Matching Matrix Elements and Parton Showers with HERWIG and PYTHIA
Mrenna, S; Mrenna, Stephen; Richardson, Peter
2004-01-01
We report on our exploration of matching matrix element calculations with the parton-shower models contained in the event generators HERWIG and Pythia. We describe results for e+e- collisions and for the hadroproduction of W bosons and Drell--Yan pairs. We compare methods based on (1) a strict implementation of ideas proposed by Catani, et al., (2) a generalization based on using the internal Sudakov form factors of HERWIG and Pythia, and (3) a simpler proposal of M. Mangano. Where appropriate, we show the dependence on various choices of scales and clustering that do not affect the soft and collinear limits of the predictions, but have phenomenological implications. Finally, we comment on how to use these results to state systematic errors on the theoretical predictions.
Bellm, Johannes; Richardson, Peter; Siódmok, Andrzej; Webster, Stephen
2016-01-01
We report on the possibility of reweighting parton-shower Monte Carlo predictions for scale variations in the parton-shower algorithm. The method is based on a generalization of the Sudakov veto algorithm. We demonstrate the feasibility of this approach using example physical distributions. Implementations are available for both the parton-shower modules in the Herwig 7 event generator.
Implementing NLO DGLAP evolution in parton showers
Energy Technology Data Exchange (ETDEWEB)
Höche, Stefan; Krauss, Frank; Prestel, Stefan
2017-10-01
We present a parton shower which implements the DGLAP evolution of parton densities and fragmentation functions at next-to-leading order precision up to effects stemming from local four-momentum conservation. The Monte-Carlo simulation is based on including next-to-leading order collinear splitting functions in an existing parton shower and combining their soft enhanced contributions with the corresponding terms at leading order. Soft double counting is avoided by matching to the soft eikonal. Example results from two independent realizations of the algorithm, implemented in the two event generation frameworks Pythia and Sherpa, illustrate the improved precision of the new formalism.
Triple collinear emissions in parton showers
Energy Technology Data Exchange (ETDEWEB)
Höche, Stefan; Prestel, Stefan
2017-10-01
A framework to include triple collinear splitting functions into parton showers is presented, and the implementation of flavor-changing NLO splitting kernels is discussed as a first application. The correspondence between the Monte-Carlo integration and the analytic computation of NLO DGLAP evolution kernels is made explicit for both timelike and spacelike parton evolution. Numerical simulation results are obtained with two independent implementations of the new algorithm, using the two independent event generation frameworks Pythia and Sherpa.
International Nuclear Information System (INIS)
Nagy, Zoltan; Soper, Davison E.
2017-05-01
We consider idealized parton shower event generators that treat parton spin and color exactly, leaving aside the choice of practical approximations for spin and color. We investigate how the structure of such a parton shower generator is related to the structure of QCD. We argue that a parton shower with splitting functions proportional to αs can be viewed not just as a model, but as the lowest order approximation to a shower that is defined at any perturbative order. To support this argument, we present a formulation for a parton shower at order α k s for any k. Since some of the input functions needed are specified by their properties but not calculated, this formulation does not provide a useful recipe for an order α k s parton shower algorithm. However, in this formulation we see how the operators that generate the shower are related to operators that specify the infrared singularities of QCD.
An analytic parton shower. Algorithms, implementation and validation
Energy Technology Data Exchange (ETDEWEB)
Schmidt, Sebastian
2012-06-15
The realistic simulation of particle collisions is an indispensable tool to interpret the data measured at high-energy colliders, for example the now running Large Hadron Collider at CERN. These collisions at these colliders are usually simulated in the form of exclusive events. This thesis focuses on the perturbative QCD part involved in the simulation of these events, particularly parton showers and the consistent combination of parton showers and matrix elements. We present an existing parton shower algorithm for emissions off final state partons along with some major improvements. Moreover, we present a new parton shower algorithm for emissions off incoming partons. The aim of these particular algorithms, called analytic parton shower algorithms, is to be able to calculate the probabilities for branchings and for whole events after the event has been generated. This allows a reweighting procedure to be applied after the events have been simulated. We show a detailed description of the algorithms, their implementation and the interfaces to the event generator WHIZARD. Moreover we discuss the implementation of a MLM-type matching procedure and an interface to the shower and hadronization routines from PYTHIA. Finally, we compare several predictions by our implementation to experimental measurements at LEP, Tevatron and LHC, as well as to predictions obtained using PYTHIA. (orig.)
An analytic parton shower. Algorithms, implementation and validation
International Nuclear Information System (INIS)
Schmidt, Sebastian
2012-06-01
The realistic simulation of particle collisions is an indispensable tool to interpret the data measured at high-energy colliders, for example the now running Large Hadron Collider at CERN. These collisions at these colliders are usually simulated in the form of exclusive events. This thesis focuses on the perturbative QCD part involved in the simulation of these events, particularly parton showers and the consistent combination of parton showers and matrix elements. We present an existing parton shower algorithm for emissions off final state partons along with some major improvements. Moreover, we present a new parton shower algorithm for emissions off incoming partons. The aim of these particular algorithms, called analytic parton shower algorithms, is to be able to calculate the probabilities for branchings and for whole events after the event has been generated. This allows a reweighting procedure to be applied after the events have been simulated. We show a detailed description of the algorithms, their implementation and the interfaces to the event generator WHIZARD. Moreover we discuss the implementation of a MLM-type matching procedure and an interface to the shower and hadronization routines from PYTHIA. Finally, we compare several predictions by our implementation to experimental measurements at LEP, Tevatron and LHC, as well as to predictions obtained using PYTHIA. (orig.)
Ordering variable for parton showers
Energy Technology Data Exchange (ETDEWEB)
Nagy, Zoltan [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Soper, Davison E. [Oregon Univ., Eugene, OR (United States). Inst. of Theoretical Science
2014-01-15
The parton splittings in a parton shower are ordered according to an ordering variable, for example the transverse momentum of the daughter partons relative to the direction of the mother, the virtuality of the splitting, or the angle between the daughter partons. We analyze the choice of the ordering variable and conclude that one particular choice has the advantage of factoring softer splittings from harder splittings graph by graph in a physical gauge.
Ordering variable for parton showers
Energy Technology Data Exchange (ETDEWEB)
Nagy, Zoltán [DESY,Notkestrasse 85, 22607 Hamburg (Germany); Soper, Davison E. [Institute of Theoretical Science, University of Oregon,Eugene, OR 97403-5203 (United States)
2014-06-30
The parton splittings in a parton shower are ordered according to an ordering variable, for example the transverse momentum of the daughter partons relative to the direction of the mother, the virtuality of the splitting, or the angle between the daughter partons. We analyze the choice of the ordering variable and conclude that one particular choice has the advantage of factoring softer splittings from harder splittings graph by graph in a physical gauge.
Ordering variable for parton showers
International Nuclear Information System (INIS)
Nagy, Zoltan; Soper, Davison E.
2014-01-01
The parton splittings in a parton shower are ordered according to an ordering variable, for example the transverse momentum of the daughter partons relative to the direction of the mother, the virtuality of the splitting, or the angle between the daughter partons. We analyze the choice of the ordering variable and conclude that one particular choice has the advantage of factoring softer splittings from harder splittings graph by graph in a physical gauge.
Energy Technology Data Exchange (ETDEWEB)
Nagy, Zoltan [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Soper, Davison E. [Oregon Univ., Eugene, OR (United States). Inst. of Theoretical Science
2017-05-15
We consider idealized parton shower event generators that treat parton spin and color exactly, leaving aside the choice of practical approximations for spin and color. We investigate how the structure of such a parton shower generator is related to the structure of QCD. We argue that a parton shower with splitting functions proportional to αs can be viewed not just as a model, but as the lowest order approximation to a shower that is defined at any perturbative order. To support this argument, we present a formulation for a parton shower at order α{sup k}{sub s} for any k. Since some of the input functions needed are specified by their properties but not calculated, this formulation does not provide a useful recipe for an order α{sup k}{sub s} parton shower algorithm. However, in this formulation we see how the operators that generate the shower are related to operators that specify the infrared singularities of QCD.
Calculations with off-shell matrix elements, TMD parton densities and TMD parton showers
Energy Technology Data Exchange (ETDEWEB)
Bury, Marcin; Hameren, Andreas van; Kutak, Krzysztof; Sapeta, Sebastian [Polish Academy of Sciences, Institute of Nuclear Physics, Cracow (Poland); Jung, Hannes [Polish Academy of Sciences, Institute of Nuclear Physics, Cracow (Poland); DESY, Hamburg (Germany); Serino, Mirko [Polish Academy of Sciences, Institute of Nuclear Physics, Cracow (Poland); Ben Gurion University of the Negev, Department of Physics, Beersheba (Israel)
2018-02-15
A new calculation using off-shell matrix elements with TMD parton densities supplemented with a newly developed initial state TMD parton shower is described. The calculation is based on the KaTie package for an automated calculation of the partonic process in high-energy factorization, making use of TMD parton densities implemented in TMDlib. The partonic events are stored in an LHE file, similar to the conventional LHE files, but now containing the transverse momenta of the initial partons. The LHE files are read in by the Cascade package for the full TMD parton shower, final state shower and hadronization from Pythia where events in HEPMC format are produced. We have determined a full set of TMD parton densities and developed an initial state TMD parton shower, including all flavors following the TMD distribution. As an example of application we have calculated the azimuthal de-correlation of high p{sub t} dijets as measured at the LHC and found very good agreement with the measurement when including initial state TMD parton showers together with conventional final state parton showers and hadronization. (orig.)
Clan properties in parton showers
International Nuclear Information System (INIS)
Ugoccioni, R.; Giovannini, A.; Lupia, S.
1994-01-01
By considering clans as genuine elementary sub-processes, i.e., intermediate parton sources in the Simplified Parton Shower model, a generalized version of this model is defined. It predicts analytically clan properties at parton level in agreement with the general trends observed experimentally at hadronic level and in Monte Carlo simulations both at partonic and hadronic level. In particular the model shows a linear rising in rapidity of the average number of clans at fixed energy of the initial parton and its subsequent bending for rapidity intervals at the border of phase space, and approximate energy independence of the average number of clans in fixed rapidity intervals. The energy independence becomes stricter by properly normalizing the average number of clans (orig.)
Clan properties in parton showers
Energy Technology Data Exchange (ETDEWEB)
Ugoccioni, R. (Dipt. di Fisica Teorica, Univ. di Torino (Italy) INFN (Italy)); Giovannini, A. (Dipt. di Fisica Teorica, Univ. di Torino (Italy) INFN (Italy)); Lupia, S. (Dipt. di Fisica Teorica, Univ. di Torino (Italy) INFN (Italy))
1994-11-01
By considering clans as genuine elementary sub-processes, i.e., intermediate parton sources in the Simplified Parton Shower model, a generalized version of this model is defined. It predicts analytically clan properties at parton level in agreement with the general trends observed experimentally at hadronic level and in Monte Carlo simulations both at partonic and hadronic level. In particular the model shows a linear rising in rapidity of the average number of clans at fixed energy of the initial parton and its subsequent bending for rapidity intervals at the border of phase space, and approximate energy independence of the average number of clans in fixed rapidity intervals. The energy independence becomes stricter by properly normalizing the average number of clans (orig.)
Parton distribution functions in the context of parton showers
International Nuclear Information System (INIS)
Nagy, Zoltán; Soper, Davison E.
2014-01-01
When the initial state evolution of a parton shower is organized according to the standard “backward evolution” prescription, ratios of parton distribution functions appear in the splitting probabilities. The shower thus organized evolves from a hard scale to a soft cutoff scale. At the end of the shower, one expects that only the parton distributions at the soft scale should affect the results. The other effects of the parton distributions should have cancelled. This means that the kernels for parton evolution should be related to the shower splitting functions. If the initial state partons can have non-zero masses, this requires that the evolution kernels cannot be the usual (MS)-bar kernels. We work out what the parton evolution kernels should be to match the shower evolution contained in the parton shower event generator DEDUCTOR, in which the b and c quarks have non-zero masses.
Parton showers with quantum interference
Nagy, Zoltan
2007-01-01
We specify recursive equations that could be used to generate a lowest order parton shower for hard scattering in hadron-hadron collisions. The formalism is based on the factorization soft and collinear interactions from relatively harder interactions in QCD amplitudes. It incorporates quantum interference between different amplitudes in those cases in which the interference diagrams have leading soft or collinear singularities. It incorporates the color and spin information carried by partons emerging from a hard interaction. One motivation for this work is to have a method that can naturally cooperate with next-to-leading order calculations.
Parton showers with quantum interference
International Nuclear Information System (INIS)
Nagy, Zoltan; Soper, Davison E.
2007-01-01
We specify recursive equations that could be used to generate a lowest order parton shower for hard scattering in hadron-hadron collisions. The formalism is based on the factorization soft and collinear interactions from relatively harder interactions in QCD amplitudes. It incorporates quantum interference between different amplitudes in those cases in which the interference diagrams have leading soft or collinear singularities. It incorporates the color and spin information carried by partons emerging from a hard interaction. One motivation for this work is to have a method that can naturally cooperate with next-to-leading order calculations
An analytic initial-state parton shower
Energy Technology Data Exchange (ETDEWEB)
Kilian, W. [Siegen Univ. (Germany). Dept. Physik; Reuter, J.; Schmidt, S.; Wiesler, D. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)
2011-12-15
We present a new algorithm for an analytic parton shower. While the algorithm for the final-state shower has been known in the literature, the construction of an initial-state shower along these lines is new. The aim is to have a parton shower algorithm for which the full analytic form of the probability distribution for all branchings is known. For these parton shower algorithms it is therefore possible to calculate the probability for a given event to be generated, providing the potential to reweight the event after the simulation. We develop the algorithm for this shower including scale choices and angular ordering. Merging to matrix elements is used to describe high-energy tails of distributions correctly. Finally, we compare our results with those of other parton showers and with experimental data from LEP, Tevatron and LHC. (orig.)
An analytic initial-state parton shower
International Nuclear Information System (INIS)
Kilian, W.
2011-12-01
We present a new algorithm for an analytic parton shower. While the algorithm for the final-state shower has been known in the literature, the construction of an initial-state shower along these lines is new. The aim is to have a parton shower algorithm for which the full analytic form of the probability distribution for all branchings is known. For these parton shower algorithms it is therefore possible to calculate the probability for a given event to be generated, providing the potential to reweight the event after the simulation. We develop the algorithm for this shower including scale choices and angular ordering. Merging to matrix elements is used to describe high-energy tails of distributions correctly. Finally, we compare our results with those of other parton showers and with experimental data from LEP, Tevatron and LHC. (orig.)
Summing threshold logs in a parton shower
International Nuclear Information System (INIS)
Nagy, Zoltan; Soper, Davison E.
2016-05-01
When parton distributions are falling steeply as the momentum fractions of the partons increases, there are effects that occur at each order in α s that combine to affect hard scattering cross sections and need to be summed. We show how to accomplish this in a leading approximation in the context of a parton shower Monte Carlo event generator.
Summing threshold logs in a parton shower
Energy Technology Data Exchange (ETDEWEB)
Nagy, Zoltán [DESY,Notkestrasse 85, 22607 Hamburg (Germany); Soper, Davison E. [Institute of Theoretical Science, University of Oregon,Eugene, OR 97403-5203 (United States)
2016-10-05
When parton distributions are falling steeply as the momentum fractions of the partons increases, there are effects that occur at each order in α{sub s} that combine to affect hard scattering cross sections and need to be summed. We show how to accomplish this in a leading approximation in the context of a parton shower Monte Carlo event generator.
A parton shower based on factorization of the quantum density matrix
International Nuclear Information System (INIS)
Nagy, Zoltan; Soper, Davison E.
2014-01-01
We present rst results from a new parton shower event generator, DEDUCTOR. Anticipating a need for an improved treatment of parton color and spin, the structure of the generator is based on the quantum density matrix in color and spin space. So far, DEDUCTOR implements only a standard spin-averaged treatment of spin in parton splittings. Although DEDUCTOR implements an improved treatment of color, in this paper we present results in the standard leading color approximation so that we can compare to the generator PYTHIA. The algorithms used incorporate a virtuality based shower ordering parameter and massive initial state bottom and charm quarks.
Fully NLO Parton Shower in QCD
International Nuclear Information System (INIS)
Skrzypek, M.; Jadach, S.; Slawinska, M.; Gituliar, O.; Kusina, A.; Placzek, W.
2011-01-01
The project of constructing a complete NLO-level Parton Shower Monte Carlo for the QCD processes developed in IFJ PAN in Krakow is reviewed. Four issues are discussed: (1) the extension of the standard inclusive collinear factorization into a new, fully exclusive scheme; (2) reconstruction of the LO Parton Shower in the new scheme; (3) inclusion of the exclusive NLO corrections into the hard process and (4) inclusion of the exclusive NLO corrections into the evolution (ladder) part. (authors)
A Parton Shower for High Energy Jets
DEFF Research Database (Denmark)
Andersen, Jeppe Rosenkrantz; Lonnblad, Leif; M. Smillie, Jennifer
2011-01-01
it is important that the corresponding divergences in the parton shower are subtracted, keeping only the collinear parts. We present a novel, shower-independent method for achieving this, enabling us to generate fully exclusive and hadronized events with multiple hard jets, in hadronic collisions. We discuss...
A Parton Shower for High Energy Jets
Andersen, Jeppe R; Smillie, Jennifer M
2011-01-01
We present a method to match the multi-parton states generated by the High Energy Jets Monte Carlo with parton showers generated by the Ariadne program using the colour dipole model. The High Energy Jets program already includes a full resummation of soft divergences. Hence, in the matching it is important that the corresponding divergences in the parton shower are subtracted, keeping only the collinear parts. We present a novel, shower-independent method for achieving this, enabling us to generate fully exclusive and hadronized events with multiple hard jets, in hadronic collisions. We discuss in detail the arising description of the soft, collinear and hard regions by examples in pure QCD jet-production.
Measurement of parton shower observables with OPAL
Directory of Open Access Journals (Sweden)
Fischer N.
2016-01-01
Full Text Available A study of QCD coherence is presented based on a sample of about 397,000 e+e- hadronic annihilation events collected at √s = 91 GeV with the OPAL detector at LEP. The study is based on four recently proposed observables that are sensitive to coherence effects in the perturbative regime. The measurement of these observables is presented, along with a comparison with the predictions of different parton shower models. The models include both conventional parton shower models and dipole antenna models. Different ordering variables are used to investigate their influence on the predictions.
Jet Hadronization via Recombination of Parton Showers in Vacuum and in Medium
Energy Technology Data Exchange (ETDEWEB)
Fries, Rainer J.; Han, Kyongchol; Ko, Che Ming
2016-12-15
We introduce a hadronization algorithm for jet parton showers based on a hybrid approach involving recombination of quarks and fragmentation of strings. The algorithm can be applied to parton showers from a shower Monte Carlo generator at the end of their perturbative evolution. The algorithm forces gluon decays and then evaluates the recombination probabilities for quark-antiquark pairs into mesons and (anti)quark triplets into (anti)baryons. We employ a Wigner phase space formulation based on the assumption of harmonic oscillator wave functions for stable hadrons and resonances. Partons too isolated in phase space to find recombination partners are connected by QCD strings to other quarks. Fragmentation of those remnant strings and the decay of all hadron resonances complete the hadronization process. We find that our model applied to parton showers from the PYTHIA Monte Carlo event generator leads to results very similar to pure Lund string fragmentation. We suggest that our algorithm can be readily generalized to jets embedded in quark-gluon plasma by adding sampled thermal partons from the phase transition hypersurface. The recombination of thermal partons and shower partons leads to an enhancement of pions and protons at intermediate momentum at both RHIC and LHC.
Systematic improvement of QCD parton showers
Winter, Jan; Hoeth, Hendrik; Krauss, Frank; Schonherr, Marek; Schumann, Steffen; Siegert, Frank; Zapp, Korinna
2012-01-01
In this contribution, we will give a brief overview of the progress that has been achieved in the field of combining matrix elements and parton showers. We exemplify this by focusing on the case of electron--positron collisions and by reporting on recent developments as accomplished within the Sherpa event generation framework.
Further ATLAS tunes of PYTHIA6 and Pythia 8
The ATLAS collaboration
2011-01-01
We present the latest developments of the ATLAS MC generator tuning project for the Pythia family of event generators, including the C++ Pythia 8 code. The PYTHIA 6 tunes presented here complete the ``AUET2B'' set by addition of parton shower and multi-parton interaction model tunings with three next-to-leading order (NLO) PDFs in addition to the leading-order and MC-adapted PDFs previously presented. This note also presents systematic variation ``eigentunes'' for the parton shower configurations in the AMBT2B/AUET2B tune series. The Pythia 8 MPI tunes in this note have been constructed for six different PDFs, making use of a new $x$-dependent hadronic matter distribution model. MPI eigentunes are constructed for the PDFs intended for use in ATLAS bulk MC production.
Hadronic top-quark pair-production with one jet and parton showering
Energy Technology Data Exchange (ETDEWEB)
Alioli, Simone; Moch, Sven-Olaf [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany); Uwer, Peter [Humboldt-Universitaet, Berlin (Germany). Inst. fuer Physik
2011-10-15
We present a calculation of heavy-flavor production in hadronic collisions in association with one jet matched to parton shower Monte Carlo programs at next-to-leading order in perturbative QCD. Top-quark decays are included and spin correlations in the decay products are taken into account. The calculation builds on existing results for the radiative corrections to heavy-quark plus one jet production and uses the POWHEG BOX for the interface to the parton shower programs PYTHIA or HERWIG. A broad phenomenological study for the Large Hadron Collider and the Tevatron is presented. In particular we study - as one important sample application - the impact of the parton shower on the top-quark charge asymmetry. (orig.)
Parton shower evolution with subleading color
International Nuclear Information System (INIS)
Nagy, Zoltan; Soper, Davison E.
2012-02-01
Parton shower Monte Carlo event generators in which the shower evolves from hard splittings to soft splittings generally use the leading color approximation, which is the leading term in an expansion in powers of 1/N c 2 , where N c =3 is the number of colors. We introduce a more general approximation, the LC+ approximation, that includes some of the color suppressed contributions. There is a cost: each generated event comes with a weight. There is a benefit: at each splitting the leading soft x collinear singularity and the leading collinear singularity are treated exactly with respect to color. In addition, an LC+ shower can start from a state of the color density matrix in which the bra state color and the ket state color do not match. (orig.)
Parton shower evolution with subleading color
Energy Technology Data Exchange (ETDEWEB)
Nagy, Zoltan [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Soper, Davison E. [Oregon Univ., Eugene, OR (United States). Inst. of Theoretical Science
2012-02-15
Parton shower Monte Carlo event generators in which the shower evolves from hard splittings to soft splittings generally use the leading color approximation, which is the leading term in an expansion in powers of 1/N{sub c}{sup 2}, where N{sub c}=3 is the number of colors. We introduce a more general approximation, the LC+ approximation, that includes some of the color suppressed contributions. There is a cost: each generated event comes with a weight. There is a benefit: at each splitting the leading soft x collinear singularity and the leading collinear singularity are treated exactly with respect to color. In addition, an LC+ shower can start from a state of the color density matrix in which the bra state color and the ket state color do not match. (orig.)
Parton Shower Uncertainties with Herwig 7: Benchmarks at Leading Order
Bellm, Johannes; Plätzer, Simon; Schichtel, Peter; Siódmok, Andrzej
2016-01-01
We perform a detailed study of the sources of perturbative uncertainty in parton shower predictions within the Herwig 7 event generator. We benchmark two rather different parton shower algorithms, based on angular-ordered and dipole-type evolution, against each other. We deliberately choose leading order plus parton shower as the benchmark setting to identify a controllable set of uncertainties. This will enable us to reliably assess improvements by higher-order contributions in a follow-up work.
Initial-state parton shower kinematics for NLO event generators
International Nuclear Information System (INIS)
Odaka, Shigeru; Kurihara, Yoshimasa
2007-01-01
We are developing a consistent method to combine tree-level event generators for hadron collision interactions with those including one additional QCD radiation from the initial-state partons, based on the limited leading-log (LLL) subtraction method, aiming at an application to NLO event generators. In this method, a boundary between non-radiative and radiative processes necessarily appears at the factorization scale (μ F ). The radiation effects are simulated using a parton shower (PS) in non-radiative processes. It is therefore crucial in our method to apply a PS which well reproduces the radiation activities evaluated from the matrix-element (ME) calculations for radiative processes. The PS activity depends on the applied kinematics model. In this paper we introduce two models for our simple initial-state leading-log PS: a model similar to the 'old' PYTHIA-PS and a p T -prefixed model motivated by ME calculations. PS simulations employing these models are tested using W-boson production at LHC as an example. Both simulations show a smooth matching to the LLL subtracted W+1 jet simulation in the p T distribution of W bosons, and the summed p T spectra are stable against a variation of μ F , despite that the p T -prefixed PS results in an apparently harder p T spectrum. (orig.)
Parton showers in a phenomenological context
International Nuclear Information System (INIS)
Bengtsson, M.
1987-08-01
Models for generating multiple parton final states, based on the Altarelli-Parisi equations, are presented. Algorithms are described for applications in e + e - physics, leptoproduction and hadron physics. The two latter cases are somewhat special since composite objects are present in the initial state. Constraints from structure function evolution are properly taken into account. The scheme in leptoproduction is made selfconsistent in the sense that parton shower evolution does not affect the measurable structure functions. The scheme developed in e + e - allows for a number of different features which are not given directly in this approach, i.e. matching onto matrix elements, coherence effects, argument in α s , implementation of kinematics etc. These options are systematically studied, using Lund string fragmentation for hadronization, and compared with experimental data. A note on α s determinations in hadron-hadron collisions is also included. (author)
QCD parton showers and NLO EW corrections to Drell-Yan
Richardson, P; Sapronov, A A; Seymour, M H; Skands, P Z
2012-01-01
We report on the implementation of an interface between the SANC generator framework for Drell-Yan hard processes, which includes next-to-leading order electroweak (NLO EW) corrections, and the Herwig++ and Pythia8 QCD parton shower Monte Carlos. A special aspect of this implementation is that the initial-state shower evolution in both shower generators has been augmented to handle the case of an incoming photon-in-a-proton, diagrams for which appear at the NLO EW level. The difference between shower algorithms leads to residual differences in the relative corrections of 2-3% in the p_T(mu) distributions at p_T(mu)>~50 GeV (where the NLO EW correction itself is of order 10%).
International Nuclear Information System (INIS)
Alioli, Simone; Bauer, Christian W.; Berggren, Calvin; Vermilion, Christopher K.; Walsh, Jonathan R.; Zuberi, Saba; Hornig, Andrew; Tackmann, Frank J.
2013-05-01
We discuss the GENEVA Monte Carlo framework, which combines higher-order resummation (NNLL) of large Sudakov logarithms with multiple next-to-leading-order (NLO) matrix-element corrections and parton showering (using PYTHIA 8) to give a complete description at the next higher perturbative accuracy in α s at both small and large jet resolution scales. Results for e + e - →jets compared to LEP data and pp→(Z/γ * →l + l - )+jets are presented.
A study of optimal parameter setting for aMC@NLO + Pythia8 matched setup
The ATLAS collaboration
2015-01-01
This note presents a study to arrive at the optimum tune of Pythia8 generator's parton shower and multiple parton interaction parameters for aMC@NLO + Pythia8 matched setup. Published distributions from ATLAS Run 1 data at 7 TeV for three different processes, inclusive jet, Z~boson and $t\\bar{t}$ production were studied. Additionally, the effect of using two different parton recoil modes in shower, global and local recoil are also investigated.
Reweighting QCD matrix-element and parton-shower calculations
Energy Technology Data Exchange (ETDEWEB)
Bothmann, Enrico; Schumann, Steffen [Universitaet Goettingen, II. Physikalisches Institut, Goettingen (Germany); Schoenherr, Marek [Universitaet Zuerich, Physik-Institut, Zuerich (Switzerland)
2016-11-15
We present the implementation and validation of the techniques used to efficiently evaluate parametric and perturbative theoretical uncertainties in matrix-element plus parton-shower simulations within the Sherpa event-generator framework. By tracing the full α{sub s} and PDF dependences, including the parton-shower component, as well as the fixed-order scale uncertainties, we compute variational event weights on-the-fly, thereby greatly reducing the computational costs to obtain theoretical-uncertainty estimates. (orig.)
Combining higher-order resummation with multiple NLO calculations and parton showers in GENEVA
Energy Technology Data Exchange (ETDEWEB)
Alioli, Simone; Bauer, Christian W.; Berggren, Calvin; Vermilion, Christopher K.; Walsh, Jonathan R.; Zuberi, Saba [California Univ., Berkeley, CA (United States). Ernest Orlando Lawrence Berkeley National Laboratory; Hornig, Andrew [Washington Univ., Seattle, WA (United States). Dept. of Physics; Tackmann, Frank J. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany). Gruppe Theorie
2012-11-15
We extend the lowest-order matching of tree-level matrix elements with parton showers to give a complete description at the next higher perturbative accuracy in {alpha}{sub s} at both small and large jet resolutions, which has not been achieved so far. This requires the combination of the higher-order resummation of large Sudakov logarithms at small values of the jet resolution variable with the full next-to-leading order (NLO) matrix-element corrections at large values. As a by-product, this combination naturally leads to a smooth connection of the NLO calculations for different jet multiplicities. In this paper, we focus on the general construction of our method and discuss its application to e{sup +}e{sup -} and pp collisions. We present first results of the implementation in the GENEVA Monte Carlo framework. We employ N-jettiness as the jet resolution variable, combining its next-to-next-to-leading logarithmic resummation with fully exclusive NLO matrix elements, and PYTHIA 8 as the backend for further parton showering and hadronization. For hadronic collisions, we take Drell-Yan production as an example to apply our construction. For e{sup +}e{sup -} {yields} jets, taking {alpha}{sub s}(m{sub Z}) = 0.1135 from fits to LEP thrust data, together with the PYTHIA 8 hadronization model, we obtain good agreement with LEP data for a variety of 2-jet observables.
Controlling inclusive cross sections in parton shower + matrix element merging
International Nuclear Information System (INIS)
Plaetzer, Simon
2012-11-01
We propose an extension of matrix element plus parton shower merging at tree level to preserve inclusive cross sections obtained from the merged and showered sample. Implementing this constraint generates approximate next-to-leading order (NLO) contributions similar to the LoopSim approach. We then show how full NLO, or in principle even higher order, corrections can be added consistently, including constraints on inclusive cross sections to account for yet missing parton shower accuracy at higher logarithmic order. We also show how NLO accuracy below the merging scale can be obtained.
Controlling inclusive cross sections in parton shower + matrix element merging
Energy Technology Data Exchange (ETDEWEB)
Plaetzer, Simon
2012-11-15
We propose an extension of matrix element plus parton shower merging at tree level to preserve inclusive cross sections obtained from the merged and showered sample. Implementing this constraint generates approximate next-to-leading order (NLO) contributions similar to the LoopSim approach. We then show how full NLO, or in principle even higher order, corrections can be added consistently, including constraints on inclusive cross sections to account for yet missing parton shower accuracy at higher logarithmic order. We also show how NLO accuracy below the merging scale can be obtained.
Systematic improvement of parton showers with effective theory
International Nuclear Information System (INIS)
Baumgart, Matthew; Marcantonini, Claudio; Stewart, Iain W.
2011-01-01
We carry out a systematic classification and computation of next-to-leading order kinematic power corrections to the fully differential cross section in the parton shower. To do this we devise a map between ingredients in a parton shower and operators in a traditional effective field theory framework using a chain of soft-collinear effective theories. Our approach overcomes several difficulties including avoiding double counting and distinguishing approximations that are coordinate choices from true power corrections. Branching corrections can be classified as hard-scattering, that occur near the top of the shower, and jet-structure, that can occur at any point inside it. Hard-scattering corrections include matrix elements with additional hard partons, as well as power suppressed contributions to the branching for the leading jet. Jet-structure corrections require simultaneous consideration of potential 1→2 and 1→3 branchings. The interference structure induced by collinear terms with subleading powers remains localized in the shower.
A case study of quark-gluon discrimination at NNLL{sup '} in comparison to parton showers
Energy Technology Data Exchange (ETDEWEB)
Mo, Jonathan; Waalewijn, Wouter J. [University of Amsterdam, Institute for Theoretical Physics Amsterdam and Delta Institute for Theoretical Physics, Amsterdam (Netherlands); Nikhef, Theory Group, Amsterdam (Netherlands); Tackmann, Frank J. [Theory Group, Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)
2017-11-15
Predictions for our ability to distinguish quark and gluon jets vary by more than a factor of two between different parton showers. We study this problem using analytic resummed predictions for the thrust event shape up to NNLL{sup '} using e{sup +}e{sup -} → Z → q anti q and e{sup +}e{sup -} → H → gg as proxies for quark and gluon jets. We account for hadronization effects through a nonperturbative shape function, and include an estimate of both perturbative and hadronization uncertainties. In contrast to previous studies, we find reasonable agreement between our results and predictions from both Pythia and Herwig parton showers. We find that this is due to a noticeable improvement in the description of gluon jets in the newest Herwig 7.1 compared to previous versions. (orig.)
A case study of quark-gluon discrimination at NNLL{sup '} in comparison to parton showers
Energy Technology Data Exchange (ETDEWEB)
Mo, Jonathan; Waalewijn, Wouter [Institute for Theoretical Physics, Amsterdam (Netherlands); Amsterdam Univ. (Netherlands). Delta Inst. for Theoretical Physics; Nikhef, Amsterdam (Netherlands). Theory Group; Tackmann, Frank J. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany). Theory Group
2017-08-15
Predictions for our ability to distinguish quark and gluon jets vary by more than a factor of two between different parton showers. We study this problem using analytic resummed predictions for the thrust event shape up to NNLL{sup '} using e{sup +}e{sup -}→Z→q anti q and e{sup +}e{sup -}→H→gg as proxies for quark and gluon jets. We account for hadronization effects through a nonperturbative shape function, and include an estimate of both perturbative and hadronization uncertainties. In contrast to previous studies, we find reasonable agreement between our results and predictions from both PYTHIA and HERWIG parton showers. We find that this is due to a noticeable improvement in the description of gluon jets in the newest Herwig 7.1 compared to previous versions.
The ATLAS collaboration
2014-01-01
We present tunes of the Pythia8 Monte~Carlo event generator's parton shower and multiple parton interaction parameters to a range of data observables from ATLAS Run 1. Four new tunes have been constructed, corresponding to the four leading-order parton density functions, CTEQ6L1, MSTW2008LO, NNPDF23LO, and HERAPDF15LO, each simultaneously tuning ten generator parameters. A set of systematic variations is provided for the NNPDF tune, based on the eigentune method. These tunes improve the modeling of observables that can be described by leading-order + parton shower simulation, and are primarily intended for use in situations where next-to-leading-order and/or multileg parton-showered simulations are unavailable or impractical.
Effects of subleading color in a parton shower
International Nuclear Information System (INIS)
Nagy, Zoltan; Soper, Davison E.
2014-12-01
Parton shower Monte Carlo event generators in which the shower evolves from hard splittings to soft splittings generally use the leading color (LC) approximation, which is the leading term in an expansion in powers of 1/N c 2 , where N c =3 is the number of colors. In the parton shower event generator DEDUCTOR, we have introduced a more general approximation, the LC+ approximation, that includes some of the color suppressed contributions. In this paper, we explore the differences in results between the LC approximation and the LC+ approximation. Numerical comparisons suggest that, for simple observables, the LC approximation is quite accurate. We also find evidence that for gap-between-jets cross sections neither the LC approximation nor the LC+ approximation is adequate.
Tuning of the PYTHIA 6.4 Multiple Parton Interaction model to Minimum Bias and Underlying Event data
Firdoua, Nameequa
QCD has been quite successful in describing hadronic interactions at large transfer momenta, also known as hard interactions. However high energy pp and p p collisions are dominated by soft partonic collisions. Di erent phenomenological models are implemented in several Monte Carlo (MC) event generators such as PYTHIA, PHOJET and HERWIG etc., which attempt to simulate these interactions. These MC event generators have free parameters which need to be tuned to improve the agreement with the data. In this thesis the MC event generator PYTHIA6.424 is considered and the optimization of its model parameters have been presented. This work mainly focuses on tuning of multiple parton interaction parameters to Minimum Bias and Underlying event published data from ATLAS at 0.9 and 7TeV and from CDF II at 1.96 TeV. The method employed to tune the parameters is based on a linear and iterative approach and allows the simultaneous variation of many parameters. Six parameters are tuned, which are found to be...
Matching fully differential NNLO calculations and parton showers
Energy Technology Data Exchange (ETDEWEB)
Alioli, Simone; Bauer, Christian W.; Berggren, Calvin; Walsh, Jonathan R.; Zuberi, Saba [California Univ., Berkeley, CA (United States). Ernest Orlando Lawrence Berkeley National Laboratory; Tackmann, Frank J. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)
2013-11-15
We present a general method to match fully differential next-to-next-to-leading (NNLO) calculations to parton shower programs. We discuss in detail the perturbative accuracy criteria a complete NNLO+PS matching has to satisfy. Our method is based on consistently improving a given NNLO calculation with the leading-logarithmic (LL) resummation in a chosen jet resolution variable. The resulting NNLO+LL calculation is cast in the form of an event generator for physical events that can be directly interfaced with a parton shower routine, and we give an explicit construction of the input ''Monte Carlo cross sections'' satisfying all required criteria. We also show how other proposed approaches naturally arise as special cases in our method.
Combining states without scale hierarchies with ordered parton showers
Energy Technology Data Exchange (ETDEWEB)
Fischer, Nadine [Monash University, School of Physics and Astronomy, Clayton, VIC (Australia); Prestel, Stefan [Fermi National Accelerator Laboratory, Batavia, IL (United States)
2017-09-15
We present a parameter-free scheme to combine fixed-order multi-jet results with parton-shower evolution. The scheme produces jet cross sections with leading-order accuracy in the complete phase space of multiple emissions, resumming large logarithms when appropriate, while not arbitrarily enforcing ordering on momentum configurations beyond the reach of the parton-shower evolution equation. This requires the development of a matrix-element correction scheme for complex phase-spaces including ordering conditions as well as a systematic scale-setting procedure for unordered phase-space points. The resulting algorithm does not require a merging-scale parameter. We implement the new method in the Vincia framework and compare to LHC data. (orig.)
Matching fully differential NNLO calculations and parton showers
International Nuclear Information System (INIS)
Alioli, Simone; Bauer, Christian W.; Berggren, Calvin; Walsh, Jonathan R.; Zuberi, Saba
2013-11-01
We present a general method to match fully differential next-to-next-to-leading (NNLO) calculations to parton shower programs. We discuss in detail the perturbative accuracy criteria a complete NNLO+PS matching has to satisfy. Our method is based on consistently improving a given NNLO calculation with the leading-logarithmic (LL) resummation in a chosen jet resolution variable. The resulting NNLO+LL calculation is cast in the form of an event generator for physical events that can be directly interfaced with a parton shower routine, and we give an explicit construction of the input ''Monte Carlo cross sections'' satisfying all required criteria. We also show how other proposed approaches naturally arise as special cases in our method.
The average number of partons per clan in rapidity intervals in parton showers
Energy Technology Data Exchange (ETDEWEB)
Giovannini, A. [Turin Univ. (Italy). Ist. di Fisica Teorica; Lupia, S. [Max-Planck-Institut fuer Physik, Muenchen (Germany). Werner-Heisenberg-Institut; Ugoccioni, R. [Lund Univ. (Sweden). Dept. of Theoretical Physics
1996-04-01
The dependence of the average number of partons per clan on virtuality and rapidity variables is analytically predicted in the framework of the Generalized Simplified Parton Shower model, based on the idea that clans are genuine elementary subprocesses. The obtained results are found to be qualitatively consistent with experimental trends. This study extends previous results on the behavior of the average number of clans in virtuality and rapidity and shows how important physical quantities can be calculated analytically in a model based on essentials of QCD allowing local violations of the energy-momentum conservation law, still requiring its global validity. (orig.)
The average number of partons per clan in rapidity intervals in parton showers
International Nuclear Information System (INIS)
Giovannini, A.; Lupia, S.; Ugoccioni, R.
1996-01-01
The dependence of the average number of partons per clan on virtuality and rapidity variables is analytically predicted in the framework of the Generalized Simplified Parton Shower model, based on the idea that clans are genuine elementary subprocesses. The obtained results are found to be qualitatively consistent with experimental trends. This study extends previous results on the behavior of the average number of clans in virtuality and rapidity and shows how important physical quantities can be calculated analytically in a model based on essentials of QCD allowing local violations of the energy-momentum conservation law, still requiring its global validity. (orig.)
Parton-shower uncertainties with Herwig 7: benchmarks at leading order
Energy Technology Data Exchange (ETDEWEB)
Bellm, Johannes; Schichtel, Peter [Durham University, Department of Physics, IPPP, Durham (United Kingdom); Nail, Graeme [University of Manchester, Particle Physics Group, School of Physics and Astronomy, Manchester (United Kingdom); Karlsruhe Institute of Technology, Institute for Theoretical Physics, Karlsruhe (Germany); Plaetzer, Simon [Durham University, Department of Physics, IPPP, Durham (United Kingdom); University of Manchester, Particle Physics Group, School of Physics and Astronomy, Manchester (United Kingdom); Siodmok, Andrzej [CERN, TH Department, Geneva (Switzerland); Polish Academy of Sciences, The Henryk Niewodniczanski Institute of Nuclear Physics in Cracow, Krakow (Poland)
2016-12-15
We perform a detailed study of the sources of perturbative uncertainty in parton-shower predictions within the Herwig 7 event generator. We benchmark two rather different parton-shower algorithms, based on angular-ordered and dipole-type evolution, against each other. We deliberately choose leading order plus parton shower as the benchmark setting to identify a controllable set of uncertainties. This will enable us to reliably assess improvements by higher-order contributions in a follow-up work. (orig.)
Top-pair production and decay at NLO matched with parton showers
International Nuclear Information System (INIS)
Campbell, John M.; Ellis, R. Keith; Nason, Paolo; Re, Emanuele
2015-01-01
We present a next-to-leading order (NLO) calculation of tt¯ production in hadronic collisions interfaced to shower generators according to the POWHEG method. We start from an NLO result from previous work, obtained in the zero width limit, where radiative corrections to both production and decays are included. The POWHEG interface required an extension of the POWHEG BOX framework, in order to deal with radiation from the decay of resonances. This extension is fully general (i.e. it can be applied in principle to any process considered in the zero width limit), and is here applied for the first time. In order to perform a realistic simulation, we introduce finite width effects using different approximations, that we validated by comparing with published exact NLO results. We have interfaced our POWHEG code to the PYTHIA8 shower Monte Carlo generator. At this stage, we dealt with novel issues related to the treatment of resonances, especially with regard to the initial scale for the shower that needs to be set appropriately. This procedure affects, for example, the fragmentation function of the b quark, that we have studied with particular attention. We believe that the tool presented here improves over previous generators for all aspects that have to do with top decays, and especially for the study of issues related to top mass measurements that involve B hadrons or b jets. As a result, the work presented here also constitutes a first step towards a fully consistent matching of NLO calculations involving intermediate resonances decaying into coloured particles, with parton showers
Higgs boson production A comparison of parton showers and resummation
Balázs, C; Puljak, I
2001-01-01
The search for the Higgs boson(s) is one of the major priorities at the upgraded Fermilab Tevatron and at the CERN Large Hadron Collider (LHC). Monte Carlo (MC) event generators are heavily utilized to extract and interpret the Higgs signal, which depends on the details of the soft-gluon emission from the initial state partons in hadronic collisions. Thus, it is crucial to establish the reliability of the MC event generators used by the experimentalists. In this paper, the MC based parton shower formalism is compared to that of an analytic resummation calculation. Theoretical input, predictions and, where they exist, data for the transverse momentum distribution of Higgs bosons, Z/sup 0/ bosons, and photon pairs are compared for the Tevatron and the LHC. This comparison is useful in understanding the strengths and the weaknesses of the different theoretical approaches, and in testing their reliability. (36 refs).
Energy Technology Data Exchange (ETDEWEB)
Sjoestrand, Torbjoern; Christiansen, Jesper R.; Corke, Richard; Rasmussen, Christine O. [Lund Univ. (Sweden). Dept. of Astronomy and Theoretical Physics; Ask, Stefan [Cambridge Univ. (United Kingdom). Dept. of Physics; Desai, Nishita [Heidelberg Univ. (Germany). Inst. fuer Theoretische Physik; Ilten, Philip [Massachusetts Institute of Technology, Cambridge (United States); Mrenna, Stephen [Fermi National Accelerator Laboratory, Batavia, IL (United States); Prestel, Stefan [DESY Hamburg (Germany). Theory Group; SLAC National Accelerator Laboratory, Menlo Park, CA (United States); Skands, Peter Z. [CERN/PH, Geneva (Switzerland); Monash Univ., Melbourne (Australia). School of Physics
2014-10-15
The Pythia program is a standard tool for the generation of events in high-energy collisions, comprising a coherent set of physics models for the evolution from a few-body hard process to a complex multiparticle final state. It contains a library of hard processes, models for initial- and final-state parton showers, matching and merging methods between hard processes and parton showers, multiparton interactions, beam remnants, string fragmentation and particle decays. It also has a set of utilities and several interfaces to external programs. Pythia 8.2 is the second main release after the complete rewrite from Fortran to C++, and now has reached such a maturity that it offers a complete replacement for most applications, notably for LHC physics studies. The many new features should allow an improved description of data.
Sjöstrand, Torbjörn; Christiansen, Jesper R.; Corke, Richard; Desai, Nishita; Ilten, Philip; Mrenna, Stephen; Prestel, Stefan; Rasmussen, Christine O.; Skands, Peter Z.
2015-02-11
The PYTHIA program is a standard tool for the generation of events in high-energy collisions, comprising a coherent set of physics models for the evolution from a few-body hard process to a complex multiparticle final state. It contains a library of hard processes, models for initial- and final-state parton showers, matching and merging methods between hard processes and parton showers, multiparton interactions, beam remnants, string fragmentation and particle decays. It also has a set of utilities and several interfaces to external programs. PYTHIA 8.2 is the second main release after the complete rewrite from Fortran to C++, and now has reached such a maturity that it offers a complete replacement for most applications, notably for LHC physics studies. The many new features should allow an improved description of data.
International Nuclear Information System (INIS)
Sjoestrand, Torbjoern; Christiansen, Jesper R.; Corke, Richard; Rasmussen, Christine O.; Mrenna, Stephen; Prestel, Stefan; Skands, Peter Z.; Monash Univ., Melbourne
2014-10-01
The Pythia program is a standard tool for the generation of events in high-energy collisions, comprising a coherent set of physics models for the evolution from a few-body hard process to a complex multiparticle final state. It contains a library of hard processes, models for initial- and final-state parton showers, matching and merging methods between hard processes and parton showers, multiparton interactions, beam remnants, string fragmentation and particle decays. It also has a set of utilities and several interfaces to external programs. Pythia 8.2 is the second main release after the complete rewrite from Fortran to C++, and now has reached such a maturity that it offers a complete replacement for most applications, notably for LHC physics studies. The many new features should allow an improved description of data.
Parton-shower matching systematics in vector-boson-fusion WW production
Energy Technology Data Exchange (ETDEWEB)
Rauch, Michael [Karlsruhe Institute of Technology, Institute for Theoretical Physics, Karlsruhe (Germany); Plaetzer, Simon [Durham University, Institute for Particle Physics Phenomenology, Durham (United Kingdom); University of Manchester, School of Physics and Astronomy, Manchester (United Kingdom)
2017-05-15
We perform a detailed analysis of next-to-leading order plus parton-shower matching in vector-boson-fusion WW production including leptonic decays. The study is performed in the Herwig 7 framework interfaced to VBFNLO 3, using the angular-ordered and dipole-based parton-shower algorithms combined with the subtractive and multiplicative-matching algorithms. (orig.)
Parton shower and NLO-matching uncertainties in Higgs boson pair production
Jones, Stephen; Kuttimalai, Silvan
2018-02-01
We perform a detailed study of NLO parton shower matching uncertainties in Higgs boson pair production through gluon fusion at the LHC based on a generic and process independent implementation of NLO subtraction and parton shower matching schemes for loop-induced processes in the Sherpa event generator. We take into account the full top-quark mass dependence in the two-loop virtual corrections and compare the results to an effective theory approximation. In the full calculation, our findings suggest large parton shower matching uncertainties that are absent in the effective theory approximation. We observe large uncertainties even in regions of phase space where fixed-order calculations are theoretically well motivated and parton shower effects expected to be small. We compare our results to NLO matched parton shower simulations and analytic resummation results that are available in the literature.
Tuning Geneva+Pythia 8 Using Professor 2
Gellersen, Leif Erik
2016-01-01
We study the tuning of the Geneva Monte Carlo framework to LHC data. Geneva improves the predictions for Drell-Yan production by including NNLO QCD corrections and extending the resummation accuracy to NNLL$'$ for 0-jettiness and NLL for 1-jettiness. The partonic results provided by Geneva are interfaced to Pythia 8 for showering including its multiple parton interaction (MPI) model. This allows us to obtain sensible predictions for Underlying Event (UE) sensitive observables too. Retuning Geneva + Pythia 8 to LHC data with the Professor 2 package shows an improved agreement for both UE sensitive and more inclusive observables.
On the transverse momentum in Z-boson production in a virtually ordered parton shower
Energy Technology Data Exchange (ETDEWEB)
Nagy, Zoltan [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Soper, Davison E. [Oregon Univ., Eugene, OR (United States). Inst. of Theoretical Science
2009-12-15
Cross sections for physical processes that involve very different momentum scales in the same process will involve large logarithms of the ratio of the momentum scales when calculated in perturbation theory. One goal of calculations using parton showers is to sum these large logarithms. We ask whether this goal is achieved for the transverse momentum distribution of a Z-boson produced in hadron-hadron collisions when the shower is organized with higher virtuality parton splittings coming first, followed successively by lower virtuality parton splittings. We find that the virtuality ordered shower works well in reproducing the known QCD result. (orig.)
On the transverse momentum in Z-boson production in a virtually ordered parton shower
International Nuclear Information System (INIS)
Nagy, Zoltan; Soper, Davison E.
2009-12-01
Cross sections for physical processes that involve very different momentum scales in the same process will involve large logarithms of the ratio of the momentum scales when calculated in perturbation theory. One goal of calculations using parton showers is to sum these large logarithms. We ask whether this goal is achieved for the transverse momentum distribution of a Z-boson produced in hadron-hadron collisions when the shower is organized with higher virtuality parton splittings coming first, followed successively by lower virtuality parton splittings. We find that the virtuality ordered shower works well in reproducing the known QCD result. (orig.)
QED radiative correction for the single-W production using a parton shower method
International Nuclear Information System (INIS)
Kurihara, Y.; Fujimoto, J.; Ishikawa, T.; Shimizu, Y.; Kato, K.; Tobimatsu, K.; Munehisa, T.
2001-01-01
A parton shower method for the photonic radiative correction is applied to single W-boson production processes. The energy scale for the evolution of the parton shower is determined so that the correct soft-photon emission is reproduced. Photon spectra radiated from the partons are compared with those from the exact matrix elements, and show a good agreement. Possible errors due to an inappropriate energy-scale selection or due to the ambiguity of the energy-scale determination are also discussed, particularly for the measurements on triple gauge couplings. (orig.)
QCD event generators with next-to-leading order matrix-elements and parton showers
International Nuclear Information System (INIS)
Kurihara, Y.; Fujimoto, J.; Ishikawa, T.; Kato, K.; Kawabata, S.; Munehisa, T.; Tanaka, H.
2003-01-01
A new method to construct event-generators based on next-to-leading order QCD matrix-elements and leading-logarithmic parton showers is proposed. Matrix elements of loop diagram as well as those of a tree level can be generated using an automatic system. A soft/collinear singularity is treated using a leading-log subtraction method. Higher order resummation of the soft/collinear correction by the parton shower method is combined with the NLO matrix-element without any double-counting in this method. An example of the event generator for Drell-Yan process is given for demonstrating a validity of this method
A parton shower based on factorization of the quantum density matrix
Nagy, Zoltan; Soper, Davison E.
2014-01-01
We present first results from a new parton shower event generator, D eductor . Anticipating a need for an improved treatment of parton color and spin, the structure of the generator is based on the quantum density matrix in color and spin space. So far, D eductor implements only a standard spin-averaged treatment of spin in parton splittings. Although D eductor implements an improved treatment of color, in this paper we present results in the standard leading color approximation so that we ca...
Three-particle correlations in QCD parton showers
International Nuclear Information System (INIS)
Perez-Ramos, Redamy; Mathieu, Vincent; Sanchis-Lozano, Miguel-Angel
2011-01-01
Three-particle correlations in quark and gluon jets are computed for the first time in perturbative QCD. We give results in the double logarithmic approximation and the modified leading logarithmic approximation. In both resummation schemes, we use the formalism of the generating functional and solve the evolution equations analytically from the steepest descent evaluation of the one-particle distribution. We thus provide a further test of the local parton hadron duality and make predictions for the LHC.
HERWIRI1.0: MC realization of IR-improved DGLAP-CS parton showers
International Nuclear Information System (INIS)
Joseph, S.; Majhi, S.; Ward, B.F.L.; Yost, S.A.
2010-01-01
We present Monte Carlo data showing the comparison between the parton shower generated by the standard Dokshitzer-Gribov-Lipatov-Altarelli-Parisi-Callan-Symanzik (DGLAP-CS) kernels and that generated with the new IR-improved DGLAP-CS kernels recently developed by one of us. We do this in the context of HERWIG6.5 by implementing the new kernels therein to generate a new MC, HERWIRI1.0, for hadron-hadron interactions at high energies. We discuss possible phenomenological implications for precision LHC theory. We also present comparisons with FNAL data.
Matching next-to-leading order predictions to parton showers in supersymmetric QCD
Degrande, Celine; Hirschi, Valentin; Proudom, Josselin; Shao, Hua-Sheng
2016-04-10
We present a fully automated framework based on the FeynRules and MadGraph5 aMC@NLO programs that allows for accurate simulations of supersymmetric QCD processes at the LHC. Starting directly from a model Lagrangian that features squark and gluino interactions, event generation is achieved at the next-to-leading order in QCD, matching short-distance events to parton showers and including the subsequent decay of the produced supersymmetric particles. As an application, we study the impact of higher-order corrections in gluino pair-production in a simplified benchmark scenario inspired by current gluino LHC searches.
Cabouat, Baptiste; Sjöstrand, Torbjörn
2018-03-01
Parton showers have become a standard component in the description of high-energy collisions. Nowadays most final-state ones are of the dipole character, wherein a pair of partons branches into three, with energy and momentum preserved inside this subsystem. For initial-state showers a dipole picture is also possible and commonly used, but the older global-recoil strategy remains a valid alternative, wherein larger groups of partons share the energy-momentum preservation task. In this article we introduce and implement a dipole picture also for initial-state radiation in Pythia, and compare with the existing global-recoil one, and with data. For the case of Deeply Inelastic Scattering we can directly compare with matrix element expressions and show that the dipole picture gives a very good description over the whole phase space, at least for the first branching.
Heinrich, G.; Kerner, M.; Luisoni, G.; Vryonidou, E.
2017-08-21
We present the first combination of NLO QCD matrix elements for di-Higgs production, retaining the full top quark mass dependence, with a parton shower. Results are provided within both the POWHEG-BOX and MadGraph5_aMC@NLO Monte Carlo frameworks. We assess in detail the theoretical uncertainties and provide differential results. We find that, as expected, the shower effects are relatively large for observables like the transverse momentum of the Higgs boson pair, which are sensitive to extra radiation. However, these shower effects are still much smaller than the differences between the Born-improved HEFT approximation and the full NLO calculation in the tails of the distributions.
Energy Technology Data Exchange (ETDEWEB)
Sjostrand, Torbjorn; /Lund U., Dept. Theor. Phys.; Mrenna, Stephen; Skands, Peter; /Fermilab
2006-03-01
The Pythia program can be used to generate high-energy-physics ''events'', i.e. sets of outgoing particles produced in the interactions between two incoming particles. The objective is to provide as accurate as possible a representation of event properties in a wide range of reactions, within and beyond the Standard Model, with emphasis on those where strong interactions play a role, directly or indirectly, and therefore multihadronic final states are produced. The physics is then not understood well enough to give an exact description; instead the program has to be based on a combination of analytical results and various QCD-based models. This physics input is summarized here, for areas such as hard subprocesses, initial- and final-state parton showers, underlying events and beam remnants, fragmentation and decays, and much more. Furthermore, extensive information is provided on all program elements: subroutines and functions, switches and parameters, and particle and process data. This should allow the user to tailor the generation task to the topics of interest.
New approach to parton shower Monte Carlo event generators for precision QCD theory: HERWIRI1.0(31)
International Nuclear Information System (INIS)
Joseph, S.; Ward, B. F. L.; Majhi, S.; Yost, S. A.
2010-01-01
By implementing the new IR-improved Dokshitzer-Gribov-Lipatov-Altarelli-Parisi-Callan-Symanzik (DGLAP-CS) kernels recently developed by one of us in the HERWIG6.5 environment we generate a new Monte Carlo (MC), HERWIRI1.0(31), for hadron-hadron scattering at high energies. We use MC data to illustrate the comparison between the parton shower generated by the standard DGLAP-CS kernels and that generated by the new IR-improved DGLAP-CS kernels. The interface to MC-NLO, MC-NLO/HERWIRI, is illustrated. Comparisons with FNAL data and some discussion of possible implications for LHC phenomenology are also presented.
International Nuclear Information System (INIS)
Majhi, S.K.; Mukhopadhyay, A.; Ward, B.F.L.; Yost, S.A.
2013-01-01
We present the current status of the application of our approach of exact amplitude-based resummation in quantum field theory to precision QCD calculations, by realistic MC event generator methods, as needed for precision LHC physics. In this ongoing program of research, we discuss recent results as they relate to the interplay of the attendant IR-improved DGLAP-CS theory of one of us and the precision of exact NLO matrix element matched parton shower MC's in the Herwig6.5 environment in relation to recent LHC experimental observations. There continues to be reason for optimism in the attendant comparison of theory and experiment
Energy Technology Data Exchange (ETDEWEB)
Majhi, S.K., E-mail: tpskm@iacs.res.in [Indian Association for the Cultivation of Science, Kolkata (India); Mukhopadhyay, A., E-mail: aditi_mukhopadhyay@baylor.edu [Baylor University, Waco, TX (United States); Ward, B.F.L., E-mail: bfl_ward@baylor.edu [Baylor University, Waco, TX (United States); Yost, S.A., E-mail: scott.yost@citadel.edu [The Citadel, Charleston, SC (United States)
2013-02-26
We present the current status of the application of our approach of exact amplitude-based resummation in quantum field theory to precision QCD calculations, by realistic MC event generator methods, as needed for precision LHC physics. In this ongoing program of research, we discuss recent results as they relate to the interplay of the attendant IR-improved DGLAP-CS theory of one of us and the precision of exact NLO matrix element matched parton shower MC's in the Herwig6.5 environment in relation to recent LHC experimental observations. There continues to be reason for optimism in the attendant comparison of theory and experiment.
EVENT GENERATION OF STANDARD MODEL HIGGS DECAY TO DIMUON PAIRS USING PYTHIA SOFTWARE
Yusof, Adib
2015-01-01
My project for CERN Summer Student Programme 2015 is on Event Generation of Standard Model Higgs Decay to Dimuon Pairs using Pythia Software. Briefly, Pythia or specifically, Pythia 8.1 is a program for the generation of high-energy Physics events that is able to describe the collisions at any given energies between elementary particles such as Electron, Positron, Proton as well as anti-Proton. It contains theory and models for a number of Physics aspects, including hard and soft interactions, parton distributions, initial-state and final-state parton showers, multiparton interactions, fragmentation and decay. All programming code is to be written in C++ language for this version (the previous version uses FORTRAN) and can be linked to ROOT software for displaying output in form of histogram. For my project, I need to generate events for standard model Higgs Boson into Muon and anti-Muon pairs (H→μ+ μ) to study the expected significance value for this particular process at centre-of-mass energy of 13 TeV...
Matching the Nagy-Soper parton shower at next-to-leading order
Energy Technology Data Exchange (ETDEWEB)
Kraus, Manfred [Institute for Theoretical Particle Physics and Cosmology, RWTH Aachen University (Germany)
2015-07-01
We give a short review of the shower concept, first introduced by Nagy and Soper, that includes full quantum correlations in the shower evolution. We also state the current status of implementation of the publicly available shower program Deductor. However, the main focus of the talk is the matching of the shower at next-to-leading order within the MC rate at NLO formalism. Matching is necessary in order to increase the accuracy of theoretical predictions and to employ a hadronization model. We show first results using Deductor in conjunction with the Helac-NLO framework for top quark pair production in association with one hard jet.
Kardos, Adam; Trócsányi, Zoltán
2015-05-01
We simulate the hadroproduction of a -pair in association with a hard photon at LHC using the PowHel package. These events are almost fully inclusive with respect to the photon, allowing for any physically relevant isolation of the photon. We use the generated events, stored according to the Les-Houches event format, to make predictions for differential distributions formally at the next-to-leading order (NLO) accuracy and we compare these to existing predictions accurate at NLO using the smooth isolation prescription of Frixione. Our fixed-order predictions include the direct-photon contribution only. We also make predictions for distributions after full parton shower and hadronization using the standard experimental cone-isolation of the photon.
International Nuclear Information System (INIS)
Majhi, S.K.; Mukhopadhyay, A.; Ward, B.F.L.; Yost, S.A.
2014-01-01
We present a phenomenological study of the current status of the application of our approach of exact amplitude-based resummation in quantum field theory to precision QCD calculations, by realistic MC event generator methods, as needed for precision LHC physics. We discuss recent results as they relate to the interplay of the attendant IR-improved DGLAP-CS theory of one of us and the precision of exact NLO matrix-element matched parton shower MC’s in the Herwig6.5 environment as determined by comparison to recent LHC experimental observations on single heavy gauge boson production and decay. The level of agreement between the new theory and the data continues to be a reason for optimism. In the spirit of completeness, we discuss as well other approaches to the same theoretical predictions that we make here from the standpoint of physical precision with an eye toward the (sub-)1% QCD⊗EW total theoretical precision regime for LHC physics. - Highlights: • Using LHC data, we show that IR-improved DGLAP-CS kernels with exact NLO Shower/ME matching improves MC precision. • We discuss other possible approaches in comparison with ours. • We propose experimental tests to discriminate between competing approaches
Energy Technology Data Exchange (ETDEWEB)
Majhi, S.K., E-mail: tpskm@iacs.res.in [Indian Association for the Cultivation of Science, Kolkata (India); Mukhopadhyay, A., E-mail: aditi_mukhopadhyay@baylor.edu [Baylor University, Waco, TX (United States); Ward, B.F.L., E-mail: bfl_ward@baylor.edu [Baylor University, Waco, TX (United States); Yost, S.A., E-mail: scott.yost@citadel.edu [The Citadel, Charleston, SC (United States)
2014-11-15
We present a phenomenological study of the current status of the application of our approach of exact amplitude-based resummation in quantum field theory to precision QCD calculations, by realistic MC event generator methods, as needed for precision LHC physics. We discuss recent results as they relate to the interplay of the attendant IR-improved DGLAP-CS theory of one of us and the precision of exact NLO matrix-element matched parton shower MC’s in the Herwig6.5 environment as determined by comparison to recent LHC experimental observations on single heavy gauge boson production and decay. The level of agreement between the new theory and the data continues to be a reason for optimism. In the spirit of completeness, we discuss as well other approaches to the same theoretical predictions that we make here from the standpoint of physical precision with an eye toward the (sub-)1% QCD⊗EW total theoretical precision regime for LHC physics. - Highlights: • Using LHC data, we show that IR-improved DGLAP-CS kernels with exact NLO Shower/ME matching improves MC precision. • We discuss other possible approaches in comparison with ours. • We propose experimental tests to discriminate between competing approaches.
Summary of ATLAS Pythia 8 tunes
The ATLAS collaboration
2012-01-01
We summarize the latest ATLAS Pythia 8 minimum bias and underlying event tunes. The Pythia 8 MPI tunes in this note have been constructed for nine different PDFs, making use of a new x-dependent hadronic matter distribution model.
Coherence effects in parton showers
International Nuclear Information System (INIS)
Pettersson, U.
1988-10-01
A model for gluon emission based on the colour dipole approximation is presented. Gluons are radiated from dipoles that are stretched from one colour charge to the corresponding anti-charge, with probability distribution given by generalizations of the Altarelli-Parisi equations. The model agrees very well with experimental data on e + e - annihilation. For the reaction e + e - -> W + W - -> qq ' QQ ' it is pointed out how to extract information about the QCD vacuum and the confinement mechanism by varying the CM energy. Finally the model is applied to deep inelastic lepton scattering. When a quark is kicked out in the lepton-proton interaction, separation of the colour charges leads to gluon emission. Since the proton remnant is not a pointlike object, coherence conditions lead to an asymmetry between gluons emitted in the forward and in the backward region. The asymmetry is controlled by the energy distribution in the force field. Experimental data are reproduced with a linear energy distribution, which is consistent with the proton behaving as a vortex line in a type II superconductor. (author)
Analysis of Baryon Angular Correlations with Pythia
Mccune, Amara
2017-01-01
Our current understanding of baryon production is encompassed in the framework of the Lund String Fragmentation Model, which is then encoded in the Monte Carlo event generator program Pythia. In proton-proton collisions, daughter particles of the same baryon number produce an anti-correlation in $\\Delta\\eta\\Delta\\varphi$ space in ALICE data, while Pythia programs predict a correlation. To understand this unusual effect, where it comes from, and where our models of baryon production go wrong, correlation functions were systematically generated with Pythia. Effects of energy scaling, color reconnection, and popcorn parameters were investigated.
ATLAS tunes of PYTHIA 6 and Pythia 8 for MC11
The ATLAS collaboration
2011-01-01
We present the latest developments of the ATLAS MC generator tuning project for the Pythia family of event generators, including the C++ Pythia 8 code for the first time. The PYTHIA 6 tunes presented here, titled AMBT2B and AUET2B and constructed for a variety of PDFs, constitute alternatives to the AMBT2/AUET2 tunes previously presented as a candidate for MC11 event simulation. They systematically differ from the AMBT2/AUET2 PYTHIA 6 tunes in the treatment of alpha_S, to address concerns with those tunes. Systematic tune variations are also presented. The Pythia 8 tunes have been constructed for two different PDFs, and are aimed at an optimal description of minimum bias, for use in pile-up simulation. PDF-sensitive effects are observed and discussed in the MPI tunings of both generators.
MBR Monte Carlo Simulation in PYTHIA8
Ciesielski, R.
We present the MBR (Minimum Bias Rockefeller) Monte Carlo simulation of (anti)proton-proton interactions and its implementation in the PYTHIA8 event generator. We discuss the total, elastic, and total-inelastic cross sections, and three contributions from diffraction dissociation processes that contribute to the latter: single diffraction, double diffraction, and central diffraction or double-Pomeron exchange. The event generation follows a renormalized-Regge-theory model, successfully tested using CDF data. Based on the MBR-enhanced PYTHIA8 simulation, we present cross-section predictions for the LHC and beyond, up to collision energies of 50 TeV.
Aspects of perturbative QCD in Monte Carlo shower models
International Nuclear Information System (INIS)
Gottschalk, T.D.
1986-01-01
The perturbative QCD content of Monte Carlo models for high energy hadron-hadron scattering is examined. Particular attention is given to the recently developed backwards evolution formalism for initial state parton showers, and the merging of parton shower evolution with hard scattering cross sections. Shower estimates of K-factors are discussed, and a simple scheme is presented for incorporating 2 → QCD cross sections into shower model calculations without double counting. Additional issues in the development of hard scattering Monte Carlo models are summarized. 69 references, 20 figures
Final state dipole showers and the DGLAP equation
International Nuclear Information System (INIS)
Nagy, Zoltan; Soper, Davison E.
2009-01-01
We study a parton shower description, based on a dipole picture, of the final state in electron-positron annihilation. In such a shower, the distribution function describing the inclusive probability to find a quark with a given energy depends on the shower evolution time. Starting from the exclusive evolution equation for the shower, we derive an equation for the evolution of the inclusive quark energy distribution in the limit of strong ordering in shower evolution time of the successive parton splittings. We find that, as expected, this is the DGLAP equation. This paper is a response to a recent paper of Dokshitzer and Marchesini that raised troubling issues about whether a dipole based shower could give the DGLAP equation for the quark energy distribution.
Effects produced by multi-parton interactions and color reconnection in small systems
Energy Technology Data Exchange (ETDEWEB)
Cuautle, Eleazar; Ortiz, Antonio; Paić, Guy
2016-12-15
Multi-parton interactions and color reconnection can produce QGP-like effects in small systems, specifically, radial flow-like patterns. For pp collisions simulated with Pythia 8.212, in this work we investigate their effects on different observables like event multiplicity, event shapes and transverse momentum distributions.
Energy Technology Data Exchange (ETDEWEB)
Ebata, T [Tohoku Univ., Sendai (Japan). Coll. of General Education
1976-06-01
The geometrical distribution inferred from the inelastic cross section is assumed to be proportional to the partial waves. The precocious scaling and the Q/sup 2/-dependence of various quantities are treated from the geometrical point of view. It is shown that the approximate conservation of the orbital angular momentum may be a very practical rule to understand the helicity structure of various hadronic and electromagnetic reactions. The rule can be applied to inclusive reactions as well. The model is also applied to large angle processes. Through the discussion, it is suggested that many peculiar properties of the quark-parton can be ascribed to the geometrical effects.
Kersevan, Borut Paul; Richter-Waş, Elzbieta
2013-03-01
The AcerMC Monte Carlo generator is dedicated to the generation of Standard Model background processes which were recognised as critical for the searches at LHC, and generation of which was either unavailable or not straightforward so far. The program itself provides a library of the massive matrix elements (coded by MADGRAPH) and native phase space modules for generation of a set of selected processes. The hard process event can be completed by the initial and the final state radiation, hadronisation and decays through the existing interface with either PYTHIA, HERWIG or ARIADNE event generators and (optionally) TAUOLA and PHOTOS. Interfaces to all these packages are provided in the distribution version. The phase-space generation is based on the multi-channel self-optimising approach using the modified Kajantie-Byckling formalism for phase space construction and further smoothing of the phase space was obtained by using a modified ac-VEGAS algorithm. An additional improvement in the recent versions is the inclusion of the consistent prescription for matching the matrix element calculations with parton showering for a select list of processes. Catalogue identifier: ADQQ_v2_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADQQ_v2_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 3853309 No. of bytes in distributed program, including test data, etc.: 68045728 Distribution format: tar.gz Programming language: FORTRAN 77 with popular extensions (g77, gfortran). Computer: All running Linux. Operating system: Linux. Classification: 11.2, 11.6. External routines: CERNLIB (http://cernlib.web.cern.ch/cernlib/), LHAPDF (http://lhapdf.hepforge.org/) Catalogue identifier of previous version: ADQQ_v1_0 Journal reference of previous version: Comput. Phys. Comm. 149(2003)142 Does
Risk and the Internet of Things: Damocles, Pythia, or Pandora?
Showell, Chris
2016-01-01
The Internet of Things holds great promise for healthcare, but also embodies a number of risks. This analysis suggests that the risks are as yet poorly delineated (having features in common with the oracle Pythia, and with Pandora and her box), and that adopting the precautionary principle is appropriate.
Signatures of Parton Exogamy in e+ e- -> W+ W- -> hadrons
Ellis, John; Geiger, Klaus
1997-01-01
We propose possible signatures of `exogamous' combinations between partons in the different W+ and W- hadron showers in e+e- -> W+W- events with purely hadronic final states. Within the space-time model for hadronic shower development that we have proposed previously, we find a possible difference of about 10 % between the mean hadronic multiplicity in such purely hadronic final states and twice the hadronic multiplicity in events in which one W decays hadronically and the other leptonically,...
Helicity antenna showers for hadron colliders
Energy Technology Data Exchange (ETDEWEB)
Fischer, Nadine; Skands, Peter [Monash University, School of Physics and Astronomy, Clayton, VIC (Australia); Lifson, Andrew [Monash University, School of Physics and Astronomy, Clayton, VIC (Australia); ETH Zuerich, Zurich (Switzerland)
2017-10-15
We present a complete set of helicity-dependent 2 → 3 antenna functions for QCD initial- and final-state radiation. The functions are implemented in the Vincia shower Monte Carlo framework and are used to generate showers for hadron-collider processes in which helicities are explicitly sampled (and conserved) at each step of the evolution. Although not capturing the full effects of spin correlations, the explicit helicity sampling does permit a significantly faster evaluation of fixed-order matrix-element corrections. A further speed increase is achieved via the implementation of a new fast library of analytical MHV amplitudes, while matrix elements from Madgraph are used for non-MHV configurations. A few examples of applications to QCD 2 → 2 processes are given, comparing the newly released Vincia 2.200 to Pythia 8.226. (orig.)
Helicity antenna showers for hadron colliders
Fischer, Nadine; Lifson, Andrew; Skands, Peter
2017-10-01
We present a complete set of helicity-dependent 2→ 3 antenna functions for QCD initial- and final-state radiation. The functions are implemented in the Vincia shower Monte Carlo framework and are used to generate showers for hadron-collider processes in which helicities are explicitly sampled (and conserved) at each step of the evolution. Although not capturing the full effects of spin correlations, the explicit helicity sampling does permit a significantly faster evaluation of fixed-order matrix-element corrections. A further speed increase is achieved via the implementation of a new fast library of analytical MHV amplitudes, while matrix elements from Madgraph are used for non-MHV configurations. A few examples of applications to QCD 2→ 2 processes are given, comparing the newly released Vincia 2.200 to Pythia 8.226.
Multiple parton interactions in photoproduction at HERA/H1
Energy Technology Data Exchange (ETDEWEB)
Magro, Lluis Marti
2009-02-15
Photoproduction data of HERA-I are analysed by requiring dijets with transverse momenta of at least 5 GeV. The two jets define in azimuth a towards region (leading jet), an away region (usually the 2nd jet) and transverse regions between them. The charged particle and jet with low transverse momentum multiplicity, so called minijets, are measured in these regions as a function of the variables x{sup obs}{sub {gamma}} and P{sup Jet{sub 1T}} (leading jet). The measurement is compared to predictions including parton showers and matrix elements at leading order in {alpha}{sub s}. Some predictions include contributions from multiple parton interactions and use different parton evolution equations. It was found that existing MC programs do not fully describe the measurements but the description can be improved by including multiple parton interactions. (orig.)
Structure functions and parton distributions
International Nuclear Information System (INIS)
Olness, F.; Tung, Wu-Ki
1991-04-01
Activities of the structure functions and parton distributions group is summarized. The impact of scheme-dependence of parton distributions (especially sea-quarks and gluons) on the quantitative formulation of the QCD parton model is highlighted. Recent progress on the global analysis of parton distributions is summarized. Issues on the proper use of the next-to-leading parton distributions are stressed
Pythia: A Privacy-enhanced Personalized Contextual Suggestion System for Tourism
Drosatos, G.; Efraimidis, P.S.; Arampatzis, A.; Stamatelatos, G.; Athanasiadis, I.N.
2015-01-01
We present Pythia, a privacy-enhanced non-invasive contextual suggestion system for tourists, with important architectural innovations. The system offers high quality personalized recommendations, non-invasive operation and protection of user privacy. A key feature of Pythia is the exploitation of
Electroweak splitting functions and high energy showering
Chen, Junmou; Han, Tao; Tweedie, Brock
2017-11-01
We derive the electroweak (EW) collinear splitting functions for the Standard Model, including the massive fermions, gauge bosons and the Higgs boson. We first present the splitting functions in the limit of unbroken SU(2) L × U(1) Y and discuss their general features in the collinear and soft-collinear regimes. These are the leading contributions at a splitting scale ( k T ) far above the EW scale ( v). We then systematically incorporate EW symmetry breaking (EWSB), which leads to the emergence of additional "ultra-collinear" splitting phenomena and naive violations of the Goldstone-boson Equivalence Theorem. We suggest a particularly convenient choice of non-covariant gauge (dubbed "Goldstone Equivalence Gauge") that disentangles the effects of Goldstone bosons and gauge fields in the presence of EWSB, and allows trivial book-keeping of leading power corrections in v/ k T . We implement a comprehensive, practical EW showering scheme based on these splitting functions using a Sudakov evolution formalism. Novel features in the implementation include a complete accounting of ultra-collinear effects, matching between shower and decay, kinematic back-reaction corrections in multi-stage showers, and mixed-state evolution of neutral bosons ( γ/ Z/ h) using density-matrices. We employ the EW showering formalism to study a number of important physical processes at O (1-10 TeV) energies. They include (a) electroweak partons in the initial state as the basis for vector-boson-fusion; (b) the emergence of "weak jets" such as those initiated by transverse gauge bosons, with individual splitting probabilities as large as O (35%); (c) EW showers initiated by top quarks, including Higgs bosons in the final state; (d) the occurrence of O (1) interference effects within EW showers involving the neutral bosons; and (e) EW corrections to new physics processes, as illustrated by production of a heavy vector boson ( W ') and the subsequent showering of its decay products.
Double Parton Scattering in 4-jet production at the LHC with and without open b-bar
Serino, Mirko; Kutak, Krzysztof; van Hameren, Andreas; Bury, Marcin
2018-01-01
We report the preliminary results of the ongoing update of our study of 4-jet production at the LHC in High Energy Factorization, which is being supplemented by parton showers. We focus on a specific angular variable introduced in two papers by the CMS collaboration on 4-jet production with and without two b-tagged jets. The variable is, by construction, sensitive to contributions from Multi Parton Interactions (MPIs), specifically hard Double Parton Scattering (DPS). We preliminarily find that, adding parton showers to the single parton scattering channel, the evidence for the need for MPIs is compatible with the one reported by the CMS collaboration after a comparison of the data with simulations based on collinear Monte Carlo event generators.
Double Parton Scattering in 4-jet production at the LHC with and without open b-bar
Serino, Mirko; Kutak, Krzysztof; van Hameren, Andreas; Bury, Marcin
2017-01-01
We report the preliminary results of the ongoing update of our study of 4-jet production at the LHC in High Energy Factorization, which is being supplemented by parton showers. We focus on a specific angular variable introduced in two papers by the CMS collaboration on 4-jet production with and without two b-tagged jets. The variable is, by construction, sensitive to contributions from Multi Parton Interactions (MPIs), specifically hard Double Parton Scattering (DPS). We preliminarily find that, adding parton showers to the single parton scattering channel, the evidence for the need for MPIs is compatible with the one reported by the CMS collaboration after a comparison of the data with simulations based on collinear Monte Carlo event generators.
Are Parton Distributions Positive?
Forte, Stefano; Ridolfi, Giovanni; Altarelli, Guido; Forte, Stefano; Ridolfi, Giovanni
1999-01-01
We show that the naive positivity conditions on polarized parton distributions which follow from their probabilistic interpretation in the naive parton model are reproduced in perturbative QCD at the leading log level if the quark and gluon distribution are defined in terms of physical processes. We show how these conditions are modified at the next-to-leading level, and discuss their phenomenological implications, in particular in view of the determination of the polarized gluon distribution
Are parton distributions positive?
International Nuclear Information System (INIS)
Forte, Stefano; Altarelli, Guido; Ridolfi, Giovanni
1999-01-01
We show that the naive positivity conditions on polarized parton distributions which follow from their probabilistic interpretation in the naive parton model are reproduced in perturbative QCD at the leading log level if the quark and gluon distribution are defined in terms of physical processes. We show how these conditions are modified at the next-to-leading level, and discuss their phenomenological implications, in particular in view of the determination of the polarized gluon distribution
Parton Distributions Working Group
International Nuclear Information System (INIS)
Barbaro, L. de; Keller, S. A.; Kuhlmann, S.; Schellman, H.; Tung, W.-K.
2000-01-01
This report summarizes the activities of the Parton Distributions Working Group of the QCD and Weak Boson Physics workshop held in preparation for Run II at the Fermilab Tevatron. The main focus of this working group was to investigate the different issues associated with the development of quantitative tools to estimate parton distribution functions uncertainties. In the conclusion, the authors introduce a Manifesto that describes an optimal method for reporting data
Analytic solutions of QCD evolution equations for parton cascades inside nuclear matter at small x
International Nuclear Information System (INIS)
Geiger, K.
1994-01-01
An analytical method is presented to solve generalized QCD evolution equations for the time development of parton cascades in a nuclear environment. In addition to the usual parton branching processes in vacuum, these evolution equations provide a consistent description of interactions with the nuclear medium by accounting for stimulated branching processes, fusion, and scattering processes that are specific to QCD in a medium. Closed solutions for the spectra of produced partons with respect to the variables time, longitudinal momentum, and virtuality are obtained under some idealizing assumptions about the composition of the nuclear medium. Several characteristic features of the resulting parton distributions are discussed. One of the main conclusions is that the evolution of a parton shower in a medium is dilated as compared to free space and is accompanied by an enhancement of particle production. These effects become stronger with increasing nuclear density
International Nuclear Information System (INIS)
Close, F.E.
1976-01-01
The studies of inelastic electron scattering at SLAC and of neutrino scattering at CERN have been widely interpreted as giving support to the idea that the nucleon is built from elementary constituents, called partons, and that these partons have the same quantum numbers as the quarks that are familiar in spectroscopy. In particular, a very simple regularity in the data, known as scale invariance or just 'scaling' was seen at least at moderate energies (2 2 > approximately 1 GeV) which is natural in the parton model. The data on e + e - annihilation also appear to be consistent with scaling when Esub(cm) approximately 5 GeV. These lectures are concerned with the scaling phenomena. One may expect the new hadronic degree of freedom to generate scaling violations in inelastic electron and neutrino scattering. These are mentioned briefly in these lectures. (Auth.)
Multi parton interactions and multi parton distributions in QCD
International Nuclear Information System (INIS)
Diehl, M.
2012-01-01
After a brief recapitulation of the general interest of parton densities, we discuss multiple hard interactions and multi parton distributions. We report on recent theoretical progress in their QCD description, on outstanding conceptual problems and on possibilities to use multi parton distributions as a laboratory to test and improve our understanding of hadron structure. (author)
Multiplicities and parton dynamics
International Nuclear Information System (INIS)
Knuteson, R.O.
1987-01-01
The production of strongly interacting particles from the annihilation of electrons and positrons at high energies is studied, with emphasis on the multiplicity, or number, of particles produced. A probabilistic branching model based on the leading log approximation in QCD is formulated to predict the evolution of particle number with the energy of collision. Direct integration of a master equation for the probabilities allows a comparison to the experimentally observed particle distribution. The production of strongly interacting particles from proton-antiproton collisions is also considered. A model for the production of particles from parton-parton collisions is presented and the growth in multiplicity with energy demonstrated
Are partons confined tachyons?
International Nuclear Information System (INIS)
Noyes, H.P.
1996-03-01
The author notes that if hadrons are gravitationally stabilized ''black holes'', as discrete physics suggests, it is possible that partons, and in particular quarks, could be modeled as tachyons, i.e. particles having v 2 > c 2 , without conflict with the observational fact that neither quarks nor tachyons have appeared as ''free particles''. Some consequences of this model are explored
International Nuclear Information System (INIS)
Hwa, R.C.
1978-08-01
Low P/sub T/ meson production in hadronic collisions is described in the framework of the parton model. The recombination of quark and antiquark is suggested as the dominant mechanism in the large x region. Phenomenological evidences for the mechanism are given. The application to meson initiated reactions yields the quark distribution in mesons. 21 references
QCD-aware partonic jet clustering for truth-jet flavour labelling
Energy Technology Data Exchange (ETDEWEB)
Buckley, Andy; Pollard, Chris [University of Glasgow, School of Physics and Astronomy, Glasgow (United Kingdom)
2016-02-15
We present an algorithm for deriving partonic flavour labels to be applied to truth particle jets in Monte Carlo event simulations. The inputs to this approach are final pre-hadronisation partons, to remove dependence on unphysical details such as the order of matrix element calculation and shower generator frame recoil treatment. These are clustered using standard jet algorithms, modified to restrict the allowed pseudo-jet combinations to those in which tracked flavour labels are consistent with QCD and QED Feynman rules. The resulting algorithm is shown to be portable between the major families of shower generators, and largely insensitive to many possible systematic variations: it hence offers significant advantages over existing ad hoc labelling schemes. However, it is shown that contamination from multi-parton scattering simulations can disrupt the labelling results. Suggestions are made for further extension to incorporate more detailed QCD splitting function kinematics, robustness improvements, and potential uses for truth-level physics object definitions and tagging. (orig.)
QCD-aware partonic jet clustering for truth-jet flavour labelling
International Nuclear Information System (INIS)
Buckley, Andy; Pollard, Chris
2016-01-01
We present an algorithm for deriving partonic flavour labels to be applied to truth particle jets in Monte Carlo event simulations. The inputs to this approach are final pre-hadronisation partons, to remove dependence on unphysical details such as the order of matrix element calculation and shower generator frame recoil treatment. These are clustered using standard jet algorithms, modified to restrict the allowed pseudo-jet combinations to those in which tracked flavour labels are consistent with QCD and QED Feynman rules. The resulting algorithm is shown to be portable between the major families of shower generators, and largely insensitive to many possible systematic variations: it hence offers significant advantages over existing ad hoc labelling schemes. However, it is shown that contamination from multi-parton scattering simulations can disrupt the labelling results. Suggestions are made for further extension to incorporate more detailed QCD splitting function kinematics, robustness improvements, and potential uses for truth-level physics object definitions and tagging. (orig.)
Thermalization through parton transport
International Nuclear Information System (INIS)
Zhang Bin
2010-01-01
A radiative transport model is used to study kinetic equilibration during the early stage of a relativistic heavy ion collision. The parton system is found to be able to overcome expansion and move toward thermalization via parton collisions. Scaling behaviors show up in both the pressure anisotropy and the energy density evolutions. In particular, the pressure anisotropy evolution shows an approximate α s scaling when radiative processes are included. It approaches an asymptotic time evolution on a time scale of 1 to 2 fm/c. The energy density evolution shows an asymptotic time evolution that decreases slower than the ideal hydro evolution. These observations indicate that partial thermalization can be achieved and viscosity is important for the evolution during the early longitudinal expansion stage of a relativistic heavy ion collision.
Are partons confined tachyons?
Energy Technology Data Exchange (ETDEWEB)
Noyes, H.P.
1996-03-01
The author notes that if hadrons are gravitationally stabilized ``black holes``, as discrete physics suggests, it is possible that partons, and in particular quarks, could be modeled as tachyons, i.e. particles having v{sup 2} > c{sup 2}, without conflict with the observational fact that neither quarks nor tachyons have appeared as ``free particles``. Some consequences of this model are explored.
International Nuclear Information System (INIS)
Paschos, E.A.
1976-08-01
The quark parton model describes the inclusive electro- and neutrino production data if a clear distinction is made between reactions which take place at high and at low energies. For the low energy region the classical view of six structure functions of the proton is still adequate. For the high energy region models can be constructed which are consistent with the experimental data. (BJ) [de
Scalable Data Quality for Big Data: The Pythia Framework for Handling Missing Values.
Cahsai, Atoshum; Anagnostopoulos, Christos; Triantafillou, Peter
2015-09-01
Solving the missing-value (MV) problem with small estimation errors in large-scale data environments is a notoriously resource-demanding task. The most widely used MV imputation approaches are computationally expensive because they explicitly depend on the volume and the dimension of the data. Moreover, as datasets and their user community continuously grow, the problem can only be exacerbated. In an attempt to deal with such a problem, in our previous work, we introduced a novel framework coined Pythia, which employs a number of distributed data nodes (cohorts), each of which contains a partition of the original dataset. To perform MV imputation, the Pythia, based on specific machine and statistical learning structures (signatures), selects the most appropriate subset of cohorts to perform locally a missing value substitution algorithm (MVA). This selection relies on the principle that particular subset of cohorts maintains the most relevant partition of the dataset. In addition to this, as Pythia uses only part of the dataset for imputation and accesses different cohorts in parallel, it improves efficiency, scalability, and accuracy compared to a single machine (coined Godzilla), which uses the entire massive dataset to compute imputation requests. Although this article is an extension of our previous work, we particularly investigate the robustness of the Pythia framework and show that the Pythia is independent from any MVA and signature construction algorithms. In order to facilitate our research, we considered two well-known MVAs (namely K-nearest neighbor and expectation-maximization imputation algorithms), as well as two machine and neural computational learning signature construction algorithms based on adaptive vector quantization and competitive learning. We prove comprehensive experiments to assess the performance of the Pythia against Godzilla and showcase the benefits stemmed from this framework.
Double parton scattering. A tale of two partons
Energy Technology Data Exchange (ETDEWEB)
Kasemets, Tomas
2013-08-15
Double parton scattering in proton-proton collisions can give sizable contributions to final states in parts of phase space. We investigate the correlations between the partons participating in the two hard interactions of double parton scattering. With a detailed calculation of the differential cross section for the double Drell-Yan process we demonstrate how initial state correlations between the partons affect the rate and distribution of final state particles. We present our results with focus on correlations between the polarizations of the partons. In particular transversely polarized quarks lead to a dependence of the cross section on angles between final state particles of the two hard interactions, and thereby on the invariant mass of particle pairs. The size of the spin correlations, and therewith the degree to which the final state particles are correlated, depends on unknown double parton distributions. We derive positivity bounds on the double parton distributions that follow from their interpretation as probability densities, taking into account all possible spin correlations between two partons in an unpolarized proton. We show that the bounds are stable under homogeneous leading-order DGLAP evolution to higher scales. We make direct use of the positivity bounds in numerical investigations on the double DGLAP evolution for two linearly polarized gluons and for two transversely polarized quarks. We find that the linearly polarized gluons are likely to be negligible at high scales but that transversely polarized quarks can still play a significant role. We examine the dependence of the double parton distributions on the transverse distance between the two partons, and therewith between the two hard interactions. We further study the interplay between transverse and longitudinal variables of the distributions, as well as the impact of the differences in integration limits between the evolution equations for single and double parton distributions. (orig.)
Factorization of in-medium parton branching beyond the eikonal approximation
Apolinário, Liliana; Armesto, Néstor; Milhano, José Guilherme; Salgado, Carlos A.
2017-08-01
The description of the in-medium modifications of partonic showers is at the forefront of current theoretical and experimental efforts in heavy-ion physics. The theory of jet quenching, a commonly used alias for the modifications of the parton branching resulting from the interactions with the QGP, has been significantly developed over the last years. Within a weak coupling approach, several elementary processes that build up the parton shower evolution, such as single gluon emissions, interference effects between successive emissions and corrections to radiative energy loss off massive quarks, have been addressed both at eikonal accuracy and beyond by taking into account the Brownian motion that high-energy particles experience when traversing a hot and dense medium. In this work, by using the setup of single gluon emission from a color correlated quark-antiquark pair in a singlet state (q- q ‾ antenna), we calculate the in-medium gluon radiation spectrum beyond the eikonal approximation. This allows to fully explore the physical interplay between broadening and coherence/decoherence effects. The results show that we are able to factorize broadening effects from the modifications of the radiation process itself. This provides a very strong indication that a probabilistic picture of parton shower evolution holds even in the presence of a QGP, a feature that is of the utmost importance for a successful future generation of Jet quenching Monte Carlos.
Directory of Open Access Journals (Sweden)
Kulagin S. A.
2017-01-01
Full Text Available We review a microscopic model of the nuclear parton distribution functions, which accounts for a number of nuclear effects including Fermi motion and nuclear binding, nuclear meson-exchange currents, off-shell corrections to bound nucleon distributions and nuclear shadowing. We also discuss applications of this model to a number of processes including lepton-nucleus deep inelastic scattering, proton-nucleus Drell-Yan lepton pair production at Fermilab, as well as W± and Z0 boson production in proton-lead collisions at the LHC.
The ATLAS collaboration
2017-01-01
A study of the performance of various colour reconnection models included in the Pythia8 Monte Carlo event generator is performed using leading charged-particle underlying event data in three centre-of-mass energies from Run 1 and Run 2, measured in ATLAS. Each model can be tuned to describe the data reasonably well.
Parton distributions with QED corrections
Collaboration, The NNPDF; Ball, Richard D.; Bertone, Valerio; Carrazza, Stefano; Debbio, Luigi Del; Forte, Stefano; Guffanti, Alberto; Hartland, Nathan P.; Rojo, Juan
2013-01-01
We present a set of parton distribution functions (PDFs), based on the NNPDF2.3 set, which includes a photon PDF, and QED contributions to parton evolution. We describe the implementation of the combined QCD+QED evolution in the NNPDF framework. We then provide a first determination of the full set
International Nuclear Information System (INIS)
Mundim Filho, Luiz Martins; Carvalho, Wagner de Paula
2012-01-01
Full text: CASTOR (Centaur And Strange Object Research) is an electromagnetic (EM) and hadronic (HAD) calorimeter, based on tungsten and quartz plates, operating in the CMS Detector (Compact Muon Solenoid) at LHC. The calorimeter detects Cerenkov radiation and is positioned around the beam pipe in the very forward region of CMS (at 14.38 m from the interaction point), covering the pseudo-rapidity range between -6.6 ≤ η≤-5.1 . It is longitudinally segmented into 14 sections, 2 for the EM and 12 for the HAD parts and is 16-fold azimuthally symmetric around the beam pipe. A Shower Library is needed for CASTOR Monte Carlo simulation, as the full simulation of showers takes a long time and the high multiplicity of particles in the forward region makes this simulation very time consuming. The Shower Library is used as a look-up table in the form of a ROOT file, so that when a simulated particle enters the detector with a certain energy and direction, characterized by the azimuthal angle φ and the pseudo-rapidity η, instead of making the full simulation of the shower in CASTOR, it is substituted by one already stored in the Shower Library. Showers corresponding to two types of particles are included in the Shower Library: electrons (or photons) and charged pions. The software implemented to make the Shower Library is described, as well as the validation of this library and timing studies. This package has been developed in the context of the official software of the CMS Collaboration, CMSSW. (author)
Parton distribution in relativistic hadrons
International Nuclear Information System (INIS)
Kopeliovich, B.Z.; Lapidus, L.I.; Zamolodchikov, Al.B.
1979-01-01
The distribution in the slow-parton number in the relativistic hadron is considered as a function of its rapidity (y). Neglecting corrections due to the tarton chain recombination the equation is derived and its explicit solution is found. It describes this distribution depending on the initial distribution at y approximately 1. Comparison with the reggeon diagrams results in relations between the parton model and the regaeon field theory parameters. The interpretation of the cutting rules in the framework of the parton model is presented. The numerical estimation of the parton model parameters is performed. It is shown that the slow-parton density corresponding to accessible energies seems to be close to the saturated density. Therefore, the enhanced graphs contributions turn out to be of considerable importance
Signatures of Parton Exogamy in $e^+ e^- \\to W^+ W^- \\to$ hadrons
Ellis, Jonathan Richard; Ellis, John; Geiger, Klaus
1997-01-01
We propose possible signatures of `exogamous' combinations between partons in the different W+ and W- hadron showers in e+e- -> W+W- events with purely hadronic final states. Within the space-time model for hadronic shower development that we have proposed previously, we find a possible difference of about 10 % between the mean hadronic multiplicity in such purely hadronic final states and twice the hadronic multiplicity in events in which one W decays hadronically and the other leptonically, i.e., \
Real emission and virtual exchange of gravitons and unparticles in Pythia8
International Nuclear Information System (INIS)
Ask, S.; Akin, I.V.; Benucci, L.; Roeck, A. de; Goebel, M.; Haller, J.
2009-12-01
Models with large extra dimensions as well as unparticle models could give rise to new phenomena at collider experiments due to real emission or virtual exchange of gravitons or unparticles. In this paper we present the common implementation of these processes in the Monte Carlo generator Pythia8, using relations between the parameters of the two models. The program offers several options related to the treatment of the UV region of the effective theories, including the possibility of using a form factor for the running gravitational coupling. Characteristic results obtained with Pythia8 have been used to validate the implementations as well as to illustrate the key features and effects of the model parameters. The results presented in this paper are focused on mono-jet, di-photon and di-lepton final states at the LHC. (orig.)
Real emission and virtual exchange of gravitons and unparticles in Pythia8
Energy Technology Data Exchange (ETDEWEB)
Ask, S. [Manchester Univ. (United Kingdom); Akin, I.V. [Middle East Technical Univ., Ankara (Turkey); Benucci, L. [Universitaire Instelling Antwerpen, Wilrijk (Belgium); Roeck, A. de [Universitaire Instelling Antwerpen, Wilrijk (Belgium); European Lab. for Particle Physics (CERN), Geneva (Switzerland); Goebel, M. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Hamburg Univ. (Germany); Haller, J. [Hamburg Univ. (Germany)
2009-12-15
Models with large extra dimensions as well as unparticle models could give rise to new phenomena at collider experiments due to real emission or virtual exchange of gravitons or unparticles. In this paper we present the common implementation of these processes in the Monte Carlo generator Pythia8, using relations between the parameters of the two models. The program offers several options related to the treatment of the UV region of the effective theories, including the possibility of using a form factor for the running gravitational coupling. Characteristic results obtained with Pythia8 have been used to validate the implementations as well as to illustrate the key features and effects of the model parameters. The results presented in this paper are focused on mono-jet, di-photon and di-lepton final states at the LHC. (orig.)
Q-PYTHIA: a medium-modified implementation of final state radiation
Armesto, Néstor; Cunqueiro, Leticia; Salgado, Carlos A.
2009-10-01
We present a Monte Carlo implementation, within PYTHIA, of medium-induced gluon radiation in the final state branching process. Medium effects are introduced through an additive term in the splitting functions computed in the multiple-soft scattering approximation. The observable effects of this modification are studied for different quantities as fragmentation functions and the hump-backed plateau, and transverse momentum and angular distributions. The anticipated increase of intra-jet multiplicities, energy loss of the leading particle and jet broadening are observed as well as modifications of naive expectations based solely on analytical calculations. This shows the adequacy of a Monte Carlo simulator for jet analyses. Effects of hadronization are found to wash out medium effects in the soft region, while the main features remain. To show the performance of the implementation and the feasibility of our approach in realistic experimental situations we provide some examples: fragmentation functions, nuclear suppression factors, jet shapes and jet multiplicities. The package containing the modified routines is available for public use. This code, which is not an official PYTHIA release, is called Q-PYTHIA. We also include a short manual to perform the simulations of jet quenching.
The partonic nature of instantons
International Nuclear Information System (INIS)
Collie, Benjamin; Tong, David
2009-01-01
In both Yang-Mills theories and sigma models, instantons are endowed with degrees of freedom associated to their scale size and orientation. It has long been conjectured that these degrees of freedom have a dual interpretation as the positions of partonic constituents of the instanton. These conjectures are usually framed in d = 3+1 and d = 1+1 dimensions respectively where the partons are supposed to be responsible for confinement and other strong coupling phenomena. We revisit this partonic interpretation of instantons in the context of d = 4+1 and d = 2+1 dimensions. Here the instantons are particle-like solitons and the theories are non-renormalizable. We present an explicit and calculable model in d = 2+1 dimensions where the single soliton in the CP N sigma-model can be shown to be a multi-particle state whose partons are identified with the ultra-violet degrees of freedom which render the theory well-defined at high energies. We introduce a number of methods which reveal the partons inside the soliton, including deforming the sigma model and a dual version of the Bogomolnyi equations. We conjecture that partons inside Yang-Mills instantons hold the key to understanding the ultra-violet completion of five-dimensional gauge theories.
Charge symmetry at the partonic level
Energy Technology Data Exchange (ETDEWEB)
Londergan, J. T.; Peng, J. C.; Thomas, A. W.
2010-07-01
This review article discusses the experimental and theoretical status of partonic charge symmetry. It is shown how the partonic content of various structure functions gets redefined when the assumption of charge symmetry is relaxed. We review various theoretical and phenomenological models for charge symmetry violation in parton distribution functions. We summarize the current experimental upper limits on charge symmetry violation in parton distributions. A series of experiments are presented, which might reveal partonic charge symmetry violation, or alternatively might lower the current upper limits on parton charge symmetry violation.
Deep-Inelastic Final States in a Space-Time Description of Shower Development and Hadronization
Ellis, John; Geiger, Klaus; Kowalski, Henryk
1996-01-01
We extend a quantum kinetic approach to the description of hadronic showers in space, time and momentum space to deep-inelastic $ep$ collisions, with particular reference to experiments at HERA. We follow the history of hard scattering events back to the initial hadronic state and forward to the formation of colour-singlet pre-hadronic clusters and their decays into hadrons. The time evolution of the space-like initial-state shower and the time-like secondary partons are treated similarly, an...
Hadron seagulls and parton jets
International Nuclear Information System (INIS)
Satz, H.; Zarmi, Y.
1976-01-01
For the lepton production of hadrons in the current fragmentation region it was recently shown that the two-level partonic picture leads to a broadening of the average transverse momentum of the observed secondaries. This ''seagull'' effect is well known for hadron-hadron interactions. In the note it is considered the possibility that parton arguments can explain it here as well and it is discussed what information on the constituent structure of hadrons can be obtained through an investigation of the seagull effect from such a point of view. It is shown that a non trivial seagull effect is a consequence of a simple two step production mechanism and the parton model predicts significant differences between baryon, meson and virtual-photon fragmentation seagull
New information on parton distributions
International Nuclear Information System (INIS)
Martin, A.D.; Stirling, W.J.; Roberts, R.G.
1992-04-01
New data on structure functions from deep-inelastic scattering provide new information on parton distributions, particularly in the 0.01 2 data from the New Muon Collaboration (NMC) and its implications for other processes, and the evidence for SU(2) symmetry breaking in the light quark sea. We show that although good fits can be obtained with or without this symmetry breaking, more physically reasonable parton distributions are obtained if we allow d-bar > u-bar at small x. With the inclusion of the latest deep-inelastic data we find α s (M Z ) = 0.111 -0.005 +0.004 . We also show how W, Z and Drell-Yan production at p-barp colliders can give information on parton distributions. (Author)
On positivity of parton distributions
International Nuclear Information System (INIS)
Altarelli, G.; Forte, S.; Ridolfi, G.
1998-01-01
We discuss the bounds on polarized parton distributions which follow from their definition in terms of cross section asymmetries. We spell out how the bounds obtained in the naive parton model can be derived within perturbative QCD at leading order when all quark and gluon distributions are defined in terms of suitable physical processes. We specify a convenient physical definition for the polarized and unpolarized gluon distributions in terms of Higgs production from gluon fusion. We show that these bounds are modified by subleading corrections, and we determine them up to NLO. We examine the ensuing phenomenological implications, in particular in view of the determination of the polarized gluon distribution. (orig.)
On positivity of parton distributions
Altarelli, Guido; Ridolfi, G; Altarelli, Guido; Forte, Stefano; Ridolfi, Giovanni
1998-01-01
We discuss the bounds on polarized parton distributions which follow from their definition in terms of cross section asymmetries. We spell out how the bounds obtained in the naive parton model can be derived within perturbative QCD at leading order when all quark and gluon distributions are defined in terms of suitable physical processes. We specify a convenient physical definition for the polarized and unpolarized gluon distributions in terms of Higgs production from gluon fusion. We show that these bounds are modified by subleading corrections, and we determine them up to NLO. We examine the ensuing phenomenological implications, in particular in view of the determination of the polarized gluon distribution.
Imaging partons in exclusive scattering processes
Energy Technology Data Exchange (ETDEWEB)
Diehl, Markus
2012-06-15
The spatial distribution of partons in the proton can be probed in suitable exclusive scattering processes. I report on recent performance estimates for parton imaging at a proposed Electron-Ion Collider.
Hadron Correlations and Parton Recombination
Energy Technology Data Exchange (ETDEWEB)
Fries, R.J. [School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455 (United States)]. E-mail: rjfries@comp.tamu.edu
2007-02-15
Parton recombination has been found to be an extremely useful model to understand hadron production at the Relativistic Heavy Ion Collider. It is particularly important to explore its connections with hard processes. This article reviews some of the aspects of the quark recombination model and places particular emphasis on hadron correlations.
Hadronization of dense partonic matter
Energy Technology Data Exchange (ETDEWEB)
Fries, Rainer J [School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455 (United States)
2006-12-15
The parton recombination model has turned out to be a valuable tool to describe hadronization in high-energy heavy-ion collisions. I review the model and revisit recent progress in our understanding of hadron correlations. I also discuss higher Fock states in the hadrons, possible violations of the elliptic flow scaling and recombination effects in more dilute systems.
Parton distributions with LHC data
Ball, Richard D.; Bertone, Valerio; Carrazza, Stefano; Deans, Christopher S.; Debbio, Luigi Del; Forte, Stefano; Guffanti, Alberto; Hartland, Nathan P.; Latorre, Jose I.; Rojo, Juan; Ubiali, Maria
2013-01-01
We present the first determination of parton distributions of the nucleon at NLO and NNLO based on a global data set which includes LHC data: NNPDF2.3. Our data set includes, besides the deep inelastic, Drell-Yan, gauge boson production and jet data already used in previous global PDF
Dual model for parton densities
International Nuclear Information System (INIS)
El Hassouni, A.; Napoly, O.
1981-01-01
We derive power-counting rules for quark densities near x=1 and x=0 from parton interpretations of one-particle inclusive dual amplitudes. Using these rules, we give explicit expressions for quark distributions (including charm) inside hadrons. We can then show the compatibility between fragmentation and recombination descriptions of low-p/sub perpendicular/ processes
What Exactly is a Parton Density ?
International Nuclear Information System (INIS)
Collins, J.C.
2003-01-01
I give an account of the definitions of parton densities, both the conventional ones, integrated over parton transverse momentum, and unintegrated transverse-momentum-dependent densities. The aim is to get a precise and correct definition of a parton density as the target expectation value of a suitable quantum mechanical operator, so that a clear connection to non-perturbative QCD is provided. Starting from the intuitive ideas in the parton model that predate QCD, we will see how the simplest operator definitions suffer from divergences. Corrections to the definition are needed to eliminate the divergences. An improved definition of unintegrated parton densities is proposed. (author)
Rao, M V S
1997-01-01
Ultrahigh energy cosmic rays carry information about their sources and the intervening medium apart from providing a beam of particles for studying certain features of high energy interactions currently inaccessible at man-made accelerators. They can at present be studied only via the extensive air showers (EAS's) they generate while passing through the Earth's atmosphere, since their fluxes are too low for the experiments of limited capability flown in balloons and satellites. The EAS is generated by a series of interactions of the primary cosmic ray and its progeny with the atmospheric nucle
Electromagnetic shower counter
CERN PhotoLab
1974-01-01
The octogonal block of lead glass is observed by eight photomultiplier tubes. Four or five such counters, arranged in succession, are used on each arm of the bispectrometer in order to detect heavy particles of the same family as those recently observed at Brookhaven and SLAC. They provide a means of identifying electrons. The arrangement of eight lateral photomultiplier tubes offers an efficient means of collecting the photons produced in the showers and determining, with a high resolution, the energy of the incident electrons. The total width at half-height is less than 6.9% for electrons having an energy of 1 GeV.
Parton distributions with threshold resummation
Bonvini, Marco; Rojo, Juan; Rottoli, Luca; Ubiali, Maria; Ball, Richard D.; Bertone, Valerio; Carrazza, Stefano; Hartland, Nathan P.
2015-01-01
We construct a set of parton distribution functions (PDFs) in which fixed-order NLO and NNLO calculations are supplemented with soft-gluon (threshold) resummation up to NLL and NNLL accuracy respectively, suitable for use in conjunction with any QCD calculation in which threshold resummation is included at the level of partonic cross sections. These resummed PDF sets, based on the NNPDF3.0 analysis, are extracted from deep-inelastic scattering, Drell-Yan, and top quark pair production data, for which resummed calculations can be consistently used. We find that, close to threshold, the inclusion of resummed PDFs can partially compensate the enhancement in resummed matrix elements, leading to resummed hadronic cross-sections closer to the fixed-order calculation. On the other hand, far from threshold, resummed PDFs reduce to their fixed-order counterparts. Our results demonstrate the need for a consistent use of resummed PDFs in resummed calculations.
Parton distributions with LHC data
DEFF Research Database (Denmark)
Ball, R.D.; Deans, C.S.; Del Debbio, L.
2013-01-01
We present the first determination of parton distributions of the nucleon at NLO and NNLO based on a global data set which includes LHC data: NNPDF2.3. Our data set includes, besides the deep inelastic, Drell-Yan, gauge boson production and jet data already used in previous global PDF determinati......We present the first determination of parton distributions of the nucleon at NLO and NNLO based on a global data set which includes LHC data: NNPDF2.3. Our data set includes, besides the deep inelastic, Drell-Yan, gauge boson production and jet data already used in previous global PDF...... fraction of the proton. We also present collider PDF sets, constructed using only data from HERA, the Tevatron and the LHC, but find that this data set is neither precise nor complete enough for a competitive PDF determination....
Review of Parton Recombination Models
International Nuclear Information System (INIS)
Bass, Steffen A
2006-01-01
Parton recombination models have been very successful in explaining data taken at RHIC on hadron spectra and emission patterns in Au+Au collisions at transverse momenta above 2 GeV/c, which have exhibited features which could not be understood in the framework of basic perturbative QCD. In this article I will review the current status on recombination models and outline which future challenges need to be addressed by this class of models
Structure functions and parton distributions
International Nuclear Information System (INIS)
Martin, A.D.; Stirling, W.J.; Roberts, R.G.
1995-01-01
The MRS parton distribution analysis is described. The latest sets are shown to give an excellent description of a wide range of deep-inelastic and other hard scattering data. Two important theoretical issues-the behavior of the distributions at small x and the flavor structure of the quark sea-are discussed in detail. A comparison with the new structure function data from HERA is made, and the outlook for the future is discussed
Meteor showers an annotated catalog
Kronk, Gary W
2014-01-01
Meteor showers are among the most spectacular celestial events that may be observed by the naked eye, and have been the object of fascination throughout human history. In “Meteor Showers: An Annotated Catalog,” the interested observer can access detailed research on over 100 annual and periodic meteor streams in order to capitalize on these majestic spectacles. Each meteor shower entry includes details of their discovery, important observations and orbits, and gives a full picture of duration, location in the sky, and expected hourly rates. Armed with a fuller understanding, the amateur observer can better view and appreciate the shower of their choice. The original book, published in 1988, has been updated with over 25 years of research in this new and improved edition. Almost every meteor shower study is expanded, with some original minor showers being dropped while new ones are added. The book also includes breakthroughs in the study of meteor showers, such as accurate predictions of outbursts as well ...
International Nuclear Information System (INIS)
2008-01-01
Full text: Sunshine and light showers are forecast for the Oscar winning actor Cate Blanchett as she increasingly greens her lifestyle. She is installing solar panels to power her Sydney home and has cut her showers back to a maximum of four minutes to help save water in drought-stricken Australia. And that is only a beginning, for she is also greening her main place of work, is campaigning on solar power and climate change, and has committed to other changes in her life to save energy and water. Blanchett - who sprang to fame in the title role of the film Elisabeth ten years ago - learned conservation when growing up in Melbourne in the 1970s from her grandmother who had lived through the Great Depression and, as a result, insisted in recycling and on letting nothing go to waste. She grew up to win an Oscar for her role in Martin Scorsese's The Aviator, amid a host of other top awards, and was spurred into environmental activism by reading about her country's growing water crisis. She says: 'As I see it, there is no greater challenge we face as a species than dealing with climate change and its effects. I care about it because of my children. I want to safeguard their future. It is an inescapable problem, but also provides us with an opportunity to change for the better. To change the way we consume, the way we think, and the way we behave. By assuming responsibility, we protect and respect the generations behind us.' Together with her husband, playwright Andrew Upton, she has started by setting out to 'greenovate' their home: powering it with solar energy, using natural air flows rather than air conditioning to cool it, and recycling grey water. The couple also plan to extend the improvements to the Sydney Theatre Company, where they are joint artistic directors, with the aim of running off-grid for a whole season. 'I really love a refreshing shower,' she says, but has installed a timer to stop them after four minutes. Indeed she tries to make them even shorter
New meteor showers – yes or not?
Koukal, Jakub
2018-01-01
The development of meteor astronomy associated with the development of CCD technology is reflected in a huge increase in databases of meteor orbits. It has never been possible before in the history of meteor astronomy to examine properties of meteors or meteor showers. Existing methods for detecting new meteor showers seem to be inadequate in these circumstances. The spontaneous discovery of new meteor showers leads to ambiguous specifications of new meteor showers. There is a duplication of already discovered meteor showers and a division of existing meteor showers based on their own criteria. The analysis in this article considers some new meteor showers in the IAU MDC database.
Multi-parton interactions at the LHC
Energy Technology Data Exchange (ETDEWEB)
Kulesza, A. [RWTH Aachen (Germany). Inst. fuer Theoretische Teilchenphysik und Kosmologie; Nagy, Z. (eds.) [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)
2011-11-15
We review the recent progress in the theoretical description and experimental observation of multiple parton interactions. Subjects covered include experimental measurements of minimum bias interactions and of the underlying event, models of soft physics implemented in Monte Carlo generators, developments in the theoretical description of multiple parton interactions and phenomenological studies of double parton scattering. This article stems from contributions presented at the Helmholtz Alliance workshop on ''Multi-Parton Interactions at the LHC'', DESY Hamburg, 13-15 September 2010. (orig.)
Framework for evolution in double parton scattering
Energy Technology Data Exchange (ETDEWEB)
Buffing, Maarten G.A.
2017-07-15
Double parton scattering (DPS) describes two colliding hadrons having interactions in the form of two hard processes, each initiated by a separate pair of partons. Just as for single parton scattering, the resummation of soft gluon exchange gives rise to a soft function, which is a necessary ingredient for obtaining rapidity evolution equations. For various regions of phase space, we derive the rapidity evolution and the scale evolution of double transverse momentum dependent parton distribution functions (DTMDs) as well as of the p{sub T}-resummed cross section for double Drell-Yan like processes. This contributes to a framework that can be used for phenomenological DPS studies including resummation.
Penetrating particles in horizontal air showers
International Nuclear Information System (INIS)
Wohlenberg, J.; Boehm, E.
1975-01-01
Particle density and arrival time of muons has been measured in Horizontal Air Showers. 5,600 showers have been recorded in 7,800 hours. Using stringent selection criteria 155 showers have been found horizontal (zenith angle larger 70 0 ) in the size range 4.1 > lg N > 5.5. The muons observed in these showers can be explained by purely electromagnetic origin of horizontal showers. (orig.) [de
Multiple Parton Interactions in ALICE
CERN. Geneva
2013-01-01
We will present in detail the measurement of the charged particle multiplicity dependence of per-trigger pair yields in azimuthal direction induced by low-energetic di-jets produced in proton-proton collisions. Using two-particle angular correlations with low transverse momentum thresholds, jet properties are measured on a statistical basis down to the lowest possible jet energies. The analysis can give information about the contribution from multiple parton interactions to particle production. Moreover, the results allow to optimize the parametrization of the jet fragmentation in phenomenological mode...
Parton Distribution Benchmarking with LHC Data
Ball, Richard D.; Carrazza, Stefano; Debbio, Luigi Del; Forte, Stefano; Gao, Jun; Hartland, Nathan; Huston, Joey; Nadolsky, Pavel; Rojo, Juan; Stump, Daniel; Thorne, Robert S.; Yuan, C. -P.
2012-01-01
We present a detailed comparison of the most recent sets of NNLO PDFs from the ABM, CT, HERAPDF, MSTW and NNPDF collaborations. We compare parton distributions at low and high scales and parton luminosities relevant for LHC phenomenology. We study the PDF dependence of LHC benchmark inclusive cross
The neural network approach to parton fitting
International Nuclear Information System (INIS)
Rojo, Joan; Latorre, Jose I.; Del Debbio, Luigi; Forte, Stefano; Piccione, Andrea
2005-01-01
We introduce the neural network approach to global fits of parton distribution functions. First we review previous work on unbiased parametrizations of deep-inelastic structure functions with faithful estimation of their uncertainties, and then we summarize the current status of neural network parton distribution fits
Parton-parton scattering at two-loops
International Nuclear Information System (INIS)
Tejeda Yeomans, M.E.
2001-01-01
Abstract We present an algorithm for the calculation of scalar and tensor one- and two-loop integrals that contribute to the virtual corrections of 2 → 2 partonic scattering. First, the tensor integrals are related to scalar integrals that contain an irreducible propagator-like structure in the numerator. Then, we use Integration by Parts and Lorentz Invariance recurrence relations to build a general system of equations that enables the reduction of any scalar integral (with and without structure in the numerator) to a basis set of master integrals. Their expansions in ε = 2 - D/2 have already been calculated and we present a summary of the techniques that have been used to this end, as well as a compilation of the expansions we need in the different physical regions. We then apply this algorithm to the direct evaluation of the Feynman diagrams contributing to the O(α s 4 ) one- and two-loop matrix-elements for massless like and unlike quark-quark, quark-gluon and gluon-gluon scattering. The analytic expressions we provide are regularised in Convensional Dimensional Regularisation and renormalised in the MS-bar scheme. Finally, we show that the structure of the infrared divergences agrees with that predicted by the application of Catani's formalism to the analysis of each partonic scattering process. The results presented in this thesis provide the complete calculation of the one- and two-loop matrix-elements for 2 → 2 processes needed for the next-to-next-to-leading order contribution to inclusive jet production at hadron colliders. (author)
The ATLAS collaboration
2016-01-01
We present a new tune of the Pythia8 event generator, titled ``A3'' and suitable for inclusive QCD modelling, including minimum bias physics and pile-up overlay. The tuning uses the early Run~2 charged particle distribution and inelastic cross section results from ATLAS in addition to the Run~1 data used to construct previous minimum-bias tunes. For the first time, the tuning included a consideration of diffraction modelling parameters and a diffractive model other than the Pythia8 default is used in the final configuration. That resulted in a better descriptions of the measured inelastic cross-sections, and similar or better level of agreement compared to the currently used A2 tune for other distributions considered.
Chekanov, Sergei; Fischer, Andrew; Zhang, Jinlong
2017-01-01
This paper describes the effect of PYTHIA8 tunes on event simulation of e$^+$e$^-$ collisions with center-of-mass (CM) energies of 380 GeV and 3 TeV at the proposed CLIC collider. Event shapes, such as thrust, thrust major, thrust minor, oblateness, as well as particle multiplicities have been analyzed and relative differences with respect to the default PYTHIA8 tune were determined. The effect of tunes on top-mass reconstruction in the resolved and boosted regimes was analyzed. No statistically significant variation for reconstructed top masses using invariant masses of three jets was found for events with a CM energy of 380 GeV. For the fully boosted top reconstruction at a CM energy of 3 TeV, a significant shift in reconstructed top mass of about 700 MeV for the "Montull" tune was observed. This shift correlates with an increase in particle multiplicity compared to all other PYTHIA8 tunes.
Signatures of parton exogamy in e+e- → W+W- → hadrons
Ellis, John; Geiger, Klaus
1997-02-01
We propose possible signatures of ‘exogamous’ combinations between partons in the different W+ and W- hadron showers in e+e- → W+W- events with purely hadronic final states. Within the space-time model for hadronic shower development that we have proposed previously, we find a possible difference of about 10% between the mean hadronic multiplicity in such purely hadronic final states and twice the hadronic multiplicity in events in which one W± decays hadronically and the other leptonically, i.e., « Nhad(2 W ≠ 2« Nhad( W), associated with the formation of hadronic clusters by ‘exogamous’ pairs of partons. We discuss the dependence of this possible difference in multiplicity on the center-of-mass energy, on the hadron momenta, and on the angular separation between the W± dijets. If it were observed, any such multiplicity difference would indicate that the W± do not hadronize independently, and hence raise questions about the accuracy with which the W± mass could be determined from purely hadronic final states.
Studies on muon showers underground
Energy Technology Data Exchange (ETDEWEB)
Bergamasco, L; Castagnoli, C; Dardo, M; D' Ettorre Piazzoli, B; Mannocchi, G [Consiglio Nazionale delle Ricerche, Turin (Italy). Lab. di Cosmo-Geofisica; Picchi, P; Visentin, R [Comitato Nazionale per l' Energia Nucleare, Frascati (Italy). Laboratori Nazionali di Frascati; Sitte, K [Freiburg Univ. (Germany, F.R.). Fakultaet fuer Physik
1976-08-21
The 4 m/sup 2/ spark chamber telescope array of the Mt. Cappuccini Laboratory, Torino, At 40 m w.e. underground was operated for about 830 h recording muon showers. The data were analysed with respect to the multiplicity distribution of the shower particles, and to local interactions initiated in the chamber absorbers. Regarding the multiplicity analysis a semi-empirical expression for the likely shower size dependence of a structure function of the analytical form proposed by Vernov et al., was derived and applied with systematically varied parameters. The comparison of the observed rates of multiples with those calculated with a variety of parameters showed that a satisfactory agreement can be attained only if one admits a variation with the shower size of the parameters, and an enhanced muon/electron ratio at the lower primary energies, possibly indicative of an increased abundance of primary heavy nuclei. This would conform with the idea of a two-component primary composition in which a pulsar-produced fraction, enriched in heavy nuclei, dominated only at medium energies. The records on multiplicative interactions, and on large-angle scattering, were analysed by comparing their rates observed for shower particles with those found in single-muon check runs. The results are consistent with the assumption that all shower particle interactions are electromagnetic in nature, and that nonconventional components like mandelas are absent. Only making extreme allowances for statistical fluctuations the data can be made compatible with a mandela flux as large as that suggested by Baruch et al., provided that the mandela attenuation length is less than 1 500g/cm/sup 2/ of rock.
Studies on muon showers underground
International Nuclear Information System (INIS)
Bergamasco, L.; Castagnoli, C.; Dardo, M.; D'Ettorre Piazzoli, B.; Mannocchi, G.; Picchi, P.; Visentin, R.; Sitte, K.
1976-01-01
The 4 m 2 spark chamber telescope array of the Mt. Cappuccini Laboratory, Torino, At 40 m w.e. underground was operated for about 830 h recording muon showers. The data were analysed with respect to the multiplicity distribution of the shower particles, adn to local interactions initiated in the chamber absorbers. Regarding the multiplicity analysis a semi-empirical expression for the likely shower size dependence of a structure function of the analytical form proposed by Vernov et al., was derived and applied with systematically varied parameters. The comparison of the observed rates of multiples with those calculated with a variety of parameters showed that a satisfactory agreement can be attained only if one admits a variation with the shower size of the parameters, and an enhanced muon/electron ratio at the lower primary energies, possibly indicative of an increased abundance of primary heavy nuclei. This would conform with the idea of a two-component primary composition in which a pulsar-produced fraction, enriched in heavy nuclei, dominated only at medium energies. The records on multiplicative interactions, and on large-angle scattering, were analysed by comparing their rates observed for shower particles with those found in single-muon check runs. The results are consistent with the assumption that all shower particle interactions are electromagnetic in nature, and that nonconventional components like mandelas are absent. Only making extreme allowances for statistical fluctuations the data can be made compatible with a mandela flux as large as that suggested by Baruch et al., provided that the mandela attenuation length is less than 1 500g/cm 2 of rock
Gregor, Ivan; Dröge, Johannes; Schirmer, Melanie; Quince, Christopher; McHardy, Alice C
2016-01-01
Background. Metagenomics is an approach for characterizing environmental microbial communities in situ, it allows their functional and taxonomic characterization and to recover sequences from uncultured taxa. This is often achieved by a combination of sequence assembly and binning, where sequences are grouped into 'bins' representing taxa of the underlying microbial community. Assignment to low-ranking taxonomic bins is an important challenge for binning methods as is scalability to Gb-sized datasets generated with deep sequencing techniques. One of the best available methods for species bins recovery from deep-branching phyla is the expert-trained PhyloPythiaS package, where a human expert decides on the taxa to incorporate in the model and identifies 'training' sequences based on marker genes directly from the sample. Due to the manual effort involved, this approach does not scale to multiple metagenome samples and requires substantial expertise, which researchers who are new to the area do not have. Results. We have developed PhyloPythiaS+, a successor to our PhyloPythia(S) software. The new (+) component performs the work previously done by the human expert. PhyloPythiaS+ also includes a new k-mer counting algorithm, which accelerated the simultaneous counting of 4-6-mers used for taxonomic binning 100-fold and reduced the overall execution time of the software by a factor of three. Our software allows to analyze Gb-sized metagenomes with inexpensive hardware, and to recover species or genera-level bins with low error rates in a fully automated fashion. PhyloPythiaS+ was compared to MEGAN, taxator-tk, Kraken and the generic PhyloPythiaS model. The results showed that PhyloPythiaS+ performs especially well for samples originating from novel environments in comparison to the other methods. Availability. PhyloPythiaS+ in a virtual machine is available for installation under Windows, Unix systems or OS X on: https://github.com/algbioi/ppsp/wiki.
Electron shower transverse profile measurement
International Nuclear Information System (INIS)
Lednev, A.A.
1993-01-01
A method to measure the shower transverse profile is described. Calibration data of the lead-glass spectrometer GAMS collected in a wide electron beam without any additional coordinate detector are used. The method may be used for the measurements in both cellular- and projective-type spectrometers. The results of measuring the 10 GeV electron shower profile in the GAMS spectrometer, without optical grease between the lead-glass radiators and photomultipliers, are approximated with an analytical function. The estimate of the coordinate accuracy is obtained. 5 refs., 8 figs
Endpoint singularities in unintegrated parton distributions
Hautmann, F
2007-01-01
We examine the singular behavior from the endpoint region x -> 1 in parton distributions unintegrated in both longitudinal and transverse momenta. We identify and regularize the singularities by using the subtraction method, and compare this with the cut-off regularization method. The counterterms for the distributions with subtractive regularization are given in coordinate space by compact all-order expressions in terms of eikonal-line operators. We carry out an explicit calculation at one loop for the unintegrated quark distribution. We discuss the relation of the unintegrated parton distributions in subtractive regularization with the ordinary parton distributions.
Photons in a partonic transport approach
Energy Technology Data Exchange (ETDEWEB)
Greif, Moritz; Senzel, Florian; Greiner, Carsten [Goethe Universitaet Frankfurt, Max-von-Laue-Str. 1 60438 Frankfurt am Main (Germany)
2015-07-01
Partonic transport approaches have proved to be valuable tools in describing the quark-gluon plasma, created in heavy-ion collisions. In this work, first steps towards a dynamical understanding of photonproduction in expanding heavy-ion collisions are presented. Several photon production processes are included in the partonic cascade BAMPS (Boltzmann Approach to Multi-Parton Scatterings). BAMPS provides a microscopic tool to study expanding fireballs, employing a stochastic method to solve the relativistic 3+1d Boltzmann equation. Subsequently, photon spectra can be investigated, and in particular, the influence of the quark-gluon plasma phase for the elliptic flow of photons is studied.
Eikonal propagators and high-energy parton-parton scattering in gauge theories
International Nuclear Information System (INIS)
Meggiolaro, Enrico
2001-01-01
In this paper we consider 'soft' high-energy parton-parton scattering processes in gauge theories, i.e., elastic scattering processes involving partons at very high squared energies s in the center of mass and small squared transferred momentum t (s→∞, t 2 ). By a direct resummation of perturbation theory in the limit we are considering, we derive expressions for the truncated-connected quark (antiquark) propagator in an external gluon field, as well as for the residue at the pole of the full unrenormalized propagator, both for scalar and fermion gauge theories. These are the basic ingredients to derive high-energy parton-parton scattering amplitudes, using the LSZ reduction formulae and a functional integral approach. The above procedure is also extended to include the case in which at least one of the partons is a gluon. The meaning and the validity of the results are discussed
Parton distributions beyond the leading order
International Nuclear Information System (INIS)
Chyla, J.
1993-01-01
The importance of properly taking into account the factorization scheme dependence of parton distribution functions is emphasized. A serious error in the usual handling of this topic is pointed out and the correct procedure for transforming parton distribution functions from one factorization scheme to another recalled. It is shown that the conventional M bar S and DIS definitions thereof are ill defined due to the lack of distinction between the factorization scheme dependence of parton distribution functions and renormalization scheme dependence of the strong coupling constant α s . A novel definition of parton distribution functions is suggested and its role in the construction of consistent next-to-leading-order event generators briefly outlined
Pre-equilibrium parton dynamics: Proceedings
Energy Technology Data Exchange (ETDEWEB)
Wang, Xin-Nian [ed.
1993-12-31
This report contains papers on the following topics: parton production and evolution; QCD transport theory; interference in the medium; QCD and phase transition; and future heavy ion experiments. This papers have been indexed separately elsewhere on the data base.
Pre-equilibrium parton dynamics: Proceedings
International Nuclear Information System (INIS)
Wang, Xin-Nian
1993-01-01
This report contains papers on the following topics: parton production and evolution; QCD transport theory; interference in the medium; QCD and phase transition; and future heavy ion experiments. This papers have been indexed separately elsewhere on the data base
Unraveling hadron structure with generalized parton distributions
Energy Technology Data Exchange (ETDEWEB)
Andrei Belitsky; Anatoly Radyushkin
2004-10-01
The recently introduced generalized parton distributions have emerged as a universal tool to describe hadrons in terms of quark and gluonic degrees of freedom. They combine the features of form factors, parton densities and distribution amplitudes - the functions used for a long time in studies of hadronic structure. Generalized parton distributions are analogous to the phase-space Wigner quasi-probability function of non-relativistic quantum mechanics which encodes full information on a quantum-mechanical system. We give an extensive review of main achievements in the development of this formalism. We discuss physical interpretation and basic properties of generalized parton distributions, their modeling and QCD evolution in the leading and next-to-leading orders. We describe how these functions enter a wide class of exclusive reactions, such as electro- and photo-production of photons, lepton pairs, or mesons.
Partons and their applications at high energies
International Nuclear Information System (INIS)
Drell, Sidney D.; Yan, Tung-Mow
2000-01-01
We discuss Feynman's parton model for deep inelastic weak or electromagnetic processes as an application of the impulse approximation to elementary particle interactions. The special features and conditions permitting this application are elaborated upon in some detail including the dependence of the parton model and the impulse treatment on an appropriate choice of coordinate frames and the role of the very soft or wee partons. Application of the parton model is made to the calculation of the cross section for massive lepton pair production in very high energy hadron-hadron collisions and compared with experiment. The conjectured role of light cone singularities in describing this and the other deep inelastic amplitudes is also discussed. (c) 2000 Academic Press, Inc
Calculation of the TeV prompt muon component in very high energy cosmic ray showers
International Nuclear Information System (INIS)
Battistoni, G.; Bloise, C.; Forti, C.; Tanzini, A.
1995-07-01
HEMAS-DPM is a Monte Carlo for the simulation of very high energy cosmic ray showers, which includes the DPMJET-II code based on the two component Dual Parton Model. DPMJET-II provides also charm production in agreement with data and, for p exceeding 5 GeV/c, with perturbative QCD results in hadron-nucleus and nucleus-nucleus interactions. In this respect, a new scheme has been considered for the inclusive production of D mesons at large p in hadronic collisions in the frame work of perturbative fragmentation functions, allowing an analysis at the NLO (next to leading order) level which goes beyond the fixed O(α s 3 ) perturbative theory of open charm production. HEMAS-DPM has been applied to the calculation of the prompt muon component for E μ ≥1 TeV in air showers considering the two extreme cases of primary protons and Fe nuclei
Air shower measurements with LOFAR
Horneffer, A.; Bähren, L.; Buitink, S.; Falcke, H.; Hörandel, J.R.; Kuijpers, J.; Lafebre, S.; Nigl, A.; Scholten, O.; Singh, K.
2009-01-01
Air showers from cosmic rays emit short, intense radio pulses. The Low Frequency Array (LOFAR) is a new radio telescope, that is being built in the Netherlands and Europe. Designed primarily as a radio interferometer, the core of LOFAR will have a high density of radio antennas, which will be
Color correlations in parton jet decay
International Nuclear Information System (INIS)
Levin, E.M.; Ryskin, M.G.
1983-01-01
The pre-confinement effect is discussed. Colour correlations are calculated for the decays of parton jets with account for the coherence of the gluon interaction. It is shown that, in contrast to the results of previous works, the colour correlations between two gluons with a high pair mass can be appreciable. In any kinematical interval, however, the energy carried away be the particles correlated in the colour is always much less than the total energy carried away by the partons
Results on reuse of reclaimed shower water
Verostko, Charles E.; Garcia, Rafael; Pierson, Duane L.; Reysa, Richard P.; Irbe, Robert
1986-01-01
The Waste Water Recovery System that has been used in conjunction with a microgravity whole body shower to test a closed loop shower water reclamation system applicable to the NASA Space Station employs a Thermoelectric Integrated Hollow Fiber Membrane Evaporation Subsystem. Attention is given to the suitability of a Space Shuttle soap for such crew showers, the effects of shower water on the entire system, and the purification qualities of the recovered water. The chemical pretreatment of the shower water for microorganism control involved activated carbon, mixed ion exchange resin beds, and iodine bactericide dispensing units. The water was recycled five times, demonstrating the feasibility of reuse.
Parton fragmentation and string dynamics
International Nuclear Information System (INIS)
Andersson, B.; Gustafson, G.; Ingelman, G.; Sjoestrand, T.
1983-01-01
While much has been learned recently about quark and gluon interactions in the framework of perturbative Quantum Chromodynamics, the relation between calculated parton properties and observed hadron densities involves models where dynamics and jet empirical rules have to be combined. The purpose of this article is to describe a presently successful approach which is based on a cascade jet model using String dynamics. It can readily lead to Monte Carlo jet programmes of great use when analyzing data. Production processes in an iterative cascade approach, with tunneling in a constant force field, are reviewed. Expected differences between quark and gluon jets are discussed. Low transverse momentum phenomena are also reviewed with emphasis on hyperon polarization. In so far as this approach uses a fragmentation scheme based on String dynamics, it was deemed appropriate to also include under the same cover a special report on the Classical theory of relativistic Strings, seen as the classical limit of the Dual Resonance model. The Equations of motion and interaction among strings are presented. (orig.)
Parton distributions with LHC data
Ball, Richard D.; Carrazza, Stefano; Deans, Christopher S.; Del Debbio, Luigi; Forte, Stefano; Guffanti, Alberto; Hartland, Nathan P.; Latorre, Jose I.; Rojo, Juan; Ubiali, Maria
2013-01-01
We present the first determination of parton distributions of the nucleon at NLO and NNLO based on a global data set which includes LHC data: NNPDF2.3. Our data set includes, besides the deep inelastic, Drell-Yan, gauge boson production and jet data already used in previous global PDF determinations, all the relevant LHC data for which experimental systematic uncertainties are currently available: ATLAS and LHCb W and Z lepton rapidity distributions from the 2010 run, CMS W electron asymmetry data from the 2011 run, and ATLAS inclusive jet cross-sections from the 2010 run. We introduce an improved implementation of the FastKernel method which allows us to fit to this extended data set, and also to adopt a more effective minimization methodology. We present the NNPDF2.3 PDF sets, and compare them to the NNPDF2.1 sets to assess the impact of the LHC data. We find that all the LHC data are broadly consistent with each other and with all the older data sets included in the fit. We present predictions for various ...
Matching NLO parton shower matrix element with exact phase space case of $W\\to l\
Nanava, G; Was, Z
2010-01-01
In practical applications PHOTOS Monte Carlo is often used for simulation of QED effects in decay of intermediate particles and resonances. Generated in such a way that samples of events cover the whole bremsstrahlung phase space. With the help of selection cuts, experimental acceptance can be then taken into account. The program is based on exact multiphoton phase space. To evaluate the program precision it is necessary to control its matrix element. Generally it is obtained using iteration of the universal multidimensional kernel. In some cases it is however obtained from the exact first order matrix element. Then, as a consequence, all terms necessary for non-leading logarithms are taken into account. In the present paper we will focus on the decays W -> l nu and gamma^* -> pi^+ pi^-. The Born level cross sections for both processes approach zero in some points of the phase space. Process dependent, compensating weight is constructed to implement exact matrix element, but it will be recommended for use onl...
Transverse nucleon structure and diagnostics of hard parton-parton processes at LHC
Energy Technology Data Exchange (ETDEWEB)
L. Frankfurt, M. Strikman, C. Weiss
2011-03-01
We propose a new method to determine at what transverse momenta particle production in high-energy pp collisions is governed by hard parton-parton processes. Using information on the transverse spatial distribution of partons obtained from hard exclusive processes in ep/\\gamma p scattering, we evaluate the impact parameter distribution of pp collisions with a hard parton-parton process as a function of p_T of the produced parton (jet). We find that the average pp impact parameters in such events depend very weakly on p_T in the range 2 < p_T < few 100 GeV, while they are much smaller than those in minimum-bias inelastic collisions. The impact parameters in turn govern the observable transverse multiplicity in such events (in the direction perpendicular to the trigger particle or jet). Measuring the transverse multiplicity as a function of p_T thus provides an effective tool for determining the minimum p_T for which a given trigger particle originates from a hard parton-parton process.
Time structure of cascade showers
International Nuclear Information System (INIS)
Nakatsuka, Takao
1984-01-01
Interesting results have been reported on the time structure of the electromagnetic components of air showers which have been obtained by using recent fast electronic circuit technology. However, these analyses and explanations seem not very persuasive. One of the reasons is that there is not satisfactory theoretical calculation yet to explain the delay of electromagnetic components in cascade processes which are the object of direct observation. Therefore, Monte Carlo calculation was attempted for examining the relationship between the altitude at which high energy γ-ray is generated up in the air and the time structure of cascade showers at the level of observation. The investigation of a dominant factor over the delay of electromagnetic components indicated that the delay due to the multiple scattering of electrons was essential. The author used the analytical solution found by himself of C. N. Yang's equation for the study on the delay due to multiple scattering. The results were as follows: The average delay time and the spread of distribution of electromagnetic cascades were approximately in linear relationship with the mass of a material having passed in a thin uniform medium; the rise time of arrival time distribution for electromagnetic cascade showers was very steep under the condition that they were generated up in the air and observed on the ground; the subpeaks delayed by tens of ns in arrival time may sometimes appear due to the perturbation in electromagnetic cascade processes. (Wakatsuki, Y.)
Evolution of parton densities beyond leading order
International Nuclear Information System (INIS)
Curci, G.; Petronzio, R.; Furmanski, W.
1980-01-01
We develop a technique, based explicitly on the factorization properties of mass singularities, which allows one to calculate the evolution of parton densities beyond leading order. We present the results for the evolution of hadronic structure functions as well as for parton fragmentation functions into hadrons. Within our scheme the predictions for a particular process are obtained by convoluting a universal parton density with a short-distance cross section specific to the process. As an application, we calculate the QCD predictions for the Q 2 dependence of deep inelastic lepton-hadron scattering and of one-particle inclusive e + e - annihilation cross sections. Our results for electroproduction agree with those obtained with the operator product expansion technique. Physical quantitites in scattering are related to the corresponding ones in annihilation by analytic continuation, whereas the Gribov-Lipatov relation is strongly violated. (orig.)
Nucleon parton distributions in chiral perturbation theory
International Nuclear Information System (INIS)
Moiseeva, Alena
2013-01-01
Properties of the chiral expansion of nucleon light-cone operators have been studied. In the framework of the chiral perturbation theory we have demonstrated that convergency of the chiral expansion of nucleon parton distributions strongly depends on the value of the variable x. Three regions in x with essentially different analytical properties of the resulting chiral expansion for parton distributions were found. For each of the regions we have elaborated special power counting rules corresponding to the partial resummation of the chiral series. The nonlocal effective operators for the vector and the axial nucleon parton distributions have been constructed at the zeroth and the first chiral order. Using the derived nonlocal operators and the derived power counting rules we have obtained the second order expressions for the nucleon GPDs H(x,ξ,Δ 2 ), H(x,ξ,Δ 2 ),E(x,ξ,Δ 2 ) valid in the region x>or similar a 2 χ .
Radar reflection off extensive air showers
Stasielak, J; Bertaina, M; Blümer, J; Chiavassa, A; Engel, R; Haungs, A; Huege, T; Kampert, K -H; Klages, H; Kleifges, M; Krömer, O; Ludwig, M; Mathys, S; Neunteufel, P; Pekala, J; Rautenberg, J; Riegel, M; Roth, M; Salamida, F; Schieler, H; Šmída, R; Unger, M; Weber, M; Werner, F; Wilczyński, H; Wochele, J
2012-01-01
We investigate the possibility of detecting extensive air showers by the radar technique. Considering a bistatic radar system and different shower geometries, we simulate reflection of radio waves off the static plasma produced by the shower in the air. Using the Thomson cross-section for radio wave reflection, we obtain the time evolution of the signal received by the antennas. The frequency upshift of the radar echo and the power received are studied to verify the feasibility of the radar detection technique.
Monte-Carlo simulation of electromagnetic showers
International Nuclear Information System (INIS)
Amatuni, Ts.A.
1984-01-01
The universal ELSS-1 program for Monte Carlo simulation of high energy electromagnetic showers in homogeneous absorbers of arbitrary geometry is written. The major processes and effects of electron and photon interaction with matter, particularly the Landau-Pomeranchuk-Migdal effect, are taken into account in the simulation procedures. The simulation results are compared with experimental data. Some characteristics of shower detectors and electromagnetic showers for energies up 1 TeV are calculated
Parton Propagation and Fragmentation in QCD Matter
Energy Technology Data Exchange (ETDEWEB)
Alberto Accardi, Francois Arleo, William Brooks, David D' Enterria, Valeria Muccifora
2009-12-01
We review recent progress in the study of parton propagation, interaction and fragmentation in both cold and hot strongly interacting matter. Experimental highlights on high-energy hadron production in deep inelastic lepton-nucleus scattering, proton-nucleus and heavy-ion collisions, as well as Drell-Yan processes in hadron-nucleus collisions are presented. The existing theoretical frameworks for describing the in-medium interaction of energetic partons and the space-time evolution of their fragmentation into hadrons are discussed and confronted to experimental data. We conclude with a list of theoretical and experimental open issues, and a brief description of future relevant experiments and facilities.
Improved modelling of independent parton hadronization
International Nuclear Information System (INIS)
Biddulph, P.; Thompson, G.
1989-01-01
A modification is proposed to current versions of the Field-Feynman ansatz for the hadronization of a quark in Monte Carlo models of QCD interactions. This faster-running algorithm has no more parameters and imposes a better degree of energy conservation. It results in naturally introducing a limitation of the transverse momentum distribution, similar to the experimentally observed ''seagull'' effect. There is now a much improved conservation of quantum numbers between the original parton and resultant hadrons, and the momentum of the emitted parton is better preserved in the summed momentum vectors of the final state particles. (orig.)
Positivity bounds on double parton distributions
International Nuclear Information System (INIS)
Diehl, Markus; Kasemets, Tomas
2013-03-01
Double hard scattering in proton-proton collisions is described in terms of double parton distributions. We derive bounds on these distributions that follow from their interpretation as probability densities, taking into account all possible spin correlations between two partons in an unpolarized proton. These bounds constrain the size of the polarized distributions and can for instance be used to set upper limits on the effects of spin correlations in double hard scattering. We show that the bounds are stable under leading-order DGLAP evolution to higher scales.
Partons and the EMC spin effect
International Nuclear Information System (INIS)
Bass, S.D.
1992-03-01
We focus on the patron model and the role of the axial anomaly in polarised deep inelastic scattering. We show that the axial anomaly is relevant to each of the higher moments of the spin dependent structure function g 1 (x) and not just the first moment. This result implies that the factorisation of mass singularities is not sufficient to define the parton model in spin dependent quantum chromodynamics (QCD). (It is certainly a necessary condition.) We also need to consider the locality of the photon parton interaction. The anomaly is observed over all x in the (EMC)g 1 (x) data. (author)
Complex conjugate poles and parton distributions
International Nuclear Information System (INIS)
Tiburzi, B.C.; Detmold, W.; Miller, G.A.
2003-01-01
We calculate parton and generalized parton distributions in Minkowski space using a scalar propagator with a pair of complex conjugate poles. Correct spectral and support properties are obtained only after careful analytic continuation from Euclidean space. Alternately the quark distribution function can be calculated from modified cutting rules, which put the intermediate state on its complex mass shells. Distribution functions agree with those resulting from the model's Euclidean space double distribution which we calculate via nondiagonal matrix elements of twist-two operators. Thus one can use a wide class of analytic parametrizations of the quark propagator to connect Euclidean space Green functions to light-cone dominated amplitudes
Shower maximum detector for SDC calorimetry
International Nuclear Information System (INIS)
Ernwein, J.
1994-01-01
A prototype for the SDC end-cap (EM) calorimeter complete with a pre-shower and a shower maximum detector was tested in beams of electrons and Π's at CERN by an SDC subsystem group. The prototype was manufactured from scintillator tiles and strips read out with 1 mm diameter wave-length shifting fibers. The design and construction of the shower maximum detector is described, and results of laboratory tests on light yield and performance of the scintillator-fiber system are given. Preliminary results on energy and position measurements with the shower max detector in the test beam are shown. (authors). 4 refs., 5 figs
Fast shower simulation in the ATLAS calorimeter
International Nuclear Information System (INIS)
Barberio, E; Boudreau, J; Mueller, J; Tsulaia, V; Butler, B; Young, C C; Cheung, S L; Savard, P; Dell'Acqua, A; Simone, A D; Gallas, M V; Ehrenfeld, W; Glazov, A; Placakyte, R; Marshall, Z; Rimoldi, A; Waugh, A
2008-01-01
The time to simulate pp collisions in the ATLAS detector is largely dominated by the showering of electromagnetic particles in the heavy parts of the detector, especially the electromagnetic barrel and endcap calorimeters. Two procedures have been developed to accelerate the processing time of electromagnetic particles in these regions: (1) a fast shower parameterisation and (2) a frozen shower library. Both work by generating the response of the calorimeter to electrons and positrons with Geant 4, and then reintroduce the response into the simulation at runtime. In the fast shower parameterisation technique, a parameterisation is tuned to single electrons and used later by simulation. In the frozen shower technique, actual showers from low-energy particles are used in the simulation. Full Geant 4 simulation is used to develop showers down to ∼ 1GeV, at which point the shower is terminated by substituting a frozen shower. Judicious use of both techniques over the entire electromagnetic portion of the ATLAS calorimeter produces an important improvement of CPU time. We discuss the algorithms and their performance in this paper
Partons and quarks. Daresbury lecture note series No. 12
Energy Technology Data Exchange (ETDEWEB)
Close, F. E.
1973-04-15
The report is based on a series of lectures given at Daresbury Laboratory on 2 to 12 Apri1 1973. It is stated that the purpose was to show the reasons why parton models describe the data, show what other phenomena can be understood and what predictions can be made within the parton hypothesis. The report is in sections: elastic electron scattering; inelastic electron scattering; deep inelastic scattering and partons; structure functions and surn rules in the quark parton model; inelastic neutrinto scattering; forward Compton scattering; Compton scattering in simple models; a J = 0 fixed pole in Compton scattering; the non-perturbative parton model without tears; the parton model and vector-meson dominance-rivals or partners; do resonances scale; resonances, SU(6) and the quark parton model; towards a dynamical parton model. (UK)
Directory of Open Access Journals (Sweden)
Ivan Gregor
2016-02-01
Full Text Available Background. Metagenomics is an approach for characterizing environmental microbial communities in situ, it allows their functional and taxonomic characterization and to recover sequences from uncultured taxa. This is often achieved by a combination of sequence assembly and binning, where sequences are grouped into ‘bins’ representing taxa of the underlying microbial community. Assignment to low-ranking taxonomic bins is an important challenge for binning methods as is scalability to Gb-sized datasets generated with deep sequencing techniques. One of the best available methods for species bins recovery from deep-branching phyla is the expert-trained PhyloPythiaS package, where a human expert decides on the taxa to incorporate in the model and identifies ‘training’ sequences based on marker genes directly from the sample. Due to the manual effort involved, this approach does not scale to multiple metagenome samples and requires substantial expertise, which researchers who are new to the area do not have. Results. We have developed PhyloPythiaS+, a successor to our PhyloPythia(S software. The new (+ component performs the work previously done by the human expert. PhyloPythiaS+ also includes a new k-mer counting algorithm, which accelerated the simultaneous counting of 4–6-mers used for taxonomic binning 100-fold and reduced the overall execution time of the software by a factor of three. Our software allows to analyze Gb-sized metagenomes with inexpensive hardware, and to recover species or genera-level bins with low error rates in a fully automated fashion. PhyloPythiaS+ was compared to MEGAN, taxator-tk, Kraken and the generic PhyloPythiaS model. The results showed that PhyloPythiaS+ performs especially well for samples originating from novel environments in comparison to the other methods. Availability. PhyloPythiaS+ in a virtual machine is available for installation under Windows, Unix systems or OS X on: https://github.com/algbioi/ppsp/wiki.
Constraints on parton density functions from D0
Energy Technology Data Exchange (ETDEWEB)
Hays, Jonathan M.; /Imperial Coll., London
2008-04-01
Five recent results from D0 which either impact or have the potential to impact on uncertainties in parton density functions are presented. Many analyses at D0 are sensitive to the modeling of the partonic structure of the proton. When theoretical and experimental uncertainties are well controlled there exists the possibility for additional constraints on parton density functions (PDF). Five measurements are presented which either have already been included in global parton fits or have the potential to contribute in the future.
The ultimate air shower observatory
International Nuclear Information System (INIS)
Jones, L.W.
1981-01-01
The possibility of constructing an international air shower observatory in the Himalayas is explored. A site at about 6500 m elevation (450 g/cm 2 ) would provide more definitive measurements of composition and early interaction properties of primaries above 10 16 eV than can be achieved with existing arrays. By supplementing a surface array with a Fly's Eye and muon detectors, information on the highest energy cosmic rays may be gained which is not possible in any other way. Potential sites, technical aspects, and logistical problems are explored
Collinear and transverse momentum dependent parton densities obtained with a parton branching method
Energy Technology Data Exchange (ETDEWEB)
Lelek, Aleksandra
2017-10-15
We present a solution of the DGLAP evolution equations, written in terms of Sudakov form factors to describe the branching and no-branching probabilities, using a parton branching Monte Carlo method. We demonstrate numerically that this method reproduces the semi-analytical solutions. We show how this method can be used to determine Transverse Momentum Dependent (TMD) parton distribution functions, in addition to the usual integrated parton distributions functions. We discuss numerical effects of the boundary of soft gluon resolution scale parameter on the resulting parton distribution functions. We show that a very good fit of the integrated TMDs to high precision HERA data can be obtained over a large range in x and Q{sup 2}.
Collinear and transverse momentum dependent parton densities obtained with a parton branching method
International Nuclear Information System (INIS)
Lelek, Aleksandra
2017-10-01
We present a solution of the DGLAP evolution equations, written in terms of Sudakov form factors to describe the branching and no-branching probabilities, using a parton branching Monte Carlo method. We demonstrate numerically that this method reproduces the semi-analytical solutions. We show how this method can be used to determine Transverse Momentum Dependent (TMD) parton distribution functions, in addition to the usual integrated parton distributions functions. We discuss numerical effects of the boundary of soft gluon resolution scale parameter on the resulting parton distribution functions. We show that a very good fit of the integrated TMDs to high precision HERA data can be obtained over a large range in x and Q 2 .
What is the transverse momentum of partons
International Nuclear Information System (INIS)
Close, F.E.; Halzen, F.; Scott, D.M.
1977-01-01
Theoretical arguments for a picture where the average transverse momentum of partons inside hadrons increases when x increases towards x=0.4 approximately 0.5, peaks and subsequently decreases when x approaches 1. This result is contrary to that suggested by asymptotic freedom arguments. Phenomenological support for this is discussed. (Auth.)
Parton dynamics in hadronic processes. Final report
International Nuclear Information System (INIS)
Sukhatme, U.P.
1984-07-01
We have elucidated several aspects of the dual parton fragmentation model for low transverse momentum multiparticle production in hadronic collisions previously developed by the author and collaborators at Orsay, France. In particular, we have verified that the dual parton model correctly reproduces recently obtained two particle inclusive distributions and particle ratios in the central region of pp and anti pp collisions. This work sheds light on the dynamics of partons in a hadronic collision since it strongly indicates that a valence quark from each initial hadron is held back with a small momentum fraction. Also, we have extended the dual parton approach to include diffraction dissocation and studied the consequences on inclusive pion production in pp interactions. We have investigated the virtues and limitations of logarithmic perturbation theory, which is often a much simpler alternative to standard Rayleigh-Schroedinger perturbation theory. Finally, we have developed and studied the shifted 1/N expansion for the enrgy eigenstates in non-relativistic quantum mechanics. Our results provide an accurate, rapidly convergent, powerful new way of handling any spherically symmetric potential. 18 references
QCD parton model at collider energies
International Nuclear Information System (INIS)
Ellis, R.K.
1984-09-01
Using the example of vector boson production, the application of the QCD improved parton model at collider energies is reviewed. The reliability of the extrapolation to SSC energies is assessed. Predictions at √S = 0.54 TeV are compared with data. 21 references
Correlations in the Parton Recombination Model
Energy Technology Data Exchange (ETDEWEB)
Bass, S.A. [Department of Physics, Duke University, Durham, NC 27708-0305 (United States); RIKEN BNL Research Center, Brookhaven Nat. Lab., Upton, NY 11973 (United States); Fries, R.J. [School of Physics and Astronomy, Univ. of Minnesota, Minneapolis, MN 55455 (United States); Mueller, B. [Department of Physics, Duke University, Durham, NC 27708-0305 (United States)
2006-08-07
We describe how parton recombination can address the recent measurement of dynamical jet-like two particle correlations. In addition we discuss the possible effect realistic light-cone wave-functions including higher Fock-states may have on the well-known elliptic flow valence-quark number scaling law.
Parton distribution and Tevatron jet data
International Nuclear Information System (INIS)
Alekhin, S.; Bluemlein, J.; Moch, S.
2011-05-01
We study the impact of Tevatron jet data on a global fit of parton distribution functions and on the determination of the value of the strong coupling constant α s (M Z ). The consequences are illustrated for cross sections of Higgs boson production at Tevatron and the LHC. (orig.)
From form factors to generalized parton distributions
Energy Technology Data Exchange (ETDEWEB)
Diehl, Markus
2013-06-15
I present an extraction of generalized parton distributions from selected data on the electromagnetic nucleon form factors. The extracted distributions can in particular be used to quantify the contribution to the proton spin from the total angular momentum carried by valence quarks, as well as their transverse spatial distribution inside the proton.
Indian Academy of Sciences (India)
Partons and jets at the LHC. DAVISON E SOPER. Institute of Theoretical Science, University of Oregon, Eugene, OR 97403-5203, USA. Abstract. I review some issues related to short distance QCD and its relation to the experimental program of the large hadron collider (LHC) now under construction in Geneva. Keywords.
Frozen-shower simulation of electromagnetic showers in the ATLAS forward calorimeter
Gasnikova, Ksenia; The ATLAS collaboration
2016-01-01
Accurate simulation of calorimeter response for high energy electromagnetic particles is essential for the LHC experiments. Detailed simulation of the electromagnetic showers using Geant4 is however very CPU intensive and various fast simulation methods were proposed instead. The frozen shower simulation substitutes the full propagation of the showers for energies below 1~GeV by showers taken from a pre-simulated library. The method is used for production of the main ATLAS Monte Carlo samples, greatly improving the production time. The frozen showers describe shower shapes, sampling fraction, sampling and noise-related fluctuations very well, while description of the constant term, related to calorimeter non-uniformity, requires a careful choice of the shower library binning. A new method is proposed to tune the binning variables, using multivariate techniques. The method is tested and optimized for the description of the ATLAS forward calorimeter.
Shower library technique for fast simulation of showers in calorimeters of the H1 experiment
International Nuclear Information System (INIS)
Raičević, N.; Glazov, A.; Zhokin, A.
2013-01-01
Fast simulation of showers in calorimeters is very important for particle physics analysis since shower simulation typically takes significant amount of the simulation time. At the same time, a simulation must reproduce experimental data in the best possible way. In this paper, a fast simulation of showers in two calorimeters of the H1 experiment is presented. High speed and good quality of shower simulation is achieved by using a shower library technique in which the detector response is simulated using a collection of stored showers for different particle types and topologies. The library is created using the GEANT programme. The fast simulation based on shower library is compared to the data collected by the H1 experiment
Pion showers in highly granular calorimeters
Indian Academy of Sciences (India)
New results on properties of hadron showers created by pion beam at 8–80 GeV in high granular electromagnetic and hadron calorimeters are presented. Data were used for the ﬁrst time to investigate the separation of the neutral and charged hadron showers. The result is important to verify the prediction of the PFA ...
Microwave detection of air showers with MIDAS
Czech Academy of Sciences Publication Activity Database
Facal San Luis, P.; Alekotte, I.; Alvarez, J.; Berlin, A.; Bertou, X.; Bogdan, M.; Boháčová, Martina; Bonifazi, C.; Carvalho, W.R.; de Mello Neto, J.R.T.; Genat, J.F.; Mills, E.; Monasor, M.; Privitera, P.; Reyes, I.C.; d´Orfeuil, B.R.; Santos, E.M.; Wayne, S.; Williams, C.; Zas, E.
2012-01-01
Roč. 662, Sup. 1 (2012), "S118"-"S123" ISSN 0168-9002 R&D Projects: GA MŠk(CZ) LA08016 Institutional research plan: CEZ:AV0Z10100502 Keywords : MIDAS (Microwave Detector of Air Showers) * extensive air showers Subject RIV: BF - Elementary Particles and High Energy Physics Impact factor: 1.142, year: 2012
Cosmic Rays and Extensive Air Showers
Stanev, Todor
2010-01-01
We begin with a brief introduction of the cosmic ray energy spectrum and its main features. At energies higher than 105 GeV cosmic rays are detected by the showers they initiate in the atmosphere. We continues with a brief description of the energy spectrum and composition derived from air shower data.
Scaling analysis of meteorite shower mass distributions
DEFF Research Database (Denmark)
Oddershede, Lene; Meibom, A.; Bohr, Jakob
1998-01-01
Meteorite showers are the remains of extraterrestrial objects which are captivated by the gravitational field of the Earth. We have analyzed the mass distribution of fragments from 16 meteorite showers for scaling. The distributions exhibit distinct scaling behavior over several orders of magnetude......; the observed scaling exponents vary from shower to shower. Half of the analyzed showers show a single scaling region while the orther half show multiple scaling regimes. Such an analysis can provide knowledge about the fragmentation process and about the original meteoroid. We also suggest to compare...... the observed scaling exponents to exponents observed in laboratory experiments and discuss the possibility that one can derive insight into the original shapes of the meteoroids....
Probe initial parton density and formation time via jet quenching
International Nuclear Information System (INIS)
Wang, Xin-Nian
2002-01-01
Medium modification of jet fragmentation function due to multiple scattering and induced gluon radiation leads directly to jet quenching or suppression of leading particle distribution from jet fragmentation. One can extract an effective total parton energy loss which can be related to the total transverse momentum broadening. For an expanding medium, both are shown to be sensitive to the initial parton density and formation time. Therefore, one can extract the initial parton density and formation time from simultaneous measurements of parton energy loss and transverse momentum broadening. Implication of the recent experimental data on effects of detailed balance in parton energy loss is also discussed
Correlations in double parton distributions. Effects of evolution
International Nuclear Information System (INIS)
Diehl, Markus; Keane, Shane; Kasemets, Tomas; Vrije Univ., Amsterdam
2014-01-01
We numerically investigate the impact of scale evolution on double parton distributions, which are needed to compute multiple hard scattering processes. Assuming correlations between longitudinal and transverse variables or between the parton spins to be present at a low scale, we study how they are affected by evolution to higher scales, i.e. by repeated parton emission. We find that generically evolution tends to wash out correlations, but with a speed that may be slow or fast depending on kinematics and on the type of correlation. Nontrivial parton correlations may hence persist in double parton distributions at the high scales relevant for hard scattering processes.
CT14 intrinsic charm parton distribution functions from CTEQ-TEA global analysis
Hou, Tie-Jiun; Dulat, Sayipjamal; Gao, Jun; Guzzi, Marco; Huston, Joey; Nadolsky, Pavel; Schmidt, Carl; Winter, Jan; Xie, Keping; Yuan, C.-P.
2018-02-01
We investigate the possibility of a (sizable) nonperturbative contribution to the charm parton distribution function (PDF) in a nucleon, theoretical issues arising in its interpretation, and its potential impact on LHC scattering processes. The "fitted charm" PDF obtained in various QCD analyses contains a process-dependent component that is partly traced to power-suppressed radiative contributions in DIS and is generally different at the LHC. We discuss separation of the universal component of the nonperturbative charm from the rest of the radiative contributions and estimate its magnitude in the CT14 global QCD analysis at the next-to-next-to leading order in the QCD coupling strength, including the latest experimental data from HERA and the Large Hadron Collider. Models for the nonperturbative charm PDF are examined as a function of the charm quark mass and other parameters. The prospects for testing these models in the associated production of a Z boson and a charm jet at the LHC are studied under realistic assumptions, including effects of the final-state parton showering.
Czech Academy of Sciences Publication Activity Database
Adare, A.; Afanasiev, S.; Aidala, C.; Růžička, Pavel; Tomášek, Michal
2017-01-01
Roč. 96, č. 2 (2017), s. 1-19, č. článku 024907. ISSN 2469-9985 Institutional support: RVO:68378271 Keywords : parton * showers * HERWIG * PYTHIA * experimental results * statistical analysis * 200 GeV-cms Subject RIV: BF - Elementary Particles and High Energy Physics OBOR OECD: Particles and field physics Impact factor: 3.820, year: 2016
Multiple parton interactions at the LHC
Gaunt, Jonathan Richard
2018-01-01
Many high-energy collider experiments (including the current Large Hadron Collider at CERN) involve the collision of hadrons. Hadrons are composite particles consisting of partons (quarks and gluons), and this means that in any hadron–hadron collision there will typically be multiple collisions of the constituents — i.e. multiple parton interactions (MPI). Understanding the nature of the MPI is important in terms of searching for new physics in the products of the scatters, and also in its own right to gain a greater understanding of hadron structure. This book aims at providing a pedagogical introduction and a comprehensive review of different research lines linked by an involvement of MPI phenomena. It is written by pioneers as well as young leading scientists, and reviews both experimental findings and theoretical developments, discussing also the remaining open issues.
Momentum transfer dependence of generalized parton distributions
Energy Technology Data Exchange (ETDEWEB)
Sharma, Neetika [Indian Institute of Science Education and Research Mohali, S.A.S. Nagar, Punjab (India)
2016-11-15
We revisit the model for parametrization of the momentum dependence of nucleon generalized parton distributions in the light of recent MRST measurements of parton distribution functions (A.D. Martin et al., Eur. Phys. J. C 63, 189 (2009)). Our parametrization method with a minimum set of free parameters give a sufficiently good description of data for Dirac and Pauli electromagnetic form factors of proton and neutron at small and intermediate values of momentum transfer. We also calculate the GPDs for up- and down-quarks by decomposing the electromagnetic form factors for the nucleon using the charge and isospin symmetry and also study the evolution of GPDs to a higher scale. We further investigate the transverse charge densities for both the unpolarized and transversely polarized nucleon and compare our results with Kelly's distribution. (orig.)
New results in the Dual Parton Model
International Nuclear Information System (INIS)
Van, J.T.T.; Capella, A.
1984-01-01
In this paper, the similarity between the x distribution for particle production and the fragmentation functions are observed in e+e- collisions and in deep inelastic scattering are presented. Based on the observation, the authors develop a complete approach to multiparticle production which incorporates the most important features and concepts learned about high energy collisions. 1. Topological expansion : the dominant diagram at high energy corresponds to the simplest topology. 2. Unitarity : diagrams of various topology contribute to the cross sections in a way that unitary is preserved. 3. Regge behaviour and Duality. 4. Partonic structure of hadrons. These general theoretical ideas, result from many joint experimental and theoretical efforts on the study of soft hadron physics. The dual parton model is able to explain all the experimental features from FNAL to SPS collider energies. It has all the properties of an S-matrix theory and provides a unified description of hadron-hadron, hadron-nucleus and nucleus-nucleus collisions
Structure functions are not parton probabilities
International Nuclear Information System (INIS)
Brodsky, Stanley J.; Hoyer, Paul; Sannino, Francesco; Marchal, Nils; Peigne, Stephane
2002-01-01
The common view that structure functions measured in deep inelastic lepton scattering are determined by the probability of finding quarks and gluons in the target is not correct in gauge theory. We show that gluon exchange between the fast, outgoing partons and target spectators, which is usually assumed to be an irrelevant gauge artifact, affects the leading twist structure functions in a profound way. This observation removes the apparent contradiction between the projectile (eikonal) and target (parton model) views of diffractive and small x B phenomena. The diffractive scattering of the fast outgoing quarks on spectators in the target causes shadowing in the DIS cross section. Thus the depletion of the nuclear structure functions is not intrinsic to the wave function of the nucleus, but is a coherent effect arising from the destructive interference of diffractive channels induced by final state interactions. This is consistent with the Glauber-Gribov interpretation of shadowing as a rescattering effect
Parton Distributions in the Higgs Boson Era
Rojo, Juan
2013-01-01
Parton distributions are an essential ingredient of the LHC program. PDFs are relevant for precision Standard Model measurements, for Higgs boson characterization as well as for New Physics searches. In this contribution I review recent progress in the determination of the parton distributions of the proton during the last year. Important developments include the impact of new LHC measurements to pin down poorly known PDFs, studies of theoretical uncertainties, higher order calculations for processes relevant for PDF determinations, PDF benchmarking exercises with LHC data, as well as methodological and statistical improvements in the global analysis framework. I conclude with some speculative considerations about future directions in PDF determinations from the theory point of view.
Occurrence of Legionella in UK household showers.
Collins, Samuel; Stevenson, David; Bennett, Allan; Walker, Jimmy
2017-04-01
Household water systems have been proposed as a source of sporadic, community acquired Legionnaires' disease. Showers represent a frequently used aerosol generating device in the domestic setting yet little is known about the occurrence of Legionella spp. in these systems. This study has investigated the prevalence of Legionella spp. by culture and qPCR in UK household showers. Ninety nine showers from 82 separate properties in the South of England were sampled. Clinically relevant Legionella spp. were isolated by culture in 8% of shower water samples representing 6% of households. Legionella pneumophila sg1 ST59 was isolated from two showers in one property and air sampling demonstrated its presence in the aerosol state. A further 31% of showers were positive by Legionella spp. qPCR. By multi-variable binomial regression modelling Legionella spp. qPCR positivity was associated with the age of the property (p=0.02), the age of the shower (p=0.01) and the frequency of use (p=0.09). The concentration of Legionella spp. detected by qPCR was shown to decrease with increased frequency of use (p=0.04) and more frequent showerhead cleaning (p=0.05). There was no association between Legionella spp. qPCR positivity and the cold water supply or the showerhead material (p=0.65 and p=0.71, respectively). Household showers may be important reservoirs of clinically significant Legionella and should be considered in source investigations. Simple public health advice may help to mitigate the risk of Legionella exposure in the domestic shower environment. Crown Copyright © 2016. Published by Elsevier GmbH. All rights reserved.
PYTHON - the Monte Carlo for deep inelastic leptoproduction. Short write up
International Nuclear Information System (INIS)
Bengtsson, M.
1988-05-01
As its name indicates, this is a relative to the Lund Monte Carlo for hadronic interactions - PYTHIA. It performs parton shower evolution in deep inelastic scattering which results in a complete event on the partonic level. Subsequent fragmentation into hadrons may be done using the Lund string fragmentation scheme. The basic hard interaction processes, neutral and charged currents, are included together with a theoretically well developed scheme for parton showers where the first order QCD matrix element is used as a guideline for hard emission. (orig.)
Deep inelastic processes and the parton model
International Nuclear Information System (INIS)
Altarelli, G.
The lecture was intended as an elementary introduction to the physics of deep inelastic phenomena from the point of view of theory. General formulae and facts concerning inclusive deep inelastic processes in the form: l+N→l'+hadrons (electroproduction, neutrino scattering) are first recalled. The deep inelastic annihilation e + e - →hadrons is then envisaged. The light cone approach, the parton model and their relation are mainly emphasized
Generalized Parton Distributions and their Singularities
Energy Technology Data Exchange (ETDEWEB)
Anatoly Radyushkin
2011-04-01
A new approach to building models of generalized parton distributions (GPDs) is discussed that is based on the factorized DD (double distribution) Ansatz within the single-DD formalism. The latter was not used before, because reconstructing GPDs from the forward limit one should start in this case with a very singular function $f(\\beta)/\\beta$ rather than with the usual parton density $f(\\beta)$. This results in a non-integrable singularity at $\\beta=0$ exaggerated by the fact that $f(\\beta)$'s, on their own, have a singular $\\beta^{-a}$ Regge behavior for small $\\beta$. It is shown that the singularity is regulated within the GPD model of Szczepaniak et al., in which the Regge behavior is implanted through a subtracted dispersion relation for the hadron-parton scattering amplitude. It is demonstrated that using proper softening of the quark-hadron vertices in the regions of large parton virtualities results in model GPDs $H(x,\\xi)$ that are finite and continuous at the "border point'' $x=\\xi$. Using a simple input forward distribution, we illustrate the implementation of the new approach for explicit construction of model GPDs. As a further development, a more general method of regulating the $\\beta=0$ singularities is proposed that is based on the separation of the initial single DD $f(\\beta, \\alpha)$ into the "plus'' part $[f(\\beta,\\alpha)]_{+}$ and the $D$-term. It is demonstrated that the "DD+D'' separation method allows to (re)derive GPD sum rules that relate the difference between the forward distribution $f(x)=H(x,0)$ and the border function $H(x,x)$ with the $D$-term function $D(\\alpha)$.
Experimental studies of generalized parton distributions
International Nuclear Information System (INIS)
Kabuss, E.M.
2014-01-01
Generalized parton distributions (GPD) provide a new way to study the nucleon structure. Experimentally they can be accessed using hard exclusive processes such as deeply virtual Compton scattering and meson production. First insights to GPDs were already obtained from measurements at DESY, JLAB and CERN, while new ambitious studies are planned at the upgraded JLAB at 12 GeV and at CERN. Here, some emphasis will be put onto the planned COMPASS II programme. (author)
An introduction to the Generalized Parton Distributions
International Nuclear Information System (INIS)
Michel Garcon
2002-01-01
The concepts of Generalized Parton Distributions (GPD) are reviewed in an introductory and phenomenological fashion. These distributions provide a rich and unifying picture of the nucleon structure. Their physical meaning is discussed. The GPD are in principle measurable through exclusive deeply virtual production of photons (DVCS) or of mesons (DVMP). Experiments are starting to test the validity of these concepts. First results are discussed and new experimental projects presented, with an emphasis on this program at Jefferson Lab
Fast shower simulation in the ATLAS calorimeter
Barberio, E; Butler, B; Cheung, S L; Dell'Acqua, A; Di Simone, A; Ehrenfeld, W; Gallas, M V; Glazov, A; Marshall, Z; Müller, J; Placakyte, R; Rimoldi, A; Savard, P; Tsulaia, V; Waugh, A; Young, C C
2008-01-01
The time to simulate pp collisions in the ATLAS detector is largely dominated by the showering of electromagnetic particles in the heavy parts of the detector, especially the electromagnetic barrel and endcap calorimeters. Two procedures have been developed to accelerate the processing time of electromagnetic particles in these regions: (1) a fast shower parameterisation and (2) a frozen shower library. Both work by generating the response of the calorimeter to electrons and positrons with Geant 4, and then reintroduce the response into the simulation at runtime.
Radar reflection off extensive air showers
Directory of Open Access Journals (Sweden)
Werner F.
2013-06-01
Full Text Available We investigate the possibility of detecting extensive air showers by the radar technique. Considering a bistatic radar system and different shower geometries, we simulate reflection of radio waves off the static plasma produced by the shower in the air. Using the Thomson cross-section for radio wave reflection, we obtain the time evolution of the signal received by the antennas. The frequency upshift of the radar echo and the power received are studied to verify the feasibility of the radar detection technique.
Comet showers and Nemesis, the death star
International Nuclear Information System (INIS)
Hills, J.G.
1984-01-01
The recently proposed hypothesis that the periodic extinctions of terrestrial species are the result of comet showers catalyzed by a hypothetical distant solar companion, Nemesis, a tale of global death by comet bombardment of the earth, is discussed
QCD Monte-Carlo model tuning studies with CMS data at 13 TeV
Sunar Cerci, Deniz
2018-01-01
New CMS PYTHIA 8 event tunes are presented. The new tunes are obtained using minimum bias and underlying event observables using Monte Carlo configurations with consistent parton distribution functions and strong coupling constant values in the matrix element and the parton shower. Validation and performance studies are presented by comparing the predictions of the new tune to various soft- and hard-QCD measurements at 7, 8 and 13 TeV with CMS.
Microwave detection of air showers with MIDAS
Energy Technology Data Exchange (ETDEWEB)
Facal San Luis, P., E-mail: facal@kicp.uchicago.edu [University of Chicago, Enrico Fermi Institue and Kavli Institute for Cosmological Physics, 5640 South Ellis Avenue, Chicago, IL 60637 (United States); Alekotte, I. [Centro Atomico Bariloche and Instituto Balseiro (CNEA-UNCuyo-CONICET), 8400 San Carlos de Bariloche, Rio Negro (Argentina); Alvarez, J. [Universidad de Santiago de Compostela, Departamento de Fisica de Particulas, Campus Sur, E-15782 Santiago de Compostela (Spain); Berlin, A. [University of Chicago, Enrico Fermi Institue and Kavli Institute for Cosmological Physics, 5640 South Ellis Avenue, Chicago, IL 60637 (United States); Bertou, X. [Centro Atomico Bariloche and Instituto Balseiro (CNEA-UNCuyo-CONICET), 8400 San Carlos de Bariloche, Rio Negro (Argentina); Bogdan, M.; Bohacova, M. [University of Chicago, Enrico Fermi Institue and Kavli Institute for Cosmological Physics, 5640 South Ellis Avenue, Chicago, IL 60637 (United States); Bonifazi, C. [Univ. Federal do Rio de Janeiro (UFRJ), Instituto de Fisica, Cidade Universitaria, Caixa Postal 68528, 21945-970 Rio de Janeiro, RJ (Brazil); Carvalho, W.R. [Universidad de Santiago de Compostela, Departamento de Fisica de Particulas, Campus Sur, E-15782 Santiago de Compostela (Spain); Mello Neto, J.R.T. de [Univ. Federal do Rio de Janeiro (UFRJ), Instituto de Fisica, Cidade Universitaria, Caixa Postal 68528, 21945-970 Rio de Janeiro, RJ (Brazil); Genat, J.F.; Mills, E.; Monasor, M.; Privitera, P.; Reyes, I.C.; Rouille d& #x27; Orfeuil, B. [University of Chicago, Enrico Fermi Institue and Kavli Institute for Cosmological Physics, 5640 South Ellis Avenue, Chicago, IL 60637 (United States); and others
2012-01-11
MIDAS (MIcrowave Detector of Air Showers) is a prototype of a microwave telescope to detect extensive air showers: it images a 20{sup Degree-Sign } Multiplication-Sign 10{sup Degree-Sign} region of the sky with a 4.5 m parabolic reflector and 53 feeds in the focal plane. It has been commissioned in March 2010 and is currently taking data. We present the design, performance and first results of MIDAS.
Microwave detection of air showers with MIDAS
International Nuclear Information System (INIS)
Facal San Luis, P.; Alekotte, I.; Alvarez, J.; Berlin, A.; Bertou, X.; Bogdan, M.; Bohacova, M.; Bonifazi, C.; Carvalho, W.R.; Mello Neto, J.R.T. de; Genat, J.F.; Mills, E.; Monasor, M.; Privitera, P.; Reyes, I.C.; Rouille d’Orfeuil, B.
2012-01-01
MIDAS (MIcrowave Detector of Air Showers) is a prototype of a microwave telescope to detect extensive air showers: it images a 20 ° ×10 ° region of the sky with a 4.5 m parabolic reflector and 53 feeds in the focal plane. It has been commissioned in March 2010 and is currently taking data. We present the design, performance and first results of MIDAS.
Parton-hadron cascade approach at SPS and RHIC
Energy Technology Data Exchange (ETDEWEB)
Nara, Yasushi [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment
1998-07-01
A parton-hadron cascade model which is the extension of hadronic cascade model incorporating hard partonic scattering based on HIJING is presented to describe the space-time evolution of parton/hadron system produced by ultra-relativistic nuclear collisions. Hadron yield, baryon stopping and transverse momentum distribution are calculated and compared with HIJING and VNI. Baryon density, energy density and temperature for RHIC are calculated within this model. (author)
QCD evolution equations for high energy partons in nuclear matter
Kinder-Geiger, Klaus; Geiger, Klaus; Mueller, Berndt
1994-01-01
We derive a generalized form of Altarelli-Parisi equations to decribe the time evolution of parton distributions in a nuclear medium. In the framework of the leading logarithmic approximation, we obtain a set of coupled integro- differential equations for the parton distribution functions and equations for the virtuality (``age'') distribution of partons. In addition to parton branching processes, we take into account fusion and scattering processes that are specific to QCD in medium. Detailed balance between gain and loss terms in the resulting evolution equations correctly accounts for both real and virtual contributions which yields a natural cancellation of infrared divergences.
Studies of vector boson transverse momentum simulation in Monte Carlo event generators
The ATLAS collaboration
2011-01-01
We present studies of event generator behaviours regarding vector boson production characteristics, in particular the transverse momentum, pT, of the $Z$ boson as measured by ATLAS, for discussion at the LPCC working group meeting on precision electroweak physics at the LHC. The results discussed focus on the poor descriptions of ATLAS $W$ and $Z$ pT spectra by the ATLAS AUET2B LO** tune of PYTHIA6, and by the shower-matched NLO generator combination POWHEG+PYTHIA6. We show that both standalone PYTHIA6 and POWHEG can be made to describe the Sudakov peak of the ATLAS $Z$ pT distribution by tuning of the PYTHIA parton shower -- different approaches are required in each case. Comparisons of other NLO generators to the $Z$ pT data are also shown.
Scholten, O.; Trinh, T. N. G.; de Vries, K. D.; Hare, B. M.
2018-01-01
The radio intensity and polarization footprint of a cosmic-ray induced extensive air shower is determined by the time-dependent structure of the current distribution residing in the plasma cloud at the shower front. In turn, the time dependence of the integrated charge-current distribution in the
Macroscopic treatment of radio emission from cosmic ray air showers based on shower simulations
Werner, Klaus; Scholten, Olaf
We present a macroscopic calculation of coherent electro-magnetic radiation from air showers initiated by ultra-high energy cosmic rays, based on currents obtained from Monte Carlo simulations of air showers in a realistic geo-magnetic field. We can clearly relate the time signal to the time
Scholten, O.; Trinh, T. N. G.; de Vries, K. D.; Hare, B. M.
2018-01-01
The radio intensity and polarization footprint of a cosmic-ray induced extensive air shower is determined by the time-dependent structure of the current distribution residing in the plasma cloud at the shower front. In turn, the time dependence of the integrated charge-current distribution in the plasma cloud, the longitudinal shower structure, is determined by interesting physics which one would like to extract, such as the location and multiplicity of the primary cosmic-ray collision or the values of electric fields in the atmosphere during thunderstorms. To extract the structure of a shower from its footprint requires solving a complicated inverse problem. For this purpose we have developed a code that semianalytically calculates the radio footprint of an extensive air shower given an arbitrary longitudinal structure. This code can be used in an optimization procedure to extract the optimal longitudinal shower structure given a radio footprint. On the basis of air-shower universality we propose a simple parametrization of the structure of the plasma cloud. This parametrization is based on the results of Monte Carlo shower simulations. Deriving the parametrization also teaches which aspects of the plasma cloud are important for understanding the features seen in the radio-emission footprint. The calculated radio footprints are compared with microscopic CoREAS simulations.
ABM11 parton distributions and benchmarks
International Nuclear Information System (INIS)
Alekhin, Sergey; Bluemlein, Johannes; Moch, Sven-Olaf
2012-08-01
We present a determination of the nucleon parton distribution functions (PDFs) and of the strong coupling constant α s at next-to-next-to-leading order (NNLO) in QCD based on the world data for deep-inelastic scattering and the fixed-target data for the Drell-Yan process. The analysis is performed in the fixed-flavor number scheme for n f =3,4,5 and uses the MS scheme for α s and the heavy quark masses. The fit results are compared with other PDFs and used to compute the benchmark cross sections at hadron colliders to the NNLO accuracy.
ABM11 parton distributions and benchmarks
Energy Technology Data Exchange (ETDEWEB)
Alekhin, Sergey [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany); Institut Fiziki Vysokikh Ehnergij, Protvino (Russian Federation); Bluemlein, Johannes; Moch, Sven-Olaf [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany)
2012-08-15
We present a determination of the nucleon parton distribution functions (PDFs) and of the strong coupling constant {alpha}{sub s} at next-to-next-to-leading order (NNLO) in QCD based on the world data for deep-inelastic scattering and the fixed-target data for the Drell-Yan process. The analysis is performed in the fixed-flavor number scheme for n{sub f}=3,4,5 and uses the MS scheme for {alpha}{sub s} and the heavy quark masses. The fit results are compared with other PDFs and used to compute the benchmark cross sections at hadron colliders to the NNLO accuracy.
Quasi parton distributions and the gradient flow
International Nuclear Information System (INIS)
Monahan, Christopher; Orginos, Kostas
2017-01-01
We propose a new approach to determining quasi parton distribution functions (PDFs) from lattice quantum chromodynamics. By incorporating the gradient flow, this method guarantees that the lattice quasi PDFs are finite in the continuum limit and evades the thorny, and as yet unresolved, issue of the renormalization of quasi PDFs on the lattice. In the limit that the flow time is much smaller than the length scale set by the nucleon momentum, the moments of the smeared quasi PDF are proportional to those of the lightfront PDF. Finally, we use this relation to derive evolution equations for the matching kernel that relates the smeared quasi PDF and the light-front PDF.
A Lattice Calculation of Parton Distributions
International Nuclear Information System (INIS)
Alexandrou, Constantia; Cichy, Krzysztof; Poznan Univ.; Drach, Vincent; Univ. of Southern Denmark, Odense; Garcia-Ramos, Elena; Humboldt-Universitaet, Berlin; Hadjiyiannakou, Kyriakos; Jansen, Karl; Steffens, Fernanda; Wiese, Christian
2015-04-01
We report on our exploratory study for the direct evaluation of the parton distribution functions from lattice QCD, based on a recently proposed new approach. We present encouraging results using N f =2+1+1 twisted mass fermions with a pion mass of about 370 MeV. The focus of this work is a detailed description of the computation, including the lattice calculation, the matching to an infinite momentum and the nucleon mass correction. In addition, we test the effect of gauge link smearing in the operator to estimate the influence of the Wilson line renormalization, which is yet to be done.
Generalized parton distribution for non zero skewness
International Nuclear Information System (INIS)
Kumar, Narinder; Dahiya, Harleen; Teryaev, Oleg
2012-01-01
In the theory of strong interactions the main open question is how the nucleon and other hadrons are built from quarks and gluons, the fundamental degrees of freedom in QCD. An essential tool to investigate hadron structure is the study of deep inelastic scattering processes, where individual quarks and gluons can be resolved. The parton densities extracted from such processes encode the distribution of longitudinal momentum and polarization carried by quarks, antiquarks and gluons within a fast moving hadron. They have provided much to shape the physical picture of hadron structure. In the recent years, it has become clear that appropriate exclusive scattering processes may provide such information encoded in the general parton distributions (GPDs). Here, we investigate the GPD for deep virtual compton scattering (DVCS) for the non zero skewness. The study has investigated the GPDs by expressing them in terms of overlaps of light front wave functions (LFWFs). The work represented a spin 1/2 system as a composite of spin 1/2 fermion and spin 1 boson with arbitrary masses
International Nuclear Information System (INIS)
Olness, F.I.; Tung, Wu-Ki
1989-10-01
Applications of the QCD-based parton model to new physics processes involving heavy partons are illustrated using charged Higgs production. The naive parton model predictions are found to over-estimate the actual cross section by a factor of 2 to 5. The role of the top quark as a ''parton'' is examined, and the energy range over which heavy quarks (or other particles) should or should not be naturally treated as ''partons'' is delineated. 12 refs., 5 figs
Large psub(T) pion production and clustered parton model
Energy Technology Data Exchange (ETDEWEB)
Kanki, T [Osaka Univ., Toyonaka (Japan). Coll. of General Education
1977-05-01
Recent experimental results on the large p sub(T) inclusive ..pi../sup 0/ productions by pp and ..pi..p collisions are interpreted by the parton model in which the constituent quarks are defined to be the clusters of the quark-partons and gluons.
Comparison of parton distributions and structure functions for the proton
International Nuclear Information System (INIS)
Abramowicz, H.; Charchula, K.; Krawczyk, M.; Levy, A.
1990-09-01
A comparative study of the most popular parton parametrizations is presented. The individual parton distributions as well as the F 2 structure function are discussed with a particular emphasis on the low x region, 10 -4 -2 . The predictions of these parametrizations for the F 2 structure function have a wide spread which persists also in the HERA kinematical region. (orig.)
Nucleon generalized parton distributions from full lattice QCD
International Nuclear Information System (INIS)
Haegler, P.; Schroers, W.; Bratt, J.; Negele, J.W.; Pochinsky, A.V.
2007-07-01
We present a comprehensive study of the lowest moments of nucleon generalized parton distributions in N f =2+1 lattice QCD using domain wall valence quarks and improved staggered sea quarks. Our investigation includes helicity dependent and independent generalized parton distributions for pion masses as low as 350 MeV and volumes as large as (3.5 fm) 3 . (orig.)
Pion and kaon valence-quark parton quasidistributions
Xu, Shu-Sheng; Chang, Lei; Roberts, Craig D.; Zong, Hong-Shi
2018-05-01
Algebraic Ansätze for the Poincaré-covariant Bethe-Salpeter wave functions of the pion and kaon are used to calculate their light-front wave functions, parton distribution amplitudes, parton quasidistribution amplitudes, valence parton distribution functions, and parton quasidistribution functions (PqDFs). The light-front wave functions are broad, concave functions, and the scale of flavor-symmetry violation in the kaon is roughly 15%, being set by the ratio of emergent masses in the s - and u -quark sectors. Parton quasidistribution amplitudes computed with longitudinal momentum Pz=1.75 GeV provide a semiquantitatively accurate representation of the objective parton distribution amplitude, but even with Pz=3 GeV , they cannot provide information about this amplitude's end point behavior. On the valence-quark domain, similar outcomes characterize PqDFs. In this connection, however, the ratio of kaon-to-pion u -quark PqDFs is found to provide a good approximation to the true parton distribution function ratio on 0.4 ≲x ≲0.8 , suggesting that with existing resources computations of ratios of parton quasidistributions can yield results that support empirical comparison.
Transverse momentum in double parton scattering. Factorisation, evolution and matching
International Nuclear Information System (INIS)
Buffing, Maarten G.A.; Diehl, Markus; Kasemets, Tomas
2017-08-01
We give a description of double parton scattering with measured transverse momenta in the final state, extending the formalism for factorisation and resummation developed by Collins, Soper and Sterman for the production of colourless particles. After a detailed analysis of their colour structure, we derive and solve evolution equations in rapidity and renormalisation scale for the relevant soft factors and double parton distributions. We show how in the perturbative regime, transverse momentum dependent double parton distributions can be expressed in terms of simpler nonperturbative quantities and compute several of the corresponding perturbative kernels at one-loop accuracy. We then show how the coherent sum of single and double parton scattering can be simplified for perturbatively large transverse momenta, and we discuss to which order resummation can be performed with presently available results. As an auxiliary result, we derive a simple form for the square root factor in the Collins construction of transverse momentum dependent parton distributions.
Transverse momentum in double parton scattering. Factorisation, evolution and matching
Energy Technology Data Exchange (ETDEWEB)
Buffing, Maarten G.A.; Diehl, Markus [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Kasemets, Tomas [Nikhef, Amsterdam (Netherlands). Theory Group; VU Univ. Amsterdam (Netherlands)
2017-08-15
We give a description of double parton scattering with measured transverse momenta in the final state, extending the formalism for factorisation and resummation developed by Collins, Soper and Sterman for the production of colourless particles. After a detailed analysis of their colour structure, we derive and solve evolution equations in rapidity and renormalisation scale for the relevant soft factors and double parton distributions. We show how in the perturbative regime, transverse momentum dependent double parton distributions can be expressed in terms of simpler nonperturbative quantities and compute several of the corresponding perturbative kernels at one-loop accuracy. We then show how the coherent sum of single and double parton scattering can be simplified for perturbatively large transverse momenta, and we discuss to which order resummation can be performed with presently available results. As an auxiliary result, we derive a simple form for the square root factor in the Collins construction of transverse momentum dependent parton distributions.
Dynamical equilibration in strongly-interacting parton-hadron matter
Directory of Open Access Journals (Sweden)
Gorenstein M.
2011-04-01
Full Text Available We study the kinetic and chemical equilibration in 'infinite' parton-hadron matter within the Parton-Hadron-String Dynamics transport approach, which is based on a dynamical quasiparticle model for partons matched to reproduce lattice-QCD results – including the partonic equation of state – in thermodynamic equilibrium. The 'infinite' matter is simulated within a cubic box with periodic boundary conditions initialized at different baryon density (or chemical potential and energy density. The transition from initially pure partonic matter to hadronic degrees of freedom (or vice versa occurs dynamically by interactions. Different thermody-namical distributions of the strongly-interacting quark-gluon plasma (sQGP are addressed and discussed.
Deep-inelastic final states in a space-time description of shower development and hadronization
International Nuclear Information System (INIS)
Ellis, J.
1996-06-01
We extend a quantum kinetic approach to the description of hadronic showers in space, time and momentum space to deep-inelastic ep collisions, with particular reference to experiments at HERA. We follow the history of hard scattering events back to the initial hadronic state and forward to the formation of colour-singlet pre-hadronic clusters and their decays into hadrons. The time evolution of the space-like initial-state shower and the time-like secondary partons are treated similarly, and cluster formation is treated using a spatial criterion motivated by confinement and a non-perturbative model for hadronization. We calculate the time evolution of particle distributions in rapidity, transverse and longitudinal space. We also compare the transverse hadronic energy flow and the distribution of observed hadronic masses with experimental data from HERA, finding encouraging results, and discuss the background to large-rapidity-gap events. The techniques developed in this paper may be applied in the future to more complicated processes such as eA, pp, pA and AA collisions. (orig.)
Deep-inelastic final states in a space-time description of shower development and hadronization
International Nuclear Information System (INIS)
Ellis, J.; Geiger, K.; Kowalski, H.
1996-01-01
We extend a quantum kinetic approach to the description of hadronic showers in space, time, and momentum space to deep-inelastic ep collisions, with particular reference to experiments at DESY HERA. We follow the history of hard scattering events back to the initial hadronic state and forward to the formation of color-singlet prehadronic clusters and their decays into hadrons. The time evolution of the spacelike initial-state shower and the timelike secondary partons are treated similarly, and cluster formation is treated using a spatial criterion motivated by confinement and a nonperturbative model for hadronization. We calculate the time evolution of particle distributions in rapidity, transverse, and longitudinal space. We also compare the transverse hadronic energy flow and the distribution of observed hadronic masses with experimental data from HERA, finding encouraging results, and discuss the background to large-rapidity-gap events. The techniques developed in this paper may be applied in the future to more complicated processes such as eA, pp, pA, and AA collisions. copyright 1996 The American Physical Society
Modeling of the Atmospheric Response to the Leonid Meteor Showers
National Research Council Canada - National Science Library
McNeil, William
1998-01-01
... showers of recent years. The model allows for ablation, deposition, diffusion and chemical dynamics, thereby permitting the computation of the modifications in the layers due to the showers in a self-consistent manner, based...
Hadron showers in a highly granular calorimeter
Energy Technology Data Exchange (ETDEWEB)
Lutz, Benjamin
2010-11-15
A future electron-positron collider like the planned International Linear Collider (ILC) needs excellent detectors to exploit the full physics potential. Different detector concepts have been evaluated for the ILC and two concepts on the particle-flow approach were validated. To make particle-flow work, a new type of imaging calorimeters is necessary in combination with a high performance tracking system, to be able to track the single particles through the full detector system. These calorimeters require an unprecedented level of both longitudinal and lateral granularity. Several calorimeter technologies promise to reach the required readout segmentation and are currently studied. This thesis addresses one of these: The analogue hadron calorimeter technology. It combines work on the technological aspects of a highly granular calorimeter with the study of hadron shower physics. The analogue hadron calorimeter technology joins a classical scintillator-steel sandwich design with a modern photo-sensor technology, the silicon photomultiplier (SiPM). The SiPM is a millimetre sized, magnetic field insensitive, and low cost photo-sensor, that opens new possibilities in calorimeter design. This thesis outlines the working principle and characteristics of these devices. The requirements for an application specific integrated circuit (ASIC) to read the SiPM are discussed; the performance of a prototype chip for SiPM readout, the SPIROC, is quantified. Also the SiPM specific reconstruction of a multi-thousand channel prototype calorimeter, the CALICE AHCAL, is explained; the systematic uncertainty of the calibration method is derived. The AHCAL does not only offer a test of the calorimeter technology, it also allows to record hadron showers with an unprecedented level of details. Test-beam measurements have been performed with the AHCAL and provide a unique sample for the development of novel analysis techniques and the validation of hadron shower simulations. A method to
Hadron showers in a highly granular calorimeter
International Nuclear Information System (INIS)
Lutz, Benjamin
2010-11-01
A future electron-positron collider like the planned International Linear Collider (ILC) needs excellent detectors to exploit the full physics potential. Different detector concepts have been evaluated for the ILC and two concepts on the particle-flow approach were validated. To make particle-flow work, a new type of imaging calorimeters is necessary in combination with a high performance tracking system, to be able to track the single particles through the full detector system. These calorimeters require an unprecedented level of both longitudinal and lateral granularity. Several calorimeter technologies promise to reach the required readout segmentation and are currently studied. This thesis addresses one of these: The analogue hadron calorimeter technology. It combines work on the technological aspects of a highly granular calorimeter with the study of hadron shower physics. The analogue hadron calorimeter technology joins a classical scintillator-steel sandwich design with a modern photo-sensor technology, the silicon photomultiplier (SiPM). The SiPM is a millimetre sized, magnetic field insensitive, and low cost photo-sensor, that opens new possibilities in calorimeter design. This thesis outlines the working principle and characteristics of these devices. The requirements for an application specific integrated circuit (ASIC) to read the SiPM are discussed; the performance of a prototype chip for SiPM readout, the SPIROC, is quantified. Also the SiPM specific reconstruction of a multi-thousand channel prototype calorimeter, the CALICE AHCAL, is explained; the systematic uncertainty of the calibration method is derived. The AHCAL does not only offer a test of the calorimeter technology, it also allows to record hadron showers with an unprecedented level of details. Test-beam measurements have been performed with the AHCAL and provide a unique sample for the development of novel analysis techniques and the validation of hadron shower simulations. A method to
Shower reconstruction in the CLUE experiment
Energy Technology Data Exchange (ETDEWEB)
Bartoli, B.; Bastieri, D.; Bigongiari, C. E-mail: bigongiari@pd.infn.it; Ciocci, M.A.; Cosulich, D.; Cresti, M.; Dokoutchaeva, V.; Kartashov, D.; Liello, F.; Malakhov, N.; Mariotti, M.; Marsella, G.; Menzione, A.; Paoletti, R.; Parlavecchio, G.; Peruzzo, L.; Piccioli, A.; Pegna, R.; Rosso, F.; Sacco, R.; Saggion, A.; Sartori, G.; Sartori, P.; Sbarra, C.; Scribano, A.; Smogailov, E.; Stamerra, A.; Turini, N
2001-04-01
The CLUE experiment studies primary cosmic rays (E{>=}2 TeV) by detecting UV (190-230 nm) Cherenkov light produced by atmospheric showers. Since atmospheric absorption in the UV range is higher than in the visible range, CLUE cannot apply algorithms normally used in IACT experiments to determine primary cosmic-ray direction. In this paper, we present a new method developed by CLUE. The algorithm performances were evaluated using simulated showers. Preliminary results of the source analysis using this new method are shown.
Shower reconstruction in the CLUE experiment
International Nuclear Information System (INIS)
Bartoli, B.; Bastieri, D.; Bigongiari, C.; Ciocci, M.A.; Cosulich, D.; Cresti, M.; Dokoutchaeva, V.; Kartashov, D.; Liello, F.; Malakhov, N.; Mariotti, M.; Marsella, G.; Menzione, A.; Paoletti, R.; Parlavecchio, G.; Peruzzo, L.; Piccioli, A.; Pegna, R.; Rosso, F.; Sacco, R.; Saggion, A.; Sartori, G.; Sartori, P.; Sbarra, C.; Scribano, A.; Smogailov, E.; Stamerra, A.; Turini, N.
2001-01-01
The CLUE experiment studies primary cosmic rays (E≥2 TeV) by detecting UV (190-230 nm) Cherenkov light produced by atmospheric showers. Since atmospheric absorption in the UV range is higher than in the visible range, CLUE cannot apply algorithms normally used in IACT experiments to determine primary cosmic-ray direction. In this paper, we present a new method developed by CLUE. The algorithm performances were evaluated using simulated showers. Preliminary results of the source analysis using this new method are shown
On chiral-odd Generalized Parton Distributions
Energy Technology Data Exchange (ETDEWEB)
Wallon, Samuel [Laboratoire de Physique Theorique d' Orsay - LPT, Bat. 210, Univ. Paris-Sud 11, 91405 Orsay Cedex (France); UPMC Univ. Paris 6, Paris (France); Pire, Bernard [Centre de Physique Theorique - CPHT, UMR 7644, Ecole Polytechnique, Bat. 6, RDC, F91128 Palaiseau Cedex (France); Szymanowski, Lech [Soltan Institute for Nuclear Studies, Hoza 69, 00691, Warsaw (Poland)
2010-07-01
The chiral-odd transversity generalized parton distributions of the nucleon can be accessed experimentally through the exclusive photoproduction process {gamma} + N {yields} {pi} + {rho} + N', in the kinematics where the meson pair has a large invariant mass and the final nucleon has a small transverse momentum, provided the vector meson is produced in a transversally polarized state. Estimated counting rates show that the experiment is feasible with real or quasi real photon beams expected at JLab at 12 GeV and in the COMPASS experiment. (Phys Letters B688,154,2010) In addition, a consistent classification of the chiral-odd pion GPDs beyond the leading twist 2 is presented. Based on QCD equations of motion and on the invariance under rotation on the light-cone of any scattering amplitude involving such GPDs, we reduce the basis of these chiral-odd GPDs to a minimal set. (author)
Insights into nucleon structure from parton distributions
Energy Technology Data Exchange (ETDEWEB)
Melnitchouk, Wally [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
2017-05-01
We review recent progress in understanding the substructure of the nucleon from global QCD analysis of parton distribution functions (PDFs). New high-precision data onW-boson production in p ¯ p collisions have significantly reduced the uncertainty on the d=u PDF ratio at large values of x, indirectly constraining models of the medium modification of bound nucleons. Drell-Yan data from pp and pd scattering reveal new information on the d¯-u¯ asymmetry, clarifying the role of chiral symmetry breaking in the nucleon. In the strange sector, a new chiral SU(3) analysis finds a valence-like component of the strange-quark PDF, giving rise to a nontrivial s- ¯ s asymmetry at moderate x values. We also review recent analyses of charm in the nucleon, which have found conflicting indications of the size of the nonperturbative charm component.
Updated lattice results for parton distributions
International Nuclear Information System (INIS)
Alexandrou, Constantia; Cichy, Krzysztof; Hadjiyiannakou, Kyriakos; Jansen, Karl; Steffens, Fernanda; Wiese, Christian
2017-07-01
We provide an analysis of the x-dependence of the bare unpolarized, helicity and transversity iso-vector parton distribution functions (PDFs) from lattice calculations employing (maximally) twisted mass fermions. The x-dependence of the calculated PDFs resembles the one of the phenomenological parameterizations, a feature that makes this approach very promising. Furthermore, we apply momentum smearing for the relevant matrix elements to compute the lattice PDFs and find a large improvement factor when compared to conventional Gaussian smearing. This allows us to extend the lattice computation of the distributions to higher values of the nucleon momentum, which is essential for the prospects of a reliable extraction of the PDFs in the future.
Updated lattice results for parton distributions
Energy Technology Data Exchange (ETDEWEB)
Alexandrou, Constantia [Cyprus Univ., Nicosia (Cyprus). Dept. of Physics; The Cyprus Institute, Nicosia (Cyprus); Cichy, Krzysztof [Frankfurt Univ. (Germany). Inst. fuer Theoretische Physik; Poznan Univ. (Poland). Faculty of Physics; Constantinou, Martha [Temple Univ., Philadelphia, PA (United States); Hadjiyiannakou, Kyriakos [Cyprus Univ., Nicosia (Cyprus). Dept. of Physics; Jansen, Karl; Steffens, Fernanda; Wiese, Christian [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC
2017-07-15
We provide an analysis of the x-dependence of the bare unpolarized, helicity and transversity iso-vector parton distribution functions (PDFs) from lattice calculations employing (maximally) twisted mass fermions. The x-dependence of the calculated PDFs resembles the one of the phenomenological parameterizations, a feature that makes this approach very promising. Furthermore, we apply momentum smearing for the relevant matrix elements to compute the lattice PDFs and find a large improvement factor when compared to conventional Gaussian smearing. This allows us to extend the lattice computation of the distributions to higher values of the nucleon momentum, which is essential for the prospects of a reliable extraction of the PDFs in the future.
An air shower array for LOFAR: LORA
Thoudam, S.; Aar, G. V.; Akker, M. V. D.; Bähren, L.; Corstanje, A.; Falcke, H.; Hörandel, J. R.; Horneffer, A.; James, C.; Mevius, M.; Scholten, O.; Singh, K.; Ter Veen, S.
2011-01-01
LOFAR is a new form of radio telescope which can detect radio emission from air showers induced by very high-energy cosmic rays. It can also look for radio emission from particle cascades on the Moon induced by ultra high-energy cosmic rays or neutrinos. To complement the radio detection, we are
Modelling of an RF plasma shower
Atanasova, M.; Carbone, E.A.D.; Mihailova, D.B.; Benova, E.; Degrez, G.; Mullen, van der J.J.A.M.
2012-01-01
A capacitive radiofrequency (RF) discharge at atmospheric pressure is studied by means of a time-dependent, two-dimensional fluid model. The plasma is created in a stationary argon gas flow guided through two perforated electrodes, hence resembling a shower. The inner electrode, the electrode facing
The parametrized simulation of electromagnetic showers
International Nuclear Information System (INIS)
Peters, S.
1992-09-01
The simulation of electromagnetic showers in calorimeters by detailed tracking of all secondary particles is extremely computer time consuming. Without loosing considerably in precision, the use of parametrizations for global shower properties may reduce the computing time by factors of 10 1 to 10 4 , depending on the energy, the degree of parametrization, and the complexity in the material description and the cut off energies in the detailed simulation. To arrive at a high degree of universality, parametrizations of individual electromagnetic showers in homogeneous media are developed, taking the dependence of the shower development on the material into account. In sampling calorimeters, the inhomogeneous material distribution leads to additional effects which can be taken into account by geometry dependent terms in the parametrization of the longitudinal and radial energy density distributions. Comparisons with detailed simulations of homogeneous and sampling calorimeters show very good agreement in the fluctuations, correlations, and signal averages of spatial energy distributions. Verifications of the algorithms for the simulation of the H1 detector are performed using calorimeter test data for different moduls of the H1 liquid argon calorimeter. Special attention has been paid to electron pion separation, which is of great importance for physics analysis. (orig.) [de
The CYGNUS extensive air-shower experiment
Energy Technology Data Exchange (ETDEWEB)
Alexandreas, D.E.; Allen, R.C.; Biller, S.D.; Delay, R.S.; Dion, G.M.; Lu, X.Q.; Vishwanath, P.R.; Yodh, G.B. (Univ. of California, Irvine (United States)); Berley, D.; Chang, C.Y.; Dingus, B.L.; Goodman, J.A.; Haines, T.J.; Gupta, S.; Krakauer, D.A.; Stark, M.J.; Talaga, R.L. (Univ. of Maryland, College Park (United States)); Burman, R.L.; Butterfield, K.; Cady, R.; Hoffman, C.M.; Lloyd-Evans, J.; Nagle, D.E.; Potter, M.E.; Sandberg, V.D.; Sinnis, C.; Stanislaus, S.; Thompson, T.N.; Wilkinson, C.A.; Zhang, W. (Los Alamos National Lab., NM (United States)); Ellsworth, R.W. (George Mason Univ., Fairfax, VA (United States))
1992-01-01
The CYGNUS extensive air-shower experiment is described. The design criteria, construction and operation details, and performance characteristics are presented. A discussion of the data analysis techniques is given. Finally, several enhancements and improvements in the apparatus are described. (orig.).
E143 experiment. Shower counter calibration
International Nuclear Information System (INIS)
Fonvieille, H.; Grenier, P.
1994-01-01
The calibration procedure for the shower counters used in the E143 experiment is described. It has been developed during january 1994 in view of being used for the quick analysis. The method is explained and the results obtained on a given run are presented. (author)
Parton Distributions and the LHC W and Z Production
Martin, A D; Stirling, William James; Thorne, R S
2000-01-01
W and Z bosons will be produced copiously at the LHC proton-proton collider. We study the parton distribution dependence of the total production cross sections and rapidity distributions, paying particular attention to the uncertainties arising from uncertainties in the parton distributions themselves. Variations in the gluon, the strong coupling, the sea quarks and the overall normalisation are shown to lead to small but non-negligible variations in the cross section predictions. Ultimately, therefore, the measurement of these cross sections will provide a powerful cross check on our knowledge of parton distributions and their evolution.
A parton description of the nucleus fragmentation region in heavy-ion collisions
International Nuclear Information System (INIS)
Hwa, R.C.; Oregon Univ., Eugene
1984-01-01
In nucleus-nucleus collisions, the rapidity distribution of partons in the nucleus fragmentation region is highly asymmetrical. Thermalization that randomizes the momenta of partons far apart in rapidity cannot be expected. A local thermalization model is introduced which relates temperature to the range of parton interaction in rapidity. The parton number density and energy density are then calculated. (orig.)
Probing early parton kinetics by photons, dileptons and charm
International Nuclear Information System (INIS)
Kaempfer, B.; Technische Univ. Dresden; Pavlenko, O.P.
1993-07-01
Equilibration processes in pre-equilibrium parton matter are considered. We investigate chemical quark equilibration, partial thermalization and overall thermalization, and their influence on electromagnetic (photons, dileptons) and charmed probes. (orig.)
Generalized parton distributions and transversity from full lattice QCD
Göckeler, M.; Hägler, Ph.; Horsley, R.; Pleiter, D.; Rakow, P. E. L.; Schäfer, A.; Schierholz, G.; Zanotti, J. M.; Qcdsf Collaboration
2005-06-01
We present here the latest results from the QCDSF collaboration for moments of gener- alized parton distributions and transversity in two-flavour QCD, including a preliminary analysis of the pion mass dependence.
Parton distributions andαs for the LHC
International Nuclear Information System (INIS)
Alekhin, S.; Bluemlein, J.; Moch, S.O.; Univ. Hamburg
2013-03-01
We report on recent determinations of NNLO parton distributions and of α s (M Z ) based on the world deep-inelastic data, supplemented by collider data. Some applications are discussed for semi-inclusive processes at the LHC.
Transverse momentum dependent (TMD) parton distribution functions : status and prospects
Angeles-Martinez, R.; Bacchetta, A.; Balitsky, I.I.; Boer, D.; Boglione, M.; Boussarie, R.; Ceccopieri, F.A.; Cherednikov, I.O.; Connor, P.; Echevarria, M. G.; Ferrera, G.; Luyando, J. Grados; Hautmann, F.; Jung, H.; Kasemets, T.; Kutak, K.; Lansberg, J.P.; Lelek, A.; Lykasov, G.; Martinez, J. D. Madrigal; Mulders, P. J.; Nocera, Emanuele R.; Petreska, E.; Pisano, C.; Placakyte, R.; Radescu, V.; Radici, M.; Schnell, G.; Scimemi, I.; Signori, A.; Szymanowski, L.; Monfared, S. Taheri; van der Veken, F.F.; van Haevermaet, H.J.; van Mechelen, P.; Vladimirov, A.; Wallon, S.
2015-01-01
We review transverse momentum dependent (TMD) parton distribution functions, their application to topical issues in high-energy physics phenomenology, and their theoretical connections with QCD resummation, evolution and factorization theorems. We illustrate the use of TMDs via examples of
Nucleon parton distributions in a light-front quark model
International Nuclear Information System (INIS)
Gutsche, Thomas; Lyubovitskij, Valery E.; Schmidt, Ivan
2017-01-01
Continuing our analysis of parton distributions in the nucleon, we extend our light-front quark model in order to obtain both the helicity-independent and the helicity-dependent parton distributions, analytically matching the results of global fits at the initial scale μ∝ 1 GeV; they also contain the correct Dokshitzer-Gribov-Lipatov-Altarelli-Parisi evolution. We also calculate the transverse parton, Wigner and Husimi distributions from a unified point of view, using our light-front wave functions and expressing them in terms of the parton distributions q_v(x) and δq_v(x). Our results are very relevant for the current and future program of the COMPASS experiment at SPS (CERN). (orig.)
Parton model (Moessbauer) sum rules for b → c decays
International Nuclear Information System (INIS)
Lipkin, H.J.
1993-01-01
The parton model is a starting point or zero-order approximation in many treatments. The author follows an approach previously used for the Moessbauer effect and shows how parton model sum rules derived for certain moments of the lepton energy spectrum in b → c semileptonic decays remain valid even when binding effects are included. The parton model appears as a open-quote semiclassical close-quote model whose results for certain averages also hold (correspondence principle) in quantum mechanics. Algebraic techniques developed for the Moessbauer effect exploit simple features of the commutator between the weak current operator and the bound state Hamiltonian to find the appropriate sum rules and show the validity of the parton model in the classical limit, ℎ → 0, where all commutators vanish
Improved quasi parton distribution through Wilson line renormalization
Energy Technology Data Exchange (ETDEWEB)
Chen, Jiunn-Wei [Department of Physics, Center for Theoretical Sciences, and Leung Center for Cosmology and Particle Astrophysics, National Taiwan University, Taipei, 106, Taiwan (China); Center for Theoretical Physics, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Ji, Xiangdong [INPAC, Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai, 200240 (China); Maryland Center for Fundamental Physics, Department of Physics, University of Maryland, College Park, MD 20742 (United States); Zhang, Jian-Hui, E-mail: jianhui.zhang@physik.uni-regensburg.de [Institut für Theoretische Physik, Universität Regensburg, D-93040 Regensburg (Germany)
2017-02-15
Recent developments showed that hadron light-cone parton distributions could be directly extracted from spacelike correlators, known as quasi parton distributions, in the large hadron momentum limit. Unlike the normal light-cone parton distribution, a quasi parton distribution contains ultraviolet (UV) power divergence associated with the Wilson line self energy. We show that to all orders in the coupling expansion, the power divergence can be removed by a “mass” counterterm in the auxiliary z-field formalism, in the same way as the renormalization of power divergence for an open Wilson line. After adding this counterterm, the quasi quark distribution is improved such that it contains at most logarithmic divergences. Based on a simple version of discretized gauge action, we present the one-loop matching kernel between the improved non-singlet quasi quark distribution with a lattice regulator and the corresponding quark distribution in dimensional regularization.
Improved quasi parton distribution through Wilson line renormalization
Directory of Open Access Journals (Sweden)
Jiunn-Wei Chen
2017-02-01
Full Text Available Recent developments showed that hadron light-cone parton distributions could be directly extracted from spacelike correlators, known as quasi parton distributions, in the large hadron momentum limit. Unlike the normal light-cone parton distribution, a quasi parton distribution contains ultraviolet (UV power divergence associated with the Wilson line self energy. We show that to all orders in the coupling expansion, the power divergence can be removed by a “mass” counterterm in the auxiliary z-field formalism, in the same way as the renormalization of power divergence for an open Wilson line. After adding this counterterm, the quasi quark distribution is improved such that it contains at most logarithmic divergences. Based on a simple version of discretized gauge action, we present the one-loop matching kernel between the improved non-singlet quasi quark distribution with a lattice regulator and the corresponding quark distribution in dimensional regularization.
Parton jet fragmentation at small momentum fraction (x)
International Nuclear Information System (INIS)
Kirschner, R.
1984-05-01
The parton fragmentation function is calculated at small x and the angular ordering condition is rederived by extending the method of separation of the softest particle, which is based on unitarity and gauge invariance. (author)
Nucleon parton distributions in a light-front quark model
Energy Technology Data Exchange (ETDEWEB)
Gutsche, Thomas [Universitaet Tuebingen, Institut fuer Theoretische Physik, Kepler Center for Astro and Particle Physics, Tuebingen (Germany); Lyubovitskij, Valery E. [Universitaet Tuebingen, Institut fuer Theoretische Physik, Kepler Center for Astro and Particle Physics, Tuebingen (Germany); Tomsk State University, Department of Physics, Tomsk (Russian Federation); Tomsk Polytechnic University, Laboratory of Particle Physics, Mathematical Physics Department, Tomsk (Russian Federation); Universidad Tecnica Federico Santa Maria, Departamento de Fisica y Centro Cientifico Tecnologico de Valparaiso (CCTVal), Valparaiso (Chile); Schmidt, Ivan [Universidad Tecnica Federico Santa Maria, Departamento de Fisica y Centro Cientifico Tecnologico de Valparaiso (CCTVal), Valparaiso (Chile)
2017-02-15
Continuing our analysis of parton distributions in the nucleon, we extend our light-front quark model in order to obtain both the helicity-independent and the helicity-dependent parton distributions, analytically matching the results of global fits at the initial scale μ∝ 1 GeV; they also contain the correct Dokshitzer-Gribov-Lipatov-Altarelli-Parisi evolution. We also calculate the transverse parton, Wigner and Husimi distributions from a unified point of view, using our light-front wave functions and expressing them in terms of the parton distributions q{sub v}(x) and δq{sub v}(x). Our results are very relevant for the current and future program of the COMPASS experiment at SPS (CERN). (orig.)
Insight into nucleon structure from generalized parton distributions
International Nuclear Information System (INIS)
J.W. Negele; R.C. Brower; P. Dreher; R. Edwards; G. Fleming; Ph. Hagler; Th. Lippert; A.V.Pochinsky; D.B. Renner; D. Richards; K. Schilling; W. Schroers
2004-01-01
The lowest three moments of generalized parton distributions are calculated in full QCD and provide new insight into the behavior of nucleon electromagnetic form factors, the origin of the nucleon spin, and the transverse structure of the nucleon
Study of the partonic structure of the helium nucleus
International Nuclear Information System (INIS)
Perrin, Y.
2012-01-01
The structure of the nucleons and of the nuclei was actively studied during the twentieth century through electron elastic scattering (measuring the electromagnetic form factors) and deep inelastic electron scattering (measuring the parton distributions). The formalism of generalized parton distributions (GPD) achieved the unification of the form factors and the parton distributions. This link gives a source of information about parton dynamics, such as the distribution of nuclear forces and orbital momentum inside hadrons. The easiest experimental access to the GPD is the deeply virtual Compton scattering (DVCS), which corresponds to the hard electroproduction of a real photon. While several experiments focussed on DVCS off the nucleon, only a few experiments studied DVCS off a nuclear target. This thesis deals with the study of the coherent channel of DVCS off helium 4, with the aim of extracting the real and imaginary parts of the Compton form factor thanks to the beam spin asymmetry. (author)
The azimuthal decorrelation of jets widely separated in rapidity
International Nuclear Information System (INIS)
Abbott, B.
1997-11-01
We study the azimuthal decorrelation between jets with pseudorapidity separation up to six units. The data were accumulated using the D0 detector during the 1994-1995 collider run of the Fermilab Tevatron at √s = 1.8 TeV. The data are compared to two parton shower Monte Carlos (HERWIG and PYTHIA) and an analytical prediction using the leading logarithmic BFKL resummation. The final state jets as predicted by the parton showering Monte Carlos describe the data over the entire pseudorapidity range studied. The prediction based on the leading logarithmic BFKL resummation shows more decorrelation than the data as the rapidity interval increases
QCD collinear factorization, its extensions and the partonic distributions
Szymanowski, Lech
2012-01-01
I review the basics of the collinear factorization theorem applied primarily to deep inelastic scattering (DIS) involving forward parton distributions (PDFs) and the extensions of this theorem for exclusive processes probing non-forward parton distributions (GPDs), the generalized distribution amplitudes (GDAs) and the transition distribution amplitudes (TDAs). These QCD factorization theorem is an important tool in the description of hard processes in QCD. Whenever valid, it permits to repre...
Experimental tests of charge symmetry violation in parton distributions
International Nuclear Information System (INIS)
Londergan, J.T.; Murdock, D.P.; Thomas, A.W.
2005-01-01
Recently, a global phenomenological fit to high energy data has included charge symmetry breaking terms, leading to limits on the allowed magnitude of such effects. We discuss two possible experiments that could search for isospin violation in valence parton distributions. We show that, given the magnitude of charge symmetry violation consistent with existing global data, such experiments might expect to see effects at a level of several percent. Alternatively, such experiments could significantly decrease the upper limits on isospin violation in parton distributions
Calculation of parton fragmentation functions from jet calculus: gluon applications
International Nuclear Information System (INIS)
Lassila, K.E.; Ng, A.
1985-01-01
A method is presented for calculation of general parton fragmentation functions based on jet calculus plus meson and baryon wave functions. Results for gluon fragmentation into mesons and baryons are discussed and related to recent information on upsilon decay into gluons. The expressions derived can be used directly in e + e - cross section predictions and will need to be folded in with baryon parton distribution functions when used in p-barp collisions. (author)
QCD next-to-leading-order predictions matched to parton showers for vector-like quark models.
Fuks, Benjamin; Shao, Hua-Sheng
2017-01-01
Vector-like quarks are featured by a wealth of beyond the Standard Model theories and are consequently an important goal of many LHC searches for new physics. Those searches, as well as most related phenomenological studies, however, rely on predictions evaluated at the leading-order accuracy in QCD and consider well-defined simplified benchmark scenarios. Adopting an effective bottom-up approach, we compute next-to-leading-order predictions for vector-like-quark pair production and single production in association with jets, with a weak or with a Higgs boson in a general new physics setup. We additionally compute vector-like-quark contributions to the production of a pair of Standard Model bosons at the same level of accuracy. For all processes under consideration, we focus both on total cross sections and on differential distributions, most these calculations being performed for the first time in our field. As a result, our work paves the way to precise extraction of experimental limits on vector-like quarks thanks to an accurate control of the shapes of the relevant observables and emphasise the extra handles that could be provided by novel vector-like-quark probes never envisaged so far.
QCD next-to-leading order predictions matched to parton showers for vector-like quark models
Fuks, Benjamin
2017-02-27
Vector-like quarks are featured by a wealth of beyond the Standard Model theories and are consequently an important goal of many LHC searches for new physics. Those searches, as well as most related phenomenological studies, however rely on predictions evaluated at the leading-order accuracy in QCD and consider well-defined simplified benchmark scenarios. Adopting an effective bottom-up approach, we compute next-to-leading-order predictions for vector-like-quark pair-production and single production in association with jets, with a weak or with a Higgs boson in a general new physics setup. We additionally compute vector-like-quark contributions to the production of a pair of Standard Model bosons at the same level of accuracy. For all processes under consideration, we focus both on total cross sections and on differential distributions, most these calculations being performed for the first time in our field. As a result, our work paves the way to precise extraction of experimental limits on vector-like quarks...
Parton distributions from SMC and SLAC data
International Nuclear Information System (INIS)
Ramsey, G.P.
1996-01-01
We have extracted spin-weighted parton distributions in a proton from recent data at CERN and SLAC. The valence, sea quark and Antiquark spin-weighted distributions are determined separately. The data are all consistent with a small to moderate polarized gluon distribution, so that the anomaly term is not significant in the determination of the constituent contributions to the spin of the proton. We have analyzed the consistency of the results obtained from various sets of data and the Biorken sum rule. Although all data are consistent with the sum rule, the polarized distributions from different experiments vary, even with higher order QCD corrections taken into account. Results split into two models, one set implying a large polarized strange sea which violates the positivity bound, and the other set yielding a smaller polarized strange sea. Only further experiments which extract information about the polarized sea will reconcile these differences. We suggest specific experiments which can be performed to determine the size of the polarized sea and gluons
Parton distributions for the LHC Run II
Ball, Richard D.; Carrazza, Stefano; Deans, Christopher S.; Del Debbio, Luigi; Forte, Stefano; Guffanti, Alberto; Hartland, Nathan P.; Latorre, José I.; Rojo, Juan; Ubiali, Maria
2015-01-01
We present NNPDF3.0, the first set of parton distribution functions (PDFs) determined with a methodology validated by a closure test. NNPDF3.0 uses a global dataset including HERA-II deep-inelastic inclusive cross-sections, the combined HERA charm data, jet production from ATLAS and CMS, vector boson rapidity and transverse momentum distributions from ATLAS, CMS and LHCb, W+c data from CMS and top quark pair production total cross sections from ATLAS and CMS. Results are based on LO, NLO and NNLO QCD theory and also include electroweak corrections. To validate our methodology, we show that PDFs determined from pseudo-data generated from a known underlying law correctly reproduce the statistical distributions expected on the basis of the assumed experimental uncertainties. This closure test ensures that our methodological uncertainties are negligible in comparison to the generic theoretical and experimental uncertainties of PDF determination. This enables us to determine with confidence PDFs at different pertu...
Tests of gas sampling electromagnetic shower calorimeter
International Nuclear Information System (INIS)
Barbaro-Galtieri, A.; Carithers, W.; Day, C.; Johnson, K.J.; Wenzel, W.A.; Videau, H.
1983-01-01
An electromagnetic shower gas-sampling calorimeter has been tested in both Geiger and proportional discharge modes for incident electron energies in the range 0.125-16 GeV. The 0.2 radiation length-thick layers were lead-fiberglass laminates with cathode strips normal to the sense wires. The 5x10 mm 2 Geiger cells were formed with uniformly spaced nylon fibers perpendicular to the wires. Proportional mode measurements were carried out in the pressure range 1-10 atm. A Monte Carlo simulation is in good agreement with measured shower characteristics and has been used to predict the behavior for oblique of incidence and for various Geiger cell dimensions. (orig.)
Sirunyan, A. M.; Tumasyan, A.; Adam, W.; Asilar, E.; Bergauer, T.; Brandstetter, J.; Brondolin, E.; Dragicevic, M.; Erö, J.; Flechl, M.; Friedl, M.; Frühwirth, R.; Ghete, V. M.; Hartl, C.; Hörmann, N.; Hrubec, J.; Jeitler, M.; König, A.; Krätschmer, I.; Liko, D.; Matsushita, T.; Mikulec, I.; Rabady, D.; Rad, N.; Rahbaran, B.; Rohringer, H.; Schieck, J.; Strauss, J.; Waltenberger, W.; Wulz, C.-E.; Dvornikov, O.; Makarenko, V.; Mossolov, V.; Suarez Gonzalez, J.; Zykunov, V.; Shumeiko, N.; Alderweireldt, S.; De Wolf, E. A.; Janssen, X.; Lauwers, J.; Van De Klundert, M.; Van Haevermaet, H.; Van Mechelen, P.; Van Remortel, N.; Van Spilbeeck, A.; Abu Zeid, S.; Blekman, F.; D'Hondt, J.; Daci, N.; De Bruyn, I.; Deroover, K.; Lowette, S.; Moortgat, S.; Moreels, L.; Olbrechts, A.; Python, Q.; Skovpen, K.; Tavernier, S.; Van Doninck, W.; Van Mulders, P.; Van Parijs, I.; Brun, H.; Clerbaux, B.; De Lentdecker, G.; Delannoy, H.; Fasanella, G.; Favart, L.; Goldouzian, R.; Grebenyuk, A.; Karapostoli, G.; Lenzi, T.; Léonard, A.; Luetic, J.; Maerschalk, T.; Marinov, A.; Randle-conde, A.; Seva, T.; Vander Velde, C.; Vanlaer, P.; Vannerom, D.; Yonamine, R.; Zenoni, F.; Zhang, F.; Cornelis, T.; Dobur, D.; Fagot, A.; Gul, M.; Khvastunov, I.; Poyraz, D.; Salva, S.; Schöfbeck, R.; Tytgat, M.; Van Driessche, W.; Yazgan, E.; Zaganidis, N.; Bakhshiansohi, H.; Bondu, O.; Brochet, S.; Bruno, G.; Caudron, A.; De Visscher, S.; Delaere, C.; Delcourt, M.; Francois, B.; Giammanco, A.; Jafari, A.; Komm, M.; Krintiras, G.; Lemaitre, V.; Magitteri, A.; Mertens, A.; Musich, M.; Piotrzkowski, K.; Quertenmont, L.; Selvaggi, M.; Vidal Marono, M.; Wertz, S.; Beliy, N.; Aldá Júnior, W. L.; Alves, F. L.; Alves, G. A.; Brito, L.; Hensel, C.; Moraes, A.; Pol, M. E.; Rebello Teles, P.; Chagas, E. Belchior Batista Das; Carvalho, W.; Chinellato, J.; Custódio, A.; Da Costa, E. M.; Da Silveira, G. G.; De Jesus Damiao, D.; De Oliveira Martins, C.; De Souza, S. Fonseca; Guativa, L. M. Huertas; Malbouisson, H.; Matos Figueiredo, D.; Mora Herrera, C.; Mundim, L.; Nogima, H.; Prado Da Silva, W. L.; Santoro, A.; Sznajder, A.; Tonelli Manganote, E. J.; Torres Da Silva De Araujo, F.; Vilela Pereira, A.; Ahuja, S.; Bernardes, C. A.; Dogra, S.; Fernandez Perez Tomei, T. R.; Gregores, E. M.; Mercadante, P. G.; Moon, C. S.; Novaes, S. F.; Padula, Sandra S.; Romero Abad, D.; Ruiz Vargas, J. C.; Aleksandrov, A.; Hadjiiska, R.; Iaydjiev, P.; Rodozov, M.; Stoykova, S.; Sultanov, G.; Vutova, M.; Dimitrov, A.; Glushkov, I.; Litov, L.; Pavlov, B.; Petkov, P.; Fang, W.; Ahmad, M.; Bian, J. G.; Chen, G. M.; Chen, H. S.; Chen, M.; Chen, Y.; Cheng, T.; Jiang, C. H.; Leggat, D.; Liu, Z.; Romeo, F.; Ruan, M.; Shaheen, S. M.; Spiezia, A.; Tao, J.; Wang, C.; Wang, Z.; Zhang, H.; Zhao, J.; Ban, Y.; Chen, G.; Li, Q.; Liu, S.; Mao, Y.; Qian, S. J.; Wang, D.; Xu, Z.; Avila, C.; Cabrera, A.; Chaparro Sierra, L. F.; Florez, C.; Gomez, J. P.; González Hernández, C. F.; Ruiz Alvarez, J. D.; Sanabria, J. C.; Godinovic, N.; Lelas, D.; Puljak, I.; Ribeiro Cipriano, P. M.; Sculac, T.; Antunovic, Z.; Kovac, M.; Brigljevic, V.; Ferencek, D.; Kadija, K.; Mesic, B.; Susa, T.; Ather, M. W.; Attikis, A.; Mavromanolakis, G.; Mousa, J.; Nicolaou, C.; Ptochos, F.; Razis, P. A.; Rykaczewski, H.; Finger, M.; Finger, M.; Carrera Jarrin, E.; Ellithi Kamel, A.; Mahmoud, M. A.; Radi, A.; Kadastik, M.; Perrini, L.; Raidal, M.; Tiko, A.; Veelken, C.; Eerola, P.; Pekkanen, J.; Voutilainen, M.; Härkönen, J.; Järvinen, T.; Karimäki, V.; Kinnunen, R.; Lampén, T.; Lassila-Perini, K.; Lehti, S.; Lindén, T.; Luukka, P.; Tuominiemi, J.; Tuovinen, E.; Wendland, L.; Talvitie, J.; Tuuva, T.; Besancon, M.; Couderc, F.; Dejardin, M.; Denegri, D.; Fabbro, B.; Faure, J. L.; Favaro, C.; Ferri, F.; Ganjour, S.; Ghosh, S.; Givernaud, A.; Gras, P.; Hamel de Monchenault, G.; Jarry, P.; Kucher, I.; Locci, E.; Machet, M.; Malcles, J.; Rander, J.; Rosowsky, A.; Titov, M.; Abdulsalam, A.; Antropov, I.; Baffioni, S.; Beaudette, F.; Busson, P.; Cadamuro, L.; Chapon, E.; Charlot, C.; Davignon, O.; Granier de Cassagnac, R.; Jo, M.; Lisniak, S.; Miné, P.; Nguyen, M.; Ochando, C.; Ortona, G.; Paganini, P.; Pigard, P.; Regnard, S.; Salerno, R.; Sirois, Y.; Stahl Leiton, A. G.; Strebler, T.; Yilmaz, Y.; Zabi, A.; Zghiche, A.; Agram, J.-L.; Andrea, J.; Bloch, D.; Brom, J.-M.; Buttignol, M.; Chabert, E. C.; Chanon, N.; Collard, C.; Conte, E.; Coubez, X.; Fontaine, J.-C.; Gelé, D.; Goerlach, U.; Bihan, A.-C. Le; Van Hove, P.; Gadrat, S.; Beauceron, S.; Bernet, C.; Boudoul, G.; Carrillo Montoya, C. A.; Chierici, R.; Contardo, D.; Courbon, B.; Depasse, P.; El Mamouni, H.; Fay, J.; Finco, L.; Gascon, S.; Gouzevitch, M.; Grenier, G.; Ille, B.; Lagarde, F.; Laktineh, I. B.; Lethuillier, M.; Mirabito, L.; Pequegnot, A. L.; Perries, S.; Popov, A.; Sordini, V.; Vander Donckt, M.; Verdier, P.; Viret, S.; Khvedelidze, A.; Lomidze, D.; Autermann, C.; Beranek, S.; Feld, L.; Kiesel, M. K.; Klein, K.; Lipinski, M.; Preuten, M.; Schomakers, C.; Schulz, J.; Verlage, T.; Albert, A.; Brodski, M.; Dietz-Laursonn, E.; Duchardt, D.; Endres, M.; Erdmann, M.; Erdweg, S.; Esch, T.; Fischer, R.; Güth, A.; Hamer, M.; Hebbeker, T.; Heidemann, C.; Hoepfner, K.; Knutzen, S.; Merschmeyer, M.; Meyer, A.; Millet, P.; Mukherjee, S.; Olschewski, M.; Padeken, K.; Pook, T.; Radziej, M.; Reithler, H.; Rieger, M.; Scheuch, F.; Sonnenschein, L.; Teyssier, D.; Thüer, S.; Cherepanov, V.; Flügge, G.; Kargoll, B.; Kress, T.; Künsken, A.; Lingemann, J.; Müller, T.; Nehrkorn, A.; Nowack, A.; Pistone, C.; Pooth, O.; Stahl, A.; Aldaya Martin, M.; Arndt, T.; Asawatangtrakuldee, C.; Beernaert, K.; Behnke, O.; Behrens, U.; Bin Anuar, A. A.; Borras, K.; Campbell, A.; Connor, P.; Contreras-Campana, C.; Costanza, F.; Diez Pardos, C.; Dolinska, G.; Eckerlin, G.; Eckstein, D.; Eichhorn, T.; Eren, E.; Gallo, E.; Garay Garcia, J.; Geiser, A.; Gizhko, A.; Grados Luyando, J. M.; Grohsjean, A.; Gunnellini, P.; Harb, A.; Hauk, J.; Hempel, M.; Jung, H.; Kalogeropoulos, A.; Karacheban, O.; Kasemann, M.; Keaveney, J.; Kleinwort, C.; Korol, I.; Krücker, D.; Lange, W.; Lelek, A.; Lenz, T.; Leonard, J.; Lipka, K.; Lobanov, A.; Lohmann, W.; Mankel, R.; Melzer-Pellmann, I.-A.; Meyer, A. B.; Mittag, G.; Mnich, J.; Mussgiller, A.; Pitzl, D.; Placakyte, R.; Raspereza, A.; Roland, B.; Sahin, M. Ö.; Saxena, P.; Schoerner-Sadenius, T.; Spannagel, S.; Stefaniuk, N.; Van Onsem, G. P.; Walsh, R.; Wissing, C.; Zenaiev, O.; Blobel, V.; Centis Vignali, M.; Draeger, A. R.; Dreyer, T.; Garutti, E.; Gonzalez, D.; Haller, J.; Hoffmann, M.; Junkes, A.; Klanner, R.; Kogler, R.; Kovalchuk, N.; Kurz, S.; Lapsien, T.; Marchesini, I.; Marconi, D.; Meyer, M.; Niedziela, M.; Nowatschin, D.; Pantaleo, F.; Peiffer, T.; Perieanu, A.; Scharf, C.; Schleper, P.; Schmidt, A.; Schumann, S.; Schwandt, J.; Sonneveld, J.; Stadie, H.; Steinbrück, G.; Stober, F. M.; Stöver, M.; Tholen, H.; Troendle, D.; Usai, E.; Vanelderen, L.; Vanhoefer, A.; Vormwald, B.; Akbiyik, M.; Barth, C.; Baur, S.; Baus, C.; Berger, J.; Butz, E.; Caspart, R.; Chwalek, T.; Colombo, F.; De Boer, W.; Dierlamm, A.; Fink, S.; Freund, B.; Friese, R.; Giffels, M.; Gilbert, A.; Goldenzweig, P.; Haitz, D.; Hartmann, F.; Heindl, S. M.; Husemann, U.; Kassel, F.; Katkov, I.; Kudella, S.; Mildner, H.; Mozer, M. U.; Müller, Th.; Plagge, M.; Quast, G.; Rabbertz, K.; Röcker, S.; Roscher, F.; Schröder, M.; Shvetsov, I.; Sieber, G.; Simonis, H. J.; Ulrich, R.; Wayand, S.; Weber, M.; Weiler, T.; Williamson, S.; Wöhrmann, C.; Wolf, R.; Anagnostou, G.; Daskalakis, G.; Geralis, T.; Giakoumopoulou, V. A.; Kyriakis, A.; Loukas, D.; Topsis-Giotis, I.; Kesisoglou, S.; Panagiotou, A.; Saoulidou, N.; Tziaferi, E.; Kousouris, K.; Evangelou, I.; Flouris, G.; Foudas, C.; Kokkas, P.; Loukas, N.; Manthos, N.; Papadopoulos, I.; Paradas, E.; Filipovic, N.; Pasztor, G.; Bencze, G.; Hajdu, C.; Horvath, D.; Sikler, F.; Veszpremi, V.; Vesztergombi, G.; Zsigmond, A. J.; Beni, N.; Czellar, S.; Karancsi, J.; Makovec, A.; Molnar, J.; Szillasi, Z.; Bartók, M.; Raics, P.; Trocsanyi, Z. L.; Ujvari, B.; Komaragiri, J. R.; Bahinipati, S.; Bhowmik, S.; Choudhury, S.; Mal, P.; Mandal, K.; Nayak, A.; Sahoo, D. K.; Sahoo, N.; Swain, S. K.; Bansal, S.; Beri, S. B.; Bhatnagar, V.; Chawla, R.; Bhawandeep, U.; Kalsi, A. K.; Kaur, A.; Kaur, M.; Kumar, R.; Kumari, P.; Mehta, A.; Mittal, M.; Singh, J. B.; Walia, G.; Kumar, Ashok; Bhardwaj, A.; Choudhary, B. C.; Garg, R. 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T.; Meister, D.; Micheli, F.; Musella, P.; Nessi-Tedaldi, F.; Pandolfi, F.; Pata, J.; Pauss, F.; Perrin, G.; Perrozzi, L.; Quittnat, M.; Rossini, M.; Schönenberger, M.; Starodumov, A.; Tavolaro, V. R.; Theofilatos, K.; Wallny, R.; Aarrestad, T. K.; Amsler, C.; Caminada, L.; Canelli, M. F.; De Cosa, A.; Donato, S.; Galloni, C.; Hinzmann, A.; Hreus, T.; Kilminster, B.; Ngadiuba, J.; Pinna, D.; Rauco, G.; Robmann, P.; Salerno, D.; Seitz, C.; Yang, Y.; Zucchetta, A.; Candelise, V.; Doan, T. H.; Jain, Sh.; Khurana, R.; Konyushikhin, M.; Kuo, C. M.; Lin, W.; Pozdnyakov, A.; Yu, S. S.; Kumar, Arun; Chang, P.; Chang, Y. H.; Chao, Y.; Chen, K. F.; Chen, P. H.; Fiori, F.; Hou, W.-S.; Hsiung, Y.; Liu, Y. F.; Lu, R.-S.; Miñano Moya, M.; Paganis, E.; Psallidas, A.; Tsai, J. F.; Asavapibhop, B.; Singh, G.; Srimanobhas, N.; Suwonjandee, N.; Adiguzel, A.; Boran, F.; Cerci, S.; Damarseckin, S.; Demiroglu, Z. S.; Dozen, C.; Dumanoglu, I.; Girgis, S.; Gokbulut, G.; Guler, Y.; Hos, I.; Kangal, E. 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D.; Wang, Q.; Ivanov, A.; Kaadze, K.; Maravin, Y.; Mohammadi, A.; Saini, L. K.; Skhirtladze, N.; Toda, S.; Rebassoo, F.; Wright, D.; Anelli, C.; Baden, A.; Baron, O.; Belloni, A.; Calvert, B.; Eno, S. C.; Ferraioli, C.; Gomez, J. A.; Hadley, N. J.; Jabeen, S.; Jeng, G. Y.; Kellogg, R. G.; Kunkle, J.; Mignerey, A. C.; Ricci-Tam, F.; Shin, Y. H.; Skuja, A.; Tonjes, M. B.; Tonwar, S. C.; Abercrombie, D.; Allen, B.; Apyan, A.; Azzolini, V.; Barbieri, R.; Baty, A.; Bi, R.; Bierwagen, K.; Brandt, S.; Busza, W.; Cali, I. A.; D'Alfonso, M.; Demiragli, Z.; Gomez Ceballos, G.; Goncharov, M.; Hsu, D.; Iiyama, Y.; Innocenti, G. M.; Klute, M.; Kovalskyi, D.; Krajczar, K.; Lai, Y. S.; Lee, Y.-J.; Levin, A.; Luckey, P. D.; Maier, B.; Marini, A. C.; Mcginn, C.; Mironov, C.; Narayanan, S.; Niu, X.; Paus, C.; Roland, C.; Roland, G.; Salfeld-Nebgen, J.; Stephans, G. S. F.; Tatar, K.; Velicanu, D.; Wang, J.; Wang, T. W.; Wyslouch, B.; Benvenuti, A. C.; Chatterjee, R. 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J.; Kellams, N.; Lannon, K.; Marinelli, N.; Meng, F.; Mueller, C.; Musienko, Y.; Planer, M.; Reinsvold, A.; Ruchti, R.; Rupprecht, N.; Smith, G.; Taroni, S.; Wayne, M.; Wolf, M.; Woodard, A.; Alimena, J.; Antonelli, L.; Bylsma, B.; Durkin, L. S.; Flowers, S.; Francis, B.; Hart, A.; Hill, C.; Ji, W.; Liu, B.; Luo, W.; Puigh, D.; Winer, B. L.; Wulsin, H. W.; Cooperstein, S.; Driga, O.; Elmer, P.; Hardenbrook, J.; Hebda, P.; Lange, D.; Luo, J.; Marlow, D.; Medvedeva, T.; Mei, K.; Ojalvo, I.; Olsen, J.; Palmer, C.; Piroué, P.; Stickland, D.; Svyatkovskiy, A.; Tully, C.; Malik, S.; Barker, A.; Barnes, V. E.; Folgueras, S.; Gutay, L.; Jha, M. K.; Jones, M.; Jung, A. W.; Khatiwada, A.; Miller, D. H.; Neumeister, N.; Schulte, J. F.; Shi, X.; Sun, J.; Wang, F.; Xie, W.; Parashar, N.; Stupak, J.; Adair, A.; Akgun, B.; Chen, Z.; Ecklund, K. M.; Geurts, F. J. M.; Guilbaud, M.; Li, W.; Michlin, B.; Northup, M.; Padley, B. 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R.; Faulkner, J.; Gurpinar, E.; Kunori, S.; Lamichhane, K.; Lee, S. W.; Libeiro, T.; Peltola, T.; Undleeb, S.; Volobouev, I.; Wang, Z.; Greene, S.; Gurrola, A.; Janjam, R.; Johns, W.; Maguire, C.; Melo, A.; Ni, H.; Sheldon, P.; Tuo, S.; Velkovska, J.; Xu, Q.; Arenton, M. W.; Barria, P.; Cox, B.; Hirosky, R.; Ledovskoy, A.; Li, H.; Neu, C.; Sinthuprasith, T.; Sun, X.; Wang, Y.; Wolfe, E.; Xia, F.; Clarke, C.; Harr, R.; Karchin, P. E.; Sturdy, J.; Zaleski, S.; Belknap, D. A.; Buchanan, J.; Caillol, C.; Dasu, S.; Dodd, L.; Duric, S.; Gomber, B.; Grothe, M.; Herndon, M.; Hervé, A.; Hussain, U.; Klabbers, P.; Lanaro, A.; Levine, A.; Long, K.; Loveless, R.; Pierro, G. A.; Polese, G.; Ruggles, T.; Savin, A.; Smith, N.; Smith, W. H.; Taylor, D.; Woods, N.
2017-07-01
Normalized double-differential cross sections for top quark pair (t\\overline{t}) production are measured in pp collisions at a centre-of-mass energy of 8 {TeV} with the CMS experiment at the LHC. The analyzed data correspond to an integrated luminosity of 19.7 {fb}^{-1}. The measurement is performed in the dilepton e^{± }μ ^{∓ } final state. The t\\overline{t} cross section is determined as a function of various pairs of observables characterizing the kinematics of the top quark and t\\overline{t} system. The data are compared to calculations using perturbative quantum chromodynamics at next-to-leading and approximate next-to-next-to-leading orders. They are also compared to predictions of Monte Carlo event generators that complement fixed-order computations with parton showers, hadronization, and multiple-parton interactions. Overall agreement is observed with the predictions, which is improved when the latest global sets of proton parton distribution functions are used. The inclusion of the measured t\\overline{t} cross sections in a fit of parametrized parton distribution functions is shown to have significant impact on the gluon distribution.
Energy Technology Data Exchange (ETDEWEB)
Sirunyan, A.M.; Tumasyan, A. [Yerevan Physics Institute, Yerevan (Armenia); Adam, W. [Institut fuer Hochenergiephysik, Vienna (Austria); Collaboration: CMS Collaboration; and others
2017-07-15
Normalized double-differential cross sections for top quark pair (t anti t) production are measured in pp collisions at a centre-of-mass energy of 8 TeV with the CMS experiment at the LHC. The analyzed data correspond to an integrated luminosity of 19.7 fb{sup -1}. The measurement is performed in the dilepton e{sup ±}μ{sup -+} final state. The t anti t cross section is determined as a function of various pairs of observables characterizing the kinematics of the top quark and t anti t system. The data are compared to calculations using perturbative quantum chromodynamics at next-to-leading and approximate next-to-next-to-leading orders. They are also compared to predictions of Monte Carlo event generators that complement fixed-order computations with parton showers, hadronization, and multiple-parton interactions. Overall agreement is observed with the predictions, which is improved when the latest global sets of proton parton distribution functions are used. The inclusion of the measured t anti t cross sections in a fit of parametrized parton distribution functions is shown to have significant impact on the gluon distribution. (orig.)
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Goncharov, M; Hsu, D; Iiyama, Y; Innocenti, G M; Klute, M; Kovalskyi, D; Krajczar, K; Lai, Y S; Lee, Y-J; Levin, A; Luckey, P D; Maier, B; Marini, A C; Mcginn, C; Mironov, C; Narayanan, S; Niu, X; Paus, C; Roland, C; Roland, G; Salfeld-Nebgen, J; Stephans, G S F; Tatar, K; Velicanu, D; Wang, J; Wang, T W; Wyslouch, B; Benvenuti, A C; Chatterjee, R M; Evans, A; Hansen, P; Kalafut, S; Kao, S C; Kubota, Y; Lesko, Z; Mans, J; Nourbakhsh, S; Ruckstuhl, N; Rusack, R; Tambe, N; Turkewitz, J; Acosta, J G; Oliveros, S; Avdeeva, E; Bloom, K; Claes, D R; Fangmeier, C; Gonzalez Suarez, R; Kamalieddin, R; Kravchenko, I; Malta Rodrigues, A; Monroy, J; Siado, J E; Snow, G R; Stieger, B; Alyari, M; Dolen, J; Godshalk, A; Harrington, C; Iashvili, I; Kaisen, J; Nguyen, D; Parker, A; Rappoccio, S; Roozbahani, B; Alverson, G; Barberis, E; Hortiangtham, A; Massironi, A; Morse, D M; Nash, D; Orimoto, T; Teixeira De Lima, R; Trocino, D; Wang, R-J; Wood, D; Bhattacharya, S; Charaf, O; Hahn, K A; Mucia, N; Odell, N; Pollack, B; Schmitt, M H; Sung, K; Trovato, M; Velasco, M; Dev, N; Hildreth, M; Hurtado Anampa, K; Jessop, C; Karmgard, D J; Kellams, N; Lannon, K; Marinelli, N; Meng, F; Mueller, C; Musienko, Y; Planer, M; Reinsvold, A; Ruchti, R; Rupprecht, N; Smith, G; Taroni, S; Wayne, M; Wolf, M; Woodard, A; Alimena, J; Antonelli, L; Bylsma, B; Durkin, L S; Flowers, S; Francis, B; Hart, A; Hill, C; Ji, W; Liu, B; Luo, W; Puigh, D; Winer, B L; Wulsin, H W; Cooperstein, S; Driga, O; Elmer, P; Hardenbrook, J; Hebda, P; Lange, D; Luo, J; Marlow, D; Medvedeva, T; Mei, K; Ojalvo, I; Olsen, J; Palmer, C; Piroué, P; Stickland, D; Svyatkovskiy, A; Tully, C; Malik, S; Barker, A; Barnes, V E; Folgueras, S; Gutay, L; Jha, M K; Jones, M; Jung, A W; Khatiwada, A; Miller, D H; Neumeister, N; Schulte, J F; Shi, X; Sun, J; Wang, F; Xie, W; Parashar, N; Stupak, J; Adair, A; Akgun, B; Chen, Z; Ecklund, K M; Geurts, F J M; Guilbaud, M; Li, W; Michlin, B; Northup, M; Padley, B P; Roberts, J; Rorie, J; Tu, Z; Zabel, J; Betchart, B; Bodek, A; de Barbaro, P; Demina, R; Duh, Y T; Ferbel, T; Galanti, M; Garcia-Bellido, A; Han, J; Hindrichs, O; Khukhunaishvili, A; Lo, K H; Tan, P; Verzetti, M; Agapitos, A; Chou, J P; Gershtein, Y; Gómez Espinosa, T A; Halkiadakis, E; Heindl, M; Hughes, E; Kaplan, S; Kunnawalkam Elayavalli, R; Kyriacou, S; Lath, A; Montalvo, R; Nash, K; Osherson, M; Saka, H; Salur, S; Schnetzer, S; Sheffield, D; Somalwar, S; Stone, R; Thomas, S; Thomassen, P; Walker, M; Delannoy, A G; Foerster, M; Heideman, J; Riley, G; Rose, K; Spanier, S; Thapa, K; Bouhali, O; Celik, A; Dalchenko, M; De Mattia, M; Delgado, A; Dildick, S; Eusebi, R; Gilmore, J; Huang, T; Juska, E; Kamon, T; Mueller, R; Pakhotin, Y; Patel, R; Perloff, A; Perniè, L; Rathjens, D; Safonov, A; Tatarinov, A; Ulmer, K A; Akchurin, N; Damgov, J; De Guio, F; Dragoiu, C; Dudero, P R; Faulkner, J; Gurpinar, E; Kunori, S; Lamichhane, K; Lee, S W; Libeiro, T; Peltola, T; Undleeb, S; Volobouev, I; Wang, Z; Greene, S; Gurrola, A; Janjam, R; Johns, W; Maguire, C; Melo, A; Ni, H; Sheldon, P; Tuo, S; Velkovska, J; Xu, Q; Arenton, M W; Barria, P; Cox, B; Hirosky, R; Ledovskoy, A; Li, H; Neu, C; Sinthuprasith, T; Sun, X; Wang, Y; Wolfe, E; Xia, F; Clarke, C; Harr, R; Karchin, P E; Sturdy, J; Zaleski, S; Belknap, D A; Buchanan, J; Caillol, C; Dasu, S; Dodd, L; Duric, S; Gomber, B; Grothe, M; Herndon, M; Hervé, A; Hussain, U; Klabbers, P; Lanaro, A; Levine, A; Long, K; Loveless, R; Pierro, G A; Polese, G; Ruggles, T; Savin, A; Smith, N; Smith, W H; Taylor, D; Woods, N
2017-01-01
Normalized double-differential cross sections for top quark pair ([Formula: see text]) production are measured in pp collisions at a centre-of-mass energy of 8[Formula: see text] with the CMS experiment at the LHC. The analyzed data correspond to an integrated luminosity of 19.7[Formula: see text]. The measurement is performed in the dilepton [Formula: see text] final state. The [Formula: see text] cross section is determined as a function of various pairs of observables characterizing the kinematics of the top quark and [Formula: see text] system. The data are compared to calculations using perturbative quantum chromodynamics at next-to-leading and approximate next-to-next-to-leading orders. They are also compared to predictions of Monte Carlo event generators that complement fixed-order computations with parton showers, hadronization, and multiple-parton interactions. Overall agreement is observed with the predictions, which is improved when the latest global sets of proton parton distribution functions are used. The inclusion of the measured [Formula: see text] cross sections in a fit of parametrized parton distribution functions is shown to have significant impact on the gluon distribution.
Depth Distribution Of The Maxima Of Extensive Air Shower
Adams, J. H.; Howell, L. W.
2003-01-01
Observations of the extensive air showers from space can be free from interference by low altitude clouds and aerosols if the showers develop at a sufficiently high altitude. In this paper we explore the altitude distribution of shower maxima to determine the fraction of all showers that will reach their maxima at sufficient altitudes to avoid interference from these lower atmosphere phenomena. Typically the aerosols are confined within a planetary boundary layer that extends from only 2-3 km above the Earth's surface. Cloud top altitudes extend above 15 km but most are below 4 km. The results reported here show that more than 75% of the showers that will be observed by EUSO have maxima above the planetary boundary layer. The results also show that more than 50% of the showers that occur on cloudy days have their maxima above the cloud tops.
Spatial structure of extensive air showers near the axis
Energy Technology Data Exchange (ETDEWEB)
Alekseev, E N; Gal' perin, M D; Glemba, P Ya [AN SSSR, Moscow. Inst. Yadernykh Issledovanij; Moskovskij Gosudarstvennyj Univ. (USSR). Nauchno-Issledovatel' skij Inst. Yadernoj Fiziki; Consiglio Nazionale delle Ricerche, Turin (Italy). Lab. di Cosmo-Geofisica)
1978-07-01
The spatial structure of the extensive air showers has been investigated. The tests have been staged on the 400 scintillation counter installation. It has been shown, that spatial distribution of the extensive air showers in the vicinity of the axis does not vary in case of the Nsub(e) electron number showers in the 10/sup 5/-10/sup 6/ range. The share of the showers having a clear-cut multicore structure is approximately 3% with Nsub(e) >= 2x10/sup 5/.
Polarized 3 parton production in inclusive DIS at small x
Energy Technology Data Exchange (ETDEWEB)
Ayala, Alejandro [Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, Apartado Postal 70-543, Ciudad de México 04510 (Mexico); Centre for Theoretical and Mathematical Physics, and Department of Physics, University of Cape Town, Rondebosch 7700 (South Africa); Hentschinski, Martin, E-mail: hentschinski@correo.nucleares.unam.mx [Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, Apartado Postal 70-543, Ciudad de México 04510 (Mexico); Facultad de Ciencias Físico Matemáticas, Benemérita Universidad Autónoma de Puebla, Puebla 1152 (Mexico); Jalilian-Marian, Jamal [Department of Natural Sciences, Baruch College, CUNY, 17 Lexington Avenue, New York, NY 10010 (United States); CUNY Graduate Center, 365 Fifth Avenue, New York, NY 10016 (United States); Tejeda-Yeomans, Maria Elena [Departamento de Física, Universidad de Sonora, Boulevard Luis Encinas J. y Rosales, Colonia Centro, Hermosillo, Sonora 83000 (Mexico)
2016-10-10
Azimuthal angular correlations between produced hadrons/jets in high energy collisions are a sensitive probe of the dynamics of QCD at small x. Here we derive the triple differential cross section for inclusive production of 3 polarized partons in DIS at small x. The target proton or nucleus is described using the Color Glass Condensate (CGC) formalism. The resulting expressions are used to study azimuthal angular correlations between produced partons in order to probe the gluon structure of the target hadron or nucleus. Our analytic expressions can also be used to calculate the real part of the Next to Leading Order (NLO) corrections to di-hadron production in DIS by integrating out one of the three final state partons.
Polarized 3 parton production in inclusive DIS at small x
International Nuclear Information System (INIS)
Ayala, Alejandro; Hentschinski, Martin; Jalilian-Marian, Jamal; Tejeda-Yeomans, Maria Elena
2016-01-01
Azimuthal angular correlations between produced hadrons/jets in high energy collisions are a sensitive probe of the dynamics of QCD at small x. Here we derive the triple differential cross section for inclusive production of 3 polarized partons in DIS at small x. The target proton or nucleus is described using the Color Glass Condensate (CGC) formalism. The resulting expressions are used to study azimuthal angular correlations between produced partons in order to probe the gluon structure of the target hadron or nucleus. Our analytic expressions can also be used to calculate the real part of the Next to Leading Order (NLO) corrections to di-hadron production in DIS by integrating out one of the three final state partons.
Polarized 3 parton production in inclusive DIS at small x
Directory of Open Access Journals (Sweden)
Alejandro Ayala
2016-10-01
Full Text Available Azimuthal angular correlations between produced hadrons/jets in high energy collisions are a sensitive probe of the dynamics of QCD at small x. Here we derive the triple differential cross section for inclusive production of 3 polarized partons in DIS at small x. The target proton or nucleus is described using the Color Glass Condensate (CGC formalism. The resulting expressions are used to study azimuthal angular correlations between produced partons in order to probe the gluon structure of the target hadron or nucleus. Our analytic expressions can also be used to calculate the real part of the Next to Leading Order (NLO corrections to di-hadron production in DIS by integrating out one of the three final state partons.
Reconstruction of Monte Carlo replicas from Hessian parton distributions
Energy Technology Data Exchange (ETDEWEB)
Hou, Tie-Jiun [Department of Physics, Southern Methodist University,Dallas, TX 75275-0181 (United States); Gao, Jun [INPAC, Shanghai Key Laboratory for Particle Physics and Cosmology,Department of Physics and Astronomy, Shanghai Jiao-Tong University, Shanghai 200240 (China); High Energy Physics Division, Argonne National Laboratory,Argonne, Illinois, 60439 (United States); Huston, Joey [Department of Physics and Astronomy, Michigan State University,East Lansing, MI 48824 (United States); Nadolsky, Pavel [Department of Physics, Southern Methodist University,Dallas, TX 75275-0181 (United States); Schmidt, Carl; Stump, Daniel [Department of Physics and Astronomy, Michigan State University,East Lansing, MI 48824 (United States); Wang, Bo-Ting; Xie, Ke Ping [Department of Physics, Southern Methodist University,Dallas, TX 75275-0181 (United States); Dulat, Sayipjamal [Department of Physics and Astronomy, Michigan State University,East Lansing, MI 48824 (United States); School of Physics Science and Technology, Xinjiang University,Urumqi, Xinjiang 830046 (China); Center for Theoretical Physics, Xinjiang University,Urumqi, Xinjiang 830046 (China); Pumplin, Jon; Yuan, C.P. [Department of Physics and Astronomy, Michigan State University,East Lansing, MI 48824 (United States)
2017-03-20
We explore connections between two common methods for quantifying the uncertainty in parton distribution functions (PDFs), based on the Hessian error matrix and Monte-Carlo sampling. CT14 parton distributions in the Hessian representation are converted into Monte-Carlo replicas by a numerical method that reproduces important properties of CT14 Hessian PDFs: the asymmetry of CT14 uncertainties and positivity of individual parton distributions. The ensembles of CT14 Monte-Carlo replicas constructed this way at NNLO and NLO are suitable for various collider applications, such as cross section reweighting. Master formulas for computation of asymmetric standard deviations in the Monte-Carlo representation are derived. A correction is proposed to address a bias in asymmetric uncertainties introduced by the Taylor series approximation. A numerical program is made available for conversion of Hessian PDFs into Monte-Carlo replicas according to normal, log-normal, and Watt-Thorne sampling procedures.
New advances in the statistical parton distributions approach*
Directory of Open Access Journals (Sweden)
Soffer Jacques
2016-01-01
Full Text Available The quantum statistical parton distributions approach proposed more than one decade ago is revisited by considering a larger set of recent and accurate Deep Inelastic Scattering experimental results. It enables us to improve the description of the data by means of a new determination of the parton distributions. This global next-to-leading order QCD analysis leads to a good description of several structure functions, involving unpolarized parton distributions and helicity distributions, in terms of a rather small number of free parameters. There are many serious challenging issues. The predictions of this theoretical approach will be tested for single-jet production and charge asymmetry in W± production in p̄p and pp collisions up to LHC energies, using recent data and also for forthcoming experimental results.
Neural network determination of parton distributions: the nonsinglet case
International Nuclear Information System (INIS)
Del Debbio, Luigi; Forte, Stefano; Latorre, Jose I.; Piccione, Andrea; Rojo, Joan
2007-01-01
We provide a determination of the isotriplet quark distribution from available deep-inelastic data using neural networks. We give a general introduction to the neural network approach to parton distributions, which provides a solution to the problem of constructing a faithful and unbiased probability distribution of parton densities based on available experimental information. We discuss in detail the techniques which are necessary in order to construct a Monte Carlo representation of the data, to construct and evolve neural parton distributions, and to train them in such a way that the correct statistical features of the data are reproduced. We present the results of the application of this method to the determination of the nonsinglet quark distribution up to next-to-next-to-leading order, and compare them with those obtained using other approaches
The breaking of Bjorken scaling in the covariant parton model
International Nuclear Information System (INIS)
Polkinghorne, J.C.
1976-01-01
Scale breaking is investigated in terms of a covariant parton model formulation of deep inelastic processes. It is shown that a consistent theory requires that the convergence properties of parton-hadron amplitudes should be modified as well as the parton being given form factors. Purely logarithmic violation is possible and the resulting model has many features in common with asymtotically free gauge theories. Behaviour at large and small ω and fixed q 2 is investigated. γW 2 should increase with q 2 at large ω and decrease with q 2 at small ω. Heuristic arguments are also given which suggest that the model would only lead to logarithmic modifications of dimensional counting results in purely hadronic deep scattering. (Auth.)
Instanton partons in 5-dimensional SU(N) gauge theory
International Nuclear Information System (INIS)
Bolognesi, Stefano; Lee, Kimyeong
2011-01-01
The circle compactification of the 6-dimensional (2,0) superconformal theory of A N-1 type leads to the 5-dimensional SU(N) maximally supersymmetric gauge theory. Instanton solitons embody Kaluza-Klein modes and are conjectured to be composed of partonic constituents. We realize such a parton of 1/N instanton topological charge at the intersection of magnetic flux sheets. After a further compactification with nontrivial Wilson-line expectation value, instantons or calorons have been shown to be split into fundamental monopoles of fractional instanton charge. In the symmetric phase with trivial Wilson-line expectation value, Bogomol'nyi-Prasad-Sommerfield instanton partons emerge more concretely as non-Abelian Bogomol'nyi-Prasad-Sommerfield monopoles of minimum charge allowed in Dirac quantization.
Unbiased determination of polarized parton distributions and their uncertainties
Ball, Richard D.; Guffanti, Alberto; Nocera, Emanuele R.; Ridolfi, Giovanni; Rojo, Juan
2013-01-01
We present a determination of a set of polarized parton distributions (PDFs) of the nucleon, at next-to-leading order, from a global set of longitudinally polarized deep-inelastic scattering data: NNPDFpol1.0. The determination is based on the NNPDF methodology: a Monte Carlo approach, with neural networks used as unbiased interpolants, previously applied to the determination of unpolarized parton distributions, and designed to provide a faithful and statistically sound representation of PDF uncertainties. We present our dataset, its statistical features, and its Monte Carlo representation. We summarize the technique used to solve the polarized evolution equations and its benchmarking, and the method used to compute physical observables. We review the NNPDF methodology for parametrization and fitting of neural networks, the algorithm used to determine the optimal fit, and its adaptation to the polarized case. We finally present our set of polarized parton distributions. We discuss its statistical properties, ...
QCD's Partner Needed for Mass Spectra and Parton Structure Functions
International Nuclear Information System (INIS)
Kim, Y.S.
2009-01-01
as in the case of the hydrogen atom, bound-state wave functions are needed to generate hadronic spectra. For this purpose, in 1971, Feynman and his students wrote down a Lorentz-invariant harmonic oscillator equation. This differential equation has one set of solutions satisfying the Lorentz-covariant boundary condition. This covariant set generates Lorentz-invariant mass spectra with their degeneracies. Furthermore, the Lorentz-covariant wave functions allow us to calculate the valence parton distribution by Lorentz-boosting the quark-model wave function from the hadronic rest frame. However, this boosted wave function does not give an accurate parton distribution. The wave function needs QCD corrections to make a contact with the real world. Likewise, QCD needs the wave function as a starting point for calculating the parton structure function. (author)
Soft factors for double parton scattering at NNLO
Energy Technology Data Exchange (ETDEWEB)
Vladimirov, Alexey [Institut für Theoretische Physik, Universität Regensburg,D-93040 Regensburg (Germany)
2016-12-13
We show at NNLO that the soft factors for double parton scattering (DPS) for both integrated and unintegrated kinematics, can be presented entirely in the terms of the soft factor for single Drell-Yan process, i.e. the transverse momentum dependent (TMD) soft factor. Using the linearity of the logarithm of TMD soft factor in rapidity divergences, we decompose the DPS soft factor matrices into a product of matrices with rapidity divergences in given sectors, and thus, define individual double parton distributions at NNLO. The rapidity anomalous dimension matrices for double parton distributions are presented in the terms of TMD rapidity anomalous dimension. The analysis is done using the generating function approach to web diagrams. Significant part of the result is obtained from the symmetry properties of web diagrams without referring to explicit expressions or a particular rapidity regularization scheme. Additionally, we present NNLO expression for the web diagram generating function for Wilson lines with two light-like directions.
J/Ψ production in an equilibrating partonic system
International Nuclear Information System (INIS)
Xu, Xiao-Ming
1999-01-01
Any color singlet or octet cc-bar pair is created at short distances and then expands to a full size of J/Ψ. Such a dynamical evolution process is included here in calculations for the J/Ψ number distribution as a function of transverse momentum and rapidity in central Au-Au collisions at both RHIC and LHC energies. The cc-bar pairs are produced in the initial collision and in the partonic system during the prethermal and thermal stages through the partonic channels ab → cc-bar[ 2S+1 L J ] and ab → cc-bar[ 2S+1 L J ]x, and then they dissociate in the latter two stages. Dissociation of cc-bar in the medium occurs via two reactions: (a) color singlet cc-bar plus a gluon turns to color octet cc-bar, (b) color octet cc-bar plus a gluon persists as color octet. There are modest yields of cc-bar in the prethermal stage at RHIC energy and through the reactions ab → cc-bar[ 2S+1 L J ] at LHC energy for partons with large average momentum in the prethermal stage at both collider energies and in the thermal stage at LHC energy. Production from the partonic system competes with the suppression of the initial yield in the deconfined medium. Consequently, a bulge within -1.5 < y < 1.5 has been found for the J/Ψ number distribution and the ratio of J/Ψ number distributions for Au-Au collisions to nucleon-nucleon collisions. This bulge is caused by the partonic system and is thus an indicator of a deconfined partonic medium. Based on this result we suggest the rapidity region worth measuring in future experiments at RHIC and LHC to be -3 < y < 3
Unbiased Polarised Parton Distribution Functions and their Uncertainties
Nocera, Emanuele R.; Ridolfi, Giovanni; Rojo, Juan
2012-01-01
We present preliminary results on the determination of spin-dependent, or polarised, Parton Distribution Functions (PDFs) from all relevant inclusive polarised DIS data. The analysis is performed within the NNPDF approach, which provides a faithful and statistically sound representation of PDFs and their uncertainties. We describe how the NNPDF methodology has been extended to the polarised case, and compare our results with other recent polarised parton sets. We show that polarised PDF uncertainties can be sizeably underestimated in standard determinations, most notably for the gluon.
Renormalization in Large Momentum Effective Theory of Parton Physics.
Ji, Xiangdong; Zhang, Jian-Hui; Zhao, Yong
2018-03-16
In the large-momentum effective field theory approach to parton physics, the matrix elements of nonlocal operators of quark and gluon fields, linked by straight Wilson lines in a spatial direction, are calculated in lattice quantum chromodynamics as a function of hadron momentum. Using the heavy-quark effective theory formalism, we show a multiplicative renormalization of these operators at all orders in perturbation theory, both in dimensional and lattice regularizations. The result provides a theoretical basis for extracting parton properties through properly renormalized observables in Monte Carlo simulations.
The role of the input scale in parton distribution analyses
International Nuclear Information System (INIS)
Jimenez-Delgado, Pedro
2012-01-01
A first systematic study of the effects of the choice of the input scale in global determinations of parton distributions and QCD parameters is presented. It is shown that, although in principle the results should not depend on these choices, in practice a relevant dependence develops as a consequence of what is called procedural bias. This uncertainty should be considered in addition to other theoretical and experimental errors, and a practical procedure for its estimation is proposed. Possible sources of mistakes in the determination of QCD parameter from parton distribution analysis are pointed out.
Chemical and kinetic equilibrations via radiative parton transport
International Nuclear Information System (INIS)
Zhang Bin; Wortman, Warner A
2011-01-01
A hot and dense partonic system can be produced in the early stage of a relativistic heavy ion collision. How it equilibrates is important for the extraction of Quark-Gluon Plasma properties. We study the chemical and kinetic equilibrations of the Quark-Gluon Plasma using a radiative transport model. Thermal and Color-Glass-Condensate motivated initial conditions are used. We observe that screened parton interactions always lead to partial pressure isotropization. Different initial pressure anisotropies result in the same asymptotic evolution. Comparison of evolutions with and without radiative processes shows that chemical equilibration interacts with kinetic equilibration and radiative processes can contribute significantly to pressure isotropization.
Probing lumps of wee partons in deep inelastic scattering
International Nuclear Information System (INIS)
Buchmueller, W.
1994-06-01
Recently, the ZEUS collaboration has reported on several remarkable properties of events with a large rapidity gap in deep inelastic scattering. We suggest that the mechanism underlying these events is the scattering of electrons off lumps of wee partons inside the proton. Based on an effective lagrangian approach the Q 2 -, x- and W-distributions are evaluated. For sufficiently small invariant mass of the detected hadronic system, the mechanism implies leading twist behaviour. The x- and W-distributions are determined by the Lipatov exponent which governs the behaviour of parton densities at small x. (orig.)
Transverse momentum dependent (TMD) parton distribution functions. Status and prospects
International Nuclear Information System (INIS)
Angeles-Martinez, R.; Bacchetta, A.; Pavia Univ.; Balitsky, I.I.
2015-07-01
We provide a concise overview on transverse momentum dependent (TMD) parton distribution functions, their application to topical issues in high-energy physics phenomenology, and their theoretical connections with QCD resummation, evolution and factorization theorems. We illustrate the use of TMDs via examples of multi-scale problems in hadronic collisions. These include transverse momentum q T spectra of Higgs and vector bosons for low q T , and azimuthal correlations in the production of multiple jets associated with heavy bosons at large jet masses. We discuss computational tools for TMDs, and present an application of a new tool, TMDlib, to parton density fits and parameterizations.
Possible signatures of the hadronisation scale in parton jets
International Nuclear Information System (INIS)
Ochs, W.
1987-01-01
Models for hardon production in hard collisions differ widely in the energy scale characteristic of the transition from the primary partonic to the secondary hadronic phase of jet evolution. We investigate possible experimental signatures for the existence of both phases. In particular, we consider multiplicity and energy moments, long range charge correlations and angular correlations as a function of total energy or near the exclusive two body limit in e + e - annihilation and deep inelastic scattering processes. The possibility of a dual correspondence between hadronic and partonic states is discussed. (orig.)
On the use of the KMR unintegrated parton distribution functions
Golec-Biernat, Krzysztof; Staśto, Anna M.
2018-06-01
We discuss the unintegrated parton distribution functions (UPDFs) introduced by Kimber, Martin and Ryskin (KMR), which are frequently used in phenomenological analyses of hard processes with transverse momenta of partons taken into account. We demonstrate numerically that the commonly used differential definition of the UPDFs leads to erroneous results for large transverse momenta. We identify the reason for that, being the use of the ordinary PDFs instead of the cutoff dependent distribution functions. We show that in phenomenological applications, the integral definition of the UPDFs with the ordinary PDFs can be used.
Fractal Dimension of Particle Showers Measured in a Highly Granular Calorimeter
Ruan, Manqi; Bourdy, Vincent; Brients, Jean-Claude; Videau, Henri
2014-01-01
fractal dimension of showers measured in a high granularity calorimeter designed for a future lepton collider. The shower fractal dimension reveals detailed information of the spatial configuration of the shower. It is found to be characteristic of the type of interaction and highly sensitive to the nature of the incident particle. Using the shower fractal dimension, we demonstrate a particle identification algorithm that can efficiently separate electromagnetic showers, hadronic showers and non-showering tracks. We also find a logarithmic dependence of the shower fractal dimension on the particle energy.
Study of final-state radiation in decays of Z bosons produced in pp collisions at 7 TeV
Khachatryan, Vardan; Tumasyan, Armen; Adam, Wolfgang; Bergauer, Thomas; Dragicevic, Marko; Erö, Janos; Friedl, Markus; Fruehwirth, Rudolf; Ghete, Vasile Mihai; Hartl, Christian; Hörmann, Natascha; Hrubec, Josef; Jeitler, Manfred; Kiesenhofer, Wolfgang; Knünz, Valentin; Krammer, Manfred; Krätschmer, Ilse; Liko, Dietrich; Mikulec, Ivan; Rabady, Dinyar; Rahbaran, Babak; Rohringer, Herbert; Schöfbeck, Robert; Strauss, Josef; Treberer-Treberspurg, Wolfgang; Waltenberger, Wolfgang; Wulz, Claudia-Elisabeth; Mossolov, Vladimir; Shumeiko, Nikolai; Suarez Gonzalez, Juan; Alderweireldt, Sara; Bansal, Sunil; Cornelis, Tom; De Wolf, Eddi A; Janssen, Xavier; Knutsson, Albert; Lauwers, Jasper; Luyckx, Sten; Ochesanu, Silvia; Rougny, Romain; Van De Klundert, Merijn; Van Haevermaet, Hans; Van Mechelen, Pierre; Van Remortel, Nick; Van Spilbeeck, Alex; Blekman, Freya; Blyweert, Stijn; D'Hondt, Jorgen; Daci, Nadir; Heracleous, Natalie; Keaveney, James; Lowette, Steven; Maes, Michael; Olbrechts, Annik; Python, Quentin; 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Bunin, Pavel; Gavrilenko, Mikhail; Golutvin, Igor; Gorbunov, Ilya; Kamenev, Alexey; Karjavin, Vladimir; Konoplyanikov, Viktor; Lanev, Alexander; Malakhov, Alexander; Matveev, Viktor; Moisenz, Petr; Palichik, Vladimir; Perelygin, Victor; Shmatov, Sergey; Skatchkov, Nikolai; Smirnov, Vitaly; Zarubin, Anatoli; Golovtsov, Victor; Ivanov, Yury; Kim, Victor; Kuznetsova, Ekaterina; Levchenko, Petr; Murzin, Victor; Oreshkin, Vadim; Smirnov, Igor; Sulimov, Valentin; Uvarov, Lev; Vavilov, Sergey; Vorobyev, Alexey; Vorobyev, Andrey; Andreev, Yuri; Dermenev, Alexander; Gninenko, Sergei; Golubev, Nikolai; Kirsanov, Mikhail; Krasnikov, Nikolai; Pashenkov, Anatoli; Tlisov, Danila; Toropin, Alexander; Epshteyn, Vladimir; Gavrilov, Vladimir; Lychkovskaya, Natalia; Popov, Vladimir; Pozdnyakov, Ivan; Safronov, Grigory; Semenov, Sergey; Spiridonov, Alexander; Stolin, Viatcheslav; Vlasov, Evgueni; Zhokin, Alexander; Andreev, Vladimir; Azarkin, Maksim; Dremin, Igor; Kirakosyan, Martin; Leonidov, Andrey; Mesyats, Gennady; Rusakov, Sergey V; Vinogradov, Alexey; Belyaev, Andrey; Boos, Edouard; Dubinin, Mikhail; Dudko, Lev; Ershov, Alexander; Gribushin, Andrey; Klyukhin, Vyacheslav; Kodolova, Olga; Lokhtin, Igor; Obraztsov, Stepan; Petrushanko, Sergey; Savrin, Viktor; Snigirev, Alexander; Azhgirey, Igor; Bayshev, Igor; Bitioukov, Sergei; Kachanov, Vassili; Kalinin, Alexey; Konstantinov, Dmitri; Krychkine, Victor; Petrov, Vladimir; Ryutin, Roman; Sobol, Andrei; Tourtchanovitch, Leonid; Troshin, Sergey; Tyurin, Nikolay; Uzunian, Andrey; Volkov, Alexey; Adzic, Petar; Ekmedzic, Marko; Milosevic, Jovan; Rekovic, Vladimir; Alcaraz Maestre, Juan; Battilana, Carlo; Calvo, Enrique; Cerrada, Marcos; Chamizo Llatas, Maria; Colino, Nicanor; De La Cruz, Begona; Delgado Peris, Antonio; Domínguez Vázquez, Daniel; Escalante Del Valle, Alberto; Fernandez Bedoya, Cristina; Fernández Ramos, Juan Pablo; Flix, Jose; Fouz, Maria Cruz; Garcia-Abia, Pablo; Gonzalez Lopez, Oscar; Goy Lopez, Silvia; Hernandez, Jose M; Josa, Maria Isabel; Navarro De Martino, Eduardo; Pérez-Calero Yzquierdo, Antonio María; Puerta Pelayo, Jesus; Quintario Olmeda, Adrián; Redondo, Ignacio; Romero, Luciano; Senghi Soares, Mara; Albajar, Carmen; de Trocóniz, Jorge F; Missiroli, Marino; Moran, Dermot; Brun, Hugues; Cuevas, Javier; Fernandez Menendez, Javier; Folgueras, Santiago; Gonzalez Caballero, Isidro; Brochero Cifuentes, Javier Andres; Cabrillo, Iban Jose; Calderon, Alicia; Duarte Campderros, Jordi; Fernandez, Marcos; Gomez, Gervasio; Graziano, Alberto; Lopez Virto, Amparo; Marco, Jesus; Marco, Rafael; Martinez Rivero, Celso; Matorras, Francisco; Munoz Sanchez, Francisca Javiela; Piedra Gomez, Jonatan; Rodrigo, Teresa; Rodríguez-Marrero, Ana Yaiza; Ruiz-Jimeno, Alberto; Scodellaro, Luca; Vila, Ivan; Vilar Cortabitarte, Rocio; Abbaneo, Duccio; Auffray, Etiennette; Auzinger, Georg; Bachtis, Michail; Baillon, Paul; Ball, Austin; Barney, David; Benaglia, Andrea; Bendavid, Joshua; Benhabib, Lamia; Benitez, Jose F; Bloch, Philippe; Bocci, Andrea; Bonato, Alessio; Bondu, Olivier; Botta, Cristina; Breuker, Horst; Camporesi, Tiziano; Cerminara, Gianluca; Colafranceschi, Stefano; D'Alfonso, Mariarosaria; D'Enterria, David; Dabrowski, Anne; David Tinoco Mendes, Andre; De Guio, Federico; De Roeck, Albert; De Visscher, Simon; Di Marco, Emanuele; Dobson, Marc; Dordevic, Milos; Dorney, Brian; Dupont-Sagorin, Niels; Elliott-Peisert, Anna; Franzoni, Giovanni; Funk, Wolfgang; Gigi, Dominique; Gill, Karl; Giordano, Domenico; Girone, Maria; Glege, Frank; Guida, Roberto; Gundacker, Stefan; Guthoff, Moritz; Hammer, Josef; Hansen, Magnus; Harris, Philip; Hegeman, Jeroen; Innocente, Vincenzo; Janot, Patrick; Kousouris, Konstantinos; Krajczar, Krisztian; Lecoq, Paul; Lourenco, Carlos; Magini, Nicolo; Malgeri, Luca; Mannelli, Marcello; Marrouche, Jad; Masetti, Lorenzo; Meijers, Frans; Mersi, Stefano; Meschi, Emilio; Moortgat, Filip; Morovic, Srecko; Mulders, Martijn; Orsini, Luciano; Pape, Luc; Perez, Emmanuelle; Petrilli, Achille; Petrucciani, Giovanni; Pfeiffer, Andreas; Pimiä, Martti; Piparo, Danilo; Plagge, Michael; Racz, Attila; Rolandi, Gigi; Rovere, Marco; Sakulin, Hannes; Schäfer, Christoph; Schwick, Christoph; Sharma, Archana; Siegrist, Patrice; Silva, Pedro; Simon, Michal; Sphicas, Paraskevas; Spiga, Daniele; Steggemann, Jan; Stieger, Benjamin; Stoye, Markus; Takahashi, Yuta; Treille, Daniel; Tsirou, Andromachi; Veres, Gabor Istvan; Wardle, Nicholas; Wöhri, Hermine Katharina; Wollny, Heiner; Zeuner, Wolfram Dietrich; Bertl, Willi; Deiters, Konrad; Erdmann, Wolfram; Horisberger, Roland; Ingram, Quentin; Kaestli, Hans-Christian; Kotlinski, Danek; Langenegger, Urs; Renker, Dieter; Rohe, Tilman; Bachmair, Felix; Bäni, Lukas; Bianchini, Lorenzo; Buchmann, Marco-Andrea; Casal, Bruno; Chanon, Nicolas; Dissertori, Günther; Dittmar, Michael; Donegà, Mauro; Dünser, Marc; Eller, Philipp; Grab, Christoph; Hits, Dmitry; Hoss, Jan; Lustermann, Werner; Mangano, Boris; Marini, Andrea Carlo; Marionneau, Matthieu; Martinez Ruiz del Arbol, Pablo; Masciovecchio, Mario; Meister, Daniel; Mohr, Niklas; Musella, Pasquale; Nägeli, Christoph; Nessi-Tedaldi, Francesca; Pandolfi, Francesco; Pauss, Felicitas; Perrozzi, Luca; Peruzzi, Marco; Quittnat, Milena; Rebane, Liis; Rossini, Marco; Starodumov, Andrei; Takahashi, Maiko; Theofilatos, Konstantinos; Wallny, Rainer; Weber, Hannsjoerg Artur; Amsler, Claude; Canelli, Maria Florencia; Chiochia, Vincenzo; De Cosa, Annapaola; Hinzmann, Andreas; Hreus, Tomas; Kilminster, Benjamin; Lange, Clemens; Ngadiuba, Jennifer; Pinna, Deborah; Robmann, Peter; Ronga, Frederic Jean; Taroni, Silvia; Yang, Yong; Cardaci, Marco; Chen, Kuan-Hsin; Ferro, Cristina; Kuo, Chia-Ming; Lin, Willis; Lu, Yun-Ju; Volpe, Roberta; Yu, Shin-Shan; Chang, Paoti; Chang, You-Hao; Chao, Yuan; Chen, Kai-Feng; Chen, Po-Hsun; Dietz, Charles; Grundler, Ulysses; Hou, George Wei-Shu; Liu, Yueh-Feng; Lu, Rong-Shyang; Miñano Moya, Mercedes; Petrakou, Eleni; Tzeng, Yeng-Ming; Wilken, Rachel; Asavapibhop, Burin; Singh, Gurpreet; Srimanobhas, Norraphat; Suwonjandee, Narumon; Adiguzel, Aytul; Bakirci, Mustafa Numan; Cerci, Salim; Dozen, Candan; Dumanoglu, Isa; Eskut, Eda; Girgis, Semiray; Gokbulut, Gul; Guler, Yalcin; Gurpinar, Emine; Hos, Ilknur; Kangal, Evrim Ersin; Kayis Topaksu, Aysel; Onengut, Gulsen; Ozdemir, Kadri; Ozturk, Sertac; Polatoz, Ayse; Sunar Cerci, Deniz; Tali, Bayram; Topakli, Huseyin; Vergili, Mehmet; Zorbilmez, Caglar; Akin, Ilina Vasileva; Bilin, Bugra; Bilmis, Selcuk; Gamsizkan, Halil; Isildak, Bora; Karapinar, Guler; Ocalan, Kadir; Sekmen, Sezen; Surat, Ugur Emrah; Yalvac, Metin; Zeyrek, Mehmet; Albayrak, Elif Asli; Gülmez, Erhan; Kaya, Mithat; Kaya, Ozlem; Yetkin, Taylan; Cankocak, Kerem; Vardarlı, Fuat Ilkehan; Levchuk, Leonid; Sorokin, Pavel; Brooke, James John; Clement, Emyr; Cussans, David; Flacher, Henning; Goldstein, Joel; Grimes, Mark; Heath, Greg P; Heath, Helen F; Jacob, Jeson; Kreczko, Lukasz; Lucas, Chris; Meng, Zhaoxia; Newbold, Dave M; Paramesvaran, Sudarshan; Poll, Anthony; Sakuma, Tai; Seif El Nasr-storey, Sarah; Senkin, Sergey; Smith, Vincent J; Bell, Ken W; Belyaev, Alexander; Brew, Christopher; Brown, Robert M; Cockerill, David JA; Coughlan, John A; Harder, Kristian; Harper, Sam; Olaiya, Emmanuel; Petyt, David; Shepherd-Themistocleous, Claire; Thea, Alessandro; Tomalin, Ian R; Williams, Thomas; Womersley, William John; Worm, Steven; Baber, Mark; Bainbridge, Robert; Buchmuller, Oliver; Burton, Darren; Colling, David; Cripps, Nicholas; Dauncey, Paul; Davies, Gavin; Della Negra, Michel; Dunne, Patrick; Elwood, Adam; Ferguson, William; Fulcher, Jonathan; Futyan, David; Hall, Geoffrey; Iles, Gregory; Jarvis, Martyn; Karapostoli, Georgia; Kenzie, Matthew; Lane, Rebecca; Lucas, Robyn; Lyons, Louis; Magnan, Anne-Marie; Malik, Sarah; Mathias, Bryn; Nash, Jordan; Nikitenko, Alexander; Pela, Joao; Pesaresi, Mark; Petridis, Konstantinos; Raymond, David Mark; Rogerson, Samuel; Rose, Andrew; Seez, Christopher; Sharp, Peter; Tapper, Alexander; Vazquez Acosta, Monica; Virdee, Tejinder; Zenz, Seth Conrad; Cole, Joanne; Hobson, Peter R; Khan, Akram; Kyberd, Paul; Leggat, Duncan; Leslie, Dawn; Reid, Ivan; Symonds, Philip; Teodorescu, Liliana; Turner, Mark; Dittmann, Jay; Hatakeyama, Kenichi; Kasmi, Azeddine; Liu, Hongxuan; Pastika, Nathaniel; Scarborough, Tara; Wu, Zhenbin; Charaf, Otman; Cooper, Seth; Henderson, Conor; Rumerio, Paolo; Avetisyan, Aram; Bose, Tulika; Fantasia, Cory; Lawson, Philip; Richardson, Clint; Rohlf, James; St John, Jason; Sulak, Lawrence; Alimena, Juliette; Berry, Edmund; Bhattacharya, Saptaparna; Christopher, Grant; Cutts, David; Demiragli, Zeynep; Dhingra, Nitish; Ferapontov, Alexey; Garabedian, Alex; Heintz, Ulrich; Laird, Edward; Landsberg, Greg; Narain, Meenakshi; Sagir, Sinan; Sinthuprasith, Tutanon; Speer, Thomas; Swanson, Joshua; Breedon, Richard; Breto, Guillermo; Calderon De La Barca Sanchez, Manuel; Chauhan, Sushil; Chertok, Maxwell; Conway, John; Conway, Rylan; Cox, Peter Timothy; Erbacher, Robin; Gardner, Michael; Ko, Winston; Lander, Richard; Mulhearn, Michael; Pellett, Dave; 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Barge, Derek; Bradmiller-Feld, John; Campagnari, Claudio; Danielson, Thomas; Dishaw, Adam; Dutta, Valentina; Flowers, Kristen; Franco Sevilla, Manuel; Geffert, Paul; George, Christopher; Golf, Frank; Gouskos, Loukas; Incandela, Joe; Justus, Christopher; Mccoll, Nickolas; Mullin, Sam Daniel; Richman, Jeffrey; Stuart, David; To, Wing; West, Christopher; Yoo, Jaehyeok; Apresyan, Artur; Bornheim, Adolf; Bunn, Julian; Chen, Yi; Duarte, Javier; Mott, Alexander; Newman, Harvey B; Pena, Cristian; Pierini, Maurizio; Spiropulu, Maria; Vlimant, Jean-Roch; Wilkinson, Richard; Xie, Si; Zhu, Ren-Yuan; Azzolini, Virginia; Calamba, Aristotle; Carlson, Benjamin; Ferguson, Thomas; Iiyama, Yutaro; Paulini, Manfred; Russ, James; Vogel, Helmut; Vorobiev, Igor; Cumalat, John Perry; Ford, William T; Gaz, Alessandro; Krohn, Michael; Luiggi Lopez, Eduardo; Nauenberg, Uriel; Smith, James; Stenson, Kevin; Wagner, Stephen Robert; Alexander, James; Chatterjee, Avishek; Chaves, Jorge; Chu, Jennifer; Dittmer, Susan; Eggert, Nicholas; Mirman, Nathan; Nicolas Kaufman, Gala; Patterson, Juliet Ritchie; Ryd, Anders; Salvati, Emmanuele; Skinnari, Louise; Sun, Werner; Teo, Wee Don; Thom, Julia; Thompson, Joshua; Tucker, Jordan; Weng, Yao; Winstrom, Lucas; Wittich, Peter; Winn, Dave; Abdullin, Salavat; Albrow, Michael; Anderson, Jacob; Apollinari, Giorgio; Bauerdick, Lothar AT; Beretvas, Andrew; Berryhill, Jeffrey; Bhat, Pushpalatha C; Bolla, Gino; Burkett, Kevin; Butler, Joel Nathan; Cheung, Harry; Chlebana, Frank; Cihangir, Selcuk; Elvira, Victor Daniel; Fisk, Ian; Freeman, Jim; Gottschalk, Erik; Gray, Lindsey; Green, Dan; Grünendahl, Stefan; Gutsche, Oliver; Hanlon, Jim; Hare, Daryl; Harris, Robert M; Hirschauer, James; Hooberman, Benjamin; Jindariani, Sergo; Johnson, Marvin; Joshi, Umesh; Klima, Boaz; Kreis, Benjamin; Kwan, Simon; Linacre, Jacob; Lincoln, Don; Lipton, Ron; Liu, Tiehui; Lopes De Sá, Rafael; Lykken, Joseph; Maeshima, Kaori; Marraffino, John Michael; Martinez Outschoorn, Verena Ingrid; Maruyama, Sho; 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Verzetti, Mauro; Vishnevskiy, Dmitry; Ciesielski, Robert; Demortier, Luc; Goulianos, Konstantin; Mesropian, Christina; Arora, Sanjay; Barker, Anthony; Chou, John Paul; Contreras-Campana, Christian; Contreras-Campana, Emmanuel; Duggan, Daniel; Ferencek, Dinko; Gershtein, Yuri; Gray, Richard; Halkiadakis, Eva; Hidas, Dean; Kaplan, Steven; Lath, Amitabh; Panwalkar, Shruti; Park, Michael; Salur, Sevil; Schnetzer, Steve; Sheffield, David; Somalwar, Sunil; Stone, Robert; Thomas, Scott; Thomassen, Peter; Walker, Matthew; Rose, Keith; Spanier, Stefan; York, Andrew; Bouhali, Othmane; Castaneda Hernandez, Alfredo; Dildick, Sven; Eusebi, Ricardo; Flanagan, Will; Gilmore, Jason; Kamon, Teruki; Khotilovich, Vadim; Krutelyov, Vyacheslav; Montalvo, Roy; Osipenkov, Ilya; Pakhotin, Yuriy; Patel, Rishi; Perloff, Alexx; Roe, Jeffrey; Rose, Anthony; Safonov, Alexei; Suarez, Indara; Tatarinov, Aysen; Ulmer, Keith; Akchurin, Nural; Cowden, Christopher; Damgov, Jordan; Dragoiu, Cosmin; Dudero, Phillip Russell; Faulkner, James; Kovitanggoon, Kittikul; Kunori, Shuichi; Lee, Sung Won; Libeiro, Terence; Volobouev, Igor; Appelt, Eric; Delannoy, Andrés G; Greene, Senta; Gurrola, Alfredo; Johns, Willard; Maguire, Charles; Mao, Yaxian; Melo, Andrew; Sharma, Monika; Sheldon, Paul; Snook, Benjamin; Tuo, Shengquan; Velkovska, Julia; Arenton, Michael Wayne; Boutle, Sarah; Cox, Bradley; Francis, Brian; Goodell, Joseph; Hirosky, Robert; Ledovskoy, Alexander; Li, Hengne; Lin, Chuanzhe; Neu, Christopher; Wolfe, Evan; Wood, John; Clarke, Christopher; Harr, Robert; Karchin, Paul Edmund; Kottachchi Kankanamge Don, Chamath; Lamichhane, Pramod; Sturdy, Jared; Belknap, Donald; Carlsmith, Duncan; Cepeda, Maria; Dasu, Sridhara; Dodd, Laura; Duric, Senka; Friis, Evan; Hall-Wilton, Richard; Herndon, Matthew; Hervé, Alain; Klabbers, Pamela; Lanaro, Armando; Lazaridis, Christos; Levine, Aaron; Loveless, Richard; Mohapatra, Ajit; Ojalvo, Isabel; Perry, Thomas; Pierro, Giuseppe Antonio; Polese, Giovanni; Ross, Ian; Sarangi, Tapas; Savin, Alexander; Smith, Wesley H; Taylor, Devin; Vuosalo, Carl; Woods, Nathaniel
2015-05-29
The differential cross sections for the production of photons in $\\mathrm{Z} \\to \\mu^+ \\mu^- \\gamma$ decays are presented as a function of the transverse energy of the photon and its separation from the nearest muon. The data for these measurements were collected with the CMS detector and correspond to an integrated luminosity of 4.7 fb$^{-1}$ of pp collisions at $\\sqrt{s}$ = 7 TeV delivered by the CERN LHC. The cross sections are compared to simulations with POWHEG and PYTHIA, where PYTHIA is used to simulate parton showers and final-state photons. These simulations match the data to better than 5%.
Cosmic ray air showers in the knee energy region
Indian Academy of Sciences (India)
The cosmic ray extensive air showers in the knee energy region have been studied by the North Bengal University array. The differential size spectra at different atmospheric depths show a systematic shift of the knee towards smaller shower size with the increase in atmospheric depth. The measured values of spectral ...
New shower maximum trigger for electrons and photons at CDF
International Nuclear Information System (INIS)
Amidei, D.; Burkett, K.; Gerdes, D.; Miao, C.; Wolinski, D.
1994-01-01
For the 1994 Tevatron collider run, CDF has upgraded the electron and photo trigger hardware to make use of shower position and size information from the central shower maximum detector. For electrons, the upgrade has resulted in a 50% reduction in backgrounds while retaining approximately 90% of the signal. The new trigger also eliminates the background to photon triggers from single-phototube spikes
New shower maximum trigger for electrons and photons at CDF
International Nuclear Information System (INIS)
Gerdes, D.
1994-08-01
For the 1994 Tevatron collider run, CDF has upgraded the electron and photon trigger hardware to make use of shower position and size information from the central shower maximum detector. For electrons, the upgrade has resulted in a 50% reduction in backgrounds while retaining approximately 90% of the signal. The new trigger also eliminates the background to photon triggers from single-phototube discharge
The Geant4-Based ATLAS Fast Electromagnetic Shower Simulation
Barberio, E; Butler, B; Cheung, S L; Dell'Acqua, A; Di Simone, A; Ehrenfeld, W; Gallas, M V; Glasow, A; Hughes, E; Marshall, Z; Müller, J; Placakyte, R; Rimoldi, A; Savard, P; Tsulaia, V; Waugh, A; Young, C C; 10th ICATPP Conference on Astroparticle, Particle, Space Physics, Detectors and Medical Physics Applications
2008-01-01
We present a three-pronged approach to fast electromagnetic shower simulation in ATLAS. Parameterisation is used for high-energy, shower libraries for medium-energy, and an averaged energy deposition for very low-energy particles. We present a comparison between the fast simulation and full simulation in an ATLAS Monte Carlo production.
Air shower detection and the energy flow in electromagnetic cascades
Energy Technology Data Exchange (ETDEWEB)
Stanev, Todor (Nuclear Power Oversight Committee (United States)); Vankov, H.P. (Bylgarska Akademiya na Naukite, Sofia (Bulgaria). Inst. za Yadrena Izsledvaniya i Yadrena Energetika)
1992-02-01
We study the longitudinal behaviour of the energy carried by the shower particles E{sub c} and its lateral distribution, give simple parametrizations of the results of Monte Carlo simulations, and discuss the advantages of shower detectors that measure directly E{sub c}. (author).
JASA: A prototype water-Cerenkov air-shower detector
International Nuclear Information System (INIS)
Berley, D.; Dion, C.; Goodman, J.A.; Haines, T.J.; Kwok, P.W.; Stark, M.J.; Svoboda, R.C.; Ferguson, H.; Hoffman, C.M.; Horch, E.; Ellsworth, R.W.; Delay, R.S.; Lu, X.; Yodh, G.B.
1991-01-01
A small pilot experiment to examine the use of the water-Cerenkov technique for air shower detection was installed near the center of the CYGNUS air shower array. Preliminary results showing general agreement with simulations are presented. Thus, the technique promises to offer significant advances for VHE-UHE γ-ray astronomy
Testing the Effectiveness of Therapeutic Showering in Labor.
Stark, Mary Ann
: Therapeutic showering is a holistic nursing intervention that is often available and supports physiologic labor. The purpose of this study was to compare the effectiveness of therapeutic showering with usual care during active labor. Research questions were as follows: Are there significant differences between women who showered 30 minutes during active labor and those who received usual labor care in anxiety, tension, relaxation, pain, discomfort, and coping? Is there a difference in use of obstetric interventions between groups? A convenience sample of healthy low-risk women in active labor was recruited (N = 32). A pretest posttest control group repeated-measures design was used. Participants were randomized to treatment group (n = 17), who showered for 30 minutes, or to control group (n = 14) who received usual labor care. Women evaluated pain, discomfort, anxiety, tension, coping, and relaxation at enrollment, again 15 minutes after entering the shower or receiving usual care, then again 30 minutes after entering the shower or receiving usual care. Chart reviews after delivery recorded obstetric interventions. The showering group had statistically significant decreases in pain, discomfort, anxiety and tension, and significant increase in relaxation. There were no differences in use of obstetric interventions. Therapeutic showering was effective in reducing pain, discomfort, anxiety, and tension while improving relaxation and supporting labor in this sample.
Hadron shower profile and direction measurements in a segmented calorimeter
International Nuclear Information System (INIS)
Auchincloss, P.; Blair, R.; Haber, C.
1982-01-01
Recently a test measurement was made to see how well the direction of the shower induced by neutrino interactions could be determined in the lab-E detector at Fermilab. While the calorimeter in lab-E has very coarse sampling compared to the detectors described at this workshop, the method used to sample the shower could be employed in other more finely segmented detectors. The shower angle resolution obtained (36 mr.FWHM) is largely constrained by the sampling. In this test pulse heights in 2mm. steps across the hadron shower at five points along the shower were recorded. This was done with 20 wires and 20 fast ADC's. A standard MWPC system intended to accomplish the same task would have required about 250 wires and 250 ADC channels. This considerable saving in system complexity should be possible for any system where finely segmented pulse height measurements are required
Underlying event sensitive observables in Drell-Yan production using GENEVA
Alioli, Simone; Guns, Sam; Tackmann, Frank J.
2016-11-09
We present an extension of the GENEVA Monte Carlo framework to include multiple parton interactions (MPI) provided by PYTHIA8. This allows us to obtain predictions for underlying-event sensitive measurements in Drell-Yan production, in conjunction with GENEVA's fully-differential NNLO calculation, NNLL' resummation for the 0-jet resolution variable (beam thrust), and NLL resummation for the 1-jet resolution variable. We describe the interface with the parton shower algorithm and MPI model of PYTHIA8, which preserves both the precision of partonic N-jet cross sections in GENEVA as well as the shower accuracy and good description of soft hadronic physics of PYTHIA8. We present results for several underlying-event sensitive observables and compare to data from ATLAS and CMS as well as to standalone PYTHIA8 predictions. This includes a comparison with the recent ATLAS measurement of the beam thrust spectrum, which provides a potential avenue to fully disentangle the physical effects from the primary hard interact...
Wee partons in large nuclei: from virtual dream to hard reality
International Nuclear Information System (INIS)
Venugopalan, R.
1995-01-01
We construct a weak coupling, many body theory to compute parton distributions in large nuclei for x -1/3 . The wee partons are highly coherent, non-Abelian Weizsaecker-Williams fields. Radiative corrections to the classical results are discussed. The parton distributions for a single nucleus provide the initial conditions for the dynamical evolution of matter formed in ultrarelativistic nuclear collisions. (orig.)
Global study of nuclear modifications on parton distribution functions
Directory of Open Access Journals (Sweden)
Rong Wang
2017-07-01
Full Text Available A global analysis of nuclear medium modifications of parton distributions is presented using deeply inelastic scattering data of various nuclear targets. Two obtained data sets are provided for quark and gluon nuclear modification factors, referred as nIMParton16. One is from the global fit only to the experimental data of isospin-scalar nuclei (Set A, and the other is from the fit to all the measured nuclear data (Set B. The scale-dependence is described by DGLAP equations with nonlinear corrections in this work. The Fermi motion and off-shell effect, nucleon swelling, and parton–parton recombination are taken into account together for modeling the complicated x-dependence of nuclear modification. The nuclear gluon shadowing in this paper is dynamically generated by the QCD evolution of parton splitting and recombination processes with zero gluon density at the input scale. Sophisticated nuclear dependence of nuclear medium effects is studied with only two free parameters. With the obtained free parameters from the global analysis, the nuclear modifications of parton distribution functions of unmeasured nuclei can be predicted in our model. Nuclear modification of deuteron is also predicted and shown with recent measurement at JLab.
Parton degrees of freedom from the path-integral formalism
International Nuclear Information System (INIS)
Liu, Keh-Fei
2000-01-01
We formulate the hadronic tensor W μν of deep inelastic scattering in the path-integral formalism. It is shown that there are 3 gauge invariant and topologically distinct contributions. In addition to the valence contribution, there are two sources for the sea--one in the connected insertion and the other in the disconnected insertion. The operator product expansion is carried out in this formalism. The operator rescaling and mixing reveal that the connected sea partons evolve the same way as the valence; i.e., their evolution is decoupled from the disconnected sea and the gluon distribution functions. We explore the phenomenological consequences of this classification in terms of the small x behavior, Gottfried sum rule violation, and flavor dependence. In particular, we point out that in the nucleon u(bar sign) and d(bar sign) partons have both connected and disconnected sea contributions, whereas the s(bar sign) parton has only the disconnected sea contribution. This difference between u(bar sign)+d(bar sign) and s(bar sign), as far as we know, has not been taken into account in the fitting of parton distribution functions to experiments. (c) 2000 The American Physical Society
Unbiased determination of polarized parton distributions and their uncertainties
Energy Technology Data Exchange (ETDEWEB)
Ball, Richard D. [Tait Institute, University of Edinburgh, JCMB, KB, Mayfield Rd, Edinburgh EH9 3JZ, Scotland (United Kingdom); Forte, Stefano, E-mail: forte@mi.infn.it [Dipartimento di Fisica, Università di Milano and INFN, Sezione di Milano, Via Celoria 16, I-20133 Milano (Italy); Guffanti, Alberto [The Niels Bohr International Academy and Discovery Center, The Niels Bohr Institute, Blegdamsvej 17, DK-2100 Copenhagen (Denmark); Nocera, Emanuele R. [Dipartimento di Fisica, Università di Milano and INFN, Sezione di Milano, Via Celoria 16, I-20133 Milano (Italy); Ridolfi, Giovanni [Dipartimento di Fisica, Università di Genova and INFN, Sezione di Genova, Genova (Italy); Rojo, Juan [PH Department, TH Unit, CERN, CH-1211 Geneva 23 (Switzerland)
2013-09-01
We present a determination of a set of polarized parton distributions (PDFs) of the nucleon, at next-to-leading order, from a global set of longitudinally polarized deep-inelastic scattering data: NNPDFpol1.0. The determination is based on the NNPDF methodology: a Monte Carlo approach, with neural networks used as unbiased interpolants, previously applied to the determination of unpolarized parton distributions, and designed to provide a faithful and statistically sound representation of PDF uncertainties. We present our dataset, its statistical features, and its Monte Carlo representation. We summarize the technique used to solve the polarized evolution equations and its benchmarking, and the method used to compute physical observables. We review the NNPDF methodology for parametrization and fitting of neural networks, the algorithm used to determine the optimal fit, and its adaptation to the polarized case. We finally present our set of polarized parton distributions. We discuss its statistical properties, test for its stability upon various modifications of the fitting procedure, and compare it to other recent polarized parton sets, and in particular obtain predictions for polarized first moments of PDFs based on it. We find that the uncertainties on the gluon, and to a lesser extent the strange PDF, were substantially underestimated in previous determinations.
Unbiased determination of polarized parton distributions and their uncertainties
International Nuclear Information System (INIS)
Ball, Richard D.; Forte, Stefano; Guffanti, Alberto; Nocera, Emanuele R.; Ridolfi, Giovanni; Rojo, Juan
2013-01-01
We present a determination of a set of polarized parton distributions (PDFs) of the nucleon, at next-to-leading order, from a global set of longitudinally polarized deep-inelastic scattering data: NNPDFpol1.0. The determination is based on the NNPDF methodology: a Monte Carlo approach, with neural networks used as unbiased interpolants, previously applied to the determination of unpolarized parton distributions, and designed to provide a faithful and statistically sound representation of PDF uncertainties. We present our dataset, its statistical features, and its Monte Carlo representation. We summarize the technique used to solve the polarized evolution equations and its benchmarking, and the method used to compute physical observables. We review the NNPDF methodology for parametrization and fitting of neural networks, the algorithm used to determine the optimal fit, and its adaptation to the polarized case. We finally present our set of polarized parton distributions. We discuss its statistical properties, test for its stability upon various modifications of the fitting procedure, and compare it to other recent polarized parton sets, and in particular obtain predictions for polarized first moments of PDFs based on it. We find that the uncertainties on the gluon, and to a lesser extent the strange PDF, were substantially underestimated in previous determinations
On neutrino and antineutrino scattering by electrons, and by partons
Bell, J S
1975-01-01
Assuming a non-derivative point interaction, and Born approximation, there are some simple relations between neutrino and antineutrino scattering on electrons or partons. They have been observed already, for some special cases, in the results of explicit calculations. Here they are obtained from simple and general considerations. (8 refs).
Parton Distributions at a 100 TeV Hadron Collider
Rojo, Juan
2016-01-01
The determination of the parton distribution functions (PDFs) of the proton will be an essential input for the physics program of a future 100 TeV hadron collider. The unprecedented center-of-mass energy will require knowledge of PDFs in currently unexplored kinematical regions such as the ultra
Spin-dependent parton distributions and structure functions
International Nuclear Information System (INIS)
Bentz, W.; Ito, T.; Cloet, I.C.; Thomas, A.W.; Yazaki, K.
2008-01-01
Nuclear parton distributions and structure functions are determined in an effective chiral quark theory. We also discuss an extension of our model to fragmentation functions. Presented at the 20th Few-Body Conference, Pisa, Italy, 10-14 September 2007. (author)
Probing the partonic structure of exotic particles in hard electroproduction
International Nuclear Information System (INIS)
Anikin, I.V.; Pire, B.; Szymanowski, L.; Teryaev, O.V.; Wallon, S.
2005-01-01
We argue that the electroproduction of exotic particles is a useful tool for study of their partonic structure. In the case of hybrid mesons, the magnitude of their cross sections shows that they are accessible for measurements in existing electroproduction experiments
Diffraction scattering and the parton model in QCD
International Nuclear Information System (INIS)
White, A.
1985-01-01
Arguments are presented that the validity of the parton model for hadron scattering in QCD is directly related to the occurrence of the Critical Pomeron description of diffraction scattering. An attractive route suggested for Electroweak and Grand Unification is also briefly described
The QCD coupling and parton distributions at high precision
International Nuclear Information System (INIS)
Bluemlein, Johannes
2010-07-01
A survey is given on the present status of the nucleon parton distributions and related precision calculations and precision measurements of the strong coupling constant α s (M 2 Z ). We also discuss the impact of these quantities on precision observables at hadron colliders. (orig.)
The QCD coupling and parton distributions at high precision
Energy Technology Data Exchange (ETDEWEB)
Bluemlein, Johannes
2010-07-15
A survey is given on the present status of the nucleon parton distributions and related precision calculations and precision measurements of the strong coupling constant {alpha}{sub s}(M{sup 2}{sub Z}). We also discuss the impact of these quantities on precision observables at hadron colliders. (orig.)
Extent of sensitivity of single photon production to parton distribution ...
Indian Academy of Sciences (India)
used the BFG-I parton to photon fragmentation function by Bourhis et al [17], which includes correction in the fragmentation function beyond leading logarithmic approxima- tion. The three scales μf,μR,μF are set equal to a common scale μ to reduce theoretical uncertainties in the calculation. The scale μ is further defined as ...
Spin structure at the partonic level. Pt. 2
International Nuclear Information System (INIS)
Leader, E.
1983-01-01
Knowledge of the spin and momentum distribution of partons inside a polarised nucleon, as deduced from lepton scattering, is combined with lowest order QCD to calculate spin dependent parameters in large psub(T) hadronic reactions. Clear predictions emerge in some cases and are in conflict with present experimental results. There is a real challenge to improve both theory and experiment. (orig.)
Parton distributions and{alpha}{sub s} for the LHC
Energy Technology Data Exchange (ETDEWEB)
Alekhin, S. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany); Institut Fiziki Vysokikh Ehnergij, Protvino (Russian Federation); Bluemlein, J. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany); Moch, S.O. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany); Univ. Hamburg (Germany). 2. Inst fuer Theoretische Physik
2013-03-15
We report on recent determinations of NNLO parton distributions and of {alpha}{sub s}(M{sub Z}) based on the world deep-inelastic data, supplemented by collider data. Some applications are discussed for semi-inclusive processes at the LHC.
PARTON SATURATION, PRODUCTION, AND EQUILIBRATION IN HIGH ENERGY NUCLEAR COLLISIONS
International Nuclear Information System (INIS)
VENUGOPALAN, R.
1999-01-01
Deeply inelastic scattering of electrons off nuclei can determine whether parton distributions saturate at HERA energies. If so, this phenomenon will also tell us a great deal about how particles are produced, and whether they equilibrate, in high energy nuclear collisions
Comparative study of the uncertainties in parton distribution functions
International Nuclear Information System (INIS)
Alekhin, S.I.
2003-01-01
Comparison of the methods used to extract the uncertainties in parton distributions is given, including their statistical properties and practical issues of implementation. Advantages and disadvantages of different methods are illustrated using the examples based on the analysis of real data. Available PDFs sets with associated uncertainties are reviewed and critically compared
Nuclear physics aspects in the parton model of Feynman
International Nuclear Information System (INIS)
Pauchy Hwang, W.Y.
1995-01-01
The basic fact that pions couple strongly to nucleons has dominated various nuclear physics thinkings since the birth of the field more than sixty years ago. The parton model of Feynman, in which the structure of a nucleon (or a hadron) is characterized by a set of parton distributions, was proposed originally in late 1960's to treat high energy deep inelastic scattering, and later many other high energy physics experiments involving hadrons. Introduction of the concept of parton distributions signifies the departure of particle physics from nuclear physics. Following the suggestion that the sea quark distributions in a nucleon, at low and moderate Q 2 (at least up to a few GeV 2 ), can be attributed primarily to the probability of finding such quarks or antiquarks in the mesons (or recoiling baryons) associated with the nucleon, the author examines how nuclear physics aspects offer quantitative understanding of several recent experimental results, including the observed violation of the Gotfried sum rule and the so-called open-quotes proton spin crisisclose quotes. These results suggest that determination of parton distributions of a hadron at Q 2 of a few GeV 2 (and at small x) must in general take into account nuclear physics aspects. Implication of these results for other high-energy reactions, such as semi-inclusive hadron production in deep inelastic scattering, are also discussed
On neutrino and antineutrino scattering by electrons, and by partons
International Nuclear Information System (INIS)
Bell, J.S.; Dass, G.V.
1975-09-01
Assuming a non-derivative point interaction, and Born approximation, there are some simple relations between neutrino and antineutrino scattering on electrons or partons. They have been observed already, for some special cases, in the results of explicit calculations. Here they are obtained from simple general considerations. (author)
A determination of parton distributions with faithful uncertainty estimation
International Nuclear Information System (INIS)
Ball, Richard D.; Del Debbio, Luigi; Forte, Stefano; Guffanti, Alberto; Latorre, Jose I.; Piccione, Andrea; Rojo, Juan; Ubiali, Maria
2009-01-01
We present the determination of a set of parton distributions of the nucleon, at next-to-leading order, from a global set of deep-inelastic scattering data: NNPDF1.0. The determination is based on a Monte Carlo approach, with neural networks used as unbiased interpolants. This method, previously discussed by us and applied to a determination of the nonsinglet quark distribution, is designed to provide a faithful and statistically sound representation of the uncertainty on parton distributions. We discuss our dataset, its statistical features, and its Monte Carlo representation. We summarize the technique used to solve the evolution equations and its benchmarking, and the method used to compute physical observables. We discuss the parametrization and fitting of neural networks, and the algorithm used to determine the optimal fit. We finally present our set of parton distributions. We discuss its statistical properties, test for its stability upon various modifications of the fitting procedure, and compare it to other recent parton sets. We use it to compute the benchmark W and Z cross sections at the LHC. We discuss issues of delivery and interfacing to commonly used packages such as LHAPDF
Czech Academy of Sciences Publication Activity Database
Abdallah, J.; Abreu, A.; Adam, W.; Mašík, Jiří; Němeček, Stanislav; Řídký, Jan; Todorovová, Šárka; Trávníček, Petr; Vrba, Václav
2011-01-01
Roč. 71, č. 2 (2011), 1-50 ISSN 1434-6044 R&D Projects: GA MŠk LA08015 Institutional research plan: CEZ:AV0Z10100502 Keywords : parton: shower s * bottom: fragmentation function * jet: hadronization * CERN * LEP * DELPHI * quantum chromodynamics * PYTHIA * ALEPH * OPAL * SLD Subject RIV: BF - Elementary Particles and High Energy Physics Impact factor: 3.631, year: 2011
Modelling hadronic interactions in HEP MC generators
Skands, Peter
2015-01-01
HEP event generators aim to describe high-energy collisions in full exclusive detail. They combine perturbative matrix elements and parton showers with dynamical models of less well-understood phenomena such as hadronization, diffraction, and the so-called underlying event. We briefly summarise some of the main concepts relevant to the modelling of soft/inclusive hadron interactions in MC generators, in particular PYTHIA, with emphasis on questions recently highlighted by LHC data.
Huston, J
2001-01-01
This talk is intended to serve as a pedagogical guide on the determination of, the proper use of, and the uncertainties of parton distribution functions and their impact on physics cross sections at the Tevatron and LHC. A longer writeup of this talk is available at http://www.pa.msu.edu./~huston/lhc/lhc_pdfnote.ps. (12 refs).
CAMS newly detected meteor showers and the sporadic background
Jenniskens, P.; Nénon, Q.; Gural, P. S.; Albers, J.; Haberman, B.; Johnson, B.; Morales, R.; Grigsby, B. J.; Samuels, D.; Johannink, C.
2016-03-01
The Cameras for Allsky Meteor Surveillance (CAMS) video-based meteoroid orbit survey adds 60 newly identified showers to the IAU Working List of Meteor Showers (numbers 427, 445-446, 506-507, and part of 643-750). 28 of these are also detected in the independent SonotaCo survey. In total, 230 meteor showers and shower components are identified in CAMS data, 177 of which are detected in at least two independent surveys. From the power-law size frequency distribution of detected showers, we extrapolate that 36% of all CAMS-observed meteors originated from ∼700 showers above the N = 1 per 110,000 shower limit. 71% of mass falling to Earth from streams arrives on Jupiter-family type orbits. The transient Geminids account for another 15%. All meteoroids not assigned to streams form a sporadic background with highest detected numbers from the apex source, but with 98% of mass falling in from the antihelion source. Even at large ∼7-mm sizes, a Poynting-Robertson drag evolved population is detected, which implies that the Grün et al. collisional lifetimes at these sizes are underestimated by about a factor of 10. While these large grains survive collisions, many fade on a 104-y timescale, possibly because they disintegrate into smaller particles by processes other than collisions, leaving a more resilient population to evolve.
COMET SHOWERS ARE NOT INDUCED BY INTERSTELLAR CLOUDS
Energy Technology Data Exchange (ETDEWEB)
Morris, D.E.
1985-11-01
Encounters with interstellar clouds (IC) have been proposed by Rampino and Stothers as a cause of quasi-periodic intense comet showers leading to earth impacts, in order to explain the periodicity in marine mass extinctions found by Raup and Sepkoski. The model was described further, criticized and defended. The debate has centered on the question of whether the scale height of the clouds is small enough (in comparison to the amplitude of the oscillation of the solar system about the plane of the Galaxy) to produce a modulation in the rate of encounters. We wish to point out another serious, we believe fatal, defect in this model - the tidal fields of ICs are not strong enough to produce intense comet showers leading to earth impacts by bringing comets of the postulated inner Oort cloud into earth crossing orbits, except possibly during very rare encounters with very dense clouds. We will show that encounters with abundant clouds of low density cannot produce comet showers; cloud density N > 10{sup 3} atoms cm{sup -3} is needed to produce an intense comet shower leading to earth impacts. Furthermore, the tidal field of a dense cloud during a distant encounter is too weak to produce such showers. As a consequence, comet showers induced by ICs will be far less frequent than showers caused by passing stars. This conclusion is independent of assumptions about the radial distribution of comets in the inner Oort cloud.
Shower reconstruction in TUNKA-HiSCORE
Energy Technology Data Exchange (ETDEWEB)
Porelli, Andrea; Wischnewski, Ralf [DESY-Zeuthen, Platanenallee 6, 15738 Zeuthen (Germany)
2015-07-01
The Tunka-HiSCORE detector is a non-imaging wide-angle EAS cherenkov array designed as an alternative technology for gamma-ray physics above 10 TeV and to study spectrum and composition of cosmic rays above 100 TeV. An engineering array with nine stations (HiS-9) has been deployed in October 2013 on the site of the Tunka experiment in Russia. In November 2014, 20 more HiSCORE stations have been installed, covering a total array area of 0.24 square-km. We describe the detector setup, the role of precision time measurement, and give results from the innovative WhiteRabbit time synchronization technology. Results of air shower reconstruction are presented and compared with MC simulations, for both the HiS-9 and the HiS-29 detector arrays.
pp interactions in extended air showers
Directory of Open Access Journals (Sweden)
Kendi Kohara A.
2015-01-01
Full Text Available Applying the recently constructed analytic representation for the pp scattering amplitudes, we present a study of p-air cross sections, with comparison to the data from Extensive Air Shower (EAS measurements. The amplitudes describe with precision all available accelerator data at ISR, SPS and LHC energies, and its theoretical basis, together with the very smooth energy dependence of parameters controlled by unitarity and dispersion relations, permit reliable extrapolation to higher energies and to asymptotic ranges. The comparison with cosmic ray data is very satisfactory in the whole pp energy interval from 1 to 100 TeV. High energy asymptotic behaviour of cross sections is investigated in view of the geometric scaling property of the amplitudes. The amplitudes predict that the proton does not behave as a black disk even at asymptotically high enegies, and we discuss possible non-trivial consequences of this fact for pA collision cross sections at higher energies.
Baryon stopping and strangeness baryon production in a parton cascade model
International Nuclear Information System (INIS)
Nara, Yasushi
1999-01-01
A parton cascade model which is based on pQCD incorporating hard partonic scattering and dynamical hadronization scheme describes the space-time evolution of parton/hadron system produced by ultra-relativistic nuclear collisions. Hadron yield, baryon stopping and transverse momentum distribution are calculated and compared with experimental data at SPS energies. Using new version of parton cascade code VNI in which baryonic cluster formation is implemented, we calculate the net baryon number distributions and Λ yield. It is found that baryon stopping behavior at SPS energies is well accounted for within the parton cascade picture. As a consequence of the production of the baryon (u and d quark) rich parton matter, parton coalescence naturally explains the enhanced yield of Λ particle which has been observed in experiment. (author)
Modelling of radio emission from cosmic ray air showers
Ludwig, Marianne
2011-06-01
Cosmic rays entering the Earth's atmosphere induce extensive air showers consisting of up to billions of secondary particles. Among them, a multitude of electrons and positrons are generated. These get deflected in the Earth's magnetic field, creating time-varying transverse currents. Thereby, the air shower emits coherent radiation in the MHz frequency range measured by radio antenna arrays on the ground such as LOPES at the KIT. This detection method provides a possibility to study cosmic rays with energies above 1017 eV. At this time, the radio technique undergoes the change from prototype experiments to large scale application. Thus, a detailed understanding of the radio emission process is needed more than ever. Before starting this work, different models made conflicting predictions on the pulse shape and the amplitude of the radio signal. It turned out that a radiation component caused by the variation of the number of charged particles within the air shower was missed in several models. The Monte Carlo code REAS2 superposing the radiation of the individual air shower electrons and positrons was one of those. At this time, it was not known how to take the missing component into account. For REAS3, we developed and implemented the endpoint formalism, a universal approach, to calculate the radiation from each single particle. For the first time, we achieve a good agreement between REAS3 and MGMR, an independent and completely different simulation approach. In contrast to REAS3, MGMR is based on a macroscopic approach and on parametrisations of the air shower. We studied the differences in the underlying air shower models to explain the remaining deviations. For comparisons with LOPES data, we developed a new method which allows "top-down" simulations of air showers. From this, we developed an air shower selection criterion based on the number of muons measured with KASCADE to take shower-to-shower fluctuations for a single event analysis into account. With
International Nuclear Information System (INIS)
Geer, S.; Gsponer, A.
1983-01-01
Absorbed radiation doses produced by 500, 1,000 and 10,000 MeV electron initiated electromagnetic showers in air have been calculated using a Monte Carlo program. The radial distributions of the absorbed dose near to the shower axis are found to be significantly narrower than predicted by simple analytical shower theory. For a 500 MeV, 10 kA, 100 ns electron beam pulse, the region in which the total dose is in excess of 1 krad and the dose rate in excess of 10 10 rad/s is a cigar-shaped envelope of radius 1 m and length 200 m. (orig.) [de
What the radio signal tells about the cosmic-ray air shower
Directory of Open Access Journals (Sweden)
Werner Klaus
2013-06-01
Full Text Available The physics of radio emission from cosmic-ray induced air showers is shortly summarized. It will be shown that the radio signal at different distances from the shower axis provides complementary information on the longitudinal shower evolution, in particular the early part, and on the distribution of the electrons in the shower core. This complements the information obtained from surface, fluorescence, and muon detectors and is very useful in getting a comprehensive picture of an air shower.
A Gas Calorimeter for High-Energy Experiment and Study of High-Energy Cascade Shower
Energy Technology Data Exchange (ETDEWEB)
Miyata, Hitoshi [Univ. of Tsukuba (Japan)
1984-09-01
High energy behavior of the electromagnetic cascade shower has been studied. high energy showers were created by electron and hadron beams with energies between 25 GeV and 150 GeV at Fermi National Accelerator Laboratory. The showers were observed by a shower detector consisting of multi-layer of lead plates and proportional chambers. The experimental results were analyzed with special emphasis on the fluctuation problem of the electromagnetic cascade shower.
Sirunyan, Albert M; Adam, Wolfgang; Aşılar, Ece; Bergauer, Thomas; Brandstetter, Johannes; Brondolin, Erica; Dragicevic, Marko; Erö, Janos; Flechl, Martin; Friedl, Markus; Fruehwirth, Rudolf; Ghete, Vasile Mihai; Hartl, Christian; Hörmann, Natascha; Hrubec, Josef; Jeitler, Manfred; König, Axel; Krätschmer, Ilse; Liko, Dietrich; Matsushita, Takashi; Mikulec, Ivan; Rabady, Dinyar; Rad, Navid; Rahbaran, Babak; Rohringer, Herbert; Schieck, Jochen; Strauss, Josef; Waltenberger, Wolfgang; Wulz, Claudia-Elisabeth; Dvornikov, Oleg; Makarenko, Vladimir; Mossolov, Vladimir; Suarez Gonzalez, Juan; Zykunov, Vladimir; Shumeiko, Nikolai; Alderweireldt, Sara; De Wolf, Eddi A; Janssen, Xavier; Lauwers, Jasper; Van De Klundert, Merijn; Van Haevermaet, Hans; Van Mechelen, Pierre; Van Remortel, Nick; Van Spilbeeck, Alex; Abu Zeid, Shimaa; Blekman, Freya; D'Hondt, Jorgen; Daci, Nadir; De Bruyn, Isabelle; Deroover, Kevin; Lowette, Steven; Moortgat, Seth; Moreels, Lieselotte; Olbrechts, Annik; Python, Quentin; Skovpen, Kirill; Tavernier, Stefaan; Van Doninck, Walter; Van Mulders, Petra; Van Parijs, Isis; Brun, Hugues; Clerbaux, Barbara; De Lentdecker, Gilles; Delannoy, Hugo; Fasanella, Giuseppe; Favart, Laurent; Goldouzian, Reza; Grebenyuk, Anastasia; Karapostoli, Georgia; Lenzi, Thomas; Léonard, Alexandre; Luetic, Jelena; Maerschalk, Thierry; Marinov, Andrey; Randle-conde, Aidan; Seva, Tomislav; Vander Velde, Catherine; Vanlaer, Pascal; Vannerom, David; Yonamine, Ryo; Zenoni, Florian; Zhang, Fengwangdong; Cornelis, Tom; Dobur, Didar; Fagot, Alexis; Gul, Muhammad; Khvastunov, Illia; Poyraz, Deniz; Salva Diblen, Sinem; Schöfbeck, Robert; Tytgat, Michael; Van Driessche, Ward; Yazgan, Efe; Zaganidis, Nicolas; Bakhshiansohi, Hamed; Bondu, Olivier; Brochet, Sébastien; Bruno, Giacomo; Caudron, Adrien; De Visscher, Simon; Delaere, Christophe; Delcourt, Martin; Francois, Brieuc; Giammanco, Andrea; Jafari, Abideh; Komm, Matthias; Krintiras, Georgios; Lemaitre, Vincent; Magitteri, Alessio; Mertens, Alexandre; Musich, Marco; Piotrzkowski, Krzysztof; Quertenmont, Loic; Selvaggi, Michele; Vidal Marono, Miguel; Wertz, Sébastien; Beliy, Nikita; Aldá Júnior, Walter Luiz; Alves, Fábio Lúcio; Alves, Gilvan; Brito, Lucas; Hensel, Carsten; Moraes, Arthur; Pol, Maria Elena; Rebello Teles, Patricia; Belchior Batista Das Chagas, Ewerton; Carvalho, Wagner; Chinellato, Jose; Custódio, Analu; Melo Da Costa, Eliza; Da Silveira, Gustavo Gil; De Jesus Damiao, Dilson; De Oliveira Martins, Carley; Fonseca De Souza, Sandro; Huertas Guativa, Lina Milena; Malbouisson, Helena; Matos Figueiredo, Diego; Mora Herrera, Clemencia; Mundim, Luiz; Nogima, Helio; Prado Da Silva, Wanda Lucia; Santoro, Alberto; Sznajder, Andre; Tonelli Manganote, Edmilson José; Torres Da Silva De Araujo, Felipe; Vilela Pereira, Antonio; Ahuja, Sudha; Bernardes, Cesar Augusto; Dogra, Sunil; Tomei, Thiago; De Moraes Gregores, Eduardo; Mercadante, Pedro G; Moon, Chang-Seong; Novaes, Sergio F; Padula, Sandra; Romero Abad, David; Ruiz Vargas, José Cupertino; Aleksandrov, Aleksandar; Hadjiiska, Roumyana; Iaydjiev, Plamen; Rodozov, Mircho; Stoykova, Stefka; Sultanov, Georgi; Vutova, Mariana; Dimitrov, Anton; Glushkov, Ivan; Litov, Leander; Pavlov, Borislav; Petkov, Peicho; Fang, Wenxing; Ahmad, Muhammad; Bian, Jian-Guo; Chen, Guo-Ming; Chen, He-Sheng; Chen, Mingshui; Chen, Ye; Cheng, Tongguang; Jiang, Chun-Hua; Leggat, Duncan; Liu, Zhenan; Romeo, Francesco; Ruan, Manqi; Shaheen, Sarmad Masood; Spiezia, Aniello; Tao, Junquan; Wang, Chunjie; Wang, Zheng; Zhang, Huaqiao; Zhao, Jingzhou; Ban, Yong; Chen, Geng; Li, Qiang; Liu, Shuai; Mao, Yajun; Qian, Si-Jin; Wang, Dayong; Xu, Zijun; Avila, Carlos; Cabrera, Andrés; Chaparro Sierra, Luisa Fernanda; Florez, Carlos; Gomez, Juan Pablo; González Hernández, Carlos Felipe; Ruiz Alvarez, José David; Sanabria, Juan Carlos; Godinovic, Nikola; Lelas, Damir; Puljak, Ivica; Ribeiro Cipriano, Pedro M; Sculac, Toni; Antunovic, Zeljko; Kovac, Marko; Brigljevic, Vuko; Ferencek, Dinko; Kadija, Kreso; Mesic, Benjamin; Susa, Tatjana; Ather, Mohsan Waseem; Attikis, Alexandros; Mavromanolakis, Georgios; Mousa, Jehad; Nicolaou, Charalambos; Ptochos, Fotios; Razis, Panos A; Rykaczewski, Hans; Finger, Miroslav; Finger Jr, Michael; Carrera Jarrin, Edgar; Ellithi Kamel, Ali; Mahmoud, Mohammed; Radi, Amr; Kadastik, Mario; Perrini, Lucia; Raidal, Martti; Tiko, Andres; Veelken, Christian; Eerola, Paula; Pekkanen, Juska; Voutilainen, Mikko; Härkönen, Jaakko; Jarvinen, Terhi; Karimäki, Veikko; Kinnunen, Ritva; Lampén, Tapio; Lassila-Perini, Kati; Lehti, Sami; Lindén, Tomas; Luukka, Panja-Riina; Tuominiemi, Jorma; Tuovinen, Esa; Wendland, Lauri; Talvitie, Joonas; Tuuva, Tuure; Besancon, Marc; Couderc, Fabrice; Dejardin, Marc; Denegri, Daniel; Fabbro, Bernard; Faure, Jean-Louis; Favaro, Carlotta; Ferri, Federico; Ganjour, Serguei; Ghosh, Saranya; Givernaud, Alain; Gras, Philippe; Hamel de Monchenault, Gautier; Jarry, Patrick; Kucher, Inna; Locci, Elizabeth; Machet, Martina; Malcles, Julie; Rander, John; Rosowsky, André; Titov, Maksym; Abdulsalam, Abdulla; Antropov, Iurii; Baffioni, Stephanie; Beaudette, Florian; Busson, Philippe; Cadamuro, Luca; Chapon, Emilien; Charlot, Claude; Davignon, Olivier; Granier de Cassagnac, Raphael; Jo, Mihee; Lisniak, Stanislav; Miné, Philippe; Nguyen, Matthew; Ochando, Christophe; Ortona, Giacomo; Paganini, Pascal; Pigard, Philipp; Regnard, Simon; Salerno, Roberto; Sirois, Yves; Stahl Leiton, Andre Govinda; Strebler, Thomas; Yilmaz, Yetkin; Zabi, Alexandre; Zghiche, Amina; Agram, Jean-Laurent; Andrea, Jeremy; Bloch, Daniel; Brom, Jean-Marie; Buttignol, Michael; Chabert, Eric Christian; Chanon, Nicolas; Collard, Caroline; Conte, Eric; Coubez, Xavier; Fontaine, Jean-Charles; Gelé, Denis; Goerlach, Ulrich; Le Bihan, Anne-Catherine; Van Hove, Pierre; Gadrat, Sébastien; Beauceron, Stephanie; Bernet, Colin; Boudoul, Gaelle; Carrillo Montoya, Camilo Andres; Chierici, Roberto; Contardo, Didier; Courbon, Benoit; Depasse, Pierre; El Mamouni, Houmani; Fay, Jean; Finco, Linda; Gascon, Susan; Gouzevitch, Maxime; Grenier, Gérald; Ille, Bernard; Lagarde, Francois; Laktineh, Imad Baptiste; Lethuillier, Morgan; Mirabito, Laurent; Pequegnot, Anne-Laure; Perries, Stephane; Popov, Andrey; Sordini, Viola; Vander Donckt, Muriel; Verdier, Patrice; Viret, Sébastien; Khvedelidze, Arsen; Lomidze, David; Autermann, Christian; Beranek, Sarah; Feld, Lutz; Kiesel, Maximilian Knut; Klein, Katja; Lipinski, Martin; Preuten, Marius; Schomakers, Christian; Schulz, Johannes; Verlage, Tobias; Albert, Andreas; Brodski, Michael; Dietz-Laursonn, Erik; Duchardt, Deborah; Endres, Matthias; Erdmann, Martin; Erdweg, Sören; Esch, Thomas; Fischer, Robert; Güth, Andreas; Hamer, Matthias; Hebbeker, Thomas; Heidemann, Carsten; Hoepfner, Kerstin; Knutzen, Simon; Merschmeyer, Markus; Meyer, Arnd; Millet, Philipp; Mukherjee, Swagata; Olschewski, Mark; Padeken, Klaas; Pook, Tobias; Radziej, Markus; Reithler, Hans; Rieger, Marcel; Scheuch, Florian; Sonnenschein, Lars; Teyssier, Daniel; Thüer, Sebastian; Cherepanov, Vladimir; Flügge, Günter; Kargoll, Bastian; Kress, Thomas; Künsken, Andreas; Lingemann, Joschka; Müller, Thomas; Nehrkorn, Alexander; Nowack, Andreas; Pistone, Claudia; Pooth, Oliver; Stahl, Achim; Aldaya Martin, Maria; Arndt, Till; Asawatangtrakuldee, Chayanit; Beernaert, Kelly; Behnke, Olaf; Behrens, Ulf; Bin Anuar, Afiq Aizuddin; Borras, Kerstin; Campbell, Alan; Connor, Patrick; Contreras-Campana, Christian; Costanza, Francesco; Diez Pardos, Carmen; Dolinska, Ganna; Eckerlin, Guenter; Eckstein, Doris; Eichhorn, Thomas; Eren, Engin; Gallo, Elisabetta; Garay Garcia, Jasone; Geiser, Achim; Gizhko, Andrii; Grados Luyando, Juan Manuel; Grohsjean, Alexander; Gunnellini, Paolo; Harb, Ali; Hauk, Johannes; Hempel, Maria; Jung, Hannes; Kalogeropoulos, Alexis; Karacheban, Olena; Kasemann, Matthias; Keaveney, James; Kleinwort, Claus; Korol, Ievgen; Krücker, Dirk; Lange, Wolfgang; Lelek, Aleksandra; Lenz, Teresa; Leonard, Jessica; Lipka, Katerina; Lobanov, Artur; Lohmann, Wolfgang; Mankel, Rainer; Melzer-Pellmann, Isabell-Alissandra; Meyer, Andreas Bernhard; Mittag, Gregor; Mnich, Joachim; Mussgiller, Andreas; Pitzl, Daniel; Placakyte, Ringaile; Raspereza, Alexei; Roland, Benoit; Sahin, Mehmet Özgür; Saxena, Pooja; Schoerner-Sadenius, Thomas; Spannagel, Simon; Stefaniuk, Nazar; Van Onsem, Gerrit Patrick; Walsh, Roberval; Wissing, Christoph; Zenaiev, Oleksandr; Blobel, Volker; Centis Vignali, Matteo; Draeger, Arne-Rasmus; Dreyer, Torben; Garutti, Erika; Gonzalez, Daniel; Haller, Johannes; Hoffmann, Malte; Junkes, Alexandra; Klanner, Robert; Kogler, Roman; Kovalchuk, Nataliia; Kurz, Simon; Lapsien, Tobias; Marchesini, Ivan; Marconi, Daniele; Meyer, Mareike; Niedziela, Marek; Nowatschin, Dominik; Pantaleo, Felice; Peiffer, Thomas; Perieanu, Adrian; Scharf, Christian; Schleper, Peter; Schmidt, Alexander; Schumann, Svenja; Schwandt, Joern; Sonneveld, Jory; Stadie, Hartmut; Steinbrück, Georg; Stober, Fred-Markus Helmut; Stöver, Marc; Tholen, Heiner; Troendle, Daniel; Usai, Emanuele; Vanelderen, Lukas; Vanhoefer, Annika; Vormwald, Benedikt; Akbiyik, Melike; Barth, Christian; Baur, Sebastian; Baus, Colin; Berger, Joram; Butz, Erik; Caspart, René; Chwalek, Thorsten; Colombo, Fabio; De Boer, Wim; Dierlamm, Alexander; Fink, Simon; Freund, Benedikt; Friese, Raphael; Giffels, Manuel; Gilbert, Andrew; Goldenzweig, Pablo; Haitz, Dominik; Hartmann, Frank; Heindl, Stefan Michael; Husemann, Ulrich; Kassel, Florian; Katkov, Igor; Kudella, Simon; Mildner, Hannes; Mozer, Matthias Ulrich; Müller, Thomas; Plagge, Michael; Quast, Gunter; Rabbertz, Klaus; Röcker, Steffen; Roscher, Frank; Schröder, Matthias; Shvetsov, Ivan; Sieber, Georg; Simonis, Hans-Jürgen; Ulrich, Ralf; Wayand, Stefan; Weber, Marc; Weiler, Thomas; Williamson, Shawn; Wöhrmann, Clemens; Wolf, Roger; Anagnostou, Georgios; Daskalakis, Georgios; Geralis, Theodoros; Giakoumopoulou, Viktoria Athina; Kyriakis, Aristotelis; Loukas, Demetrios; Topsis-Giotis, Iasonas; Kesisoglou, Stilianos; Panagiotou, Apostolos; Saoulidou, Niki; Tziaferi, Eirini; Kousouris, Konstantinos; Evangelou, Ioannis; Flouris, Giannis; Foudas, Costas; Kokkas, Panagiotis; Loukas, Nikitas; Manthos, Nikolaos; Papadopoulos, Ioannis; Paradas, Evangelos; Filipovic, Nicolas; Pasztor, Gabriella; Bencze, Gyorgy; Hajdu, Csaba; Horvath, Dezso; Sikler, Ferenc; Veszpremi, Viktor; Vesztergombi, Gyorgy; Zsigmond, Anna Julia; Beni, Noemi; Czellar, Sandor; Karancsi, János; Makovec, Alajos; Molnar, Jozsef; Szillasi, Zoltan; Bartók, Márton; Raics, Peter; Trocsanyi, Zoltan Laszlo; Ujvari, Balazs; Komaragiri, Jyothsna Rani; Bahinipati, Seema; Bhowmik, Sandeep; Choudhury, Somnath; Mal, Prolay; Mandal, Koushik; Nayak, Aruna; Sahoo, Deepak Kumar; Sahoo, Niladribihari; Swain, Sanjay Kumar; Bansal, Sunil; Beri, Suman Bala; Bhatnagar, Vipin; Chawla, Ridhi; Bhawandeep, Bhawandeep; Kalsi, Amandeep Kaur; Kaur, Anterpreet; Kaur, Manjit; Kumar, Ramandeep; Kumari, Priyanka; Mehta, Ankita; Mittal, Monika; Singh, Jasbir; Walia, Genius; Kumar, Ashok; Bhardwaj, Ashutosh; Choudhary, Brajesh C; Garg, Rocky Bala; Keshri, Sumit; Kumar, Ajay; Malhotra, Shivali; Naimuddin, Md; Ranjan, Kirti; Sharma, Ramkrishna; Sharma, Varun; Bhattacharya, Rajarshi; Bhattacharya, Satyaki; Chatterjee, Kalyanmoy; Dey, Sourav; Dutt, Suneel; Dutta, Suchandra; Ghosh, Shamik; Majumdar, Nayana; Modak, Atanu; Mondal, Kuntal; Mukhopadhyay, Supratik; Nandan, Saswati; Purohit, Arnab; Roy, Ashim; Roy, Debarati; Roy Chowdhury, Suvankar; Sarkar, Subir; Sharan, Manoj; Thakur, Shalini; Behera, Prafulla Kumar; Chudasama, Ruchi; Dutta, Dipanwita; Jha, Vishwajeet; Kumar, Vineet; Mohanty, Ajit Kumar; Netrakanti, Pawan Kumar; Pant, Lalit Mohan; Shukla, Prashant; Topkar, Anita; Aziz, Tariq; Dugad, Shashikant; Kole, Gouranga; Mahakud, Bibhuprasad; Mitra, Soureek; Mohanty, Gagan Bihari; Parida, Bibhuti; Sur, Nairit; Sutar, Bajrang; Banerjee, Sudeshna; Dewanjee, Ram Krishna; Ganguly, Sanmay; Guchait, Monoranjan; Jain, Sandhya; Kumar, Sanjeev; Maity, Manas; Majumder, Gobinda; Mazumdar, Kajari; Sarkar, Tanmay; Wickramage, Nadeesha; Chauhan, Shubhanshu; Dube, Sourabh; Hegde, Vinay; Kapoor, Anshul; Kothekar, Kunal; Pandey, Shubham; Rane, Aditee; Sharma, Seema; Chenarani, Shirin; Eskandari Tadavani, Esmaeel; Etesami, Seyed Mohsen; Khakzad, Mohsen; Mohammadi Najafabadi, Mojtaba; Naseri, Mohsen; Paktinat Mehdiabadi, Saeid; Rezaei Hosseinabadi, Ferdos; Safarzadeh, Batool; Zeinali, Maryam; Felcini, Marta; Grunewald, Martin; Abbrescia, Marcello; Calabria, Cesare; Caputo, Claudio; Colaleo, Anna; Creanza, Donato; Cristella, Leonardo; De Filippis, Nicola; De Palma, Mauro; Fiore, Luigi; Iaselli, Giuseppe; Maggi, Giorgio; Maggi, Marcello; Miniello, Giorgia; My, Salvatore; Nuzzo, Salvatore; Pompili, Alexis; Pugliese, Gabriella; Radogna, Raffaella; Ranieri, Antonio; Selvaggi, Giovanna; Sharma, Archana; Silvestris, Lucia; Venditti, Rosamaria; Verwilligen, Piet; Abbiendi, Giovanni; Battilana, Carlo; Bonacorsi, Daniele; Braibant-Giacomelli, Sylvie; Brigliadori, Luca; Campanini, Renato; Capiluppi, Paolo; Castro, Andrea; Cavallo, Francesca Romana; Chhibra, Simranjit Singh; Codispoti, Giuseppe; Cuffiani, Marco; Dallavalle, Gaetano-Marco; Fabbri, Fabrizio; Fanfani, Alessandra; Fasanella, Daniele; Giacomelli, Paolo; Grandi, Claudio; Guiducci, Luigi; Marcellini, Stefano; Masetti, Gianni; Montanari, Alessandro; Navarria, Francesco; Perrotta, Andrea; Rossi, Antonio; Rovelli, Tiziano; Siroli, Gian Piero; Tosi, Nicolò; Albergo, Sebastiano; Costa, Salvatore; Di Mattia, Alessandro; Giordano, Ferdinando; Potenza, Renato; Tricomi, Alessia; Tuve, Cristina; Barbagli, Giuseppe; Ciulli, Vitaliano; Civinini, Carlo; D'Alessandro, Raffaello; Focardi, Ettore; Lenzi, Piergiulio; Meschini, Marco; Paoletti, Simone; Russo, Lorenzo; Sguazzoni, Giacomo; Strom, Derek; Viliani, Lorenzo; Benussi, Luigi; Bianco, Stefano; Fabbri, Franco; Piccolo, Davide; Primavera, Federica; Calvelli, Valerio; Ferro, Fabrizio; Monge, Maria Roberta; Robutti, Enrico; Tosi, Silvano; Brianza, Luca; Brivio, Francesco; Ciriolo, Vincenzo; Dinardo, Mauro Emanuele; Fiorendi, Sara; Gennai, Simone; Ghezzi, Alessio; Govoni, Pietro; Malberti, Martina; Malvezzi, Sandra; Manzoni, Riccardo Andrea; Menasce, Dario; Moroni, Luigi; Paganoni, Marco; Pedrini, Daniele; Pigazzini, Simone; Ragazzi, Stefano; Tabarelli de Fatis, Tommaso; Buontempo, Salvatore; Cavallo, Nicola; De Nardo, Guglielmo; Di Guida, Salvatore; Esposito, Marco; Fabozzi, Francesco; Fienga, Francesco; Iorio, Alberto Orso Maria; Lanza, Giuseppe; Lista, Luca; Meola, Sabino; Paolucci, Pierluigi; Sciacca, Crisostomo; Thyssen, Filip; Azzi, Patrizia; Bacchetta, Nicola; Benato, Lisa; Bisello, Dario; Boletti, Alessio; Carlin, Roberto; Carvalho Antunes De Oliveira, Alexandra; Checchia, Paolo; Dall'Osso, Martino; De Castro Manzano, Pablo; Dorigo, Tommaso; Dosselli, Umberto; Gasparini, Ugo; Gonella, Franco; Lacaprara, Stefano; Margoni, Martino; Meneguzzo, Anna Teresa; Pazzini, Jacopo; Pozzobon, Nicola; Ronchese, Paolo; Rossin, Roberto; Simonetto, Franco; Torassa, Ezio; Ventura, Sandro; Zanetti, Marco; Zotto, Pierluigi; Braghieri, Alessandro; Fallavollita, Francesco; Magnani, Alice; Montagna, Paolo; Ratti, Sergio P; Re, Valerio; Ressegotti, Martina; Riccardi, Cristina; Salvini, Paola; Vai, Ilaria; Vitulo, Paolo; Alunni Solestizi, Luisa; Bilei, Gian Mario; Ciangottini, Diego; Fanò, Livio; Lariccia, Paolo; Leonardi, Roberto; Mantovani, Giancarlo; Mariani, Valentina; Menichelli, Mauro; Saha, Anirban; Santocchia, Attilio; Androsov, Konstantin; Azzurri, Paolo; Bagliesi, Giuseppe; Bernardini, Jacopo; Boccali, Tommaso; Castaldi, Rino; Ciocci, Maria Agnese; Dell'Orso, Roberto; Fedi, Giacomo; Giassi, Alessandro; Grippo, Maria Teresa; Ligabue, Franco; Lomtadze, Teimuraz; Martini, Luca; Messineo, Alberto; Palla, Fabrizio; Rizzi, Andrea; Savoy-Navarro, Aurore; Spagnolo, Paolo; Tenchini, Roberto; Tonelli, Guido; Venturi, Andrea; Verdini, Piero Giorgio; Barone, Luciano; Cavallari, Francesca; Cipriani, Marco; Del Re, Daniele; Diemoz, Marcella; Gelli, Simone; Longo, Egidio; Margaroli, Fabrizio; Marzocchi, Badder; Meridiani, Paolo; Organtini, Giovanni; Paramatti, Riccardo; Preiato, Federico; Rahatlou, Shahram; Rovelli, Chiara; Santanastasio, Francesco; Amapane, Nicola; Arcidiacono, Roberta; Argiro, Stefano; Arneodo, Michele; Bartosik, Nazar; Bellan, Riccardo; Biino, Cristina; Cartiglia, Nicolo; Cenna, Francesca; Costa, Marco; Covarelli, Roberto; Degano, Alessandro; Demaria, Natale; Kiani, Bilal; Mariotti, Chiara; Maselli, Silvia; Migliore, Ernesto; Monaco, Vincenzo; Monteil, Ennio; Monteno, Marco; Obertino, Maria Margherita; Pacher, Luca; Pastrone, Nadia; Pelliccioni, Mario; Pinna Angioni, Gian Luca; Ravera, Fabio; Romero, Alessandra; Ruspa, Marta; Sacchi, Roberto; Shchelina, Ksenia; Sola, Valentina; Solano, Ada; Staiano, Amedeo; Traczyk, Piotr; Belforte, Stefano; Casarsa, Massimo; Cossutti, Fabio; Della Ricca, Giuseppe; Zanetti, Anna; Kim, Dong Hee; Kim, Gui Nyun; Kim, Min Suk; Lee, Jeongeun; Lee, Sangeun; Lee, Seh Wook; Oh, Young Do; Sekmen, Sezen; Son, Dong-Chul; Yang, Yu Chul; Lee, Ari; Kim, Hyunchul; Brochero Cifuentes, Javier Andres; Kim, Tae Jeong; Cho, Sungwoong; Choi, Suyong; Go, Yeonju; Gyun, Dooyeon; Ha, Seungkyu; Hong, Byung-Sik; Jo, Youngkwon; Kim, Yongsun; Lee, Kisoo; Lee, Kyong Sei; Lee, Songkyo; Lim, Jaehoon; Park, Sung Keun; Roh, Youn; Almond, John; Kim, Junho; Lee, Haneol; Oh, Sung Bin; Radburn-Smith, Benjamin Charles; Seo, Seon-hee; Yang, Unki; Yoo, Hwi Dong; Yu, Geum Bong; Choi, Minkyoo; Kim, Hyunyong; Kim, Ji Hyun; Lee, Jason Sang Hun; Park, Inkyu; Ryu, Geonmo; Ryu, Min Sang; Choi, Young-Il; Goh, Junghwan; Hwang, Chanwook; Lee, Jongseok; Yu, Intae; Dudenas, Vytautas; Juodagalvis, Andrius; Vaitkus, Juozas; Ahmed, Ijaz; Ibrahim, Zainol Abidin; Md Ali, Mohd Adli Bin; Mohamad Idris, Faridah; Wan Abdullah, Wan Ahmad Tajuddin; Yusli, Mohd Nizam; Zolkapli, Zukhaimira; Castilla-Valdez, Heriberto; De La Cruz-Burelo, Eduard; Heredia-De La Cruz, Ivan; Lopez-Fernandez, Ricardo; Magaña Villalba, Ricardo; Mejia Guisao, Jhovanny; Sánchez Hernández, Alberto; Carrillo Moreno, Salvador; Oropeza Barrera, Cristina; Vazquez Valencia, Fabiola; Carpinteyro, Severiano; Pedraza, Isabel; Salazar Ibarguen, Humberto Antonio; Uribe Estrada, Cecilia; Morelos Pineda, Antonio; Krofcheck, David; Butler, Philip H; Ahmad, Ashfaq; Ahmad, Muhammad; Hassan, Qamar; Hoorani, Hafeez R; Khan, Wajid Ali; Saddique, Asif; Shah, Mehar Ali; Shoaib, Muhammad; Waqas, Muhammad; Bialkowska, Helena; Bluj, Michal; Boimska, Bożena; Frueboes, Tomasz; Górski, Maciej; Kazana, Malgorzata; Nawrocki, Krzysztof; Romanowska-Rybinska, Katarzyna; Szleper, Michal; Zalewski, Piotr; Bunkowski, Karol; Byszuk, Adrian; Doroba, Krzysztof; Kalinowski, Artur; Konecki, Marcin; Krolikowski, Jan; Misiura, Maciej; Olszewski, Michal; Pyskir, Andrzej; Walczak, Marek; Bargassa, Pedrame; Beirão Da Cruz E Silva, Cristóvão; Calpas, Betty; Di Francesco, Agostino; Faccioli, Pietro; Gallinaro, Michele; Hollar, Jonathan; Leonardo, Nuno; Lloret Iglesias, Lara; Nemallapudi, Mythra Varun; Seixas, Joao; Toldaiev, Oleksii; Vadruccio, Daniele; Varela, Joao; Afanasiev, Serguei; Bunin, Pavel; Gavrilenko, Mikhail; Golutvin, Igor; Gorbunov, Ilya; Kamenev, Alexey; Karjavin, Vladimir; Lanev, Alexander; Malakhov, Alexander; Matveev, Viktor; Palichik, Vladimir; Perelygin, Victor; Shmatov, Sergey; Shulha, Siarhei; Skatchkov, Nikolai; Smirnov, Vitaly; Voytishin, Nikolay; Zarubin, Anatoli; Chtchipounov, Leonid; Golovtsov, Victor; Ivanov, Yury; Kim, Victor; Kuznetsova, Ekaterina; Murzin, Victor; Oreshkin, Vadim; Sulimov, Valentin; Vorobyev, Alexey; Andreev, Yuri; Dermenev, Alexander; Gninenko, Sergei; Golubev, Nikolai; Karneyeu, Anton; Kirsanov, Mikhail; Krasnikov, Nikolai; Pashenkov, Anatoli; Tlisov, Danila; Toropin, Alexander; Epshteyn, Vladimir; Gavrilov, Vladimir; Lychkovskaya, Natalia; Popov, Vladimir; Pozdnyakov, Ivan; Safronov, Grigory; Spiridonov, Alexander; Toms, Maria; Vlasov, Evgueni; Zhokin, Alexander; Aushev, Tagir; Bylinkin, Alexander; Danilov, Mikhail; Popova, Elena; Rusinov, Vladimir; Andreev, Vladimir; Azarkin, Maksim; Dremin, Igor; Kirakosyan, Martin; Leonidov, Andrey; Terkulov, Adel; Baskakov, Alexey; Belyaev, Andrey; Boos, Edouard; Bunichev, Viacheslav; Dubinin, Mikhail; Dudko, Lev; Ershov, Alexander; Klyukhin, Vyacheslav; Korneeva, Natalia; Lokhtin, Igor; Miagkov, Igor; Obraztsov, Stepan; Perfilov, Maxim; Savrin, Viktor; Volkov, Petr; Blinov, Vladimir; Skovpen, Yuri; Shtol, Dmitry; Azhgirey, Igor; Bayshev, Igor; Bitioukov, Sergei; Elumakhov, Dmitry; Kachanov, Vassili; Kalinin, Alexey; Konstantinov, Dmitri; Krychkine, Victor; Petrov, Vladimir; Ryutin, Roman; Sobol, Andrei; Troshin, Sergey; Tyurin, Nikolay; Uzunian, Andrey; Volkov, Alexey; Adzic, Petar; Cirkovic, Predrag; Devetak, Damir; Dordevic, Milos; Milosevic, Jovan; Rekovic, Vladimir; Alcaraz Maestre, Juan; Barrio Luna, Mar; Calvo, Enrique; Cerrada, Marcos; Chamizo Llatas, Maria; Colino, Nicanor; De La Cruz, Begona; Delgado Peris, Antonio; Escalante Del Valle, Alberto; Fernandez Bedoya, Cristina; Fernández Ramos, Juan Pablo; Flix, Jose; Fouz, Maria Cruz; Garcia-Abia, Pablo; Gonzalez Lopez, Oscar; Goy Lopez, Silvia; Hernandez, Jose M; Josa, Maria Isabel; Navarro De Martino, Eduardo; Pérez-Calero Yzquierdo, Antonio María; Puerta Pelayo, Jesus; Quintario Olmeda, Adrián; Redondo, Ignacio; Romero, Luciano; Senghi Soares, Mara; de Trocóniz, Jorge F; Missiroli, Marino; Moran, Dermot; Cuevas, Javier; Erice, Carlos; Fernandez Menendez, Javier; Gonzalez Caballero, Isidro; González Fernández, Juan Rodrigo; Palencia Cortezon, Enrique; Sanchez Cruz, Sergio; Suárez Andrés, Ignacio; Vischia, Pietro; Vizan Garcia, Jesus Manuel; Cabrillo, Iban Jose; Calderon, Alicia; Curras, Esteban; Fernandez, Marcos; Garcia-Ferrero, Juan; Gomez, Gervasio; Lopez Virto, Amparo; Marco, Jesus; Martinez Rivero, Celso; Matorras, Francisco; Piedra Gomez, Jonatan; Rodrigo, Teresa; Ruiz-Jimeno, Alberto; Scodellaro, Luca; Trevisani, Nicolò; Vila, Ivan; Vilar Cortabitarte, Rocio; Abbaneo, Duccio; Auffray, Etiennette; Auzinger, Georg; Baillon, Paul; Ball, Austin; Barney, David; Bloch, Philippe; Bocci, Andrea; Botta, Cristina; Camporesi, Tiziano; Castello, Roberto; Cepeda, Maria; Cerminara, Gianluca; Chen, Yi; Cimmino, Anna; D'Enterria, David; Dabrowski, Anne; Daponte, Vincenzo; David Tinoco Mendes, Andre; De Gruttola, Michele; De Roeck, Albert; Di Marco, Emanuele; Dobson, Marc; Dorney, Brian; Du Pree, Tristan; Duggan, Daniel; Dünser, Marc; Dupont, Niels; Elliott-Peisert, Anna; Everaerts, Pieter; Fartoukh, Stephane; Franzoni, Giovanni; Fulcher, Jonathan; Funk, Wolfgang; Gigi, Dominique; Gill, Karl; Girone, Maria; Glege, Frank; Gulhan, Doga; Gundacker, Stefan; Guthoff, Moritz; Harris, Philip; Hegeman, Jeroen; Innocente, Vincenzo; Janot, Patrick; Kieseler, Jan; Kirschenmann, Henning; Knünz, Valentin; Kornmayer, Andreas; Kortelainen, Matti J; Krammer, Manfred; Lange, Clemens; Lecoq, Paul; Lourenco, Carlos; Lucchini, Marco Toliman; Malgeri, Luca; Mannelli, Marcello; Martelli, Arabella; Meijers, Frans; Merlin, Jeremie Alexandre; Mersi, Stefano; Meschi, Emilio; Milenovic, Predrag; Moortgat, Filip; Morovic, Srecko; Mulders, Martijn; Neugebauer, Hannes; Orfanelli, Styliani; Orsini, Luciano; Pape, Luc; Perez, Emmanuel; Peruzzi, Marco; Petrilli, Achille; Petrucciani, Giovanni; Pfeiffer, Andreas; Pierini, Maurizio; Racz, Attila; Reis, Thomas; Rolandi, Gigi; Rovere, Marco; Sakulin, Hannes; Sauvan, Jean-Baptiste; Schäfer, Christoph; Schwick, Christoph; Seidel, Markus; Sharma, Archana; Silva, Pedro; Sphicas, Paraskevas; Steggemann, Jan; Stoye, Markus; Takahashi, Yuta; Tosi, Mia; Treille, Daniel; Triossi, Andrea; Tsirou, Andromachi; Veckalns, Viesturs; Veres, Gabor Istvan; Verweij, Marta; Wardle, Nicholas; Wöhri, Hermine Katharina; Zagoździńska, Agnieszka; Zeuner, Wolfram Dietrich; Bertl, Willi; Deiters, Konrad; Erdmann, Wolfram; Horisberger, Roland; Ingram, Quentin; Kaestli, Hans-Christian; Kotlinski, Danek; Langenegger, Urs; Rohe, Tilman; Wiederkehr, Stephan Albert; Bachmair, Felix; Bäni, Lukas; Bianchini, Lorenzo; Casal, Bruno; Dissertori, Günther; Dittmar, Michael; Donegà, Mauro; Grab, Christoph; Heidegger, Constantin; Hits, Dmitry; Hoss, Jan; Kasieczka, Gregor; Lustermann, Werner; Mangano, Boris; Marionneau, Matthieu; Martinez Ruiz del Arbol, Pablo; Masciovecchio, Mario; Meinhard, Maren Tabea; Meister, Daniel; Micheli, Francesco; Musella, Pasquale; Nessi-Tedaldi, Francesca; Pandolfi, Francesco; Pata, Joosep; Pauss, Felicitas; Perrin, Gaël; Perrozzi, Luca; Quittnat, Milena; Rossini, Marco; Schönenberger, Myriam; Starodumov, Andrei; Tavolaro, Vittorio Raoul; Theofilatos, Konstantinos; Wallny, Rainer; Aarrestad, Thea Klaeboe; Amsler, Claude; Caminada, Lea; Canelli, Maria Florencia; De Cosa, Annapaola; Donato, Silvio; Galloni, Camilla; Hinzmann, Andreas; Hreus, Tomas; Kilminster, Benjamin; Ngadiuba, Jennifer; Pinna, Deborah; Rauco, Giorgia; Robmann, Peter; Salerno, Daniel; Seitz, Claudia; Yang, Yong; Zucchetta, Alberto; Candelise, Vieri; Doan, Thi Hien; Jain, Shilpi; Khurana, Raman; Konyushikhin, Maxim; Kuo, Chia-Ming; Lin, Willis; Pozdnyakov, Andrey; Yu, Shin-Shan; Kumar, Arun; Chang, Paoti; Chang, You-Hao; Chao, Yuan; Chen, Kai-Feng; Chen, Po-Hsun; Fiori, Francesco; Hou, George Wei-Shu; Hsiung, Yee; Liu, Yueh-Feng; Lu, Rong-Shyang; Miñano Moya, Mercedes; Paganis, Efstathios; Psallidas, Andreas; Tsai, Jui-fa; Asavapibhop, Burin; Singh, Gurpreet; Srimanobhas, Norraphat; Suwonjandee, Narumon; Adiguzel, Aytul; Boran, Fatma; Cerci, Salim; Damarseckin, Serdal; Demiroglu, Zuhal Seyma; Dozen, Candan; Dumanoglu, Isa; Girgis, Semiray; Gokbulut, Gul; Guler, Yalcin; Hos, Ilknur; Kangal, Evrim Ersin; Kara, Ozgun; Kiminsu, Ugur; Oglakci, Mehmet; Onengut, Gulsen; Ozdemir, Kadri; Sunar Cerci, Deniz; Tali, Bayram; Topakli, Huseyin; Turkcapar, Semra; Zorbakir, Ibrahim Soner; Zorbilmez, Caglar; Bilin, Bugra; Bilmis, Selcuk; Isildak, Bora; Karapinar, Guler; Yalvac, Metin; Zeyrek, Mehmet; Gülmez, Erhan; Kaya, Mithat; Kaya, Ozlem; Yetkin, Elif Asli; Yetkin, Taylan; Cakir, Altan; Cankocak, Kerem; Sen, Sercan; Grynyov, Boris; Levchuk, Leonid; Sorokin, Pavel; Aggleton, Robin; Ball, Fionn; Beck, Lana; Brooke, James John; Burns, Douglas; Clement, Emyr; Cussans, David; Flacher, Henning; Goldstein, Joel; Grimes, Mark; Heath, Greg P; Heath, Helen F; Jacob, Jeson; Kreczko, Lukasz; Lucas, Chris; Newbold, Dave M; Paramesvaran, Sudarshan; Poll, Anthony; Sakuma, Tai; Seif El Nasr-storey, Sarah; Smith, Dominic; Smith, Vincent J; Bell, Ken W; Belyaev, Alexander; Brew, Christopher; Brown, Robert M; Calligaris, Luigi; Cieri, Davide; Cockerill, David JA; Coughlan, John A; Harder, Kristian; Harper, Sam; Olaiya, Emmanuel; Petyt, David; Shepherd-Themistocleous, Claire; Thea, Alessandro; Tomalin, Ian R; Williams, Thomas; Baber, Mark; Bainbridge, Robert; Buchmuller, Oliver; Bundock, Aaron; Casasso, Stefano; Citron, Matthew; Colling, David; Corpe, Louie; Dauncey, Paul; Davies, Gavin; De Wit, Adinda; Della Negra, Michel; Di Maria, Riccardo; Dunne, Patrick; Elwood, Adam; Futyan, David; Haddad, Yacine; Hall, Geoffrey; Iles, Gregory; James, Thomas; Lane, Rebecca; Laner, Christian; Lyons, Louis; Magnan, Anne-Marie; Malik, Sarah; Mastrolorenzo, Luca; Nash, Jordan; Nikitenko, Alexander; Pela, Joao; Penning, Bjoern; Pesaresi, Mark; Raymond, David Mark; Richards, Alexander; Rose, Andrew; Scott, Edward; Seez, Christopher; Summers, Sioni; Tapper, Alexander; Uchida, Kirika; Vazquez Acosta, Monica; Virdee, Tejinder; Wright, Jack; Zenz, Seth Conrad; Cole, Joanne; Hobson, Peter R; Khan, Akram; Kyberd, Paul; Reid, Ivan; Symonds, Philip; Teodorescu, Liliana; Turner, Mark; Borzou, Ahmad; Call, Kenneth; Dittmann, Jay; Hatakeyama, Kenichi; Liu, Hongxuan; Pastika, Nathaniel; Bartek, Rachel; Dominguez, Aaron; Buccilli, Andrew; Cooper, Seth; Henderson, Conor; Rumerio, Paolo; West, Christopher; Arcaro, Daniel; Avetisyan, Aram; Bose, Tulika; Gastler, Daniel; Rankin, Dylan; Richardson, Clint; Rohlf, James; Sulak, Lawrence; Zou, David; Benelli, Gabriele; Cutts, David; Garabedian, Alex; Hakala, John; Heintz, Ulrich; Hogan, Julie Managan; Jesus, Orduna; Kwok, Ka Hei Martin; Laird, Edward; Landsberg, Greg; Mao, Zaixing; Narain, Meenakshi; Piperov, Stefan; Sagir, Sinan; Spencer, Eric; Syarif, Rizki; Breedon, Richard; Burns, Dustin; Calderon De La Barca Sanchez, Manuel; Chauhan, Sushil; Chertok, Maxwell; Conway, John; Conway, Rylan; Cox, Peter Timothy; Erbacher, Robin; Flores, Chad; Funk, Garrett; Gardner, Michael; Ko, Winston; Lander, Richard; Mclean, Christine; Mulhearn, Michael; Pellett, Dave; Pilot, Justin; Shalhout, Shalhout; Shi, Mengyao; Smith, John; Squires, Michael; Stolp, Dustin; Tos, Kyle; Tripathi, Mani; Bachtis, Michail; Bravo, Cameron; Cousins, Robert; Dasgupta, Abhigyan; Florent, Alice; Hauser, Jay; Ignatenko, Mikhail; Mccoll, Nickolas; Saltzberg, David; Schnaible, Christian; Valuev, Vyacheslav; Weber, Matthias; Bouvier, Elvire; Burt, Kira; Clare, Robert; Ellison, John Anthony; Gary, J William; Ghiasi Shirazi, Seyyed Mohammad Amin; Hanson, Gail; Heilman, Jesse; Jandir, Pawandeep; Kennedy, Elizabeth; Lacroix, Florent; Long, Owen Rosser; Olmedo Negrete, Manuel; Paneva, Mirena Ivova; Shrinivas, Amithabh; Si, Weinan; Wei, Hua; Wimpenny, Stephen; Yates, Brent; Branson, James G; Cerati, Giuseppe Benedetto; Cittolin, Sergio; Derdzinski, Mark; Gerosa, Raffaele; Holzner, André; Klein, Daniel; Krutelyov, Vyacheslav; Letts, James; Macneill, Ian; Olivito, Dominick; Padhi, Sanjay; Pieri, Marco; Sani, Matteo; Sharma, Vivek; Simon, Sean; Tadel, Matevz; Vartak, Adish; Wasserbaech, Steven; Welke, Charles; Wood, John; Würthwein, Frank; Yagil, Avraham; Zevi Della Porta, Giovanni; Amin, Nick; Bhandari, Rohan; Bradmiller-Feld, John; Campagnari, Claudio; Dishaw, Adam; Dutta, Valentina; Franco Sevilla, Manuel; George, Christopher; Golf, Frank; Gouskos, Loukas; Gran, Jason; Heller, Ryan; Incandela, Joe; Mullin, Sam Daniel; Ovcharova, Ana; Qu, Huilin; Richman, Jeffrey; Stuart, David; Suarez, Indara; Yoo, Jaehyeok; Anderson, Dustin; Bendavid, Joshua; Bornheim, Adolf; Bunn, Julian; Duarte, Javier; Lawhorn, Jay Mathew; Mott, Alexander; Newman, Harvey B; Pena, Cristian; Spiropulu, Maria; Vlimant, Jean-Roch; Xie, Si; Zhu, Ren-Yuan; Andrews, Michael Benjamin; Ferguson, Thomas; Paulini, Manfred; Russ, James; Sun, Menglei; Vogel, Helmut; Vorobiev, Igor; Weinberg, Marc; Cumalat, John Perry; Ford, William T; Jensen, Frank; Johnson, Andrew; Krohn, Michael; Leontsinis, Stefanos; Mulholland, Troy; Stenson, Kevin; Wagner, Stephen Robert; Alexander, James; Chaves, Jorge; Chu, Jennifer; Dittmer, Susan; Mcdermott, Kevin; Mirman, Nathan; Patterson, Juliet Ritchie; Rinkevicius, Aurelijus; Ryd, Anders; Skinnari, Louise; Soffi, Livia; Tan, Shao Min; Tao, Zhengcheng; Thom, Julia; Tucker, Jordan; Wittich, Peter; Zientek, Margaret; Winn, Dave; Abdullin, Salavat; Albrow, Michael; Apollinari, Giorgio; Apresyan, Artur; Banerjee, Sunanda; Bauerdick, Lothar AT; Beretvas, Andrew; Berryhill, Jeffrey; Bhat, Pushpalatha C; Bolla, Gino; Burkett, Kevin; Butler, Joel Nathan; Cheung, Harry; Chlebana, Frank; Cihangir, Selcuk; Cremonesi, Matteo; Elvira, Victor Daniel; Fisk, Ian; Freeman, Jim; Gottschalk, Erik; Gray, Lindsey; Green, Dan; Grünendahl, Stefan; Gutsche, Oliver; Hare, Daryl; Harris, Robert M; Hasegawa, Satoshi; Hirschauer, James; Hu, Zhen; Jayatilaka, Bodhitha; Jindariani, Sergo; Johnson, Marvin; Joshi, Umesh; Klima, Boaz; Kreis, Benjamin; Lammel, Stephan; Linacre, Jacob; Lincoln, Don; Lipton, Ron; Liu, Miaoyuan; Liu, Tiehui; Lopes De Sá, Rafael; Lykken, Joseph; Maeshima, Kaori; Magini, Nicolo; Marraffino, John Michael; Maruyama, Sho; Mason, David; McBride, Patricia; Merkel, Petra; Mrenna, Stephen; Nahn, Steve; O'Dell, Vivian; Pedro, Kevin; Prokofyev, Oleg; Rakness, Gregory; Ristori, Luciano; Sexton-Kennedy, Elizabeth; Soha, Aron; Spalding, William J; Spiegel, Leonard; Stoynev, Stoyan; Strait, James; Strobbe, Nadja; Taylor, Lucas; Tkaczyk, Slawek; Tran, Nhan Viet; Uplegger, Lorenzo; Vaandering, Eric Wayne; Vernieri, Caterina; Verzocchi, Marco; Vidal, Richard; Wang, Michael; Weber, Hannsjoerg Artur; Whitbeck, Andrew; Wu, Yujun; Acosta, Darin; Avery, Paul; Bortignon, Pierluigi; Bourilkov, Dimitri; Brinkerhoff, Andrew; Carnes, Andrew; Carver, Matthew; Curry, David; Das, Souvik; Field, Richard D; Furic, Ivan-Kresimir; Konigsberg, Jacobo; Korytov, Andrey; Low, Jia Fu; Ma, Peisen; Matchev, Konstantin; Mei, Hualin; Mitselmakher, Guenakh; Rank, Douglas; Shchutska, Lesya; Sperka, David; Thomas, Laurent; Wang, Jian; Wang, Sean-Jiun; Yelton, John; Linn, Stephan; Markowitz, Pete; Martinez, German; Rodriguez, Jorge Luis; Ackert, Andrew; Adams, Todd; Askew, Andrew; Bein, Samuel; Hagopian, Sharon; Hagopian, Vasken; Johnson, Kurtis F; Kolberg, Ted; Perry, Thomas; Prosper, Harrison; Santra, Arka; Yohay, Rachel; Baarmand, Marc M; Bhopatkar, Vallary; Colafranceschi, Stefano; Hohlmann, Marcus; Noonan, Daniel; Roy, Titas; Yumiceva, Francisco; Adams, Mark Raymond; Apanasevich, Leonard; Berry, Douglas; Betts, Russell Richard; Cavanaugh, Richard; Chen, Xuan; Evdokimov, Olga; Gerber, Cecilia Elena; Hangal, Dhanush Anil; Hofman, David Jonathan; Jung, Kurt; Kamin, Jason; Sandoval Gonzalez, Irving Daniel; Trauger, Hallie; Varelas, Nikos; Wang, Hui; Wu, Zhenbin; Zhang, Jingyu; Bilki, Burak; Clarida, Warren; Dilsiz, Kamuran; Durgut, Süleyman; Gandrajula, Reddy Pratap; Haytmyradov, Maksat; Khristenko, Viktor; Merlo, Jean-Pierre; Mermerkaya, Hamit; Mestvirishvili, Alexi; Moeller, Anthony; Nachtman, Jane; Ogul, Hasan; Onel, Yasar; Ozok, Ferhat; Penzo, Aldo; Snyder, Christina; Tiras, Emrah; Wetzel, James; Yi, Kai; Blumenfeld, Barry; Cocoros, Alice; Eminizer, Nicholas; Fehling, David; Feng, Lei; Gritsan, Andrei; Maksimovic, Petar; Roskes, Jeffrey; Sarica, Ulascan; Swartz, Morris; Xiao, Meng; You, Can; Al-bataineh, Ayman; Baringer, Philip; Bean, Alice; Boren, Samuel; Bowen, James; Castle, James; Forthomme, Laurent; Khalil, Sadia; Kropivnitskaya, Anna; Majumder, Devdatta; Mcbrayer, William; Murray, Michael; Sanders, Stephen; Stringer, Robert; Tapia Takaki, Daniel; Wang, Quan; Ivanov, Andrew; Kaadze, Ketino; Maravin, Yurii; Mohammadi, Abdollah; Saini, Lovedeep Kaur; Skhirtladze, Nikoloz; Toda, Sachiko; Rebassoo, Finn; Wright, Douglas; Anelli, Christopher; Baden, Drew; Baron, Owen; Belloni, Alberto; Calvert, Brian; Eno, Sarah Catherine; Ferraioli, Charles; Gomez, Jaime; Hadley, Nicholas John; Jabeen, Shabnam; Jeng, Geng-Yuan; Kellogg, Richard G; Kunkle, Joshua; Mignerey, Alice; Ricci-Tam, Francesca; Shin, Young Ho; Skuja, Andris; Tonjes, Marguerite; Tonwar, Suresh C; Abercrombie, Daniel; Allen, Brandon; Apyan, Aram; Azzolini, Virginia; Barbieri, Richard; Baty, Austin; Bi, Ran; Bierwagen, Katharina; Brandt, Stephanie; Busza, Wit; Cali, Ivan Amos; D'Alfonso, Mariarosaria; Demiragli, Zeynep; Gomez Ceballos, Guillelmo; Goncharov, Maxim; Hsu, Dylan; Iiyama, Yutaro; Innocenti, Gian Michele; Klute, Markus; Kovalskyi, Dmytro; Krajczar, Krisztian; Lai, Yue Shi; Lee, Yen-Jie; Levin, Andrew; Luckey, Paul David; Maier, Benedikt; Marini, Andrea Carlo; Mcginn, Christopher; Mironov, Camelia; Narayanan, Siddharth; Niu, Xinmei; Paus, Christoph; Roland, Christof; Roland, Gunther; Salfeld-Nebgen, Jakob; Stephans, George; Tatar, Kaya; Velicanu, Dragos; Wang, Jing; Wang, Ta-Wei; Wyslouch, Bolek; Benvenuti, Alberto; Chatterjee, Rajdeep Mohan; Evans, Andrew; Hansen, Peter; Kalafut, Sean; Kao, Shih-Chuan; Kubota, Yuichi; Lesko, Zachary; Mans, Jeremy; Nourbakhsh, Shervin; Ruckstuhl, Nicole; Rusack, Roger; Tambe, Norbert; Turkewitz, Jared; Acosta, John Gabriel; Oliveros, Sandra; Avdeeva, Ekaterina; Bloom, Kenneth; Claes, Daniel R; Fangmeier, Caleb; Gonzalez Suarez, Rebeca; Kamalieddin, Rami; Kravchenko, Ilya; Malta Rodrigues, Alan; Monroy, Jose; Siado, Joaquin Emilo; Snow, Gregory R; Stieger, Benjamin; Alyari, Maral; Dolen, James; Godshalk, Andrew; Harrington, Charles; Iashvili, Ia; Kaisen, Josh; Nguyen, Duong; Parker, Ashley; Rappoccio, Salvatore; Roozbahani, Bahareh; Alverson, George; Barberis, Emanuela; Hortiangtham, Apichart; Massironi, Andrea; Morse, David Michael; Nash, David; Orimoto, Toyoko; Teixeira De Lima, Rafael; Trocino, Daniele; Wang, Ren-Jie; Wood, Darien; Bhattacharya, Saptaparna; Charaf, Otman; Hahn, Kristan Allan; Mucia, Nicholas; Odell, Nathaniel; Pollack, Brian; Schmitt, Michael Henry; Sung, Kevin; Trovato, Marco; Velasco, Mayda; Dev, Nabarun; Hildreth, Michael; Hurtado Anampa, Kenyi; Jessop, Colin; Karmgard, Daniel John; Kellams, Nathan; Lannon, Kevin; Marinelli, Nancy; Meng, Fanbo; Mueller, Charles; Musienko, Yuri; Planer, Michael; Reinsvold, Allison; Ruchti, Randy; Rupprecht, Nathaniel; Smith, Geoffrey; Taroni, Silvia; Wayne, Mitchell; Wolf, Matthias; Woodard, Anna; Alimena, Juliette; Antonelli, Louis; Bylsma, Ben; Durkin, Lloyd Stanley; Flowers, Sean; Francis, Brian; Hart, Andrew; Hill, Christopher; Ji, Weifeng; Liu, Bingxuan; Luo, Wuming; Puigh, Darren; Winer, Brian L; Wulsin, Howard Wells; Cooperstein, Stephane; Driga, Olga; Elmer, Peter; Hardenbrook, Joshua; Hebda, Philip; Lange, David; Luo, Jingyu; Marlow, Daniel; Medvedeva, Tatiana; Mei, Kelvin; Ojalvo, Isabel; Olsen, James; Palmer, Christopher; Piroué, Pierre; Stickland, David; Svyatkovskiy, Alexey; Tully, Christopher; Malik, Sudhir; Barker, Anthony; Barnes, Virgil E; Folgueras, Santiago; Gutay, Laszlo; Jha, Manoj; Jones, Matthew; Jung, Andreas Werner; Khatiwada, Ajeeta; Miller, David Harry; Neumeister, Norbert; Schulte, Jan-Frederik; Shi, Xin; Sun, Jian; Wang, Fuqiang; Xie, Wei; Parashar, Neeti; Stupak, John; Adair, Antony; Akgun, Bora; Chen, Zhenyu; Ecklund, Karl Matthew; Geurts, Frank JM; Guilbaud, Maxime; Li, Wei; Michlin, Benjamin; Northup, Michael; Padley, Brian Paul; Roberts, Jay; Rorie, Jamal; Tu, Zhoudunming; Zabel, James; Betchart, Burton; Bodek, Arie; de Barbaro, Pawel; Demina, Regina; Duh, Yi-ting; Ferbel, Thomas; Galanti, Mario; Garcia-Bellido, Aran; Han, Jiyeon; Hindrichs, Otto; Khukhunaishvili, Aleko; Lo, Kin Ho; Tan, Ping; Verzetti, Mauro; Agapitos, Antonis; Chou, John Paul; Gershtein, Yuri; Gómez Espinosa, Tirso Alejandro; Halkiadakis, Eva; Heindl, Maximilian; Hughes, Elliot; Kaplan, Steven; Kunnawalkam Elayavalli, Raghav; Kyriacou, Savvas; Lath, Amitabh; Montalvo, Roy; Nash, Kevin; Osherson, Marc; Saka, Halil; Salur, Sevil; Schnetzer, Steve; Sheffield, David; Somalwar, Sunil; Stone, Robert; Thomas, Scott; Thomassen, Peter; Walker, Matthew; Delannoy, Andrés G; Foerster, Mark; Heideman, Joseph; Riley, Grant; Rose, Keith; Spanier, Stefan; Thapa, Krishna; Bouhali, Othmane; Celik, Ali; Dalchenko, Mykhailo; De Mattia, Marco; Delgado, Andrea; Dildick, Sven; Eusebi, Ricardo; Gilmore, Jason; Huang, Tao; Juska, Evaldas; Kamon, Teruki; Mueller, Ryan; Pakhotin, Yuriy; Patel, Rishi; Perloff, Alexx; Perniè, Luca; Rathjens, Denis; Safonov, Alexei; Tatarinov, Aysen; Ulmer, Keith; Akchurin, Nural; Damgov, Jordan; De Guio, Federico; Dragoiu, Cosmin; Dudero, Phillip Russell; Faulkner, James; Gurpinar, Emine; Kunori, Shuichi; Lamichhane, Kamal; Lee, Sung Won; Libeiro, Terence; Peltola, Timo; Undleeb, Sonaina; Volobouev, Igor; Wang, Zhixing; Greene, Senta; Gurrola, Alfredo; Janjam, Ravi; Johns, Willard; Maguire, Charles; Melo, Andrew; Ni, Hong; Sheldon, Paul; Tuo, Shengquan; Velkovska, Julia; Xu, Qiao; Arenton, Michael Wayne; Barria, Patrizia; Cox, Bradley; Hirosky, Robert; Ledovskoy, Alexander; Li, Hengne; Neu, Christopher; Sinthuprasith, Tutanon; Sun, Xin; Wang, Yanchu; Wolfe, Evan; Xia, Fan; Clarke, Christopher; Harr, Robert; Karchin, Paul Edmund; Sturdy, Jared; Zaleski, Shawn; Belknap, Donald; Buchanan, James; Caillol, Cécile; Dasu, Sridhara; Dodd, Laura; Duric, Senka; Gomber, Bhawna; Grothe, Monika; Herndon, Matthew; Hervé, Alain; Hussain, Usama; Klabbers, Pamela; Lanaro, Armando; Levine, Aaron; Long, Kenneth; Loveless, Richard; Pierro, Giuseppe Antonio; Polese, Giovanni; Ruggles, Tyler; Savin, Alexander; Smith, Nicholas; Smith, Wesley H; Taylor, Devin; Woods, Nathaniel
2017-07-11
Normalized double-differential cross sections for top quark pair ($ \\mathrm{ t \\bar{t} } $) production are measured in pp collisions at a centre-of-mass energy of 8 TeV with the CMS experiment at the LHC. The analyzed data correspond to an integrated luminosity of 19.7 fb$^{-1}$. The measurement is performed in the dilepton $\\mathrm{ e }^{\\pm}\\mu^{\\mp}$ final state. The $ \\mathrm{ t \\bar{t} } $ cross section is determined as a function of various pairs of observables characterizing the kinematics of the top quark and $ \\mathrm{ t \\bar{t} } $ system. The data are compared to calculations using perturbative quantum chromodynamics at next-to-leading and approximate next-to-next-to-leading orders. They are also compared to predictions of Monte Carlo event generators that complement fixed-order computations with parton showers, hadronization, and multiple-parton interactions. Overall agreement is observed with the predictions, which is improved when the latest global sets of proton parton distribution functions ar...
Charge symmetry breaking in parton distribution functions from lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Horsley, R.; Zanotti, J.M. [Edinburgh Univ. (United Kingdom). School of Physics and Astronomy; Nakamura, Y. [Regensburg Univ. (Germany). Inst. fuer Theoretische Physik; Tsukuba Univ., Ibaraki (Japan). Center for Computational Sciences; Pleiter, D. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany); Rakow, P.E.L. [Liverpool Univ. (United Kingdom). Theoretical Physics Div.; Schierholz, G. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Stueben, H. [Konrad-Zuse-Zentrum fuer Informationstechnik Berlin (Germany); Thomas, A.W.; Young, R.D. [Adelaide Univ. SA (Australia). School of Physics and Chemistry; Winter, F. [Edinburgh Univ. (United Kingdom). School of Physics and Astronomy; Regensburg Univ. (Germany). Inst. fuer Theoretische Physik
2010-12-15
By determining the quark momentum fractions of the octet baryons from N{sub f}=2+1 lattice simulations, we are able to predict the degree of charge symmetry violation in the parton distribution functions of the nucleon. This is of importance, not only as a probe of our understanding of the non-perturbative structure of the proton but also because such a violation constrains the accuracy of global ts to parton distribution functions and hence the accuracy with which, for example, cross sections at the LHC can be predicted. A violation of charge symmetry may also be critical in cases where symmetries are used to guide the search for physics beyond the Standard Model. (orig.)
Charge symmetry breaking in parton distribution functions from lattice QCD
International Nuclear Information System (INIS)
Horsley, R.; Zanotti, J.M.; Rakow, P.E.L.; Stueben, H.; Thomas, A.W.; Young, R.D.; Winter, F.; Regensburg Univ.
2010-12-01
By determining the quark momentum fractions of the octet baryons from N f =2+1 lattice simulations, we are able to predict the degree of charge symmetry violation in the parton distribution functions of the nucleon. This is of importance, not only as a probe of our understanding of the non-perturbative structure of the proton but also because such a violation constrains the accuracy of global ts to parton distribution functions and hence the accuracy with which, for example, cross sections at the LHC can be predicted. A violation of charge symmetry may also be critical in cases where symmetries are used to guide the search for physics beyond the Standard Model. (orig.)
Deep inelastic processes. Phenomenology. Quark-parton model
International Nuclear Information System (INIS)
Ioffe, B.L.; Lipatov, L.N.; Khoze, V.A.
1983-01-01
Main theoretical approaches and experimental results related to deep inelastic processes are systematically outlined: electroproduction, neutrino scattering on nucleon, electron-positron pairs annihilation into hadron γγ collisions, production of lepton pairs in hadron collisions with a large effective mass or hadrons with large transverse momenta. Kinematics and phenomenology, space-time description of deep inelastic processes, sum rules, parton and quark-parton models are considered. The experiment is briefly discussed in the book. It is performed from the stand point of comparing it with the theory, experimental data are given as of June, 1982. Since the time of accomplishing the study on the manuscript a number of new experimental results not changing however the statements made in the book appeared. Principal consists in experiments with colliding proton-antiproton beams in CERN, which resulted in discovery of intermediate W-bozon
Multi parton interactions with CMS detector at LHC
International Nuclear Information System (INIS)
Ciangottini, D.
2014-01-01
Multi parton interactions (MPI) are experiencing a growing popularity and are widely invoked to account for observations that cannot be explained otherwise: the activity of the Underlying Event, the rates for multiple heavy flavour production, the survival probability of large rapidity gaps in hard diffraction, etc. The definition, implementation and tuning of MPI models in Monte Carlo generators plays an important role for the LHC physics: a better definition of the collision dynamics and a better definition of background processes. CMS was involved into the MPI characterization from the beginning of the LHC data-taken, starting from the Underlying Event measurements in Minimum Bias events. With the large integrated luminosity available, the Double Parton Scattering (DPS) measurements (2 hard events in the same proton-proton collision) can be performed in different final states and at different energy scales. The proposed contribution is intended to review past and ongoing studies on MPI with the CMS detector, providing a common interpretation.
Unintegrated parton distributions and electroweak boson production at hadron colliders
Watt, G; Ryskin, M G
2004-01-01
We describe the use of doubly-unintegrated parton distributions in hadron-hadron collisions, using the (z,k_t)-factorisation prescription where the transverse momentum of the incoming parton is generated in the last evolution step. We apply this formalism to calculate the transverse momentum (P_T) distributions of produced W and Z bosons and compare the predictions to Tevatron Run 1 data. We find that the observed P_T distributions can be generated almost entirely by the leading order q_1 q_2 -> W,Z subprocesses, using known and universal doubly-unintegrated quark distributions. We also calculate the P_T distribution of the Standard Model Higgs boson at the LHC, where the dominant production mechanism is by gluon-gluon fusion.
Influence of diffractive interactions on cosmic ray air showers
International Nuclear Information System (INIS)
Luna, R.; Zepeda, A.; Garcia Canal, C.A.; Sciutto, S.J.
2004-01-01
A comparative study of commonly used hadronic collision simulation packages is presented. The characteristics of the products of hadron-nucleus collisions are analyzed from a general perspective, but focusing on their correlation with diffractive processes. One of the purposes of our work is to give quantitative estimations of the impact that different characteristics of the hadronic models have on air shower observables. Several sets of shower simulations using different settings for the parameters controlling the diffractive processes are used to analyze the correlations between diffractivity and shower observables. We find that the relative probability of diffractive processes during the shower development have a non-negligible influence over the longitudinal profile as well as the distribution of muons at ground level. The implications on experimental data analysis are discussed
Expected Increase of Activity of Eta Aquariids Meteor Shower
Kulikova, N. V.; Chepurova, V. M.
2018-04-01
Analysis of the results of modeling disintegration of Comet 1P/Halley after its flare in 1991 has allowed us to predict an increase of the activity of the associated Eta Aquariids meteor shower in April-May 2018.
Lethal carbon monoxide toxicity in a concrete shower unit.
Heath, Karen; Byard, Roger W
2018-05-23
A 47-year-old previously-well woman was found dead on the floor of a shower cubicle on a property in rural South Australia. The impression of the attending doctor and police was of collapse due to natural disease. Although there was significant stenosing coronary artery atherosclerosis found at autopsy, cherry pink discoloration of tissues prompted measurement of the blood carboxyhemoglobin level which was found to be 55%. The source of the gas was a poorly-maintained hot water heater that was mounted on the inside wall of the shower. Construction of the shower using an impermeable concrete rain water tank had caused gas accumulation when the water heater malfunctioned. Had lethal carbon monoxide exposure not been identified others using the same shower unit would also have been at risk.
Nitrogen fluorescence in air for observing extensive air showers
Keilhauer, B; Fraga, M; Matthews, J; Sakaki, N; Tameda, Y; Tsunesada, Y; Ulrich, A
2012-01-01
Extensive air showers initiate the fluorescence emissions from nitrogen molecules in air. The UV-light is emitted isotropically and can be used for observing the longitudinal development of extensive air showers in the atmosphere over tenth of kilometers. This measurement technique is well-established since it is exploited for many decades by several cosmic ray experiments. However, a fundamental aspect of the air shower analyses is the description of the fluorescence emission in dependence on varying atmospheric conditions. Different fluorescence yields affect directly the energy scaling of air shower reconstruction. In order to explore the various details of the nitrogen fluorescence emission in air, a few experimental groups have been performing dedicated measurements over the last decade. Most of the measurements are now finished. These experimental groups have been discussing their techniques and results in a series of \\emph{Air Fluorescence Workshops} commenced in 2002. At the 8$^{\\rm{th}}$ Air Fluoresc...
Evolution equations for connected and disconnected sea parton distributions
Liu, Keh-Fei
2017-08-01
It has been revealed from the path-integral formulation of the hadronic tensor that there are connected sea and disconnected sea partons. The former is responsible for the Gottfried sum rule violation primarily and evolves the same way as the valence. Therefore, the Dokshitzer-Gribov-Lipatov-Altarelli-Parisi evolution equations can be extended to accommodate them separately. We discuss its consequences and implications vis-á-vis lattice calculations.
Chiral perturbation theory for nucleon generalized parton distributions
Energy Technology Data Exchange (ETDEWEB)
Diehl, M. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Manashov, A. [Regensburg Univ. (Germany). Inst. fuer Physik 1 - Theoretische Physik]|[Sankt-Petersburg State Univ. (Russian Federation). Dept. of Theoretical Physics; Schaefer, A. [Regensburg Univ. (Germany). Inst. fuer Physik 1 - Theoretische Physik
2006-08-15
We analyze the moments of the isosinglet generalized parton distributions H, E, H, E of the nucleon in one-loop order of heavy-baryon chiral perturbation theory. We discuss in detail the construction of the operators in the effective theory that are required to obtain all corrections to a given order in the chiral power counting. The results will serve to improve the extrapolation of lattice results to the chiral limit. (orig.)
Revisiting parton evolution and the large-x limit
International Nuclear Information System (INIS)
Dokshitzer, Yu.L.; Marchesini, G.; Salam, G.P.
2006-01-01
This remark is part of an ongoing project to simplify the structure of the multi-loop anomalous dimensions for parton distributions and fragmentation functions. It answers the call for a 'structural explanation' of a 'very suggestive' relation found by Moch, Vermaseren and Vogt in the context of the x->1 behaviour of three-loop DIS anomalous dimensions. It also highlights further structure that remains to be fully explained
Italian Physical Society Justifying the QCD parton model
Veneziano, G
2018-01-01
I will focus my attention on the two papers I wrote with Roberto and Daniele Amati on justifying the QCD-improved parton model, a very basic tool used every day to estimate a variety of processes involving strong (as well as possibly other) interactions. While doing so, I will also touch on other occasions I had to work —or just interact— with Roberto during more than 30 years of our respective careers.
The new investigation of Kimber-Martin-Ryskin unintegrated partons
International Nuclear Information System (INIS)
Modarres, M.; Hosseinkhani, H.
2010-01-01
The three sets of conventional integrated parton distribution functions (PDFs) such as MSTW 2008 (Martin et al), GJR08 (Glueck et al) and Coquet.6 (Nadol sky et al) are used as the inputs to generate the unintegrated parton distribution functions (U PDFs) via the Kimber-Martin-Ryskin (Kmr) procedure and the results are compared with each other. The U PDFs are obtained for several values of the squared transverse momentum component of parton (k t 2 ) and the longitudinal momentum fraction (x). The various aspects of the PDFs and the U PDFs ratios of GJR08 and CTEQ6.6 to MSTW 2008 are analyzed and discussed. In addition to our previous justification (Modarres and Hosseinkani in Nucl Phys A 815:40, 2009) about the stability and the reliability of KMR UPDFs, it is observed here that they are more convergent in the larger values of the scale k t 2 (i.e. the suppression of discrepancies of different PDFs schemes) such that the UPDFs produced via the KMR approach are stable with respect to the variation of the input sets of PDFs and they also tend to a unique value by increasing the scale k t 2 . As the final justifications and conclusions, it seems that the UPDFs produced via the KMR prescription are sufficiently reliable to use in the related phenomenological computations. Our investigation is based on the comparison of the generated UPDFs via the KMR approach by using the MSTW2008, the G J R and the CT Eq.6 sets of the conventional integrated partons as inputs. It is carried out by comparing the ratios G J R/MSTW2008 and CT Eq.6/MSTW2008 and analyzing the results. Although all the UPDFs are well behaved and applicable, but at the higher transverse momentum k 2 t the results are considerable. The most convergent and the unique UPDFs are for the gluon distributions which are noticeably good. (author)
Fermi-Dirac statistics plus liquid description of quark partons
International Nuclear Information System (INIS)
Buccella, F.; Migliore, G.; Tibullo, V.
1995-01-01
A previous approach with Fermi-Dirac distributions for fermion partons is here improved to comply with the expected low x behaviour of structure functions. We are so able to get a fair description of the unpolarized and polarized structure functions of the nucleons as well as of neutrino data. We cannot reach definite conclusions, but confirm our suspicion of a relationship between the defects in Gottfried and spin sum rules. (orig.)
Towards the compression of parton densities through machine learning algorithms
Carrazza, Stefano
2016-01-01
One of the most fascinating challenges in the context of parton density function (PDF) is the determination of the best combined PDF uncertainty from individual PDF sets. Since 2014 multiple methodologies have been developed to achieve this goal. In this proceedings we first summarize the strategy adopted by the PDF4LHC15 recommendation and then, we discuss about a new approach to Monte Carlo PDF compression based on clustering through machine learning algorithms.
Implications of new deep inelastic scattering data for parton distributions
International Nuclear Information System (INIS)
Martin, A.D.; Stirling, W.J.; Roberts, R.G.
1988-01-01
We perform a next-to-leading order structure function F 2 analysis of μN and νN deep inelastic data in an attempt to resolve the disagreement between recent EMC (European muon collaboration effect) and BCDMS measurements of F 2 for μp scattering. Equally acceptable QCD fits are obtained including either set of μN data, but a comparison with Drell-Yan data appears to favour the parton distributions derived from the BCDMS data. (author)
Chiral dynamics and partonic structure at large transverse distances
Energy Technology Data Exchange (ETDEWEB)
Strikman, M. [Pennsylvania State Univ., University Park, PA (United States). Dept. of Physics; Weiss, C. [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States). Theory Center
2009-12-30
In this paper, we study large-distance contributions to the nucleon’s parton densities in the transverse coordinate (impact parameter) representation based on generalized parton distributions (GPDs). Chiral dynamics generates a distinct component of the partonic structure, located at momentum fractions x≲M_{π}/M_{N} and transverse distances b~1/M_{π}. We calculate this component using phenomenological pion exchange with a physical lower limit in b (the transverse “core” radius estimated from the nucleon’s axial form factor, R_{core}=0.55 fm) and demonstrate its universal character. This formulation preserves the basic picture of the “pion cloud” model of the nucleon’s sea quark distributions, while restricting its application to the region actually governed by chiral dynamics. It is found that (a) the large-distance component accounts for only ~1/3 of the measured antiquark flavor asymmetry d¯-u¯ at x~0.1; (b) the strange sea quarks s and s¯ are significantly more localized than the light antiquark sea; (c) the nucleon’s singlet quark size for x<0.1 is larger than its gluonic size, (b^{2})_{q+q¯}>(b^{2})_{g}, as suggested by the t-slopes of deeply-virtual Compton scattering and exclusive J/ψ production measured at HERA and FNAL. We show that our approach reproduces the general N_{c}-scaling of parton densities in QCD, thanks to the degeneracy of N and Δ intermediate states in the large-N_{c} limit. Finally, we also comment on the role of pionic configurations at large longitudinal distances and the limits of their applicability at small x.
Moments of nucleon spin-dependent generalized parton distributions
International Nuclear Information System (INIS)
Schroers, W.; Brower, R.C.; Dreher, P.; Edwards, R.; Fleming, G.; Haegler, Ph.; Heller, U.M.; Lippert, Th.; Negele, J.W.; Pochinsky, A.V.; Renner, D.B.; Richards, D.; Schilling, K.
2004-01-01
We present a lattice measurement of the first two moments of the spin-dependent GPD H∼(x, ξ, t). From these we obtain the axial coupling constant and the second moment of the spin-dependent forward parton distribution. The measurements are done in full QCD using Wilson fermions. In addition, we also present results from a first exploratory study of full QCD using Asqtad sea and domain-wall valence fermions
Timelike Compton scattering off the neutron and generalized parton distributions
Energy Technology Data Exchange (ETDEWEB)
Boer, M.; Guidal, M. [CNRS-IN2P3, Universite Paris-Sud, Institut de Physique Nucleaire d' Orsay, Orsay (France); Vanderhaeghen, M. [Johannes Gutenberg Universitaet, Institut fuer Kernphysik and PRISMA Cluster of Excellence, Mainz (Germany)
2016-02-15
We study the exclusive photoproduction of an electron-positron pair on a neutron target in the Jefferson Lab energy domain. The reaction consists of two processes: the Bethe-Heitler and the Timelike Compton Scattering. The latter process provides potentially access to the Generalized Parton Distributions (GPDs) of the nucleon. We calculate all the unpolarized, single- and double-spin observables of the reaction and study their sensitivities to GPDs. (orig.)
Three-Dimensional parton structure of light nuclei
Scopetta, Sergio; Del Dotto, Alessio; Kaptari, Leonid; Pace, Emanuele; Rinaldi, Matteo; Salmè, Giovanni
2018-03-01
Two promising directions beyond inclusive deep inelastic scattering experiments, aimed at unveiling the three dimensional structure of the bound nucleon, are reviewed, considering in particular the 3He nuclear target. The 3D structure in coordinate space can be accessed through deep exclusive processes, whose non-perturbative part is encoded in generalized parton distributions. In this way, the distribution of partons in the transverse plane can be obtained. As an example of a deep exclusive process, coherent deeply virtual Compton scattering off 3He nuclei, important to access the neutron generalized parton distributions (GPDs), will be discussed. In Impulse Approximation (IA), the sum of the two leading twist, quark helicity conserving GPDs of 3He, H and E, at low momentum transfer, turns out to be dominated by the neutron contribution. Besides, a technique, able to take into account the nuclear effects included in the Impulse Approximation analysis, has been developed. The spin dependent GPD \\tilde H of 3He is also found to be largely dominated, at low momentum transfer, by the neutron contribution. The knowledge of the GPDs H,E and \\tilde H of 3He is relevant for the planning of coherent DVCS off 3He measurements. Semi-inclusive deep inelastic scattering processes access the momentum space 3D structure parameterized through transverse momentum dependent parton distributions. A distorted spin-dependent spectral function has been recently introduced for 3He, in a non-relativistic framework, to take care of the final state interaction between the observed pion and the remnant in semi-inclusive deep inelastic electron scattering off transversely polarized 3He. The calculation of the Sivers and Collins single spin asymmetries for 3He, and a straightforward procedure to effectively take into account nuclear dynamics and final state interactions, will be reviewed. The Light-front dynamics generalization of the analysis is also addressed.
A Bayesian statistical method for particle identification in shower counters
International Nuclear Information System (INIS)
Takashimizu, N.; Kimura, A.; Shibata, A.; Sasaki, T.
2004-01-01
We report an attempt on identifying particles using a Bayesian statistical method. We have developed the mathematical model and software for this purpose. We tried to identify electrons and charged pions in shower counters using this method. We designed an ideal shower counter and studied the efficiency of identification using Monte Carlo simulation based on Geant4. Without having any other information, e.g. charges of particles which are given by tracking detectors, we have achieved 95% identifications of both particles
Microwave detection of air showers with the MIDAS experiment
International Nuclear Information System (INIS)
Privitera, Paolo; Alekotte, I.; Alvarez-Muniz, J.; Berlin, A.; Bertou, X.; Bogdan, M.; Bohacova, M.; Bonifazi, C.; Carvalho, W.R.; Mello Neto, J.R.T. de; Facal San Luis, P.; Genat, J.F.; Hollon, N.; Mills, E.; Monasor, M.; Reyes, L.C.; Rouille d'Orfeuil, B.; Santos, E.M.; Wayne, S.; Williams, C.
2011-01-01
Microwave emission from Extensive Air Showers could provide a novel technique for ultra-high energy cosmic rays detection over large area and with 100% duty cycle. We describe the design, performance and first results of the MIDAS (MIcrowave Detection of Air Showers) detector, a 4.5 m parabolic dish with 53 feeds in its focal plane, currently installed at the University of Chicago.
Electromagnetic-shower development in concrete and the punchthrough effect
International Nuclear Information System (INIS)
Mikocki, S.; Poirier, J.
1987-01-01
We present Monte Carlo calculations of the cascade curves in a concrete absorber for showers initiated by photons with energies from 10 MeV to 100 GeV. As an application of these curves, we estimate the punchthrough effect of photons and electrons in extensive-air-shower arrays which use a concrete absorber to identify muons. The results indicate that this effect is negligible
Nuclear parton distributions with the LHeC
International Nuclear Information System (INIS)
Klein, M.
2016-01-01
Nuclear parton distributions are far from being known today because of an infant experimental base. Based on design studies of the LHeC and using new simulations, of the inclusive neutral and charged current cross section measurements and of the strange, charm and beauty densities in nuclei, it is demonstrated how that energy frontier electron-ion collider would unfold the complete set of nuclear parton distributions (nPDFs) in a hugely extended kinematic range of deep inelastic scattering, extending in Bjorken x down to values near to 10 -6 in the perturbative domain. Together with a very precise and complete set of proton PDFs, the LHeC nPDFs will thoroughly change the theoretical understanding of parton dynamics and structure inside hadrons. This contribution is organised as follows: Section 2 summarises the status of the current nPDF determinations and presents a summary of the LHeC data simulation. Section 3 briefly summarises initial results of a study of the determination of PDFs in electron-deuteron scattering. Section 4 presents the nPDF simulation using LHeC data performed within an adapted EPS09 pQCD framework. Section 5 discusses the gluon distribution and the possible search for saturation of the rise of the gluon density towards low x. Section 6 includes the determination of the strange, charm and beauty distributions in nuclei from a future eA operation of the LHeC. A brief summary is presented in Section 7
Nelles, A.; Buitink, S.; Corstanje, A.; Enriquez, J. E.; Falcke, H.; Hörandel, J. R.; Rachen, J. P.; Rossetto, L.; Schellart, P.; Scholten, O.; ter Veen, S.; Thoudam, S.; Trinh, Gia
2015-01-01
The pattern of the radio emission of air showers is finely sampled with the Low-Frequency ARray (LOFAR). A set of 382 measured air showers is used to test a fast, analytic parameterization of the distribution of pulse powers. Using this parameterization we are able to reconstruct the shower axis and
Performance characteristics of a shower cooling tower
International Nuclear Information System (INIS)
Qi Xiaoni; Liu Zhenyan; Li Dandan
2007-01-01
This study was prompted by the need to design towers for applications in which, due to salt deposition on the packing and subsequent blockage, the use of tower packing is not practical. In contrast to conventional cooling towers, the cooling tower analyzed in this study is void of fill. By means of efficient atomization nozzles, a shower cooling tower (SCT) is possible to be applied in industry, which, in terms of water cooling, energy saving and equipment investing, is better than conventional packed cooling towers. However, no systematic thermodynamic numerical method could be found in the literature up to now. Based on the kinetic model and mass and heat transfer model, this paper has developed a one dimensional model for studying the motional process and evaporative cooling process occurring at the water droplet level in the SCT. The finite difference approach is used for three motional processes to obtain relative parameters in each different stage, and the possibility of the droplets being entrained outside the tower is fully analyzed. The accuracy of this model is checked by practical operational results from a full scale prototype in real conditions, and some exclusive factors that affect the cooling characteristics for the SCT are analyzed in detail. This study provides the theoretical foundation for practical application of the SCT in industry
Biofilms on Hospital Shower Hoses: Characterization and ...
Although the source of drinking water used in hospitals is commonly, biofilms on water pipelines are refuge to bacteria that survive different disinfection strategies. Drinking water (DW) biofilms are well known to harbor opportunistic pathogens, however, these biofilm communities remain poorly characterized by culture-independent approaches that circumvent the limitations of conventional monitoring efforts. Hence, the frequency of pathogens in DW biofilms and how biofilm members withstand high doses of disinfectants and/or chlorine residuals in the water supply remain speculative, but directly impact public health. The aim of this study was to characterize the composition of microbial communities growing on five hospital shower hoses using both culture-dependent and culture-independent techniques. Two different sequence-based methods were used to characterize the bacterial fractions: 16S rRNA gene sequencing of bacterial cultures and next generation sequencing of metagenomes. Based on the metagenomic data, we found that Mycobacterium-like species was the abundant bacterial taxa that overlapped among the five samples. We also recovered the draft genome of a novel Mycobacterium species, closely related to opportunistic pathogenic nontuberculous mycobacteria, M. rhodesiae and M. tusciae, in addition to other, less abundant species. In contrast, the cultured fraction was mostly affiliated to Proteobacteria, such as members of the Sphingomonas, Blastomonas and Porph
Extensive Air Showers with unusual structure
Directory of Open Access Journals (Sweden)
Beznosko Dmitriy
2017-01-01
Full Text Available A total of 23500 Extensive Air Showers (EAS with energies above ∼ 1016 eV have been detected during the ∼3500 hours of the Horizon-T (HT detectors system operations before Aug. 2016. Among these EAS, more than a thousand had an unusual spatial and temporary structure that showed pulses with several maxima (modals or modes from several detection points of the HT at the same time. These modes are separated in time from each other starting from tens to thousands of ns. These EAS have been called multi-modal. Analysis shows that the multi-modal EAS that have been detected by Horizon-T have the following properties: 1. Multi-modal EAS have energy above ∼1017 eV. 2. Pulses with several modes are located at large distances from the EAS axis. An overview of the collected data will be provided. General comments about the unusual structure of the multi-modal EAS will be presented.
Triple parton scatterings in high-energy proton-proton collisions arXiv
d'Enterria, David
2017-01-01
A generic expression to compute triple parton scattering cross sections in high-energy proton-proton (pp) collisions is presented as a function of the corresponding single parton cross sections and the transverse parton profile of the proton encoded in an effective parameter σeff,TPS. The value of σeff,TPS is closely related to the similar effective cross section that characterizes double parton scatterings, and amounts to σeff,TPS=12.5±4.5 mb. Estimates for triple charm (cc¯) and bottom (bb¯) production in pp collisions at LHC and FCC energies are presented based on next-to-next-to-leading-order perturbative calculations for single cc¯, bb¯ cross sections. At s≈100 TeV, about 15% of the pp collisions produce three cc¯ pairs from three different parton-parton scatterings.
Wee partons in large nuclei: From virtual dream to hard reality
International Nuclear Information System (INIS)
Venugopalan, R.
1995-01-01
We construct a weak coupling, many body theory to compute parton distributions in large nuclei for x much-lt A - 1/3 . The wee partons are highly coherent, non-Abelian Weizsaecker-Williams fields. Radiative corrections to the classical results axe discussed. The parton distributions for a single nucleus provide the initial conditions for the dynamical evolution of matter formed in ultrarelativistic nuclear collisions
Scale breaking effects in the quark-parton model for large P perpendicular phenomena
International Nuclear Information System (INIS)
Baier, R.; Petersson, B.
1977-01-01
We discuss how the scaling violations suggested by an asymptotically free parton model, i.e., the Q 2 -dependence of the transverse momentum of partons within hadrons may affect the parton model description of large p perpendicular phenomena. We show that such a mechanism can provide an explanation for the magnitude of the opposite side correlations and their dependence on the trigger momentum. (author)
Baryon form factors at high momentum transfer and generalized parton distributions
International Nuclear Information System (INIS)
Stoler, Paul
2002-01-01
Nucleon form factors at high momentum transfer t are treated in the framework of generalized parton distributions (GPD's). The possibility of obtaining information about parton high transverse momentum components by application of GPD's to form factors is discussed. This is illustrated by applying an ad hoc 2-body parton wave function to elastic nucleon form factors F 1 and F 2 , the N→Δ transition magnetic form factor G M * , and the wide angle Compton scattering form factor R 1
Double parton scattering in the ultraviolet. Addressing the double counting problem
Energy Technology Data Exchange (ETDEWEB)
Diehl, Markus [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Gaunt, Jonathan R. [Nikhef Theory Group, Amsterdam (Netherlands); Amsterdam VU Univ. (Netherlands)
2016-11-15
An important question in the theory of double parton scattering is how to incorporate the possibility of the parton pairs being generated perturbatively via 1→ 2splitting into the theory, whilst avoiding double counting with single parton scattering loop corrections. Here, we describe a consistent approach for solving this problem, which retains the notion of double parton distributions (DPDs) for individual hadrons. Further, we discuss the construction of appropriate model DPDs in our framework, and the use of these to compute the DPS part, presenting DPS 'luminosities' from our model DPDs for a few sample cases.
Charge symmetry breaking in spin dependent parton distributions and the Bjorken sum rule
International Nuclear Information System (INIS)
Cloet, I.C.; Horsley, R.; Londergan, J.T.
2012-04-01
We present the rst determination of charge symmetry violation (CSV) in the spin-dependent parton distribution functions of the nucleon. This is done by determining the rst two Mellin moments of the spin-dependent parton distribution functions of the octet baryons from N f =2+1 lattice simulations. The results are compared with predictions from quark models of nucleon structure. We discuss the contribution of partonic spin CSV to the Bjorken sum rule, which is important because the CSV contributions represent the only partonic corrections to the Bjorken sum rule.
Charge symmetry breaking in spin dependent parton distributions and the Bjorken sum rule
Energy Technology Data Exchange (ETDEWEB)
Cloet, I.C. [Adelaide Univ, SA (Australia). CSSM, School of Chemistry and Physics; Horsley, R. [Edinburgh Univ. (United Kingdom). School of Physics and Astronomy; Londergan, J.T. [Indiana Univ., Bloomington, IN (US). Dept. of Physics and Center for Exploration of Energy and Matter] (and others)
2012-04-15
We present the rst determination of charge symmetry violation (CSV) in the spin-dependent parton distribution functions of the nucleon. This is done by determining the rst two Mellin moments of the spin-dependent parton distribution functions of the octet baryons from N{sub f}=2+1 lattice simulations. The results are compared with predictions from quark models of nucleon structure. We discuss the contribution of partonic spin CSV to the Bjorken sum rule, which is important because the CSV contributions represent the only partonic corrections to the Bjorken sum rule.
Catalogue of Meteor Showers and Storms in Korean History
Directory of Open Access Journals (Sweden)
Sang-Hyeon Ahn
2004-03-01
Full Text Available We present a more complete and accurate catalogue of astronomical records for meteor showers and meteor storms appeared in primary official Korean history books, such as Samguk-sagi, Koryo-sa, Seungjeongwon-ilgi, and Choson-Wangjo-Sillok. So far the catalogue made by Imoto and Hasegawa in 1958 has been widely used in the international astronomical society. The catalogue is based on a report by Sekiguchi in 1917 that is mainly based on secondary history books. We observed that the catalogue has a number of errors in either dates or sources of the records. We have thoroughly checked the primary official history books, instead of the secondary ones, in order to make a corrected and extended catalogue. The catalogue contains 25 records of meteor storms, four records of intense meteor-showers, and five records of usual showers in Korean history. We also find that some of those records seem to correspond to some presently active meteor showers such as the Leonids, the Perseids, and the ¥ç-Aquarids-Orionids pair. However, a large number of those records do not correspond to such present showers. This catalogue we obtained can be useful for various astrophysical studies in the future.
Helicity-dependent generalized parton distributions for nonzero skewness
Energy Technology Data Exchange (ETDEWEB)
Mondal, Chandan [Chinese Academy of Sciences, Institute of Modern Physics, Lanzhou (China)
2017-09-15
We investigate the helicity-dependent generalized parton distributions (GPDs) in momentum as well as transverse position (impact) spaces for the u and d quarks in a proton when the momentum transfer in both the transverse and the longitudinal directions are nonzero. The GPDs are evaluated using the light-front wave functions of a quark-diquark model for nucleon where the wave functions are constructed by the soft-wall AdS/QCD correspondence. We also express the GPDs in the boost-invariant longitudinal position space. (orig.)
Multiparticle production in a two-component dual parton model
International Nuclear Information System (INIS)
Aurenche, P.; Bopp, F.W.; Capella, A.; Kwiecinski, J.; Maire, M.; Ranft, J.; Tran Thanh Van, J.
1992-01-01
The dual parton model (DPM) describes soft and semihard multiparticle production. The version of the DPM presented in this paper includes soft and hard mechanisms as well as diffractive processes. The model is formulated as a Monte Carlo event generator. We calculate in this model, in the energy range of the hadron colliders, rapidity distributions and the rise of the rapidity plateau with the collision energy, transverse-momentum distributions and the rise of average transverse momenta with the collision energy, multiplicity distributions in different pseudorapidity regions, and transverse-energy distributions. For most of these quantities we find a reasonable agreement with experimental data
Quark-parton model from dual topological unitarization
International Nuclear Information System (INIS)
Cohen-Tannoudji, G.; El Hassouni, A.; Kalinowski, J.; Peschanski, R.
1979-01-01
Topology, which occurs in the topological expansion of quantum chromodynamics (QCD) and in the dual topological unitarization (DTU) schemes, allows us to establish a quantitative correspondence between QCD and the dual S-matrix approaches. This topological correspondence, proposed by Veneziano and made more explicit in a recent paper for current-induced reactions, provides a clarifying and unifying quark-parton interpretation of soft inclusive processes. Precise predictions for inclusive cross sections in hadron-hadron collisions, structure functions of hadrons, and quark fragmentation functions including absolute normalizations are shown to agree with data. On a more theoretical ground the proposed scheme suggests a new approach to the confinement problem
Parton recombination model including resonance production. RL-78-040
International Nuclear Information System (INIS)
Roberts, R.G.; Hwa, R.C.; Matsuda, S.
1978-05-01
Possible effects of resonance production on the meson inclusive distribution in the fragmentation region are investigated in the framework of the parton recombination model. From a detailed study of the data on vector-meson production, a reliable ratio of the vector-to-pseudoscalar rates is determined. Then the influence of the decay of the vector mesons on the pseudoscalar spectrum is examined, and the effect found to be no more than 25% for x > 0.5. The normalization of the non-strange antiquark distributions are still higher than those in a quiescent proton. The agreement between the calculated results and data remain very good. 36 references
Current issues and challenges in global analysis of parton distributions
International Nuclear Information System (INIS)
Tung, Wu-Ki
2007-01-01
A new implementation of precise perturbative QCD calculation of deep inelastic scattering structure functions and cross sections, incorporating heavy quark mass effects, is applied to the global analysis of the full HERA I data sets on NC and CC cross sections, in conjunction with other experiments. Improved agreement between the NLO QCD theory and the global data sets are obtained. Comparison of the new results to that of previous analysis based on conventional zero-mass parton formalism is made. Exploratory work on implications of new fixed-target neutrino scattering and Drell-Yan data on global analysis is also discussed. (author)
Nonscaling parametrization of hadronic spectra and dual parton model
International Nuclear Information System (INIS)
Gaponenko, O.N.
2001-01-01
Using the popular Wdowczyk-Wolfendale parametrization (WW-parametrization) as an example one studies restrictions imposed by a dual parton model for different nonscaling parametrizations of the pulsed hadron spectra in soft hadron-hadron and hadron-nuclear interactions. One derived a new parametrization free from basic drawback of the WW-formulae. In the central range the determined parametrization show agreement with the Wdowczyk-Wolfendale formula, but in contrast to the last-named one it does not result in contradiction with the experiment due to fast reduction of inelastic factor reduction with energy increase [ru
Transverse momentum dependent parton distributions at small-x
Directory of Open Access Journals (Sweden)
Bo-Wen Xiao
2017-08-01
Full Text Available We study the transverse momentum dependent (TMD parton distributions at small-x in a consistent framework that takes into account the TMD evolution and small-x evolution simultaneously. The small-x evolution effects are included by computing the TMDs at appropriate scales in terms of the dipole scattering amplitudes, which obey the relevant Balitsky–Kovchegov equation. Meanwhile, the TMD evolution is obtained by resumming the Collins–Soper type large logarithms emerged from the calculations in small-x formalism into Sudakov factors.
Parton recombination model including resonance production. RL-78-040
Energy Technology Data Exchange (ETDEWEB)
Roberts, R. G.; Hwa, R. C.; Matsuda, S.
1978-05-01
Possible effects of resonance production on the meson inclusive distribution in the fragmentation region are investigated in the framework of the parton recombination model. From a detailed study of the data on vector-meson production, a reliable ratio of the vector-to-pseudoscalar rates is determined. Then the influence of the decay of the vector mesons on the pseudoscalar spectrum is examined, and the effect found to be no more than 25% for x > 0.5. The normalization of the non-strange antiquark distributions are still higher than those in a quiescent proton. The agreement between the calculated results and data remain very good. 36 references.
APFELgrid: a high performance tool for parton density determinations
Bertone, Valerio; Hartland, Nathan P.
We present a new software package designed to reduce the computational burden of hadron collider measurements in Parton Distribution Function (PDF) fits. The APFELgrid package converts interpolated weight tables provided by APPLgrid files into a more efficient format for PDF fitting by the combination with PDF and $\\alpha_s$ evolution factors provided by APFEL. This combination significantly reduces the number of operations required to perform the calculation of hadronic observables in PDF fits and simplifies the structure of the calculation into a readily optimised scalar product. We demonstrate that our technique can lead to a substantial speed improvement when compared to existing methods without any reduction in numerical accuracy.
Large high altitude air shower observatory (LHAASO) project
International Nuclear Information System (INIS)
He Huihai
2010-01-01
The Large High Altitude Air Shower Observatory (LHAASO) project focuses mainly on the study of 40 GeV-1 PeV gamma ray astronomy and 10 TeV-1 EeV cosmic ray physics. It consists of a 1 km 2 extensive air shower array with 40 000 m 2 muon detectors, 90,000m 2 water Cerenkov detector array, 5 000 m 2 shower core detector array and an air Cerenkov/fluorescence telescope array. Prototype detectors are designed with some of them already in operation. A prototype array of 1% size of LHAASO will be built at the Yangbajing Cosmic Ray Observatory and used to coincidently measure cosmic rays with the ARGO-YBJ experiment. (authors)
Personnel protective equipment total-encapsulating suit decontamination study using shower systems
International Nuclear Information System (INIS)
Menkhaus, D.E.
1991-01-01
This report documents an experimental evaluation, conducted at the Idaho National Engineering Laboratory, of a shower-based decontamination station for personnel wearing a Level A, total- encapsulating, chemical-protective suit. The decontamination station is used by personnel when egressing a dry, dusty environment contaminated with transuranic radionuclides. This system has the potential to minimize the risk of spreading the contaminants to clean areas. Two types of shower systems were evaluated, a drench shower and a multi-nozzle shower. A total-encapsulating suit, worn by personnel. was contaminated with soil containing 239 Pu. Pre- shower and post-shower contamination samples were collected and visual observations were made to evaluate the ability of the shower system to remove the contaminated dust and to obtain baseline data useful in designing a shower-based personnel decontamination system. 12 figs., 7 tabs
Delayed hadrons in air showers observed in Chacaltaya
International Nuclear Information System (INIS)
Kakimoto, Fumio
1984-01-01
Bolivian Air Shower Joint Experiment group has studied high energy interaction by measuring the aspect of vertical growth of air showers of 10 16 eV or more at Mt. Chacaltaya Space Physics Observatory at 5200 m above sea level and atmospheric depth of 550 g/cm 2 . The aspect of vertical growth of electrons from about 100 g/cm 2 to about 400 g/cm 2 of atmospheric depth obtained by the measured results of the time of arrival distribution of air Cherenkov radiation at Mt. Chacaltaya agreed with the one predicted from the enhanced 1/2 power of E model. Since the vertical growth of electrons and muons in about 10 17 eV air showers from the atmospheric apex was difficult to give the unified explanation with known interaction models, the University of Tokyo group has proposed a two-component model for air shower growth. If this second component is formed from heavy particles or heavy quantum state as parents, it should be observed as the component which arrives later in air shower. Thus, the measurement and experiment on the delayed hadrons in air showers have been started. In this paper, the experiment, analysis and results are reported. It is clear that the parent particles which caused such a phenomenon were not pions which were multiply generated by the interaction generally known. Therefore, an exact simulating calculation must be performed and compared with the experimental results to obtain the final conclusion from the measured results of this time. (Wakatsuki, Y.)
Double parton correlations in Light-Front constituent quark models
Directory of Open Access Journals (Sweden)
Rinaldi Matteo
2015-01-01
Full Text Available Double parton distribution functions (dPDF represent a tool to explore the 3D proton structure. They can be measured in high energy proton-proton and proton nucleus collisions and encode information on how partons inside a proton are correlated among each other. dPFDs are studied here in the valence quark region, by means of a constituent quark model, where two particle correlations are present without any additional prescription. This framework allows to understand the dynamical origin of the correlations and to clarify which, among the features of the results, are model independent. Use will be made of a relativistic light-front scheme, able to overcome some drawbacks of the previous calculation. Transverse momentum correlations, due to the exact treatment of the boosts, are predicted and analyzed. The role of spin correlations is also shown. Due to the covariance of the approach, some symmetries of the dPDFs are seen unambigously. For the valence sector, also the study of the QCD evolution of the model results, which can be performed safely thanks to the property of good support, has been also completed.
Uncertainties of predictions from parton distributions 1, experimental errors
Martin, A D; Stirling, William James; Thorne, R S; CERN. Geneva
2003-01-01
We determine the uncertainties on observables arising from the errors on the experimental data that are fitted in the global MRST2001 parton analysis. By diagonalizing the error matrix we produce sets of partons suitable for use within the framework of linear propagation of errors, which is the most convenient method for calculating the uncertainties. Despite the potential limitations of this approach we find that it can be made to work well in practice. This is confirmed by our alternative approach of using the more rigorous Lagrange multiplier method to determine the errors on physical quantities directly. As particular examples we determine the uncertainties on the predictions of the charged-current deep-inelastic structure functions, on the cross-sections for W production and for Higgs boson production via gluon--gluon fusion at the Tevatron and the LHC, on the ratio of W-minus to W-plus production at the LHC and on the moments of the non-singlet quark distributions. We discuss the corresponding uncertain...
LHAPDF6: parton density access in the LHC precision era
Energy Technology Data Exchange (ETDEWEB)
Buckley, Andy; Ferrando, James; Nordstroem, Karl [University of Glasgow, School of Physics and Astronomy, Glasgow (United Kingdom); Lloyd, Stephen [University of Edinburgh, School of Physics and Astronomy, Edinburgh (United Kingdom); Page, Ben [Universidad de Granada, Departamento de Fisica Teorica y del Cosmos y CAFPE, Granada (Spain); Ruefenacht, Martin [University of Edinburgh, School of Informatics, Edinburgh (United Kingdom); Schoenherr, Marek [Universitaet Zuerich, Physik-Institut, Zurich (Switzerland); Watt, Graeme [Durham University, Institute for Particle Physics Phenomenology, Durham (United Kingdom)
2015-03-01
The Fortran LHAPDF library has been a long-term workhorse in particle physics, providing standardised access to parton density functions for experimental and phenomenological purposes alike, following on from the venerable PDFLIB package. During Run 1 of the LHC, however, several fundamental limitations in LHAPDF's design have became deeply problematic, restricting the usability of the library for important physics-study procedures and providing dangerous avenues by which to silently obtain incorrect results. In this paper we present the LHAPDF 6 library, a ground-up re-engineering of the PDFLIB/LHAPDF paradigm for PDF access which removes all limits on use of concurrent PDF sets, massively reduces static memory requirements, offers improved CPU performance, and fixes fundamental bugs in multi-set access to PDF metadata. The new design, restricted for now to interpolated PDFs, uses centralised numerical routines and a powerful cascading metadata system to decouple software releases from provision of new PDF data and allow completely general parton content. More than 200 PDF sets have been migrated from LHAPDF 5 to the new universal data format, via a stringent quality control procedure. LHAPDF 6 is supported by many Monte Carlo generators and other physics programs, in some cases via a full set of compatibility routines, and is recommended for the demanding PDF access needs of LHC Run 2 and beyond. (orig.)
LHAPDF6: parton density access in the LHC precision era
International Nuclear Information System (INIS)
Buckley, Andy; Ferrando, James; Nordstroem, Karl; Lloyd, Stephen; Page, Ben; Ruefenacht, Martin; Schoenherr, Marek; Watt, Graeme
2015-01-01
The Fortran LHAPDF library has been a long-term workhorse in particle physics, providing standardised access to parton density functions for experimental and phenomenological purposes alike, following on from the venerable PDFLIB package. During Run 1 of the LHC, however, several fundamental limitations in LHAPDF's design have became deeply problematic, restricting the usability of the library for important physics-study procedures and providing dangerous avenues by which to silently obtain incorrect results. In this paper we present the LHAPDF 6 library, a ground-up re-engineering of the PDFLIB/LHAPDF paradigm for PDF access which removes all limits on use of concurrent PDF sets, massively reduces static memory requirements, offers improved CPU performance, and fixes fundamental bugs in multi-set access to PDF metadata. The new design, restricted for now to interpolated PDFs, uses centralised numerical routines and a powerful cascading metadata system to decouple software releases from provision of new PDF data and allow completely general parton content. More than 200 PDF sets have been migrated from LHAPDF 5 to the new universal data format, via a stringent quality control procedure. LHAPDF 6 is supported by many Monte Carlo generators and other physics programs, in some cases via a full set of compatibility routines, and is recommended for the demanding PDF access needs of LHC Run 2 and beyond. (orig.)
Parton fragmentation in the vacuum and in the medium
Albino, S.; Arleo, F.; Besson, Dave Z.; Brooks, William K.; Buschbeck, B.; Cacciari, M.; Christova, E.; Corcella, G.; D'Enterria, David G.; Dolejsi, Jiri; Domdey, S.; Estienne, M.; Hamacher, Klaus; Heinz, M.; Hicks, K.; Kettler, D.; Kumano, S.; Moch, S.O.; Muccifora, V.; Pacetti, S.; Perez-Ramos, R.; Pirner, H.J.; Pronko, Alexandre Pavlovich; Radici, M.; Rak, J.; Roland, C.; Rudolph, Gerald; Rurikova, Z.; Salgado, C.A.; Sapeta, S.; Saxon, David H.; Seidl, Ralf-Christian; Seuster, R.; Stratmann, M.; Tannenbaum, Michael J.; Tasevsky, M.; Trainor, T.; Traynor, D.; Werlen, M.; Zhou, C.
2008-01-01
We present the mini-proceedings of the workshop on ``Parton fragmentation in the vacuum and in the medium'' held at the European Centre for Theoretical Studies in Nuclear Physics and Related Areas (ECT*, Trento) in February 2008. The workshop gathered both theorists and experimentalists to discuss the current status of investigations of quark and gluon fragmentation into hadrons at different accelerator facilities (LEP, B-factories, JLab, HERA, RHIC, and Tevatron) as well as preparations for extension of these studies at the LHC. The main physics topics covered were: (i) light-quark and gluon fragmentation in the vacuum including theoretical (global fits analyses and MLLA) and experimental (data from e+e-, p-p, e-p collisions) aspects, (ii) strange and heavy-quark fragmentation, (iii) parton fragmentation in cold QCD matter (nuclear DIS), and (iv) medium-modified fragmentation in hot and dense QCD matter (high-energy nucleus-nucleus collisions). These mini-proceedings consist of an introduction and short summ...
Parton self-energies for general momentum-space anisotropy
Kasmaei, Babak S.; Strickland, Michael
2018-03-01
We introduce an efficient general method for calculating the self-energies, collective modes, and dispersion relations of quarks and gluons in a momentum-anisotropic high-temperature quark-gluon plasma. The method introduced is applicable to the most general classes of deformed anisotropic momentum distributions and the resulting self-energies are expressed in terms of a series of hypergeometric basis functions which are valid in the entire complex phase-velocity plane. Comparing to direct numerical integration of the self-energies, the proposed method is orders of magnitude faster and provides results with similar or better accuracy. To extend previous studies and demonstrate the application of the proposed method, we present numerical results for the parton self-energies and dispersion relations of partonic collective excitations for the case of an ellipsoidal momentum-space anisotropy. Finally, we also present, for the first time, the gluon unstable mode growth rate for the case of an ellipsoidal momentum-space anisotropy.
Heat recovery from shower water; Warmteterugwinning uit douchewater
Energy Technology Data Exchange (ETDEWEB)
Heidemans, J. [Hei-Tech, Emmen (Netherlands)
2011-09-15
With a payback period of several years, heat recovery from shower water in swimming pools but also in, for example, apartment buildings are an attractive form of energy saving. Possible are savings from 30 to 50% on energy, which is tested and proved by measurements in the heat exchanger of showers in a swimming pool in Denmark. [Dutch] Met een terugverdientijd van enkele jaren is warmteterugwinning uit douchewater in zwembaden maar ook in bijvoorbeeld sporthallen en appartementengebouwen een aantrekkelijke vorm van energiebesparing. Er kan een besparing worden gerealiseerd van 30 tot 50% op het energiegebruik van het douchewater. Metingen aan een douchewarmtewisselaar in een zwembad in Denemarken tonen dit aan.
Cosmic ray radio emission as air shower detection
International Nuclear Information System (INIS)
Curutiu, Alexandru; Rusu, Mircea; Isar, Gina; Zgura, Sorin
2004-01-01
The possibility of radio-detection of ultra-high energy cosmic rays (within the 10 to 100 MHz range) are discussed. Currently, air showers are detected by various methods, mainly based on particle detectors (KASCADE, Auger) or optical detection (Cerenkov radiation). Recently,to detect radio emission from cosmic ray air showers a method using electromagnetic radiation in low frequency domain (LOFAR) was proposed. We are investigating this possibility, using simulation codes created to investigate electromagnetic radiation of intricate antennae structure, for example fractal antennas. Some of the preliminary results will be communicated in this session. (authors)
Test results on reuse of reclaimed shower water - A summary
Verostko, Charles E.; Garcia, Rafael; Sauer, Richard; Reysa, Richard P.; Linton, Arthur T.
1989-01-01
Results are presented from tests to evaluate a microgravity whole body shower and waste water recovery system design for possible use on the Space Station. Several water recovery methods were tested, including phase change distillation, a thermoelectric hollow fiber membrane evaporation subsystem, and a reverse osmosis dynamic membrane system. Consideration is given to the test hardware, the types of soaps evaluated, the human response to showering with reclaimed water, chemical treatment for microbial control, the procedures for providing hygienic water, and the quality of water produced by the systems. All three of the waste water recovery systems tested successfully produced reclaimed water for reuse.
Shower fractal dimension analysis in a highly-granular calorimeter
Ruan, M
2014-01-01
We report on an investigation of the self-similar structure of particle showers recorded at a highly-granular calorimeter. On both simulated and experimental data, a strong correlation between the number of hits and the spatial scale of the readout channels is observed, from which we define the shower fractal dimension. The measured fractal dimension turns out to be strongly dependent on particle type, which enables new approaches for particle identification. A logarithmic dependence of the particle energy on the fractal dimension is also observed.
Unbiased global determination of parton distributions and their uncertainties at NNLO and at LO
Collaboration, The NNPDF; Ball, Richard D.; Bertone, Valerio; Cerutti, Francesco; Debbio, Luigi Del; Forte, Stefano; Guffanti, Alberto; Latorre, Jose I.; Rojo, Juan; Ubiali, Maria
2012-01-01
We present a determination of the parton distributions of the nucleon from a global set of hard scattering data using the NNPDF methodology at LO and NNLO in perturbative QCD, thereby generalizing to these orders the NNPDF2.1 NLO parton set. Heavy quark masses are included using the so-called FONLL
A new way of air shower detection: measuring the properties of cosmic rays with LOFAR
Nelles, A.; Buitink, S.; Corstanje, A.; Enriquez, J. E.; Falcke, H.; Hörandel, J. R.; Rachen, J. P.; Schellart, P.; Scholten, O.; ter Veen, S.; Thoudam, S.; Trinh, T.N.G.
2015-01-01
High-energy cosmic rays impinging onto the atmosphere of the Earth initiate cascades of secondary particles: extensive air showers. Many of the particles in a shower are electrons and positrons. During the development of the air shower and by interacting with the geomagnetic field, the
What the radio signal tells about the cosmic-ray air shower
Scholten, Olaf; de Vries, Krijn D.; Werner, Klaus
2013-01-01
The physics of radio emission from cosmic-ray induced air showers is shortly summarized. It will be shown that the radio signal at different distances from the shower axis provides complementary information on the longitudinal shower evolution, in particular the early part, and on the distribution
The search for extended air showers at the Jicamarca Radio Observatory
International Nuclear Information System (INIS)
Wahl, D.; Chau, J.; Galindo, F.; Huaman, A.; Solano, C. J.
2009-01-01
This paper presents the status of the project to detect extended air showers at the Jicamarca Radio Observatory. We report on detected anomalous signals and present a toy model to estimate at what altitudes we might expect to see air shower signals. According to this model, a significant number of high altitude horizontal air showers could be observed by radar techniques.
Comparison of methods for determining the centers of extensive air showers
International Nuclear Information System (INIS)
Poirier, J.; Funk, E.; Mikocki, S.; Rohrer, N.
1987-01-01
Monte Carlo techniques are used to generate extensive air shower data. Two methods of determining the core location of the shower have been investigated: the method of least squares and the method of maximizing the likelihood function. The likelihood function method gives a precision of shower center location two times better than the χ 2 method for small numbers of detected particles. (orig.)
Hadron Azimuthal Correlations and Mach-like Structures in a Partonic/Hadronic Transport Model
International Nuclear Information System (INIS)
Ma, G.L.; Zhang, S.; Ma, Y.G.; Cai, X.Z.; Chen, J.H.; He, Z.J.; Huang, H.Z.; Long, J.L.; Shen, W.Q.; Shi, X.H.; Zhong, C.; Zuo, J.X.
2007-01-01
With a multi-phase transport model (AMPT) with both partonic and hadronic interactions, two- and three-particle azimuthal correlations in Au + Au collisions at s NN =200 GeV have been studied by the mixing-event technique. A Mach-like structure has been observed in two- and three-particle correlations in central collisions. It has been found that both partonic and hadronic dynamical mechanisms contribute to the Mach-like structure. However, only hadronic rescattering is unable to reproduce experimental amplitude of Mach-like structure, and parton cascade process is indispensable. The results of three-particle correlation indicate a partonic Mach-like shock wave can be produced by strong parton cascade in central Au+Au collisions
Hadronic shower development in iron-scintillator tile calorimetry
Czech Academy of Sciences Publication Activity Database
Amaral, P.; Amorim, A.; Anderson, K.; Lokajíček, Miloš; Němeček, Stanislav
2000-01-01
Roč. 443, - (2000), s. 51-70 ISSN 0168-9002 R&D Projects: GA MPO RP-4210/69 Institutional research plan: CEZ:AV0Z1010920 Keywords : ATLAS Iron-Scintillator * hadron calorimeter * shower parametrisation * calorimetry * computer data analysis Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 0.964, year: 2000
Simple ADC unit for cosmic ray air shower experiments
Energy Technology Data Exchange (ETDEWEB)
Goswami, G C; Ghosh, B; Ghoshdastidar, M R; Sengupta, S K; Chaudhuri, N [North Bengal Univ., Darjeeling (India). Dept. of Physics
1982-02-01
The design of a new low cost analog-to-digital converter system is described. It is based upon the method of linearising the charging process of a storage condenser and is controlled by logic gates. Its tested characteristics have been found to be reliable for application in cosmic ray air shower experiments.
Shower Counters for SLAC experiments E142/E143
Energy Technology Data Exchange (ETDEWEB)
Borel, H; Grenier, P; Le Meur, J; Lombard, R; Lugol, J C; Marroncle, J; Morgenstern, J; Mouly, J P; Paul, B; Staley, F; Terrien, Y [CEA Centre d` Etudes de Saclay, 91 - Gif-sur-Yvette (France). Dept. d` Astrophysique, de la Physique des Particules, de la Physique Nucleaire et de l` Instrumentation Associee; Breton, V; Comptour, C; Crouau, M; Fonvieille, H; Roblin, Y; Savinel, G [Clermont-Ferrand-2 Univ., 63 - Aubiere (France); Gearhart, R [Stanford Linear Accelerator Center, Menlo Park, CA (United States)
1994-10-01
The two electromagnetic calorimeters each made of 200 lead glass blocks used at SLAC to discriminate between electrons and pions and to measure electron energies are described. Procedures to reconstruct electron showers and to calibrate calorimeters are treated as well as the calorimeter performance. (author). 6 refs., 10 figs.
Meteoroid Environment Modeling: the Meteoroid Engineering Model and Shower Forecasting
Moorhead, Althea V.
2017-01-01
The meteoroid environment is often divided conceptually into meteor showers plus a sporadic background component. The sporadic complex poses the bulk of the risk to spacecraft, but showers can produce significant short-term enhancements of the meteoroid flux. The Meteoroid Environment Office (MEO) has produced two environment models to handle these cases: the Meteoroid Engineering Model (MEM) and an annual meteor shower forecast. Both MEM and the forecast are used by multiple manned spaceflight projects in their meteoroid risk evaluation, and both tools are being revised to incorporate recent meteor velocity, density, and timing measurements. MEM describes the sporadic meteoroid complex and calculates the flux, speed, and directionality of the meteoroid environment relative to a user-supplied spacecraft trajectory, taking the spacecraft's motion into account. MEM is valid in the inner solar system and offers near-Earth and cis-lunar environments. While the current version of MEM offers a nominal meteoroid environment corresponding to a single meteoroid bulk density, the next version of MEMR3 will offer both flux uncertainties and a density distribution in addition to a revised near-Earth environment. We have updated the near-Earth meteor speed distribution and have made the first determination of uncertainty in this distribution. We have also derived a meteor density distribution from the work of Kikwaya et al. (2011). The annual meteor shower forecast takes the form of a report and data tables that can be used in conjunction with an existing MEM assessment. Fluxes are typically quoted to a constant limiting kinetic energy in order to comport with commonly used ballistic limit equations. For the 2017 annual forecast, the MEO substantially revised the list of showers and their characteristics using 14 years of meteor flux measurements from the Canadian Meteor Orbit Radar (CMOR). Defunct or insignificant showers were removed and the temporal profiles of many showers
Parton distribution functions and benchmark cross sections at NNLO
Energy Technology Data Exchange (ETDEWEB)
Alekhin, S. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany); Institute for High Energy Physics (IHEP), Protvino (Russian Federation); Bluemlein, J.; Moch, S. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany)
2012-02-15
We present a determination of parton distribution functions (ABM11) and the strong coupling constant {alpha}{sub s} at next-to-leading order and next-to-next-to-leading order (NNLO) in QCD based on world data for deep-inelastic scattering and fixed-target data for the Drell-Yan process. The analysis is performed in the fixed-flavor number scheme for n{sub f}=3,4,5 and uses the MS-scheme for {alpha}{sub s} and the heavy-quark masses. At NNLO we obtain the value {alpha}{sub s}(MZ)=0.1134{+-}0.0011. The fit results are used to compute benchmark cross sections at hadron colliders to NNLO accuracy and to compare to data from the LHC. (orig.)
Parton dynamics in hadronic processes. Final technical report
International Nuclear Information System (INIS)
Sukhatme, U.P.
1986-09-01
New physics results were obtained in four main areas. (1) Heavy flavor production, diffractive excitations and odderon effects were studied within the framework of the dual parton model. (2) Large n expansions for potential problems were investigated both in the bound state and scattering regimes. In the determination of energy eigenvalues, our shifted large N technique surpasses other analytic techniques in its accuracy, simplicity and wide range of applicability. (3) The property of supersymmetry was exploited to further enhance the convergence of large N expansions. (4) Cosmic ray data were re-analysed keeping unitarity bounds in mind. A ln 2 S energy dependence for the proton-proton total cross section seems to be favored
Polarized Parton Distributions at an Electron-Ion Collider
Ball, Richard D.; Guffanti, Alberto; Nocera, Emanuele R.; Ridolfi, Giovanni; Rojo, Juan
2014-01-01
We study the potential impact of inclusive deep-inelastic scattering data from a future electron-ion collider (EIC) on longitudinally polarized parton distribution (PDFs). We perform a PDF determination using the NNPDF methodology, based on sets of deep-inelastic EIC pseudodata, for different realistic choices of the electron and proton beam energies. We compare the results to our current polarized PDF set, NNPDFpol1.0, based on a fit to fixed-target inclusive DIS data. We show that the uncertainties on the first moments of the polarized quark singlet and gluon distributions are substantially reduced in comparison to NNPDFpol1.0, but also that more measurements may be needed to ultimately pin down the size of the gluon contribution to the nucleon spin.
Polarized parton distributions at an electron–ion collider
Energy Technology Data Exchange (ETDEWEB)
Ball, Richard D. [Tait Institute, University of Edinburgh, JCMB, KB, Mayfield Rd, Edinburgh EH9 3JZ, Scotland (United Kingdom); Forte, Stefano [Dipartimento di Fisica, Università di Milano and INFN, Sezione di Milano, Via Celoria 16, I-20133 Milano (Italy); Guffanti, Alberto [The Niels Bohr International Academy and Discovery Center, The Niels Bohr Institute, Blegdamsvej 17, DK-2100 Copenhagen (Denmark); Nocera, Emanuele R. [Dipartimento di Fisica, Università di Milano and INFN, Sezione di Milano, Via Celoria 16, I-20133 Milano (Italy); Ridolfi, Giovanni [Dipartimento di Fisica, Università di Genova and INFN, Sezione di Genova, Genova (Italy); Rojo, Juan [PH Department, TH Unit, CERN, CH-1211 Geneva 23 (Switzerland)
2014-01-20
We study the potential impact of inclusive deep-inelastic scattering data from a future electron–ion collider (EIC) on longitudinally polarized parton distributions (PDFs). We perform a PDF determination using the NNPDF methodology, based on sets of deep-inelastic EIC pseudodata, for different realistic choices of the electron and proton beam energies. We compare the results to our current polarized PDF set, NNPDFpol1.0, based on a fit to fixed-target inclusive DIS data. We show that the uncertainties on the first moments of the polarized quark singlet and gluon distributions are substantially reduced in comparison to NNPDFpol1.0, but also that more measurements may be needed to ultimately pin down the size of the gluon contribution to the nucleon spin.
Evolution of truncated moments of singlet parton distributions
International Nuclear Information System (INIS)
Forte, S.; Magnea, L.; Piccione, A.; Ridolfi, G.
2001-01-01
We define truncated Mellin moments of parton distributions by restricting the integration range over the Bjorken variable to the experimentally accessible subset x 0 ≤x≤1 of the allowed kinematic range 0≤x≤1. We derive the evolution equations satisfied by truncated moments in the general (singlet) case in terms of an infinite triangular matrix of anomalous dimensions which couple each truncated moment to all higher moments with orders differing by integers. We show that the evolution of any moment can be determined to arbitrarily good accuracy by truncating the system of coupled moments to a sufficiently large but finite size, and show how the equations can be solved in a way suitable for numerical applications. We discuss in detail the accuracy of the method in view of applications to precision phenomenology
Polarized parton distributions at an electron–ion collider
International Nuclear Information System (INIS)
Ball, Richard D.; Forte, Stefano; Guffanti, Alberto; Nocera, Emanuele R.; Ridolfi, Giovanni; Rojo, Juan
2014-01-01
We study the potential impact of inclusive deep-inelastic scattering data from a future electron–ion collider (EIC) on longitudinally polarized parton distributions (PDFs). We perform a PDF determination using the NNPDF methodology, based on sets of deep-inelastic EIC pseudodata, for different realistic choices of the electron and proton beam energies. We compare the results to our current polarized PDF set, NNPDFpol1.0, based on a fit to fixed-target inclusive DIS data. We show that the uncertainties on the first moments of the polarized quark singlet and gluon distributions are substantially reduced in comparison to NNPDFpol1.0, but also that more measurements may be needed to ultimately pin down the size of the gluon contribution to the nucleon spin
Electromagnetic contribution to charge symmetry violation in parton distributions
Directory of Open Access Journals (Sweden)
X.G. Wang
2016-02-01
Full Text Available We report a calculation of the combined effect of photon radiation and quark mass differences on charge symmetry violation (CSV in the parton distribution functions of the nucleon. Following a recent suggestion of Martin and Ryskin, the initial photon distribution is calculated in terms of coherent radiation from the proton as a whole, while the effect of the quark mass difference is based on a recent lattice QCD simulation. The distributions are then evolved to a scale at which they can be compared with experiment by including both QCD and QED radiation. Overall, at a scale of 5 GeV2, the total CSV effect on the phenomenologically important difference between the d and u-quark distributions is some 20% larger than the value based on quark mass differences alone. In total these sources of CSV account for approximately 40% of the NuTeV anomaly.
Resummation of singlet parton evolution at small x
Altarelli, Guido; Forte, Stefano; Altarelli, Guido; Ball, Richard D.; Forte, Stefano
2000-01-01
We propose an improvement of the splitting functions at small x which overcomes the apparent problems encountered by the BFKL approach. We obtain a stable expansion for the x-evolution function chi(M) near M=0 by including in it a sequence of terms derived from the one- and two-loop anomalous dimension gamma. The requirement of momentum conservation is always satisfied. The residual ambiguity on the splitting functions is effectively parameterized in terms of the value of lambda, which fixes the small x asymptotic behaviour x^-lambda of the singlet parton distributions. We derive from this improved evolution function an expansion of the splitting function which leads to good apparent convergence, and to a description of scaling violations valid both at large and small x.
Orbital angular momentum parton distributions in quark models
International Nuclear Information System (INIS)
Scopetta, S.; Vento, V.
2000-01-01
At the low energy, hadronic, scale we calculate Orbital Angular Momentum (OAM) twist-two parton distributions for the relativistic MIT bag model and for nonrelativistic quark models. We reach the scale of the data by leading order evolution in perturbative QCD. We confirm that the contribution of quarks and gluons OAM to the nucleon spin grows with Q 2 , and it can be relevant at the experimental scale, even if it is negligible at the hadronic scale, irrespective of the model used. The sign and shape of the quark OAM distribution at high Q 2 may depend strongly on the relative size of the OAM and spin distributions at the hadronic scale. Sizeable quark OAM distributions at the hadronic scale, as proposed by several authors, can produce the dominant contribution to the nucleon spin at high Q 2 . (author)
Parton distribution functions with QED corrections in the valon model
Mottaghizadeh, Marzieh; Taghavi Shahri, Fatemeh; Eslami, Parvin
2017-10-01
The parton distribution functions (PDFs) with QED corrections are obtained by solving the QCD ⊗QED DGLAP evolution equations in the framework of the "valon" model at the next-to-leading-order QCD and the leading-order QED approximations. Our results for the PDFs with QED corrections in this phenomenological model are in good agreement with the newly related CT14QED global fits code [Phys. Rev. D 93, 114015 (2016), 10.1103/PhysRevD.93.114015] and APFEL (NNPDF2.3QED) program [Comput. Phys. Commun. 185, 1647 (2014), 10.1016/j.cpc.2014.03.007] in a wide range of x =[10-5,1 ] and Q2=[0.283 ,108] GeV2 . The model calculations agree rather well with those codes. In the latter, we proposed a new method for studying the symmetry breaking of the sea quark distribution functions inside the proton.
Nucleon form factors, generalized parton distributions and quark angular momentum
Energy Technology Data Exchange (ETDEWEB)
Diehl, Markus [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Kroll, Peter [Bergische Univ., Wuppertal (Germany). Fachbereich Physik; Regensburg Univ. (Germany). Institut fuer Theoretische Physik
2013-02-15
We extract the individual contributions from u and d quarks to the Dirac and Pauli form factors of the proton, after a critical examination of the available measurements of electromagnetic nucleon form factors. From this data we determine generalized parton distributions for valence quarks, assuming a particular form for their functional dependence. The result allows us to study various aspects of nucleon structure in the valence region. In particular, we evaluate Ji's sum rule and estimate the total angular momentum carried by valence quarks at the scale {mu}=2 GeV to be J{sup u}{sub v}=0.230{sup +0.009}{sub -0.024} and J{sup d}{sub v}=-0.004{sup +0.010}{sub -0.016}.
Nucleon form factors, generalized parton distributions and quark angular momentum
International Nuclear Information System (INIS)
Diehl, Markus; Kroll, Peter; Regensburg Univ.
2013-02-01
We extract the individual contributions from u and d quarks to the Dirac and Pauli form factors of the proton, after a critical examination of the available measurements of electromagnetic nucleon form factors. From this data we determine generalized parton distributions for valence quarks, assuming a particular form for their functional dependence. The result allows us to study various aspects of nucleon structure in the valence region. In particular, we evaluate Ji's sum rule and estimate the total angular momentum carried by valence quarks at the scale μ=2 GeV to be J u v =0.230 +0.009 -0.024 and J d v =-0.004 +0.010 -0.016 .
Parton dynamics in hadronic processes. Technical progress report
International Nuclear Information System (INIS)
Sukhatme, U.P.
1985-02-01
We have studied the production of strangeness, charm and other heavy flavors in hadronic collisions in the framework of the dual parton model. This model allows us to understand why heavy flavors have ''delayed thresholds'' and noticeable production at large x values. We have also studied the leading particle effect in a variety of processes. We suggest the intriguing possibility that certain experimentally feasible non-diffractive processes involving soft gluons might have forward ''diffraction-like'' peak as x → 1. Finally, we have extended the techniques previously developed by us to get accurate analytic expressions for energy eigenstates. This enables us to get much-improved expansions for bound state wave functions, which compare remarkably well with numerical computations. 9 refs
QCD phenomenology of parton distribution functions at small x
International Nuclear Information System (INIS)
Tung, Wu-Ki
1990-09-01
The small x behavior of parton distributions is studied phenomenologically by examining in detail a series of QCD-evolved distribution sets obtained in a new global analysis of deep inelastic scattering and lepton-pair production experiments. The importance of 2-loop evolution is discussed. The main features and results of the global analysis are described. The range of small x behavior consistent with next-to-leading order QCD and current data is delineated. The extrapolated small x behavior is parameterized by effective Q-dependent power- and logarithmic-law parameters. Intriguing features of the evolution of these parameters with Q are presented. Alternative parametrizations based on the analytic solution for small x is also explored. 20 refs., 6 figs., 1 tab
Moments of nucleon generalized parton distributions from lattice QCD
International Nuclear Information System (INIS)
Alexandrou, C.; Cyprus Institute, Nicosia; Carbonell, J.; Harraud, P.A.; Papinutto, M.; Constantinou, M.; Kallidonis, C.; Guichon, P.; Jansen, K.; Korzec, T.; Humboldt Univ. Berlin
2011-07-01
We present results on the lower moments of the nucleon generalized parton distributions within lattice QCD using two dynamical flavors of degenerate twisted mass fermions. Our simulations are performed on lattices with three different values of the lattice spacings, namely a=0.089 fm, a=0.070 fm and a=0.056 fm, allowing the investigation of cut-off effects. The volume dependence is examined using simulations on two lattices of spatial length L=2.1 fm and L=2.8 fm. The simulations span pion masses in the range of 260-470 MeV. Our results are renormalized nonperturbatively and the values are given in the MS scheme at a scale μ=2 GeV. They are chirally extrapolated to the physical point in order to compare with experiment. The consequences of these results on the spin carried by the quarks in the nucleon are investigated. (orig.)
Transverse momentum-dependent parton distribution functions in lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Engelhardt, Michael G. [New Mexico State University; Musch, Bernhard U. [Tech. University Munich; Haegler, Philipp G. [Tech. University Munich; Negele, John W. [MIT; Schaefer, Andreas [Regensburg
2013-08-01
A fundamental structural property of the nucleon is the distribution of quark momenta, both parallel as well as perpendicular to its propagation. Experimentally, this information is accessible via selected processes such as semi-inclusive deep inelastic scattering (SIDIS) and the Drell-Yan process (DY), which can be parametrized in terms of transversemomentum-dependent parton distributions (TMDs). On the other hand, these distribution functions can be extracted from nucleon matrix elements of a certain class of bilocal quark operators in which the quarks are connected by a staple-shaped Wilson line serving to incorporate initial state (DY) or final state (SIDIS) interactions. A scheme for evaluating such matrix elements within lattice QCD is developed. This requires casting the calculation in a particular Lorentz frame, which is facilitated by a parametrization of the matrix elements in terms of invariant amplitudes. Exploratory results are presented for the time-reversal odd Sivers and Boer-Mulders transverse momentum shifts.
Hare, B. M.; Dwyer, J. R.; Winner, L. H.; Uman, M. A.; Jordan, D. M.; Kotovsky, D. A.; Caicedo, J. A.; Wilkes, R. A.; Carvalho, F. L.; Pilkey, J. T.; Ngin, T. K.; Gamerota, W. R.; Rassoul, H. K.
2017-01-01
It has been argued in the technical literature, and widely reported in the popular press, that cosmic ray air showers (CRASs) can initiate lightning via a mechanism known as relativistic runaway electron avalanche (RREA), where large numbers of high-energy and low-energy electrons can, somehow,
New measurements and analysis of high-energy muons in cosmic ray extensive air showers
International Nuclear Information System (INIS)
Sarkar, S.K.; Ghose, B.; Murkherjee, N.; Sanyal, S.; Chaudhuri, N.; Chhetri, R.; Basak, D.K.
1991-01-01
Cosmic ray air shower structure measurements and measurement of density and energy of air shower muons of a wide energy range simultaneously in individual air showers by two magnet spectrographs are presented. The measured muon densities have been used to compare with some of the previous measurements on muon densities in air showers of nearly the same size. The measured muon densities have also been applied for distinguishing between various interaction models and between light and heavier air shower primaries. In the air shower size range 10 4 -10 6 particles the present measurements do not provide evidence for iron primaries and the different interaction models seem not to be distinguishable by air shower observations. (Author)
Working Group I: Parton distributions: Summary report for the HERA LHC Workshop Proceedings
Energy Technology Data Exchange (ETDEWEB)
Dittmar, M.; /Zurich, ETH; Forte, S.; /Milan U. /INFN, Milan; Glazov, A.; /DESY; Moch, S.; /DESY, Zeuthen; Alekhin, S.; Altarelli, G.; Andersen, Jeppe R.; Ball, R.D.; Blumlein, J.; Bottcher, H.; Carli, T.; Ciafaloni, M.; Colferai, D.; Cooper-Sarkar, A.; Corcella, G.; Del Debbio, L.; Dissertori, G.; Feltesse, J.; Guffanti, A.; Gwenlan, C.; Huston, J.; /Zurich, ETH /DESY, Zeuthen /Serpukhov, IHEP /CERN /Rome III U. /INFN, Rome3 /Cambridge U. /Edinburgh U. /Florence U. /INFN, Florence /Oxford U. /DSM, DAPNIA, Saclay
2005-11-01
We provide an assessment of the impact of parton distributions on the determination of LHC processes, and of the accuracy with which parton distributions (PDFs) can be extracted from data, in particular from current and forthcoming HERA experiments. We give an overview of reference LHC processes and their associated PDF uncertainties, and study in detail W and Z production at the LHC.We discuss the precision which may be obtained from the analysis of existing HERA data, tests of consistency of HERA data from different experiments, and the combination of these data. We determine further improvements on PDFs which may be obtained from future HERA data (including measurements of F{sub L}), and from combining present and future HERA data with present and future hadron collider data. We review the current status of knowledge of higher (NNLO) QCD corrections to perturbative evolution and deep-inelastic scattering, and provide reference results for their impact on parton evolution, and we briefly examine non-perturbative models for parton distributions. We discuss the state-of-the art in global parton fits, we assess the impact on them of various kinds of data and of theoretical corrections, by providing benchmarks of Alekhin and MRST parton distributions and a CTEQ analysis of parton fit stability, and we briefly presents proposals for alternative approaches to parton fitting. We summarize the status of large and small x resummation, by providing estimates of the impact of large x resummation on parton fits, and a comparison of different approaches to small x resummation, for which we also discuss numerical techniques.
The effective cross section for double parton scattering within a holographic AdS/QCD approach
Energy Technology Data Exchange (ETDEWEB)
Traini, Marco, E-mail: marcoclaudio.traini@unitn.it [Institut de Physique Théorique, Université Paris Saclay, CEA, F-91191 Gif-sur-Yvette (France); INFN - TIFPA, Dipartimento di Fisica, Università degli Studi di Trento, Via Sommarive 14, I-38123 Povo, Trento (Italy); Rinaldi, Matteo [Departament de Fisica Teòrica, Universitat de València and Institut de Fisica Corpuscular, Consejo Superior de Investigaciones Científicas, 46100 Burjassot, València (Spain); Scopetta, Sergio [Dipartimento di Fisica e Geologia, Università degli Studi di Perugia, Via A. Pascoli, I-06123 (Italy); Istituto Nazionale di Fisica Nucleare, Sezione di Perugia, Perugia (Italy); Vento, Vicente [Departament de Fisica Teòrica, Universitat de València and Institut de Fisica Corpuscular, Consejo Superior de Investigaciones Científicas, 46100 Burjassot, València (Spain)
2017-05-10
A first attempt to apply the AdS/QCD framework for a bottom–up approach to the evaluation of the effective cross section for double parton scattering in proton–proton collisions is presented. The main goal is the analytic evaluation of the dependence of the effective cross section on the longitudinal momenta of the involved partons, obtained within the holographic Soft-Wall model. If measured in high-energy processes at hadron colliders, this momentum dependence could open a new window on 2-parton correlations in a proton.
Hard scattering on light nuclei: a convenient way to study parton correlations
International Nuclear Information System (INIS)
Calucci, G.; Treleani, D.
2011-01-01
The one-body partonic distributions in the hadrons are well investigated using electromagnetic or weak interactions. If we wish to exploit the same procedure to study the two-body distributions we should study the very rare events with multiple electromagnetic or weak interactions on the same hadron.The alternative is to study events with hard QCD double scattering of partons of the same hadron, such events become more and more abundant when the energy of the colliding hadrons grows. In fact at very high energies even the parton at small fractional momentum χ may suffer collisions with momentum transfer large enough to allow a perturbative treatment
Directory of Open Access Journals (Sweden)
Alexandrou Constantia
2017-01-01
Full Text Available We briefly discuss the current status of lattice QCD simulations and review selective results on nucleon observables focusing on recent developments in the lattice QCD evaluation of the nucleon form factors and radii, parton distribution functions and their moments, and the neutron electric dipole moment. Nucleon charges and moments of parton distribution functions are presented using simulations generated at physical values of the quark masses, while exploratory studies are performed for the parton distribution functions and the neutron electric dipole moment at heavier than physical value of the pion mass.
The Effect of New Shower Facilities on Physical Activity Behaviors of Employees: A Quasi-experiment.
Nehme, Eileen K; Pérez, Adriana; Ranjit, Nalini; Amick, Benjamin C; Kohl, Harold W
2017-02-01
This quasi-experimental study assessed the effects of new workplace showers on physical activity behaviors in a sample of downtown employees in Austin, TX. The study design was quasi-experimental with 2 comparison groups. Data were collected via internet-based surveys before and 4 months after shower installation at 1 worksite. Differences across study groups in the ranks of change in past-week minutes of physical activity from baseline to follow-up were assessed. Adjusted odds ratios and 95% confidence intervals for reporting an increase of ≥10 min past-week physical activity and workday physical activity among those with new showers and existing showers relative to those with no showers were also assessed. No significant differences in changes in physical activity from baseline to follow-up across study groups were found. One-quarter of participants with new workplace showers and 46.9% of those with existing workplace showers at baseline reported ever using the showers. This prospective study did not find significant changes in employee physical activity 4 months after installation of worksite showers. Worksite shower users were highly active at baseline, suggesting a possible early adopter effect, with potential for diffusion. Future studies may benefit from longer exposure times and larger samples.
Merging H/W/Z + 0 and 1 jet at NLO with no merging scale: a path to parton shower + NNLO matching
Hamilton, Keith; Oleari, Carlo; Zanderighi, Giulia
2013-01-01
We consider the POWHEG generator for a H/W/Z boson plus one jet, augmented with the recently proposed MiNLO method for the choice of scales and the inclusion of Sudakov form factors. Within this framework, the generator covers all the transverse-momentum region of the H/W/Z boson, i.e. no generation cuts are needed to obtain a finite result. By construction, the generator achieves NLO accuracy for distributions involving a finite (and relatively large) transverse momentum of the boson. We examine the conditions under which also the totally inclusive distributions (e.g. the boson rapidity distribution) achieve NLO accuracy. We find that a minimal modification of the MiNLO prescription is sufficient to achieve such accuracy. We thus construct a NLO generator for H/W/Z boson plus one jet production such that it smoothly merges into a NLO single boson production in the small transverse-momentum region. We notice that, by simply reweighting the boson rapidity distribution to NNLO predictions, we achieve a NNLO acc...
Resistive Plate Chamber Digitization in a Hadronic Shower Environment
Deng, Z.
2016-06-28
The CALICE Semi-Digital Hadron Calorimeter (SDHCAL) technological prototype is a sampling calorimeter using Glass Resistive Plate Chamber detectors with a three-threshold readout as the active medium. This technology is one of the two options proposed for the hadron calorimeter of the International Large Detector for the International Linear Collider. The prototype was exposed to beams of muons, electrons and pions of different energies at the CERN Super Proton Synchrotron. To be able to study the performance of such a calorimeter in future experiments it is important to ensure reliable simulation of its response. In this paper we present our prototype simulation performed with GEANT4 and the digitization procedure achieved with an algorithm called SimDigital. A detailed description of this algorithm is given and the methods to determinate its parameters using muon tracks and electromagnetic showers are explained. The comparison with hadronic shower data shows a good agreement up to 50 GeV. Discrepancies are ...
A silicon pad shower maximum detector for a Shashlik calorimeter
International Nuclear Information System (INIS)
Alvsvaag, S.J.; Maeland, O.A.; Klovning, A.
1995-01-01
The new luminosity monitor of the DELPHI detector, STIC (Small angle TIle Calorimeter), was built using a Shashlik technique. This technique does not provide longitudinal sampling of the showers, which limits the measurement of the direction of the incident particles and the e-π separation. For these reasons STIC was equipped with a Silicon Pad Shower Maximum Detector (SPSMD). In order to match the silicon detectors to the Shashlick read out by wavelength shifter (WLS) fibers, the silicon wafers had to be drilled with a precision better than 10μm without damaging the active area of the detectors. This paper describes the SPSMD with emphasis on the fabrication techniques and on the components used. Some preliminary results of the detector performance from data taken with a 45GeV electron beam at CERN are presented. (orig.)
How dense does parton matter get in Pb + Pb collisions at the CERN SPS?
International Nuclear Information System (INIS)
Geiger, K.; Mueller, B.
1998-01-01
The qualitative features of parton production through materialization in heavy-ion collisions are examined within perturbative QCD, and the magnitude of the resulting parton density created during the early stage of the collisions is estimated. The implications for 'anomalous' J/ψ suppression observed in Pb + Pb collisions at the CERN SPS are discussed. The A-dependence of absorption of J/ψ by (partonic) comovers is steeper than assumed in most phenomenological models, because the absorption process is dominated by quasi-perturbative QCD interactions. The argument is supported by results recently obtained in the framework of the parton cascade model. Significant 'anomalous' suppression for Pb + Pb collisions at the CERN-SPS are predicted, but not for S + U collisions. (author)
On the Impact of Tsallis Statistics on Cosmic Ray Showers
Directory of Open Access Journals (Sweden)
M. Abrahão
2016-01-01
Full Text Available We investigate the impact of the Tsallis nonextensive statistics introduced by intrinsic temperature fluctuations in p-Air ultrahigh energy interactions on observables of cosmic ray showers, such as the slant depth of the maximum Xmax and the muon number on the ground Nμ. The results show that these observables are significantly affected by temperature fluctuations and agree qualitatively with the predictions of Heitler model.
The AMY experiment: Microwave emission from air shower plasmas
Directory of Open Access Journals (Sweden)
Alvarez-Muñiz J.
2016-01-01
Full Text Available You The Air Microwave Yield (AMY experiment investigate the molecular bremsstrahlung radiation emitted in the GHz frequency range from an electron beam induced air-shower. The measurements have been performed at the Beam Test Facility (BTF of Frascati INFN National Laboratories with a 510 MeV electron beam in a wide frequency range between 1 and 20 GHz. We present the apparatus and the results of the tests performed.
Composition sensitivity of the Auger observatory through inclined showers
International Nuclear Information System (INIS)
Ave, M.; Watson, A.A.; Hinton, J.A.; Vazquez, R.A.; Zas, E.
2003-01-01
We report a calculation of the expected rate of inclined air showers induced by ultra high-energy cosmic rays to be obtained by the Auger Southern Observatory assuming different mass compositions. We describe some features that can be used to distinguish photons at energies as high as 10 20 eV. The discrimination of photons at such energies will help to test some models of the origin of ultrahigh-energy cosmic rays
On the formation of meteor showers of comet Halley
International Nuclear Information System (INIS)
Babadzhanov, P.B.; Obrubov, J.V.; Pushkarev, A.N.; Hajduk, A.
1987-01-01
The orbits of test particles ejected from the nucleus of Halley comet at its perihelion passage in 1910 with different velocities are studied for the next three passages of the comet up to 2134 taking into consideration perturbations from all planets. Some characteristics of the stream formation are presented. The calculations show that the return of the comet to its perihelion cannot produce an immediate influence on the activity of its meteor showers. (author). 2 figs., 1 tab., 13 refs
A swimming pool array for ultra high energy showers
Yodh, Gaurang B.; Shoup, Anthony; Barwick, Steve; Goodman, Jordan A.
1992-11-01
A very preliminary design concept for an array using water Cherenkov counters, built out of commercially available backyard swimming pools, to sample the electromagnetic and muonic components of ultra high energy showers at large lateral distances is presented. The expected performance of the pools is estimated using the observed lateral distributions by scintillator and water Cherenkov arrays at energies above 1019 eV and simulations.
Fast simulation of electromagnetic showers in the ZEUS calorimeter
International Nuclear Information System (INIS)
Peso, J. del; Ros, E.
1991-02-01
We present a fast Monte Carlo algorithm for the generation of electromagnetic showers in the uranium-scintillator sampling calorimeter of the ZEUS experiment. This algorithm includes a simulation of longitudinal and transverse profiles, their fluctuations and the correlation between these fluctuations as well. The tuning of this fast Monte Carlo with data generated with EGS is described and its performance together with some applications is discussed. (orig.)
On Combining High and Low Q2 Information on the Polarized Parton Densities
International Nuclear Information System (INIS)
Leader, Elliot; Stamenov, Dimiter B.
2000-01-01
We draw attention to some problems in the combined use of high-Q 2 deep inelastic scattering (DIS) data and low-Q 2 hyperon β-decay data in the determination of the polarized parton densities. We explain why factorization schemes like the JET or AB schemes are the simplest in which to study the implications of the DIS parton densities for the physics of the low-Q 2 region. (author)
Testing partonic charge symmetry at a high-energy electron collider
International Nuclear Information System (INIS)
Hobbs, T.J.; Londergan, J.T.; Murdock, D.P.; Thomas, A.W.
2011-01-01
We examine the possibility that one could measure partonic charge symmetry violation (CSV) by comparing neutrino or antineutrino production through charged-current reactions induced by electrons or positrons at a possible electron collider at the LHC. We calculate the magnitude of CSV that might be expected at such a facility. We show that this is likely to be a several percent effect, substantially larger than the typical CSV effects expected for partonic reactions.
Hautmann, F.; Jung, H.; Krämer, M.; Mulders, P. J.; Nocera, E. R.; Rogers, T. C.; Signori, A.
2014-12-01
Transverse-momentum-dependent distributions (TMDs) are extensions of collinear parton distributions and are important in high-energy physics from both theoretical and phenomenological points of view. In this manual we introduce the library , a tool to collect transverse-momentum-dependent parton distribution functions (TMD PDFs) and fragmentation functions (TMD FFs) together with an online plotting tool, TMDplotter. We provide a description of the program components and of the different physical frameworks the user can access via the available parameterisations.
Parameterized Shower Simulation in Lelaps: a Comparison with Geant4
International Nuclear Information System (INIS)
Langeveld, Willy G.J.
2003-01-01
The detector simulation toolkit Lelaps[1] simulates electromagnetic and hadronic showers in calorimetric detector elements of high-energy particle detectors using a parameterization based on the algorithms originally developed by Grindhammer and Peters[2] and Bock et al.[3]. The primary motivations of the present paper are to verify the implementation of the parameterization, to explore regions of energy where the parameterization is valid and to serve as a basis for further improvement of the algorithm. To this end, we compared the Lelaps simulation to a detailed simulation provided by Geant4[4]. A number of different calorimeters, both electromagnetic and hadronic, were implemented in both programs. Longitudinal and radial shower profiles and their fluctuations were obtained from Geant4 over a wide energy range and compared with those obtained from Lelaps. Generally the longitudinal shower profiles are found to be in good agreement in a large part of the energy range, with poorer results at energies below about 300 MeV. Radial profiles agree well in homogeneous detectors, but are somewhat deficient in segmented ones. These deficiencies are discussed
Mesospheric sodium over Gadanki during Geminid meteor shower 2007
Lokanadham, B.; Rakesh Chandra, N.; Bhaskara Rao, S. Vijaya; Raghunath, K.; Yellaiah, G.
Resonance LIDAR system at Gadanki has been used for observing the mesospheric sodium during the night of 12-13 Dec 2007 when the peak activity of Geminid meteor shower occurred. Geminid meteor shower is observed along with the co-located MST radar in the altitude range 80-110 km. Sodium density profiles have been obtained with a vertical resolution of 300 m and a temporal resolution of 120 s with sodium resonance scattering LIDAR system. The sodium layers were found to exist in the altitude range 90-100 km. The enhanced Geminid meteor rates were recorded with the co-located MST radar in the same altitude range. The sodium concentration in the atmospheric altitude of ~93 km is estimated to be 2000 per cc where the meteoric concentration of Geminid is maximum and reduced to around 800 on the non activity of Geminid. These observations showed that the sodium levels in the E-region are found to be increasing during meteor shower nights at least by a factor of two.
EGS4, Electron Photon Shower Simulation by Monte-Carlo
International Nuclear Information System (INIS)
1998-01-01
1 - Description of program or function: The EGS code system is one of a chain of three codes designed to solve the electromagnetic shower problem by Monte Carlo simulation. This chain makes possible simulation of almost any electron-photon transport problem conceivable. The structure of the system, with its global features, modular form, and structured programming, is readily adaptable to virtually any interfacing scheme that is desired on the part of the user. EGS4 is a package of subroutines plus block data with a flexible user interface. This allows for greater flexibility without requiring the user to be overly familiar with the internal details of the code. Combining this with the macro facility capabilities of the Mortran3 language, this reduces the likelihood that user edits will introduce bugs into the code. EGS4 uses material cross section and branching ratio data created and fit by the companion code, PEGS4. EGS4 allows for the implementation of importance sampling and other variance reduction techniques such as leading particle biasing, splitting, path length biasing, Russian roulette, etc. 2 - Method of solution: EGS employs the Monte Carlo method of solution. It allows all of the fundamental processes to be included and arbitrary geometries can be treated, also. Other minor processes, such as photoneutron production, can be added as a further generalization. Since showers develop randomly according to the quantum laws of probability, each shower is different. We again are led to the Monte Carlo method. 3 - Restrictions on the complexity of the problem: None noted
Producing EGS4 shower displays with the Unified Graphics System
International Nuclear Information System (INIS)
Cowan, R.F.
1990-01-01
The EGS4 Code System has been coupled with the SLAC Unified Graphics System in such a manner as to provide a means for displaying showers on UGS77-supported devices. This is most easily accomplished by attaching an auxiliary subprogram package (SHOWGRAF) to existing EGS4 User Codes and making use of a graphics display or a post-processor code called EGS4PL. SHOWGRAF may be used to create shower displays directly on interactive IBM 5080 color display devices, supporting three-dimensional rotations, translations, and zoom features, and providing illustration of particle types and energies by color and/or intensity. Alternatively, SHOWGRAF may be used to record a two-dimensional projection of the shower in a device-independent graphics file. The EGS4PL post-processor may then be used to convert this file into device-dependent graphics code for any UGS77-supported device. Options exist within EGS4PL that allow for two-dimensional translations and zoom, for creating line structure to indicate particle types and energies, and for optional display of particles by type. All of this is facilitated by means of the command processor EGS4PL EXEC together with new options (5080 and PDEV) with the standard EGS4IN EXEC routine for running EGS4 interactively under VM/SP. 6 refs
International Nuclear Information System (INIS)
Anselmino, M.; Avakian, H.; Boer, D.; Bradamante, F.; Burkardt, M.; Chen, J.P.; Cisbani, E.; Contalbrigo, M.; Crabb, D.; Dutta, D.; Gamberg, L.; Gao, H.; Hasch, D.; Huang, J.; Huang, M.; Kang, Z.; Keppel, C.; Laskaris, G.; Liang, Z.-T.; Liu, M.X.; Makins, N.; Mckeown, R.D.; Metz, A.; Meziani, Z.-E.; Musch, B.; Peng, J.-C.; Prokudin, A.; Qian, X.; Qiang, Y.; Qiu, J.W.; Rossi, P.; Schweitzer, P.; Soffer, J.; Sulkosky, V.; Wang, Y.; Xiao, B.; Ye, Q.; Ye, Q.-J.; Yuan, F.; Zhan, X.; Zhang, Y.; Zheng, W.; Zhou, J.
2011-01-01
We present a summary of a recent workshop held at Duke University on Partonic Transverse Momentum in Hadrons: Quark Spin-Orbit Correlations and Quark-Gluon Interactions. The transverse momentum dependent parton distribution functions (TMDs), parton-to-hadron fragmentation functions, and multi-parton correlation functions, were discussed extensively at the Duke workshop. In this paper, we summarize first the theoretical issues concerning the study of partonic structure of hadrons at a future electron-ion collider (EIC) with emphasis on the TMDs. We then present simulation results on experimental studies of TMDs through measurements of single spin asymmetries (SSA) from semi-inclusive deep-inelastic scattering (SIDIS) processes with an EIC, and discuss the requirement of the detector for SIDIS measurements. The dynamics of parton correlations in the nucleon is further explored via a study of SSA in D ((bar D)) production at large transverse momenta with the aim of accessing the unexplored tri-gluon correlation functions. The workshop participants identified the SSA measurements in SIDIS as a golden program to study TMDs in both the sea and valence quark regions and to study the role of gluons, with the Sivers asymmetry measurements as examples. Such measurements will lead to major advancement in our understanding of TMDs in the valence quark region, and more importantly also allow for the investigation of TMDs in the sea quark region along with a study of their evolution.
Parton Distributions based on a Maximally Consistent Dataset
Rojo, Juan
2016-04-01
The choice of data that enters a global QCD analysis can have a substantial impact on the resulting parton distributions and their predictions for collider observables. One of the main reasons for this has to do with the possible presence of inconsistencies, either internal within an experiment or external between different experiments. In order to assess the robustness of the global fit, different definitions of a conservative PDF set, that is, a PDF set based on a maximally consistent dataset, have been introduced. However, these approaches are typically affected by theory biases in the selection of the dataset. In this contribution, after a brief overview of recent NNPDF developments, we propose a new, fully objective, definition of a conservative PDF set, based on the Bayesian reweighting approach. Using the new NNPDF3.0 framework, we produce various conservative sets, which turn out to be mutually in agreement within the respective PDF uncertainties, as well as with the global fit. We explore some of their implications for LHC phenomenology, finding also good consistency with the global fit result. These results provide a non-trivial validation test of the new NNPDF3.0 fitting methodology, and indicate that possible inconsistencies in the fitted dataset do not affect substantially the global fit PDFs.
The ABM parton distributions tuned to LHC data
International Nuclear Information System (INIS)
Alekhin, S.; Bluemlein, J.; Moch, S.; Hamburg Univ.
2013-10-01
We present a global fit of parton distributions at next-to-next-to-leading order (NNLO) in QCD. The fit is based on the world data for deep-inelastic scattering, fixed-target data for the Drell-Yan process and includes, for the first time, data from the Large Hadron Collider (LHC) for the Drell-Yan process and the hadro-production of top-quark pairs. The analysis applies the fixed-flavor number scheme for n f =3,4,5, uses the MS scheme for the strong coupling α s and the heavy-quark masses and keeps full account of the correlations among all non-perturbative parameters. At NNLO this returns the values of α s (M Z )=0.1132±0.0011 and m t (pole)=171.2±2.4 GeV for the top-quark pole mass. The fit results are used to compute benchmark cross sections for Higgs production at the LHC to NNLO accuracy. We compare our results to those obtained by other groups and show that differences can be linked to different theoretical descriptions of the underlying physical processes.
Problem with parton-model descriptions of neutrino data
International Nuclear Information System (INIS)
Barger, V.; Weiler, T.; Phillips, R.J.N.
1976-01-01
The present results from νN and ν-barN scattering experiments appear to place conflicting requirements on conventional quark--parton models. The strong rise with energy of /sup ν-barN and sigma/sup ν-barN/sub T//sigma/ sup νN//sub T/ seems to require new-particle (charm) production from valence quarks in ν-barN interactions, whereas the x dependence of dimuon events and the dsigma/dy anomaly suggest that ν-barN charm production comes from sea quarks. No single model gives a fully satisfactory explanation of all the present data. We draw attention to this problem, illustrate the conflicting requirements of data with particular models, and discuss possible resolutions. The closest overall compromise with the present data is obtained with the six-quark model, using charm-quark masses m/sub c/ = 1.5 GeV, m/sub b/ = 5 GeV, and a higher t-quark mass
The ABM parton distributions tuned to LHC data
Energy Technology Data Exchange (ETDEWEB)
Alekhin, S. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany); Institute for High Energy Physics, Protvino (Russian Federation); Bluemlein, J. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany); Moch, S. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany); Hamburg Univ. (Germany). II. Inst. fuer Theoretische Physik
2013-10-15
We present a global fit of parton distributions at next-to-next-to-leading order (NNLO) in QCD. The fit is based on the world data for deep-inelastic scattering, fixed-target data for the Drell-Yan process and includes, for the first time, data from the Large Hadron Collider (LHC) for the Drell-Yan process and the hadro-production of top-quark pairs. The analysis applies the fixed-flavor number scheme for n{sub f}=3,4,5, uses the MS scheme for the strong coupling {alpha}{sub s} and the heavy-quark masses and keeps full account of the correlations among all non-perturbative parameters. At NNLO this returns the values of {alpha}{sub s}(M{sub Z})=0.1132{+-}0.0011 and m{sub t}(pole)=171.2{+-}2.4 GeV for the top-quark pole mass. The fit results are used to compute benchmark cross sections for Higgs production at the LHC to NNLO accuracy. We compare our results to those obtained by other groups and show that differences can be linked to different theoretical descriptions of the underlying physical processes.
Medium Modifications of Hadron Properties and Partonic Processes
Energy Technology Data Exchange (ETDEWEB)
Brooks, W. K.; Strauch, S.; Tsushima, K.
2011-06-01
Chiral symmetry is one of the most fundamental symmetries in QCD. It is closely connected to hadron properties in the nuclear medium via the reduction of the quark condensate
Obtaining parton distribution functions from self-organizing maps
International Nuclear Information System (INIS)
Honkanen, H.; Liuti, S.; Loitiere, Y.C.; Brogan, D.; Reynolds, P.
2007-01-01
We present an alternative algorithm to global fitting procedures to construct Parton Distribution Functions parametrizations. The proposed algorithm uses Self-Organizing Maps which at variance with the standard Neural Networks, are based on competitive-learning. Self-Organizing Maps generate a non-uniform projection from a high dimensional data space onto a low dimensional one (usually 1 or 2 dimensions) by clustering similar PDF representations together. The SOMs are trained on progressively narrower selections of data samples. The selection criterion is that of convergence towards a neighborhood of the experimental data. All available data sets on deep inelastic scattering in the kinematical region of 0.001 ≤ x ≤ 0.75, and 1 ≤ Q 2 ≤ 100 GeV 2 , with a cut on the final state invariant mass, W 2 ≥ 10 GeV 2 were implemented. The proposed fitting procedure, at variance with standard neural network approaches, allows for an increased control of the systematic bias by enabling the user to directly control the data selection procedure at various stages of the process. (author)
Dual parametrization of generalized parton distributions in two equivalent representations
International Nuclear Information System (INIS)
Müller, D.; Polyakov, M.V.; Semenov-Tian-Shansky, K.M.
2015-01-01
The dual parametrization and the Mellin-Barnes integral approach represent two frameworks for handling the double partial wave expansion of generalized parton distributions (GPDs) in the conformal partial waves and in the t-channel SO(3) partial waves. Within the dual parametrization framework, GPDs are represented as integral convolutions of forward-like functions whose Mellin moments generate the conformal moments of GPDs. The Mellin-Barnes integral approach is based on the analytic continuation of the GPD conformal moments to the complex values of the conformal spin. GPDs are then represented as the Mellin-Barnes-type integrals in the complex conformal spin plane. In this paper we explicitly show the equivalence of these two independently developed GPD representations. Furthermore, we clarify the notions of the J=0 fixed pole and the D-form factor. We also provide some insight into GPD modeling and map the phenomenologically successful Kumerički-Müller GPD model to the dual parametrization framework by presenting the set of the corresponding forward-like functions. We also build up the reparametrization procedure allowing to recast the double distribution representation of GPDs in the Mellin-Barnes integral framework and present the explicit formula for mapping double distributions into the space of double partial wave amplitudes with complex conformal spin.
Parton distributions and lattice QCD calculations: A community white paper
Lin, Huey-Wen; Nocera, Emanuele R.; Olness, Fred; Orginos, Kostas; Rojo, Juan; Accardi, Alberto; Alexandrou, Constantia; Bacchetta, Alessandro; Bozzi, Giuseppe; Chen, Jiunn-Wei; Collins, Sara; Cooper-Sarkar, Amanda; Constantinou, Martha; Del Debbio, Luigi; Engelhardt, Michael; Green, Jeremy; Gupta, Rajan; Harland-Lang, Lucian A.; Ishikawa, Tomomi; Kusina, Aleksander; Liu, Keh-Fei; Liuti, Simonetta; Monahan, Christopher; Nadolsky, Pavel; Qiu, Jian-Wei; Schienbein, Ingo; Schierholz, Gerrit; Thorne, Robert S.; Vogelsang, Werner; Wittig, Hartmut; Yuan, C.-P.; Zanotti, James
2018-05-01
In the framework of quantum chromodynamics (QCD), parton distribution functions (PDFs) quantify how the momentum and spin of a hadron are divided among its quark and gluon constituents. Two main approaches exist to determine PDFs. The first approach, based on QCD factorization theorems, realizes a QCD analysis of a suitable set of hard-scattering measurements, often using a variety of hadronic observables. The second approach, based on first-principle operator definitions of PDFs, uses lattice QCD to compute directly some PDF-related quantities, such as their moments. Motivated by recent progress in both approaches, in this document we present an overview of lattice-QCD and global-analysis techniques used to determine unpolarized and polarized proton PDFs and their moments. We provide benchmark numbers to validate present and future lattice-QCD calculations and we illustrate how they could be used to reduce the PDF uncertainties in current unpolarized and polarized global analyses. This document represents a first step towards establishing a common language between the two communities, to foster dialogue and to further improve our knowledge of PDFs.
EPPS16: nuclear parton distributions with LHC data
Energy Technology Data Exchange (ETDEWEB)
Eskola, Kari J. [University of Jyvaskyla, Department of Physics, P.O. Box 35, University of Jyvaskyla (Finland); Helsinki Institute of Physics, P.O. Box 64, University of Helsinki (Finland); Paakkinen, Petja [University of Jyvaskyla, Department of Physics, P.O. Box 35, University of Jyvaskyla (Finland); Paukkunen, Hannu [University of Jyvaskyla, Department of Physics, P.O. Box 35, University of Jyvaskyla (Finland); Helsinki Institute of Physics, P.O. Box 64, University of Helsinki (Finland); Universidade de Santiago de Compostela, Instituto Galego de Fisica de Altas Enerxias (IGFAE), Galicia (Spain); Salgado, Carlos A. [Universidade de Santiago de Compostela, Instituto Galego de Fisica de Altas Enerxias (IGFAE), Galicia (Spain)
2017-03-15
We introduce a global analysis of collinearly factorized nuclear parton distribution functions (PDFs) including, for the first time, data constraints from LHC proton-lead collisions. In comparison to our previous analysis, EPS09, where data only from charged-lepton-nucleus deep inelastic scattering (DIS), Drell-Yan (DY) dilepton production in proton-nucleus collisions and inclusive pion production in deuteron-nucleus collisions were the input, we now increase the variety of data constraints to cover also neutrino-nucleus DIS and low-mass DY production in pion-nucleus collisions. The new LHC data significantly extend the kinematic reach of the data constraints. We now allow much more freedom for the flavor dependence of nuclear effects than in other currently available analyses. As a result, especially the uncertainty estimates are more objective flavor by flavor. The neutrino DIS plays a pivotal role in obtaining a mutually consistent behavior for both up and down valence quarks, and the LHC dijet data clearly constrain gluons at large momentum fraction. Mainly for insufficient statistics, the pion-nucleus DY and heavy-gauge-boson production in proton-lead collisions impose less visible constraints. The outcome - a new set of next-to-leading order nuclear PDFs called EPPS16 - is made available for applications in high-energy nuclear collisions. (orig.)
Monte-Carlo simulation of hadronic showers. Part 3: The ANI prototype calorimeter
International Nuclear Information System (INIS)
Amatuni, Ts.A.; Mamidjanyan, E.A.; Sanossyan, Kh.N.
1992-01-01
Hadronic showers initiated by 0.5, 1, 2, 4, 5, 7, 10, 12, 15, 20, 22 and 30 eV incident protons in the ANI prototype calorimeter are simulated. The energy deposition (longitudinal and lateral) for these showers are calculated. Lateral shower profiles for 0.5, 5 and 20 TeV primary energies are presented and parametrized. The leakage from the calorimeter is estimated. 19 refs
Pion and proton showers in the CALICE scintillator-steel analogue hadron calorimeter
Bilki, B.; Xia, L.; Eigen, G.; Thomson, M.A.; Ward, D.R.; Benchekroun, D.; Hoummada, A.; Khoulaki, Y.; Chang, S.; Khan, A.; Kim, D.H.; Kong, D.J.; Oh, Y.D.; Blazey, G.C.; Dyshkant, A.; Francis, K.; Lima, J.G.R.; Salcido, R.; Zutshi, V.; Salvatore, F.; Kawagoe, K.; Miyazaki, Y.; Sudo, Y.; Suehara, T.; Tomita, T.; Ueno, H.; Yoshioka, T.; Apostolakis, J.; Dannheim, D.; Folger, G.; Ivantchenko, V.; Klempt, W.; Lucaci-Timoce, A. -I.; Ribon, A.; Schlatter, D.; Sicking, E.; Uzhinskiy, V.; Giraud, J.; Grondin, D.; Hostachy, J. -Y.; Morin, L.; Brianne, E.; Cornett, U.; David, D.; Ebrahimi, A.; Falley, G.; Gadow, K.; Göttlicher, P.; Günter, C.; Hartbrich, O.; Hermberg, B.; Karstensen, S.; Krivan, F.; Krüger, K.; Lu, S.; Lutz, B.; Morozov, S.; Morgunov, V.; Neubüser, C.; Reinecke, M.; Sefkow, F.; Smirnov, P.; Tran, H.L.; Buhmann, P.; Garutti, E.; Laurien, S.; Matysek, M.; Ramilli, M.; Briggl, K.; Eckert, P.; Harion, T.; Munwes, Y.; Schultz-Coulon, H. -Ch.; Shen, W.; Stamen, R.; Norbeck, E.; Northacker, D.; van Doren, B.; Wilson, G.W.; Wing, M.; Combaret, C.; Caponetto, L.; Eté, R.; Grenier, G.; Han, R.; Ianigro, J.C.; Kieffer, R.; Laktineh, I.; Lumb, N.; Mathez, H.; Mirabito, L.; Petrukhin, A.; Steen, A.; Antequera, J. Berenguer; Calvo Alamillo, E.; Fouz, M. -C.; Marin, J.; Puerta-Pelayo, J.; Verdugo, A.; Corriveau, F.; Bobchenko, B.; Chistov, R.; Chadeeva, M.; Danilov, M.; Drutskoy, A.; Epifantsev, A.; Markin, O.; Mironov, D.; Mizuk, R.; Novikov, E.; Rusinov, V.; Tarkovsky, E.; Besson, D.; Buzhan, P.; Ilyin, A.; Popova, E.; Gabriel, M.; Kiesling, C.; van der Kolk, N.; Simon, F.; Soldner, C.; Szalay, M.; Tesar, M.; Weuste, L.; Amjad, M.S.; Bonis, J.; Conforti Di Lorenzo, S.; Cornebise, P.; Dulucq, F.; Fleury, J.; Frisson, T.; Martin-Chassard, G.; Poschl, R.; Raux, L.; Richard, F.; Pöschl, R.; Rouëné, J.; Seguin-Moreau, N.; de la Taille, Ch.; Anduze, M.; Boudry, V.; Brient, J-C.; Clerc, C.; Cornat, R.; Frotin, M.; Gastaldi, F.; Matthieu, A.; Mora de Freitas, P.; Musat, G.; Ruan, M.; Videau, H.; Zacek, J.; Cvach, J.; Gallus, P.; Havranek, M.; Janata, M.; Kvasnicka, J.; Lednicky, D.; Marcisovsky, M.; Polak, I.; Popule, J.; Tomasek, L.; Tomasek, M.; Sicho, P.; Smolik, J.; Vrba, V.; Zalesak, J.; Jeans, D.; Weber, S.
2015-04-28
Showers produced by positive hadrons in the highly granular CALICE scintillatorsteel analogue hadronic calorimeter were studied. The experimental data were collected at CERN and FNAL for single particles with initial momenta from 10 to 80 GeV/c. The calorimeter response and resolution and spatial characteristics of shower development for proton- and pion-induced showers for test beam data and simulations using GEANT4 version 9.6 are compared.
Three-dimensional parametrization of photon-initiated high energy showers
International Nuclear Information System (INIS)
De Angelis, A.
1988-01-01
A three-dimensional parametrization of photon-initiated showers in a homogeneous absorber is presented. The form, suggested by a model assimilating the transverse shower development to a random walk process, displays a simple scaling with the primary energy, and is very suitable for numerical integration. The parameters are explicitly calculated for the case of showers in SF5 lead glass, and the results are compared with the explicit simulation by GEANT3.11. Fields of application are investigated. (orig.)
Monte-Carlo simulation of hadronic showers. Part 3: The ANI prototype calorimeter
Energy Technology Data Exchange (ETDEWEB)
Amatuni, Ts A; Mamidjanyan, E A; Sanossyan, Kh N
1993-12-31
Hadronic showers initiated by 0.5, 1, 2, 4, 5, 7, 10, 12, 15, 20, 22 and 30 eV incident protons in the ANI prototype calorimeter are simulated. The energy deposition (longitudinal and lateral) for these showers are calculated. Lateral shower profiles for 0.5, 5 and 20 TeV primary energies are presented and parametrized. The leakage from the calorimeter is estimated. 19 refs.
Directory of Open Access Journals (Sweden)
Sertac Ozturk
2014-01-01
Full Text Available Being able to distinguish parton pair type in a dijet event could significantly improve the search for new particles that are predicted by the theories beyond the Standard Model at the Large Hadron Collider. To explore whether parton pair types manifesting themselves as a dijet event could be distinguished on an event-by-event basis, I performed a simulation based study considering observable jet variables. I found that using a multivariate approach can filter out about 80% of the other parton pairs while keeping more than half of the quark-quark or gluon-gluon parton pairs in an inclusive QCD dijet distribution. The effects of event-by-event parton pair tagging for dijet resonance searches were also investigated and I found that improvement on signal significance after applying parton pair tagging can reach up to 4 times for gluon-gluon resonances.
Nonpointlike-parton model with asymptotic scaling and with scaling violationat moderate Q2 values
International Nuclear Information System (INIS)
Chen, C.K.
1981-01-01
A nonpointlike-parton model is formulated on the basis of the assumption of energy-independent total cross sections of partons and the current-algebra sum rules. No specific strong-interaction Lagrangian density is introduced in this approach. This model predicts asymptotic scaling for the inelastic structure functions of nucleons on the one hand and scaling violation at moderate Q 2 values on the other hand. The predicted scaling-violation patterns at moderate Q 2 values are consistent with the observed scaling-violation patterns. A numerical fit of F 2 functions is performed in order to demonstrate that the predicted scaling-violation patterns of this model at moderate Q 2 values fit the data, and to see how the predicted asymptotic scaling behavior sets in at various x values. Explicit analytic forms of F 2 functions are obtained from this numerical fit, and are compared in detail with the analytic forms of F 2 functions obtained from the numerical fit of the quantum-chromodynamics (QCD) parton model. This comparison shows that this nonpointlike-parton model fits the data better than the QCD parton model, especially at large and small x values. Nachtman moments are computed from the F 2 functions of this model and are shown to agree with data well. It is also shown that the two-dimensional plot of the logarithm of a nonsinglet moment versus the logarithm of another such moment is not a good way to distinguish this nonpointlike-parton model from the QCD parton model
General-purpose event generators for LHC physics
Buckley, Andy; Gieseke, Stefan; Grellscheid, David; Hoche, Stefan; Hoeth, Hendrik; Krauss, Frank; Lonnblad, Leif; Nurse, Emily; Richardson, Peter; Schumann, Steffen; Seymour, Michael H.; Sjostrand, Torbjorn; Skands, Peter; Webber, Bryan
2011-01-01
We review the physics basis, main features and use of general-purpose Monte Carlo event generators for the simulation of proton-proton collisions at the Large Hadron Collider. Topics included are: the generation of hard-scattering matrix elements for processes of interest, at both leading and next-to-leading QCD perturbative order; their matching to approximate treatments of higher orders based on the showering approximation; the parton and dipole shower formulations; parton distribution functions for event generators; non-perturbative aspects such as soft QCD collisions, the underlying event and diffractive processes; the string and cluster models for hadron formation; the treatment of hadron and tau decays; the inclusion of QED radiation and beyond-Standard-Model processes. We describe the principal features of the ARIADNE, Herwig++, PYTHIA 8 and SHERPA generators, together with the Rivet and Professor validation and tuning tools, and discuss the physics philosophy behind the proper use of these generators ...
Association between meteor showers and asteroids using multivariate criteria
Dumitru, B. A.; Birlan, M.; Popescu, M.; Nedelcu, D. A.
2017-10-01
Context. Meteoroid streams are fragments of matter produced by comets or asteroids which intersects the orbit of Earth. Meteor showers are produced when Earth intersects these streams of matter. The discoveries of active asteroids and extinct comets open a new view of the relation between these objects as possible parent bodies at the origin of meteor showers. Aims: The aim of this work is to identify the asteroids that can produce or re-populate meteoroid streams by determining the similarity of their orbits and orbital evolution over 10 000 yr. Methods: The identification was carried out by evaluating several well known D-criteria metrics, the orbits being taken from the IAU Meteor Data Center database and from IAU Minor Planet Center. Finally, we analyzed the physical properties and the orbital stability (in the Lyapunov time sense) of the candidates as well as their possible relationship with meteorites. Results: 206 near-Earth asteroids (NEAs) were associated as possible parent bodies with 28 meteor showers, according to at least two of the criterion used. 50 of them satisfied all the criteria. Notable finds are: binary asteroid 2000UG11 associated with Andromedids (AND), while the tumbling asteroid (4179)Toutatis could be associated with October Capricornids (OCC). Other possible good candidates are 2004TG10, 2008EY5, 2010CF55, 2010TU149 and 2014OY1. These objects have low albedo, therefore can be primitive objects. Asteroid 2007LW19 which is a fast rotator and most probably has monolithic structure and so its physical characteristic does not support the association found based on the dynamical criteria.
Transition effect of extensive air showers in thick scintillators
International Nuclear Information System (INIS)
Lidvanskij, A.S.; Navarra, Dzh.; Chernyaev, A.V.
1985-01-01
Transition effect of extensive air showers has been measured by means of the ''Kover'' facility of the Baksan neutrino laboratory. The transition effect represents the ratio of ''scintillation'' particle density detected with detectors and particle density under the facility concrete roof (21 gxcm -2 ). Measurement results are compared with data obtained by means of the program of electron-photon cascade gaming. Good agreement of experimental and calculational data has been obtained. It follows from the data in the paper that the transition effect for one scintillator in the absence of roof can be produced by the gaming rather reliably
Dipole showers and automated NLO matching in Herwig++
International Nuclear Information System (INIS)
Plaetzer, Simon; Gieseke, Stefan
2011-09-01
We report on the implementation of a coherent dipole shower algorithm along with an automated implementation for dipole subtraction and for performing POWHEG- and MC rate at NLO-type matching to next-to-leading order (NLO) calculations. Both programs are implemented as add-on modules to the event generator HERWIG++. A preliminary tune of parameters to data acquired at LEP, HERA and Drell-Yan pair production at the Tevatron has been performed, and we find an overall very good description which is slightly improved by the NLO matching. (orig.)
Dipole showers and automated NLO matching in Herwig++
Energy Technology Data Exchange (ETDEWEB)
Plaetzer, Simon [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Gieseke, Stefan [Karlsruher Institut fuer Technologie, Karlsruhe (Germany). Inst. fuer Theoretische Teilchenphysik
2011-09-15
We report on the implementation of a coherent dipole shower algorithm along with an automated implementation for dipole subtraction and for performing POWHEG- and MC rate at NLO-type matching to next-to-leading order (NLO) calculations. Both programs are implemented as add-on modules to the event generator HERWIG++. A preliminary tune of parameters to data acquired at LEP, HERA and Drell-Yan pair production at the Tevatron has been performed, and we find an overall very good description which is slightly improved by the NLO matching. (orig.)
Sidereal anisotropy of small air showers observed at Mt. Norikura
International Nuclear Information System (INIS)
Nagashima, K.; Sakakibara, S.; Fujimoto, K.; Fujii, Z.; Ueno, H.; Kondo, I.
1977-01-01
Observation of small air showers has been continued from August 1970, using a part of the multidirectional cosmic ray telescope at Mt. Norikura. Most significant result obtained from this observation was a sidereal diurnal anisotropy of amplitude 0.051 +- 0.004% with maximum at 1.0 +- 0.5 h, which showed a persistent trend over six years. Based on the results of the observation together with those obtained by Gombosi et al. and Fenton et al., a tentative model of sidereal anisotropies is presented. (author)
D-meson production according to the parton model and their detection in ALICE
Kalliokoski, Tuomo; Trzaska, Wladyslaw
2007-01-01
Modern understanding in particle physics is constructed over lay- ers and layers of work. Most of the work was done during last century, starting from the quantum mechanics. Modern theoretical basis is the parton model, which is constructed from three independent parts: distribution of momentum to partons inside hadron, partonic cross-sections from QCD and from fragmentation of parton to hadrons. All of these parts are discussed in this work. Future experiments are aiming for higher energies and/or greater number of intresting events than what previous experiments were capable to gain. Main example of this is LHC and ALICE-experiment on it in CERN. While simulations have benefited greatly from fast increase of computing power during last few decades. With the following assumptions, p$_t$ $>$ 1 GeV, fixed QCD scale Q = 5 GeV, massless quarks and only gluon-gluon channel in partonic cross-section and $\\delta$-function fragmentation, the lowest order simulations for production of D-meson with midrapidity y = 0 a...
Energy Technology Data Exchange (ETDEWEB)
Nachtmann, O., E-mail: O.Nachtmann@thphys.uni-heidelberg.de
2014-11-15
We review ideas on the structure of the QCD vacuum which had served as motivation for the discussion of various non-standard QCD effects in high-energy reactions in articles from 1984 to 1995. These effects include, in particular, transverse-momentum and spin correlations in the Drell–Yan process and soft photon production in hadron–hadron collisions. We discuss the relation of the approach introduced in the above-mentioned articles to the approach, developed later, using transverse-momentum-dependent parton distributions (TDMs). The latter approach is a special case of our more general one which allows for parton entanglement in high-energy reactions. We discuss signatures of parton entanglement in the Drell–Yan reaction. Also for Higgs-boson production in pp collisions via gluon–gluon annihilation effects of entanglement of the two gluons are discussed and are found to be potentially important. These effects can be looked for in the current LHC experiments. In our opinion studying parton-entanglement effects in high-energy reactions is, on the one hand, very worthwhile by itself and, on the other hand, it allows to perform quantitative tests of standard factorisation assumptions. Clearly, the experimental observation of parton-entanglement effects in the Drell–Yan reaction and/or in Higgs-boson production would have a great impact on our understanding how QCD works in high-energy collisions.
The transverse momentum of partons in large psub(T) processes
International Nuclear Information System (INIS)
Chase, M.K.
1977-11-01
An approximate method is used to investigate the effects of parton transverse momentum in large psub(T) particle production within the framework of hard scattering models. An approximate expression is derived for the mean bias towards the trigger of each of the two participating partons and it is found that event by event one of the partons is biased more than the other, even with a 90 0 trigger. The transverse momentum of partons and their closely related off mass shell behaviour are treated as a perturbation in the equation for the single particle inclusive cross-section, which is then expanded in a Taylor series. The first non-zero correction term is calculated and it is found that to this order, the cross-section is increased by parton transverse momentum effects by typically a factor of 2 for psub(T) = 2 to 3 GeV/c, and that the correction decreases rapidly with increasing psub(T). (author)
Interpretation of the cosmic-ray air shower signal in Askaryan radio detectors
de Vries, Krijn D.; Buitink, Stijn; van Eijndhoven, Nick; Meures, Thomas; O'Murchadha, Aongus; Scholten, Olaf
2017-01-01
We discuss the radio emission from a cosmic-ray air shower propagating in air before it hits an air-ice boundary after which it completes its propagation inside the ice. The in-air emission, the in-ice emission, as well as the transition radiation from the shower crossing the boundary is considered.
Probing Atmospheric Electric Fields through Radio Emission from Cosmic-Ray-Induced Air Showers
Scholten, Olaf; Trinh, Gia; Buitink, Stijn; Corstanje, Arthur; Ebert, Ute; Enriquez, Emilio; Falcke, Heino; Hoerandel, Joerg; Nelles, Anna; Schellart, Pim; Rachen, Joerg; Rutjes, Casper; ter Veen, Sander; Rossetto, Laura; Thoudam, Satyendra
2016-01-01
Energetic cosmic rays impinging on the atmosphere create a particle avalanche called an extensive air shower. In the leading plasma of this shower electric currents are induced that generate coherent radio wave emission that has been detected with LOFAR, a large and dense array of simple radio
An in-premise model for Legionella exposure during showering events
An exposure model was constructed to predict the critical Legionella densities in an engineered water system that might result in infection from inhalation of aerosols containing the pathogen while showering. The model predicted the Legionella densities in the shower air, water ...
Monte-Carlo simulation of hadronic showers. Part 1: Comparison with experiment
International Nuclear Information System (INIS)
Amatuni, Ts.A.; Mamidjanyan, E.A.; Sanossyan, Kh.N.
1992-01-01
Hadronic showers are simulated by the MARS 10 code and compared with various experimental results obtained at high-energy accelerators. Good agreement between the experiment and the simulations is observed. MARS 10 is a fast and reliable instrument for numerical studies of the average characteristics of hadronic showers. 16 refs
The Effect of Cold Showering on Health and Work: A Randomized Controlled Trial
Buijze, Geert A.; Sierevelt, Inger N.; van der Heijden, Bas C. J. M.; Dijkgraaf, Marcel G.; Frings-Dresen, Monique H. W.
2016-01-01
The aim of this study was to determine the cumulative effect of a routine (hot-to-) cold shower on sickness, quality of life and work productivity. Between January and March 2015, 3018 participants between 18 and 65 years without severe comorbidity and no routine experience of cold showering were
Scholten, O.; Trinh, T. N. G.; Bonardi, A.; Buitink, S.; Correa, P.; Corstanje, A.; Hasankiadeh, Q. Dorosti; Falcke, H.; Horandel, J. R.; Mitra, P.; Mulrey, K.; Nelles, A.; Rachen, J. P.; Rossetto, L.; Schellart, P.; Thoudam, S.; ter Veen, S.; de Vries, K. D.; Winchen, T.
2016-01-01
We report here on a novel analysis of the complete set of four Stokes parameters that uniquely determine the linear and/or circular polarization of the radio signal for an extensive air shower. The observed dependency of the circular polarization on azimuth angle and distance to the shower axis is a
Determining Thunderstorm Electric Fields using Radio Emission from Cosmic-Ray Air Showers
Hare, B.; Scholten, O.; Trinh, G. T. N.; Ebert, U.; Rutjes, C.
2017-01-01
We report on a novel non-intrusive way to investigate electric fields in thunderclouds.Energetic cosmic rays penetrating the atmosphere create a particle avalanche called an extensive air shower. The front of the shower is a plasma cloud that contains 10^6 or more free electrons and positrons moving
A liquid argon ionisation calorimeter for detection of electromagnetic and hadronic showers
International Nuclear Information System (INIS)
Hofmann, W.
1975-02-01
The performance of a liquid argon ionization chamber, consisting of a set of eighty 2 mm thick iron plates, is described. Measurements with muons, and electron and proton showers were performed; from these measurements a ratio of 1.2 for the electron to proton response was derived. For hadron showers a good detection efficiency of nuclear spallation products could be established. (orig.) [de