DESY: QCD workshop

International Nuclear Information System (INIS)

Ingelman, Gunnar

1994-01-01

The traditional annual DESY Theory Workshop highlights a topical theory sector. The most recent was under the motto 'Quantum Chromo-Dynamics' - QCD, the field theory of quarks and gluons. The organizers had arranged a programme covering most aspects of current QCD research. This time the workshop was followed by a topical meeting on 'QCD at HERA' to look at the electron-proton scattering experiments now in operation at DESY's new HERA collider

Phases of QCD

International Nuclear Information System (INIS)

Roessner, Simon

2009-01-01

Quantum Chromodynamics (QCD) is the theory of the strong interaction within the Standard Model of elementary particles. Today's research in this area dedicates substantial resources to numeric solutions of the QCD field equations and experimental programs exploring the phases of QCD. This thesis proceeds along a complementary line - that of modelling QCD, with the aim of identifying its dominant degrees of freedom. This is possible by minimally coupling effective potentials for the Polyakov loop to Nambu-Jona-Lasinio models using temporal background fields to model chiral symmetry breaking respecting colour confinement. The fermion sign problem resulting from the minimal coupling is addressed in this work establishing a novel, systematically ordered approach. The modifications to the approximative order parameter of colour confinement, the Polyakov loop, are in direct connection with the fermion sign problem. Furthermore an effective coupling of quark densities of different flavours is induced. This mechanism, most likely also present in QCD, produces finite contributions to flavour off diagonal susceptibilities. Susceptibilities are amongst the most promising physical quantities for the experimental exploration of the phase transition at high temperatures and densities. (orig.)

QCD phenomenology

International Nuclear Information System (INIS)

Gaillard, M.K.

1979-01-01

Selected topics in QCD phenomenology are reviewed: the development of an effective jet perturbation series with applications to factorization, energy flow analysis and photon physics; implications of non-perturbative phenomena for hard scattering processes and the pseudoscalar mass spectrum; resonance properties as extracted from the combined technologies of perturbative and non-perturbative QCD. (orig.)

Standard model group, QCD subgroup - dynamics isolating and testing the elementary QCD subprocess

International Nuclear Information System (INIS)

Tannenbaum, M.J.

1982-01-01

QCD to an experimentalist is the theory of interactions of quarks and gluons. Experimentalists like QCD because QCD is analogous to QED. Thus, following Drell and others who have for many years studied the validity of QED, one has a ready-made menu for tests of QCD. There are the static and long distance tests. These topics are covered by Peter LePage in the static properties group. In this report, dynamic and short distance tests of QCD will be discussed, primarily via reactions with large transverse momenta. This report is an introduction and overview of the subject, to serve as a framework for other reports from the subgroup. In the last two sections, the author has taken the opportunity to discuss his own ideas and opinions

Semihard QCD

International Nuclear Information System (INIS)

Kwiecinski, J.

1989-01-01

Recent results concerning the small x limit of parton distributions in perturbative QCD are reviewed. This includes in particular discussion of the bare Pomeron in perturbative QCD and of shadowing corrections. The minijet production processes and possible manifestation of semihard interactions in high energy pp-bar elastic scattering are also discussed. 46 refs., 8 figs. (author)

Valence QCD: Connecting QCD to the quark model

International Nuclear Information System (INIS)

Liu, K.F.; Dong, S.J.; Draper, T.; Sloan, J.; Leinweber, D.; Woloshyn, R.M.

1999-01-01

A valence QCD theory is developed to study the valence quark properties of hadrons. To keep only the valence degrees of freedom, the pair creation through the Z graphs is deleted in the connected insertions, whereas the sea quarks are eliminated in the disconnected insertions. This is achieved with a new 'valence QCD' Lagrangian where the action in the time direction is modified so that the particle and antiparticle decouple. It is shown in this valence version of QCD that the ratios of isovector to isoscalar matrix elements (e.g., F A /D A and F S /D S ratios) in the nucleon reproduce the SU(6) quark model predictions in a lattice QCD calculation. We also consider how the hadron masses are affected on the lattice and discover new insights into the origin of dynamical mass generation. It is found that, within statistical errors, the nucleon and the Δ become degenerate for the quark masses we have studied (ranging from 1 to 4 times the strange mass). The π and ρ become nearly degenerate in this range. It is shown that valence QCD has the C, P, T symmetries. The lattice version is reflection positive. It also has the vector and axial symmetries. The latter leads to a modified partially conserved axial Ward identity. As a result, the theory has a U(2N F ) symmetry in the particle-antiparticle space. Through lattice simulation, it appears that this is dynamically broken down to U q (N F )xU bar q (N F ). Furthermore, the lattice simulation reveals spin degeneracy in the hadron masses and various matrix elements. This leads to an approximate U q (2N F )xU bar q (2N F ) symmetry which is the basis for the valence quark model. In addition, we find that the masses of N, Δ,ρ,π,a 1 , and a 0 all drop precipitously compared to their counterparts in the quenched QCD calculation. This is interpreted as due to the disappearance of the 'constituent' quark mass which is dynamically generated through tadpole diagrams. The origin of the hyperfine splitting in the baryon is

Phases of QCD

Energy Technology Data Exchange (ETDEWEB)

Roessner, Simon

2009-04-09

Quantum Chromodynamics (QCD) is the theory of the strong interaction within the Standard Model of elementary particles. Today's research in this area dedicates substantial resources to numeric solutions of the QCD field equations and experimental programs exploring the phases of QCD. This thesis proceeds along a complementary line - that of modelling QCD, with the aim of identifying its dominant degrees of freedom. This is possible by minimally coupling effective potentials for the Polyakov loop to Nambu-Jona-Lasinio models using temporal background fields to model chiral symmetry breaking respecting colour confinement. The fermion sign problem resulting from the minimal coupling is addressed in this work establishing a novel, systematically ordered approach. The modifications to the approximative order parameter of colour confinement, the Polyakov loop, are in direct connection with the fermion sign problem. Furthermore an effective coupling of quark densities of different flavours is induced. This mechanism, most likely also present in QCD, produces finite contributions to flavour off diagonal susceptibilities. Susceptibilities are amongst the most promising physical quantities for the experimental exploration of the phase transition at high temperatures and densities. (orig.)

Resonances in QCD

Energy Technology Data Exchange (ETDEWEB)

Lutz, Matthias F. M.; Lange, Jens Sören; Pennington, Michael; Bettoni, Diego; Brambilla, Nora; Crede, Volker; Eidelman, Simon; Gillitzer, Albrecht; Gradl, Wolfgang; Lang, Christian B.; Metag, Volker; Nakano, Takashi; Nieves, Juan; Neubert, Sebastian; Oka, Makoto; Olsen, Stephen L.; Pappagallo, Marco; Paul, Stephan; Pelizäus, Marc; Pilloni, Alessandro; Prencipe, Elisabetta; Ritman, Jim; Ryan, Sinead; Thoma, Ulrike; Uwer, Ulrich; Weise, Wolfram

2016-04-01

We report on the EMMI Rapid Reaction Task Force meeting 'Resonances in QCD', which took place at GSI October 12-14, 2015 (Fig.~1). A group of 26 people met to discuss the physics of resonances in QCD. The aim of the meeting was defined by the following three key questions; what is needed to understand the physics of resonances in QCD?; where does QCD lead us to expect resonances with exotic quantum numbers?; and what experimental efforts are required to arrive at a coherent picture? For light mesons and baryons only those with up, down and strange quark content were considered. For heavy-light and heavy-heavy meson systems, those with charm quarks were the focus.This document summarizes the discussions by the participants, which in turn led to the coherent conclusions we present here.

Predictive Lattice QCD

International Nuclear Information System (INIS)

Kronfeld, Andreas

2005-01-01

Quantum chromodynamics (QCD) is the quantum field theory describing the strong interactions of quarks bound inside hadrons. It is marvelous theory, which works (mathematically) at all distance scales. Indeed, for thirty years, theorists have known how to calculate short-distance properties of QCD, thanks to the (Nobel-worthy) idea of asymptotic freedom. More recently, numerical techniques applied to the strong-coupling regime of QCD have enabled us to compute long-distance bound-state properties. In this colloquium, we review these achievements and show how the new-found methods of calculation will influence high-energy physics.

Excited QCD 2017

CERN Document Server

2017-01-01

This edition is the ninth in a series of workshops that had been previously organised in Poland (2009), Slovakia (2010 and 2015), France (2011), Portugal (2012 and 2016) and Bosnia and Herzegovina (2013 and 2014). In the year 2017 the workshop goes to the beautiful Sintra near Lisbon, Portugal. The workshop covers diverse aspects of QCD: (i) QCD at low energies: excited hadrons, new resonances, glueballs, multiquarks. (ii) QCD at high temperatures and large densities: heavy-ion collisions, jets, diffraction, hadronisation, quark-gluon plasma, holography, colour-glass condensate, compact stars, applications to astrophysics.

Lattice QCD

International Nuclear Information System (INIS)

Hasenfratz, P.

1983-01-01

The author presents a general introduction to lattice gauge theories and discusses non-perturbative methods in the gauge sector. He then shows how the lattice works in obtaining the string tension in SU(2). Lattice QCD at finite physical temperature is discussed. Universality tests in SU(2) lattice QCD are presented. SU(3) pure gauge theory is briefly dealt with. Finally, fermions on the lattice are considered. (Auth.)

Academic Training Lectures - QCD for Postgraduates

CERN Multimedia

Maureen Prola-Tessaur

2010-01-01

by Giulia Zanderighi (University of Oxford) Monday 12 to Friday 16 April 2010 From 11:00 to 12:00 - Main Auditorium, Bldg. 500-1-001 Monday 12 - Modern QCD - Lecture 1 Starting from the QCD Lagrangian we will revisit some basic QCD concepts and derive fundamental properties like gauge invariance and isospin symmetry and will discuss the Feynman rules of the theory. We will then focus on the gauge group of QCD and derive the Casimirs CF and CA and some useful color identities. Tuesday 13 - Modern QCD - Lecture 2 We will start discussing the matter content of the theory and revisit the experimental measurements that led to the discovery of quarks. We will then consider a classic QCD observable, the R-ratio, and use it to illustrate the appearance of UV divergences and the need to renormalize the coupling constant of QCD. We will then discuss asymptotic freedom and confinement. Finally, we will examine a case where soft and collinear infrared divergences appear, will discuss the soft approximation in QCD ...

Novel QCD Phenomena

International Nuclear Information System (INIS)

Brodsky, Stanley J.; SLAC

2007-01-01

I discuss a number of novel topics in QCD, including the use of the AdS/CFT correspondence between Anti-de Sitter space and conformal gauge theories to obtain an analytically tractable approximation to QCD in the regime where the QCD coupling is large and constant. In particular, there is an exact correspondence between the fifth-dimension coordinate z of AdS space and a specific impact variable ζ which measures the separation of the quark constituents within the hadron in ordinary space-time. This connection allows one to compute the analytic form of the frame-independent light-front wavefunctions of mesons and baryons, the fundamental entities which encode hadron properties and allow the computation of exclusive scattering amplitudes. I also discuss a number of novel phenomenological features of QCD. Initial- and final-state interactions from gluon-exchange, normally neglected in the parton model, have a profound effect in QCD hard-scattering reactions, leading to leading-twist single-spin asymmetries, diffractive deep inelastic scattering, diffractive hard hadronic reactions, the breakdown of the Lam Tung relation in Drell-Yan reactions, and nuclear shadowing and non-universal antishadowing--leading-twist physics not incorporated in the light-front wavefunctions of the target computed in isolation. I also discuss tests of hidden color in nuclear wavefunctions, the use of diffraction to materialize the Fock states of a hadronic projectile and test QCD color transparency, and anomalous heavy quark effects. The presence of direct higher-twist processes where a proton is produced in the hard subprocess can explain the large proton-to-pion ratio seen in high centrality heavy ion collisions

QCD as a Theory of Hadrons

Science.gov (United States)

Narison, Stephan

2007-07-01

About Stephan Narison; Outline of the book; Preface; Acknowledgements; Part I. General Introduction: 1. A short flash on particle physics; 2. The pre-QCD era; 3. The QCD story; 4. Field theory ingredients; Part II. QCD Gauge Theory: 5. Lagrangian and gauge invariance; 6. Quantization using path integral; 7. QCD and its global invariance; Part III. MS scheme for QCD and QED: Introduction; 8. Dimensional regularization; 9. The MS renormalization scheme; 10. Renormalization of operators using the background field method; 11. The renormalization group; 12. Other renormalization schemes; 13. MS scheme for QED; 14. High-precision low-energy QED tests; Part IV. Deep Inelastic Scattering at Hadron Colliders: 15. OPE for deep inelastic scattering; 16. Unpolarized lepton-hadron scattering; 17. The Altarelli-Parisi equation; 18. More on unpolarized deep inelastic scatterings; 19. Polarized deep-inelastic processes; 20. Drell-Yan process; 21. One 'prompt photon' inclusive production; Part V. Hard Processes in e+e- Collisions: Introduction; 22. One hadron inclusive production; 23. gg scatterings and the 'spin' of the photon; 24. QCD jets; 25. Total inclusive hadron productions; Part VI. Summary of QCD Tests and as Measurements; Part VII. Power Corrections in QCD: 26. Introduction; 27. The SVZ expansion; 28. Technologies for evaluating Wilson coefficients; 29. Renormalons; 30. Beyond the SVZ expansion; Part VIII. QCD Two-Point Functions: 31. References guide to original works; 32. (Pseudo)scalar correlators; 33. (Axial-)vector two-point functions; 34. Tensor-quark correlator; 35. Baryonic correlators; 36. Four-quark correlators; 37. Gluonia correlators; 38. Hybrid correlators; 39. Correlators in x-space; Part IX. QCD Non-Perturbative Methods: 40. Introduction; 41. Lattice gauge theory; 42. Chiral perturbation theory; 43. Models of the QCD effective action; 44. Heavy quark effective theory; 45. Potential approaches to quarkonia; 46. On monopole and confinement; Part X. QCD

Renormalization of Extended QCD2

International Nuclear Information System (INIS)

Fukaya, Hidenori; Yamamura, Ryo

2015-01-01

Extended QCD (XQCD), proposed by Kaplan [D. B. Kaplan, arXiv:1306.5818], is an interesting reformulation of QCD with additional bosonic auxiliary fields. While its partition function is kept exactly the same as that of original QCD, XQCD naturally contains properties of low-energy hadronic models. We analyze the renormalization group flow of 2D (X)QCD, which is solvable in the limit of a large number of colors N c , to understand what kind of roles the auxiliary degrees of freedom play and how the hadronic picture emerges in the low-energy region

Experimental application of QCD antennas

Energy Technology Data Exchange (ETDEWEB)

Bobrovskyi, Sergei

2010-02-15

A serious problem in searches for new physics at the LHC is the rejection of QCD induced multijet events. In this thesis the formalism of QCD antenna variables based on the SPHEL approximation of QCD matrix elements is applied for the rst time on experimentally reconstructed jets in order to discriminate QCD from supersymmetric processes. The new observables provide additional information with respect to traditional event shape variables. Albeit correlated with experimentally measured missing transverse energy, the variables can be used to improve the signal to background ratio. (orig.)

Experimental application of QCD antennas

International Nuclear Information System (INIS)

Bobrovskyi, Sergei

2010-02-01

A serious problem in searches for new physics at the LHC is the rejection of QCD induced multijet events. In this thesis the formalism of QCD antenna variables based on the SPHEL approximation of QCD matrix elements is applied for the rst time on experimentally reconstructed jets in order to discriminate QCD from supersymmetric processes. The new observables provide additional information with respect to traditional event shape variables. Albeit correlated with experimentally measured missing transverse energy, the variables can be used to improve the signal to background ratio. (orig.)

Hadron structure from lattice QCD

International Nuclear Information System (INIS)

Schaefer, Andreas

2008-01-01

Some elements and current developments of lattice QCD are reviewed, with special emphasis on hadron structure observables. In principle, high precision experimental and lattice data provide nowadays a very detailled picture of the internal structure of hadrons. However, to relate both, a very good controle of perturbative QCD is needed in many cases. Finally chiral perturbation theory is extremely helpful to boost the precision of lattice calculations. The mutual need and benefit of all four elements: experiment, lattice QCD, perturbative QCD and chiral perturbation theory is the main topic of this review

Recent QCD results from ATLAS

CERN Document Server

Meyer, C; The ATLAS collaboration

2014-01-01

The ATLAS collaboration has performed studies of a wide range of QCD phenomena, from soft particle to hard photon and jet production. Recent soft-QCD measurements include studies of underlying event and vector meson production. Differential measurements of inclusive and dijet production provide stringent tests of high-order QCD predictions and provide input for determination of parton density functions. Measurements of isolated inclusive and di-photons cross sections for high transverse momentum photons test theoretical predictions of perturbative QCD and constrain parton density functions. An overview of these results is given.

QCD and nuclei

International Nuclear Information System (INIS)

Simonov, Yu.A.

1989-01-01

To apply QCD to nuclear physics one needs methods of long-distance QCD. A new method, method of Confining Background Fields, CBF, which incorporates confinement, is presented with applications to heavy and light quarks, both in mesons and baryons. Spin-dependent forces are calculated for light and heavy quarks. The quark potential model in some limiting case is derived. 25 refs

QCD: Renormalization for the practitioner

International Nuclear Information System (INIS)

Pascual, P.; Tarrach, R.

1984-01-01

These notes correspond to a GIFT (Grupo Interuniversitario de Fisica Teorica) course which was given by us in autumn 1983 at the University of Barcelona. Their main subject is renormalization in perturbative QCD and only the last chapter goes beyond perturbation theory. They are essentially self contained and their aim is to teach the student the techniques of perturbative QCD and the QCD sum rules. (orig./HSI)

Towards the chiral limit in QCD

International Nuclear Information System (INIS)

Shailesh Chandrasekharan

2006-01-01

Computing hadronic observables by solving QCD from first principles with realistic quark masses is an important challenge in fundamental nuclear and particle physics research. Although lattice QCD provides a rigorous framework for such calculations many difficulties arise. Firstly, there are no good algorithms to solve lattice QCD with realistically light quark masses. Secondly, due to critical slowing down, Monte Carlo algorithms are able to access only small lattice sizes on coarse lattices. Finally, due to sign problems it is almost impossible to study the physics of finite baryon density. Lattice QCD contains roughly three mass scales: the cutoff (or inverse lattice spacing) a -1 , the confinement scale Λ QCD , and the pion mass m π . Most conventional Monte Carlo algorithms for QCD become inefficient in two regimes: when Λ QCD becomes small compared to a -1 and when m π becomes small compared to Λ QCD . The former can be largely controlled by perturbation theory thanks to asymptotic freedom. The latter is more difficult since chiral extrapolations are typically non-analytic and can be unreliable if the calculations are not done at sufficiently small quark masses. For this reason it has been difficult to compute quantities close to the chiral limit. The essential goal behind this proposal was to develop a new approach towards understanding QCD and QCD-like theories with sufficiently light quarks. The proposal was based on a novel cluster algorithm discovered in the strong coupling limit with staggered fermions [1]. This algorithm allowed us to explore the physics of exactly massless quarks and as well as light quarks. Thus, the hope was that this discovery would lead to the complete solution of at least a few strongly coupled QCD-like theories. The solution would be far better than those achievable through conventional methods and thus would be able to shed light on the chiral physics from a new direction. By the end of the funding period, the project led

Components of QCD

International Nuclear Information System (INIS)

Sivers, D.

1979-10-01

Some aspects of a simple strategy for testing the validity of QCD perturbation theory are examined. The importance of explicit evaluation of higher-order contributions is illustrated by considering Z 0 decays. The recent progress toward understanding exclusive processes in QCD is discussed and some simple examples are given of how to isolate and test the separate components of the perturbation expansion in a hypothetical series of jet experiments

Quantum chromodynamics (QCD) and collider physics

International Nuclear Information System (INIS)

Ellis, R.K.; Stirling, W.J.

1990-01-01

This report discusses: fundamentals of perturbative QCD; QCD in e + e - → hadrons; deep inelastic scattering and parton distributions; the QCD parton model in hadron-hadron collisions; large p T jet production in hadron-hadron collisions; the production of vector bosons in hadronic collisions; and the production of heavy quarks

Nucleon-nucleon interactions via Lattice QCD: Methodology. HAL QCD approach to extract hadronic interactions in lattice QCD

Science.gov (United States)

Aoki, Sinya

2013-07-01

We review the potential method in lattice QCD, which has recently been proposed to extract nucleon-nucleon interactions via numerical simulations. We focus on the methodology of this approach by emphasizing the strategy of the potential method, the theoretical foundation behind it, and special numerical techniques. We compare the potential method with the standard finite volume method in lattice QCD, in order to make pros and cons of the approach clear. We also present several numerical results for nucleon-nucleon potentials.

Parameters for characterisation of the ecochemical soil status and the potential hazards of acidification and nitrogen saturation in level II forest sites; Kennwerte zur Charakterisierung des oekochemischen Bodenzustandes und des Gefaehrdungspotentials durch Bodenversauerung und Stickstoffsaettigung an Level II-Waldoekosystem-Dauerbeobachtungsflaechen

Energy Technology Data Exchange (ETDEWEB)

NONE

2000-07-01

The ad hoc working group on soil acidification and nitrogen saturation of the Federal Government/Laender Working Group level II primarily aimed at drafting a manual for the interpretation of soil data (soil solid phase, soil solution) acquired on Level II plots. The manual contains parameters and proposals for evaluating the acid/base-status of forest soils, the nutrient supply and nitrogen status as well as for assessing the risks caused by aluminium, acid and heavy metal stress. Further parameters and proposals for evaluation concern the risks for spring and ground water quality through acidification and elevated nitrate concentrations. All parameters are described in detail, their informative value is discussed and examples are given for their use. A distinction is made between indicators to show the current ecochemical situation and to describe future risks, e.g. through progressive soil acidification, nutrient depletion and increasing nitrogen saturation. The manual thus fits in right with the overall objectives of the Level II Programme to reveal cause-effect relations in the forest damage situation and to give advice on timely counteraction via forecasts of the future development. (orig.) [German] Das vorrangige Ziel des Arbeitskreises 'Bodenversauerung und Stickstoffsaettigung' der Bundes-Laender-Arbeitsgruppe Level II war die Erarbeitung eines Auswerteleitfadens fuer die Bodendaten (Bodenfestphase, Sickerwasser) der Level II-Flaechen. Der Leitfaden enthaelt Kennwerte und Bewertungsvorschlaege zum Saeure-Base-Zustand des Waldbodens, zur Naehrstoffbereitstellung, zum Stickstoffstatus, zur Abschaetzung von Risiken durch Aluminium-, Saeure- und Schwermetallstress und zur Gefaehrdung des Quell- und Grundwassers durch Versauerung und steigende Nitratgehalte. Alle Kennwerte werden eingehend beschrieben, ihre Aussagekraft diskutiert und ihre Anwendung an Beispielen dargestellt. Unterschieden wird zwischen Indikatoren zur Darstellung der aktuellen

Method of analytic continuation by duality in QCD: Beyond QCD sum rules

International Nuclear Information System (INIS)

Kremer, M.; Nasrallah, N.F.; Papadopoulos, N.A.; Schilcher, K.

1986-01-01

We present the method of analytic continuation by duality which allows the approximate continuation of QCD amplitudes to small values of the momentum variables where direct perturbative calculations are not possible. This allows a substantial extension of the domain of applications of hadronic QCD phenomenology. The method is illustrated by a simple example which shows its essential features

Theoretical summary talk of QCD 2002

International Nuclear Information System (INIS)

Basu, Rahul

2003-01-01

This is a summary of the talks on QCD, not including QCD at finite temperature or density (which are discussed elsewhere) presented at the QCD 2002 meeting held at IIT, Kanpur. I have attempted to give only an overview of the talks since the details may be found in the individual contributions. (author)

The HC potential of pre-Westphalian sediments in the North German basin. A synthesis; Das Kohlenwasserstoff-Potential des Praewestfals im norddeutschen Becken. Eine Synthese

Energy Technology Data Exchange (ETDEWEB)

Gerling, P.; Kockel, F.; Krull, P. [Bundesanstalt fuer Geowissenschaften und Rohstoffe, Berlin (Germany).]|[Bundesanstalt fuer Geowissenschaften und Rohstoffe, Hannover (Germany)

1999-07-01

It was the aim of the interdisciplinary and interinstitutional research program to investigate the possibilities of HC generation from pre-Westphalian sediments in the North German basin in space and time. Potential source rock horizons exist within all pre-Westphalian structural units in Northern Europe, ranging from Cambrian to the Namurian in age and deposited in different environments. The structural framework of the basement of the North German Permian basin was described, the position of the Variscan outer front newly defined and the maturation history during the Late Palaeozoic, Mesozoic and Cainozoic deciphered. Pyrolysis experiments have shown that HC generation, especially from type III kerogen, is possible even beyond a maturity of 4% Rmax. Detailed geochemical and isotope-geochemical investigations of the natural gases from all North German fields indicate gas contributions from pre-Westphalian sources in special regions (Ems Estuary region, Altmark). By integrating all the results of the study an estimation of the possibilities of pre-Westphalian gas occurrences in Northern Germany could be made and the most promising areas for prospecting have been outlined. (orig.) [Deutsch] Aufgabe des interdisziplinaeren und interinstitutionellen Forschungsvorhabens war es, die Moeglichkeiten der Kohlenwasserstoff-Bildung aus praewestfalen Sedimenten im Norddeutschen Becken in Raum und Zeit zu erkunden. In allen praewestfalen strukturellen Grosseinheiten Nordeuropas existieren potentielle Muttergesteinshorizonte kambrischen bis namurischen Alters aus unterschiedlichen Ablagerungsmilieus. Das strukturelle Inventar des Untergrundes des norddeutschen Permbeckens, der Verlauf der Variszidenfront in Norddeutschland und die Reifungsgeschichte der praewestfalen Muttergesteine im Verlauf der jungpalaeozoischen, mesozoischen und tertiaeren Entwicklung wurden entschluesselt. Pyrolyseversuche zeigten, dass eine KW-Genese, vor allem fuer Kerogen des Typs III, auch jenseits

Weak-interacting holographic QCD

International Nuclear Information System (INIS)

Gazit, D.; Yee, H.-U.

2008-06-01

We propose a simple prescription for including low-energy weak-interactions into the frame- work of holographic QCD, based on the standard AdS/CFT dictionary of double-trace deformations. As our proposal enables us to calculate various electro-weak observables involving strongly coupled QCD, it opens a new perspective on phenomenological applications of holographic QCD. We illustrate efficiency and usefulness of our method by performing a few exemplar calculations; neutron beta decay, charged pion weak decay, and meson-nucleon parity non-conserving (PNC) couplings. The idea is general enough to be implemented in both Sakai-Sugimoto as well as Hard/Soft Wall models. (author)

Resonances in QCD

Energy Technology Data Exchange (ETDEWEB)

Lutz, Matthias F.M., E-mail: m.lutz@gsi.de [GSI Helmholtzzentrum für Schwerionenforschung GmbH, D-64291 Darmstadt (Germany); Technische Universität Darmstadt, D-64289 Darmstadt (Germany); Lange, Jens Sören, E-mail: Soeren.Lange@exp2.physik.uni-giessen.de [II. Physikalisches Institut, Justus-Liebig-Universität Giessen, D-35392 Giessen (Germany); Pennington, Michael, E-mail: michaelp@jlab.org [Thomas Jefferson National Accelerator Facility, Newport News, VA 23606 (United States); Bettoni, Diego [Istituto Nazionale di Fisica Nucleare, Sezione di Ferrara, 44122 Ferrara (Italy); Brambilla, Nora [Physik Department, Technische Universität München, D-85747 Garching (Germany); Crede, Volker [Department of Physics, Florida State University, Tallahassee, FL 32306 (United States); Eidelman, Simon [Novosibirsk State University, Novosibirsk 630090 (Russian Federation); Budker Istitute of Nuclear Physics SB RAS, Novosibirsk 630090 (Russian Federation); Gillitzer, Albrecht [Institut für Kernphysik, Forschungszentrum Jülich GmbH, D-52425 Jülich (Germany); Gradl, Wolfgang [Institut für Kernphysik, Johannes Gutenberg-Universität Mainz, D-55128 Mainz (Germany); Lang, Christian B. [Institut für Physik, Universität Graz, A-8010 Graz (Austria); Metag, Volker [II. Physikalisches Institut, Justus-Liebig-Universität Giessen, D-35392 Giessen (Germany); Nakano, Takashi [Research Center for Nuclear Physics, Osaka University, Osaka 567-0047 (Japan); and others

2016-04-15

We report on the EMMI Rapid Reaction Task Force meeting ‘Resonances in QCD’, which took place at GSI October 12–14, 2015. A group of 26 people met to discuss the physics of resonances in QCD. The aim of the meeting was defined by the following three key questions: • What is needed to understand the physics of resonances in QCD? • Where does QCD lead us to expect resonances with exotic quantum numbers? • What experimental efforts are required to arrive at a coherent picture? For light mesons and baryons only those with up, down and strange quark content were considered. For heavy–light and heavy–heavy meson systems, those with charm quarks were the focus. This document summarizes the discussions by the participants, which in turn led to the coherent conclusions we present here.

Dual QCD and phase transition in early universe

International Nuclear Information System (INIS)

Ranjan, Akhilesh; Raina, P.K.; Nandan, Hemwati

2009-01-01

The quantum chromodynamics (QCD) vacuum with condensed monopoles/ dyons (i.e., a dual Ginzburg- Landau (DGL) type model of QCD or dual QCD) has been quite successful to describe the large-distance behavior of QCD vacuum. Further, such DGL theory of QCD at finite temperature is also found to be useful in studying the phase transition process as believed to occur in early universe. In the present article, we have used the DGL theory of QCD with dyons to study the hadronisation in early universe. The effective potential at finite temperature is calculated. The notions of the phase transition in the background of the dyonically condensed QCD vacuum has been investigated by calculating the critical temperature in view of the temperature dependent couplings

Extension of the HAL QCD approach to inelastic and multi-particle scatterings in lattice QCD

Science.gov (United States)

Aoki, S.

We extend the HAL QCD approach, with which potentials between two hadrons can be obtained in QCD at energy below inelastic thresholds, to inelastic and multi-particle scatterings. We first derive asymptotic behaviors of the Nambu-Bethe-Salpeter (NBS) wave function at large space separations for systems with more than 2 particles, in terms of the one-shell $T$-matrix consrainted by the unitarity of quantum field theories. We show that its asymptotic behavior contains phase shifts and mixing angles of $n$ particle scatterings. This property is one of the essential ingredients of the HAL QCD scheme to define "potential" from the NBS wave function in quantum field theories such as QCD. We next construct energy independent but non-local potentials above inelastic thresholds, in terms of these NBS wave functions. We demonstrate an existence of energy-independent coupled channel potentials with a non-relativistic approximation, where momenta of all particles are small compared with their own masses. Combining these two results, we can employ the HAL QCD approach also to investigate inelastic and multi-particle scatterings.

QCD machines - present and future

International Nuclear Information System (INIS)

Christ, N.H.

1991-01-01

The present status of the currently working and nearly working dedicated QCD machines is reviewed and proposals for future machines are discussed with particular emphasis on the QCD Teraflop Project in the US. (orig.)

Investigation of the feasibility of the solar-/geothermally-assisted heat supply system Gesotherm S; Untersuchung der Durchfuehrbarkeit des solar-/ geothermisch gestuetzten Waermeversorgungssystems Gesotherm S

Energy Technology Data Exchange (ETDEWEB)

Liebisch, H. [EKT Energie und Kommunal-Technologie GmbH, Berlin (Germany)

1998-12-31

The project has been running since 1st March 1998 and is supposed to investigate the technical feasibility and economic efficiency of the Gesotherm S heat supply system in the residential area Berlin-Biesdorf/Habichtshorst (1,000 flats). Main points of investigation are: proof of feasibility and geothermal analysis of the deep pit; analysis of storage possibilities and technical synergies of combined solar-geothermal operation; determination of the regenerative supply ratio; calculation of economic efficiency; estimation of cost-saving potentials. The whole system is simulated for these studies. A new simulation model was developed for the pit. Simulations are based on the SMILE-simulation environment developed by the Technical University of Berlin. First estimates indicate costs of DM 200 per MWh without subsidies. (orig.) [Deutsch] Mit dem seit 1. Maerz 1998 laufenden Vorhaben soll die technische Realisierbarkeit und wirtschaftliche Attraktivitaet des Waermeversorgungssystems Gesotherm S am Beispiel der Nahwaermeversorgung eines Wohngebietes (ca. 1.000 WE) in Berlin-Biesdorf/Habichtshorst umfassend untersucht werden. Schwerpunkte der Untersuchung: - Machbarkeitsnachweis und geothermische Analyse der Tiefensonde - Analyse der Speichermoeglichkeiten und der technischen Synergieeffekte des solar-/geothermischen Kombinationsbetriebes - Ermittlung der regenerativen Deckungsrate - Berechnung der Wirtschaftlichkeit - Abschaetzung der Kostensenkungspotentiale. Fuer die Untersuchung wird das Gesamtsystem simuliert. Speziell fuer die Tiefensonde wird ein neues Simulationsmodell entwickelt. Basis ist die, an der TU-Berlin entwickelte, Simulationsumgebung SMILE. Erste Abschaetzungen ergaben Waermekosten ohne Subventionen von unter 200 DM/MWh. (orig.)

QCD

CERN Document Server

Catani, S; Soper, Davison Eugene; Stirling, William James; Tapprogge, Stefan; Alekhin, S I; Aurenche, Patrick; Balázs, C; Ball, R D; Battistoni, G; Berger, E L; Binoth, T; Brock, R L; Casey, D; Corcella, Gennaro; Del Duca, V; Fabbro, A D; de Roeck, A; Ewerz, C; de Florian, D; Fontannaz, M; Frixione, Stefano; Giele, W T; Grazzini, Massimiliano; Guillet, J P; Marlen-Heinrich, G; Huston, J; Kalk, J; Kataev, A L; Kato, K; Keller, S; Klasen, M; Kosower, D A; Kulesza, A; Kunszt, Zoltán; Kupco, A; Ilyin, V A; Magnea, L; Mangano, Michelangelo L; Martin, A D; Mazumdar, K; Miné, P; Moretti, M; van Neerven, W L; Parente, G; Perret-Gallix, D; Pilon, E; Pukhov, A E; Puljak, I; Pumplin, Jon; Richter-Was, Elzbieta; Roberts, R G; Salam, Gavin P; Seymour, Michael H; Skachkov, N B; Sidorov, A V; Stenzel, H; Stump, D R; Thorne, R S; Treleani, D; Tung, W K; Vogt, A; Webber, Bryan R; Werlen, M; Zmouchko, S; Mine, Ph.

2000-01-01

We discuss issues of QCD at the LHC including parton distributions, Monte Carlo event generators, the available next-to-leading order calculations, resummation, photon production, small x physics, double parton scattering, and backgrounds to Higgs production.

Meson Spectroscopy from QCD - Project Results

Energy Technology Data Exchange (ETDEWEB)

Dudek, Jozef [Old Dominion Univ., Norfolk, VA (United States)

2017-04-17

Highlights of the research include: the determination of the form of the lowest energy gluonic excitation within QCD and the spectrum of hybrid hadrons which follows; the first calculation of the spectrum of hybrid baryons within a first-principles approach to QCD; a detailed mapping out of the phase-shift of elastic ππ scattering featuring the ρ resonance at two values of the light quark mass within lattice QCD; the first (and to date, only) determinations of coupled-channel meson-meson scattering within first-principles QCD; the first (and to date, only) determinations of the radiative coupling of a resonant state, the ρ appearing in πγ→ππ; the first (and to date, only) determination of the properties of the broad σ resonance in elastic ππ scattering within QCD without unjustified approximations.

Baryon interactions in lattice QCD: the direct method vs. the HAL QCD potential method

Science.gov (United States)

Iritani, T.; HAL QCD Collaboration

We make a detailed comparison between the direct method and the HAL QCD potential method for the baryon-baryon interactions, taking the $\\Xi\\Xi$ system at $m_\\pi= 0.51$ GeV in 2+1 flavor QCD and using both smeared and wall quark sources. The energy shift $\\Delta E_\\mathrm{eff}(t)$ in the direct method shows the strong dependence on the choice of quark source operators, which means that the results with either (or both) source are false. The time-dependent HAL QCD method, on the other hand, gives the quark source independent $\\Xi\\Xi$ potential, thanks to the derivative expansion of the potential, which absorbs the source dependence to the next leading order correction. The HAL QCD potential predicts the absence of the bound state in the $\\Xi\\Xi$($^1$S$_0$) channel at $m_\\pi= 0.51$ GeV, which is also confirmed by the volume dependence of finite volume energy from the potential. We also demonstrate that the origin of the fake plateau in the effective energy shift $\\Delta E_\\mathrm{eff}(t)$ at $t \\sim 1$ fm can be clarified by a few low-lying eigenfunctions and eigenvalues on the finite volume derived from the HAL QCD potential, which implies that the ground state saturation of $\\Xi\\Xi$($^1$S$_0$) requires $t \\sim 10$ fm in the direct method for the smeared source on $(4.3 \\ \\mathrm{fm})^3$ lattice, while the HAL QCD method does not suffer from such a problem.

Perturbative QCD (1/3)

CERN Multimedia

CERN. Geneva

2013-01-01

Perturbative QCD is the general theoretical framework for describing hard scattering processes yielding multiparticle production at hadron colliders. In these lectures, we shall introduce fundamental features of perturbative QCD and describe its application to several high energy collider processes, including jet production in electron-positron annihilation, deep inelastic scattering, Higgs boson and gauge boson production at the LHC.

QCD roadshow rolls on

International Nuclear Information System (INIS)

Anon.

1979-01-01

Is quantum chromodynamics (QCD) the ultimate theory of hadronic phenomena? Or, put more sceptically, can one tell QCD from a hole in the ground? This is the title of a new theory roadshow, which after a successful premiere at CERN went on to attract a large audience at Erice, Sicily, during the recent international school of subnuclear physics

QCD roadshow rolls on

Energy Technology Data Exchange (ETDEWEB)

Anon.

1979-10-15

Is quantum chromodynamics (QCD) the ultimate theory of hadronic phenomena? Or, put more sceptically, can one tell QCD from a hole in the ground? This is the title of a new theory roadshow, which after a successful premiere at CERN went on to attract a large audience at Erice, Sicily, during the recent international school of subnuclear physics.

Topology in dynamical lattice QCD simulations

International Nuclear Information System (INIS)

Gruber, Florian

2012-01-01

Lattice simulations of Quantum Chromodynamics (QCD), the quantum field theory which describes the interaction between quarks and gluons, have reached a point were contact to experimental data can be made. The underlying mechanisms, like chiral symmetry breaking or the confinement of quarks, are however still not understood. This thesis focuses on topological structures in the QCD vacuum. Those are not only mathematically interesting but also closely related to chiral symmetry and confinement. We consider methods to identify these objects in lattice QCD simulations. Based on this, we explore the structures resulting from different discretizations and investigate the effect of a very strong electromagnetic field on the QCD vacuum.

Topology in dynamical lattice QCD simulations

Energy Technology Data Exchange (ETDEWEB)

Gruber, Florian

2012-08-20

Lattice simulations of Quantum Chromodynamics (QCD), the quantum field theory which describes the interaction between quarks and gluons, have reached a point were contact to experimental data can be made. The underlying mechanisms, like chiral symmetry breaking or the confinement of quarks, are however still not understood. This thesis focuses on topological structures in the QCD vacuum. Those are not only mathematically interesting but also closely related to chiral symmetry and confinement. We consider methods to identify these objects in lattice QCD simulations. Based on this, we explore the structures resulting from different discretizations and investigate the effect of a very strong electromagnetic field on the QCD vacuum.

Conformal Aspects of QCD

Energy Technology Data Exchange (ETDEWEB)

Brodsky, S

2003-11-19

Theoretical and phenomenological evidence is now accumulating that the QCD coupling becomes constant at small virtuality; i.e., {alpha}{sub s}(Q{sup 2}) develops an infrared fixed point in contradiction to the usual assumption of singular growth in the infrared. For example, the hadronic decays of the {tau} lepton can be used to determine the effective charge {alpha}{sub {tau}}(m{sub {tau}{prime}}{sup 2}) for a hypothetical {tau}-lepton with mass in the range 0 < m{sub {tau}{prime}} < m{sub {tau}}. The {tau} decay data at low mass scales indicates that the effective charge freezes at a value of s = m{sub {tau}{prime}}{sup 2} of order 1 GeV{sup 2} with a magnitude {alpha}{sub {tau}} {approx} 0.9 {+-} 0.1. The near-constant behavior of effective couplings suggests that QCD can be approximated as a conformal theory even at relatively small momentum transfer and why there are no significant running coupling corrections to quark counting rules for exclusive processes. The AdS/CFT correspondence of large N{sub c} supergravity theory in higher-dimensional anti-de Sitter space with supersymmetric QCD in 4-dimensional space-time also has interesting implications for hadron phenomenology in the conformal limit, including an all-orders demonstration of counting rules for exclusive processes and light-front wavefunctions. The utility of light-front quantization and light-front Fock wavefunctions for analyzing nonperturbative QCD and representing the dynamics of QCD bound states is also discussed.

The AdS/CFT Correspondence and Holographic QCD

International Nuclear Information System (INIS)

Erlich, J.

2012-01-01

Holographic QCD is an extra-dimensional approach to modeling QCD resonances and their interactions. Holographic models encode information about chiral symmetry breaking, Weinberg sum rules, vector meson dominance, and other phenomenological features of QCD. There are two complementary approaches to holographic model building: a top-down approach which begins with string-theory brane configurations, and a bottom-up approach which is more phenomenological. In this talk I will describe the AdS/CFT correspondence, which motivates Holographic QCD, and the techniques used to build holographic models of QCD and to calculate observables in those models. I will also discuss an intriguing light cone approach to Holographic QCD discovered by Brodsky and De Teramond. (author)

Some new/old approaches to QCD

International Nuclear Information System (INIS)

Gross, D.J.

1992-11-01

In this lecture I shall discuss some recent attempts to revive some old ideas to address the problem of solving QCD. I believe that it is timely to return to this problem which has been woefully neglected for the last decade. QCD is a permanent part of the theoretical landscape and eventually we will have to develop analytic tools for dealing with the theory in the infra-red. Lattice techniques are useful but they have not yet lived up to their promise. Even if one manages to derive the hadronic spectrum numerically, to an accuracy of 10% or even 1%, we will not be truly satisfied unless we have some analytic understanding of the results. Also, lattice Monte-Carlo methods can only be used to answer a small set of questions. Many issues of great conceptual and practical interest-in particular the calculation of scattering amplitudes, are thus far beyond lattice control. Any progress in controlling QCD in an explicit analytic, fashion would be of great conceptual value. It would also be of great practical aid to experimentalists, who must use rather ad-hoc and primitive models of QCD scattering amplitudes to estimate the backgrounds to interesting new physics. I will discuss an attempt to derive a string representation of QCD and a revival of the large N approach to QCD. Both of these ideas have a long history, many theorist-years have been devoted to their pursuit-so far with little success. I believe that it is time to try again. In part this is because of the progress in the last few years in string theory. Our increased understanding of string theory should make the attempt to discover a stringy representation of QCD easier, and the methods explored in matrix models might be employed to study the large N limit of QCD

Some New/Old Approaches to QCD

Science.gov (United States)

Gross, D. J.

1992-11-01

In this lecture I shall discuss some recent attempts to revive some old ideas to address the problem of solving QCD. I believe that it is timely to return to this problem which has been woefully neglected for the last decade. QCD is a permanent part of the theoretical landscape and eventually we will have to develop analytic tools for dealing with the theory in the infra-red. Lattice techniques are useful but they have not yet lived up to their promise. Even if one manages to derive the hadronic spectrum numerically, to an accuracy of 10% or even 1%, we will not be truly satisfied unless we have some analytic understanding of the results. Also, lattice Monte-Carlo methods can only be used to answer a small set of questions. Many issues of great conceptual and practical interest-in particular the calculation of scattering amplitudes, are thus far beyond lattice control. Any progress in controlling QCD in an explicit analytic, fashion would be of great conceptual value. It would also be of great practical aid to experimentalists, who must use rather ad-hoc and primitive models of QCD scattering amplitudes to estimate the backgrounds to interesting new physics. I will discuss an attempt to derive a string representation of QCD and a revival of the large N approach to QCD. Both of these ideas have a long history, many theorist-years have been devoted to their pursuit-so far with little success. I believe that it is time to try again. In part this is because of the progress in the last few years in string theory. Our increased understanding of string theory should make the attempt to discover a stringy representation of QCD easier, and the methods explored in matrix models might be employed to study the large N limit of QCD.

Some new/old approaches to QCD

Energy Technology Data Exchange (ETDEWEB)

Gross, D.J.

1992-11-01

In this lecture I shall discuss some recent attempts to revive some old ideas to address the problem of solving QCD. I believe that it is timely to return to this problem which has been woefully neglected for the last decade. QCD is a permanent part of the theoretical landscape and eventually we will have to develop analytic tools for dealing with the theory in the infra-red. Lattice techniques are useful but they have not yet lived up to their promise. Even if one manages to derive the hadronic spectrum numerically, to an accuracy of 10% or even 1%, we will not be truly satisfied unless we have some analytic understanding of the results. Also, lattice Monte-Carlo methods can only be used to answer a small set of questions. Many issues of great conceptual and practical interest-in particular the calculation of scattering amplitudes, are thus far beyond lattice control. Any progress in controlling QCD in an explicit analytic, fashion would be of great conceptual value. It would also be of great practical aid to experimentalists, who must use rather ad-hoc and primitive models of QCD scattering amplitudes to estimate the backgrounds to interesting new physics. I will discuss an attempt to derive a string representation of QCD and a revival of the large N approach to QCD. Both of these ideas have a long history, many theorist-years have been devoted to their pursuit-so far with little success. I believe that it is time to try again. In part this is because of the progress in the last few years in string theory. Our increased understanding of string theory should make the attempt to discover a stringy representation of QCD easier, and the methods explored in matrix models might be employed to study the large N limit of QCD.

Nuclear properties from perturbative QCD

International Nuclear Information System (INIS)

Close, F.E.; Roberts, R.G.; Ross, G.G.

1986-01-01

Two apparently different descriptions of quark distributions in a nucleus may in fact be connected. A ''duality'' between the QCD approach and the conventional model of nucleon binding leads to nuclear properties being simply related to the anomalous dimensions of QCD. (orig.)

Chiral perturbation theory for lattice QCD

Energy Technology Data Exchange (ETDEWEB)

Baer, Oliver

2010-07-21

The formulation of chiral perturbation theory (ChPT) for lattice Quantum Chromodynamics (QCD) is reviewed. We start with brief summaries of ChPT for continuum QCD as well as the Symanzik effective theory for lattice QCD. We then review the formulation of ChPT for lattice QCD. After an additional chapter on partial quenching and mixed action theories various concrete applications are discussed: Wilson ChPT, staggered ChPT and Wilson ChPT with a twisted mass term. The remaining chapters deal with the epsilon regime with Wilson fermions and selected results in mixed action ChPT. Finally, the formulation of heavy vector meson ChPT with Wilson fermions is discussed. (orig.)

Chiral perturbation theory for lattice QCD

International Nuclear Information System (INIS)

Baer, Oliver

2010-01-01

The formulation of chiral perturbation theory (ChPT) for lattice Quantum Chromodynamics (QCD) is reviewed. We start with brief summaries of ChPT for continuum QCD as well as the Symanzik effective theory for lattice QCD. We then review the formulation of ChPT for lattice QCD. After an additional chapter on partial quenching and mixed action theories various concrete applications are discussed: Wilson ChPT, staggered ChPT and Wilson ChPT with a twisted mass term. The remaining chapters deal with the epsilon regime with Wilson fermions and selected results in mixed action ChPT. Finally, the formulation of heavy vector meson ChPT with Wilson fermions is discussed. (orig.)

Dynamical chiral-symmetry breaking in dual QCD

International Nuclear Information System (INIS)

Krein, G.; Williams, A.G.

1991-01-01

We have extended recent studies by Baker, Ball, and Zachariasen (BBZ) of dynamical chiral-symmetry breaking in dual QCD. Specifically, we have taken dual QCD to specify the nonperturbative infrared nature of the quark-quark interaction and then we have smoothly connected onto this the known leading-log perturbative QCD interaction in the ultraviolet region. In addition, we have solved for a momentum-dependent self-energy and have used the complete lowest-order dual QCD quark-quark interaction. We calculate the quark condensate left-angle bar qq right-angle and the pion decay constant f π within this model. We find that the dual QCD parameters needed to give acceptable results are reasonably consistent with those extracted from independent physical considerations by BBZ

Modeling the thermodynamics of QCD

Energy Technology Data Exchange (ETDEWEB)

Hell, Thomas

2010-07-26

Strongly interacting (QCD) matter is expected to exhibit a multifaceted phase structure: a hadron gas at low temperatures, a quark-gluon plasma at very high temperatures, nuclear matter in the low-temperature and high-density region, color superconductors at asymptotically high densities. Most of the conjectured phases cannot yet be scrutinized by experiments. Much of the present picture - particularly concerning the intermediate temperature and density area of the phase diagram of QCD matter - is based on model calculations. Further insights come from Lattice-QCD computations. The present thesis elaborates a nonlocal covariant extension of the Nambu and Jona-Lasinio (NJL) model with built-in constraints from the running coupling of QCD at high-momentum and instanton physics at low-momentum scales. We present this model for two and three quark flavors (in the latter case paying particular attention to the axial anomaly). At finite temperatures and densities, gluon dynamics is incorporated through a gluonic background field, expressed in terms of the Polyakov loop (P). The thermodynamics of this nonlocal PNJL model accounts for both chiral and deconfinement transitions. We obtain results in mean-field approximation and beyond, including additional pionic and kaonic contributions to the chiral condensate, the pressure and other thermodynamic quantities. Finally, the nonlocal PNJL model is applied to the finite-density region of the QCD phase diagram; for three quark flavors we investigate, in particular, the dependence of the critical point appearing in the models on the axial anomaly. The thesis closes with a derivation of the nonlocal PNJL model from first principles of QCD. (orig.)

Heavy flavor production in QCD

International Nuclear Information System (INIS)

Hoyer, P.

1989-01-01

In this paper a brief survey is given of the status of heavy quark hadroproduction in QCD. The next-to-leading order calculation allows an estimate of the theoretical uncertainties to be made. They are manageable for top, but considerable for charm. The data on charm continues to show an excess of events at large x F , compared to QCD expectations. This may be linked to the measured anomalous A-dependence of the cross section on nuclear targets, also present at large x F . QCD models for the diffractive production of heavy quarks remain to be tested experimentally

Hadronic and nuclear interactions in QCD

International Nuclear Information System (INIS)

1982-01-01

Despite the evidence that QCD - or something close to it - gives a correct description of the structure of hadrons and their interactions, it seems paradoxical that the theory has thus far had very little impact in nuclear physics. One reason for this is that the application of QCD to distances larger than 1 fm involves coherent, non-perturbative dynamics which is beyond present calculational techniques. For example, in QCD the nuclear force can evidently be ascribed to quark interchange and gluon exchange processes. These, however, are as complicated to analyze from a fundamental point of view as is the analogous covalent bond in molecular physics. Since a detailed description of quark-quark interactions and the structure of hadronic wavefunctions is not yet well-understood in QCD, it is evident that a quantitative first-principle description of the nuclear force will require a great deal of theoretical effort. Another reason for the limited impact of QCD in nuclear physics has been the conventional assumption that nuclear interactions can for the most part be analyzed in terms of an effective meson-nucleon field theory or potential model in isolation from the details of short distance quark and gluon structure of hadrons. These lectures, argue that this view is untenable: in fact, there is no correspondence principle which yields traditional nuclear physics as a rigorous large-distance or non-relativistic limit of QCD dynamics. On the other hand, the distinctions between standard nuclear physics dynamics and QCD at nuclear dimensions are extremely interesting and illuminating for both particle and nuclear physics

The current matrix elements from HAL QCD method

Science.gov (United States)

Watanabe, Kai; Ishii, Noriyoshi

2018-03-01

HAL QCD method is a method to construct a potential (HAL QCD potential) that reproduces the NN scattering phase shift faithful to the QCD. The HAL QCD potential is obtained from QCD by eliminating the degrees of freedom of quarks and gluons and leaving only two particular hadrons. Therefor, in the effective quantum mechanics of two nucleons defined by HAL QCD potential, the conserved current consists not only of the nucleon current but also an extra current originating from the potential (two-body current). Though the form of the two-body current is closely related to the potential, it is not straight forward to extract the former from the latter. In this work, we derive the the current matrix element formula in the quantum mechanics defined by the HAL QCD potential. As a first step, we focus on the non-relativistic case. To give an explicit example, we consider a second quantized non-relativistic two-channel coupling model which we refer to as the original model. From the original model, the HAL QCD potential for the open channel is constructed by eliminating the closed channel in the elastic two-particle scattering region. The current matrix element formula is derived by demanding the effective quantum mechanics defined by the HAL QCD potential to respond to the external field in the same way as the original two-channel coupling model.

International Meeting: Excited QCD 2014

CERN Document Server

Giacosa, Francesco; Malek, Magdalena; Marinkovic, Marina; Parganlija, Denis

2014-01-01

Excited QCD 2014 will take place on the beautiful Bjelasnica mountain located in the vicinity of the Bosnian capital Sarajevo. Bjelasnica was a venue of the XIV Winter Olympic Games and it is situated only 30 kilometers from Sarajevo International Airport. The workshop program will start on February 2 and finish on February 8, 2014, with scientific lectures taking place from February 3 to 7. Workshop participants will be accomodated in Hotel Marsal, only couple of minutes by foot from the Olympic ski slopes. ABOUT THE WORKSHOP This edition is the sixth in a series of workshops that were previously organised in Poland, Slovakia, France and Portugal. Following the succesful meeting in 2013, the Workshop is returning to Sarajevo Olympic mountains in 2014, exactly thirty years after the Games. The workshop covers diverse aspects of QCD: (i) QCD at low energies: excited hadrons, glueballs, multiquarks. (ii) QCD at high temperatures and large densities: heavy-ion collisions, jets, diffraction, hadronisation, quark-...

Beyond QCD: Why and How

International Nuclear Information System (INIS)

Preparata, G.

1983-01-01

In this paper the necessity of going beyond Quantum chromodynamics is argued, and a new theory of Isotropic Chromodynamics (ICD) is introduced. The basic theoretical notions behind QCD--quarks, colors, and gauge theory are retained, but the conclusion that QCD must be the theory of hadrions is questioned. Two points of QCD are reviewed, gluons (including glueballs), and asymptotic freedom. It is suggested that much of this theory is wishful thinking. Beyond QCD, aspects which are puzzling in hadrodynamics are well understood in two-dimensional gauge theories (confinement, freedom at short distances etc). Anisotropic chromodynamics is proposed in the attempt to conjugate the basic pillars of hadrodynamics with the peculiar characteristics of two-dimensional gauge dynamics. In order to construct a gauge dynamics for the color field which is isomorphic to a two-dimensional gauge-theory base space must be enlarged to a seven dimension space-time structure, to be called Anisotropic Space-Time (AST). The ideas and present achievements of ICD are then reviewed

Novel QCD Phenomenology

Energy Technology Data Exchange (ETDEWEB)

Brodsky, Stanley J.; /SLAC /Southern Denmark U., CP3-Origins

2011-08-12

I review a number of topics where conventional wisdom in hadron physics has been challenged. For example, hadrons can be produced at large transverse momentum directly within a hard higher-twist QCD subprocess, rather than from jet fragmentation. Such 'direct' processes can explain the deviations from perturbative QCD predictions in measurements of inclusive hadron cross sections at fixed x{sub T} = 2p{sub T}/{radical}s, as well as the 'baryon anomaly', the anomalously large proton-to-pion ratio seen in high centrality heavy ion collisions. Initial-state and final-state interactions of the struck quark, the soft-gluon rescattering associated with its Wilson line, lead to Bjorken-scaling single-spin asymmetries, diffractive deep inelastic scattering, the breakdown of the Lam-Tung relation in Drell-Yan reactions, as well as nuclear shadowing and antishadowing. The Gribov-Glauber theory predicts that antishadowing of nuclear structure functions is not universal, but instead depends on the flavor quantum numbers of each quark and antiquark, thus explaining the anomalous nuclear dependence measured in deep-inelastic neutrino scattering. Since shadowing and antishadowing arise from the physics of leading-twist diffractive deep inelastic scattering, one cannot attribute such phenomena to the structure of the nucleus itself. It is thus important to distinguish 'static' structure functions, the probability distributions computed from the square of the target light-front wavefunctions, versus 'dynamical' structure functions which include the effects of the final-state rescattering of the struck quark. The importance of the J = 0 photon-quark QCD contact interaction in deeply virtual Compton scattering is also emphasized. The scheme-independent BLM method for setting the renormalization scale is discussed. Eliminating the renormalization scale ambiguity greatly improves the precision of QCD predictions and increases the sensitivity of

Multi-meson systems in lattice QCD / Many-body QCD

Energy Technology Data Exchange (ETDEWEB)

Detmold, William [College of William and Mary, Williamsburg, VA (United States)

2013-08-31

Nuclear physics entails the study of the properties and interactions of hadrons, such as the proton and neutron, and atomic nuclei and it is central to our understanding of our world at the smallest scales. The underlying basis for nuclear physics is provided by the Standard Model of particle physics which describes how matter interacts through the strong, electromagnetic and weak (electroweak) forces. This theory was developed in the 1970s and provides an extremely successful description of our world at the most fundamental level to which it has been probed. The Standard Model has been, and continues to be, subject to stringent tests at particle accelerators around the world, so far passing without blemish. However, at the relatively low energies that are relevant for nuclear physics, calculations involving the strong interaction, governed by the equations of Quantum Chromodynamics (QCD), are enormously challenging, and to date, the only systematic way to perform them is numerically, using a framework known as lattice QCD (LQCD). In this approach, one discretizes space-time and numerically solves the equations of QCD on a space-time lattice; for realistic calculations, this requires highly optimized algorithms and cutting-edge high performance computing (HPC) resources. Progress over the project period is discussed in detail in the following subsections

QCD: Questions, challenges, and dilemmas

International Nuclear Information System (INIS)

Bjorken, J.

1996-11-01

An introduction to some outstanding issues in QCD is presented, with emphasis on work by Diakonov and co-workers on the influence of the instanton vacuum on low-energy QCD observables. This includes the calculation of input valence-parton distributions for deep-inelastic scattering. 35 refs., 3 figs

Experimental Summary Moriond QCD 2007

CERN Document Server

Rolandi, Gigi

2007-01-01

More than 90 speakers gave a presentation at this years Moriond QCD conference and more than 60 talks reported the experimental status and perspectives on Standard Model, especially QCD, search for new physics, quark spectroscopy and Heavy Ions physics. I summarize what I consider the highlights of these presentations.

Quarklei: nuclear physics from QCD

International Nuclear Information System (INIS)

Goldman, T.

1985-01-01

The difficulties posed for nuclear physics by either recognizing or ignoring QCD, are discussed. A QCD model for nuclei is described. A crude approximation is shown to qualitatively reproduce saturation of nuclear binding energies and the EMC effect. The model is applied seriously to small nuclei, and to hypernuclei

Color ordering in QCD

OpenAIRE

Schuster, Theodor

2013-01-01

We derive color decompositions of arbitrary tree and one-loop QCD amplitudes into color ordered objects called primitive amplitudes. Furthermore, we derive general fermion flip and reversion identities spanning the null space among the primitive amplitudes and use them to prove that all color ordered tree amplitudes of massless QCD can be written as linear combinations of color ordered tree amplitudes of $\\mathcal{N}=4$ super Yang-Mills theory.

QCD and Light-Front Dynamics

International Nuclear Information System (INIS)

Brodsky, Stanley J.; de Teramond, Guy F.

2011-01-01

AdS/QCD, the correspondence between theories in a dilaton-modified five-dimensional anti-de Sitter space and confining field theories in physical space-time, provides a remarkable semiclassical model for hadron physics. Light-front holography allows hadronic amplitudes in the AdS fifth dimension to be mapped to frame-independent light-front wavefunctions of hadrons in physical space-time. The result is a single-variable light-front Schroedinger equation which determines the eigenspectrum and the light-front wavefunctions of hadrons for general spin and orbital angular momentum. The coordinate z in AdS space is uniquely identified with a Lorentz-invariant coordinate ζ which measures the separation of the constituents within a hadron at equal light-front time and determines the off-shell dynamics of the bound state wavefunctions as a function of the invariant mass of the constituents. The hadron eigenstates generally have components with different orbital angular momentum; e.g., the proton eigenstate in AdS/QCD with massless quarks has L = 0 and L = 1 light-front Fock components with equal probability. Higher Fock states with extra quark-anti quark pairs also arise. The soft-wall model also predicts the form of the nonperturbative effective coupling and its β-function. The AdS/QCD model can be systematically improved by using its complete orthonormal solutions to diagonalize the full QCD light-front Hamiltonian or by applying the Lippmann-Schwinger method to systematically include QCD interaction terms. Some novel features of QCD are discussed, including the consequences of confinement for quark and gluon condensates. A method for computing the hadronization of quark and gluon jets at the amplitude level is outlined.

QCD and Light-Front Dynamics

Energy Technology Data Exchange (ETDEWEB)

Brodsky, Stanley J.; de Teramond, Guy F.; /SLAC /Southern Denmark U., CP3-Origins /Costa Rica U.

2011-01-10

AdS/QCD, the correspondence between theories in a dilaton-modified five-dimensional anti-de Sitter space and confining field theories in physical space-time, provides a remarkable semiclassical model for hadron physics. Light-front holography allows hadronic amplitudes in the AdS fifth dimension to be mapped to frame-independent light-front wavefunctions of hadrons in physical space-time. The result is a single-variable light-front Schroedinger equation which determines the eigenspectrum and the light-front wavefunctions of hadrons for general spin and orbital angular momentum. The coordinate z in AdS space is uniquely identified with a Lorentz-invariant coordinate {zeta} which measures the separation of the constituents within a hadron at equal light-front time and determines the off-shell dynamics of the bound state wavefunctions as a function of the invariant mass of the constituents. The hadron eigenstates generally have components with different orbital angular momentum; e.g., the proton eigenstate in AdS/QCD with massless quarks has L = 0 and L = 1 light-front Fock components with equal probability. Higher Fock states with extra quark-anti quark pairs also arise. The soft-wall model also predicts the form of the nonperturbative effective coupling and its {beta}-function. The AdS/QCD model can be systematically improved by using its complete orthonormal solutions to diagonalize the full QCD light-front Hamiltonian or by applying the Lippmann-Schwinger method to systematically include QCD interaction terms. Some novel features of QCD are discussed, including the consequences of confinement for quark and gluon condensates. A method for computing the hadronization of quark and gluon jets at the amplitude level is outlined.

QCD as a topologically ordered system

International Nuclear Information System (INIS)

Zhitnitsky, Ariel R.

2013-01-01

We argue that QCD belongs to a topologically ordered phase similar to many well-known condensed matter systems with a gap such as topological insulators or superconductors. Our arguments are based on an analysis of the so-called “deformed QCD” which is a weakly coupled gauge theory, but nevertheless preserves all the crucial elements of strongly interacting QCD, including confinement, nontrivial θ dependence, degeneracy of the topological sectors, etc. Specifically, we construct the so-called topological “BF” action which reproduces the well known infrared features of the theory such as non-dispersive contribution to the topological susceptibility which cannot be associated with any propagating degrees of freedom. Furthermore, we interpret the well known resolution of the celebrated U(1) A problem where the would be η ′ Goldstone boson generates its mass as a result of mixing of the Goldstone field with a topological auxiliary field characterizing the system. We then identify the non-propagating auxiliary topological field of the BF formulation in deformed QCD with the Veneziano ghost (which plays the crucial role in resolution of the U(1) A problem). Finally, we elaborate on relation between “string-net” condensation in topologically ordered condensed matter systems and long range coherent configurations, the “skeletons”, studied in QCD lattice simulations. -- Highlights: •QCD may belong to a topologically ordered phase similar to condensed matter (CM) systems. •We identify the non-propagating topological field in deformed QCD with the Veneziano ghost. •Relation between “string-net” condensates in CM systems and the “skeletons” in QCD lattice simulations is studied

QCD and Hadron Physics

Energy Technology Data Exchange (ETDEWEB)

Brodsky, Stanley J.; Deshpande, Abhay L.; Gao, Haiyan; McKeown, Robert D.; Meyer, Curtis A.; Meziani, Zein-Eddine; Milner, Richard G.; Qiu, Jianwei; Richards, David G.; Roberts, Craig D.

2015-02-26

This White Paper presents the recommendations and scientific conclusions from the Town Meeting on QCD and Hadronic Physics that took place in the period 13-15 September 2014 at Temple University as part of the NSAC 2014 Long Range Planning process. The meeting was held in coordination with the Town Meeting on Phases of QCD and included a full day of joint plenary sessions of the two meetings. The goals of the meeting were to report and highlight progress in hadron physics in the seven years since the 2007 Long Range Plan (LRP07), and present a vision for the future by identifying the key questions and plausible paths to solutions which should define the next decade. The introductory summary details the recommendations and their supporting rationales, as determined at the Town Meeting on QCD and Hadron Physics, and the endorsements that were voted upon. The larger document is organized as follows. Section 2 highlights major progress since the 2007 LRP. It is followed, in Section 3, by a brief overview of the physics program planned for the immediate future. Finally, Section 4 provides an overview of the physics motivations and goals associated with the next QCD frontier: the Electron-Ion-Collider.

Scattering processes and resonances from lattice QCD

Science.gov (United States)

Briceño, Raúl A.; Dudek, Jozef J.; Young, Ross D.

2018-04-01

The vast majority of hadrons observed in nature are not stable under the strong interaction; rather they are resonances whose existence is deduced from enhancements in the energy dependence of scattering amplitudes. The study of hadron resonances offers a window into the workings of quantum chromodynamics (QCD) in the low-energy nonperturbative region, and in addition many probes of the limits of the electroweak sector of the standard model consider processes which feature hadron resonances. From a theoretical standpoint, this is a challenging field: the same dynamics that binds quarks and gluons into hadron resonances also controls their decay into lighter hadrons, so a complete approach to QCD is required. Presently, lattice QCD is the only available tool that provides the required nonperturbative evaluation of hadron observables. This article reviews progress in the study of few-hadron reactions in which resonances and bound states appear using lattice QCD techniques. The leading approach is described that takes advantage of the periodic finite spatial volume used in lattice QCD calculations to extract scattering amplitudes from the discrete spectrum of QCD eigenstates in a box. An explanation is given of how from explicit lattice QCD calculations one can rigorously garner information about a variety of resonance properties, including their masses, widths, decay couplings, and form factors. The challenges which currently limit the field are discussed along with the steps being taken to resolve them.

Aspects of QCD factorization

International Nuclear Information System (INIS)

Neubert, Matthias

2001-01-01

The QCD factorization approach provides the theoretical basis for a systematic analysis of nonleptonic decay amplitudes of B mesons in the heavy-quark limit. After recalling the basic ideas underlying this formalism, several tests of QCD factorization in the decays B→D (*) L, B→K * γ, and B→πK, ππ are discussed. It is then illustrated how factorization can be used to obtain new constraints on the parameters of the unitarity triangle

Gravitational waves generated from the cosmological QCD phase transition within AdS/QCD

Directory of Open Access Journals (Sweden)

M. Ahmadvand

2017-09-01

Full Text Available We study the gravitational waves produced by the collision of the bubbles as a probe for the cosmological first order QCD phase transition, considering heavy static quarks. Using AdS/QCD and the correspondence between a first order Hawking–Page phase transition and confinement–deconfinement phase transition, we find the spectrum and the strain amplitude of the gravitational wave within the hard and soft wall models. We postulate the duration of the phase transition corresponds to the evaporation time of the black hole in the five dimensional dual gravity space, and thereby obtain a bound on the string length in the space and correspondingly on the duration of the QCD phase transition. We also show that IPTA and SKA detectors will be able to detect these gravitational waves, which can be an evidence for the first order deconfinement transition.

Nonperturbative QCD and elastic processes at CEBAF energies

Energy Technology Data Exchange (ETDEWEB)

Radyushkin, A.V. [Old Dominion Univ., Norfolk, VA (United States)]|[Continuous Electron Beam Accelerator Facility, Newport News, VA (United States)

1994-04-01

The author outlines how one can approach nonperturbative aspects of the QCD dynamics studying elastic processes at energies accessible at upgraded CEBAF. The author`s point is that, in the absence of a complete theory of the nonperturbative effects, a possible way out is based on a systematic use of the QCD factorization procedure which separates theoretically understood ({open_quotes}known{close_quotes}) short-distance effects and nonperturbative ({open_quotes}unknown{close_quotes}) long-distance ones. The latter include hadronic distribution amplitudes, soft components of hadronic form factors etc. Incorporating the QCD sum rule version of the QCD factorization approach, one can relate these nonperturbative functions to more fundamental objects, vacuum condensates, which accumulate information about the nonperturbative structure of the QCD vacuum. The emerging QCD sum rule picture of hadronic form factors is characterized by a dominant role of essentially nonperturbative effects in the few GeV region, with perturbative mechanisms starting to show up for momentum transfers Q{sup 2} closer to 10 GeV{sup 2} and higher. Thus, increasing CEBAF energy provides a unique opportunity for a precision study of interplay between the perturbative and nonperturbative phenomena in the QCD description of elastic processes.

Nonperturbative QCD and elastic processes at CEBAF energies

International Nuclear Information System (INIS)

Radyushkin, A.V.

1994-01-01

The author outlines how one can approach nonperturbative aspects of the QCD dynamics studying elastic processes at energies accessible at upgraded CEBAF. The author's point is that, in the absence of a complete theory of the nonperturbative effects, a possible way out is based on a systematic use of the QCD factorization procedure which separates theoretically understood (open-quotes knownclose quotes) short-distance effects and nonperturbative (open-quotes unknownclose quotes) long-distance ones. The latter include hadronic distribution amplitudes, soft components of hadronic form factors etc. Incorporating the QCD sum rule version of the QCD factorization approach, one can relate these nonperturbative functions to more fundamental objects, vacuum condensates, which accumulate information about the nonperturbative structure of the QCD vacuum. The emerging QCD sum rule picture of hadronic form factors is characterized by a dominant role of essentially nonperturbative effects in the few GeV region, with perturbative mechanisms starting to show up for momentum transfers Q 2 closer to 10 GeV 2 and higher. Thus, increasing CEBAF energy provides a unique opportunity for a precision study of interplay between the perturbative and nonperturbative phenomena in the QCD description of elastic processes

QCD at finite temperature

International Nuclear Information System (INIS)

Kikkawa, Keiji

1983-01-01

The varidity of the perturbation method in the high temperature QCD is discussed. The skeleton expansion method takes account of plasmon effects and eliminates the electric infrared singularity but not the magnetic one. A possibility of eliminating the latter, which was recently proposed, is examined by a gauge invariant skeleton expansion. The magnetic singularity is unable to be eliminated by the perturbation method. This implies that some non-perturbative approaches must be incorporated in the high temperature QCD. (author)

QCD for Collider Physics

OpenAIRE

Skands, Peter

2011-01-01

These lectures are directed at a level suitable for graduate students in experimental and theoretical High Energy Physics. They are intended to give an introduction to the theory and phenomenology of quantum chromodynamics (QCD) as it is used in collider physics applications. The aim is to bring the reader to a level where informed decisions can be made concerning different approaches and their uncertainties. The material is divided into four main areas: 1) fundamentals, 2) perturbative QCD, ...

Dynamical effects of QCD vacuum structure

International Nuclear Information System (INIS)

Ferreira, Erasmo

1994-01-01

The role of the QCD vacuum structure in the determination of the properties of states and processes occurring in the confinement regime of QCD is reviewed. The finite range of the vacuum correlations is discussed, and an analytical form is suggested for the correlation functions. The role of the vacuum quantum numbers in the phenomenology of high-energy scattering is reviewed. The vacuum correlation model of non-perturbative QCD is mentioned as a bridge between the fundamental theory and the description of the experiments. (author). 13 refs., 1 fig

Knot topology in QCD

International Nuclear Information System (INIS)

Zou, L.P.; Zhang, P.M.; Pak, D.G.

2013-01-01

We consider topological structure of classical vacuum solutions in quantum chromodynamics. Topologically non-equivalent vacuum configurations are classified by non-trivial second and third homotopy groups for coset of the color group SU(N) (N=2,3) under the action of maximal Abelian stability group. Starting with explicit vacuum knot configurations we study possible exact classical solutions. Exact analytic non-static knot solution in a simple CP 1 model in Euclidean space–time has been obtained. We construct an ansatz based on knot and monopole topological vacuum structure for searching new solutions in SU(2) and SU(3) QCD. We show that singular knot-like solutions in QCD in Minkowski space–time can be naturally obtained from knot solitons in integrable CP 1 models. A family of Skyrme type low energy effective theories of QCD admitting exact analytic solutions with non-vanishing Hopf charge is proposed

Lattice QCD for cosmology

International Nuclear Information System (INIS)

Borsanyi, Sz.; Kampert, K.H.; Fodor, Z.; Forschungszentrum Juelich; Eoetvoes Univ., Budapest

2016-06-01

We present a full result for the equation of state (EoS) in 2+1+1 (up/down, strange and charm quarks are present) flavour lattice QCD. We extend this analysis and give the equation of state in 2+1+1+1 flavour QCD. In order to describe the evolution of the universe from temperatures several hundreds of GeV to the MeV scale we also include the known effects of the electroweak theory and give the effective degree of freedoms. As another application of lattice QCD we calculate the topological susceptibility (χ) up to the few GeV temperature region. These two results, EoS and χ, can be used to predict the dark matter axion's mass in the post-inflation scenario and/or give the relationship between the axion's mass and the universal axionic angle, which acts as a initial condition of our universe.

QCD sum rules in a Bayesian approach

International Nuclear Information System (INIS)

Gubler, Philipp; Oka, Makoto

2011-01-01

A novel technique is developed, in which the Maximum Entropy Method is used to analyze QCD sum rules. The main advantage of this approach lies in its ability of directly generating the spectral function of a given operator. This is done without the need of making an assumption about the specific functional form of the spectral function, such as in the 'pole + continuum' ansatz that is frequently used in QCD sum rule studies. Therefore, with this method it should in principle be possible to distinguish narrow pole structures form continuum states. To check whether meaningful results can be extracted within this approach, we have first investigated the vector meson channel, where QCD sum rules are traditionally known to provide a valid description of the spectral function. Our results exhibit a significant peak in the region of the experimentally observed ρ-meson mass, which agrees with earlier QCD sum rules studies and shows that the Maximum Entropy Method is a useful tool for analyzing QCD sum rules.

The Operator Product Expansion Beyond Perturbation Theory in QCD

International Nuclear Information System (INIS)

Dominguez, C. A.

2011-01-01

The Operator Product Expansion (OPE) of current correlators at short distances beyond perturbation theory in QCD, together with Cauchy's theorem in the complex energy plane, are the pillars of the method of QCD sum rules. This technique provides an analytic tool to relate QCD with hadronic physics at low and intermediate energies. It has been in use for over thirty years to determine hadronic parameters, form factors, and QCD parameters such as the quark masses, and the running strong coupling at the scale of the τ-lepton. QCD sum rules provide a powerful complement to numerical simulations of QCD on the lattice. In this talk a short review of the method is presented for non experts, followed by three examples of recent applications.

Hadronic laws from QCD

International Nuclear Information System (INIS)

Cahill, R.T.

1992-01-01

A review is given of progress in deriving the effective action for hadronic physics, S[π, ρ, ω, .., anti N, N, ..], from the fundamental defining action of QCD, S[anti q, q, A μ a ]. This is a problem in quantum field theory and the most success so far has been achieved using functional integral calculus (FIC) techniques. This formulates the problem as an exercise in changing the variables of integration in the functional integrals, from those of the quark and gluon fields to those of the (bare) meson and baryon fields. The appropriate variables are determined by the dynamics of QCD, and the final hadronic variables (essentially the 'normal modes' of QCD) are local fields describing the 'centre-of-mass' motion of extended bound states of quarks. The quarks are extensively dressed by the gluons, and the detailed aspects of the hidden chiral symmetry emerge naturally from the formalism. Particular attention is given to covariant integral equations which determine bare nucleon structure (i.e. in the quenched approximation). These equations, which arise from the closed double-helix diagrams of the FIC analysis, describe the baryons in terms of quark-diquark structure, in the form of Faddeev equations. This hadronisation of QCD also generates the dressing of these baryons by the pions, and the non-local πNN coupling. (orig.)

Experimental tests of QCD

International Nuclear Information System (INIS)

Hansl-Kozanecka, T.

1992-01-01

The phenomenological aspects of Quantum Chromodynamics (QCD) are examined which are relevant for lepton-hadron, electron-positron and hadron-hadron collisions. In deep inelastic scattering the virtual γ or W/Z is used as a probe of the nucleon structure. The strong coupling constant (α s ) measurements via deep inelastic scattering and e + e - annihilation are discussed. Parton-parton collisions (e.g., hard hadron-hadron collisions) are examined as the third regime for QCD tests. (K.A.) 122 refs., 84 figs., 4 tabs

Analytic continuation in perturbative QCD

International Nuclear Information System (INIS)

Caprini, Irinel

2002-01-01

We discuss some attempts to improve standard perturbative expansion in QCD by using the analytic continuation in the momentum and the Borel complex planes. We first analyse the momentum-plane analyticity properties of the Borel-summed Green functions in perturbative QCD and the connection between the Landau singularities and the infrared renormalons. By using the analytic continuation in the Borel complex plane, we propose a new perturbative series replacing the standard expansion in powers of the normalized coupling constant a. The new expansion functions have branch point and essential singularities at the origin of the complex a-plane and divergent Taylor expansions in powers of a. On the other hand the modified expansion of the QCD correlators is convergent under rather conservative conditions. (author)

Dual QCD: A review

International Nuclear Information System (INIS)

Baker, M.; Ball, J.S.; Zachariasen, F.

1991-01-01

We review the attempts to use dual (electric) vector potentials rather than the standard magnetic vector potentials to describe QCD, particularly in the infrared regime. The use of dual potentials is motivated by the fact that in classical electrodynamics, in a medium with a dielectric constant vanishing at small momenta (as is believed to be the case in QCD), electric potentials provide a far more convenient language than do magnetic potentials. To begin with, we outline attempts to construct the QCD Lagrangian in terms of dual potentials and describe the various possibilities, their shortcomings and advantages, which so far exist. We then proceed to use the most attractive (albeit consistent as a field theory only at the tree level) of these Lagrangians in a number of applications. We show that it describes a non-Abelian dual superconductor (so that it automatically confines color), derive the static quark-antiquark potential, and various temperature dependent effects, such as deconfinement and chiral symmetry breaking. (orig.)

Color-magnetic permeability of QCD vacuum

Energy Technology Data Exchange (ETDEWEB)

Saito, T [Kyoto Prefectural Univ. of Medicine (Japan); Shigemoto, K

1980-03-01

In the very strong background gauge field the QCD true vacuum has been shown to have lower energy than the ''perturbative vacuum.'' The color-magnetic permeability of the QCD true vacuum is then calculated to be 1/2 within the quark-one-loop approximation.

Understanding of QCD through solvable models

Energy Technology Data Exchange (ETDEWEB)

Bhattacharya, G.

1980-07-01

Various aspects of strong interaction physics are discussed. It is shown that several nontrivial features arise from non-perturbative 'solutions' of QCD-like models in (1+1) dimensions. An attempt is made to bring these features in (3+1) dimensional semiclassical treatments of QCD.

Quark virtuality and QCD vacuum condensates

International Nuclear Information System (INIS)

Zhou Lijuan; Ma Weixing

2004-01-01

Based on the Dyson-Schwinger equations (DSEs) in the 'rainbow' approximation, the authors investigate the quark virtuality in the vacuum state and quantum-chromodynamics (QCD) vacuum condensates. In particular, authors calculate the local quark vacuum condensate and quark-gluon mixed condensates, and then the virtuality of quark. The calculated quark virtualities are λ u,d 2 =0.7 GeV 2 for u, d quarks, and λ s 2 =1.6 GeV 2 for s quark. The theoretical predictions are consistent with empirical values used in QCD sum rules, and also fit to lattice QCD predictions

QCD Results from ATLAS and CMS

CERN Document Server

Leyton, M; The ATLAS collaboration

2014-01-01

The ATLAS and CMS collaborations have performed a wide range of studies of QCD phenomena, from soft particle to hard photon and jet production. Recent soft-­QCD measurements include studies of the underlying event, double parton interactions and vector meson production. Differential measurements of inclusive and dijet production provide stringent tests of high­-order QCD predictions and provide input for the determination of parton density functions. Measurements of isolated, inclusive and di­-photon cross sections for high-pT photons test various theoretical predictions and further constrain PDFs. An overview of these results is given.


Determinations of the QCD strong coupling αsub(s) and the scale Λsub(QCD)

International Nuclear Information System (INIS)

Duke, D.W.; Roberts, R.G.

1984-08-01

The authors review determinations, via experiment of the strong coupling of QCD, αsub(s). In almost every case, the results are used of perturbative QCD to make the necessary extraction from data. These include scaling violations of deep inelastic scattering, e + e - annihilation experiments (including quarkonium decays) and lepton pair production. Finally estimates for Λ from lattice calculations are listed. (author)

Introduction to finite temperature and finite density QCD

International Nuclear Information System (INIS)

Kitazawa, Masakiyo

2014-01-01

It has been pointed out that QCD (Quantum Chromodynamics) in the circumstances of medium at finite temperature and density shows numbers of phenomena similar to the characteristics of solid state physics, e.g. phase transitions. In the past ten years, the very high temperature and density matter came to be observed experimentally at the heavy ion collisions. At the same time, the numerical QCD analysis at finite temperature and density attained quantitative level analysis possible owing to the remarkable progress of computers. In this summer school lecture, it has been set out to give not only the recent results, but also the spontaneous breaking of the chiral symmetry, the fundamental theory of finite temperature and further expositions as in the following four sections. The first section is titled as 'Introduction to Finite Temperature and Density QCD' with subsections of 1.1 standard model and QCD, 1.2 phase transition and phase structure of QCD, 1.3 lattice QCD and thermodynamic quantity, 1.4 heavy ion collision experiments, and 1.5 neutron stars. The second one is 'Equilibrium State' with subsections of 2.1 chiral symmetry, 2.2 vacuum state: BCS theory, 2.3 NJL (Nambu-Jona-Lasinio) model, and 2.4 color superconductivity. The third one is 'Static fluctuations' with subsections of 3.1 fluctuations, 3.2 moment and cumulant, 3.3 increase of fluctuations at critical points, 3.4 analysis of fluctuations by lattice QCD and Taylor expansion, and 3.5 experimental exploration of QCD phase structure. The fourth one is 'Dynamical Structure' with 4.1 linear response theory, 4.2 spectral functions, 4.3 Matsubara function, and 4.4 analyses of dynamical structure by lattice QCD. (S. Funahashi)

Twisted mass lattice QCD

International Nuclear Information System (INIS)

Shindler, A.

2007-07-01

I review the theoretical foundations, properties as well as the simulation results obtained so far of a variant of the Wilson lattice QCD formulation: Wilson twisted mass lattice QCD. Emphasis is put on the discretization errors and on the effects of these discretization errors on the phase structure for Wilson-like fermions in the chiral limit. The possibility to use in lattice simulations different lattice actions for sea and valence quarks to ease the renormalization patterns of phenomenologically relevant local operators, is also discussed. (orig.)

Twisted mass lattice QCD

Energy Technology Data Exchange (ETDEWEB)

Shindler, A. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC

2007-07-15

I review the theoretical foundations, properties as well as the simulation results obtained so far of a variant of the Wilson lattice QCD formulation: Wilson twisted mass lattice QCD. Emphasis is put on the discretization errors and on the effects of these discretization errors on the phase structure for Wilson-like fermions in the chiral limit. The possibility to use in lattice simulations different lattice actions for sea and valence quarks to ease the renormalization patterns of phenomenologically relevant local operators, is also discussed. (orig.)

A Bayesian analysis of QCD sum rules

International Nuclear Information System (INIS)

Gubler, Philipp; Oka, Makoto

2011-01-01

A new technique has recently been developed, in which the Maximum Entropy Method is used to analyze QCD sum rules. This approach has the virtue of being able to directly generate the spectral function of a given operator, without the need of making an assumption about its specific functional form. To investigate whether useful results can be extracted within this method, we have first studied the vector meson channel, where QCD sum rules are traditionally known to provide a valid description of the spectral function. Our results show a significant peak in the region of the experimentally observed ρ-meson mass, which is in agreement with earlier QCD sum rules studies and suggests that the Maximum Entropy Method is a strong tool for analyzing QCD sum rules.

Challenges for QCD theory: some personal reflections

International Nuclear Information System (INIS)

Sjöstrand, T

2013-01-01

At the LHC all processes are QCD ones, whether ‘signal’ or ‘background’. In this review the frontiers of current QCD research are addressed, towards increased understanding, improved calculational precision, and role in potential future discoveries. Issues raised include: - the limits of perturbative QCD calculations and parton distribution usage,; - the nature of multiparton interactions,; - the impact of colour reconnection on physical observables,; - the need for progress on hadronization modelling,; - the improvements of parton showers and their combination with the matrix-element description,; - the use of QCD concepts in Beyond-the-Standard-Model scenarios and; - the key position of event generators and other software in the successful exploration of LHC physics. On the way, several questions are posed, where further studies are needed. (paper)

Topics in perturbative QCD beyond the leading order

International Nuclear Information System (INIS)

Buras, A.J.

1979-08-01

The basic structure of QCD formulae for various inclusive and semi-inclusive processes is presented. Next to leading order QCD corrections to inclusive deep-inelastic scattering are discussed in some detail. The methods for calculations of QCD corrections (leading, next to leading) to semi-inclusive processes are outlined. Some results of these calculations are discussed. 58 references

Stabilisation goals for concentrations of climate-relevant gaseous emissions: Effects and emission pathways. Final report; Stabilisierungsziele fuer Treibhausgaskonzentrationen: Eine Abschaetzung der Auswirkungen und der Emissionspfade. Abschlussbericht

Energy Technology Data Exchange (ETDEWEB)

Onigkeit, J.; Alcamo, J.; Kaspar, F.; Roesch, T.

2000-04-01

Two different stabilisation goals were assumed, i.e. 550 ppm and 450 ppm of carbon dioxide. First, the global anthropogenic carbon dioxide emissions were calculated that are permissible to reach these goals. Secondly, the global and regional environmental effects of these concentration goals were assessed. In this, carbon dioxide, nitric oxides and methane emissions from power generation, industry and agriculture were considered. Apart from an investigation of the global reduction strategies required, a key was developed for sharing the global reduction loads between Annex B countries and non-Annex B countries. To reach a stable concentration of 550 ppm carbon dioxide in the atmosphere, the global anthropogenic carbon dioxide emissions per annum may increase slightly until 2030 but must be lowered to the 1990 level by 2100. In the case of 450 ppm, the 1990 level must even be halved by 2100. The consequences of climate change for agriculture, natural vegetation, availability of water, and sea levels were investigated in consideration of regional variations in carbon dioxide emissions and emission reduction measures. In spite of extensive emission control, the area of reduced agricultural productivity will grow rapidly in both cases, and natural vegetation will be endangered, although with strong regional variations. [German] Ausgehend von zwei langfristigen Klimaschutzzielen (Stabilisierung der atmosphaerischen CO{sub 2}-Konzentration bei 550 ppm und bei 450 ppm) wurde mit Hilfe des IMAGE 2.1 Modells: (1) Eine Berechnung der globalen anthropogenen Treibhausgasemissionen durchgefuehrt, die zwischen 1990 und 2100 erlaubt sind, um diese Konzentrationsziele zu erreichen. (2) Wurde eine Abschaetzung der globalen und regionalen Umweltauswirkungen durch den Klimawandel durchgefuehrt, der mit diesen Konzentrationszielen einhergeht. Bei der Analyse wurden CO{sub 2}-, N{sub 2}O- und CH{sub 4} Emissionen aus dem Energie/Industrie- und dem landwirtschaftlichen Sektor

High-temperature acquifer thermal storage and underground heat storage; IEA ECES Annex 12: Hochtemperatur-Erdwaermesonden- und Aquiferwaermespeicher

Energy Technology Data Exchange (ETDEWEB)

Sanner, B.; Knoblich, K. [Giessen Univ. (Germany). Inst. fuer Angewandte Geowissenschaften; Koch, M.; Adinolfi, M. [Stuttgart Univ. (Germany). Inst. fuer Siedlungswasserbau, Wasserguete und Abfallwirtschaft

1998-12-31

Heat storage is essential for the reconciliation of heat supply and demand. The earth has already proved to be an excellent medium for storing large amounts of heat over longer periods of time, for instance during the cold and hot season. The efficiency of the storage is the better the lower storage losses are at high temperature levels. Unfortunately this can not be easily achieved. While thermal underground stores, which are widely used for cold storage, have proved to perform quite well at temperatures between 10 C - 40 C, it has been rather difficult to achieve similar results at higher temperatures up to 150 C as test and demonstration plants of the 1980s proved. This issue has again attracted so much interest that the IEA launched a project on high temperature underground storage in December 1998. (orig.) [Deutsch] Waermespeicherung ist von entscheidender Bedeutung, wenn es darum geht, ein Waermeangebot mit einer Waermenachfrage zeitlich zur Deckung zu bringen. Der Untergrund hat sich schon seit vielen Jahren als ein geeignetes Medium erwiesen, groessere Waermepumpen ueber laengere Zeitraeume wie etwa die kalten und warmen Jahreszeiten zu speichern. Die Effizienz eines solchen Speichers steigt mit der Hoehe des erreichten Temperaturniveaus und mit sinkenden Speicherverlusten, was leider eher gegenlaeufige Erscheinungen sind. Waehrend thermische Untergrundspeicher im Temperaturbereich von 10-40 C inzwischen erfolgreich demonstriert wurden und vor allem zur Kaeltespeicherung auch bereits vielfach eingesetzt werden, haben hoehere Temperaturen bis etwa 150 C in den Versuchs- und Demonstrationsanlagen der 80er Jahre vielfaeltige Probleme bereitet. Im Gefolge eines erneuten Interesses an unterirdischer thermischer Energiespeicherung wurde im Dezember 1997 ein Vorhaben des IEA Energiespeicherprogramms zu Untergrund-Waermespeichern hoeherer Temperatur eingerichtet. (orig.)

New Methods in Non-Perturbative QCD

Energy Technology Data Exchange (ETDEWEB)

Unsal, Mithat [North Carolina State Univ., Raleigh, NC (United States)

2017-01-31

In this work, we investigate the properties of quantum chromodynamics (QCD), by using newly developing mathematics and physics formalisms. Almost all of the mass in the visible universe emerges from a quantum chromodynamics (QCD), which has a completely negligible microscopic mass content. An intimately related issue in QCD is the quark confinement problem. Answers to non-perturbative questions in QCD remained largely elusive despite much effort over the years. It is also believed that the usual perturbation theory is inadequate to address these kinds of problems. Perturbation theory gives a divergent asymptotic series (even when the theory is properly renormalized), and there are non-perturbative phenomena which never appear at any order in perturbation theory. Recently, a fascinating bridge between perturbation theory and non-perturbative effects has been found: a formalism called resurgence theory in mathematics tells us that perturbative data and non-perturbative data are intimately related. Translating this to the language of quantum field theory, it turns out that non-perturbative information is present in a coded form in perturbation theory and it can be decoded. We take advantage of this feature, which is particularly useful to understand some unresolved mysteries of QCD from first principles. In particular, we use: a) Circle compactifications which provide a semi-classical window to study confinement and mass gap problems, and calculable prototypes of the deconfinement phase transition; b) Resurgence theory and transseries which provide a unified framework for perturbative and non-perturbative expansion; c) Analytic continuation of path integrals and Lefschetz thimbles which may be useful to address sign problem in QCD at finite density.

Quark model and QCD

International Nuclear Information System (INIS)

Anisovich, V.V.

1989-06-01

Using the language of the quarks and gluons for description of the soft hadron physics it is necessary to take into account two characteristic phenomena which prevent one from usage of QCD Lagrangian in the straightforward way, chiral symmetry breaking, and confinement of colour particles. The topics discussed in this context are: QCD in the domain of soft processes, phenomenological Lagrangian for soft processes and exotic mesons, spectroscopy of low-lying hadrons (mesons, baryons and mesons with heavy quarks - c,b -), confinement forces, spectral integration over quark masses. (author) 3 refs.; 19 figs.; 3 tabs

QCD

CERN Multimedia

1999-01-01

Basic Properties of QCD: the Lagrangian, the running coupling, asymptotic freedom and colour confinement. Examples of perturbative calculations in electron- positron physics (total cross sections and event) Parton branching approach will be used to derive the evolution equations for hadron structure functions Comarison with data on deep inelastic scattering and jet production will be for hadron structure functions and jet fragmentation functions

Testing QCD with Hypothetical Tau Leptons

Energy Technology Data Exchange (ETDEWEB)

Brodsky, Stanley J.

1998-10-21

We construct new tests of perturbative QCD by considering a hypothetical {tau} lepton of arbitrary mass, which decays hadronically through the electromagnetic current. We can explicitly compute its hadronic width ratio directly as an integral over the e{sup +}e{sup -} annihilation cross section ratio, R{sub e{sup +}e{sup -}}. Furthermore, we can design a set of commensurate scale relations and perturbative QCD tests by varying the weight function away from the form associated with the V-A decay of the physical {tau}. This method allows the wide range of the R{sub e{sup +}e{sup -}} data to be used as a probe of perturbative QCD.

Quantum properties of QCD string fragmentation

Directory of Open Access Journals (Sweden)

Todorova-Nová Šárka

2016-01-01

Full Text Available A simple quantization concept for a 3-dim QCD string is used to derive properties of QCD flux tube from the mass spectrum of light mesons and to predict observable quantum effects in correlations between adjacent hadrons. The quantized fragmentation model is presented and compared with experimental observations.

Towards understanding Regge trajectories in holographic QCD

International Nuclear Information System (INIS)

Cata, Oscar

2007-01-01

We reassess a work done by Migdal on the spectrum of low-energy vector mesons in QCD in the light of the anti-de Sitter (AdS)-QCD correspondence. Recently, a tantalizing parallelism was suggested between Migdal's work and a family of holographic duals of QCD. Despite the intriguing similarities, both approaches face a major drawback: the spectrum is in conflict with well-tested Regge scaling. However, it has recently been shown that holographic duals can be modified to accommodate Regge behavior. Therefore, it is interesting to understand whether Regge behavior can also be achieved in Migdal's approach. In this paper we investigate this issue. We find that Migdal's approach, which is based on a modified Pade approximant, is closely related to the issue of quark-hadron duality breakdown in QCD

Mass and scattering length inequalities in QCD and QCD-like theories

International Nuclear Information System (INIS)

Nussinov, S.; Pennsylvania Univ., Philadelphia; Sathiapalan, B.

1985-01-01

Some observations about mass scattering length inequalities in QCD-like theories are presented. It is shown that the Weingarten mass inequality can be used to argue that global vector symmetries are unbroken in such theories. For QCD, in the limit Nsub(c)->infinite, it is shown that Msub(baryon)>=1/2Nsub(c)Msub(meson), provided there are at least Nsub(c) degenerate flavors of quarks. It is argued that when there are not bound states in a scattering channel, the mass inequalities can be used to derive inequalities beteen scattering lengths. Some rigorous inequalities for two and higher point functions for operators bilinear in currents are derived, and used to extract inequalities between quartic coupling constants. (orig.)

Studies on the hazard potential of noble metal emissions from catalytic converters; Untersuchungen zur Frage des Gefaehrdungspotentials von katalysatorbuertigen Edelmetallemissionen (VPT 05)

Energy Technology Data Exchange (ETDEWEB)

Artelt, S [Fraunhofer-Institut fuer Toxikologie und Aerosolforschung, Hannover (Germany)

1998-12-31

Plants were exposed to engine exhaust fumes from engine test stands in order to estimate the probable level of platinum deposition near roads. [Deutsch] Zur Abschaetzung der zu erwarteten Platindeposition in der Naehe von Strassen wurden Pflanzen mit Motorabgasen, die aus Motorstandexperimenten gewonnen wurden, beaufschlagt. (orig.)

Studies on the hazard potential of noble metal emissions from catalytic converters; Untersuchungen zur Frage des Gefaehrdungspotentials von katalysatorbuertigen Edelmetallemissionen (VPT 05)

Energy Technology Data Exchange (ETDEWEB)

Artelt, S. [Fraunhofer-Institut fuer Toxikologie und Aerosolforschung, Hannover (Germany)

1997-12-31

Plants were exposed to engine exhaust fumes from engine test stands in order to estimate the probable level of platinum deposition near roads. [Deutsch] Zur Abschaetzung der zu erwarteten Platindeposition in der Naehe von Strassen wurden Pflanzen mit Motorabgasen, die aus Motorstandexperimenten gewonnen wurden, beaufschlagt. (orig.)

QCD are we ready for the LHC?

CERN Multimedia

CERN. Geneva

2006-01-01

The LHC energy regime poses a serious challenge to our capability of predicting QCD reactions to the level of accuracy necessary for a successful programme of searches for physics beyond the Standard Model. In these lectures, I'll introduce basic concepts in QCD, and present techniques based on perturbation theory, such as fixed-order and resummed computations, and Monte Carlo simulations. I'll discuss applications of these techniques to hadron-hadron processes, concentrating on recent trends in perturbative QCD aimed at improving our understanding of LHC phenomenology.

The generalized scheme-independent Crewther relation in QCD

Science.gov (United States)

Shen, Jian-Ming; Wu, Xing-Gang; Ma, Yang; Brodsky, Stanley J.

2017-07-01

The Principle of Maximal Conformality (PMC) provides a systematic way to set the renormalization scales order-by-order for any perturbative QCD calculable processes. The resulting predictions are independent of the choice of renormalization scheme, a requirement of renormalization group invariance. The Crewther relation, which was originally derived as a consequence of conformally invariant field theory, provides a remarkable connection between two observables when the β function vanishes: one can show that the product of the Bjorken sum rule for spin-dependent deep inelastic lepton-nucleon scattering times the Adler function, defined from the cross section for electron-positron annihilation into hadrons, has no pQCD radiative corrections. The ;Generalized Crewther Relation; relates these two observables for physical QCD with nonzero β function; specifically, it connects the non-singlet Adler function (Dns) to the Bjorken sum rule coefficient for polarized deep-inelastic electron scattering (CBjp) at leading twist. A scheme-dependent ΔCSB-term appears in the analysis in order to compensate for the conformal symmetry breaking (CSB) terms from perturbative QCD. In conventional analyses, this normally leads to unphysical dependence in both the choice of the renormalization scheme and the choice of the initial scale at any finite order. However, by applying PMC scale-setting, we can fix the scales of the QCD coupling unambiguously at every order of pQCD. The result is that both Dns and the inverse coefficient CBjp-1 have identical pQCD coefficients, which also exactly match the coefficients of the corresponding conformal theory. Thus one obtains a new generalized Crewther relation for QCD which connects two effective charges, αˆd (Q) =∑i≥1 αˆg1 i (Qi), at their respective physical scales. This identity is independent of the choice of the renormalization scheme at any finite order, and the dependence on the choice of the initial scale is negligible. Similar

Fractal structures and intermittency in QCD

International Nuclear Information System (INIS)

Gustafson, Goesta.

1990-04-01

New results are presented for fractal structures and intermittency in QCD parton showers. A geometrical interpretation of the anomalous dimension in QCD is given. It is shown that model predications for factorial moments in the PEP-PETRA energy range are increased. if the properties of directly produced pions are more carefully taken into account

ADS/CFT and QCD

International Nuclear Information System (INIS)

Brodsky, Stanley J.; de Teramond, Guy F.

2007-01-01

The AdS/CFT correspondence between string theory in AdS space and conformal .eld theories in physical spacetime leads to an analytic, semi-classical model for strongly-coupled QCD which has scale invariance and dimensional counting at short distances and color confinement at large distances. Although QCD is not conformally invariant, one can nevertheless use the mathematical representation of the conformal group in five-dimensional anti-de Sitter space to construct a first approximation to the theory. The AdS/CFT correspondence also provides insights into the inherently non-perturbative aspects of QCD, such as the orbital and radial spectra of hadrons and the form of hadronic wavefunctions. In particular, we show that there is an exact correspondence between the fifth-dimensional coordinate of AdS space z and a specific impact variable ζ which measures the separation of the quark and gluonic constituents within the hadron in ordinary space-time. This connection allows one to compute the analytic form of the frame-independent light-front wavefunctions, the fundamental entities which encode hadron properties and allow the computation of decay constants, form factors, and other exclusive scattering amplitudes. New relativistic lightfront equations in ordinary space-time are found which reproduce the results obtained using the 5-dimensional theory. The effective light-front equations possess remarkable algebraic structures and integrability properties. Since they are complete and orthonormal, the AdS/CFT model wavefunctions can also be used as a basis for the diagonalization of the full light-front QCD Hamiltonian, thus systematically improving the AdS/CFT approximation

Death to perturbative QCD in exclusive processes?

Energy Technology Data Exchange (ETDEWEB)

Eckardt, R.; Hansper, J.; Gari, M.F. [Institut fuer Theoretische Physik, Bochum (Germany)

1994-04-01

The authors discuss the question of whether perturbative QCD is applicable in calculations of exclusive processes at available momentum transfers. They show that the currently used method of determining hadronic quark distribution amplitudes from QCD sum rules yields wave functions which are completely undetermined because the polynomial expansion diverges. Because of the indeterminacy of the wave functions no statement can be made at present as to whether perturbative QCD is valid. The authors emphasize the necessity of a rigorous discussion of the subject and the importance of experimental data in the range of interest.

Phases of Holographic QCD

International Nuclear Information System (INIS)

Lippert, Matthew

2009-01-01

We investigated the Sakai-Sugimoto model of large N QCD at nonzero temperature and baryon chemical potential and in the presence of background electric and magnetic fields. We studied the holographic representation of baryons and the deconfinement, chiral-symmetry breaking, and nuclear matter phase transitions. In a background electric field, chiral-symmetry breaking corresponds to an insulator-conductor transition. A magnetic field both catalyzes chiral-symmetry breaking and generates, in the confined phase, a pseudo-scalar gradient or, in the deconfined phase, an axial current. The resulting phase diagram is in qualitative agreement with studies of hot, dense QCD.

Volume independence in large Nc QCD-like gauge theories

International Nuclear Information System (INIS)

Kovtun, Pavel; Uensal, Mithat; Yaffe, Laurence G.

2007-01-01

Volume independence in large N c gauge theories may be viewed as a generalized orbifold equivalence. The reduction to zero volume (or Eguchi-Kawai reduction) is a special case of this equivalence. So is temperature independence in confining phases. A natural generalization concerns volume independence in 'theory space' of quiver gauge theories. In pure Yang-Mills theory, the failure of volume independence for sufficiently small volumes (at weak coupling) due to spontaneous breaking of center symmetry, together with its validity above a critical size, nicely illustrate the symmetry realization conditions which are both necessary and sufficient for large N c orbifold equivalence. The existence of a minimal size below which volume independence fails also applies to Yang-Mills theory with antisymmetric representation fermions [QCD(AS)]. However, in Yang-Mills theory with adjoint representation fermions [QCD(Adj)], endowed with periodic boundary conditions, volume independence remains valid down to arbitrarily small size. In sufficiently large volumes, QCD(Adj) and QCD(AS) have a large N c ''orientifold'' equivalence, provided charge conjugation symmetry is unbroken in the latter theory. Therefore, via a combined orbifold-orientifold mapping, a well-defined large N c equivalence exists between QCD(AS) in large, or infinite, volume and QCD(Adj) in arbitrarily small volume. Since asymptotically free gauge theories, such as QCD(Adj), are much easier to study (analytically or numerically) in small volume, this equivalence should allow greater understanding of large N c QCD in infinite volume

Tests of hard and soft QCD with $e^{+}e^{-}$ Annihilation Data

CERN Document Server

Kluth, S

2002-01-01

Experimental tests of QCD predictions for event shape distributions combining contributions from hard and soft processes are discussed. The hard processes are predicted by perturbative QCD calculations. The soft processes cannot be calculated directly using perturbative QCD, they are treated by a power correction model based on the analysis of infrared renormalons. Furthermore, an analysis of the gauge structure of QCD is presented using fits of the colour factors within the same combined QCD predictions.

Multi-Quarks and Two-Baryon Interaction in Lattice QCD

International Nuclear Information System (INIS)

Okiharu, F.; Suganuma, H.; Takahashi, T. T.; Doi, T.

2006-01-01

We study multi-quark (3Q,4Q,5Q) systems in lattice QCD. We perform the detailed studies of multi-quark potentials in lattice QCD to clarify the inter-quark interaction in multi-quark systems. We find that all the multi-quark potentials are well described by the OGE Coulomb plus multi-Y-type linear potential, i.e., the multi-Y Ansatz. For multi-quark systems, we observe lattice QCD evidences of 'flip-flop', i.e., flux-tube recombination. These lattice QCD studies give an important bridge between elementary particle physics and nuclear physics

Lattice QCD. A critical status report

Energy Technology Data Exchange (ETDEWEB)

Jansen, Karl

2008-10-15

The substantial progress that has been achieved in lattice QCD in the last years is pointed out. I compare the simulation cost and systematic effects of several lattice QCD formulations and discuss a number of topics such as lattice spacing scaling, applications of chiral perturbation theory, non-perturbative renormalization and finite volume effects. Additionally, the importance of demonstrating universality is emphasized. (orig.)

Lattice QCD. A critical status report

International Nuclear Information System (INIS)

Jansen, Karl

2008-10-01

The substantial progress that has been achieved in lattice QCD in the last years is pointed out. I compare the simulation cost and systematic effects of several lattice QCD formulations and discuss a number of topics such as lattice spacing scaling, applications of chiral perturbation theory, non-perturbative renormalization and finite volume effects. Additionally, the importance of demonstrating universality is emphasized. (orig.)

Solving QCD via multi-Regge theory

International Nuclear Information System (INIS)

White, A. R.

1998-01-01

A high-energy, transverse momentum cut-off, solution of QCD is outlined. Regge pole and single gluon properties of the pomeron are directly related to the confinement and chiral symmetry breaking properties of the hadron spectrum. This solution, which corresponds to a supercritical phase of Reggeon Field Theory, may only be applicable to QCD with a very special quark content

QCD on the Cell Broadband Engine

Energy Technology Data Exchange (ETDEWEB)

Meyer, Nils [Department of Physics, University of Regensburg, 93040 Regensburg (Germany)

2008-07-01

We evaluate IBM's Enhanced Cell Broadband Engine (BE) as a possible building block of a new generation of lattice QCD machines. The Enhanced Cell BE will provide full support of double precision floating-point arithmetics, including IEEE-compliant rounding. We have developed a performance model and applied it to relevant lattice QCD kernels. The performance estimates are supported by micro- and application-benchmarks that have been obtained on currently available Cell BE-based computers, such as IBM QS20 blades and PlayStation 3. The results are encouraging and show that this processor is an interesting option for lattice QCD applications. For a massively parallel machine on the basis of the Cell BE, an application-optimized network needs to be developed.

QCD on the Cell Broadband Engine

Energy Technology Data Exchange (ETDEWEB)

Meyer, Nils [Department of Physics, University of Regensburg, 93040 Regensburg (Germany)

2008-07-01

We evaluate IBM's Enhanced Cell Broadband Engine (BE) as a possible building block of a new generation of lattice QCD machines. The Enhanced Cell BE will provide full support of double precision floating-point arithmetics, including IEEE-compliant rounding. We have developed a performance model and applied it to relevant lattice QCD kernels. The performance estimates are supported by micro- and application-benchmarks that have been obtained on currently available Cell BE-based computers, such as IBM QS20 blades and PlayStation 3. The results are encouraging and show that this processor is an interesting option for lattice QCD applications. For a massively parallel machine on the basis of the Cell BE, an application-optimized network needs to be developed.

QCD on the BlueGene/L Supercomputer

International Nuclear Information System (INIS)

Bhanot, G.; Chen, D.; Gara, A.; Sexton, J.; Vranas, P.

2005-01-01

In June 2004 QCD was simulated for the first time at sustained speed exceeding 1 TeraFlops in the BlueGene/L supercomputer at the IBM T.J. Watson Research Lab. The implementation and performance of QCD in the BlueGene/L is presented

QCD on the BlueGene/L Supercomputer

Science.gov (United States)

Bhanot, G.; Chen, D.; Gara, A.; Sexton, J.; Vranas, P.

2005-03-01

In June 2004 QCD was simulated for the first time at sustained speed exceeding 1 TeraFlops in the BlueGene/L supercomputer at the IBM T.J. Watson Research Lab. The implementation and performance of QCD in the BlueGene/L is presented.

How is the charmonium splitting in QCD

International Nuclear Information System (INIS)

Bertlmann, R.A.

1981-06-01

Using the SVZ moment procedure to predict resonance masses within QCD the author has calculated exponential moments as a limit of the QCD formulae given by Reinders, Rubinstein and Yazaki. Applied to charmonium their results (besides 3 P 0 ) are reproduced very well. (Auth.)

Novel QCD Phenomena at Electron-Proton Colliders

International Nuclear Information System (INIS)

Brodsky, S

2008-01-01

I discuss several novel phenomenological features of QCD which are observable in deep inelastic lepton-nucleon and lepton-nucleus scattering. Initial- and final-state interactions from gluon exchange, normally neglected in the parton model, have a profound effect on QCD hard-scattering reactions, leading to leading-twist single-spin asymmetries, the diffractive contribution to deep inelastic scattering, and the breakdown of the pQCD Lam-Tung relation in Drell-Yan reactions. Leading-twist diffractive processes in turn lead to nuclear shadowing and non-universal antishadowing--physics not incorporated in the light-front wavefunctions of the nucleus computed in isolation

The QCD Critical Point and Related Observables

Energy Technology Data Exchange (ETDEWEB)

Nahrgang, Marlene

2016-12-15

The search for the critical point of QCD in heavy-ion collision experiments has sparked enormous interest with the completion of phase I of the RHIC beam energy scan. Here, I review the basics of the thermodynamics of the QCD phase transition and its implications for experimental multiplicity fluctuations in heavy-ion collisions. Several sources of noncritical fluctuations impact the observables and need to be understood in addition to the critical phenomena. Recent progress has been made in dynamical modeling of critical fluctuations, which ultimately is indispensable to understand potential signals of the QCD critical point in heavy-ion collision.

Recent QCD results from CDF

International Nuclear Information System (INIS)

Yun, J.C.

1990-01-01

In this paper we report recent QCD analysis with the new data taken from CDF detector. CDF recorded an integrated luminosity of 4.4 nb -1 during the 1988--1989 run at center of mass system (CMS) energy of 1.8 TeV. The major topics of this report are inclusive jet, dijet, trijet and direct photon analysis. These measurements are compared of QCD predictions. For the inclusive jet an dijet analysis, tests of quark compositeness are emphasized. 11 refs., 6 figs

Selected challenges in low-energy QCD and hadron physics

Energy Technology Data Exchange (ETDEWEB)

Weise, Wolfram [Physik-Department, Technische Universitaet Muenchen, D-85747 Garching (Germany)

2009-11-15

This presentation briefly addresses three basic issues of low-energy QCD: first, whether the Nambu-Goldstone scenario of spontaneous chiral symmetry breaking is well established; secondly, whether there is a dynamical entanglement of the chiral and deconfinement crossover transitions in QCD; and thirdly, what is the status of knowledge about the phase diagram of QCD at low temperature and non-zero baryon density. These three topics were injected as key words into a panel discussion at the Schladming school on Challenges in QCD. The following exposition reflects the style and character of the discussions, with no claim of completeness.

Non-perturbative Aspects of QCD and Parameterized Quark Propagator

Institute of Scientific and Technical Information of China (English)

HAN Ding-An; ZHOU Li-Juan; ZENG Ya-Guang; GU Yun-Ting; CAO Hui; MA Wei-Xing; MENG Cheng-Ju; PAN Ji-Huan

2008-01-01

Based on the Global Color Symmetry Model, the non-perturbative QCD vacuum is investigated in theparameterized fully dressed quark propagator. Our theoretical predictions for various quantities characterized the QCD vacuum are in agreement with those predicted by many other phenomenological QCD inspired models. The successful predictions clearly indicate the extensive validity of our parameterized quark propagator used here. A detailed discussion on the arbitrariness in determining the integration cut-off parameter of# in calculating QCD vacuum condensates and a good method, which avoided the dependence of calculating results on the cut-off parameter is also strongly recommended to readers.

Nonperturbative QCD corrections to electroweak observables

Energy Technology Data Exchange (ETDEWEB)

Dru B Renner, Xu Feng, Karl Jansen, Marcus Petschlies

2011-12-01

Nonperturbative QCD corrections are important to many low-energy electroweak observables, for example the muon magnetic moment. However, hadronic corrections also play a significant role at much higher energies due to their impact on the running of standard model parameters, such as the electromagnetic coupling. Currently, these hadronic contributions are accounted for by a combination of experimental measurements and phenomenological modeling but ideally should be calculated from first principles. Recent developments indicate that many of the most important hadronic corrections may be feasibly calculated using lattice QCD methods. To illustrate this, we will examine the lattice computation of the leading-order QCD corrections to the muon magnetic moment, paying particular attention to a recently developed method but also reviewing the results from other calculations. We will then continue with several examples that demonstrate the potential impact of the new approach: the leading-order corrections to the electron and tau magnetic moments, the running of the electromagnetic coupling, and a class of the next-to-leading-order corrections for the muon magnetic moment. Along the way, we will mention applications to the Adler function, the determination of the strong coupling constant and QCD corrections to muonic-hydrogen.

Low-energy QCD and ultraviolet renormalons

International Nuclear Information System (INIS)

Peris, S.

1997-01-01

We discuss the contribution of ultraviolet (UV) renormalons in QCD to two-point functions of quark current operators. This explicitly includes effects due to the exchange of one renormalon chain as well as two chains. It is shown that, when the external Euclidean momentum of the two-point functions becomes smaller than the scale Λ L associated with the Landau singularity of the QCD one-loop running coupling constant, the positions of the UV renormalons in the Borel plane become true singularities in the integration range of the Borel transform. This introduces ambiguities in the evaluation of the corresponding two-point functions. The ambiguities associated with the leading UV renormalon singularity are of the same type as the contribution due to the inclusion of dimension d=6 local operators in a low-energy effective Lagrangian valid at scales smaller than Λ L . We then discuss the inclusion of an infinite number of renormalon chains and argue that the previous ambiguity hints at a plausible approximation scheme for low-energy QCD, resulting in an effective Lagrangian similar to the one of the extended Nambu-Jona-Lasinio (ENJL) model of QCD at large N c . (orig.)

Hard And Soft QCD Physics In ATLAS

Directory of Open Access Journals (Sweden)

Adomeit Stefanie

2014-04-01

Full Text Available Hard and soft QCD results using proton-proton collisions recorded with the ATLAS detector at the LHC are reported. Charged-particle distributions and forward-backward correlations have been studied in low-luminosity minimum bias data taken at centre-of-mass energies of √s = 0.9, 2.36 and 7 TeV. Recent measurements on underlying event characteristics using charged-particle jets are also presented. The results are tested against various phenomenological soft QCD models implemented in Monte-Carlo generators. A summary of hard QCD measurements involving high transverse momentum jets is also given. Inclusive jet and dijet cross-sections have been measured at a centre-of-mass energy of 7 TeV and are compared to expectations based on NLO pQCD calculations corrected for non-perturbative effects as well as to NLO Monte Carlo predictions. Recent studies exploiting jet substructure techniques to identify hadronic decays of boosted massive particles are reported.

Photon-photon inclusive scattering and perturbative QCD

International Nuclear Information System (INIS)

Maor, U.

1988-01-01

Perturbative QCD expectations and problems associated with the study of the photon structure function data are reviewed. An assessment is given for the viability and sensitivity of photon-photon scattering as a decisive tool for the determination of the QCD scale. Particular attention is given to the theoretical problems of singularity cancellations at x = 0 and threshold-associated difficulties at x = 1 and their implications on the actual data analysis. It is concluded that the experimental results, while not providing a decisive verification of QCD at small distances, do add to other independent experiments which are all consistent with the theory and suggest a reasonably well defined QCD scale parameter. The importance of the small Q 2 limit to photon-photon analysis is discussed and the data are examined in an attempt to identify and isolate the contributions of the hadronic and point-like sectors of the target photon. 21 refs., 7 figs. (author)

The Top Quark, QCD, And New Physics.

Science.gov (United States)

Dawson, S.

2002-06-01

The role of the top quark in completing the Standard Model quark sector is reviewed, along with a discussion of production, decay, and theoretical restrictions on the top quark properties. Particular attention is paid to the top quark as a laboratory for perturbative QCD. As examples of the relevance of QCD corrections in the top quark sector, the calculation of e{sup+}e{sup -}+ t{bar t} at next-to-leading-order QCD using the phase space slicing algorithm and the implications of a precision measurement of the top quark mass are discussed in detail. The associated production of a t{bar t} pair and a Higgs boson in either e{sup+}e{sup -} or hadronic collisions is presented at next-to-leading-order QCD and its importance for a measurement of the top quark Yulrawa coupling emphasized. Implications of the heavy top quark mass for model builders are briefly examined, with the minimal supersymmetric Standard Model and topcolor discussed as specific examples.

Recent QCD Studies at the Tevatron

Energy Technology Data Exchange (ETDEWEB)

Group, Robert Craig

2008-04-01

Since the beginning of Run II at the Fermilab Tevatron the QCD physics groups of the CDF and D0 experiments have worked to reach unprecedented levels of precision for many QCD observables. Thanks to the large dataset--over 3 fb{sup -1} of integrated luminosity recorded by each experiment--important new measurements have recently been made public and will be summarized in this paper.

The dual description of long-distance QCD (Dual QCD)

International Nuclear Information System (INIS)

Baker, M.

1990-01-01

We construct and solve a local field theory which describes in terms of dual variables a system having an A μ propagator behaving like M 2 /q 4 in the infrared and discuss how this theory can be used as a starting point for describing long-distance QCD. 3 refs

Threshold resummation and higher order effects in QCD

International Nuclear Information System (INIS)

Ringer, Felix Maximilian

2015-01-01

Quantum chromodynamics (QCD) is a quantum field theory that describes the strong interactions between quarks and gluons, the building blocks of all hadrons. Thanks to the experimental progress over the past decades, there has been an ever-growing need for QCD precision calculations for scattering processes involving hadrons. For processes at large momentum transfer, perturbative QCD offers a systematic approach for obtaining precise predictions. This approach relies on two key concepts: the asymptotic freedom of QCD and factorization. In a perturbative calculation at higher orders, the infrared cancellation between virtual and real emission diagrams generally leaves behind logarithmic contributions. In many observables relevant for hadronic scattering these logarithms are associated with a kinematic threshold and are hence known as ''threshold logarithms''. They become large when the available phase space for real gluon emission shrinks. In order to obtain a reliable prediction from QCD, the threshold logarithms need to be taken into account to all orders in the strong coupling constant, a procedure known as ''threshold resummation''. The main focus of my PhD thesis is on studies of QCD threshold resummation effects beyond the next-to-leading logarithmic order. Here we primarily consider the production of hadron pairs in hadronic collisions as an example. In addition, we also consider hadronic jet production, which is particularly interesting for the phenomenology at the LHC. For both processes, we fully take into account the non-trivial QCD color structure of the underlying partonic hard- scattering cross sections. We find that threshold resummation leads to sizable numerical effects in the kinematic regimes relevant for comparisons to experimental data.

Neutron star structure from QCD

CERN Document Server

Fraga, Eduardo S; Vuorinen, Aleksi

2016-01-01

In this review article, we argue that our current understanding of the thermodynamic properties of cold QCD matter, originating from first principles calculations at high and low densities, can be used to efficiently constrain the macroscopic properties of neutron stars. In particular, we demonstrate that combining state-of-the-art results from Chiral Effective Theory and perturbative QCD with the current bounds on neutron star masses, the Equation of State of neutron star matter can be obtained to an accuracy better than 30% at all densities.

The supercritical pomeron in QCD

International Nuclear Information System (INIS)

White, A. R.

1998-01-01

Deep-inelastic diffractive scaling violations have provided fundamental insight into the QCD pomeron, suggesting a single gluon inner structure rather than that of a perturbative two-gluon bound state. This talk outlines a derivation of a high-energy, transverse momentum cut-off, confining solution of QCD. The pomeron, in first approximation, is a single reggeized gluon plus a ''wee parton'' component that compensates for the color and particle properties of the gluon. This solution corresponds to a super-critical phase of Reggeon Field Theory

Archeology and evolution of QCD

CERN Document Server

De Rújula, A.

2017-01-01

These are excerpts from the closing talk at the "XIIth Conference on Quark Confinement and the Hadron Spectrum", which took place last Summer in Thessaloniki --an excellent place to enjoy an interest in archeology. A more complete personal view of the early days of QCD and the rest of the Standard Model is given in [1]. Here I discuss a few of the points which --to my judgement-- illustrate well the QCD evolution (in time), both from a scientific and a sociological point of view.

Lattice QCD at finite temperature with Wilson fermions

International Nuclear Information System (INIS)

Pinke, Christopher

2014-01-01

The subatomic world is governed by the strong interactions of quarks and gluons, described by Quantum Chromodynamics (QCD). Quarks experience confinement into colour-less objects, i.e. they can not be observed as free particles. Under extreme conditions such as high temperature or high density, this constraint softens and a transition to a phase where quarks and gluons are quasi-free particles (Quark-Gluon-Plasma) can occur. This environment resembles the conditions prevailing during the early stages of the universe shortly after the Big Bang. The phase diagram of QCD is under investigation in current and future collider experiments, for example at the Large Hadron Collider (LHC) or at the Facility for Antiproton and Ion Research (FAIR). Due to the strength of the strong interactions in the energy regime of interest, analytic methods can not be applied rigorously. The only tool to study QCD from first principles is given by simulations of its discretised version, Lattice QCD (LQCD). These simulations are in the high-performance computing area, hence, the numerical aspects of LQCD are a vital part in this field of research. In recent years, Graphic Processing Units (GPUs) have been incorporated in these simulations as they are a standard tool for general purpose calculations today. In the course of this thesis, the LQCD application CL 2 QCD has been developed, which allows for simulations on GPUs as well as on traditional CPUs, as it is based on OpenCL. CL 2 QCD constitutes the first application for Wilson type fermions in OpenCL. It provides excellent performance and has been applied in physics studies presented in this thesis. The investigation of the QCD phase diagram is hampered by the notorious sign-problem, which restricts current simulation algorithms to small values of the chemical potential. Theoretically, studying unphysical parameter ranges allows for constraints on the phase diagram. Of utmost importance is the clarification of the order of the finite

Perturbative QCD and electromagnetic form factors

International Nuclear Information System (INIS)

Carlson, C.E.; Gross, F.

1987-01-01

We calculate nucleon magnetic form factors using perturbative QCD for several distribution amplitudes including a general one given in terms of Appell polynomials. We find that the magnitude and sign of both nucleon magnetic form factors can be explained within perturbative QCD. The observed normalization of G/sub Mp/ requires that the distribution amplitude be broader than its superhigh momentum transfer limit, and the G/sub Mn//G/sub Mp/ data may require the distribution amplitude to be asymmetric, in accord with distribution amplitudes derived from QCD sum rules. Some speculation as to how an asymmetric distribution amplitude can come about is offered. Finally, we show that the soft contributions corresponding to the particular distribution amplitudes we use need not be bigger than the data. 16 refs., 6 figs

Calculating hadronic properties in strong QCD

International Nuclear Information System (INIS)

Pennington, M.R.

1996-01-01

This talk gives a brief review of the progress that has been made in calculating the properties of hadrons in strong QCD. In keeping with this meeting I will concentrate on those properties that can be studied with electromagnetic probes. Though perturbative QCD is highly successful, it only applies in a limited kinematic regime, where hard scattering occur, and the quarks move in the interaction region as if they are free, pointlike objects. However, the bulk of strong interactions are governed by the long distance regime, where the strong interaction is strong. It is this regime of length scales of the order of a Fermi, that determines the spectrum of light hadrons and their properties. The calculation of these properties requires an understanding of non-perturbative QCD, of confinement and chiral symmetry breaking. (author)

Small-x physics in perturbative QCD

International Nuclear Information System (INIS)

Lipatov, L.N.

1996-07-01

We review the parton model and the Regge approach to the QCD description of the deep-inelastic ep scattering at the small Bjorken variable x and demonstrate their relation with the DGLAP and BFKL evolution equations. It is shown, that in the leading logarithmic approximation the gluon is reggeized and the pomeron is a compound state of two reggeized gluons. The conformal invariance of the BFKL pomeron in the impact parameter space is used to investigate the scattering amplitudes at high energies and fixed momentum transfers. The remarkable properties of the Schroedinger equation for compound states of an arbitrary number of reggeized gluons in the multi-colour QCD are reviewed. The gauge-invariant effective action describing the gluon-Reggeon interactions is constructed. The known next-to-leading corrections to the QCD pomeron are discussed. (orig.)

The effective QCD theory at low energy; La theorie effective de QCD a basse energie

Energy Technology Data Exchange (ETDEWEB)

Knecht, M. [Paris-11 Univ., 91 - Orsay (France). Inst. de Physique Nucleaire

1995-12-31

Quantum chromodynamics is studied here in the range of low energies. The Chiral perturbation theory is presented, this theory is based on a thorough study of QCD symmetry, of general field theory principles and of S-matrices. Ward identities are defined within the scope of current algebras and by using functional method. Their consequences on Chiral structure of QCD emptiness and on strong interaction at low energies are studied. The pion-pion diffusion at low energies is treated as an example. (A.C.) 70 refs.

A new perturbative approach to QCD

International Nuclear Information System (INIS)

Pervushin, V.N.; Kallies, W.; Sarikov, N.A.

1988-01-01

For the description of bound states in QED and QCD the physical perturbation theory on the spatial components of the vector over the exact solution, defined by the time one, is proposed. It is shown this perturbation theory in QCD can be redefined so that it reproduces the main elements of hadron physics: confinement, spectroscopy of light and heavy quarkonia, dual-resonance amplitudes, chiral Lagrangians and the parton model

Lattice and Phase Diagram in QCD

International Nuclear Information System (INIS)

Lombardo, Maria Paola

2008-01-01

Model calculations have produced a number of very interesting expectations for the QCD Phase Diagram, and the task of a lattice calculations is to put these studies on a quantitative grounds. I will give an overview of the current status of the lattice analysis of the QCD phase diagram, from the quantitative results of mature calculations at zero and small baryochemical potential, to the exploratory studies of the colder, denser phase.

Self-consistent areas law in QCD

International Nuclear Information System (INIS)

Makeenko, Yu.M.; Migdal, A.A.

1980-01-01

The problem of obtaining the self-consistent areas law in quantum chromodynamics (QCD) is considered from the point of view of the quark confinement. The exact equation for the loop average in multicolor QCD is reduced to a bootstrap form. Its iterations yield new manifestly gauge invariant perturbation theory in the loop space, reproducing asymptotic freedom. For large loops, the areas law apprears to be a self-consistent solution

Search for the QCD ground state

International Nuclear Information System (INIS)

Reuter, M.; Wetterich, C.

1994-05-01

Within the Euclidean effective action approach we propose criteria for the ground state of QCD. Despite a nonvanishing field strength the ground state should be invariant with respect to modified Poincare transformations consisting of a combination of translations and rotations with suitable gauge transformations. We have found candidate states for QCD with four or more colours. The formation of gluon condensates shows similarities with the Higgs phenomenon. (orig.)

Nonperturbation aspects of QCD. Monte Carlo and optimization

International Nuclear Information System (INIS)

Brezin, E.; Morel, A.; Marinari, E.; Couchot, F.; Narison, S.; Richard, J.M.; Blaizot, J.P.; Souillard, B.

1986-01-01

Phase transitions; lattice QCD; numerical simulation of lattice gauge theories; experimental research on gluonic mesons; QCD-duality sum rules; the bag model, potentials, and hadron spectra; and efficient Lagrangian functions and the Skyrme model are introduced [fr

Quark mass effects in QCD

International Nuclear Information System (INIS)

Shirkov, D.V.

1982-01-01

In this paper recent studies of invariant QCD coupling anti asub(s)(Qsup(2)) in the 2-loop approximation with account of fermionic mass effects are summarized. The main results are: An explicit expression for anti asub(s)(Qsup(2)) in the 2-loop approximation with accurate account of heavy quark masses. A quantitative analysis on the basis of the above-mentioned expression for anti asub(s)(Qsup(2)) of the energy dependence of the scale QCD parameter ν and the conclusion about its inadequacy in the modern energy range

Hadron scattering, resonances, and QCD

Science.gov (United States)

Briceño, R. A.

2016-11-01

The non-perturbative nature of quantum chromodynamics (QCD) has historically left a gap in our understanding of the connection between the fundamental theory of the strong interactions and the rich structure of experimentally observed phenomena. For the simplest properties of stable hadrons, this is now circumvented with the use of lattice QCD (LQCD). In this talk I discuss a path towards a rigorous determination of few-hadron observables from LQCD. I illustrate the power of the methodology by presenting recently determined scattering amplitudes in the light-meson sector and their resonance content.

Integration of seismic reflection and geologically balanced profiles; Integration reflexionsseismischer und geologisch bilanzierter Profile

Energy Technology Data Exchange (ETDEWEB)

Lambrecht, A. [Trappe Erdoel Erdgas Consultant, Isernhagen (Germany)

1998-12-31

Geophysics and geology employ different kinds of techniques in order to preserve the underground structure. These techniques are based on different sets of data, i.e. seismic or geological data. A sensible combination of the two techniques should produce a better model of the ground structure. This study attempts to integrate geologically balanced profiles and seismic reflection data. A balanced geological profile can than be compared with seismic reflection data measured in the field. The geological model is then changed into a seismic model of the underground by means of seismic modeling. Synthetic modeling is based on the acquisition of available field data. The synthetic stack section or the synthetic migration image are then compared to the field data. Deviations between the two can be attributed to speed errors and the fact that balances will never give an unequivocal solution but always present a group of solutions. (orig. MSK). [Deutsch] In der Geophysik und der Geologie werden verschiedene Techniken verwendet, um die Untergrundstruktur zu erhalten. Diese Techniken basieren auf verschiedenen Datensaetzen, z.B. seismische und geologische Daten. Eine sinnvolle Kombination der Techniken sollte ein besseres Abbild des Untergrundes liefern. In dieser Studie wird ein Versuch unternommen geologisch bilanzierte Profile und reflexionsseismische Daten zu integrieren. Soll ein bilanziertes geologisches Profil mit im Feld gemessenen reflexionsseismischen Daten verglichen werden, dann wird das geologische Modell mit Hilfe der seismischen Modellierung in ein seismisches Abbild des Untergrundes verwandelt. Dabei wird die synthetische Modellierung entsprechend der Aquisition der vorliegenden Felddaten durchgefuehrt. Die synthetische Stapelsektion oder das synthetische Migrationsimage werden anschliessend mit den Felddaten verglichen. Abweichungen zwischen beobachteten und Felddaten haben ihre Ursachen sowohl in Geschwindigkeitsfehlern, als auch in der Tatsache, dass eine

The QCD Effective String

International Nuclear Information System (INIS)

Espriu, D.

2003-01-01

QCD can be described in a certain kinematical regime by an effective string theory. This string must couple to background chiral fields in a chirally invariant manner, thus taking into account the true chirally non-invariant QCD vacuum. By requiring conformal symmetry of the string and the unitarity constraint on chiral fields we reconstruct the equations of motion for the latter ones. These provide a consistent background for the propagation of the string. By further requiring locality of the effective action we recover the Lagrangian of non-linear sigma model of pion interactions. The prediction is unambiguous and parameter-free. The estimated chiral structural constants of Gasser and Leutwyler fit very well the phenomenological values. (author)

QCD and Light-Front Holography

Energy Technology Data Exchange (ETDEWEB)

Brodsky, Stanley J.; /SLAC /Southern Denmark U., CP3-Origins; de Teramond, Guy F.; /Costa Rica U.

2010-10-27

The soft-wall AdS/QCD model, modified by a positive-sign dilaton metric, leads to a remarkable one-parameter description of nonperturbative hadron dynamics. The model predicts a zero-mass pion for zero-mass quarks and a Regge spectrum of linear trajectories with the same slope in the leading orbital angular momentum L of hadrons and the radial quantum number N. Light-Front Holography maps the amplitudes which are functions of the fifth dimension variable z of anti-de Sitter space to a corresponding hadron theory quantized on the light front. The resulting Lorentz-invariant relativistic light-front wave equations are functions of an invariant impact variable {zeta} which measures the separation of the quark and gluonic constituents within the hadron at equal light-front time. The result is to a semi-classical frame-independent first approximation to the spectra and light-front wavefunctions of meson and baryon light-quark bound states, which in turn predict the behavior of the pion and nucleon form factors. The theory implements chiral symmetry in a novel way: the effects of chiral symmetry breaking increase as one goes toward large interquark separation, consistent with spectroscopic data, and the the hadron eigenstates generally have components with different orbital angular momentum; e.g., the proton eigenstate in AdS/QCD with massless quarks has L = 0 and L = 1 light-front Fock components with equal probability. The soft-wall model also predicts the form of the non-perturbative effective coupling {alpha}{sub s}{sup AdS} (Q) and its {beta}-function which agrees with the effective coupling {alpha}{sub g1} extracted from the Bjorken sum rule. The AdS/QCD model can be systematically improved by using its complete orthonormal solutions to diagonalize the full QCD light-front Hamiltonian or by applying the Lippmann-Schwinger method in order to systematically include the QCD interaction terms. A new perspective on quark and gluon condensates is also reviewed.

Disconnected Diagrams in Lattice QCD

Science.gov (United States)

Gambhir, Arjun Singh

In this work, we present state-of-the-art numerical methods and their applications for computing a particular class of observables using lattice quantum chromodynamics (Lattice QCD), a discretized version of the fundamental theory of quarks and gluons. These observables require calculating so called "disconnected diagrams" and are important for understanding many aspects of hadron structure, such as the strange content of the proton. We begin by introducing the reader to the key concepts of Lattice QCD and rigorously define the meaning of disconnected diagrams through an example of the Wick contractions of the nucleon. Subsequently, the calculation of observables requiring disconnected diagrams is posed as the computationally challenging problem of finding the trace of the inverse of an incredibly large, sparse matrix. This is followed by a brief primer of numerical sparse matrix techniques that overviews broadly used methods in Lattice QCD and builds the background for the novel algorithm presented in this work. We then introduce singular value deflation as a method to improve convergence of trace estimation and analyze its effects on matrices from a variety of fields, including chemical transport modeling, magnetohydrodynamics, and QCD. Finally, we apply this method to compute observables such as the strange axial charge of the proton and strange sigma terms in light nuclei. The work in this thesis is innovative for four reasons. First, we analyze the effects of deflation with a model that makes qualitative predictions about its effectiveness, taking only the singular value spectrum as input, and compare deflated variance with different types of trace estimator noise. Second, the synergy between probing methods and deflation is investigated both experimentally and theoretically. Third, we use the synergistic combination of deflation and a graph coloring algorithm known as hierarchical probing to conduct a lattice calculation of light disconnected matrix elements

Disconnected Diagrams in Lattice QCD

Energy Technology Data Exchange (ETDEWEB)

Gambhir, Arjun [College of William and Mary, Williamsburg, VA (United States)

2017-08-01

In this work, we present state-of-the-art numerical methods and their applications for computing a particular class of observables using lattice quantum chromodynamics (Lattice QCD), a discretized version of the fundamental theory of quarks and gluons. These observables require calculating so called \\disconnected diagrams" and are important for understanding many aspects of hadron structure, such as the strange content of the proton. We begin by introducing the reader to the key concepts of Lattice QCD and rigorously define the meaning of disconnected diagrams through an example of the Wick contractions of the nucleon. Subsequently, the calculation of observables requiring disconnected diagrams is posed as the computationally challenging problem of finding the trace of the inverse of an incredibly large, sparse matrix. This is followed by a brief primer of numerical sparse matrix techniques that overviews broadly used methods in Lattice QCD and builds the background for the novel algorithm presented in this work. We then introduce singular value deflation as a method to improve convergence of trace estimation and analyze its effects on matrices from a variety of fields, including chemical transport modeling, magnetohydrodynamics, and QCD. Finally, we apply this method to compute observables such as the strange axial charge of the proton and strange sigma terms in light nuclei. The work in this thesis is innovative for four reasons. First, we analyze the effects of deflation with a model that makes qualitative predictions about its effectiveness, taking only the singular value spectrum as input, and compare deflated variance with different types of trace estimator noise. Second, the synergy between probing methods and deflation is investigated both experimentally and theoretically. Third, we use the synergistic combination of deflation and a graph coloring algorithm known as hierarchical probing to conduct a lattice calculation of light disconnected matrix elements

Methodes non perturbatives en mecanique quantique et en theorie des champs quantiques

Science.gov (United States)

Jirari, Hamza

2001-10-01

Nous construisons un hamiltonien effectif à partir de l'intégrale de chemin via la méthode Monte-Carlo. Cet hamiltonien décrit les phénomènes physiques dans le domaine de basse énergie. Nous déterminons le spectre d'énergie et les fonctions d'ondes de plusieurs systèmes quantiques. Les résultats obtenus montrent que cette nouvelle approche Monte-Carlo hamiltonienne fonctionne. En mécanique quantique, nous suggérons une expression analytique de l'intégrale de chemin en introduisant une action quantique avec des paramètres renormalisés. Nous présentons des résultats numériques pour quelques potentiels locaux. Cette action quantique offre la possibilité de comparer l'évolution classique et quantique et permet de quantifier les instantons classiques et éventuellement le chaos classique. Nous investiguons la QCD sur un réseau bidimensionnel en utilisant une version améliorée des fermions de Wilson. Nous montrons que la théorie améliorée conduit à une réduction significative des erreurs dues à la valeur finie du pas du réseau. Nous calculons le condensat chiral et la masse de l'état lié quark-antiquark. Nous aboutissons à une bonne concordance entre nos résultats numériques et les résultats analytiques du modèle dans le continu.

Properties of the quark gluon plasma from lattice QCD

International Nuclear Information System (INIS)

Mages, Simon Wolfgang

2015-01-01

Quantum Chromodynamics (QCD) is the theory of the strong interaction, the theory of the interaction between the constituents of composite elementary particles (hadrons). In the low energy regime of the theory, standard methods of theoretical physics like perturbative approaches break down due to a large value of the coupling constant. However, this is the region of most interest, where the degrees of freedom of QCD, the color charges, form color-neutral composite elementary particles, like protons and neutrons. Also the transition to more energetic states of matter like the quark gluon plasma (QGP), is difficult to investigate with perturbative approaches. A QGP is a state of strongly interacting matter, which existed shortly after the Big Bang and can be created with heavy ion collisions for example at the LHC at CERN. In a QGP the color charges of QCD are deconfined. This thesis explores ways how to use the non-perturbative approach of lattice QCD to determine properties of the QGP. It focuses mostly on observables which are derived from the energy momentum tensor, like two point correlation functions. In principle these contain information on low energy properties of the QGP like the shear and bulk viscosity and other transport coefficients. The thesis describes the lattice QCD simulations which are necessary to measure the correlation functions and proposes new methods to extract these low energy properties. The thesis also tries to make contact to another non-perturbative approach which is Improved Holographic QCD. The aim of this approach is to use the Anti-de Sitter/Conformal Field Theory (AdS/CFT) correspondence to make statements about QCD with calculations of a five dimensional theory of gravity. This thesis contributes to that work by constraining the parameters of the model action by comparing the predictions with those of measurements with lattice QCD.

Two-color lattice QCD with staggered quarks

Energy Technology Data Exchange (ETDEWEB)

Scheffler, David

2015-07-20

The study of quantum chromodynamics (QCD) at finite temperature and density provides important contributions to the understanding of strong-interaction matter as it is present e.g. in nuclear matter and in neutron stars or as produced in heavy-ion collision experiments. Lattice QCD is a non-perturbative approach, where equations of motion for quarks and gluons are discretized on a finite space-time lattice. The method successfully describes the behavior of QCD in the vacuum and at finite temperature, however it cannot be applied to finite baryon density due to the fermion sign problem. Various QCD-like theories, that offer to draw conclusions about QCD, allow simulations also at finite densities. In this work we investigate two-color QCD as a popular example of a QCD-like theory free from the sign problem with methods from lattice gauge theory. For the generation of gauge configurations with two dynamical quark flavors in the staggered formalism with the ''rooting trick'' we apply the Rational Hybrid Monte Carlo (RHMC) algorithm. We carry out essential preparatory work for future simulations at finite density. As a start, we concentrate on the calculation of the effective potential for the Polyakov loop, which is an order parameter for the confinement-deconfinement transition, in dependence of the temperature and quark mass. It serves as an important input for effective models of QCD. We obtain the effective potential via the histogram method from local distributions of the Polyakov loop. To study the influence of dynamical quarks on gluonic observables, the simulations are performed with large quark masses and are compared to calculations in the pure gauge theory. In the second part of the thesis we examine aspects of the chiral phase transition along the temperature axis. The symmetry group of chiral symmetry in two-color QCD is enlarged to SU(2N{sub f}). Discretized two-color QCD in the staggered formalism exhibits a chiral symmetry breaking

Nonperturbative QCD corrections to electroweak observables

Energy Technology Data Exchange (ETDEWEB)

Renner, Dru B. [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); Feng, Xu [High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki (Japan); Jansen, Karl [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany); Petschlies, Marcus [The Cyprus Institute, Nicosia (Cyprus)

2012-06-15

Nonperturbative QCD corrections are important to many low-energy electroweak observables, for example the muon magnetic moment. However, hadronic corrections also play a significant role at much higher energies due to their impact on the running of standard model parameters, such as the electromagnetic coupling. Currently, these hadronic contributions are accounted for by a combination of experimental measurements, effective field theory techniques and phenomenological modeling but ideally should be calculated from first principles. Recent developments indicate that many of the most important hadronic corrections may be feasibly calculated using lattice QCD methods. To illustrate this, we examine the lattice computation of the leading-order QCD corrections to the muon magnetic moment, paying particular attention to a recently developed method but also reviewing the results from other calculations. We then continue with several examples that demonstrate the potential impact of the new approach: the leading-order corrections to the electron and tau magnetic moments, the running of the electromagnetic coupling, and a class of the next-to-leading-order corrections for the muon magnetic moment. Along the way, we mention applications to the Adler function, which can be used to determine the strong coupling constant, and QCD corrections to muonic-hydrogen.

Recent QCD results from ATLAS at the LHC

CERN Document Server

Keoshkerian, H; The ATLAS collaboration

2014-01-01

The ATLAS collaboration has performed studies of a wide range of QCD phenomena, from soft particle to hard photon and jet production. Recent soft-QCD measurements include studies of underlying event, vector meson production. Differential measurements of inclusive and dijet production provide stringent tests of high-order QCD predictions and provide input for determination of parton density functions. Measurements of isolated inclusive and di-photons cross sections for high p_T photons test various theoretical predictions and constrain parton density functions. An overview of these results is given.



Static QCD potential at rQCD-1: Perturbative expansion and operator-product expansion

International Nuclear Information System (INIS)

Sumino, Y.

2007-01-01

We analyze the static QCD potential V QCD (r) in the distance region 0.1 fm QCD (r) analytically. Higher-order terms are estimated by large-β 0 approximation or by renormalization group, and the renormalization scale is varied around the minimal-sensitivity scale. A 'Coulomb'+linear potential can be identified with the scale-independent and renormalon-free part of the prediction and can be separated from the renormalon-dominating part. (II) In the frame of OPE, we define two types of renormalization schemes for the leading Wilson coefficient. One scheme belongs to the class of conventional factorization schemes. The other scheme belongs to a new class, which is independent of the factorization scale, derived from a generalization of the Coulomb+linear potential of (I). The Wilson coefficient is free from IR renormalons and IR divergences in both schemes. We study properties of the Wilson coefficient and of the corresponding nonperturbative contribution δE US (r) in each scheme. (III) We compare numerically perturbative predictions of the Wilson coefficient and lattice computations of V QCD (r) when n l =0. We confirm either correctness or consistency (within uncertainties) of the theoretical predictions made in (II). Then we perform fits to simultaneously determine δE US (r) and r 0 Λ MS 3-loop (relation between lattice scale and Λ MS ). As for the former quantity, we improve bounds as compared to the previous determination; as for the latter quantity, our analysis provides a new method for its determination. We find that (a) δE US (r)=0 is disfavored, and (b) r 0 Λ MS 3-loop =0.574±0.042. We elucidate the mechanism for the sensitivities and examine sources of errors in detail

Hadron interactions at high energy in QCD

International Nuclear Information System (INIS)

Levin, E.M.; Ryskin, M.G.

1988-01-01

Well known the typical hadronic interactions at high energy are soft processes occurring at large distances where the mysterious confinement forces should be essential. Due to this fact, discussing these processes at first sight the authors are to use and really use some models that incorporate their educated guess about the confinement and utilize the QCD degrees of freedom. But really these models use the QCD terminology rather than the explicit form of the QCD interaction. Up to now the multiparticle dynamics had been the dynamics of reggeons with some detailization coming from their hypothesis about confinement. It is the Reggeon Calculus or the reggeon phenomenology that allows them to describe the main properties of exclusive and inclusive reactions at high energy in agreement with experiment. This paper discusses this problem at this Symposium in many details. However, such pure phenomenological understanding cannot satisfy all of us at the moment. The authors would like to understand the multiparticle production and other soft processes at high energy in more microscopic way using directly the form of the QCD Lagrangian

Deuteron transverse densities in holographic QCD

Energy Technology Data Exchange (ETDEWEB)

Mondal, Chandan [Chinese Academy of Sciences, Institute of Modern Physics, Lanzhou (China); Indian Institute of Technology Kanpur, Department of Physics, Kanpur (India); Chakrabarti, Dipankar [Indian Institute of Technology Kanpur, Department of Physics, Kanpur (India); Zhao, Xingbo [Chinese Academy of Sciences, Institute of Modern Physics, Lanzhou (China)

2017-05-15

We investigate the transverse charge density in the longitudinally as well as transversely polarized deuteron using the recent empirical description of the deuteron electromagnetic form factors in the framework of holographic QCD. The predictions of the holographic QCD are compared with the results of a standard phenomenological parameterization. In addition, we evaluate GPDs and the gravitational form factors for the deuteron. The longitudinal momentum densities are also investigated in the transverse plane. (orig.)

How do we model continuum QCD

International Nuclear Information System (INIS)

Cornwall, J.M.

1986-01-01

The nonperturbative aspects of continuum QCD are so complex that one can only hope to approach them through well-motivated models. The author reviews the general properties that any such model must have, based on the understanding of the gluon condensate in the QCD vacuum. A specific, practical model is proposed motivated by a picture of the condensate as made of thick vortex sheets self-consistently constructed from dynamically massive gluons. (author)

Unusual identities for QCD at tree-level

International Nuclear Information System (INIS)

Bjerrum-Bohr, N E J; Damgaard, Poul H; Soendergaard, Thomas; Feng Bo

2011-01-01

We discuss a set of recently discovered quadratic relations between gauge theory amplitudes. Such relations give additional structural simplifications for amplitudes in QCD. Remarkably, their origin lie in an analogous set of relations that involve also gravitons. When certain gluon helicities are flipped we obtain relations that do not involve gravitons, but which refer only to QCD.

Solvable models and hidden symmetries in QCD

International Nuclear Information System (INIS)

Yepez-Martinez, Tochtli; Hess, P. O.; Szczepaniak, A.; Civitarese, O.; Lerma H., S.

2010-01-01

We show that QCD Hamiltonians at low energy exhibit an SU(2) structure, when only few orbital levels are considered. In case many orbital levels are taken into account we also find a semi-analytic solution for the energy levels of the dominant part of the QCD Hamiltonian. The findings are important to propose the structure of phenomenological models.

Parton distributions and lattice QCD calculations: A community white paper

Science.gov (United States)

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.

The exotic atoms of QCD: glueballs, hybrids and baryonia

International Nuclear Information System (INIS)

Barnes, T.

1984-05-01

The theoretical basis underlying the expected ''exotic'' states in QCD, the theory of quarks and gluons, is reviewed in three lectures. The first lecture is an historical introduction to QCD. The second lecture is a critical review of the MIT bag model and QCD on a lattice. The status of three candidate ''exotic'' states seen in psi radiative decays, the i(1440), O(1700) and zeta(2220) are discussed in the third lecture. (author)

Optimizing ROP in formations difficult to be drilled; Optimierung des Bohrfortschritts in schlecht bohrbaren Formationen

Energy Technology Data Exchange (ETDEWEB)

Engmann, M.; Belohlavek, K.U.; Gloth, H. [Technische Univ. Bergakademie Freiberg (Germany); Marx, J.; Luy, R.; Marx, C. [Technische Univ. Clausthal (Germany). Inst. fuer Erdoel- und Erdgastechnik

1998-08-01

In Northern Germany drilling engineers encounter the problem of low rates of progress (ROP) while drilling in the geological formations middle and lower Bunter and Keuper. The ROP is quite low in comparison to other regions, e.g. the North Sea. The performance date of more than 100 wells that were drilled in Northern Germany during the last 10 years were studied by statistical methods. The data under investigation comprise more than 1,000 bit runs. The results of the data analysis were used to set up a prognosis with respect to the potential to improve drilling performance in the target horizons by combining improved drilling bits, more powerful downhole motors, and increased bit hydraulics. For the two Bunter formations a special impregnated drilling bit was conceived, applied, and improved with noticeable success. (orig.) [Deutsch] In Norddeutschland wird in den geologischen Formationen unterer und mittlerer Buntsandstein sowie Keuper wegen der geologischen Besonderheiten haeufig nur ein relativ geringer Bohrfortschritt erzielt. Die Leistungsdaten Bohrfortschritt, Standlaenge und Meterkosten von ueber 100 in Norddeutschland waehrend der letzten 10 Jahre abgeteuften Bohrungen mit mehr als 1000 Meisselmaerschen wurden statistisch ausgewertet. Die Ergebnisse aus den statistischen Auswertungen sowie aus neuartigen Trendkurven zwischen unterschiedlichen Leistungsdaten wurden genutzt, um eine qualitative Abschaetzung der Potentiale zur Verbesserung des Bohrfortschritts durch neue Bohrtechnologie vorzunehmen. Diese betreffen verbesserte Bohrwerkzeuge, leistungsstaerkere Bohrmotore sowie die Erhoehung der hydraulischen Leistung auf Sohle. Fuer die Buntsandsteinformationen ist ein impraegnierter Bohrmeissel konzipiert, eingesetzt und erfolgreich weiterentwickelt worden. (orig.)

Computers for Lattice QCD

International Nuclear Information System (INIS)

Christ, Norman H

2000-01-01

The architecture and capabilities of the computers currently in use for large-scale lattice QCD calculations are described and compared. Based on this present experience, possible future directions are discussed

Simulating QCD at finite density

CERN Document Server

de Forcrand, Philippe

2009-01-01

In this review, I recall the nature and the inevitability of the "sign problem" which plagues attempts to simulate lattice QCD at finite baryon density. I present the main approaches used to circumvent the sign problem at small chemical potential. I sketch how one can predict analytically the severity of the sign problem, as well as the numerically accessible range of baryon densities. I review progress towards the determination of the pseudo-critical temperature T_c(mu), and towards the identification of a possible QCD critical point. Some promising advances with non-standard approaches are reviewed.

The first lap in QCD

International Nuclear Information System (INIS)

Close, F.E.

1980-07-01

The idea that quantum chromodynamics is Nature's choice for the theory of quark interactions and that desirable phenomena, such as quark confinement, are consequences of it are considered. The lecture is presented under the headings: (1) Why do we believe that quarks have colour. (2) A rapid summary of the parton model in deep inelastic scattering. (3) Non Abelian theories: the vertices. (4) Hyperfine splitting of hadrons: more evidence for colour. (5) Renormalisation. (6) Alpha(Q 2 ). (7) The renormalisation group equations. (8) QCD, the renormalisation group equation and deep inelastic data. (9) Higher order corrections in QCD. (U.K.)

Lattice QCD: Status and Prospect

International Nuclear Information System (INIS)

Ukawa, Akira

2006-01-01

A brief review is given of the current status and near-future prospect of lattice QCD studies of the Standard Model. After summarizing a bit of history, we describe current attempts toward inclusion of dynamical up, down and strange quarks. Recent results on the light hadron mass spectrum as well as those on the heavy quark quantities are described. Recent work on lattice pentaquark search is summarized. We touch upon the PACS-CS Project for building our next machine for lattice QCD, and conclude with a summary of computer situation and the physics possibilities over the next several years

Consistent Perturbative Fixed Point Calculations in QCD and Supersymmetric QCD

DEFF Research Database (Denmark)

Ryttov, Thomas A.

2016-01-01

order by order in $\\Delta_f$. We then compute $\\gamma_*$ through $O(\\Delta_f^2)$ for supersymmetric QCD in the $\\overline{\\text{DR}}$ scheme and find that it matches the exact known result. We find that $\\gamma_*$ is astonishingly well described in perturbation theory already at the few loops level...

Light-cone quantization and QCD phenomenology

International Nuclear Information System (INIS)

Brodsky, S.J.; Robertson, D.G.

1995-01-01

In principle, quantum chromodynamics provides a fundamental description of hadronic and nuclear structure and dynamics in terms of their elementary quark and gluon degrees of freedom. In practice, the direct application of QCD to reactions involving the structure of hadrons is extremely complex because of the interplay of nonperturbative effects such as color confinement and multi-quark coherence. A crucial tool in analyzing such phenomena is the use of relativistic light-cone quantum mechanics and Fock state methods to provide tractable and consistent treatments of relativistic many-body systems. In this article we present an overview of this formalism applied to QCD, focusing in particular on applications to the final states in deep inelastic lepton scattering that will be relevant for the proposed European Laboratory for Electrons (ELFE), HERMES, HERA, SLAC, and CEBAF. We begin with a brief introduction to light-cone field theory, stressing how it many allow the derivation of a constituent picture, analogous to the constituent quark model, from QCD. We then discuss several applications of the light-cone Fock state formalism to QCD phenomenology. The Fock state representation includes all quantum fluctuations of the hadron wavefunction, including far off-shell configurations such as intrinsic charm and, in the case of nuclei, hidden color. In some applications, such as exclusive processes at large momentum transfer, one can make first-principle predictions using factorization theorems which separate the hard perturbative dynamics from the nonpertubative physics associated with hadron binding. The Fock state components of the hadron with small transverse size, which dominate hard exclusive reactions, have small color dipole moments and thus diminished hadronic interactions. Thus QCD predicts minimal absorptive corrections, i.e., color transparency for quasi-elastic exclusive reactions in nuclear targets at large momentum transfer

HERA results on QCD and EW physics

International Nuclear Information System (INIS)

Zarnecki, A.F.

1997-01-01

Selected HERA results on QCD and EW interactions are presented. They include the measurement of the proton structure function and its analysis in terms of the QCD evolution, as well as results concerning deep inelastic scattering at very low and very high Q 2 . Selected HERA limits on new physics and parameters which extend the standard model are also presented. (author)

Recent developments in QCD for LHC physics

International Nuclear Information System (INIS)

Anastasiou, C.

2006-01-01

We will review recent theoretical developments in QCD, attempting to assess the phenomenological impact of new theoretical results and to identify potentially useful directions for the future. A part of the talk will be devoted to new imaginative ideas which are rapidly changing the traditional approach to QCD computations, and surprising theoretical discoveries from perturbative calculations on the structure of gauge theories. (author)

Pion form factor within QCD instanton vacuum model

International Nuclear Information System (INIS)

Dorokhov, A.E.

1997-01-01

Instanton induced pion wave function is constructed. It provides an intrinsic k 1 dependence which suppress soft virtual one-gluon exchanges and thus legitimate the perturbative QCD (pQCD) calculations of the pion electromagnetic form factor in the region of momentum transfers above the scale. (author)

Lattice simulations of QCD-like theories at finite baryon density

Energy Technology Data Exchange (ETDEWEB)

Scior, Philipp Friedrich

2016-07-13

The exploration of the phase diagram of quantum chromodynamics (QCD) is of great importance to describe e.g. the properties of neutron stars or heavy-ion collisions. Due to the sign problem of lattice QCD at finite chemical potential we need effective theories to study QCD at finite density. Here, we use a three-dimensional Polyakov-loop theory to study the phase diagrams of QCD-like theories. In particular, we investigate the heavy quark limit of the QCD-like theories where the effective theory can be derived from the full theory by a combined strong coupling and hopping expansion. This expansion can be systematically improved order by order. Since there is no sign problem for the QCD-like theories we consider, we can compare our results to data from lattice calculations of the full theories to make qualitative and quantitative statements of the effective theory's validity. We start by deriving the effective theory up to next-to-next-to leading-order, in particular for two-color and G{sub 2}-QCD where replace the three colors in QCD with only two colors or respectively replace the gauge group SU(3) of QCD with G{sub 2}. We will then apply the effective theory at finite temperature mainly to test the theory and the implementation but also to make some predictions for the deconfinement phase transition in G{sub 2} Yang-Mills theory. Finally, we turn our attention to the cold and dense regime of the phase diagram where we observe a sharp increase of the baryon density with the quark chemical potential μ, when μ reaches half the diquark mass. At vanishing temperature this is expected to happen in a quantum phase transition with Bose-Einstein-condensation of diquarks. In contrast to the liquid-gas transition in QCD, the phase transition to the Bose-Einstein condensate is continuous. We find evidence that the effective theories for heavy quarks are able to describe the qualitative difference between first and second order phase transitions. For even higher μ we

Lattice simulations of QCD-like theories at finite baryon density

International Nuclear Information System (INIS)

Scior, Philipp Friedrich

2016-01-01

The exploration of the phase diagram of quantum chromodynamics (QCD) is of great importance to describe e.g. the properties of neutron stars or heavy-ion collisions. Due to the sign problem of lattice QCD at finite chemical potential we need effective theories to study QCD at finite density. Here, we use a three-dimensional Polyakov-loop theory to study the phase diagrams of QCD-like theories. In particular, we investigate the heavy quark limit of the QCD-like theories where the effective theory can be derived from the full theory by a combined strong coupling and hopping expansion. This expansion can be systematically improved order by order. Since there is no sign problem for the QCD-like theories we consider, we can compare our results to data from lattice calculations of the full theories to make qualitative and quantitative statements of the effective theory's validity. We start by deriving the effective theory up to next-to-next-to leading-order, in particular for two-color and G_2-QCD where replace the three colors in QCD with only two colors or respectively replace the gauge group SU(3) of QCD with G_2. We will then apply the effective theory at finite temperature mainly to test the theory and the implementation but also to make some predictions for the deconfinement phase transition in G_2 Yang-Mills theory. Finally, we turn our attention to the cold and dense regime of the phase diagram where we observe a sharp increase of the baryon density with the quark chemical potential μ, when μ reaches half the diquark mass. At vanishing temperature this is expected to happen in a quantum phase transition with Bose-Einstein-condensation of diquarks. In contrast to the liquid-gas transition in QCD, the phase transition to the Bose-Einstein condensate is continuous. We find evidence that the effective theories for heavy quarks are able to describe the qualitative difference between first and second order phase transitions. For even higher μ we find the rise of the

Lattice investigations of the QCD phase diagram

International Nuclear Information System (INIS)

Guenther, Jana

2016-01-01

To understand the physics in the early universe as well as in heavy ion collisions a throughout understanding of the theory of strong interaction, quantum chromodynamics (QCD), is important. Lattice QCD provides a tool to study it from first principles. However due to the sign problem direct simulations with physical conditions are at the moment limited to zero chemical potential. In this thesis I present a circumvention of this problem. We can gain information on the QCD phase diagram and the equation of state from analytical continuation of results extracted from simulations at imaginary chemical potential. The topological susceptibility is very expensive to compute in Lattice QCD. However it provides an important ingredient for the estimation of the axion mass. The axion is a possible candidate for a dark matter, which plays in important role in the understanding of our universe. In this thesis I discuss two techniques that make it possible to determine the topological susceptibility and allow for an estimation of the axion mass. I then use this mass restrain to analyze the idea of an experiment to detect axions with a dielectric mirror.

Lattice investigations of the QCD phase diagram

Energy Technology Data Exchange (ETDEWEB)

Guenther, Jana

2016-12-15

To understand the physics in the early universe as well as in heavy ion collisions a throughout understanding of the theory of strong interaction, quantum chromodynamics (QCD), is important. Lattice QCD provides a tool to study it from first principles. However due to the sign problem direct simulations with physical conditions are at the moment limited to zero chemical potential. In this thesis I present a circumvention of this problem. We can gain information on the QCD phase diagram and the equation of state from analytical continuation of results extracted from simulations at imaginary chemical potential. The topological susceptibility is very expensive to compute in Lattice QCD. However it provides an important ingredient for the estimation of the axion mass. The axion is a possible candidate for a dark matter, which plays in important role in the understanding of our universe. In this thesis I discuss two techniques that make it possible to determine the topological susceptibility and allow for an estimation of the axion mass. I then use this mass restrain to analyze the idea of an experiment to detect axions with a dielectric mirror.

Academic Training: QCD: are we ready for the LHC

CERN Multimedia

2006-01-01

2006-2007 ACADEMIC TRAINING PROGRAMME LECTURE SERIES 4, 5, 6, 7 December, from 11:00 to 12:00 4, 5, 6 December - Main Auditorium, bldg. 500, 7 December - TH Auditorium, bldg. 4 - 3-006 QCD: are we ready for the LHC S. FRIXIONE / INFN, Genoa, Italy The LHC energy regime poses a serious challenge to our capability of predicting QCD reactions to the level of accuracy necessary for a successful programme of searches for physics beyond the Standard Model. In these lectures, I'll introduce basic concepts in QCD, and present techniques based on perturbation theory, such as fixed-order and resummed computations, and Monte Carlo simulations. I'll discuss applications of these techniques to hadron-hadron processes, concentrating on recent trends in perturbative QCD aimed at improving our understanding of LHC phenomenology.

The AdS/QCD correspondence: still undelivered

International Nuclear Information System (INIS)

Csaki, Csaba; Reece, Matthew; Terning, John

2009-01-01

We consider the particle spectrum and event shapes in large N gauge theories in different regimes of the short-distance 't Hooft coupling, λ. The mesons in the small λ limit should have a Regge spectrum in order to agree with perturbation theory, while generically the large λ theories with gravity duals produce spectra reminiscent of KK modes. We argue that these KK-like states are qualitatively different from QCD modes: they are deeply bound states which are sensitive to short distance interactions rather than the flux tube-like states expected in asymptotically free, confining gauge theories. In addition, we also find that the characteristic event shapes for the large λ theories with gravity duals are close to spherical, very different from QCD-like (small λ, small N) and Nambu-Goto-like (small λ, large N) theories which have jets. This observation is in agreement with the conjecture of Strassler on event shapes in large 't Hooft coupling theories, which was recently proved by Hofman and Maldacena for the conformal case. This conclusion does not change even when considering soft-wall backgrounds for the gravity dual. The picture that emerges is the following: theories with small and large λ are qualitatively different, while theories with small and large N are qualitatively similar. Thus it seems that it is the relative smallness of the 't Hooft coupling in QCD that prevents a reliable AdS/QCD correspondence from emerging, and that reproducing characteristic QCD-like behavior will require genuine stringy dynamics to be incorporated into any putative dual theory.

Hydrochemical and geochemical processes in superficial dump sediments in Zwenkau open brown coal mine; Hydro- und geochemische Prozesse in oberflaechennahen Kippensedimenten des Braunkohlentagebaus Zwenkau

Energy Technology Data Exchange (ETDEWEB)

Wiegand, U.

2002-07-01

es, die durch spektrometrische Erfassungsmethoden der Fernerkundung erhaltenen Ueberfliegungsdaten mittels konventioneller petrographischer, mineralogischer und geochemischer Analytik zu kalibrieren, um der Bergbauindustrie eine wirkungsvolle Methode zu liefern, welche es ermoeglicht, die riesigen Kippenareale des Tagebaubergbaus mit geringem zeitlichen und personellen Aufwand aussagesicher zu klassifizieren, die Sachverhalte mit hoher Genauigkeit raeumlich zuzuordnen und so einer geeigneten Nutzung zuzufuehren. Der Schwerpunkt dieser Arbeit lag dabei in der Charakterisierung der hydro- und geochemischen Veraenderungen in den Kippensedimenten des im mitteldeutschen Raum suedlich von Leipzig aufgeschlossenen Braunkohlentagebaus Zwenkau. Die Erfassung dieser Daten spielt in Hinblick auf eine Rekultivierung und Abschaetzung des Gefaehrdungspotentials der Tagebaulandschaft eine entscheidende Rolle. (orig.)

ALEPH Tau Spectral Functions and QCD

CERN Document Server

Davier, M; Zhang, Z; Davier, Michel; Hoecker, Andreas; Zhang, Zhiqing

2007-01-01

Hadronic $\\tau$ decays provide a clean laboratory for the precise study of quantum chromodynamics (QCD). Observables based on the spectral functions of hadronic $\\tau$ decays can be related to QCD quark-level calculations to determine fundamental quantities like the strong coupling constant, quark and gluon condensates. Using the ALEPH spectral functions and branching ratios, complemented by some other available measurements, and a revisited analysis of the theoretical framework, the value $\\asm = 0.345 \\pm 0.004_{\\rm exp} \\pm 0.009_{\\rm th}$ is obtained. Taken together with the determination of \\asZ from the global electroweak fit, this result leads to the most accurate test of asymptotic freedom: the value of the logarithmic slope of $\\alpha_s^{-1}(s)$ is found to agree with QCD at a precision of 4%. The value of \\asZ obtained from $\\tau$ decays is $\\asZ = 0.1215 \\pm 0.0004_{\\rm exp} \\pm 0.0010_{\\rm th} \\pm 0.0005_{\\rm evol} = 0.1215 \\pm 0.0012$.

Understanding Theoretical Uncertainties in Perturbative QCD Computations

DEFF Research Database (Denmark)

Jenniches, Laura Katharina

effective field theories and perturbative QCD to predict the effect of New Physics on measurements at the LHC and at other future colliders. We use heavy-quark, heavy-scalar and soft-collinear effective theory to calculate a three-body cascade decay at NLO QCD in the expansion-by-regions formalism...... discuss an extension of the Cacciari-Houdeau approach to observables with hadrons in the initial state....

QCD angular correlations for muon pair production

International Nuclear Information System (INIS)

Kajantie, K.; Raitio, R.; Lindfors, J.

1978-01-01

Angular distributions of muons are discussed in the framework of a QCD treatment of muon pair production in hadron-hadron collisions. The predicted angular effects are independent of the infrared behavior of QCD. Measuring them will permit one to determine whether the origin of the large transverse momentum of the pair is in the quark transverse momenta or in a constituent-constituent subprocess. (author)

On microscopic structure of the QCD vacuum

Science.gov (United States)

Pak, D. G.; Lee, Bum-Hoon; Kim, Youngman; Tsukioka, Takuya; Zhang, P. M.

2018-05-01

We propose a new class of regular stationary axially symmetric solutions in a pure QCD which correspond to monopole-antimonopole pairs at macroscopic scale. The solutions represent vacuum field configurations which are locally stable against quantum gluon fluctuations in any small space-time vicinity. This implies that the monopole-antimonopole pair can serve as a structural element in microscopic description of QCD vacuum formation.

Construction of the dual Ginzburg-Landau theory from the lattice QCD

International Nuclear Information System (INIS)

Suganuma, H.; Amemiya, K.; Ichie, H.; Koma, Y.

2002-01-01

We roughly review the QCD physics and then introduce recent topics on the confinement physics. In the maximally abelian (MA) gauge, the low-energy QCD is abelianized owing to the effective off-diagonal gluon mass M off ≅ 1.2 GeV induced by the MA gauge fixing. We demonstrate the construction of the dual Ginzburg-Landau (DGL) theory from the low-energy QCD in the MA gauge in terms of the lattice QCD evidences on infrared abelian dominance and infrared monopole condensation. (author)

Comparative Study of Algorithms for the Numerical Simulation of Lattice QCD

International Nuclear Information System (INIS)

Luz, Fernando H. P.; Mendes, Tereza

2010-01-01

Large-scale numerical simulations are the prime method for a nonperturbative study of QCD from first principles. Although the lattice simulation of the pure-gauge (or quenched-QCD) case may be performed very efficiently on parallel machines, there are several additional difficulties in the simulation of the full-QCD case, i.e. when dynamical quark effects are taken into account. We discuss the main aspects of full-QCD simulations, describing the most common algorithms. We present a comparative analysis of performance for two versions of the hybrid Monte Carlo method (the so-called R and RHMC algorithms), as provided in the MILC software package. We consider two degenerate flavors of light quarks in the staggered formulation, having in mind the case of finite-temperature QCD.

QCD at LEP

CERN Document Server

Metzger, W.J.

2003-01-01

Several preliminary QCD results from e+e- interactions at LEP are reported. These include studies of event shape variables, which are used to determine alpha_s and for studies of the validity of power corrections. Further, a study of color reconnection effects in 3-jet Z decays is reported.

QCD sum rules and applications to nuclear physics

Energy Technology Data Exchange (ETDEWEB)

Cohen, T D [Maryland Univ., College Park, MD (United States). Dept. of Physics; [Washington Univ., Seattle, WA (United States). Dept. of Physics and Inst. for Nuclear Theory; Furnstahl, R J [Ohio State Univ., Columbus, OH (United States). Dept. of Physics; Griegel, D K [Maryland Univ., College Park, MD (United States). Dept. of Physics; [TRIUMF, Vancouver, BC (Canada); Xuemin, J

1994-12-01

Applications of QCD sum-rule methods to the physics of nuclei are reviewed, with an emphasis on calculations of baryon self-energies in infinite nuclear matter. The sum-rule approach relates spectral properties of hadrons propagating in the finite-density medium, such as optical potentials for quasinucleons, to matrix elements of QCD composite operators (condensates). The vacuum formalism for QCD sum rules is generalized to finite density, and the strategy and implementation of the approach is discussed. Predictions for baryon self-energies are compared to those suggested by relativistic nuclear physics phenomenology. Sum rules for vector mesons in dense nuclear matter are also considered. (author). 153 refs., 8 figs.

QCD sum rules and applications to nuclear physics

International Nuclear Information System (INIS)

Cohen, T.D.; Xuemin, J.

1994-12-01

Applications of QCD sum-rule methods to the physics of nuclei are reviewed, with an emphasis on calculations of baryon self-energies in infinite nuclear matter. The sum-rule approach relates spectral properties of hadrons propagating in the finite-density medium, such as optical potentials for quasinucleons, to matrix elements of QCD composite operators (condensates). The vacuum formalism for QCD sum rules is generalized to finite density, and the strategy and implementation of the approach is discussed. Predictions for baryon self-energies are compared to those suggested by relativistic nuclear physics phenomenology. Sum rules for vector mesons in dense nuclear matter are also considered. (author)

Light-Front QCD

Energy Technology Data Exchange (ETDEWEB)

Brodsky, S.

2004-11-30

In these lectures, I survey a number of applications of light-front methods to hadron and nuclear physics phenomenology and dynamics, including light-front statistical physics. Light-front Fock-state wavefunctions provide a frame-independent representation of hadrons in terms of their fundamental quark and gluon degrees of freedom. Nonperturbative methods for computing LFWFs in QCD are discussed, including string/gauge duality which predicts the power-law fall-off at high momentum transfer of light-front Fock-state hadronic wavefunctions with an arbitrary number of constituents and orbital angular momentum. The AdS/CFT correspondence has important implications for hadron phenomenology in the conformal limit, including an all-orders derivation of counting rules for exclusive processes. One can also compute the hadronic spectrum of near-conformal QCD assuming a truncated AdS/CFT space. Given the LFWFs, one can compute form factors, heavy hadron decay amplitudes, hadron distribution amplitudes, and the generalized parton distributions underlying deeply virtual Compton scattering. The quantum fluctuations represented by the light-front Fock expansion leads to novel QCD phenomena such as color transparency, intrinsic heavy quark distributions, diffractive dissociation, and hidden-color components of nuclear wavefunctions. A new test of hidden color in deuteron photodisintegration is proposed. The origin of leading-twist phenomena such as the diffractive component of deep inelastic scattering, single-spin asymmetries, nuclear shadowing and antishadowing is also discussed; these phenomena cannot be described by light-front wavefunctions of the target computed in isolation. Part of the anomalous NuTeV results for the weak mixing angle {theta}{sub W} could be due to the non-universality of nuclear antishadowing for charged and neutral currents.

Continuing progress on a lattice QCD software infrastructure

International Nuclear Information System (INIS)

Joo, B

2008-01-01

We report on the progress of the software effort in the QCD application area of SciDAC. In particular, we discuss how the software developed under SciDAC enabled the aggressive exploitation of leadership computers, and we report on progress in the area of QCD software for multi-core architectures

Holographic models and the QCD trace anomaly

International Nuclear Information System (INIS)

Goity, Jose L.; Trinchero, Roberto C.

2012-01-01

Five dimensional dilaton models are considered as possible holographic duals of the pure gauge QCD vacuum. In the framework of these models, the QCD trace anomaly equation is considered. Each quantity appearing in that equation is computed by holographic means. Two exact solutions for different dilaton potentials corresponding to perturbative and non-perturbative β-functions are studied. It is shown that in the perturbative case, where the β-function is the QCD one at leading order, the resulting space is not asymptotically AdS. In the non-perturbative case, the model considered presents confinement of static quarks and leads to a non-vanishing gluon condensate, although it does not correspond to an asymptotically free theory. In both cases analyses based on the trace anomaly and on Wilson loops are carried out.

The QCD/SM working group: Summary report

International Nuclear Information System (INIS)

Giele, W.

2004-01-01

Quantum Chromo-Dynamics (QCD), and more generally the physics of the Standard Model (SM), enter in many ways in high energy processes at TeV Colliders, and especially in hadron colliders (the Tevatron at Fermilab and the forthcoming LHC at CERN), First of all, at hadron colliders, QCD controls the parton luminosity, which rules the production rates of any particle or system with large invariant mass and/or large transverse momentum. Accurate predictions for any signal of possible ''New Physics'' sought at hadron colliders, as well as the corresponding backgrounds, require an improvement in the control of uncertainties on the determination of PDF and of the propagation of these uncertainties in the predictions. Furthermore, to fully exploit these new types of PDF with uncertainties, uniform tools (computer interfaces, standardization of the PDF evolution codes used by the various groups fitting PDF's) need to be proposed and developed. The dynamics of colour also affects, both in normalization and shape, various observables of the signals of any possible ''New Physics'' sought at the TeV scale, such as, e.g. the production rate, or the distributions in transverse momentum of the Higgs boson. Last, but not least, QCD governs many backgrounds to the searches for this ''New Physics''. Large and important QCD corrections may come from extra hard parton emission (and the corresponding virtual corrections), involving multi-leg and/or multi-loop amplitudes. This requires complex higher order calculations, and new methods have to be designed to compute the required multi-legs and/or multi-loop corrections in a tractable form. In the case of semi-inclusive observables, logarithmically enhanced contributions coming from multiple soft and collinear gluon emission require sophisticated QCD resummation techniques. Resummation is a catch-all name for efforts to extend the predictive power of QCD by summing the large logarithmic corrections to all orders in perturbation theory. In

The QCD/SM working group: Summary report

Energy Technology Data Exchange (ETDEWEB)

W. Giele et al.

2004-01-12

Quantum Chromo-Dynamics (QCD), and more generally the physics of the Standard Model (SM), enter in many ways in high energy processes at TeV Colliders, and especially in hadron colliders (the Tevatron at Fermilab and the forthcoming LHC at CERN), First of all, at hadron colliders, QCD controls the parton luminosity, which rules the production rates of any particle or system with large invariant mass and/or large transverse momentum. Accurate predictions for any signal of possible ''New Physics'' sought at hadron colliders, as well as the corresponding backgrounds, require an improvement in the control of uncertainties on the determination of PDF and of the propagation of these uncertainties in the predictions. Furthermore, to fully exploit these new types of PDF with uncertainties, uniform tools (computer interfaces, standardization of the PDF evolution codes used by the various groups fitting PDF's) need to be proposed and developed. The dynamics of colour also affects, both in normalization and shape, various observables of the signals of any possible ''New Physics'' sought at the TeV scale, such as, e.g. the production rate, or the distributions in transverse momentum of the Higgs boson. Last, but not least, QCD governs many backgrounds to the searches for this ''New Physics''. Large and important QCD corrections may come from extra hard parton emission (and the corresponding virtual corrections), involving multi-leg and/or multi-loop amplitudes. This requires complex higher order calculations, and new methods have to be designed to compute the required multi-legs and/or multi-loop corrections in a tractable form. In the case of semi-inclusive observables, logarithmically enhanced contributions coming from multiple soft and collinear gluon emission require sophisticated QCD resummation techniques. Resummation is a catch-all name for efforts to extend the predictive power of QCD by summing the large

Non-perturbative QCD and hadron physics

International Nuclear Information System (INIS)

Cobos-Martínez, J J

2016-01-01

A brief exposition of contemporary non-perturbative methods based on the Schwinger-Dyson (SDE) and Bethe-Salpeter equations (BSE) of Quantum Chromodynamics (QCD) and their application to hadron physics is given. These equations provide a non-perturbative continuum formulation of QCD and are a powerful and promising tool for the study of hadron physics. Results on some properties of hadrons based on this approach, with particular attention to the pion distribution amplitude, elastic, and transition electromagnetic form factors, and their comparison to experimental data are presented. (paper)

The instanton liquid model of QCD

International Nuclear Information System (INIS)

Blotz, A.

1998-01-01

Within a microscopic model for the non-perturbative vacuum of QCD, hadronic correlation functions are calculated. In the model the vacuum is a statistical, interacting ensemble of instantons and anti-instantons at the scale of Λ QCD . Hadronic two-point as well as three-point correlation functions are evaluated and compared with phenomenological information about the spectra, couplings and form factors. Especially the electro magnetic form factor of the pion is obtained and new predictions for the charm contribution to DIS structure functions are made

Two flavor QCD and confinement - II

DEFF Research Database (Denmark)

Cossu, G.; D'Elia, M.; Di Giacomo, A.

2007-01-01

This paper is part of a program of investigation of the chiral transition in Nf=2 QCD, started in Phys.Rev.D72:114510,2005. Progress is reported on theunderstanding of some possible systematic errors. A direct test of first orderscaling is presented.......This paper is part of a program of investigation of the chiral transition in Nf=2 QCD, started in Phys.Rev.D72:114510,2005. Progress is reported on theunderstanding of some possible systematic errors. A direct test of first orderscaling is presented....

The η' meson from lattice QCD

International Nuclear Information System (INIS)

Jansen, K.; Michael, C.; Urbach, C.

2008-04-01

We study the flavour singlet pseudoscalar mesons from first principles using lattice QCD. With N f =2 flavours of light quark, this is the so-called η 2 meson and we discuss the phenomenological status of this. Using maximally twisted-mass lattice QCD, we extract the mass of the η 2 meson at two values of the lattice spacing for lighter quarks than previously discussed in the literature. We are able to estimate the mass value in the limit of light quarks with their physical masses. (orig.)

Perturbative QCD and jets

International Nuclear Information System (INIS)

Mueller, A.H.

1986-03-01

A brief review of some of the recent progress in perturbative QCD is given (heavy quark production, small-x physics, minijets and related topics, classical simulations in high energy reactions, coherence and the string effect)

The strong coupling constant of QCD with four flavors

Energy Technology Data Exchange (ETDEWEB)

Tekin, Fatih

2010-11-01

In this thesis we study the theory of strong interaction Quantum Chromodynamics on a space-time lattice (lattice QCD) with four flavors of dynamical fermions by numerical simulations. In the early days of lattice QCD, only pure gauge field simulations were accessible to the computational facilities and the effects of quark polarization were neglected. The so-called fermion determinant in the path integral was set to one (quenched approximation). The reason for this approximation was mainly the limitation of computational power because the inclusion of the fermion determinant required an enormous numerical effort. However, for full QCD simulations the virtual quark loops had to be taken into account and the development of new machines and new algorithmic techniques made the so-called dynamical simulations with at least two flavors possible. In recent years, different collaborations studied lattice QCD with dynamical fermions. In our project we study lattice QCD with four degenerated flavors of O(a) improved Wilson quarks in the Schroedinger functional scheme and calculate the energy dependence of the strong coupling constant. For this purpose, we determine the O(a) improvement coefficient c{sub sw} with four flavors and use this result to calculate the step scaling function of QCD with four flavors which describes the scale evolution of the running coupling. Using a recursive finite-size technique, the {lambda} parameter is determined in units of a technical scale L{sub max} which is an unambiguously defined length in the hadronic regime. The coupling {alpha}{sub SF} of QCD in the so-called Schroedinger functional scheme is calculated over a wide range of energies non-perturbatively and compared with 2-loop and 3-loop perturbation theory as well as with the non-perturbative result for only two flavors. (orig.)

The strong coupling constant of QCD with four flavors

International Nuclear Information System (INIS)

Tekin, Fatih

2010-01-01

In this thesis we study the theory of strong interaction Quantum Chromodynamics on a space-time lattice (lattice QCD) with four flavors of dynamical fermions by numerical simulations. In the early days of lattice QCD, only pure gauge field simulations were accessible to the computational facilities and the effects of quark polarization were neglected. The so-called fermion determinant in the path integral was set to one (quenched approximation). The reason for this approximation was mainly the limitation of computational power because the inclusion of the fermion determinant required an enormous numerical effort. However, for full QCD simulations the virtual quark loops had to be taken into account and the development of new machines and new algorithmic techniques made the so-called dynamical simulations with at least two flavors possible. In recent years, different collaborations studied lattice QCD with dynamical fermions. In our project we study lattice QCD with four degenerated flavors of O(a) improved Wilson quarks in the Schroedinger functional scheme and calculate the energy dependence of the strong coupling constant. For this purpose, we determine the O(a) improvement coefficient c sw with four flavors and use this result to calculate the step scaling function of QCD with four flavors which describes the scale evolution of the running coupling. Using a recursive finite-size technique, the Λ parameter is determined in units of a technical scale L max which is an unambiguously defined length in the hadronic regime. The coupling α SF of QCD in the so-called Schroedinger functional scheme is calculated over a wide range of energies non-perturbatively and compared with 2-loop and 3-loop perturbation theory as well as with the non-perturbative result for only two flavors. (orig.)

QCD leading order study of the J/ψ leptoproduction at HERA within the nonrelativistic QCD framework

Energy Technology Data Exchange (ETDEWEB)

Sun, Zhan [Guizhou Minzu University, School of Science, Guiyang (China); Zhang, Hong-Fei [Third Military Medical University, Department of Physics, School of Biomedical Engineering, Chongqing (China)

2017-11-15

As indicated in our previous paper (Zhang and Sun in Phys. Rev. D 96:034002, 2017), the existing literature studying the J/ψ production in deeply inelastic scattering (DIS) in collinear factorisation is on the basis of a formalism that will lead to wrong results when the ranges of the transverse momentum or the rapidity of the J/ψ in the laboratory frame do not cover all values possible for them. In this paper, we present the renewed results for the J/ψ production in DIS at HERA within the nonrelativistic QCD framework at QCD leading order (LO). Three different sets of the long-distance matrix elements are employed for comparison. The predictions via the colour-singlet (CS) model at QCD LO are generally below the experimental data especially in the regions where perturbation theory are expected to work well, while the colour-octet contributions are of the same order of magnitude as the CS ones, however, in general make the agreement between theory and experiment better. (orig.)

Various versions of analytic QCD and skeleton-motivated evaluation of observables

International Nuclear Information System (INIS)

Cvetic, Gorazd; Valenzuela, Cristian

2006-01-01

We present skeleton-motivated evaluation of QCD observables. The approach can be applied in analytic versions of QCD in certain classes of renormalization schemes. We present two versions of analytic QCD which can be regarded as low-energy modifications of the ''minimal'' analytic QCD and which reproduce the measured value of the semihadronic τ decay ratio r τ . Further, we describe an approach of calculating the higher-order analytic couplings A k (k=2,3,...) on the basis of logarithmic derivatives of the analytic coupling A 1 (Q 2 ). This approach can be applied in any version of analytic QCD. We adjust the free parameters of the aforementioned two analytic models in such a way that the skeleton-motivated evaluation reproduces the correct known values of r τ and of the Bjorken polarized sum rule (BjPSR) d b (Q 2 ) at a given point (e.g., at Q 2 =2 GeV 2 ). We then evaluate the low-energy behavior of the Adler function d v (Q 2 ) and the BjPSR d b (Q 2 ) in the aforementioned evaluation approach, in the three analytic versions of QCD. We compare with the results obtained in the minimal analytic QCD and with the evaluation approach of Milton et al. and Shirkov

Baryons and QCD

International Nuclear Information System (INIS)

Nathan Isgur

1997-01-01

The author presents an idiosyncratic view of baryons which calls for a marriage between quark-based and hadronic models of QCD. He advocates a treatment based on valence quark plus glue dominance of hadron structure, with the sea of q pairs (in the form of virtual hadron pairs) as important corrections

Strong coupling QCD and the (π+,π-) reaction

International Nuclear Information System (INIS)

Miller, G.A.; Washington Univ., Seattle, WA

1989-01-01

Previous six-quark bag model calculations are in disagreement with new (π + , π - ) data, but conventional nucleonic calculations are generally successful. Six-quark bag models are related to perturbative QCD. I argue that the strong coupling limit of QCD (SCQCD) is a more appropriate starting point for nuclear physics. 15 refs., 3 figs

Q.C.D. estimates of hadronic cross sections

International Nuclear Information System (INIS)

Navelet, H.; Peschanski, R.

1983-03-01

Estimates for hadron-hadron cross-sections are made using the leading log approximation of Q.C.D. The rise of the total inelastic pp cross-sections at high energy is reproduced, thanks to the competition between the small parton-parton interaction and the large multiplicity of gluons predicted by Q.C.D

The structure of gluon radiation in QCD

International Nuclear Information System (INIS)

Parke, S.; Mangano, M.

1990-01-01

For massless QCD the hard scattering amplitudes are naturally written in terms of the dual color expansion. Here I present this expansion for purely gluonic processes and processes involving quark-antiquark pairs and gluons. The properties of the sub-amplitudes as well as explicit algebraic expressions are given for a number of these processess. Finally, I demonstrate how to recover massless QED amplitudes from the dual expansion of massless QCD

QCD and hard diffraction at the LHC

International Nuclear Information System (INIS)

Albrow, Michael G.; Fermilab

2005-01-01

As an introduction to QCD at the LHC I given an overview of QCD at the Tevatron, emphasizing the high Q 2 frontier which will be taken over by the LHC. After describing briefly the LHC detectors I discuss high mass diffraction, in particular central exclusive production of Higgs and vector boson pairs. I introduce the FP420 project to measure the scattered protons 420 m downstream of ATLAS and CMS

Unambiguity of renormalization group calculations in QCD

International Nuclear Information System (INIS)

Vladimirov, A.A.

1979-01-01

A detailed analysis of the reduction of ambiguities determined by an arbitrary renormalization scheme is presented for the renormalization group calculations of physical quantities in quantum chromodynamics (QCD). Some basic formulas concerning the renormalization-scheme dependence of Green's and renormalization group functions are given. A massless asymptotically free theory with one coupling constant g is considered. In conclusion, several rules for renormalization group calculations in QCD are formulated

ATLAS soft QCD results

CERN Document Server

Sykora, Tomas; The ATLAS collaboration

2018-01-01

Recent results of soft QCD measurements performed by the ATLAS collaboration are reported. The measurements include total, elastic and inelastic cross sections, inclusive spectra, underlying event and particle correlations in p-p and p-Pb collisions.

Light hadron spectrum from quenched lattice QCD. Results from the CP-PACS

International Nuclear Information System (INIS)

Yoshie, Tomoteru

2001-01-01

Deriving the light hadron spectrum from first principles of QCD has been a fundamental issue in elementary particle physics since the mid-1970s, when QCD was established. With this goal in mind, we have carried out large-scale simulations of lattice QCD on the CP-PACS computer. In this article, we present results for the light hadron spectrum derived in the quenched approximation to lattice QCD. We find that although the global structure of the observed spectrum is reproduced, the quenched spectrum systematically deviates from experiment when examined with an accuracy at better than a 10% level. Results for light quark masses are also reported. Another simulation of full QCD done recently (also on the CP-PACS computer) shows indications that the discrepancy observed in quenched QCD is significantly reduced by the introduction of two flavors of light dynamical quarks. (author)

'Fixed point' QCD analysis of the CCFR data on deep inelastic neutrino-nucleon scattering

International Nuclear Information System (INIS)

Sidorov, A.V.; Stamenov, D.B.

1995-01-01

The results of LO Fixed point QCD (FP-QCD) analysis of the CCFR data for the nucleon structure function xF 3 (x,Q 2 ) are presented. The predictions of FP-QCD, in which α S (Q 2 ) tends to a nonzero coupling constant α 0 as Q 2 → ∞, are in good agreement with the data. The description of the data is even better than that in the case of LO QCD. The FP-QCD parameter α 0 is determined with a good accuracy: α 0 0.198 ± 0.009. Having in mind the recent QCD fits to the same data we conclude that unlike the high precision and large (x,Q 2 ) kinematic range of the CCFR data they cannot discriminate between QCD and FP-QCD predictions for xF 3 (x,Q 2 ). 11 refs., 1 tab

Light relativistic bound states in high temperature QCD

International Nuclear Information System (INIS)

Zahed, Ismail

1991-01-01

The nonperturbative structure of high temperature QCD is combined with generalized sum-rules arguments to analyse gauge invariant correlation functions in real time. It is shown that for a plausible choice of condensates, QCD at high temperature exhibits color singlet excitations as opposed to merely screened quarks and gluons. (author). 14 refs.; 2 figs

Lattice QCD production on commodity clusters at Fermilab

International Nuclear Information System (INIS)

Holmgren, D.

2003-01-01

We describe the construction and results to date of Fermilab's three Myrinet-networked lattice QCD production clusters (an 80-node dual Pentium III cluster, a 48-node dual Xeon cluster, and a 128-node dual Xeon cluster). We examine a number of aspects of performance of the MILC lattice QCD code running on these clusters

Confinining properties of QCD in strong magnetic backgrounds

Directory of Open Access Journals (Sweden)

Bonati Claudio

2017-01-01

Full Text Available Strong magnetic backgrounds are known to modify QCD properties at a nonperturbative level. We discuss recent lattice results, obtained for Nf = 2 + 1 QCD with physical quark masses, concerning in particular the modifications and the anisotropies induced at the level of the static quark-antiquark potential, both at zero and finite temperature.

Massive pions, anomalies and baryons in holographic QCD

Energy Technology Data Exchange (ETDEWEB)

Domenech, O. [Departament de Fisica and IFAE, Universitat Autonoma de Barcelona, 08193 Bellaterra, Barcelona (Spain); Panico, G., E-mail: panico@phys.ethz.c [Institute for Theoretical Physics, ETH Zurich, 8093 Zurich (Switzerland); Wulzer, A. [Institut de Theorie des Phenomenes Physiques, EPFL, CH-1015 Lausanne (Switzerland)

2011-03-01

We consider a holographic model of QCD, obtained by a very simple modification of the original construction, which describes at the same time the pion mass, the QCD anomalies and the baryons as topological solitons. We study in detail its phenomenological implications in both the mesonic and baryonic sectors and compare with the observations.

Critical opalescence in baryonic QCD matter.

Science.gov (United States)

Antoniou, N G; Diakonos, F K; Kapoyannis, A S; Kousouris, K S

2006-07-21

We show that critical opalescence, a clear signature of second-order phase transition in conventional matter, manifests itself as critical intermittency in QCD matter produced in experiments with nuclei. This behavior is revealed in transverse momentum spectra as a pattern of power laws in factorial moments, to all orders, associated with baryon production. This phenomenon together with a similar effect in the isoscalar sector of pions (sigma mode) provide us with a set of observables associated with the search for the QCD critical point in experiments with nuclei at high energies.

QCD measurements with the CMS detector

CERN Multimedia

CERN. Geneva

2011-01-01

In the first year of LHC data taking, CMS pursued a rich program of QCD physics. In the low-pt front, results on momentum-, pseudorapidity- and multiplicity distributions of charged and strange hadrons, underlying event observables, two particle rapidity correlations and Bose-Einstein correlations are presented. In the high-pt front, jet and photon cross-section measurements are reported on inclusive and di-object production, as well as ratios of 3/2 jet cross sections. Finally, the QCD multi-jet dynamics is explored with event-shapes variables, dijet azimuthal decorrelations and dijet angular distributions

Identifying QCD Transition Using Deep Learning

Science.gov (United States)

Zhou, Kai; Pang, Long-gang; Su, Nan; Petersen, Hannah; Stoecker, Horst; Wang, Xin-Nian

2018-02-01

In this proceeding we review our recent work using supervised learning with a deep convolutional neural network (CNN) to identify the QCD equation of state (EoS) employed in hydrodynamic modeling of heavy-ion collisions given only final-state particle spectra ρ(pT, V). We showed that there is a traceable encoder of the dynamical information from phase structure (EoS) that survives the evolution and exists in the final snapshot, which enables the trained CNN to act as an effective "EoS-meter" in detecting the nature of the QCD transition.

Critical Opalescence in Baryonic QCD Matter

Science.gov (United States)

Antoniou, N. G.; Diakonos, F. K.; Kapoyannis, A. S.; Kousouris, K. S.

2006-07-01

We show that critical opalescence, a clear signature of second-order phase transition in conventional matter, manifests itself as critical intermittency in QCD matter produced in experiments with nuclei. This behavior is revealed in transverse momentum spectra as a pattern of power laws in factorial moments, to all orders, associated with baryon production. This phenomenon together with a similar effect in the isoscalar sector of pions (sigma mode) provide us with a set of observables associated with the search for the QCD critical point in experiments with nuclei at high energies.

Critical Opalescence in Baryonic QCD Matter

International Nuclear Information System (INIS)

Antoniou, N. G.; Diakonos, F. K.; Kapoyannis, A. S.; Kousouris, K. S.

2006-01-01

We show that critical opalescence, a clear signature of second-order phase transition in conventional matter, manifests itself as critical intermittency in QCD matter produced in experiments with nuclei. This behavior is revealed in transverse momentum spectra as a pattern of power laws in factorial moments, to all orders, associated with baryon production. This phenomenon together with a similar effect in the isoscalar sector of pions (sigma mode) provide us with a set of observables associated with the search for the QCD critical point in experiments with nuclei at high energies

Large Nc QCD at nonzero chemical potential

International Nuclear Information System (INIS)

Cohen, Thomas D.

2004-01-01

The general issue of large N c QCD at nonzero chemical potential is considered with a focus on understanding the difference between large N c QCD with an isospin chemical potential and large N c QCD with a baryon chemical potential. A simple diagrammatic analysis analogous to 't Hooft's analysis at μ=0 implies that the free energy with a given baryon chemical potential is equal to the free energy with an isospin chemical potential of the same value plus 1/N c corrections. Phenomenologically, these two systems behave quite differently. A scenario to explain this difference in light of the diagrammatic analysis is explored. This scenario is based on a phase transition associated with pion condensation when the isospin chemical potential exceeds m π /2; associated with this transition there is breakdown of the 1/N c expansion--in the pion condensed phase there is a distinct 1/N c expansion including a larger set of diagrams. While this scenario is natural, there are a number of theoretical issues which at least superficially challenge it. Most of these can be accommodated. However, the behavior of quenched QCD which raises a number of apparently analogous issues cannot be easily understood completely in terms of an analogous scenario. Thus, the overall issue remains open

Nucleon structure from lattice QCD

Energy Technology Data Exchange (ETDEWEB)

Dinter, Simon

2012-11-13

In this thesis we compute within lattice QCD observables related to the structure of the nucleon. One part of this thesis is concerned with moments of parton distribution functions (PDFs). Those moments are essential elements for the understanding of nucleon structure and can be extracted from a global analysis of deep inelastic scattering experiments. On the theoretical side they can be computed non-perturbatively by means of lattice QCD. However, since the time lattice calculations of moments of PDFs are available, there is a tension between these lattice calculations and the results from a global analysis of experimental data. We examine whether systematic effects are responsible for this tension, and study particularly intensively the effects of excited states by a dedicated high precision computation. Moreover, we carry out a first computation with four dynamical flavors. Another aspect of this thesis is a feasibility study of a lattice QCD computation of the scalar quark content of the nucleon, which is an important element in the cross-section of a heavy particle with the nucleon mediated by a scalar particle (e.g. Higgs particle) and can therefore have an impact on Dark Matter searches. Existing lattice QCD calculations of this quantity usually have a large error and thus a low significance for phenomenological applications. We use a variance-reduction technique for quark-disconnected diagrams to obtain a precise result. Furthermore, we introduce a new stochastic method for the calculation of connected 3-point correlation functions, which are needed to compute nucleon structure observables, as an alternative to the usual sequential propagator method. In an explorative study we check whether this new method is competitive to the standard one. We use Wilson twisted mass fermions at maximal twist in all our calculations, such that all observables considered here have only O(a{sup 2}) discretization effects.

Nucleon structure from lattice QCD

International Nuclear Information System (INIS)

Dinter, Simon

2012-01-01

In this thesis we compute within lattice QCD observables related to the structure of the nucleon. One part of this thesis is concerned with moments of parton distribution functions (PDFs). Those moments are essential elements for the understanding of nucleon structure and can be extracted from a global analysis of deep inelastic scattering experiments. On the theoretical side they can be computed non-perturbatively by means of lattice QCD. However, since the time lattice calculations of moments of PDFs are available, there is a tension between these lattice calculations and the results from a global analysis of experimental data. We examine whether systematic effects are responsible for this tension, and study particularly intensively the effects of excited states by a dedicated high precision computation. Moreover, we carry out a first computation with four dynamical flavors. Another aspect of this thesis is a feasibility study of a lattice QCD computation of the scalar quark content of the nucleon, which is an important element in the cross-section of a heavy particle with the nucleon mediated by a scalar particle (e.g. Higgs particle) and can therefore have an impact on Dark Matter searches. Existing lattice QCD calculations of this quantity usually have a large error and thus a low significance for phenomenological applications. We use a variance-reduction technique for quark-disconnected diagrams to obtain a precise result. Furthermore, we introduce a new stochastic method for the calculation of connected 3-point correlation functions, which are needed to compute nucleon structure observables, as an alternative to the usual sequential propagator method. In an explorative study we check whether this new method is competitive to the standard one. We use Wilson twisted mass fermions at maximal twist in all our calculations, such that all observables considered here have only O(a 2 ) discretization effects.

QCD and hadron structure

International Nuclear Information System (INIS)

Kaplan, D.B.

1995-01-01

I give a brief and selective overview of QCD as it pertains to determining hadron structure, and the relevant directions in this field for nuclear theory. This document is intended to start discussion about priorities, not end it

A consistent analysis for the quark condensate in QCD

International Nuclear Information System (INIS)

Huang Zheng; Huang Tao

1988-08-01

The dynamical symmetry breaking in QCD is analysed based on the vacuum condensates. A self-consistent equation for the quark condensate (φ φ) is derived. A nontrivial solution for (φ φ) ≠ 0 is given in terms of the QCD scale parameter A

QCD predictions for weak neutral current structure functions

International Nuclear Information System (INIS)

Wu Jimin

1987-01-01

Employing the analytic expression (to the next leading order) for non-singlet component of structure function which the author got from QCD theory and putting recent experiment result of neutral current structure function at Q 2 = 11 (GeV/C) 2 as input, the QCD prediction for neutral current structure function of their scaling violation behaviours was given

Precise tests of QCD in e+e- annihilation

International Nuclear Information System (INIS)

Burrows, P.N.

1997-03-01

A pedagogical review is given of precise tests of QCD in electron-positron annihilation. Emphasis is placed on measurements that have served to establish QCD as the correct theory of strong interactions, as well as measurements of the coupling parameter α s . An outlook is given for future important tests at a high-energy e + e - collider

Tevatron-for-LHC Report of the QCD Working Group

Energy Technology Data Exchange (ETDEWEB)

Albrow, Michael G.; Begel, M.; Bourilkov, D.; Campanelli, M.; Chlebana, F.; De Roeck, A.; Dittmann, J.R.; Ellis, S.D.; Field, B.; Field, R.; Gallinaro, M.; /Fermilab

2006-10-01

The experiments at Run 2 of the Tevatron have each accumulated over 1 fb{sup -1} of high-transverse momentum data. Such a dataset allows for the first precision (i.e. comparisons between theory and experiment at the few percent level) tests of QCD at a hadron collider. While the Large Hadron Collider has been designed as a discovery machine, basic QCD analyses will still need to be performed to understand the working environment. The Tevatron-for-LHC workshop was conceived as a communication link to pass on the expertise of the Tevatron and to test new analysis ideas coming from the LHC community. The TeV4LHC QCD Working Group focused on important aspects of QCD at hadron colliders: jet definitions, extraction and use of Parton Distribution Functions, the underlying event, Monte Carlo tunes, and diffractive physics. This report summarizes some of the results achieved during this workshop.

Innovations in lattice QCD algorithms

International Nuclear Information System (INIS)

Orginos, Konstantinos

2006-01-01

Lattice QCD calculations demand a substantial amount of computing power in order to achieve the high precision results needed to better understand the nature of strong interactions, assist experiment to discover new physics, and predict the behavior of a diverse set of physical systems ranging from the proton itself to astrophysical objects such as neutron stars. However, computer power alone is clearly not enough to tackle the calculations we need to be doing today. A steady stream of recent algorithmic developments has made an important impact on the kinds of calculations we can currently perform. In this talk I am reviewing these algorithms and their impact on the nature of lattice QCD calculations performed today

QCD in e+e- annihilation

International Nuclear Information System (INIS)

Ali, A.

1981-04-01

The promise of e + e - annihilation as an ideal laboratory to test Quantum Chromodynamics, QCD, has been the dominating theme in elementary particle physics during the last several years. An attempt is made to partially survey the subject in deep perturbative region in e + e - annihilation where theoretical ambiguities are minimal. Topics discussed include a review of the renormalization group methods relevant for e + e - annihilation, total hadronic cross section, jets and large-psub(T) phenomena, non-perturbative quark and gluon fragmentation effects and analysis of the jet distributions measured at DORIS, SPEAR and PETRA. My hope is to review realistic tests of QCD in e + e - annihilation - as opposed to the ultimate tests, which abound in literature. (orig.)

Gluonium spectrum in QCD

International Nuclear Information System (INIS)

Dominguez, C.A.

1987-02-01

The scalar (0 ++ ) and the tensor (2 ++ ) gluonium spectrum is analyzed in the framework of QCD sum rules. Stable eigenvalue solutions, consistent with duality and low energy theorems, are obtained for the mass and width of these glueballs. (orig.)

Basic concepts and estimated maximum possible employment effects of a consistent development of renewable energy systems in Nordrhein-Westfalen. 1st technical report; Konzeptionelle Grundlagen und Abschaetzung zukuenftig maximal moeglicher Bruttobeschaeftigungseffekte beim Ausbau erneuerbarer Energiesysteme in Nordrhein-Westfalen. 1. Technischer Fachbericht

Energy Technology Data Exchange (ETDEWEB)

Mohr, M.; Ziegelmann, A.; Unger, H.

1995-12-01

In the First Technical Report the fundamental ideas for the realization of this project are presented and the future possible maximum gross employment effects of an expansion of renewable energy systems in North-Rhine-Westphalia with consideration of the present-day cost structure are quantified in an initial stage. In this connection gross employment effects are defined as exclusive positive job effects without consideration of possible negative employment effects on the basis of less investments in other sectors of the economy. Based on a subdivided presentation of the intended course of the project and a formulation of its main objectives, a detailed description of the theoretical background of the applied methods of input-output analysis is provided. After the presentation of some different methods and the necessary assumptions, the analysis takes the so-called `Keynesian income multiplier` into account to accommodate the effects of an increase in national income. To use a known investment distribution, grouped in 21 sub-divisions according to categories of applications, within the scope of an input-output-analysis, the investments are converted. After the determination of the matrices, necessary to quantify employment effects, the maximum possible gross effects concerning the future job market of the Federal Republic of Germany will be assessed with consideration of the fluctuations in productivity on sector level. A total of 700.000 new jobs can be expected, of which about 27% are due to the increase of personal disposable income and the resulting rise in consumer spending respectively. (orig./UA) [Deutsch] Im vorliegenden 1. Technischen Fachbericht werden konzeptionelle Grundlagen zur Realisierung des Vorhabens eroertert und es wird eine erste Abschaetzung der potentiellen Bruttobeschaeftigungswirkungen eines Ausbaus erneuerbarer Energiesysteme in Nordrhein-Westfalen durchgefuehrt. Unter Bruttobeschaeftigungswirkungen werden dabei ausschliesslich positive

From notes to chords in QCD

International Nuclear Information System (INIS)

Wilczek, F.

1998-01-01

After a very brief overview recollecting the 'classic' parts of QCD, that is its application to describe hard processes and static properties of hadrons, I survey recent work - some very recent - on QCD at non-zero temperature and density. At finite temperature and zero density there is a compelling theoretical framework allowing us to predict highly specific, non-trivial dependence of the phase structure on the number of flavors and colors. Several aspects have been rigorously, and successfully, tested against massive numerical realizations of the microscopic theory. The theoretical description of high density is nowhere near as mature, but some intriguing possibilities have been put forward. The color/flavor locked state recently proposed for three flavors has many remarkable features connected to its basic symmetry structure, notably including chiral symmetry re-breaking and the existence (unlike for two flavors) of a gauge invariant order parameter. I survey potential applications to heavy ion collisions, astrophysics, and cosmology. A noteworthy possibility is that stellar explosions are powered by release of QCD latent heat. (orig.)

QCD with jets and photons at ATLAS and CMS

CERN Document Server

AUTHOR|(INSPIRE)INSPIRE-00265099; The ATLAS collaboration

2017-01-01

A selection of recent QCD measurements by the ATLAS and CMS collaborations in final states with photons and jets is presented. New results with improved precision provide a probe of perturbative QCD, allowing to perform PDF fits and extracting the strong coupling constant $\\alpha_{S}$.

Charge correlations as definitive tests of QCD

International Nuclear Information System (INIS)

Maxwell, C.J.

1981-07-01

Certain weighted charge correlations are defined and it is shown how they can be used to measure properties of the gluon jet in the e + e - 3-jet final state. Properties are suggested which are indicative of the form of the QCD matrix element, the running coupling constant and value of Λ, and hence constitute definitive tests of QCD. The recent near tenfold increase in luminosity at PETRA should make such experimental tests possible in the near future. (author)

The structure of gluon radiation in QCD

International Nuclear Information System (INIS)

Parke, S.; Mangano, M.

1989-08-01

For massless QCD the hard scattering amplitudes are naturally written in terms of the dual color expansion. here I present this expansion for purely gluonic processes and processes involving quark-antiquark pairs and gluons. The properties of the sub-amplitudes as well as explicit algebraic expressions are given for a number of these processes. Also, I demonstrate how to recover massless QED amplitudes from the dual expansion of massless QCD. 16 refs., 3 figs., 1 tab

Assuming Regge trajectories in holographic QCD: from OPE to Chiral Perturbation Theory

CERN Document Server

Cappiello, Luigi; Greynat, David

2015-01-01

The Soft Wall model in holographic QCD has Regge trajectories but wrong operator product expansion (OPE) for the two-point vectorial QCD Green function. We correct analytically this problem and describe the axial sector and chiral symmetry breaking. The low energy chiral parameters, $F_{\\pi}$ and $L_{10}$ , are well described analytically by the model in terms of Regge spacing and QCD condensates. The model nicely supports and extends previous theoretical analyses advocating Digamma function to study QCD two-point functions in different momentum regions.

Effects of QCD equation of state on the stochastic gravitational wave background

Energy Technology Data Exchange (ETDEWEB)

Anand, Sampurn; Mohanty, Subhendra [Physical Research Laboratory, Ahmedabad 380009 (India); Dey, Ujjal Kumar, E-mail: sampurn@prl.res.in, E-mail: ujjal@cts.iitkgp.ernet.in, E-mail: mohanty@prl.res.in [Centre for Theoretical Studies, Indian Institute of Technology, Kharagpur 721302 (India)

2017-03-01

Cosmological phase transitions can be a source of Stochastic Gravitational Wave (SGW) background. Apart from the dynamics of the phase transition, the characteristic frequency and the fractional energy density Ω{sub gw} of the SGW depends upon the temperature of the transition. In this article, we compute the SGW spectrum in the light of QCD equation of state provided by the lattice results. We find that the inclusion of trace anomaly from lattice QCD, enhances the SGW signal generated during QCD phase transition by ∼ 50% and the peak frequency of the QCD era SGW are shifted higher by ∼ 25% as compared to the earlier estimates without trace anomaly. This result is extremely significant for testing the phase transition dynamics near QCD epoch.

Academic training: QCD: are we ready for the LHC

CERN Multimedia

2006-01-01

2006-2007 ACADEMIC TRAINING PROGRAMME LECTURE SERIES 4, 5, 6, 7 December, from 11:00 to 12:00 4, 5, 6 December - Main Auditorium, bldg. 500, 7 December - TH Auditorium, bldg. 4 - 3-006 QCD: are we ready for the LHC S. FRIXIONE / INFN, Genoa, Italy The LHC energy regime poses a serious challenge to our capability of predicting QCD reactions to the level of accuracy necessary for a successful programme of searches for physics beyond the Standard Model. In these lectures, I'll introduce basic concepts in QCD, and present techniques based on perturbation theory, such as fixed-order and resummed computations, and Monte Carlo simulations. I'll discuss applications of these techniques to hadron-hadron processes, concentrating on recent trends in perturbative QCD aimed at improving our understanding of LHC phenomenology. ENSEIGNEMENT ACADEMIQUE ACADEMIC TRAINING Françoise Benz 73127 academic.training@cern.ch If you wish to participate in one of the following courses, please tell to your supervisor and apply ...

Nucleon form factors and hidden symmetry in holographic QCD

International Nuclear Information System (INIS)

Hong, D.K.; Rho, M.; Yee, H.-U.; Yi, P.

2007-10-01

The vector dominance of the electromagnetic (EM) form factors both for mesons and baryons arises naturally in holographic QCD, where both the number of colors and the 't Hooft coupling are taken to be very large, offering a bona-fide derivation of the notion of vector dominance. The crucial ingredient for this is the infinite tower of vector mesons in the approximations made which share features that are characteristic of the quenched approximation in lattice QCD. We approximate the infinite sum by contributions from the lowest four vector mesons of the tower which turn out to saturate the charge and magnetic moment sum rules within a few % and compute them totally free of unknown parameters for momentum transfers Q 2 approx.= 1 GeV 2 . We identify certain observables that can be reliably computed within the approximations and others that are not, and discuss how the improvement of the latter can enable one to bring holographic QCD closer to QCD proper. (author)

A Precise determination of B(K) in quenched QCD

CERN Document Server

Dimopoulos, P.; Palombi, F.; Pena, C.; Sint, S.; Vladikas, A.

2006-01-01

The $B_K$ parameter is computed in quenched lattice QCD with Wilson twisted mass fermions. Two variants of tmQCD are used; in both of them the relevant $\\Delta S = 2$ four-fermion operator is renormalised multiplicatively. The renormalisation adopted is non-perturbative, with a Schroedinger functional renormalisation condition. Renormalisation group running is also non-perturbative, up to very high energy scales. In one of the two tmQCD frameworks the computations have been performed at the physical $K$-meson mass, thus eliminating the need of mass extrapolations. Simulations have been performed at several lattice spacings and the continuum limit was reached by combining results from both tmQCD regularisations. Finite volume effects have been partially checked and turned out to be small. Exploratory studies have also been performed with non-degenerate valence flavours. The final result for the RGI bag parameter, with all sources of uncertainty (except quenching) under control, is $\\hat B_K =0.789 \\pm 0.046$.

Freezing of the QCD coupling constant and the pion form factor

International Nuclear Information System (INIS)

Aguilar, A.C.; Mihara, A.; Natale, A.A.

2003-01-01

The possibility that the QCD coupling constant (α s ) has an infrared finite behavior (freezing) has been extensively studied in recent years. We compare phenomenological values of the 'frozen' the QCD running coupling between different classes of solutions obtained through non-perturbative Schwinger-Dyson Equations. With these solutions were computed QCD predictions for the asymptotic pion form factor which, in turn, were compared with experiment. (author)

QCD physics with the CMS experiment

CERN Document Server

Cerci, Salim

2017-01-01

Jets which are the signatures of quarks and gluons in the detector can be described by Quantum Chromodynamics (QCD) in terms of parton-parton scattering. Jets are abundantly produced at the LHC's high energy scales. Measurements of inclusive jets, dijets and multijets can be used to test perturbative QCD predictions and to constrain parton distribution functions (PDF), as well as to measure the strong coupling constant $\\alpha_{S}$. The measurements use the samples of proton-proton collisions collected with the CMS detector at the LHC at various center-of-mass energies of 7, 8 and 13 TeV.

QCD Physics with the CMS Experiment

Science.gov (United States)

Cerci, S.

2017-12-01

Jets which are the signatures of quarks and gluons in the detector can be described by Quantum Chromodynamics (QCD) in terms of parton-parton scattering. Jets are abundantly produced at the LHC's high energy scales. Measurements of inclusive jets, dijets and multijets can be used to test perturbative QCD predictions and to constrain parton distribution functions (PDF), as well as to measure the strong coupling constant αS . The measurements use the samples of proton-proton collisions collected with the CMS detector at the LHC at various center-of-mass energies of 7, 8 and 13 TeV.

Renormalization of Hamiltonian QCD

International Nuclear Information System (INIS)

Andrasi, A.; Taylor, John C.

2009-01-01

We study to one-loop order the renormalization of QCD in the Coulomb gauge using the Hamiltonian formalism. Divergences occur which might require counter-terms outside the Hamiltonian formalism, but they can be cancelled by a redefinition of the Yang-Mills electric field.

QCD propagators and vertices from lattice QCD (in memory of Michael Müller-Preußker

Directory of Open Access Journals (Sweden)

Sternbeck André

2017-01-01

Full Text Available We review lattice calculations of the elementary Greens functions of QCD with a special emphasis on the Landau gauge. These lattice results have been of interest to continuum approaches to QCD over the past 20 years. They are used as reference for Dyson-Schwinger- and functional renormalization group equation calculations as well as for hadronic bound state equations. The lattice provides low-energy data for propagators and three-point vertices in Landau gauge at zero and finite temperature even including dynamical fermions. We summarize Michael Müller-Preußker’s important contributions to this field and put them into the perspective of his other research interests.

QCD tests at CDF

International Nuclear Information System (INIS)

Kovacs, E.

1996-02-01

We present results for the inclusive jet cross section and the dijet mass distribution. The inclusive cross section and dijet mass both exhibit significant deviations from the predictions of NLO QCD for jets with E T >200 GeV, or dijet masses > 400 GeV/c 2 . We show that it is possible, within a global QCD analysis that includes the CDF inclusive jet data, to modify the gluon distribution at high x. The resulting increase in the jet cross-section predictions is 25-35%. Owing to the presence of k T smearing effects, the direct photon data does not provide as strong a constraint on the gluon distribution as previously thought. A comparison of the CDF and UA2 jet data, which have a common range in x, is plagued by theoretical and experimental uncertainties, and cannot at present confirm the CDF excess or the modified gluon distribution

QCD and asymptotic freedom: Perspectives and prospects

International Nuclear Information System (INIS)

Wilczek, F.

1993-01-01

QCD is now a mature theory, and it is possible to begin to view its place in the conceptual universe of physics with an appropriate perspective. There is a certain irony in the achievements of QCD. For the problems which initially drove its development - specifically, the desire to understand in detail the force that holds atomic nuclei together, and later the desire to calculate the spectrum of hadrons and their interactions - only limited insight has been achieved. However, the author shall argue that QCD is actually more special and important a theory than one had any right to anticipate. In many ways, the importance of the solution transcends that of the original motivating problems. After elaborating on these quasiphilosophical remarks, he discusses two current frontiers of physics that illustrate the continuing vitality of the ideas. The recent wealth of beautiful precision experiments measuring the parameters of the standard model have made it possible to consider the unification of couplings in unprecedented quantitative detail. One central result emerging from these developments is a tantalizing hint of virtual supersymmetry. The possibility of phase transitions in matter at temperatures of order ∼ 10 2 MeV, governed by QCD dynamics, is of interest from several points of view. Finally, at the end, there is a brief discussion on the relation between scaling violations and running of the coupling

Conformal Symmetry as a Template for QCD

Energy Technology Data Exchange (ETDEWEB)

Brodsky, S

2004-08-04

Conformal symmetry is broken in physical QCD; nevertheless, one can use conformal symmetry as a template, systematically correcting for its nonzero {beta} function as well as higher-twist effects. For example, commensurate scale relations which relate QCD observables to each other, such as the generalized Crewther relation, have no renormalization scale or scheme ambiguity and retain a convergent perturbative structure which reflects the underlying conformal symmetry of the classical theory. The ''conformal correspondence principle'' also dictates the form of the expansion basis for hadronic distribution amplitudes. The AdS/CFT correspondence connecting superstring theory to superconformal gauge theory has important implications for hadron phenomenology in the conformal limit, including an all-orders demonstration of counting rules for hard exclusive processes as well as determining essential aspects of hadronic light-front wavefunctions. Theoretical and phenomenological evidence is now accumulating that QCD couplings based on physical observables such as {tau} decay become constant at small virtuality; i.e., effective charges develop an infrared fixed point in contradiction to the usual assumption of singular growth in the infrared. The near-constant behavior of effective couplings also suggests that QCD can be approximated as a conformal theory even at relatively small momentum transfer. The importance of using an analytic effective charge such as the pinch scheme for unifying the electroweak and strong couplings and forces is also emphasized.

Testing QCD in the non-perturbative regime

Energy Technology Data Exchange (ETDEWEB)

A.W. Thomas

2007-01-01

This is an exciting time for strong interaction physics. We have a candidate for a fundamental theory, namely QCD, which has passed all the tests thrown at it in the perturbative regime. In the non-perturbative regime it has also produced some promising results and recently a few triumphs but the next decade will see enormous progress in our ability to unambiguously calculate the consequences of non-perturbative QCD and to test those predictions experimentally. Amongst the new experimental facilities being constructed, the hadronic machines at JPARC and GSI-FAIR and the 12 GeV Upgrade at Jefferson Lab, the major new electromagnetic facility worldwide, present a beautifully complementary network aimed at producing precise new measurements which will advance our knowledge of nuclear systems and push our ability to calculate the consequences of QCD to the limit. We will first outline the plans at Jefferson Lab for doubling the energy of CEBAF. The new facility presents some wonderful opportunities for discovery in strong interaction physics, as well as beyond the standard model. Then we turn to the theoretical developments aimed at extracting precise results for physical hadron properties from lattice QCD simulations. This discussion will begin with classical examples, such as the mass of the nucleon and ?, before dealing with a very recent and spectacular success involving information extracted from modern parity violating electron scattering.

Conformal Symmetry as a Template for QCD

International Nuclear Information System (INIS)

Brodsky, S

2004-01-01

Conformal symmetry is broken in physical QCD; nevertheless, one can use conformal symmetry as a template, systematically correcting for its nonzero β function as well as higher-twist effects. For example, commensurate scale relations which relate QCD observables to each other, such as the generalized Crewther relation, have no renormalization scale or scheme ambiguity and retain a convergent perturbative structure which reflects the underlying conformal symmetry of the classical theory. The ''conformal correspondence principle'' also dictates the form of the expansion basis for hadronic distribution amplitudes. The AdS/CFT correspondence connecting superstring theory to superconformal gauge theory has important implications for hadron phenomenology in the conformal limit, including an all-orders demonstration of counting rules for hard exclusive processes as well as determining essential aspects of hadronic light-front wavefunctions. Theoretical and phenomenological evidence is now accumulating that QCD couplings based on physical observables such as τ decay become constant at small virtuality; i.e., effective charges develop an infrared fixed point in contradiction to the usual assumption of singular growth in the infrared. The near-constant behavior of effective couplings also suggests that QCD can be approximated as a conformal theory even at relatively small momentum transfer. The importance of using an analytic effective charge such as the pinch scheme for unifying the electroweak and strong couplings and forces is also emphasized

Lattice QCD for Baryon Rich Matter – Beyond Taylor Expansions

Energy Technology Data Exchange (ETDEWEB)

Bornyakov, V. [ITEP, B. Cheremushkinskaya 25, Moscow, 117218 (Russian Federation); School of Biomedicine, Far Eastern Federal University, Sukhanova 8, Vladivostok 690950 (Russian Federation); Boyda, D. [School of Biomedicine, Far Eastern Federal University, Sukhanova 8, Vladivostok 690950 (Russian Federation); Goy, V. [School of Natural Sciences, Far Eastern Federal University, Sukhanova 8, Vladivostok 690950 (Russian Federation); Molochkov, A. [School of Biomedicine, Far Eastern Federal University, Sukhanova 8, Vladivostok 690950 (Russian Federation); Nakamura, A. [School of Biomedicine, Far Eastern Federal University, Sukhanova 8, Vladivostok 690950 (Russian Federation); Research Center for Nuclear Physics (RCNP), Osaka University, Ibaraki, Osaka, 567-0047 (Japan); Theoretical Research Division, Nishina Center, RIKEN, Wako 351-0198 (Japan); Nikolaev, A. [School of Biomedicine, Far Eastern Federal University, Sukhanova 8, Vladivostok 690950 (Russian Federation); Zakharov, V.I. [ITEP, B. Cheremushkinskaya 25, Moscow, 117218 (Russian Federation); School of Biomedicine, Far Eastern Federal University, Sukhanova 8, Vladivostok 690950 (Russian Federation); Moscow Inst Phys & Technol, Dolgoprudny, Moscow Region, 141700 (Russian Federation)

2016-12-15

We discuss our study for exploring the QCD phase diagram based on the lattice QCD. To go beyond the Taylor expansion and to reach higher density regions, we employ the canonical approach. In order to produce lattice data which meet experimental situation as much as possible, we propose a canonical approach with the charge and baryon number. We present our lattice QCD GPU code for this project which employs the clover improved Wilson fermions and Iwasaki gauge action to investigate pure imaginary chemical potential.

Lattice QCD for Baryon Rich Matter – Beyond Taylor Expansions

International Nuclear Information System (INIS)

Bornyakov, V.; Boyda, D.; Goy, V.; Molochkov, A.; Nakamura, A.; Nikolaev, A.; Zakharov, V.I.

2016-01-01

We discuss our study for exploring the QCD phase diagram based on the lattice QCD. To go beyond the Taylor expansion and to reach higher density regions, we employ the canonical approach. In order to produce lattice data which meet experimental situation as much as possible, we propose a canonical approach with the charge and baryon number. We present our lattice QCD GPU code for this project which employs the clover improved Wilson fermions and Iwasaki gauge action to investigate pure imaginary chemical potential.

Strong evidence for spontaneous chiral symmetry breaking in (quenched) QCD

International Nuclear Information System (INIS)

Barbour, I.M.; Gibbs, P.; Schierholz, G.; Teper, M.; Gilchrist, J.P.; Schneider, H.

1983-09-01

We calculate the chiral condensate for all quark masses using Kogut-Susskind fermions in lattice-regularized quenched QCD. The large volume behaviour of at small quark masses demonstrates that the explicit U(1) chiral symmetry is spontaneously broken. We perform the calculation for β = 5.1 to 5.9 and find very good continuum renormalization group behaviour. We infer that the spontaneous breaking we observe belongs to continuum QCD. This constitutes the first unambiguous demonstration of spontaneous chiral symmetry breaking in continuum quenched QCD. (orig.)

Higher order corrections to mixed QCD-EW contributions to Higgs boson production in gluon fusion

Science.gov (United States)

Bonetti, Marco; Melnikov, Kirill; Tancredi, Lorenzo

2018-03-01

We present an estimate of the next-to-leading-order (NLO) QCD corrections to mixed QCD-electroweak contributions to the Higgs boson production cross section in gluon fusion, combining the recently computed three-loop virtual corrections and the approximate treatment of real emission in the soft approximation. We find that the NLO QCD corrections to the mixed QCD-electroweak contributions are nearly identical to NLO QCD corrections to QCD Higgs production. Our result confirms an earlier estimate of these O (α αs2) effects by Anastasiou et al. [J. High Energy Phys. 04 (2009) 003, 10.1088/1126-6708/2009/04/003] and provides further support for the factorization approximation of QCD and electroweak corrections.

Novel Aspects of Hard Diffraction in QCD

International Nuclear Information System (INIS)

Brodsky, Stanley J.

2005-01-01

Initial- and final-state interactions from gluon-exchange, normally neglected in the parton model have a profound effect in QCD hard-scattering reactions, leading to leading-twist single-spin asymmetries, diffractive deep inelastic scattering, diffractive hard hadronic reactions, and nuclear shadowing and antishadowing--leading-twist physics not incorporated in the light-front wavefunctions of the target computed in isolation. I also discuss the use of diffraction to materialize the Fock states of a hadronic projectile and test QCD color transparency

Three-Prong Distribution of Massive Narrow QCD Jets

CERN Document Server

Field, Matan; Kosower, David A; Mannelli, Lorenzo; Perez, Gilad

2013-01-01

We study the planar-flow distributions of narrow, highly boosted, massive QCD jets. Using the factorization properties of QCD in the collinear limit, we compute the planar-flow jet function from the one-to-three splitting function at tree-level. We derive the leading-log behavior of the jet function analytically. We also compare our semi-analytic jet function with parton-shower predictions using various generators.

Observables of QCD diffraction

Science.gov (United States)

Mieskolainen, Mikael; Orava, Risto

2017-03-01

A new combinatorial vector space measurement model is introduced for soft QCD diffraction. The model independent mathematical construction resolves experimental complications; the theoretical framework of the approach includes the Good-Walker view of diffraction, Regge phenomenology together with AGK cutting rules and random fluctuations.

Recent development and perspectives of machines for lattice QCD

International Nuclear Information System (INIS)

Lippert, Th.

2004-01-01

I am going to highlight recent progress in cluster computer technology and to assess status and prospects of cluster computers for lattice QCD with respect to the development of QCDOC and apeNEXT. Taking the LatFor test case, I specify a 512-processor QCD-cluster better than 1$/Mflops

Statistical analyses for the purpose of an early detection of global and regional climate change due to the anthropogenic greenhouse effect; Statistische Analysen zur Frueherkennung globaler und regionaler Klimaaenderungen aufgrund des anthropogenen Treibhauseffektes

Energy Technology Data Exchange (ETDEWEB)

Grieser, J.; Staeger, T.; Schoenwiese, C.D.

2000-03-01

The report answers the question where, why and how different climate variables have changed within the last 100 years. The analyzed variables are observed time series of temperature (mean, maximum, minimum), precipitation, air pressure, and water vapour pressure in a monthly resolution. The time series are given as station data and grid box data as well. Two kinds of time-series analysis are performed. The first is applied to find significant changes concerning mean and variance of the time series. Thereby also changes in the annual cycle and frequency of extreme events arise. The second approach is used to detect significant spatio-temporal patterns in the variations of climate variables, which are most likely driven by known natural and anthropogenic climate forcings. Furtheron, an estimation of climate noise allows to indicate regions where certain climate variables have changed significantly due to the enhanced anthropogenic greenhouse effect. (orig.) [German] Der Bericht gibt Antwort auf die Frage, wo sich welche Klimavariable wie und warum veraendert hat. Ausgangspunkt der Analyse sind huntertjaehrige Zeitreihen der Temperatur (Mittel, Maximum, Minimum), des Niederschlags, Luftdrucks und Wasserdampfpartialdrucks in monatlicher Aufloesung. Es wurden sowohl Stationsdaten als auch Gitterpunktdaten verwendet. Mit Hilfe der strukturorientierten Zeitreihenzerlegung wurden signifikankte Aenderungen im Mittel und in der Varianz der Zeitreihen gefunden. Diese betreffen auch Aenderungen im Jahresgang und in der Haeufigkeit extremer Ereignisse. Die ursachenorientierte Zeitreihenzerlegung selektiert signifikante raumzeitliche Variationen der Klimavariablen, die natuerlichen bzw. anthropogenen Klimaantrieben zugeordnet werden koennen. Eine Abschaetzung des Klimarauschens erlaubt darueber hinaus anzugeben, wo und wie signifikant der anthropogene Treibhauseffekt welche Klimavariablen veraendert hat. (orig.)

Non-perturbative supersymmetry anomaly in supersymmetric QCD

International Nuclear Information System (INIS)

Shamir, Y.

1991-03-01

The zero modes of the Dirac operator in an instanton and other topologically non-trivial backgrounds are unstable in a large class of massless or partially massless supersymmetric gauge theories. We show that under a generic perturbation of the scalar fields all zero modes become resonances, and discuss the ensuing breakdown of conventional perturbation theory. As a result, despite of the presence of massless fermions, the field theoretic tunneling amplitude is not suppressed. In massless supersymmetric QCD with N c ≤ N f the effective potential is found to be negative and monotonically increasing in the weak coupling regime for scalar VEVs which lie on the perturbatively flat directions. Consequently, massless supersymmetric QCD with N c ≤ N f exhibits a non-perturbative supersymmetry anomaly and exists in a strongly interacting phase which closely resembles ordinary QCD. The same conclusions apply if small masses are added to the lagrangian and the massless limit is smooth. (author). 21 refs, 5 figs

Light-front QCD. II. Two-component theory

International Nuclear Information System (INIS)

Zhang, W.; Harindranath, A.

1993-01-01

The light-front gauge A a + =0 is known to be a convenient gauge in practical QCD calculations for short-distance behavior, but there are persistent concerns about its use because of its ''singular'' nature. The study of nonperturbative field theory quantizing on a light-front plane for hadronic bound states requires one to gain a priori systematic control of such gauge singularities. In the second paper of this series we study the two-component old-fashioned perturbation theory and various severe infrared divergences occurring in old-fashioned light-front Hamiltonian calculations for QCD. We also analyze the ultraviolet divergences associated with a large transverse momentum and examine three currently used regulators: an explicit transverse cutoff, transverse dimensional regularization, and a global cutoff. We discuss possible difficulties caused by the light-front gauge singularity in the applications of light-front QCD to both old-fashioned perturbative calculations for short-distance physics and upcoming nonperturbative investigations for hadronic bound states

Early Run 2 Hard QCD Results from the ATLAS Collaboration

Directory of Open Access Journals (Sweden)

Orlando Nicola

2016-01-01

Full Text Available We provide an overview of hard QCD results based on data collected with the ATLAS detector in proton-proton collision at √s = 13 TeV at the Large Hadron Collider. The production of high transverse momentum jets, photons and photon-pairs were studied; the inclusive jet cross section is found to agree well with the prediction of perturbative QCD calculations performed at next-to-leading accuracy. The production cross sections for W and Z bosons in their e and μ decays was measured; in general, agreement is found with the expectation of next-to-next-to leading order QCD calculations and interesting sensitivities to the proton structure functions are already observed. The top production cross sections were measured in different top decay channels and found to agree with the state of the art QCD predictions.

Elementary amplitudes from full QCD and the stochastic vacuum model

International Nuclear Information System (INIS)

Martini, A.F.; Menon, M.J.

2002-01-01

In a previous work, making use of the gluon gauge-invariant two-point correlation function determined from lattice QCD in the quenched approximation and the stochastic vacuum model, we determined the elementary (parton-parton) scattering amplitude in the momentum transfer space. In this communication we compute the elementary amplitude from new lattice QCD calculations that include the effects of dynamical fermions (full QCD). The main conclusion is that the inclusion of dynamical fermions leads to a normalized elementary amplitude that decreases more quickly with the momentum transfer than that in the quenched approximation. (author)

Searching for QCD-violations in deep inelastic structure functions

International Nuclear Information System (INIS)

Avilez, C.; Garcia Canal, C.A.; Gay Ducati, M.B.; Martins Simoes, J.A.

1979-01-01

Due to the difficulties in extracting information from data of different experiments, a systematic procedure to look for QCD-violations in the Q 2 -dependence of F 2 is discussed. The validity of the Callan-Gross relation is assumed. The proposal is illustrated in a well-known model which implies QCD-violations

Perturbative QCD and exclusive processes

International Nuclear Information System (INIS)

Bennett, J.; Hawes, F.; Zhao, M.; Zyla, P.

1991-01-01

The authors discuss perturbation theory as applied to particle physics calculations. In particle physics one is generally interested in the scattering amplitude for a system going from some initial state to a final state. The intermediate state or states are unknown. To get the scattering amplitude it is necessary to sum the contributions from processes which pass through all possible intermediate states. Intermediate states involve the exchange of intermediate vector bosons between the particles, and with this interaction is associated a coupling constant α. Each additional boson exchange involves an additional contribution of α to the coupling. If α is less than 1, one can see that the relative contribution of higher order processes is less and less important as α falls. In QCD the gluons serve as the intermediate vector bosons exchanged by quarks and gluons, and the interaction constant is not really a constant, but depends upon the distance between the particles. At short distances the coupling is small, and one can assume perturbative expansions may converge rapidly. Exclusive scattering processes, as opposed to inclusive, are those in which all of the final state products are detected. The authors then discuss the application of perturbative QCD to the deuteron. The issues of chiral conservation and color transparancy are also discussed, in the scheme of large Q 2 interations, where perturbative QCD should be applicable

QCD ghost f(T)-gravity model

Energy Technology Data Exchange (ETDEWEB)

Karami, K.; Abdolmaleki, A.; Asadzadeh, S. [University of Kurdistan, Department of Physics, Sanandaj (Iran, Islamic Republic of); Safari, Z. [Research Institute for Astronomy and Astrophysics of Maragha (RIAAM), Maragha (Iran, Islamic Republic of)

2013-09-15

Within the framework of modified teleparallel gravity, we reconstruct a f(T) model corresponding to the QCD ghost dark energy scenario. For a spatially flat FRW universe containing only the pressureless matter, we obtain the time evolution of the torsion scalar T (or the Hubble parameter). Then, we calculate the effective torsion equation of state parameter of the QCD ghost f(T)-gravity model as well as the deceleration parameter of the universe. Furthermore, we fit the model parameters by using the latest observational data including SNeIa, CMB and BAO data. We also check the viability of our model using a cosmographic analysis approach. Moreover, we investigate the validity of the generalized second law (GSL) of gravitational thermodynamics for our model. Finally, we point out the growth rate of matter density perturbation. We conclude that in QCD ghost f(T)-gravity model, the universe begins a matter dominated phase and approaches a de Sitter regime at late times, as expected. Also this model is consistent with current data, passes the cosmographic test, satisfies the GSL and fits the data of the growth factor well as the {Lambda}CDM model. (orig.)

Heavy quark production processes in QCD

International Nuclear Information System (INIS)

Brodsky, S.J.; Gunion, J.F.

1984-12-01

We have identified two novel effects in QCD, each of which acts to enhance the production of heavy quark and supersymmetric particles beyond what is conventionally expected from gluon fusion. Both effects are present in QED, but are compounded in QCD because of the increased number of diagrams and the much larger coupling constant. The intrinsic charm quark distribution in the nucleon could account for the observed enhancements of the charm structure function at large x and features of the charm production data but this mechanism is relatively suppressed for heavier systems. Prebinding distortion of the fusion cross section is, however, likely to be significant for the production at low p/sub T/ of all particles containing heavy colored constituents. At this stage the QCD calculations are highly model dependent although they agree with the general properties which can be inferred from the operator product expansion in the heavy quark mass. Much more theoretical analysis of these effects is clearly needed. It is also clear that much more experimental work is necessary to extend and confirm the reported anomalous heavy quark signals. 22 references

Full CKM matrix with lattice QCD

Energy Technology Data Exchange (ETDEWEB)

Okamoto, Masataka; /Fermilab

2004-12-01

The authors show that it is now possible to fully determine the CKM matrix, for the first time, using lattice QCD. |V{sub cd}|, |V{sub cs}|, |V{sub ub}|, |V{sub cb}| and |V{sub us}| are, respectively, directly determined with the lattice results for form factors of semileptonic D {yields} {pi}lv, D {yields} Klv, B {yields} {pi}lv, B {yields} Dlv and K {yields} {pi}lv decays. The error from the quenched approximation is removed by using the MILC unquenced lattice gauge configurations, where the effect of u, d and s quarks is included. The error from the ''chiral'' extrapolation (m{sub l} {yields} m{sub ud}) is greatly reduced by using improved staggered quarks. The accuracy is comparable to that of the Particle Data Group averages. In addition, |V{sub ud}|, |V{sub ts}|, |V{sub ts}| and |V{sub td}| are determined by using unitarity of the CKM matrix and the experimental result for sin (2{beta}). In this way, they obtain all 9 CKM matrix elements, where the only theoretical input is lattice QCD. They also obtain all the Wolfenstein parameters, for the first time, using lattice QCD.

QCD bosonization and the meson effective action

International Nuclear Information System (INIS)

Praschifka, J.; Roberts, C.D.; Cahill, R.T.

1987-01-01

A bosonization of quantum chromodynamics (QCD) is employed to derive a meson effective action, thus providing a direct link between QCD and meson phenomenology. As an example of this approach expressions are obtained for the meson parameters associated with the analysis of ω→3π decay. The bosonization also directly motivates a divergence-free, global color-symmetry model for mesons, which is seen to be a generalization of various phenomenological models. Good estimates are obtained for the values of several of the meson parameters

OpenQ∗D simulation code for QCD+QED

DEFF Research Database (Denmark)

Campos, Isabel; Fritzsch, Patrick; Hansen, Martin

2018-01-01

The openQ∗D code for the simulation of QCD+QED with C∗ boundary conditions is presented. This code is based on openQCD-1.6, from which it inherits the core features that ensure its efficiency: the locally-deflated SAP-preconditioned GCR solver, the twisted-mass frequency splitting of the fermion....... An alpha version of this code is publicly available and can be downloaded from http://rcstar.web.cern.ch/....

Resolution of ambiguities in perturbative QCD

International Nuclear Information System (INIS)

Nakkagawa, Hisao; Niegawa, Akira.

1984-01-01

In the perturbative QCD analyses of the deeply inelastic processes, the coupling constant depends on at least two mass-scales, the renormalization scale and the factorization scale. By integrating the coupled renormalization group equations with respect to these two mass-scales, the running coupling constant is defined. A perturbative approximation then introduces a new ambiguity, the integration-path dependence, into the theory. We show that the problem of this new ambiguity is resolved by imposing Stevenson's principle of minimal sensitivity. Together with the analogous analysis of the operator matrix element or the cut vertex, we can completely solve the problem of getting an unambiguous perturbative QCD prediction. (author)

Quasiparticles in QCD thermodynamics and applications

International Nuclear Information System (INIS)

Schneider, R.A.; Renk, T.

2002-01-01

We propose a novel quasiparticle interpretation of the equation of state of deconfined QCD at finite temperature. Using appropriate thermal masses, we introduce a phenomenological parametrization of the onset of confinement in the vicinity of the phase transition. Lattice results of the energy density, the pressure and the interaction measure of pure SU(3) gauge theory are well reproduced. A relation between the thermal energy density of the Yang-Mills vacuum and the chromomagnetic condensate left angle B 2 right angle T is found. We also present the two flavour QCD equation of state for realistic quark masses and apply the model to dilepton production in ultrarelativistic heavy-ion collisions. (orig.)

Automation of one-loop QCD corrections

CERN Document Server

Hirschi, Valentin; Frixione, Stefano; Garzelli, Maria Vittoria; Maltoni, Fabio; Pittau, Roberto

2011-01-01

We present the complete automation of the computation of one-loop QCD corrections, including UV renormalization, to an arbitrary scattering process in the Standard Model. This is achieved by embedding the OPP integrand reduction technique, as implemented in CutTools, into the MadGraph framework. By interfacing the tool so constructed, which we dub MadLoop, with MadFKS, the fully automatic computation of any infrared-safe observable at the next-to-leading order in QCD is attained. We demonstrate the flexibility and the reach of our method by calculating the production rates for a variety of processes at the 7 TeV LHC.

Massively Parallel QCD

International Nuclear Information System (INIS)

Soltz, R; Vranas, P; Blumrich, M; Chen, D; Gara, A; Giampap, M; Heidelberger, P; Salapura, V; Sexton, J; Bhanot, G

2007-01-01

The theory of the strong nuclear force, Quantum Chromodynamics (QCD), can be numerically simulated from first principles on massively-parallel supercomputers using the method of Lattice Gauge Theory. We describe the special programming requirements of lattice QCD (LQCD) as well as the optimal supercomputer hardware architectures that it suggests. We demonstrate these methods on the BlueGene massively-parallel supercomputer and argue that LQCD and the BlueGene architecture are a natural match. This can be traced to the simple fact that LQCD is a regular lattice discretization of space into lattice sites while the BlueGene supercomputer is a discretization of space into compute nodes, and that both are constrained by requirements of locality. This simple relation is both technologically important and theoretically intriguing. The main result of this paper is the speedup of LQCD using up to 131,072 CPUs on the largest BlueGene/L supercomputer. The speedup is perfect with sustained performance of about 20% of peak. This corresponds to a maximum of 70.5 sustained TFlop/s. At these speeds LQCD and BlueGene are poised to produce the next generation of strong interaction physics theoretical results

Efficacité des néonicotinoïdes et des pyréthrinoïdes utilisés contre le ...

African Journals Online (AJOL)

Efficacité des néonicotinoïdes et des pyréthrinoïdes utilisés contre le foreur des tiges du cacaoyer ( Eulophonotus myrmeleon Felder : Lepidoptera, Cossidae). Implications dans la stratégie de protection de la cacaoculture en Côte d'Ivoire.

The QCD form factor of massive quarks and applications

International Nuclear Information System (INIS)

Moch, S.

2009-11-01

We review the electromagnetic form factor of heavy quarks with emphasis on the QCD radiative corrections at two-loop order in the perturbative expansion. We discuss important properties of the heavy-quark form factor such as its exponentiation in the high-energy limit and its role in QCD factorization theorems for massive n-parton amplitudes. (orig.)

Two-dimensional QCD as a model for strong interaction

International Nuclear Information System (INIS)

Ellis, J.

1977-01-01

After an introduction to the formalism of two-dimensional QCD, its applications to various strong interaction processes are reviewed. Among the topics discussed are spectroscopy, deep inelastic cross-sections, ''hard'' processes involving hadrons, ''Regge'' behaviour, the existence of the Pomeron, and inclusive hadron cross-sections. Attempts are made to abstracts features useful for four-dimensional QCD phenomenology. (author)

QCD in gauge-boson production at the LHC

CERN Document Server

Schott, Matthias; The ATLAS collaboration

2018-01-01

Measurements of the Drell-Yan production of W and Z/gamma* bosons at the LHC provide a benchmark of our understanding of perturbative QCD and probe the proton structure in a unique way. The ATLAS and CMS collaborations have performed several high precision measurements at different center-of-mass energies, ranging from single to triple differential cross sections. These measurements are the key in improving physics modelling uncertainties of electroweak precision measurements at the LHC. Moreover, perturbative QCD can be tested further in a multi-scale environment, when studying the production of jets in association with single and di-bosons final states. In this talk, we review the latest measurements, discuss the compatibility between the experiments and compare the results to the state-of-the-art QCD calculations and Monte Carlo simulations, as well their potential impact on improving our understanding PDFs.

Exclusive hadronic and nuclear processes in QCD

International Nuclear Information System (INIS)

Brodsky, S.J.

1985-12-01

Hadronic and nuclear processes are covered, in which all final particles are measured at large invariant masses compared with each other, i.e., large momentum transfer exclusive reactions. Hadronic wave functions in QCD and QCD sum rule constraints on hadron wave functions are discussed. The question of the range of applicability of the factorization formula and perturbation theory for exclusive processes is considered. Some consequences of quark and gluon degrees of freedom in nuclei are discussed which are outside the usual domain of traditional nuclear physics. 44 refs., 7 figs

QCD unitarity constraints on Reggeon Field Theory

Energy Technology Data Exchange (ETDEWEB)

Kovner, Alex [Physics Department, University of Connecticut,2152 Hillside Road, Storrs, CT 06269 (United States); Levin, Eugene [Departemento de Física, Universidad Técnica Federico Santa María,and Centro Científico-Tecnológico de Valparaíso,Avda. Espana 1680, Casilla 110-V, Valparaíso (Chile); Department of Particle Physics, Tel Aviv University,Tel Aviv 69978 (Israel); Lublinsky, Michael [Physics Department, Ben-Gurion University of the Negev,Beer Sheva 84105 (Israel); Physics Department, University of Connecticut,2152 Hillside Road, Storrs, CT 06269 (United States)

2016-08-04

We point out that the s-channel unitarity of QCD imposes meaningful constraints on a possible form of the QCD Reggeon Field Theory. We show that neither the BFKL nor JIMWLK nor Braun’s Hamiltonian satisfy the said constraints. In a toy, zero transverse dimensional case we construct a model that satisfies the analogous constraint and show that at infinite energy it indeed tends to a “black disk limit' as opposed to the model with triple Pomeron vertex only, routinely used as a toy model in the literature.

QCD unitarity constraints on Reggeon Field Theory

International Nuclear Information System (INIS)

Kovner, Alex; Levin, Eugene; Lublinsky, Michael

2016-01-01

We point out that the s-channel unitarity of QCD imposes meaningful constraints on a possible form of the QCD Reggeon Field Theory. We show that neither the BFKL nor JIMWLK nor Braun’s Hamiltonian satisfy the said constraints. In a toy, zero transverse dimensional case we construct a model that satisfies the analogous constraint and show that at infinite energy it indeed tends to a “black disk limit' as opposed to the model with triple Pomeron vertex only, routinely used as a toy model in the literature.

Measuring infrared contributions to the QCD pressure

CERN Document Server

Kajantie, Keijo; Rummukainen, K; Schröder, Y

2002-01-01

For the pressure (or free energy) of QCD, four-dimensional (4d) lattice data is available at zero baryon density up to a few times the critical temperature $T_c$. Perturbation theory, on the other hand, has serious convergence problems even at very high temperatures. In a combined analytical and three-dimensional (3d) lattice method, we show that it is possible to compute the QCD pressure from about $2 T_c$ to infinity. The numerical accuracy is good enough to resolve in principle, e.g., logarithmic contributions related to 4-loop perturbation theory.

Automation of NLO QCD and EW corrections with Sherpa and Recola

Energy Technology Data Exchange (ETDEWEB)

Biedermann, Benedikt; Denner, Ansgar; Pellen, Mathieu [Universitaet Wuerzburg, Institut fuer Theoretische Physik und Astrophysik, Wuerzburg (Germany); Braeuer, Stephan; Schumann, Steffen [Georg-August Universitaet Goettingen, II. Physikalisches Institut, Goettingen (Germany); Thompson, Jennifer M. [Universitaet Heidelberg, Institut fuer Theoretische Physik, Heidelberg (Germany)

2017-07-15

This publication presents the combination of the one-loop matrix-element generator Recola with the multipurpose Monte Carlo program Sherpa. Since both programs are highly automated, the resulting Sherpa +Recola framework allows for the computation of - in principle - any Standard Model process at both NLO QCD and EW accuracy. To illustrate this, three representative LHC processes have been computed at NLO QCD and EW: vector-boson production in association with jets, off-shell Z-boson pair production, and the production of a top-quark pair in association with a Higgs boson. In addition to fixed-order computations, when considering QCD corrections, all functionalities of Sherpa, i.e. particle decays, QCD parton showers, hadronisation, underlying events, etc. can be used in combination with Recola. This is demonstrated by the merging and matching of one-loop QCD matrix elements for Drell-Yan production in association with jets to the parton shower. The implementation is fully automatised, thus making it a perfect tool for both experimentalists and theorists who want to use state-of-the-art predictions at NLO accuracy. (orig.)

Coherent-state representation for the QCD ground state

International Nuclear Information System (INIS)

Celenza, L.S.; Ji, C.; Shakin, C.M.

1987-01-01

We make use of the temporal gauge to construct a coherent state which is meant to describe the gluon condensate in the QCD vacuum under the assumption that the condensate is in a zero-momentum mode. The state so constructed is a color singlet and will yield finite, nonperturbative vacuum expectation values such as . (This matrix element is found to have a value of about 0.012 GeV 4 in QCD sum-rule studies.)

Is QCD at Small X a String Theory?

Science.gov (United States)

Peschanski, R.

Using the dipole picture describing the 1/NC limit of QCD at small x and the conformal invariance properties of the BFKL kernel in transverse coordinate space, we show that the 1→p dipole densities can be expressed in terms of dual Shapiro-Virasoro amplitudes B2p+2 and their generalization including non-zero conformal spins. We discuss the possibility of an effective closed string theory of interacting QCD dipoles.

The Pomeron and hadrons through infra-red analysis of QCD

International Nuclear Information System (INIS)

White, A.R.

1981-01-01

Infra-red analysis of QCD in the Regge limit is argued to lead to confinement with chiral symmetry breaking. The resulting Pomeron depends strongly on the centre of the gauge group with SU(3) colour producing uniquely the experimentally observed even signature, factorizing, Pomeron. The critical Pomeron (asymptotic rising cross-sections) occurs when QCD is saturated with quarks. New calculations are reviewed showing strong evidence for the emergence of the critical Pomeron diffraction peak at present accelerator energies. This leads to exciting predictions for diffraction scattering at p antip collider energies which could become the most precise experimental confirmation of QCD

Quark–hadron phase structure, thermodynamics, and magnetization of QCD matter

Science.gov (United States)

Nasser Tawfik, Abdel; Magied Diab, Abdel; Hussein, M. T.

2018-05-01

The SU(3) Polyakov linear-sigma model (PLSM) is systematically implemented to characterize the quark-hadron phase structure and to determine various thermodynamic quantities and the magnetization of quantum chromodynamic (QCD) matter. Using mean-field approximation, the dependence of the chiral order parameter on a finite magnetic field is also calculated. Under a wide range of temperatures and magnetic field strengths, various thermodynamic quantities including trace anomaly, speed of sound squared, entropy density, and specific heat are presented, and some magnetic properties are described as well. Where available these results are compared to recent lattice QCD calculations. The temperature dependence of these quantities confirms our previous finding that the transition temperature is reduced with the increase in the magnetic field strength, i.e. QCD matter is characterized by an inverse magnetic catalysis. Furthermore, the temperature dependence of the magnetization showing that QCD matter has paramagnetic properties slightly below and far above the pseudo-critical temperature is confirmed as well. The excellent agreement with recent lattice calculations proves that our QCD-like approach (PLSM) seems to possess the correct degrees of freedom in both the hadronic and partonic phases and describes well the dynamics deriving confined hadrons to deconfined quark-gluon plasma.

Santé des adolescents et des jeunes au Burkina Faso : état des ...

African Journals Online (AJOL)

Il s'est agi d'une étude évaluative ayant utilisé une revue documentaire associée à une interview des acteurs clés et un atelier de validation et d'identification des interventions pertinentes pour un plan stratégique national. La situation de la santé des adolescents et des jeunes est caractérisée par des grossesses précoces ...

QCD under extreme conditions. Inhomogeneous condensation

Energy Technology Data Exchange (ETDEWEB)

Heinz, Achim

2014-10-15

Almost 40 years after the first publication on the phase diagram of quantum chromodynamics (QCD) big progress has been made but many questions are still open. This work covers several aspects of low-energy QCD and introduces advanced methods to calculate selected parts of the QCD phase diagram. Spontaneous chiral symmetry breaking as well as its restoration is a major aspect of QCD. Two effective models, the Nambu-Jona-Lasinio (NJL) model and the linear σ-model, are widely used to describe the QCD chiral phase transition. We study the large-N{sub c} behavior of the critical temperature T{sub c} for chiral symmetry restoration in the framework of both models. While in the NJL model T{sub c} is independent of N{sub c} (and in agreement with the expected QCD scaling), the scaling behavior in the linear σ-model reads T{sub c} ∝ N{sup 1/2}{sub c}. However, this mismatch can be corrected: phenomenologically motivated temperature-dependent parameters or the extension with the Polyakov-loop renders the scaling in the linear σ-model compatible with the QCD scaling. The requirement that the chiral condensate which is the order parameter of the chiral symmetry is constant in space is too restrictive. Recent studies on inhomogeneous chiral condensation in cold, dense quark matter suggest a rich crystalline structure. These studies feature models with quark degrees of freedom. In this thesis we investigate the formation of the chiral density wave (CDW) in the framework of the so-called extended linear sigma model (eLSM) at high densities and zero temperature. The eLSM is a modern development of the linear σ-model which contains scalar, pseudoscalar, vector, as well as axial-vector mesons, and in addition, a light tetraquark state. The nucleon and its chiral partner are introduced as parity doublets in the mirror assignment. The model describes successfully the vacuum phenomenology and nuclear matter ground-state properties. As a result we find that an inhomogeneous phase

La fabrique des sciences des institutions aux pratiques

CERN Document Server

Benninghoff, Martin; Crettaz von Roten, Fabienne; Merz, Martina

2006-01-01

Aujourd'hui, les façons de produire, d'organiser, d'évaluer et d'utiliser les savoirs sont en profond débat. De plus en plus, l'Etat, la société civile et l'économie tentent d'influencer les activités des universités et des laboratoires de recherche. Ces développements mettent à l'épreuve tout à la fois les fondements des systèmes d'enseignement supérieur et de recherche, l'autonomie des institutions scientifiques, la définition des frontières des savoirs et l'acceptation des sciences. Dans des contextes suisses et européens, cet ouvrage s'intéresse aux manières dont les sciences et les technologies sont fabriquées, en analysant leurs institutions et les pratiques. A partir d'une approche relationnelle, les sciences et les technologies sont conçues comme des phénomènes profondément sociaux, culturels et politiques. Une telle démarche déstabilise les visions parfois idéalisées et stéréotypées de la construction des savoirs. Des études de cas détaillées décrivent des phénomè...

Jets and tests of qcd in e+ e- experiments

International Nuclear Information System (INIS)

Marshall, R.

This talk presents the current status of QCD tests using PETRA data. The paper is divided into three easy sections. The first section covers essentially qualitative comparisons using Q plots, thrust and P(T) distributions and energy or momentum flow. The second section describes the quantitative determination of (alpha sub s), and the third section covers the scalar-vector tests of QCD. (Copyright

Effective Lagrangians for SUSY QCD with properties seen in perturbation theory

International Nuclear Information System (INIS)

Sharatchandra, H.S.

1984-06-01

We construct effective Lagrangians for supersymmetric QCD which properly incorporate the relevant Ward identities and possess features encountered in perturbation theory. This shows that the unusual scenarios, proposed for SUSY QCD, are not necessary. (author)

QCD and the chiral critical point

International Nuclear Information System (INIS)

Gavin, S.; Gocksch, A.; Pisarski, R.D.

1994-01-01

As an extension of QCD, consider a theory with ''2+1'' flavors, where the current quark masses are held in a fixed ratio as the overall scale of the quark masses is varied. At nonzero temperature and baryon density it is expected that in the chiral limit the chiral phase transition is of first order. Increasing the quark mass from zero, the chiral transition becomes more weakly first order, and can end in a chiral critical point. We show that the only massless field at the chiral critical point is a σ meson, with the universality class that of the Ising model. Present day lattice simulations indicate that QCD is (relatively) near to the chiral critical point

Hadronization of QCD and effective interactions

International Nuclear Information System (INIS)

Frank, M.R.

1994-01-01

An introductory treatment of hadronization through functional integral calculus and bifocal Bose fields is given. Emphasis is placed on the utility of this approach for providing a connection between QCD and effective hadronic field theories. The hadronic interactions obtained by this method are nonlocal due to the QCD substructure, yet, in the presence of an electromagnetic field, maintain the electromagnetic gauge invariance manifest at the quark level. A local chiral model which is structurally consistent with chiral perturbation theory is obtained through a derivative expansion of the nonlocalities with determined, finite coefficients. Tree-level calculations of the pion form factor and π - π scattering, which illustrate the dual constituent-quark-chiral-model nature of this approach, are presented

Electroweak Higgs production with HiggsPO at NLO QCD

Science.gov (United States)

Greljo, Admir; Isidori, Gino; Lindert, Jonas M.; Marzocca, David; Zhang, Hantian

2017-12-01

We present the HiggsPO UFO model for Monte Carlo event generation of electroweak VH and VBF Higgs production processes at NLO in QCD in the formalism of Higgs pseudo-observables (PO). We illustrate the use of this tool by studying the QCD corrections, matched to a parton shower, for several benchmark points in the Higgs PO parameter space. We find that, while being sizable and thus important to be considered in realistic experimental analyses, the QCD higher-order corrections largely factorize. As an additional finding, based on the NLO results, we advocate to consider 2D distributions of the two-jet azimuthal-angle difference and the leading jet p_T for new physics searches in VBF Higgs production. The HiggsPO UFO model is publicly available.

On-shell recurrence relations for one-loop QCD amplitudes

International Nuclear Information System (INIS)

Bern, Zvi; Dixon, Lance J.; Kosower, David A.

2005-01-01

We present examples of on-shell recurrence relations for determining rational functions appearing in one-loop QCD amplitudes. In particular, we give relations for one-loop QCD amplitudes with all legs of positive helicity, or with one leg of negative helicity and the rest of positive helicity. Our recurrence relations are similar to the tree-level ones described by Britto, Cachazo, Feng, and Witten. A number of new features arise for loop amplitudes in nonsupersymmetric theories like QCD, including boundary terms and double poles. We show how to eliminate the boundary terms, which would interfere with obtaining useful relations. Using the relations we give compact explicit expressions for the n-gluon amplitudes with one negative-helicity gluon, up through n=7

Non-perturbative Debye mass in finite-T QCD

CERN Document Server

Kajantie, Keijo; Peisa, J; Rajantie, A; Rummukainen, K; Shaposhnikov, Mikhail E

1997-01-01

Employing a non-perturbative gauge invariant definition of the Debye screening mass m_D in the effective field theory approach to finite T QCD, we use 3d lattice simulations to determine the leading O(g^2) and to estimate the next-to-leading O(g^3) corrections to m_D in the high temperature region. The O(g^2) correction is large and modifies qualitatively the standard power-counting hierarchy picture of correlation lengths in high temperature QCD.

Factorization method for simulating QCD at finite density

International Nuclear Information System (INIS)

Nishimura, Jun

2003-01-01

We propose a new method for simulating QCD at finite density. The method is based on a general factorization property of distribution functions of observables, and it is therefore applicable to any system with a complex action. The so-called overlap problem is completely eliminated by the use of constrained simulations. We test this method in a Random Matrix Theory for finite density QCD, where we are able to reproduce the exact results for the quark number density. (author)

QCD and RHIC

International Nuclear Information System (INIS)

Kharzeev, D.

2004-01-01

In this talk I discuss recent advances in Quantum Chromo-Dynamics, in particular the progress in understanding the collective dynamics of the theory. I emphasise the significance of the RHIC program for establishing the properties of hot and dense QCD matter and for understanding the dynamics of the theory at the high parton density, strong color field frontier. Hopes and expectations for the future are discussed as well

QCD on the light cone

International Nuclear Information System (INIS)

Brodsky, S.J.

1992-09-01

The quantization of gauge theory at fixed light-cone time τ = t - z/c provides new perspectives for solving non-perturbative problems in quantum chromodynamics. The light-cone Fock state expansion provides both a precise definition of the relativistic wavefunctions of hadrons as bound-states of quarks and gluons and a general calculus for predicting QCD processes at the amplitude level. Applications to exclusive processes and weak decay amplitudes are discussed. The problem of computing the hadronic spectrum and the corresponding light-cone wavefunctions of QCD in one space and one time dimension has been successfully reduced to the diagonalization of a discrete representation of the light-cone Hamiltonian. The problems confronting the solution of gauge theories in 3 + 1 dimensions in the light-cone quantization formalism,, including zero modes and non-perturbative renormalization, are reviewed

Baryon physics in holographic QCD

Directory of Open Access Journals (Sweden)

Alex Pomarol

2009-03-01

Full Text Available In a simple holographic model for QCD in which the Chern–Simons term is incorporated to take into account the QCD chiral anomaly, we show that baryons arise as stable solitons which are the 5D analogs of 4D skyrmions. Contrary to 4D skyrmions and previously considered holographic scenarios, these solitons have sizes larger than the inverse cut-off of the model, and therefore they are predictable within our effective field theory approach. We perform a numerical determination of several static properties of the nucleons and find a satisfactory agreement with data. We also calculate the amplitudes of “anomalous” processes induced by the Chern–Simons term in the meson sector, such as ω→πγ and ω→3π. A combined fit to baryonic and mesonic observables leads to an agreement with experiments within 16%.

Λ2 of effective q.c.d. in the minimal subtraction scheme

International Nuclear Information System (INIS)

Miller, R.D.C.; McKellar, B.H.J.

1981-01-01

Practical Q.C.D. is an effective field theory in that unexcited heavy quarks are decoupled from the theory. To predict effects dependent on the heavy quarks one needs the R.G. invariants of the effective Q.C.D. in which they are retained. The R.G. invariants Λsub(n) 2 of the effective n flavour Q.C.D. are calculated from the observed Λ 4 2

Single slepton production associated with a top quark at LHC in NLO QCD

International Nuclear Information System (INIS)

Li, Xiao-Peng; Guo, Lei; Ma, Wen-Gan; Han, Liang; Zhang, Ren-You; Wang, Shao-Ming

2012-01-01

Single slepton production in association with a top quark at the CERN Large Hadron Collider (LHC) is one of the important processes in probing the R-parity violation couplings. We calculate the QCD next-to-leading order (NLO) corrections to the pp→tl - (anti tl + ) + X process at the LHC and discuss the impacts of the QCD corrections on kinematic distributions. We investigate the dependence of the leading order (LO) and the NLO QCD corrected integrated cross section on the factorization/renormalization energy scale, slepton, stop-quark and gluino masses. We find that the uncertainty of the LO cross section due to the energy scale is obviously improved by the NLO QCD corrections, and the exclusive jet event selection scheme keeps the convergence of the perturbative series better than the inclusive scheme. The results show that the polarization asymmetry of the top-quark will be reduced by the NLO QCD corrections, and the QCD corrections generally increase with the increment of the t 1 or g mass value. (orig.)

Microbial degradation of monocyclic and polycyclic aromatic hydrocarbons in case of limited pollutant availability with nitrate as a potential electron acceptor; Der mikrobielle Abbau mono- und polyzyklischer aromatischer Kohlenwasserstoffe bei einer begrenzten Schadstoffverfuegbarkeit mit Nitrat als potentiellem Elektronenakzeptor

Energy Technology Data Exchange (ETDEWEB)

Linke, C.

2001-07-01

. Zusammenfassend muss aus dieser Arbeit daher der Schluss gezogen werden, dass im Untergrund nicht die PAK-Verfuegbarkeit den limitierenden Faktor fuer mikrobielle Umsetzungen darstellt. Vielmehr wird der Schadstoffabbau durch fehlenden Sauerstoff begrenzt. Der Einsatz oberflaechenaktiver Substanzen zur Erhoehung der Schadstoffloeslichkeit traegt damit nicht zu einer Verbesserung des Schadstoffabbaus bei. Ein Tensideintrag waere sogar nachteilig, da damit weitere potentiell Sauerstoff zehrende Substanzen in den Untergrund eingebracht wuerden. (orig.)

The heavy quark-antiquark potential from lattice and perturbative QCD

OpenAIRE

Laschka, Alexander; Kaiser, Norbert; Weise, Wolfram

2009-01-01

The heavy quark-antiquark potential in perturbative QCD is subject to ambiguities. We show how to derive a well-defined and stable short-distance potential that can be matched to results from lattice QCD simulations at intermediate distances. The static potential as well as the order 1/m potential are discussed.

The CP-odd sector and $θ$ dynamics in holographic QCD

NARCIS (Netherlands)

Arean, Daniel; Iatrakis, Ioannis; Jarvinen, Matti; Kiritsis, Elias

2017-01-01

The holographic model of V-QCD is used to analyze the physics of QCD in the Veneziano large-N limit. An unprecedented analysis of the CP-odd physics is performed going beyond the level of effective field theories. The structure of holographic saddle-points at finite $\\theta$ is determined, as well

A color magnetic vortex condensate in QCD

International Nuclear Information System (INIS)

Ambjoern, J.; Olesen, P.

1980-03-01

It is shown that there exists a very close analogy between a lattice of vorticies in a superconductor near the critical field and a condensate of color magnetic flux tubes due to the unstable mode in QCD. This analogy makes it possible to identify a dynamical Higgs field in QCD. It is shown that the color magnetic flux tubes are quantized in terms of the center group Z(2) in the SU(2) case. In the case of SU(N) it is possible to select a color direction of the field such that one has Z(N) quantization. (Auth.)

Two-dimensional QCD in the Coulomb gauge

International Nuclear Information System (INIS)

Kalashnikova, Yu.S.; Nefed'ev, A.V.

2002-01-01

Various aspects of the 't Hooft model for two-dimensional QCD in the limit of infinite number of colours in the Coulomb gauge are discussed. The properties of mesonic excitations are studied, with special emphasis on the pion. Attention is paid to the dual role of the pion. which, while a genuine qq-bar state, is a Goldstone boson of two-dimensional QCD as well. In particular, the validity of the soft-pion theorems is demonstrated. It is shown that the Coulomb gauge is the most suitable choice for the study of hadronic observables involving pions [ru

Playing with QCD I: effective field theories

International Nuclear Information System (INIS)

Fraga, Eduardo S.

2009-01-01

The building blocks of hadrons are quarks and gluons, although color is confined into singlet states. QCD is believed to be the fundamental theory of strong interactions. Its asymptotically free nature puts the vacuum out of reach for perturbation theory. The Lagrangian of QCD and the Feynman rules associated were built by using the Gauge Principle, starting from the quark matter fields and obtaining gluons as connections. A simpler, and sometimes necessary or complementary, approach is provided by effective field theories or effective models, especially when one has to deal with the nonperturbative sector of the theory. (author)

Power corrections to exclusive processes in QCD

Energy Technology Data Exchange (ETDEWEB)

Mankiewicz, Lech

2002-02-01

In practice applicability of twist expansion crucially depends on the magnitude to power corrections to the leading-twist amplitude. I illustrate this point by considering explicit examples of two hard exclusive processes in QCD. In the case of {gamma}{sup *}{gamma} {yields} {pi}{pi} amplitude power corrections are small enough such that it should be possible to describe current experimental data by the leading-twist QCD prediction. The photon helicity-flip amplitude in DVCS on a nucleon receives large kinematical power corrections which screen the leading-twist prediction up to large values of the hard photon virtuality.

Explaining jet quenching with perturbative QCD alone

CERN Document Server

Zapp, Korinna C; Wiedemann, Urs A

2011-01-01

We present a new formulation of jet quenching in perturbative QCD beyond the eikonal approximation. Multiple scattering in the medium is modelled through infra-red-continued (2 -> 2) scattering matrix elements in QCD and the parton shower describing further emissions. The interplay between these processes is arranged in terms of a formation time constraint such that coherent emissions can be treated consistently. Emerging partons are hadronised by the Lund string model, tuned to describe LEP data in conjunction with the parton shower. Based on this picture we obtain a good description of the nuclear modification factor R_AA at RHIC and LHC.

Factorial correlators: angular scaling within QCD jets

International Nuclear Information System (INIS)

Peschanski, R.

2001-01-01

Factorial correlators measure the amount of dynamical correlation in the multiplicity between two separated phase-space windows. We present the analytical derivation of factorial correlators for a QCD jet described at the double logarithmic (DL) accuracy. We obtain a new angular scaling property for properly normalized correlators between two solid-angle cells or two rings around the jet axis. Normalized QCD factorial correlators scale with the angular distance and are independent of the window size. Scaling violations are expected beyond the DL approximation, in particular from the subject structure. Experimental tests are feasible, and thus would be welcome. (orig.)

Search for the QCD critical point at SPS energies

CERN Document Server

Anticic, T.; Barna, D.; Bartke, J.; Betev, L.; Bialkowska, H.; Blume, C.; Boimska, B.; Botje, M.; Bracinik, J.; Buncic, P.; Cerny, V.; Christakoglou, P.; Chung, P.; Chvala, O.; Cramer, J.G.; Csato, P.; Dinkelaker, P.; Eckardt, V.; Fodor, Z.; Foka, P.; Friese, V.; Gal, J.; Gazdzicki, M.; Genchev, V.; Gladysz, E.; Grebieszkow, K.; Hegyi, S.; Hohne, C.; Kadija, K.; Karev, A.; Kikola, D.; Kolesnikov, V.I.; Kornas, E.; Korus, R.; Kowalski, M.; Kreps, M.; Laszlo, A.; Lacey, R.; van Leeuwen, M.; Levai, P.; Litov, L.; Lungwitz, B.; Makariev, M.; Malakhov, A.I.; Mateev, M.; Melkumov, G.L.; Mischke, A.; Mitrovski, M.; Mrowczynski, St.; Palla, G.; Panagiotou, A.D.; Petridis, A.; Peryt, W.; Pikna, M.; Pluta, J.; Prindle, D.; Puhlhofer, F.; Renfordt, R.; Roland, C.; Roland, G.; Rybczynski, M.; Rybicki, A.; Sandoval, A.; Schmitz, N.; Schuster, T.; Seyboth, P.; Sikler, F.; Sitar, B.; Skrzypczak, E.; Slodkowski, M.; Stefanek, G.; Stock, R.; Strabel, C.; Strobele, H.; Susa, T.; Szentpetery, I.; Sziklai, J.; Szuba, M.; Szymanski, P.; Trubnikov, V.; Utvic, M.; Varga, D.; Vassiliou, M.; Veres, G.I.; Vesztergombi, G.; Vranic, D.; Wlodarczyk, Z.; Wojtaszek-Szwarc, A.; Yoo, I.K.; Abgrall, N.; Aduszkiewicz, A.; Andrieu, B.; Anticic, T.; Antoniou, N.; Argyriades, J.; Asryan, A.G.; Blondel, A.; Blumer, J.; Boldizsar, L.; Bravar, A.; Brzychczyk, J.; Bubak, A.; Bunyatov, S.A.; Choi, K.-U.; Chung, P.; Cleymans, J.; Derkach, D.A.; Diakonos, F.; Dominik, W.; Dumarchez, J.; Engel, R.; Ereditato, A.; Feofilov, G.A.; Ferrero, A.; Gazdzicki, M.; Golubeva, M.; Grzeszczuk, A.; Guber, F.; Hasegawa, T.; Haungs, A.; Igolkin, S.; Ivanov, A.S.; Ivashkin, A.; Katrynska, N.; Kielczewska, D.; Kisiel, J.; Kobayashi, T.; Kolev, D.; Kolevatov, R.S.; Kondratiev, V.P.; Kowalski, S.; Kurepin, A.; Lacey, R.; Lyubushkin, V.V.; Majka, Z.; Marchionni, A.; Marcinek, A.; Maris, I.; Matveev, V.; Meregaglia, A.; Messina, M.; Mijakowski, P.; Montaruli, T.; Murphy, S.; Nakadaira, T.; Naumenko, P.A.; Nikolic, V.; Nishikawa, K.; Palczewski, T.; Planeta, R.; Popov, B.A.; Posiadala, M.; Przewlocki, P.; Rauch, W.; Ravonel, M.; Rohrich, D.; Rondio, E.; Rossi, B.; Roth, M.; Rubbia, A.; Sadovsky, A.; Sakashita, K.; Sekiguchi, T.; Seyboth, P.; Shibata, M.; Sissakian, A.N.; Sorin, A.S.; Staszel, P.; Stepaniak, J.; Strabel, C.; Stroebele, H.; Tada, M.; Taranenko, A.; Tsenov, R.; Ulrich, R.; Unger, M.; Vechernin, V.V.; Zipper, W.

2009-01-01

Lattice QCD calculations locate the QCD critical point at energies accessible at the CERN Super Proton Synchrotron (SPS). We present average transverse momentum and multiplicity fluctuations, as well as baryon and anti-baryon transverse mass spectra which are expected to be sensitive to effects of the critical point. The future CP search strategy of the NA61/SHINE experiment at the SPS is also discussed.

Lepton pair production at ISR energies and QCD

International Nuclear Information System (INIS)

Altarelli, G.; Martinelli, G.

1985-01-01

Motivated by some recent results from the ISR we have considered all available data on the production of Drell-Yan pairs by high energy proton beams. We show that the lepton pair cross sections and qsub(T) distributions are correctly described by QCD using the known distributions of partons in the proton and acceptable values of the QCD scale Λ. No other free parameter is required. Within the accuracy of the data no appreciable intrinsic transverse momentum is needed. (orig.)

Are topological charge fluctuations in QCD instanton dominated?

International Nuclear Information System (INIS)

Edwards, Robert G.; Heller, Urs M.

2002-01-01

We consider a recent proposal by Horvath et al. to address the question of whether topological charge fluctuations in QCD are instanton dominated via the response of fermions using lattice fermions with exact chiral symmetry, the overlap fermions. Considering several volumes and lattice spacings, we find strong evidence for chirality of a finite density of low-lying eigenvectors of the overlap-Dirac operator in the regions where these modes are peaked. This result suggests instanton dominance of topological charge fluctuations in quenched QCD

Are Topological Charge Fluctuations in QCD Instanton Dominated?

International Nuclear Information System (INIS)

Edwards, Robert G.; Heller, Urs M.

2001-01-01

We consider a recent proposal by Horvath et al. to address the question whether topological charge fluctuations in QCD are instanton dominated via the response of fermions using lattice fermions with exact chiral symmetry, the overlap fermions. Considering several volumes and lattice spacings we find strong evidence for chirality of a finite density of low-lying eigenvectors of the overlap-Dirac operator in the regions where these modes are peaked. This result suggests instanton dominance of topological charge fluctuations in quenched QCD

Exploring the QCD phase diagram through relativistic heavy ion collisions

Directory of Open Access Journals (Sweden)

Mohanty Bedangadas

2014-03-01

Full Text Available We present a review of the studies related to establishing the QCD phase diagram through high energy nucleus-nucleus collisions. We particularly focus on the experimental results related to the formation of a quark-gluon phase, crossover transition and search for a critical point in the QCD phase diagram.

Exposing the QCD Splitting Function with CMS Open Data.

Science.gov (United States)

Larkoski, Andrew; Marzani, Simone; Thaler, Jesse; Tripathee, Aashish; Xue, Wei

2017-09-29

The splitting function is a universal property of quantum chromodynamics (QCD) which describes how energy is shared between partons. Despite its ubiquitous appearance in many QCD calculations, the splitting function cannot be measured directly, since it always appears multiplied by a collinear singularity factor. Recently, however, a new jet substructure observable was introduced which asymptotes to the splitting function for sufficiently high jet energies. This provides a way to expose the splitting function through jet substructure measurements at the Large Hadron Collider. In this Letter, we use public data released by the CMS experiment to study the two-prong substructure of jets and test the 1→2 splitting function of QCD. To our knowledge, this is the first ever physics analysis based on the CMS Open Data.

The High Energy Asymptotics of Scattering Processes in QCD

Energy Technology Data Exchange (ETDEWEB)

Enberg, Rikard; Golec-Biernat, K.; Munier, S.

2005-05-12

High energy scattering in the QCD parton model was recently shown to be a reaction-diffusion process, and thus to lie in the universality class of the stochastic Fisher-Kolmogorov-Petrovsky-Piscounov equation. We recall that the latter appears naturally in the context of the parton model. We provide a thorough numerical analysis of the mean field approximation, given in QCD by the Balitsky-Kovchegov equation. In the framework of a simple stochastic toy model that captures the relevant features of QCD, we discuss and illustrate the universal properties of such stochastic models. We investigate in particular the validity of the mean field approximation and how it is broken by fluctuations. We find that the mean field approximation is a good approximation in the initial stages of the evolution in rapidity.

Electroweak Higgs production with HiggsPO at NLO QCD

International Nuclear Information System (INIS)

Greljo, Admir; Isidori, Gino; Zhang, Hantian; Lindert, Jonas M.; Marzocca, David

2017-01-01

We present the HiggsPO UFO model for Monte Carlo event generation of electroweak VH and VBF Higgs production processes at NLO in QCD in the formalism of Higgs pseudo-observables (PO). We illustrate the use of this tool by studying the QCD corrections, matched to a parton shower, for several benchmark points in the Higgs PO parameter space. We find that, while being sizable and thus important to be considered in realistic experimental analyses, the QCD higher-order corrections largely factorize. As an additional finding, based on the NLO results, we advocate to consider 2D distributions of the two-jet azimuthal-angle difference and the leading jet p T for new physics searches in VBF Higgs production. The HiggsPO UFO model is publicly available. (orig.)

Electroweak Higgs production with HiggsPO at NLO QCD

Energy Technology Data Exchange (ETDEWEB)

Greljo, Admir [Universitaet Zuerich, Physik-Institut, Zurich (Switzerland); Johannes Gutenberg-Universitaet Mainz, PRISMA Cluster of Excellence and Mainz Institute for Theoretical Physics, Mainz (Germany); University of Sarajevo, Faculty of Science, Sarajevo (Bosnia and Herzegovina); Isidori, Gino; Zhang, Hantian [Universitaet Zuerich, Physik-Institut, Zurich (Switzerland); Lindert, Jonas M. [Durham University, Department of Physics, Institute for Particle Physics Phenomenology, Durham (United Kingdom); Marzocca, David [Universitaet Zuerich, Physik-Institut, Zurich (Switzerland); INFN, Sezione di Trieste(Italy); SISSA, Trieste (Italy)

2017-12-15

We present the HiggsPO UFO model for Monte Carlo event generation of electroweak VH and VBF Higgs production processes at NLO in QCD in the formalism of Higgs pseudo-observables (PO). We illustrate the use of this tool by studying the QCD corrections, matched to a parton shower, for several benchmark points in the Higgs PO parameter space. We find that, while being sizable and thus important to be considered in realistic experimental analyses, the QCD higher-order corrections largely factorize. As an additional finding, based on the NLO results, we advocate to consider 2D distributions of the two-jet azimuthal-angle difference and the leading jet p{sub T} for new physics searches in VBF Higgs production. The HiggsPO UFO model is publicly available. (orig.)

Primordial black hole formation during the QCD epoch

International Nuclear Information System (INIS)

Jedamzik, K.

1997-01-01

We consider the formation of horizon-size primordial black holes (PBH close-quote s) from pre-existing density fluctuations during cosmic phase transitions. It is pointed out that the formation of PBH close-quote s should be particularly efficient during the QCD epoch due to a substantial reduction of pressure forces during adiabatic collapse, or equivalently, a significant decrease in the effective speed of sound during the color-confinement transition. Our considerations imply that for generic initial density perturbation spectra PBH mass functions are expected to exhibit a pronounced peak on the QCD-horizon mass scale ∼1M circle-dot . This mass scale is roughly coincident with the estimated masses for compact objects recently observed in our galactic halo by the MACHO Collaboration. Black holes formed during the QCD epoch may offer an attractive explanation for the origin of halo dark matter evading possibly problematic nucleosynthesis and luminosity bounds on baryonic halo dark matter. copyright 1997 The American Physical Society

Holographic QCD with topologically charged domain-wall/membranes

International Nuclear Information System (INIS)

Lin Fengli; Wu Shangyu

2008-01-01

We study the thermodynamical phase structures of holographic QCD with nontrivial topologically charged domain-wall/membranes which are originally related to the multiple θ-vacua in the large N c limit. We realize the topologically charged membranes as the holographic D6-brane fluxes in the Sakai-Sugimoto model. The D6-brane fluxes couple to the probe D8-D8-bar via Chern-Simon term, and act as the source for the baryonic current density of QCD. We find rich phase structures of the dual meson system by varying asymptotic separation of D8 and D8-bar. Especially, there can be a thermodynamically favored and stable phase of finite baryonic current density. This provides the supporting evidence for the discovery of the topologically charged membranes found in the lattice QCD calculations. We also find a crossover phase with the limiting baryonic current density and temperature which suggest a Hagedorn-like phase transition of meson dissociation.

LHC physics: challenges for QCD

OpenAIRE

Frixione, S.

2003-01-01

I review the status of the comparisons between a few measurements at hadronic colliders and perturbative QCD predictions, which emphasize the need for improving the current computations. Such improvements will be mandatory for a satisfactory understanding of high-energy collisions at the LHC

Phenomenology Using Lattice QCD

Science.gov (United States)

Gupta, R.

2005-08-01

This talk provides a brief summary of the status of lattice QCD calculations of the light quark masses and the kaon bag parameter BK. Precise estimates of these four fundamental parameters of the standard model, i.e., mu, md, ms and the CP violating parameter η, help constrain grand unified models and could provide a window to new physics.

QCD and collider physics

CERN Document Server

Stirling, William James

1991-12-01

1. Some basic theory. 2. Two important applications: - e+ e- annihilation (LEPSLS) ; deep inelastic scattering (HERA). 3. Other applications..., large Pt jets, W and Z, heavy quark production..., (pp- colliders). In this lecture: some basic theory. 1. QCD as a non abelian gauge field theory. 2. Asymptotic freedom. 3. Beyond leading order - renormalisation schemes. 4. MS.

Delving into QCD jets

International Nuclear Information System (INIS)

Konishi, K.

1980-01-01

The author discusses, in an introductory fashion, the latest developments in the study of hadronic jets produced in hard processes, based on perturbative QCD. Emphasis is on jet calculus (and its applications and generalizations), and on the appearance of a parton-like consistent, over-all picture of jet evolution in momentum, colour, and real space-time. (Auth.)

QCD on the connection machine

International Nuclear Information System (INIS)

Gupta, R.

1990-01-01

In this talk I give a brief introduction to the standard model of particle interactions and illustrate why analytical methods fail to solve QCD. I then give some details of our implementation of the high performance QCD code on the CM2 and highlight the important lessons learned. The sustained speed of the code at the time of this conference is 5.2 Gigaflops (scaled to a full 64K machine). Since this is a conference dedicated to computing in the 21st century, I will tailor my expectations (somewhat idiosyncratic) of the physics objectives to reflect what we will be able to do in 10 years time, extrapolating from where we stand today. This work is being done under a joint LANL-TMC collaboration consisting of C. Baillie, R. Brickner, D. Daniel, G. Kilcup, L. Johnson, A. Patel. S. Sharpe and myself. 5 refs

Tombes et cimetières éthiopiens : des rois, des saints, des anonymes1

OpenAIRE

Derat, Marie-Laure

2009-01-01

L’histoire des tombes et cimetières éthiopiens, dans la longue durée, en est encore à ses balbutiements. Si les tombes des saints et des rois nous sont un peu mieux connus grâce à des textes témoignant à la fois des enjeux entourant les sépultures de ces personnages hors du commun et des soins apportés à leur inhumation, en revanche, les cimetières ordinaires échappent encore largement à l’enquête, en grande partie parce que le commun des mortels est inhumé dans l’anonymat et dans un grand dé...

Hadronic corrections to electroweak observables from twisted mass lattice QCD

International Nuclear Information System (INIS)

Pientka, Grit

2015-01-01

For several benchmark quantities investigated to detect signs for new physics beyond the standard model of elementary particle physics, lattice QCD currently constitutes the only ab initio approach available at small momentum transfers for the computation of non-perturbative hadronic contributions. Among those observables are the lepton anomalous magnetic moments and the running of the electroweak coupling constants. We compute the leading QCD contribution to the muon anomalous magnetic moment by performing lattice QCD calculations on ensembles incorporating N f =2+1+1 dynamical twisted mass fermions. Considering active up, down, strange, and charm quarks, admits for the first time a direct comparison of the lattice data for the muon anomaly with phenomenological results because both the latter as well as the experimentally obtained values are sensitive to the complete first two generations of quarks at the current level of precision. Recently, it has been noted that improved measurements of the electron and tau anomalous magnetic moments might also provide ways of detecting new physics contributions. Therefore, we also compute their leading QCD contributions, which simultaneously serve as cross-checks of the value obtained for the muon. Additionally, we utilise the obtained data to compute the leading hadronic contribution to the running of the fine structure constant, which enters all perturbative QED calculations. Furthermore, we show that even for the weak mixing angle the leading QCD contribution can be computed from this data. In this way, we identify a new prime observable in the search for new physics whose hadronic contributions can be obtained from lattice QCD. With the results obtained in this thesis, we are able to exclude unsuitable phenomenologically necessary flavour separations and thus directly assist the presently more precise phenomenological determinations of this eminent quantity.

Global QCD Analysis of the Nucleon Tensor Charge with Lattice QCD Constraints

Science.gov (United States)

Shows, Harvey, III; Melnitchouk, Wally; Sato, Nobuo

2017-09-01

By studying the parton distribution functions (PDFs) of a nucleon, we probe the partonic scale of nature, exploring what it means to be a nucleon. In this study, we are interested in the transversity PDF-the least studied of the three collinear PDFs. By conducting a global analysis on experimental data from semi-inclusive deep inelastic scattering (SIDIS), as well as single-inclusive e+e- annihilation (SIA), we extract the fit parameters needed to describe the transverse moment dependent (TMD) transversity PDF, as well as the Collins fragmentation function. Once the collinear transversity PDF is obtained by integrating the extracted TMD PDF, we wish to resolve discrepancies between lattice QCD calculations and phenomenological extractions of the tensor charge from data. Here we show our results for the transversity distribution and tensor charge. Using our method of iterative Monte Carlo, we now have a more robust understanding of the transversity PDF. With these results we are able to progress in our understanding of TMD PDFs, as well as testify to the efficacy of current lattice QCD calculations. This work is made possible through support from NSF award 1659177 to Old Dominion University.

NLO QCD Corrections to Drell-Yan in TeV-scale Gravity Models

International Nuclear Information System (INIS)

Mathews, Prakash; Ravindran, V.

2006-01-01

In TeV scale gravity models, we present the NLO-QCD corrections for the double differential cross sections in the scattering angle for dilepton production at hadron colliders. The quantitative impact of QCD corrections for extra dimension searches at LHC and Tevatron are investigated for both ADD and RS models through K-factors. We also show how the inclusion of QCD corrections to NLO stabilises the cross section with respect to renormalisation and factorisation scale variations

Instantons in the QCD vacuum and in deep inelastic scattering

International Nuclear Information System (INIS)

Ringwald, A.; Schrempp, F.

1999-01-01

We give a brief status report on our on-going investigation of the prospects to discover QCD instantons in deep inelastic scattering (DIS) at HERA. A recent high-quality lattice study of the topological structure of the QCD vacuum is exploited to provide crucial support of our predictions for DIS, based on instanton perturbation theory

Évaluation des pratiques agricoles des légumes feuilles : le cas des ...

African Journals Online (AJOL)

Face à ce constat, le défi de la recherche serait la détermination du niveau actuel de contamination des légumes feuilles et des eaux du barrage et celui de l'État serait l'initiation de programmes de sensibilisation des producteurs par rapport à une gestion plus rigoureuse des pesticides. Mots-clés : pratiques paysannes, ...

QCD collinear factorization, its extensions and the partonic distributions

OpenAIRE

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...

La convergence des rôles respectifs des relationnistes et des journalistes influence-t-elle la perception qu'ils ont les uns des autres?

DEFF Research Database (Denmark)

Valentini, Chiara

2017-01-01

la convergence des rôles respectifs des praticiens des relations publiques et des journalistes a un effet favorable sur la perception qu’ils ont les uns des autres. L’effet est plus marqué chez les praticiens des relations publiques, car leur vision de la profession en journalisme correspond à celle...

Mécanique des sols et des roches

CERN Document Server

Vullier, Laurent; Zhao, Jian

2016-01-01

La mécanique des sols et la mécanique des roches sont des disciplines généralement traitées séparément dans la littérature. Pour la première fois, un traité réunit ces deux spécialités, en intégrant également les connaissances en lien avec les écoulements souterrains et les transferts thermiques. A la fois théorique et pratique, cet ouvrage propose tout d'abord une description détaillée de la nature et de la composition des sols et des roches, puis s'attache à la modélisation de problèmes aux conditions limites et présente les essais permettant de caractériser les sols et les roches, tant d'un point de vue mécanique qu'hydraulique et thermique. La problématique des sols non saturés et des écoulements multiphasiques est également abordée. Une attention particulière est portée aux lois de comportement mécanique et à la détermination de leurs paramètres par des essais in situ et en laboratoire, et l'ouvrage offre également une présentation détaillée des systèmes de classi...

Deconfinement phase transition in QCD with heavy quarks

International Nuclear Information System (INIS)

Attig, N.; Petersson, B.; Wolff, M.; Gavai, R.V.

1988-01-01

Using the pseudo-fermion method to simulate QCD with dynamical quarks we investigate the effects of heavy dynamical quarks of 2 flavours on the deconfinement phase transition in the quenched QCD. As the mass of the quark is decreased the phase transition weakens as expected. Compared to the earlier results with leading order hopping parameter expansion, however, the weakening is less rapid. Our estimated upper bound on the critical mass where the transition becomes continuous is 1.5-2 times lower than earlier results. (orig.)

Winter Workshop on Recent QCD Advances at the LHC, Slides of the presentations

International Nuclear Information System (INIS)

D'Enterria, D.; Skands, P.; Siodmok, A.K.; Hoeth, H.; Jung, H.; Caforio, D.; Poghosyan, M.; Aquines, O.; Mitsuka, G.; Toia, A.; Jalilian-Marian, J.; Watt, G.; Guzzi, M.; Sarkar, A.; Paukkunen, H.; Kucharczyk, M.; Gouzevitch, M.; Bartels, J.; Lopez Albacete, J.; Teixeira de Almeida Milhano, G.; Marquet, C.; Kosower, D.; Guillet, J.P.; Arleo, F.; Hance, M.; Kolberg, T.R.; Weber, M.A.; Delsart, P.A.; Hinzmann, A.; Vincter, M.; Soyez, G.; Busch, O.; Nguyen, M.; Rybar, M.; Schienbein, I.; Lansberg, J.P.; Britsch, M.; Dorigo, T.; De Capua, S.; Greco, V.; Prino, F.; Panikashvili, N.; Park, W.J.; Ulrich, R.M.; Pecjak, B.; Silvestre, C.; Van Eldik, N.

2012-01-01

With the recent startup of operation at the Large Hadron Collider (LHC), the physics of the strong interaction described by the theory of Quantum Chromodynamics (QCD) explores a new territory in proton-proton and Pb-Pb collisions at energies never reached before: √(s)=7 TeV for p-p collisions and √=2.76 TeV for Pb-Pb collisions. The topics of the workshop are organized around 3 main axes: perturbative QCD (including jets, high-P T , direct photons, heavy quarks, quarkonia,...), QCD in the non-perturbative regime (including inclusive hadron production, diffraction,...) and low-x QCD. This document gathers the slides of all the presentations

A classical primer for QCD

International Nuclear Information System (INIS)

Moriyasu, K.

1981-01-01

A basic primer for QCD is presented using a semiclassical approach to the colour Maxwell equations. The non-Abelian nature of colour symmetry and the violation of superposition by colour fields is compared with QED. A simple discussion of asymptotic freedom is also presented. (author)

A bayesian approach to QCD sum rules

International Nuclear Information System (INIS)

Gubler, Philipp; Oka, Makoto

2010-01-01

QCD sum rules are analyzed with the help of the Maximum Entropy Method. We develop a new technique based on the Bayesion inference theory, which allows us to directly obtain the spectral function of a given correlator from the results of the operator product expansion given in the deep euclidean 4-momentum region. The most important advantage of this approach is that one does not have to make any a priori assumptions about the functional form of the spectral function, such as the 'pole + continuum' ansatz that has been widely used in QCD sum rule studies, but only needs to specify the asymptotic values of the spectral function at high and low energies as an input. As a first test of the applicability of this method, we have analyzed the sum rules of the ρ-meson, a case where the sum rules are known to work well. Our results show a clear peak structure in the region of the experimental mass of the ρ-meson. We thus demonstrate that the Maximum Entropy Method is successfully applied and that it is an efficient tool in the analysis of QCD sum rules. (author)

QCD in heavy quark production and decay

Energy Technology Data Exchange (ETDEWEB)

Wiss, J. [Univ. of Illinois, Urbana, IL (United States)

1997-06-01

The author discusses how QCD is used to understand the physics of heavy quark production and decay dynamics. His discussion of production dynamics primarily concentrates on charm photoproduction data which are compared to perturbative QCD calculations which incorporate fragmentation effects. He begins his discussion of heavy quark decay by reviewing data on charm and beauty lifetimes. Present data on fully leptonic and semileptonic charm decay are then reviewed. Measurements of the hadronic weak current form factors are compared to the nonperturbative QCD-based predictions of Lattice Gauge Theories. He next discusses polarization phenomena present in charmed baryon decay. Heavy Quark Effective Theory predicts that the daughter baryon will recoil from the charmed parent with nearly 100% left-handed polarization, which is in excellent agreement with present data. He concludes by discussing nonleptonic charm decay which is traditionally analyzed in a factorization framework applicable to two-body and quasi-two-body nonleptonic decays. This discussion emphasizes the important role of final state interactions in influencing both the observed decay width of various two-body final states as well as modifying the interference between interfering resonance channels which contribute to specific multibody decays. 50 refs., 77 figs.

QCD in heavy quark production and decay

International Nuclear Information System (INIS)

Wiss, J.

1997-01-01

The author discusses how QCD is used to understand the physics of heavy quark production and decay dynamics. His discussion of production dynamics primarily concentrates on charm photoproduction data which are compared to perturbative QCD calculations which incorporate fragmentation effects. He begins his discussion of heavy quark decay by reviewing data on charm and beauty lifetimes. Present data on fully leptonic and semileptonic charm decay are then reviewed. Measurements of the hadronic weak current form factors are compared to the nonperturbative QCD-based predictions of Lattice Gauge Theories. He next discusses polarization phenomena present in charmed baryon decay. Heavy Quark Effective Theory predicts that the daughter baryon will recoil from the charmed parent with nearly 100% left-handed polarization, which is in excellent agreement with present data. He concludes by discussing nonleptonic charm decay which is traditionally analyzed in a factorization framework applicable to two-body and quasi-two-body nonleptonic decays. This discussion emphasizes the important role of final state interactions in influencing both the observed decay width of various two-body final states as well as modifying the interference between interfering resonance channels which contribute to specific multibody decays. 50 refs., 77 figs

Towards an effective bilocal theory from QCD in a background

International Nuclear Information System (INIS)

Magpantay, J.A.

1982-05-01

Using the path integral, we show how we can get background gauge invariant bilocals (to be identified with mesons) from QCD in a nontrivial ground state. We discuss in this paper mainly the formal manipulations, especially how to deal with the zero modes. We also discuss the large N limit of QCD in a background. (author)

Nonperturbative determination of the QCD potential at O(1/m)

International Nuclear Information System (INIS)

Koma, Y.; Koma, M.; Wittig, H.

2006-07-01

The relativistic correction to the QCD static inter-quark potential at O(1/m) is investigated nonperturbatively for the first time by using lattice Monte Carlo QCD simulations. The correction is found to be comparable with the Coulombic term of the static potential when applied to charmonium, and amounts to 26% of the Coulombic term for bottomonium. (Orig.)

Gluon structure function for deeply inelastic scattering with nucleus in QCD

Energy Technology Data Exchange (ETDEWEB)

Ayala Filho, Alvaro L; Ducati, M.B. Gay [Rio Grande do Sul Univ., Porto Alegre, RS (Brazil). Inst. de Fisica; Levin, Eugene [Centro Brasileiro de Pesquisas Fisicas (CBPF), Rio de Janeiro, RJ (Brazil); [Petersburg Nuclear Physics Institute, Gatchina (Russian Federation). Theory Dept.

1995-06-01

In this talk we present the first calculation of the gluon structure function for nucleus in QCD. We discuss the Glauber formula for the gluon structure function and the violation of this simple approach that we anticipate in QCD. (author). 10 refs, 4 figs.

Improved methods for the study of hadronic physics from lattice QCD

International Nuclear Information System (INIS)

Orginos, Kostas; Richards, David

2015-01-01

The solution of quantum chromodynamics (QCD) on a lattice provides a first-principles method for understanding QCD in the low-energy regime, and is thus an essential tool for nuclear physics. The generation of gauge configurations, the starting point for lattice calculations, requires the most powerful leadership-class computers available. However, to fully exploit such leadership-class computing requires increasingly sophisticated methods for obtaining physics observables from the underlying gauge ensembles. In this paper, we describe a variety of recent methods that have been used to advance our understanding of the spectrum and structure of hadrons through lattice QCD. (paper)

Improved methods for the study of hadronic physics from lattice QCD

Energy Technology Data Exchange (ETDEWEB)

Orginos, Kostas [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); College of William and Mary, Williamsburg, VA (United States); Richards, David [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)

2015-02-05

The solution of QCD on a lattice provides a first-principles method for understanding QCD in the low-energy regime, and is thus an essential tool for nuclear physics. The generation of gauge configurations, the starting point for lattice calculations, requires the most powerful leadership-class computers available. However, to fully exploit such leadership-class computing requires increasingly sophisticated methods for obtaining physics observables from the underlying gauge ensembles. In this study, we describe a variety of recent methods that have been used to advance our understanding of the spectrum and structure of hadrons through lattice QCD.

Towards finite density QCD with Taylor expansions

International Nuclear Information System (INIS)

Karsch, F.; Schaefer, B.-J.; Wagner, M.; Wambach, J.

2011-01-01

Convergence properties of Taylor expansions of observables, which are also used in lattice QCD calculations at non-zero chemical potential, are analyzed in an effective N f =2+1 flavor Polyakov quark-meson model. A recently developed algorithmic technique allows the calculation of higher-order Taylor expansion coefficients in functional approaches. This novel technique is for the first time applied to an effective N f =2+1 flavor Polyakov quark-meson model and the findings are compared with the full model solution at finite densities. The results are used to discuss prospects for locating the QCD phase boundary and a possible critical endpoint in the phase diagram.

Status and prospects for the calculation of hadron structure from lattice QCD

International Nuclear Information System (INIS)

Renner, Dru B.

2010-02-01

Lattice QCD calculations of hadron structure are a valuable complement to many experimental programs as well as an indispensable tool to understand the dynamics of QCD. I present a focused review of a few representative topics chosen to illustrate both the challenges and advances of our community: the momentum fraction, axial charge and charge radius of the nucleon. I will discuss the current status of these calculations and speculate on the prospects for accurate calculations of hadron structure from lattice QCD. (orig.)

Finite temperature and chemical potential in lattice QCD and its critical point

International Nuclear Information System (INIS)

Fodor, Z.

2002-01-01

We propose a method to study lattice QCD at finite temperature (T) and chemical potential (μ). We compare the method with direct results and with the Glasgow method by using n f =4 QCD at Im(μ)≠0. We locate the critical endpoint (E) of QCD on the Re(μ)-T plane. We use n f =2+1 dynamical staggered quarks with semi-realistic masses on L t =4 lattices. Our results are based on O(10 3 - 10 4 ) configurations. (orig.)

Introduction to QCD

OpenAIRE

Skands, Peter

2012-01-01

These lectures were originally given at TASI and are directed at a level suitable for graduate students in High Energy Physics. They are intended to give an introduction to the theory and phenomenology of quantum chromodynamics (QCD), focusing on collider physics applications. The aim is to bring the reader to a level where informed decisions can be made concerning different approaches and their uncertainties. The material is divided into five main areas: 1) fundamentals, 2) fixed-order pertu...

Two-color QCD via dimensional reduction

Czech Academy of Sciences Publication Activity Database

Zhang, T.; Brauner, Tomáš; Kurkela, A.; Vuorinen, A.

2012-01-01

Roč. 2012, č. 139 (2012), s. 1-16 ISSN 1126-6708 Institutional support: RVO:61389005 Keywords : thermal field theory * QCD * confinement Subject RIV: BE - Theoretical Physics Impact factor: 5.618, year: 2012

Fundamental parameters of QCD from non-perturbative methods for two and four flavors

International Nuclear Information System (INIS)

Marinkovic, Marina

2013-01-01

The non-perturbative formulation of Quantumchromodynamics (QCD) on a four dimensional space-time Euclidean lattice together with the finite size techniques enable us to perform the renormalization of the QCD parameters non-perturbatively. In order to obtain precise predictions from lattice QCD, one needs to include the dynamical fermions into lattice QCD simulations. We consider QCD with two and four mass degenerate flavors of O(a) improved Wilson quarks. In this thesis, we improve the existing determinations of the fundamental parameters of two and four flavor QCD. In four flavor theory, we compute the precise value of the Λ parameter in the units of the scale L max defined in the hadronic regime. We also give the precise determination of the Schroedinger functional running coupling in four flavour theory and compare it to the perturbative results. The Monte Carlo simulations of lattice QCD within the Schroedinger Functional framework were performed with a platform independent program package Schroedinger Funktional Mass Preconditioned Hybrid Monte Carlo (SF-MP-HMC), developed as a part of this project. Finally, we compute the strange quark mass and the Λ parameter in two flavour theory, performing a well-controlled continuum limit and chiral extrapolation. To achieve this, we developed a universal program package for simulating two flavours of Wilson fermions, Mass Preconditioned Hybrid Monte Carlo (MP-HMC), which we used to run large scale simulations on small lattice spacings and on pion masses close to the physical value.

Évaluation des pratiques agricoles des légumes feuilles : le cas des ...

African Journals Online (AJOL)

SARAH

30 sept. 2017 ... ... de Biochimie et Immunologie Appliquée, Centre de Recherche en Sciences Biologiques, Alimentaires et .... l'intoxication des agriculteurs et des consommateurs, ... source d'alimentation en eau et au pouvoir d'achat des.

Holographic study of the QCD matter under external conditions

Directory of Open Access Journals (Sweden)

Katanaeva Alisa

2017-01-01

We use methods of the bottom-up AdS/QCD approach to bring out the phase structure of several holographic models in which transition to a deconfined phase is related to a (first order Hawking-Page phase transition. The impact of phenomenological model parameters on the critical temperature and chemical potential is studied in detail. Comparison of the model predictions with results of experimental investigations, lattice QCD simulations and other methods is also done.

CPsup(N-1) model: a toy model for QCD

International Nuclear Information System (INIS)

Cant, R.J.; Davis, A.C.

1979-01-01

The authors examine the CP 2 sup(N-1) models and discuss their relevance as toy models for QCD 4 . Specifically, they study the role of instantons, theta vacua, and confinement in the 1/N expansion. The results, and comparisons with other two-dimensional models, suggest that most of the interesting features of these models are peculiarities of two-dimensional space-time and cannot be expected to reappear in QCD 4 . (Auth.)

Two-loop off-shell QCD amplitudes in FDR

CERN Document Server

Page, Ben

2015-01-01

We link the FDR treatment of ultraviolet (UV) divergences to dimensional regularization up to two loops in QCD. This allows us to derive the one-loop and two-loop coupling constant and quark mass shifts necessary to translate infrared finite quantities computed in FDR to the MSbar renormalization scheme. As a by-product of our analysis, we solve a problem analogous to the breakdown of unitarity in the Four Dimensional Helicity (FDH) method beyond one loop. A fix to FDH is then presented that preserves the renormalizability properties of QCD without introducing evanescent quantities.

QCD effects on the event structure in leptoproduction

International Nuclear Information System (INIS)

Bengtsson, M.; Sjoestrand, T.

1988-01-01

Perturbative QCD corrections to leptoproduction events can be introduced either in the form of matrix elements or of parton showers. Each of these approaches has its advantages and disadvantages, making a comparison of the two interesting. At present energies, both methods can be made to agree reasonably well with data, whereas differences appear at higher energies. The influence of these QCD effects on the expected event structure at ep colliders, HERA in particular, is investigated in detail. This includes multiplicity and momentum distributions transverse momentum flow and correlations, as well as jet properties. (orig.)

Developments in perturbative QCD? challenges from collider physics

Energy Technology Data Exchange (ETDEWEB)

Zeppenfeld, Dieter [Valencia Univ. (Spain). Dept. de Fisica Teorica]. E-mail: dieter@phenom.physics.wisc.edu

1996-07-01

The search for new phenomena at hadron colliders requires a good understanding of QCD processes. The analysis of multi-jet signatures in the top quark search at the Tevatron is one example, forward jet tagging and rapidity gap techniques in the analysis of weak boson scattering events at the LH C will be another important application. These topics are discussed in the context of multi-parton/multi-jet QCD processes. Also described are some of the calculation tools, like amplitude techniques and automatic code generation for tree level processes. (author)

Chiral symmetry breaking parameters from QCD sum rules

Energy Technology Data Exchange (ETDEWEB)

Mallik, S [Karlsruhe Univ. (T.H.) (Germany, F.R.). Inst. fuer Theoretische Kernphysik; Bern Univ. (Switzerland). Inst. fuer Theoretische Physik)

1982-10-04

We obtain new QCD sum rules by considering vacuum expectation values of two-point functions, taking all the five quark bilinears into account. These sum rules are employed to extract values of different chiral symmetry breaking parameters in QCD theory. We find masses of light quarks, m=1/2msub(u)+msub(d)=8.4+-1.2 MeV, msub(s)=205+-65 MeV. Further, we obtain corrections to certain soft pion (kaon) PCAC relations and the violation of SU(3) flavour symmetry by the non-strange and strange quark-antiquark vacuum condensate.

Anomalous couplings in WZ production beyond NLO QCD

Energy Technology Data Exchange (ETDEWEB)

Campanario, Francisco; Roth, Robin; Zeppenfeld, Dieter [Institute for Theoretical Physics, KIT, Karlsruhe (Germany); Sapeta, Sebastian [CERN PH-TH, Geneva (Switzerland)

2016-07-01

We study WZ production with anomalous couplings (AC) at anti nNLO QCD using the LoopSim method in combination with the Monte Carlo program VBFNLO. Higher order corrections to WZ production are dominated by additional hard jet radiation. Those contributions are insensitive to AC and should thus be suppressed in analyses. We do this using a dynamical jet veto based on the transverse energy of the QCD and EW final state particles. This removes jet dominated events without introducing problematic logs like a fixed p{sub T} jet veto.

Parallel tempering in full QCD with Wilson fermions

International Nuclear Information System (INIS)

Ilgenfritz, E.-M.; Kerler, W.; Mueller-Preussker, M.; Stueben, H.

2002-01-01

We study the performance of QCD simulations with dynamical Wilson fermions by combining the hybrid Monte Carlo algorithm with parallel tempering on 10 4 and 12 4 lattices. In order to compare tempered with standard simulations, covariance matrices between subensembles have to be formulated and evaluated using the general properties of autocorrelations of the parallel tempering algorithm. We find that rendering the hopping parameter κ dynamical does not lead to an essential improvement. We point out possible reasons for this observation and discuss more suitable ways of applying parallel tempering to QCD

Developments in perturbative QCD? challenges from collider physics

International Nuclear Information System (INIS)

Zeppenfeld, Dieter

1996-01-01

The search for new phenomena at hadron colliders requires a good understanding of QCD processes. The analysis of multi-jet signatures in the top quark search at the Tevatron is one example, forward jet tagging and rapidity gap techniques in the analysis of weak boson scattering events at the LH C will be another important application. These topics are discussed in the context of multi-parton/multi-jet QCD processes. Also described are some of the calculation tools, like amplitude techniques and automatic code generation for tree level processes. (author)

Light-cone quantized QCD and novel hadron phenomenology

International Nuclear Information System (INIS)

Brodsky, S.J.

1997-09-01

The authors reviews progress made in solving gauge theories such as collinear quantum chromodynamics using light-cone Hamiltonian methods. He also shows how the light-cone Fock expansion for hadron wavefunctions can be used to compute operator matrix elements such as decay amplitudes, form factors, distribution amplitudes, and structure functions, and how it provides a tool for exploring novel features of QCD. The author also reviews commensurate scale relations, leading-twist identities which relate physical observables to each other, thus eliminating renormalization scale and scheme ambiguities in perturbative QCD predictions

Scaling violation in QCD

International Nuclear Information System (INIS)

Furmanski, W.

1981-08-01

The effects of scaling violation in QCD are discussed in the perturbative scheme, based on the factorization of mass singularities in the light-like gauge. Some recent applications including the next-to-leading corrections are presented (large psub(T) scattering, numerical analysis of the leptoproduction data). A proposal is made for extending the method on the higher twist sector. (author)

New results in perturbative QCD

International Nuclear Information System (INIS)

Ellis, R.K.

1986-01-01

Three topics in perturbative QCD important for Super-collider physics are reviewed. The topics are: 1. (2 → 2) jet phenomena calculated in O(αs 3 ). 2. New techniques for the calculation of tree graphs. 3. Color coherence in jet phenomena. 31 references, 6 figures

Modelisation des effets physico-techniques pour la conception des ...

African Journals Online (AJOL)

automatisation dans les installations industrielles a besoin d'une régulation automatique des commandes des processus technologiques pour lesquelles certaines contraintes sont à relever compte tenu des exigences des innovations scientifiques de ...

The QCD/SM Working Group: Summary Report

International Nuclear Information System (INIS)

Dobbs, M.

2004-01-01

Among the many physics processes at TeV hadron colliders, we look most eagerly for those that display signs of the Higgs boson or of new physics. We do so however amid an abundance of processes that proceed via Standard Model (SM) and in particular Quantum Chromodynamics (QCD) interactions, and that are interesting in their own right. Good knowledge of these processes is required to help us distinguish the new from the known. Their theoretical and experimental study teaches us at the same time more about QCD/SM dynamics, and thereby enables us to further improve such distinctions. This is important because it is becoming increasingly clear that the success of finding and exploring Higgs boson physics or other New Physics at the Tevatron and LHC will depend significantly on precise understanding of QCD/SM effects for many observables. To improve predictions and deepen the study of QCD/SM signals and backgrounds was therefore the ambition for our QCD/SM working group at this Les Houches workshop. Members of the working group made significant progress towards this on a number of fronts. A variety of tools were further developed, from methods to perform higher order perturbative calculations or various types of resummation, to improvements in the modeling of underlying events and parton showers. Furthermore, various precise studies of important specific processes were conducted. A significant part of the activities in Les Houches revolved around Monte Carlo simulation of collision events. A number of contributions in this report reflect the progress made in this area. At present a large number of Monte Carlo programs exist, each written with a different purpose and employing different techniques. Discussions in Les Houches revealed the need for an accessible primer on Monte Carlo programs, featuring a listing of various codes, each with a short description, but also providing a low-level explanation of the underlying methods. This primer has now been compiled and a

QCD and panti p collider physics

International Nuclear Information System (INIS)

Altarelli, G.

1983-01-01

The relevance for QCD of experiments at the SPS collider rests on the possibility they offer of testing parton dynamics in a new and highly non trivial configuration. For example, hadron-hadron interactions in the deep inelastic, large Psub(perpendicular to), region are non linear in parton densities. Also the relevant predictions cannot be derived by less committed formulations than the explicit QCD improved parton model, as for example light cone dominance and operator expansion. This complexity, which is important for providing qualitatively new testing grounds is however paid for by a loss of precision in predictive power. In addition to that, panti p collisions are also important as jet sources with an energy scale comparable to that of an e + e - ring with beam energy up to 50 GeV and more. (orig./HSI)

QCD studies at the hadron colliders

International Nuclear Information System (INIS)

Flaugher, B.L.

1990-01-01

Two hadron collider experiments are actively pursuing QCD jet analyses. They are CDF, with a √s = 1800 GeV, and UA2, with a √s = 630 GeV. Recent results from these collaborations are discussed. The inclusive jet spectrum, dijet mass and angular distribution are compared to QCD predictions and used to set limits on quark substructure. Data from both experiments are compared to the O(α s 3 ) calculations for the inclusive jet cross section. Studies of 3-jet, 4-jet and 5-jet events are described. A limit is set on the cross section for double parton scattering from the UA2 4-jet analysis. The inclusive photon cross section has been measured by both CDF and UA2 and is compared to theoretical predictions. 13 refs., 17 figs., 1 tab

Effective Chiral Lagrangians and Lattice QCD

CERN Document Server

Heitger, J; Wittig, H; Heitger, Jochen; Sommer, Rainer; Wittig, Hartmut

2000-01-01

We propose a general method to obtain accurate estimates for some of the "low-energy constants" in the one-loop effective chiral Lagrangian by means of simulating lattice QCD. In particular, the method is sensitive to those constants whose values are required to test the hypothesis of a massless up-quark. Initial tests performed in the quenched approximation confirm that good statistical precision can be achieved. As a byproduct we obtain an accurate estimate for the ratio of pseudoscalar decay constants, F_K/F_pi, in the quenched approximation, which lies 10% below the experimental result. The quantities that serve to extract the low-energy constants also allow a test of the scaling behaviour of different discretizations of QCD and a search for the effects of dynamical quarks.

Lattice QCD at finite density. An introductory review

International Nuclear Information System (INIS)

Muroya, Shin; Nakamura, Atushi; Nonaka, Chiho; Takaishi, Tetsuya

2003-01-01

This is a pedagogical review of the lattice study of finite density QCD. It is intended to provide the minimum necessary content, so that it may be used as an introduction for newcomers to the field and also for those working in nonlattice areas. After a brief introduction in which we discuss the reasons that finite density QCD is an active and important subject, we present the fundamental formulae that are necessary for the treatment given in the following sections. Next, we survey lattice QCD simulational studies of system with small chemical potentials, of which there have been several prominent works reported recently. Then, two-color QCD calculations are discussed, where we are free from the notorious phase problem and have a chance to consider many new features of finite density QCD. Of special note is the result of recent simulations indicating quark pair condensation and the in-medium effect. Tables of SU(3) and SU(2) lattice simulations at finite baryon density are given. In the next section, we survey several related works that may represent a starting point of future development, although some of these works have not attracted much attention yet. This material is described in a pedagogical manner. Starting from a simple 2-d model, we briefly discuss a lattice analysis of the NJL model. We describe a non-perturbative analytic approach, i.e., the strong coupling approximation method and some results. The canonical ensemble approach, instead of the usual canonical ensemble may be another route to reach high density. We examine the density of state method and show that this old idea includes the recently proposed factorization method. An alternative method, the complex Langevin equation, and an interesting model, the finite isospin model, are also discussed. We give brief comments on a partial sum with respect to Z 3 symmetry and the meron-cluster algorithm, which might solve the sign problem partially or completely. In the Appendix, we discuss several

Electromagnetic Form Factors of Hadrons in Dual-Large Nc QCD

International Nuclear Information System (INIS)

Dominguez, C. A.

2011-01-01

In this talk, results are presented of determinations of electromagnetic form factors of hadrons (pion, proton, and Δ(1236)) in the framework of Dual-Large N c QCD (Dual-QCD ∞ ). This framework improves considerably tree-level VMD results by incorporating an infinite number of zero-width resonances, with masses and couplings fixed by the dual-resonance (Veneziano-type) model.

Jets and QCD

International Nuclear Information System (INIS)

Ali, A.; Kramer, G.

2010-12-01

The observation of quark and gluon jets has played a crucial role in establishing Quantum Chromodynamics [QCD] as the theory of the strong interactions within the Standard Model of particle physics. The jets, narrowly collimated bundles of hadrons, reflect configurations of quarks and gluons at short distances. Thus, by analysing energy and angular distributions of the jets experimentally, the properties of the basic constituents of matter and the strong forces acting between them can be explored. In this review we summarise the properties of quark and gluon jets and the impact of their observation on Quantum Chromodynamics, primarily the discovery of the gluons as the carriers of the strong force. Focusing on these basic points, jets in e + e - collisions will be in the foreground of the discussion. In addition we will delineate the role of jets as tools for exploring other particle aspects in ep and pp/p anti p collisions - quark and gluon densities in protons, measurements of the QCD coupling, fundamental 2-2 quark/gluon scattering processes, but also the impact of jet decays of top quarks, and W ± ,Z bosons on the electroweak sector. The presentation to a large extent is formulated in a non-technical language with the intent to recall the significant steps historically and convey the significance of this field also to communities beyond high energy physics. (orig.)

Jets and QCD

Energy Technology Data Exchange (ETDEWEB)

Ali, A. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Kramer, G. [Hamburg Univ. (Germany). II. Inst. fuer Theoretische Physik

2010-12-15

The observation of quark and gluon jets has played a crucial role in establishing Quantum Chromodynamics [QCD] as the theory of the strong interactions within the Standard Model of particle physics. The jets, narrowly collimated bundles of hadrons, reflect configurations of quarks and gluons at short distances. Thus, by analysing energy and angular distributions of the jets experimentally, the properties of the basic constituents of matter and the strong forces acting between them can be explored. In this review we summarise the properties of quark and gluon jets and the impact of their observation on Quantum Chromodynamics, primarily the discovery of the gluons as the carriers of the strong force. Focusing on these basic points, jets in e{sup +}e{sup -} collisions will be in the foreground of the discussion. In addition we will delineate the role of jets as tools for exploring other particle aspects in ep and pp/p anti p collisions - quark and gluon densities in protons, measurements of the QCD coupling, fundamental 2-2 quark/gluon scattering processes, but also the impact of jet decays of top quarks, and W{sup {+-}},Z bosons on the electroweak sector. The presentation to a large extent is formulated in a non-technical language with the intent to recall the significant steps historically and convey the significance of this field also to communities beyond high energy physics. (orig.)

The $\\Delta I = 1/2 $ Rule in the Light of Two-Dimensional QCD

CERN Document Server

Ellis, John R.; Hanany, Amihay; Karliner, Marek; Ellis, John; Frishman, Yitzhak; Hanany, Amihay; Karliner, Marek

1997-01-01

We calculate in QCD$_2$ the ratios of baryonic matrix elements of $\\Delta I = 2$ and $\\Delta I = 0$ four-fermion operators, with a view to understanding better the mechanism of $\\Delta I = 1/2$ enhancement in QCD$_4$. We find relatively small suppressions of both the scalar-scalar and vector-vector these results, in view of a suggestion that gluon condensation may be an important contributing factor in the $\\Delta I = 1/2$ enhancement seen in QCD$_4$. At the technical level, our calculation of the vector-vector operator matrix element requires a treatment of the time dependence of the QCD$_2$ soliton which had not been developed in previous phenomenological calculations within this model.

Higher order QCD corrections in exclusive charmless B decays

International Nuclear Information System (INIS)

Bell, G.

2006-10-01

We discuss exclusive charmless B decays within the Standard Model of particle physics. These decays play a central role in the on-going process to constrain the parameters of the CKM matrix and to clarify the nature of CP violation. In order to exploit the rich source of data that is currently being collected at the experiments, a systematic theoretical treatment of the complicated hadronic dynamics is strongly desired. QCD Factorization represents a model-independent framework to compute hadronic matrix elements from first principles. It is based on a power expansion in Λ QCD /m b and allows for the systematic implementation of perturbative corrections. In particular, we consider hadronic two-body decays as B → ππ and perform a conceptual analysis of heavy-to-light form factors which encode the strong interaction effects in semi-leptonic decays as B → πlν. Concerning the hadronic decays we compute NNLO QCD corrections which are particularly important with respect to strong interaction phases and hence direct CP asymmetries. On the technical level, we perform a 2-loop calculation which is based on an automatized reduction algorithm and apply sophisticated techniques for the calculation of loop-integrals. We indeed find that the considered quantities are well-defined as predicted by QCD Factorization, which is the result of a highly complicated subtraction procedure. We present results for the imaginary part of the topological tree amplitudes and observe that the considered corrections are substantial. The calculation of the real part of the amplitudes is far more complicated and we present a preliminary result which is based on certain simplifications. Our calculation is one part of the full NNLO analysis of nonleptonic B decays within QCD Factorization which is currently pursued by various groups. In our conceptual analysis of the QCD dynamics in heavy-to-light transitions we consider form factors between non-relativistic bound states which can be

Higher order QCD corrections in exclusive charmless B decays

Energy Technology Data Exchange (ETDEWEB)

Bell, G.

2006-10-15

We discuss exclusive charmless B decays within the Standard Model of particle physics. These decays play a central role in the on-going process to constrain the parameters of the CKM matrix and to clarify the nature of CP violation. In order to exploit the rich source of data that is currently being collected at the experiments, a systematic theoretical treatment of the complicated hadronic dynamics is strongly desired. QCD Factorization represents a model-independent framework to compute hadronic matrix elements from first principles. It is based on a power expansion in {lambda}{sub QCD}/m{sub b} and allows for the systematic implementation of perturbative corrections. In particular, we consider hadronic two-body decays as B {yields} {pi}{pi} and perform a conceptual analysis of heavy-to-light form factors which encode the strong interaction effects in semi-leptonic decays as B {yields} {pi}l{nu}. Concerning the hadronic decays we compute NNLO QCD corrections which are particularly important with respect to strong interaction phases and hence direct CP asymmetries. On the technical level, we perform a 2-loop calculation which is based on an automatized reduction algorithm and apply sophisticated techniques for the calculation of loop-integrals. We indeed find that the considered quantities are well-defined as predicted by QCD Factorization, which is the result of a highly complicated subtraction procedure. We present results for the imaginary part of the topological tree amplitudes and observe that the considered corrections are substantial. The calculation of the real part of the amplitudes is far more complicated and we present a preliminary result which is based on certain simplifications. Our calculation is one part of the full NNLO analysis of nonleptonic B decays within QCD Factorization which is currently pursued by various groups. In our conceptual analysis of the QCD dynamics in heavy-to-light transitions we consider form factors between non

Hadron physics from lattice QCD

Energy Technology Data Exchange (ETDEWEB)

Schaefer, Andreas [Regensburg Univ. (Germany). Inst. for Theoretical Physics

2016-11-01

Particle physics experiments at modern high luminosity particle accelerators achieve orders of magnitude higher count rates than what was possible ten or twenty years ago. This extremely large statistics allows to draw far reaching conclusions even from minute signals, provided that these signals are well understood by theory. This is, however, ever more difficult to achieve. Presently, technical and scientific progress in general and experimental progress in particle physics in particular, shows typically an exponential growth rate. For example, data acquisition and analysis are, among many other factor, driven by the development of ever more efficient computers and thus by Moore's law. Theory has to keep up with this development by also achieving an exponential increase in precision, which is only possible using powerful computers. This is true for both types of calculations, analytic ones as, e.g., in quantum field perturbation theory, and purely numerical ones as in Lattice QCD. As stated above such calculations are absolutely indispensable to make best use of the extremely costly large particle physics experiments. Thus, it is economically reasonable to invest a certain percentage of the cost of accelerators and experiments in related theory efforts. The basic ideas behind Lattice QCD simulations are the following: Because quarks and gluons can never be observed individually but are always ''confined'' into colorless hadrons, like the proton, all quark-gluon states can be expressed in two different systems of basis states, namely in a quark-gluon basis and the basis of hadron states. The proton, e.g., is an eigenstate of the latter, a specific quark-gluon configuration is part of the former. In the quark-gluon basis a physical hadron, like a proton, is given by an extremely complicated multi-particle wave function containing all effects of quantum fluctuations. This state is so complicated that it is basically impossible to model it

Vecteurs Singuliers des Theories des Champs Conformes Minimales

Science.gov (United States)

Benoit, Louis

En 1984 Belavin, Polyakov et Zamolodchikov revolutionnent la theorie des champs en explicitant une nouvelle gamme de theories, les theories quantiques des champs bidimensionnelles invariantes sous les transformations conformes. L'algebre des transformations conformes de l'espace-temps presente une caracteristique remarquable: en deux dimensions elle possede un nombre infini de generateurs. Cette propriete impose de telles conditions aux fonctions de correlations qu'il est possible de les evaluer sans aucune approximation. Les champs des theories conformes appartiennent a des representations de plus haut poids de l'algebre de Virasoro, une extension centrale de l'algebre conforme du plan. Ces representations sont etiquetees par h, le poids conforme de leur vecteur de plus haut poids, et par la charge centrale c, le facteur de l'extension centrale, commune a toutes les representations d'une meme theorie. Les theories conformes minimales sont constituees d'un nombre fini de representations. Parmi celles-ci se trouvent des theories unitaires dont les representation forment la serie discrete de l'algebre de Virasoro; leur poids h a la forme h_{p,q}(m)=[ (p(m+1) -qm)^2-1] (4m(m+1)), ou p,q et m sont des entiers positifs et p+q= 2. Ces representations possedent un sous-espace invariant engendre par deux sous-representations avec h_1=h_{p,q} + pq et h_2=h_{p,q} + (m-p)(m+1-q) dont chacun des vecteurs de plus haut poids portent le nom de vecteur singulier et sont notes respectivement |Psi _{p,q}> et |Psi_{m-p,m+1-q}>. . Les theories super-conformes sont une version super-symetrique des theories conformes. Leurs champs appartiennent a des representation de plus haut poids de l'algebre de Neveu-Schwarz, une des deux extensions super -symetriques de l'algebre de Virasoro. Les theories super -conformes minimales possedent la meme structure que les theories conformes minimales. Les representations sont elements de la serie h_{p,q}= [ (p(m+2)-qm)^2-4] /(8m(m+2)) ou p,q et m sont

Reggeon interactions in perturbative QCD

International Nuclear Information System (INIS)

Kirschner, R.

1994-08-01

We study the pairwise interaction of reggeized gluons and quarks in the Regge limit of perturbative QCD. The interactions are represented as integral kernels in the transverse momentum space and as operators in the impact parameter space. We observe conformal symmetry and holomorphic factorization in all cases. (orig.)

Planar experiment as possible method of QCD tube investigation

International Nuclear Information System (INIS)

Levintov, I.I.

1989-01-01

It is proposed to distinguish the plane events with Δq tr /q-bar tr tr /q-bar tr at azimuth-independent distribution of transverse momenta in the phase volume was calculated. The arguments, owing to which the probability of plane event observation grows sufficiently at fragmentation of isolated QCD strings, are presented. Probability of formation of plane events, conditioned by isolated QCD string fragmentation, decreases with momentum as ∼ P lab -1/2 . 6 refs.; 1 fig

Instantons and quark zero modes in AdS/QCD

DEFF Research Database (Denmark)

Bechi, Jacopo

2009-01-01

In this paper the quark zero modes creation effect is studied in the context of the AdS/QCD approach. This effect is generated, in presence of instantons, by a new that can be added in the bulk.......In this paper the quark zero modes creation effect is studied in the context of the AdS/QCD approach. This effect is generated, in presence of instantons, by a new that can be added in the bulk....

Heavy-quark production in gluon fusion at two loops in QCD

International Nuclear Information System (INIS)

Czakon, M.

2007-07-01

We present the two-loop virtual QCD corrections to the production of heavy quarks in gluon fusion. The results are exact in the limit when all kinematical invariants are large compared to the mass of the heavy quark up to terms suppressed by powers of the heavy-quark mass. Our derivation uses a simple relation between massless and massive QCD scattering amplitudes as well as a direct calculation of the massive amplitude at two loops. The results presented here together with those obtained previously for quark-quark scattering form important parts of the next-to-next-to-leading order QCD corrections to heavy-quark production in hadron-hadron collisions. (orig.)

Form factors and QCD in spacelike and timelike region

International Nuclear Information System (INIS)

A.P. Bakulev; A.V. Radyushkin; N.G. Stefanis

2000-01-01

The authors analyze the basic hard exclusive processes: πγ * γ-transition, pion and nucleon electromagnetic form factors, and discuss the analytic continuation of QCD formulas from the spacelike q 2 2 > 0 of the relevant momentum transfers. They describe the construction of the timelike version of the coupling constant α s . They show that due to the analytic continuation of the collinear logarithms each eigenfunction of the evolution equation acquires a phase factor and investigate the resulting interference effects which are shown to be very small. They found no sources for the K-factor-type enhancements in the perturbative QCD contribution to the hadronic form factors. To study the soft part of the pion electromagnetic form factor, they use a QCD sum rule inspired model and show that there are non-canceling Sudakov double logarithms which result in a K-factor-type enhancement in the timelike region

Form factors and QCD in spacelike and timelike regions

International Nuclear Information System (INIS)

Bakulev, A. P.; Radyushkin, A. V.; Stefanis, N. G.

2000-01-01

We analyze the basic hard exclusive processes, the πγ * γ-transition and the pion and nucleon electromagnetic form factors, and discuss the analytic continuation of QCD formulas from the spacelike q 2 2 >0 of the relevant momentum transfers. We describe the construction of the timelike version of the coupling constant α s . We show that due to the analytic continuation of the collinear logarithms, each eigenfunction of the evolution equation acquires a phase factor and investigate the resulting interference effects which are shown to be very small. We find no sources for the K-factor-type enhancements in the perturbative QCD contribution to the hadronic form factors. To study the soft part of the pion electromagnetic form factor, we use a QCD sum rule inspired model and show that there are noncanceling Sudakov double logarithms which result in a K-factor-type enhancement in the timelike region

One-dimensional model for QCD at high energy

International Nuclear Information System (INIS)

Iancu, E.; Santana Amaral, J.T. de; Soyez, G.; Triantafyllopoulos, D.N.

2007-01-01

We propose a stochastic particle model in (1+1) dimensions, with one dimension corresponding to rapidity and the other one to the transverse size of a dipole in QCD, which mimics high-energy evolution and scattering in QCD in the presence of both saturation and particle-number fluctuations, and hence of pomeron loops. The model evolves via non-linear particle splitting, with a non-local splitting rate which is constrained by boost-invariance and multiple scattering. The splitting rate saturates at high density, so like the gluon emission rate in the JIMWLK evolution. In the mean field approximation obtained by ignoring fluctuations, the model exhibits the hallmarks of the BK equation, namely a BFKL-like evolution at low density, the formation of a traveling wave, and geometric scaling. In the full evolution including fluctuations, the geometric scaling is washed out at high energy and replaced by diffusive scaling. It is likely that the model belongs to the universality class of the reaction-diffusion process. The analysis of the model sheds new light on the pomeron loops equations in QCD and their possible improvements

QCD Factorizations in Exclusive γ*γ*→ρL0ρL0

International Nuclear Information System (INIS)

Pire, B.; Segond, M.; Szymanowski, L.; Wallon, S.

2008-01-01

The exclusive process e + e - →e + e - ρ L 0 ρ L 0 allows to study various dynamics and factorization properties of perturbative QCD. At moderate energy, we demonstrate how collinearQCD factorization emerges, involving either generalized distribution amplitudes (GDA) or transition distribution amplitudes (TDA). At higher energies, in the Regge limit of QCD, we show that it offers a promising probe of the BFKL resummation effects to be studied at ILC

Flavor-singlet baryons in the graded symmetry approach to partially quenched QCD

Science.gov (United States)

Hall, Jonathan M. M.; Leinweber, Derek B.

2016-11-01

Progress in the calculation of the electromagnetic properties of baryon excitations in lattice QCD presents new challenges in the determination of sea-quark loop contributions to matrix elements. A reliable estimation of the sea-quark loop contributions represents a pressing issue in the accurate comparison of lattice QCD results with experiment. In this article, an extension of the graded symmetry approach to partially quenched QCD is presented, which builds on previous theory by explicitly including flavor-singlet baryons in its construction. The formalism takes into account the interactions among both octet and singlet baryons, octet mesons, and their ghost counterparts; the latter enables the isolation of the quark-flow disconnected sea-quark loop contributions. The introduction of flavor-singlet states enables systematic studies of the internal structure of Λ -baryon excitations in lattice QCD, including the topical Λ (1405 ).

AdS/QCD, Light-Front Holography, and Sublimated Gluons

Energy Technology Data Exchange (ETDEWEB)

Brodsky, Stanley J.; /SLAC; de Teramond, Guy F.; /Costa Rica U.

2012-02-16

The gauge/gravity duality leads to a simple analytical and phenomenologically compelling nonperturbative approximation to the full light-front QCD Hamiltonian - 'Light-Front Holography', which provides a Lorentz-invariant first-approximation to QCD, and successfully describes the spectroscopy of light-quark meson and baryons, their elastic and transition form factors, and other hadronic properties. The bound-state Schroedinger and Dirac equations of the soft-wall AdS/QCD model predict linear Regge trajectories which have the same slope in orbital angular momentum L and radial quantum number n for both mesons and baryons. Light-front holography connects the fifth-dimensional coordinate of AdS space z to an invariant impact separation variable {zeta} in 3+1 space at fixed light-front time. A key feature is the determination of the frame-independent light-front wavefunctions of hadrons - the relativistic analogs of the Schroedinger wavefunctions of atomic physics which allow one to compute form factors, transversity distributions, spin properties of the valence quarks, jet hadronization, and other hadronic observables. One thus obtains a one-parameter color-confining model for hadron physics at the amplitude level. AdS/QCD also predicts the form of the non-perturbative effective coupling {alpha}{sub s}{sup AdS} (Q) and its {beta}-function with an infrared fixed point which agrees with the effective coupling a{sub g1} (Q{sup 2}) extracted from measurements of the Bjorken sum rule below Q{sup 2} < 1 GeV{sup 2}. This is consistent with a flux-tube interpretation of QCD where soft gluons with virtualities Q{sup 2} < 1 GeV{sup 2} are sublimated into a color-confining potential for quarks. We discuss a number of phenomenological hadronic properties which support this picture.

Utilisation sans risque des eaux usées, des excréta et des eaux ...

International Development Research Centre (IDRC) Digital Library (Canada)

Les responsables de ce projet piloteront l'application et l'adaptation des principes directeurs relatifs à l'utilisation sans risque des eaux usées, des excreta et des eaux grises en agriculture et en aquaculture (Guidelines for the Safe Use of Wastewater, Excreta and Greywater in Agriculture and Aquaculture), que ...

Factorization and pion form factor in QCD

International Nuclear Information System (INIS)

Efremov, A.V.; Radyushkin, A.V.

1979-01-01

The behaviour of the pion electromagnetic form factor (EMFF) in the framework of quantum chromodynamics (QCD) is discussed. Pion is considered to be a quark-antiquark bound state. It is proposed to use an OPE description of the bound state structure by matrix elements of certain local gauge-invariant operators. Short-distance quark interactions is proved using a direct analysis of perturbation theory in the α-parametric representation of the Feynman diagrams. It is shown that the short-distance parton picture privides a self-consistent description of the large Q 2 momentum behaviour of the pion EMFF in QCD. Pion EMFF asymptotics is expressed in terms of fu fundamental constants of the theory

A transverse lattice QCD model for mesons

Energy Technology Data Exchange (ETDEWEB)

Patel, Apoorva D.; Ratabole, Raghunath

2004-03-01

QCD is analysed with two light-front continuum dimensions and two transverse lattice dimensions. In the limit of large number of colours and strong transverse gauge coupling, the contributions of light-front and transverse directions factorise in the dynamics, and the theory can be analytically solved in a closed form. An integral equation is obtained, describing the properties of mesons, which generalises the 't Hooft equation by including spin degrees of freedom. The meson spectrum, light-front wavefunctions and form factors can be obtained by solving this equation numerically. These results would be a good starting point to model QCD observables which only weakly depend on transverse directions, e.g. deep inelastic scattering structure functions.

Study of QCD medium by sum rules

Energy Technology Data Exchange (ETDEWEB)

Mallik, S [Saha Institute of Nuclear Physics, Calcutta (India)

1998-08-01

Though it has no analogue in condensed matter physics, the thermal QCD sum rules can, nevertheless, answer questions of condensed matter type about the QCD medium. The ingredients needed to write such sum rules, viz. the operator product expansion and the spectral representation at finite temperature, are reviewed in detail. The sum rules are then actually written for the case of correlation function of two vector currents. Collecting information on the thermal average of the higher dimension operators from other sources, we evaluate these sum rules for the temperature dependent {rho}-meson parameters. Possibility of extracting more information from the combined set of all sum rules from different correlation functions is also discussed. (author) 30 refs., 2 figs.

Effective string theory and QCD scattering amplitudes

International Nuclear Information System (INIS)

Makeenko, Yuri

2011-01-01

QCD string is formed at distances larger than the confinement scale and can be described by the Polchinski-Strominger effective string theory with a nonpolynomial action, which has nevertheless a well-defined semiclassical expansion around a long-string ground state. We utilize modern ideas about the Wilson-loop/scattering-amplitude duality to calculate scattering amplitudes and show that the expansion parameter in the effective string theory is small in the Regge kinematical regime. For the amplitudes we obtain the Regge behavior with a linear trajectory of the intercept (d-2)/24 in d dimensions, which is computed semiclassically as a momentum-space Luescher term, and discuss an application to meson scattering amplitudes in QCD.

Exactly soluble QCD and confinement of quarks

International Nuclear Information System (INIS)

Rusakov, B.

1997-01-01

An exactly soluble non-perturbative model of the pure gauge QCD is derived as a weak coupling limit of the lattice theory in plaquette formulation [B. Rusakov, Phys. Lett. B 398 (1997) 331]. The model represents QCD as a theory of the weakly interacting field strength fluxes. The area law behavior of the Wilson loop average is a direct result of this representation: the total flux through macroscopic loop is the additive (due to the weakness of the interaction) function of the elementary fluxes. The compactness of the gauge group is shown to be the factor which prevents the elementary fluxes contributions from cancellation. There is no area law in the non-compact theory. (orig.)

Future directions for QCD

International Nuclear Information System (INIS)

Bjorken, J.D.

1996-10-01

New directions for exploring QCD at future high-energy colliders are sketched. These include jets within jets. BFKL dynamics, soft and hard diffraction, searches for disoriented chiral condensate, and doing a better job on minimum bias physics. The new experimental opportunities include electron-ion collisions at HERA, a new collider detector at the C0 region of the TeVatron, and the FELIX initiative at the LHC

WORKSHOP QCD at 20

International Nuclear Information System (INIS)

Nachtmann, O.

1992-01-01

The modern theory of strong interactions - Quantum Chromodynamics (QCD), where quarks and gluons carrying the 'colour' quantum number play the essential role, is twenty years old. This birthday was duly celebrated at RWTH Aachen from 9-13 June, where recurring themes were - what has been achieved in the past twenty years?, where do we stand?, and what are the perspectives for the future?

String dynamics in QCD

International Nuclear Information System (INIS)

Gervais, J.L.; Neveu, A.

1980-01-01

Recent works of the authors on string interpretation of the Wilson loop operators in QCD are reviewed in a self-contained fashion. Although most of the results habe already appeared in print, some new material is presented in renormalization of the Wilson loop operator and on the use of light-cone expansion to derive a linear string-like equation in light-cone formalism. (orig.)

QCD in hadron-hadron collisions

International Nuclear Information System (INIS)

Albrow, M.

1997-03-01

Quantum Chromodynamics provides a good description of many aspects of high energy hadron-hadron collisions, and this will be described, along with some aspects that are not yet understood in QCD. Topics include high E T jet production, direct photon, W, Z and heavy flavor production, rapidity gaps and hard diffraction

An overview of lattice QCD

International Nuclear Information System (INIS)

Woloshyn, R.M.

1988-03-01

The basic concepts of the Lagrangian formulation of lattice field theory are discussed. The Wilson and staggered schemes for dealing with fermions on the lattice are described. Some recent results for hadron masses and vector and axial vector current matrix elements in lattice QCD are reviewed. (Author) (118 refs., 16 figs.)

The gauge-independent QCD effective charge

International Nuclear Information System (INIS)

Watson, N.J.

1999-01-01

It is shown how the QCD concept of a gauge-, scale-and scheme-independent one-loop effective charge can be extended directly at the diagrammatic level to QCD, thus justifying explicitly the 'naive non-abelialization' prescription used in renormalon calculus. It is first argued that, for one-shell external fields and at the strictly one-loop level, the required gluon self-energy-like function is precisely that obtained from S-matrix elements via the pinch technique. The generalization of the pinch technique to explicitly off-shell processes is then introduced. It is shown how, as a result of a fundamental cancellation among conventional perturbation theory diagrams encoded in the QCD Ward identities, the pinch technique one-loop gluon self-energy iΠ μν ab (q) remains gauge-independent and universal regardless of the fact that the 'external' fields in the given process are off-shell. This demonstration involves a simple technique enabling the isolation in a arbitrary gauge, of iΠ μν ab (q) from subclasses of up to several hundreds diagrams at once. Furthermore, it is shown how this one-loop cancellation mechanism iterates for the subclasses of n-loop diagrams containing implicitly the Dyson chains of n-loop self energies iΠ μν ab (q). The gauge cancellation required for the Dyson summation of iΠ μν ab (q) is thus demonstrated explicitly in the class of ghost-free gauges for all orders n. (authors)

Automated NLO QCD corrections with WHIZARD

International Nuclear Information System (INIS)

Weiss, Christian; Siegen Univ.; Chokoufe Nejad, Bijan; Reuter, Juergen; Kilian, Wolfgang

2015-10-01

We briefly discuss the current status of NLO QCD automation in the Monte Carlo event generator WHIZARD. The functionality is presented for the explicit study of off-shell top quark production with associated backgrounds at a lepton collider.

ANALYSE DES PERCEPTIONS LOCALES ET DES FACTEURS ...

African Journals Online (AJOL)

AISA

1Faculté des Sciences Agronomiques (FSA), Université d'Abomey-Calavi (UAC), 01 BP 526 Cotonou Bénin. Email : cgbemavo@yahoo.fr. 2Institut National des Recherches Agricoles du Bénin, Centre de Recherches Agricoles d'Agonkanmey (CRA-A),. Laboratoire des Sciences du Sol, Eau et Environnement (LSSEE).

The spontaneous breakdown of chiral symmetry in QCD

International Nuclear Information System (INIS)

Yoshida, K.

1980-02-01

It is suggested that the usual path integral representation of Euclidean vacuum amplitude (tunneling amplitude) in QCD must be supplemented by the explicit boundary condition corresponding to the spontaneous breaking of chiral SU(N) x SU(N). Adopting the trial wave function introduced by Nambu and Jona-Lasinio, one sees that such a path integral automatically breaks also the additional chiral U(1) symmetry of massless quarks. The catastrophe of semi-classical approach to QCD and 'U(1) problem' would be avoided in this way and one has, in principle, a better starting point for the self-consistent calculation

Probing QCD in low energy anti pp collisions

International Nuclear Information System (INIS)

Brodsky, S.J.

1986-06-01

A number of exclusive and inclusive antiproton reactions are discussed which could provide useful constraints or test novel features of quantum chromodynamics in the intermediate momentum transfer domain involving both perturbative and non-perturbative dynamics. High momentum transfer reactions are briefly reviewed. Inclusive antiproton reactions and the QCD critical length, QCD predictions for proton-antiproton exclusive processes, and studies of the Compton amplitude in proton-antiproton annihilation are covered. Testing hadron helicity conservation in heavy quark resonance is discussed. Also covered are heavy hadron pair production in proton-antiproton exclusive interactions, exclusive nuclear reactions, and quasi-exclusive nuclear processes

Calculation of hadronic matrix elements using lattice QCD

International Nuclear Information System (INIS)

Gupta, R.

1993-01-01

The author gives a brief introduction to the scope of lattice QCD calculations in his effort to extract the fundamental parameters of the standard model. This goal is illustrated by two examples. First the author discusses the extraction of CKM matrix elements from measurements of form factors for semileptonic decays of heavy-light pseudoscalar mesons such as D → Keν. Second, he presents the status of results for the kaon B parameter relevant to CP violation. He concludes the talk with a short outline of his experiences with optimizing QCD codes on the CM5

Suppressing the QCD axion abundance by hidden monopoles

International Nuclear Information System (INIS)

Kawasaki, Masahiro

2015-11-01

We study the Witten effect of hidden monopoles on the QCD axion dynamics, and show that its abundance as well as isocurvature perturbations can be significantly suppressed if there is a sufficient amount of hidden monopoles. When the hidden monopoles make up a significant fraction of dark matter, the Witten effect suppresses the abundance of axion with the decay constant smaller than 10 12 GeV. The cosmological domain wall problem of the QCD axion can also be avoided, relaxing the upper bound on the decay constant when the Peccei-Quinn symmetry is spontaneously broken after inflation.

Calculation of hadronic matrix elements using lattice QCD

Energy Technology Data Exchange (ETDEWEB)

Gupta, R.

1993-08-01

The author gives a brief introduction to the scope of lattice QCD calculations in his effort to extract the fundamental parameters of the standard model. This goal is illustrated by two examples. First the author discusses the extraction of CKM matrix elements from measurements of form factors for semileptonic decays of heavy-light pseudoscalar mesons such as D {yields} Ke{nu}. Second, he presents the status of results for the kaon B parameter relevant to CP violation. He concludes the talk with a short outline of his experiences with optimizing QCD codes on the CM5.

The Pressure in 2, 2+1 and 3 Flavour QCD

CERN Document Server

Karsch, Frithjof; Peikert, A

2000-01-01

We calculate the pressure in QCD with two and three light quarks on a latticeof size 16^3x4 using tree level improved gauge and fermion actions. We arguethat for temperatures T > 2T_c systematic effects due to the finite latticecut-off and non-vanishing quark masses are below 15 0n this calculation andgive an estimate for the continuum extrapolated pressure in QCD with masslessquarks. We find that the flavour dependence of the pressure is dominated bythat of the Stefan-Boltzmann constant. Furthermore we perform a calculation ofthe pressure using 2 light (m_u,d/T=0.4) and one heavier quark (m_s/T = 1). Inthis case the pressure is reduced relative to that of three flavour QCD. Thiseffect is stronger than expected from the mass dependence of an ideal Fermigas.

Transport at ''NLO'' in hot QCD

CERN Multimedia

CERN. Geneva

2016-01-01

The study of QCD kinetics is driven by a vast array of the experimental measurements of transport at the LHC, ranging from heavy quark energy loss, jet suppression, and hydrodynamics. I first review the fundamental elements of QCD kinetic theory, i.e. plasma screening, 2to2 scattering, and medium modified collinear bremsstrahlung. Then I will summarize recent progress in calculating these elements and their interplay at "NLO" -- "NLO" refers to an order $\\sqrt{\\alpha_s}$ correction to the plasma processes arising from the statistical fluctuations of soft gluons. These "NLO" calculations suggest a computational strategy where the influence of the Debye sector on the real time dynamics of the hard lightlike modes can be incorporated into a few medium coefficients (such as the drag coefficient and $\\hat{q}$), which can be simulated with a Euclidean 3D dimensionally reduced theory.

QCD : the theory of strong interactions Conference MT17

CERN Multimedia

2001-01-01

The theory of strong interactions,Quantum Chromodynamics (QCD), predicts that the strong interaction is transmitted by the exchange of particles called gluons. Unlike the messengers of electromagnetism photons, which are electrically neutral - gluons carry a strong charge associated with the interaction they mediate. QCD predicts that the strength of the interaction between quarks and gluons becomes weaker at higher energies. LEP has measured the evolution of the strong coupling constant up to energies of 200 GeV and has confirmed this prediction.

variabilite des productions et des revenus des exploitations

African Journals Online (AJOL)

3Centre de coopération internationale en recherche agronomique pour le développement (CIRAD), UMR Innovation,. Montpellier, France. Doubangolo COULIBALY, Email kone_b@yahoo.fr. RESUME. La durabilité des systèmes de production à base de coton dans un contexte de variabilité des prix aux producteurs et de ...

Le statut vitaminique des individus et des populations…

Directory of Open Access Journals (Sweden)

Icart Jean-Claude

2000-05-01

Full Text Available Comme le souligne un récent rapport du Haut comité de santé publique, le statut vitaminique des individus et des populations demeure une question d’actualité. Si les études ne révèlent plus de signes évocateurs de carence, au plus des problèmes de déficiences pour certains groupes à risque, des interrogations, demeurent malgré le contexte d’abondance, concernant la couverture des besoins, laquelle pourrait s’avérer inférieure aux valeurs considérées comme satisfaisantes.

Application des TIC à l'atténuation des effets des catastrophes dans ...

International Development Research Centre (IDRC) Digital Library (Canada)

L'Amérique centrale est souvent aux prises avec des inondations et des ... (SIG) et de traitement des images, afin de cartographier les dangers et de modéliser les ... de l'Institut d'étude du développement international de l'Université McGill.

Precision tests of SM and pQCD with jets and photons at LHC

CERN Document Server

Sawyer, Lee; The ATLAS collaboration

2015-01-01

In this talk, I will present several aspects of jet and isolated photon production in pp collisions that have been measured by the ATLAS and CMS collaborations. The measurements of the production cross sections of inclusive jets, di-jet, tri-jet are presented double-differentially as function of jet pT and rapidity for the inclusive measurement and masses and the jet rapidity separation for the di- and tri-jet cases. They probe the dynamics of QCD and can constrain the parton structure of the proton. The cross sections are measured are compared to expectations based on next-to-leading order QCD calculations, as well as to next-to-leading order Monte Carlo simulations. A QCD analysis of these complementary data set is presented. Jet cross sections measurements of di-jet systems with a veto on additional jets, probe QCD radiation effects. The measurements of inclusive prompt photons and di-photons probe the dynamics of QCD and can constrain the parton proton structure. The inclusive prompt photon cross sections...

The time development of QCD jets

International Nuclear Information System (INIS)

Caneschi, L.

1979-01-01

The time development of jets in perturbative QCD is studied. In spite of the fact that the total time for the jet to develop increases indefinitely with increasing energy, quark antiquark pairs remain unscreened only an infinitesimal time. (author)

Gauge/String Duality, Hot QCD and Heavy Ion Collisions

CERN Document Server

Casalderrey-Solana, Jorge; Mateos, David; Rajagopal, Krishna; Wiedemann, Urs Achim

2011-01-01

Over the last decade, both experimental and theoretical advances have brought the need for strong coupling techniques in the analysis of deconfined QCD matter and heavy ion collisions to the forefront. As a consequence, a fruitful interplay has developed between analyses of strongly-coupled non-abelian plasmas via the gauge/string duality (also referred to as the AdS/CFT correspondence) and the phenomenology of heavy ion collisions. We review some of the main insights gained from this interplay to date. To establish a common language, we start with an introduction to heavy ion phenomenology and finite-temperature QCD, and a corresponding introduction to important concepts and techniques in the gauge/string duality. These introductory sections are written for nonspecialists, with the goal of bringing readers ranging from beginning graduate students to experienced practitioners of either QCD or gauge/string duality to the point that they understand enough about both fields that they can then appreciate their in...

Recent soft QCD and jet physics results from ATLAS

CERN Document Server

Boerner, Daniela; The ATLAS collaboration

2017-01-01

The ATLAS collaboration has performed studies of a wide range of QCD phenomena. Recent soft-QCD measurements include studies of track-based measurement of underlying event and particle production properties at sqrt(s)= 13 TeV. Final states with jets and photons provide a unique opportunity for tests of perturbative QCD predictions. In this talk, the latest results on the measurement of the prompt isolated photon production and the inclusive jet and dijet production at a center of mass energy of 8 and 13 TeV are presented. The 8 TeV dataset was also used to measure the photon+jet and diphoton production, differential in a wide range of kinematic variables describing the photon+jet production dynamic. Colour-coherence effects were investigated in events with a photon accompanied by two jets. Furthermore, we will discuss the measurement of multijet production cross sections, where multijet event shape variables have been used to extract the strong coupling constant. The talk concludes with a report on the observ...

QCD processes and search for supersymmetry at the LHC

Energy Technology Data Exchange (ETDEWEB)

Schum, Torben

2012-07-15

In this thesis, a data-driven method to estimate the number of QCD background events in a multijet search for supersymmetry at the LHC was developed. The method makes use of two models which predict the correlation of two key search variables, the missing transverse momentum and an angular variable, in order to extrapolate from a QCD dominated control region to the signal region. A good performance of the method was demonstrated by its application to 36 pb{sup -1} data, taken by the CMS experiment in 2010, and by the comparison with an alternative method. Comparing the number of data events to a combined background expectation of QCD and data-driven estimates of the electroweak and top background, no statistically significant excess was observed for three pre-defined search regions. Limits were calculated for the (m{sub 0},m{sub 1/2}) parameter space of the cMSSM, exceeding previous measurements. The expected sensitivity for further refined search regions was investigated.

QCD processes and search for supersymmetry at the LHC

International Nuclear Information System (INIS)

Schum, Torben

2012-07-01

In this thesis, a data-driven method to estimate the number of QCD background events in a multijet search for supersymmetry at the LHC was developed. The method makes use of two models which predict the correlation of two key search variables, the missing transverse momentum and an angular variable, in order to extrapolate from a QCD dominated control region to the signal region. A good performance of the method was demonstrated by its application to 36 pb -1 data, taken by the CMS experiment in 2010, and by the comparison with an alternative method. Comparing the number of data events to a combined background expectation of QCD and data-driven estimates of the electroweak and top background, no statistically significant excess was observed for three pre-defined search regions. Limits were calculated for the (m 0 ,m 1/2 ) parameter space of the cMSSM, exceeding previous measurements. The expected sensitivity for further refined search regions was investigated.

Chiral symmetry in perturbative QCD

International Nuclear Information System (INIS)

Trueman, T.L.

1979-04-01

The chiral symmetry of quantum chromodynamics with massless quarks is unbroken in perturbation theory. Dimensional regularization is used. The ratio of the vector and axial vector renormalization constante is shown to be independent of the renormalization mass. The general results are explicitly verified to fourth order in g, the QCD coupling constant

Two flavor QCD and Confinement

DEFF Research Database (Denmark)

D'Elia, M.; Di Giacomo, A.; Pica, Claudio

2005-01-01

We argue that the order of the chiral transition for N_f=2 is a sensitive probe of the QCD vacuum, in particular of the mechanism of color confinement. A strategy is developed to investigate the order of the transition by use of finite size scaling analysis. An in-depth numerical investigation is...

QCD and the transverse properties of jets in deep inelastic scattering

International Nuclear Information System (INIS)

Peccei, R.D.; Rueckl, R.

1981-01-01

We study the transverse properties of hadronic jets in deep inelastic scattering, focusing on features which reflect predominantly the underlying QCD structure rather than the process of hadronization. In particular we discuss the QCD induced asymmetries between the transverse size for forward and backward going jets in the virtual boson-nucleon c.m.s. We also analyze the dependence of this transverse spread on the produced hadron energy and indicate how the QCD pattern differs from that expected from hadronization or primordial transverse momentum. We point out, furthermore, the theoretical, and possibly experimental, advantages of studying the average angular spread of the energy flow rather than the transverse momenta of the particle jets. (orig.)

La gestion des résultats des entreprises innovantes

OpenAIRE

Dumas, Guillaume

2014-01-01

Cette thèse s’intéresse à la gestion des résultats dans le cadre des entreprises innovantes. Elle est constituée de trois articles. Dans le premier, il s’agit d’examiner si les résultats des entreprises innovantes sont gérés et si le stade de développement des innovations influence cette gestion des résultats. Il apparaît que les résultats des entreprises innovantes sont gérés à la hausse. Cette gestion ne semble intervenir qu’au cours de l’activité d’innovation (c’est-à-dire lorsque les entr...

Etude des erreurs d'estimation des populations par la méthode des captures successives (DeLURY, 2 captures et des captures-recaptures (PETERSEN

Directory of Open Access Journals (Sweden)

LAURENT M.

1978-01-01

Full Text Available L'estimation des populations naturelles par capture-recapture et par captures successives est souvent entachée d'erreur car, dans de nombreux cas, l'hypothèse fondamentale d'égalité des probabilités de captures pour tous les individus dans le temps et dans l'espace n'est pas respectée. Dans le cas des populations de poissons envisagés ici, les captures ont lieu par la pêche électrique. On a pu chiffrer l'ordre de grandeur des erreurs systématiques faites sur l'estimation des peuplements, en fonction des conditions particulières, biotiques et abiotiques, des différents milieux inventoriés.

Emergent Dynamics of Five-Colour QCD Due to Dimensional Frustration

OpenAIRE

Walker

2010-01-01

The consequences for five-colour QCD of a novel symmetry-breaking mechanism, published in an earlier paper, are further explored. In addition to the emergence of QED and three-colour QCD, there is also a candidate for the Z0μ. The representation theory of SU (N) is applied to the matter sector and yields the quark and electron charge ratios, and a mechanism for generating fermion particle masses.

Computing for Lattice QCD: new developments from the APE experiment

Energy Technology Data Exchange (ETDEWEB)

Ammendola, R [INFN, Sezione di Roma Tor Vergata, Roma (Italy); Biagioni, A; De Luca, S [INFN, Sezione di Roma, Roma (Italy)

2008-06-15

As the Lattice QCD develops improved techniques to shed light on new physics, it demands increasing computing power. The aim of the current APE (Array Processor Experiment) project is to provide the reference computing platform to the Lattice QCD community for the period 2009-2011. We present the project proposal for a peta flops range super-computing center with high performance and low maintenance costs, to be delivered starting from 2010.

Computing for Lattice QCD: new developments from the APE experiment

International Nuclear Information System (INIS)

Ammendola, R.; Biagioni, A.; De Luca, S.

2008-01-01

As the Lattice QCD develops improved techniques to shed light on new physics, it demands increasing computing power. The aim of the current APE (Array Processor Experiment) project is to provide the reference computing platform to the Lattice QCD community for the period 2009-2011. We present the project proposal for a peta flops range super-computing center with high performance and low maintenance costs, to be delivered starting from 2010.

Introduction to quantum chromodynamics (QCD) and the physics of jets

International Nuclear Information System (INIS)

Billoire, Alain; Napoly, Olivier.

1980-12-01

These lecture notes constitute an introduction to Quantum Chromodynamics (QCD), theory of strong interactions. After an elementary presentation of the essential theoretical tools (Lagrangian, renormalization group) and of their consequences for QCD (asymptotic freedom, scaling invariance), we use these to study jets in e + e - annihilation. We thus deal with the problem of infrared divergences and, finally, with the one of the indirect experimental detection of the gluon [fr

The rational parts of one-loop QCD amplitudes I: The general formalism

International Nuclear Information System (INIS)

Xiao Zhiguang; Yang Gang; Zhu Chuanjie

2006-01-01

A general formalism for computing only the rational parts of one-loop QCD amplitudes is developed. Starting from the Feynman integral representation of the one-loop amplitude, we use tensor reduction and recursive relations to compute the rational parts directly. Explicit formulas for the rational parts are given for all bubble and triangle integrals. Formulas are also given for box integrals up to two-mass-hard boxes which are the needed ingredients to compute up to 6-gluon QCD amplitudes. We use this method to compute explicitly the rational parts of the 5- and 6-gluon QCD amplitudes in two accompanying papers

Beauty and the beast: What lattice QCD can do for B physics

International Nuclear Information System (INIS)

Kronfeld, A.S.

1993-01-01

One of the reasons why b-hadrons are interesting is that their properties (decays, mixing, CP violation) help determine the least well-known elements of the Cabibbo-Kobayashi-Maskawa (CKM) matrix. In each case, however, the standard-model expression for the (differential) decay rate follows the pattern: (experimental measurement) = (known factors)(QCD factor)(CKM factor). To extract the CKM factor from the measurement one must have reliable theoretical calculations in nonperturbative QCD. The only systematic, first-principles approach to nonperturbative QCD is the formulation on the lattice. The most promising calculational method has proven to be large-scale numerical computations

Comparison of moments from the valence structure function with QCD predictions

International Nuclear Information System (INIS)

Groot, J.G.H. de; Hansl, T.; Holder, M.; Knobloch, J.; May, J.; Paar, H.P.; Palazzi, P.; Para, A.; Ranjard, F.; Schlatter, D.; Steinberger, J.; Suter, H.; Rueden, W. von; Wahl, H.; Whitaker, S.; Williams, E.G.H.; Eisele, F.; Kleinknecht, K.; Lierl, H.; Spahn, G.; Willutzki, H.J.; Dorth, W.; Dydak, F.; Geweniger, C.; Hepp, V.; Tittel, K.; Wotschack, J.; Bloch, P.; Devaux, B.; Loucatos, S.; Maillard, J.; Merlo, J.P.; Peyaud, B.; Rander, J.; Savoy-Navarro, A.; Turlay, R.; Navarria, F.L.

1979-01-01

Moments (both ordinary and Nachtmann) of the nucleon valence structure function measured in high Q 2 γFe scattering are presented, supplemented by data from deep inelastic eD scattering. These data seem to agree with QCD predictions for vector gluons. The QCD parameter Λ is found to be of the order 0.5 GeV. (Auth.)

QCD : the theory of strong interactions Exhibition LEPFest 2000

CERN Multimedia

2000-01-01

The theory of strong interactions,Quantum Chromodynamics (QCD),predicts that the strong interac- tion is transmitted by the exchange of particles called glu- ons.Unlike the messengers of electromagnetism -pho- tons,which are electrically neutral -gluons carry a strong charge associated with the interaction they mediate. QCD predicts that the strength of the interaction between quarks and gluons becomes weaker at higher energies.LEP has measured the evolution of the strong coupling constant up to energies of 200 GeV and has confirmed this prediction.

Fourier-positivity constraints on QCD dipole models

Directory of Open Access Journals (Sweden)

Bertrand G. Giraud

2016-09-01

Full Text Available Fourier-positivity (F-positivity, i.e. the mathematical property that a function has a positive Fourier transform, can be used as a constraint on the parametrization of QCD dipole-target cross-sections or Wilson line correlators in transverse position space r. They are Bessel transforms of positive transverse momentum dependent gluon distributions. Using mathematical F-positivity constraints on the limit r→0 behavior of the dipole amplitudes, we identify the common origin of the violation of F-positivity for various, however phenomenologically convenient, dipole models. It is due to the behavior r2+ϵ, ϵ>0 softer, even slightly, than color transparency. F-positivity seems thus to conflict with the present dipole formalism when it includes a QCD running coupling constant α(r.

Prompt atmospheric neutrino fluxes: perturbative QCD models and nuclear effects

Energy Technology Data Exchange (ETDEWEB)

Bhattacharya, Atri [Department of Physics, University of Arizona,1118 E. 4th St. Tucson, AZ 85704 (United States); Space sciences, Technologies and Astrophysics Research (STAR) Institute,Université de Liège,Bât. B5a, 4000 Liège (Belgium); Enberg, Rikard [Department of Physics and Astronomy, Uppsala University,Box 516, SE-75120 Uppsala (Sweden); Jeong, Yu Seon [Department of Physics and IPAP, Yonsei University,50 Yonsei-ro Seodaemun-gu, Seoul 03722 (Korea, Republic of); National Institute of Supercomputing and Networking, KISTI,245 Daehak-ro, Yuseong-gu, Daejeon 34141 (Korea, Republic of); Kim, C.S. [Department of Physics and IPAP, Yonsei University,50 Yonsei-ro Seodaemun-gu, Seoul 03722 (Korea, Republic of); Reno, Mary Hall [Department of Physics and Astronomy, University of Iowa,Iowa City, Iowa 52242 (United States); Sarcevic, Ina [Department of Physics, University of Arizona,1118 E. 4th St. Tucson, AZ 85704 (United States); Department of Astronomy, University of Arizona,933 N. Cherry Ave., Tucson, AZ 85721 (United States); Stasto, Anna [Department of Physics, 104 Davey Lab, The Pennsylvania State University,University Park, PA 16802 (United States)

2016-11-28

We evaluate the prompt atmospheric neutrino flux at high energies using three different frameworks for calculating the heavy quark production cross section in QCD: NLO perturbative QCD, k{sub T} factorization including low-x resummation, and the dipole model including parton saturation. We use QCD parameters, the value for the charm quark mass and the range for the factorization and renormalization scales that provide the best description of the total charm cross section measured at fixed target experiments, at RHIC and at LHC. Using these parameters we calculate differential cross sections for charm and bottom production and compare with the latest data on forward charm meson production from LHCb at 7 TeV and at 13 TeV, finding good agreement with the data. In addition, we investigate the role of nuclear shadowing by including nuclear parton distribution functions (PDF) for the target air nucleus using two different nuclear PDF schemes. Depending on the scheme used, we find the reduction of the flux due to nuclear effects varies from 10% to 50% at the highest energies. Finally, we compare our results with the IceCube limit on the prompt neutrino flux, which is already providing valuable information about some of the QCD models.

QCD in the {delta}-regime

Energy Technology Data Exchange (ETDEWEB)

Bietenholz, W. [Universidad Nacional Autonoma de Mexico, Mexico City (Mexico). Inst. de Ciencias Nucleares; Cundy, N. [Seoul National Univ. (Korea, Republic of). Lattice Gauge Theory Research Center; Goeckeler, M. [Regensburg Univ. (Germany). Inst. fuer Theoretische Physik; Horsley, R.; Zanotti, J.M. [Edinburgh Univ. (United Kingdom). School of Physics; Nakamura, Y. [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. [Regensburg Univ. (Germany). Inst. fuer Theoretische Physik; Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)

2011-03-15

The {delta}-regime of QCD is characterised by light quarks in a small spatial box, but a large extent in (Euclidean) time. In this setting a specific variant of chiral perturbation theory - the {delta}-expansion - applies, based on a quantum mechanical treatment of the quasi onedimensional system. In particular, for vanishing quark masses one obtains a residual pion mass M{sup R}{sub {pi}}, which has been computed to the third order in the {delta}-expansion. A comparison with numerical measurements of this residual mass allows for a new determination of some Low Energy Constants, which appear in the chiral Lagrangian. We first review the attempts to simulate 2-flavour QCD directly in the {delta}-regime. This is very tedious, but results compatible with the predictions for M{sup R}{sub {pi}} have been obtained. Then we show that an extrapolation of pion masses measured in a larger volume towards the {delta}-regime leads to good agreement with the theoretical predictions. From those results, we also extract a value for the (controversial) sub-leading Low Energy Constant anti l{sub 3}. (orig.)

Towards the QCD phase diagram

CERN Document Server

De Forcrand, Philippe; Forcrand, Philippe de; Philipsen, Owe

2006-01-01

We summarize our recent results on the phase diagram of QCD with N_f=2+1 quark flavors, as a function of temperature T and quark chemical potential \\mu. Using staggered fermions, lattices with temporal extent N_t=4, and the exact RHMC algorithm, we first determine the critical line in the quark mass plane (m_{u,d},m_s) where the finite temperature transition at \\mu=0 is second order. We confirm that the physical point lies on the crossover side of this line. Our data are consistent with a tricritical point at (m_{u,d},m_s) = (0,\\sim 500) MeV. Then, using an imaginary chemical potential, we determine in which direction this second-order line moves as the chemical potential is turned on. Contrary to standard expectations, we find that the region of first-order transitions shrinks in the presence of a chemical potential, which is inconsistent with the presence of a QCD critical point at small chemical potential. The emphasis is put on clarifying the translation of our results from lattice to physical units, and ...

QCD in the δ-regime

International Nuclear Information System (INIS)

Bietenholz, W.; Rakow, P.E.L.

2011-03-01

The δ-regime of QCD is characterised by light quarks in a small spatial box, but a large extent in (Euclidean) time. In this setting a specific variant of chiral perturbation theory - the δ-expansion - applies, based on a quantum mechanical treatment of the quasi onedimensional system. In particular, for vanishing quark masses one obtains a residual pion mass M R π , which has been computed to the third order in the δ-expansion. A comparison with numerical measurements of this residual mass allows for a new determination of some Low Energy Constants, which appear in the chiral Lagrangian. We first review the attempts to simulate 2-flavour QCD directly in the δ-regime. This is very tedious, but results compatible with the predictions for M R π have been obtained. Then we show that an extrapolation of pion masses measured in a larger volume towards the δ-regime leads to good agreement with the theoretical predictions. From those results, we also extract a value for the (controversial) sub-leading Low Energy Constant anti l 3 . (orig.)

Injectabilite des coulis de ciment dans des milieux fissures

Science.gov (United States)

Mnif, Thameur

Le travail presente ici est un bilan du travaux de recherche effectues sur l'injectabilite des coulis de ciment dans lu milieux fissures. Un certain nombre de coulis a base de ciment Portland et microfin ont ete selectionnes afin de caracteriser leur capacite a penetrer des milieux fissures. Une partie des essais a ete menee en laboratoire. L'etude rheologique des differents melanges a permis de tester l'influence de l'ajout de superplastifiant et/ou de fumee de silice sur la distribution granulometrique des coulis et par consequent sur leur capacite a injecter des colonnes de sable simulant un milieu fissure donne. La classe granulometrique d'un coulis, sa stabilite et sa fluidite sont apparus comme les trois facteurs principaux pour la reussite d'une injection. Un facteur de finesse a ete defini au cours de cette etude: base sur la classe granulometrique du ciment et sa stabilite, il peut entrer dans la formulation theorique du debit d'injection avant application sur chantier. La deuxieme et derniere partie de l'etude presente les resultats de deux projets de recherche sur l'injection realises sur chantier. L'injection de dalles de beton fissurees a permis le suivi de l'evolution des pressions avec la distance au point d'injection. L'injection de murs de maconnerie a caractere historique a montre l'importance de la definition de criteres de performance des coulis a utiliser pour traiter un milieu donne et pour un objectif donne. Plusieurs melanges peuvent ainsi etre predefinis et mis a disposition sur le chantier. La complementarite des ciments traditionnels et des ciments microfins devient alors un atout important. Le choix d'utilisation de ces melanges est fonction du terrain rencontre. En conclusion, cette recherche etablit une methodologie pour la selection des coulis a base de ciment et des pressions d'injection en fonction de l'ouverture des fissures ou joints de construction.

Lattice-QCD based Schwinger-Dyson approach for Chiral phase transition

International Nuclear Information System (INIS)

Iida, Hideaki; Oka, Makoto; Suganuma, Hideo

2005-01-01

Dynamical chiral-symmetry breaking in QCD is studied with the Schwinger-Dyson (SD) formalism based on lattice QCD data, i.e., LQCD-based SD formalism. We extract the SD kernel function K(p 2 ) in an Ansatzindependent manner from the lattice data of the quark propagator in the Landau gauge. As remarkable features, we find infrared vanishing and intermediate enhancement of the SD kernel function K(p 2 ). We apply the LQCD-based SD equation to thermal QCD with the quark chemical potential μ q . We find chiral symmetry restoration at T c ∼100MeV for μ q =0. The real part of the quark mass function decreases as T and μ q . At finite density, there appears the imaginary part of the quark mass function, which would lead to the width broadening of hadrons

Testing the standard model of particle physics using lattice QCD

International Nuclear Information System (INIS)

Water, Ruth S van de

2007-01-01

Recent advances in both computers and algorithms now allow realistic calculations of Quantum Chromodynamics (QCD) interactions using the numerical technique of lattice QCD. The methods used in so-called '2+1 flavor' lattice calculations have been verified both by post-dictions of quantities that were already experimentally well-known and by predictions that occurred before the relevant experimental determinations were sufficiently precise. This suggests that the sources of systematic error in lattice calculations are under control, and that lattice QCD can now be reliably used to calculate those weak matrix elements that cannot be measured experimentally but are necessary to interpret the results of many high-energy physics experiments. These same calculations also allow stringent tests of the Standard Model of particle physics, and may therefore lead to the discovery of new physics in the future

Pentaquarks in QCD Sum Rule Approach

International Nuclear Information System (INIS)

Rodrigues da Silva, R.; Matheus, R.D.; Navarra, F.S.; Nielsen, M.

2004-01-01

We estimate the mass of recently observed pentaquak staes Ξ- (1862) and Θ+(1540) using two kinds of interpolating fields, containing two highly correlated diquarks, in the QCD sum rule approach. We obtained good agreement with the experimental value, using standard continuum threshold

On-Shell Methods in Perturbative QCD

International Nuclear Information System (INIS)

Bern, Zvi; Dixon, Lance J.; Kosower, David A.

2007-01-01

We review on-shell methods for computing multi-parton scattering amplitudes in perturbative QCD, utilizing their unitarity and factorization properties. We focus on aspects which are useful for the construction of one-loop amplitudes needed for phenomenological studies at the Large Hadron Collider

La gouvernance des risques naturels et la problematique des ...

African Journals Online (AJOL)

Depuis quelques années, la gouvernance des risques naturels dus aux inondations remet en cause les processus de mise en oeuvre des politiques urbaines et la qualité de la structure des aménagements dans les grandes villes du Golfe de Guinée. La perception de la gouvernance et l'application des politiques de ...

Hidden QCD in Chiral Gauge Theories

DEFF Research Database (Denmark)

Ryttov, Thomas; Sannino, Francesco

2005-01-01

The 't Hooft and Corrigan-Ramond limits of massless one-flavor QCD consider the two Weyl fermions to be respectively in the fundamental representation or the two index antisymmetric representation of the gauge group. We introduce a limit in which one of the two Weyl fermions is in the fundamental...... representation and the other in the two index antisymmetric representation of a generic SU(N) gauge group. This theory is chiral and to avoid gauge anomalies a more complicated chiral theory is needed. This is the generalized Georgi-Glashow model with one vector like fermion. We show that there is an interesting...... phase in which the considered chiral gauge theory, for any N, Higgses via a bilinear condensate: The gauge interactions break spontaneously to ordinary massless one-flavor SU(3) QCD. The additional elementary fermionic matter is uncharged under this SU(3) gauge theory. It is also seen that when...

Vacuum structure and QCD sum rules

International Nuclear Information System (INIS)

Shifman, M.A.

1992-01-01

The method of the QCD sum rules was and still is one of the most productive tools in a wide range of problems associated with the hadronic phenomenology. Many heuristic ideas, computational devices, specific formulae which are useful to theorists working not only in hadronic physics, have been accumulated in this method. Some of the results and approaches which have originally been developed in connection with the QCD sum rules can be and are successfully applied in related fields, as supersymmetric gauge theories, nontraditional schemes of quarks and leptons, etc. The amount of literature on these and other more basic problems in hadronic physics has grown enormously in recent years. This volume presents a collection of papers which provide an overview of all basic elements of the sum rule approach and priority has been given to the works which seemed most useful from a pedagogical point of view

Vacuum structure and QCD sum rules

International Nuclear Information System (INIS)

Shifman, M.A.

1992-01-01

The method of the QCD sum rules was and still is one of the most productive tools in a wide range of problems associated with the hadronic phenomenology. Many heuristic ideas, computational devices, specific formulae which are useful to theorists working not only in hadronic physics, have been accumulated in this method. Some of the results and approaches which have been originally developed in connection with the QCD sum rules can be and are successfully applied in related fields, such as supersymmetric gauge theories, nontraditional schemes of quarks and leptons, etc. The amount of literature on these and other more basic problems in hadronic physics has grown enormously in recent years. This collection of papers provides an overview of all basic elements of the sum rule approach. Priority has been given to those works which seemed most useful from a pedagogical point of view

Motivations for AdS/QCD from 10D supergravity solutions

International Nuclear Information System (INIS)

De Paula, Wayne

2016-01-01

We discuss some attempts for the construction of gravity duals of QCD-like theories. It is analysed some properties of solutions of 10D Type IIB supergravity theory that attempt to be dual to N= 1 gauge theories, in particular the solutions that belong to Papadoulos-Tseytlin ansatz. We argue that one could obtain 5D effective theories from 10d solutions and it motivates the use of phenomenological AdS/QCD models. (paper)

ARIADNE 3. A Monte Carlo for QCD cascades in the colour dipole formulation

International Nuclear Information System (INIS)

Loennblad, Leif.

1989-06-01

A Monte Carlo program for generating QCD cascades, based on the colour dipole approximation is presented. The program is an extension of the program ARIADNE 2, including gluon splitting in the colour dipole formulation of QCD. (author)

Towards the petaflop for Lattice QCD simulations the PetaQCD project

International Nuclear Information System (INIS)

D'Auriac, Jean-Christian Angles; Carbonell, Jaume; Barthou, Denis

2010-01-01

The study and design of a very ambitious petaflop cluster exclusively dedicated to Lattice QCD simulations started in early '08 among a consortium of 7 laboratories (IN2P3, CNRS, INRIA, CEA) and 2 SMEs. This consortium received a grant from the French ANR agency in July '08, and the PetaQCD project kickoff took place in January '09. Building upon several years of fruitful collaborative studies in this area, the aim of this project is to demonstrate that the simulation of a 256 x 128 3 lattice can be achieved through the HMC/ETMC software, using a machine with efficient speed/cost/reliability/power consumption ratios. It is expected that this machine can be built out of a rather limited number of processors (e.g. between 1000 and 4000), although capable of a sustained petaflop CPU performance. The proof-of-concept should be a mock-up cluster built as much as possible with off-the-shelf components, and 2 particularly attractive axis will be mainly investigated, in addition to fast all-purpose multi-core processors: the use of the new brand of IBM-Cell processors (with on-chip accelerators) and the very recent Nvidia GP-GPUs (off-chip co-processors). This cluster will obviously be massively parallel, and heterogeneous. Communication issues between processors, implied by the Physics of the simulation and the lattice partitioning, will certainly be a major key to the project.

Very rare, exclusive, hadronic decays in QCD factorization

International Nuclear Information System (INIS)

König, Matthias

2016-01-01

We study exclusive hadronic decays of the electroweak bosons Z, W and h in the framework of QCD factorization. We show that the theory uncertainties in these channels are remarkably small compared to past applications of the QCD factorization framework. While the branching ratios are small, many of the modes are accessible at future colliders. The Higgs decays exhibit interesting dependences on the couplings due to the interferences of different diagram topologies, making the h → Vγ decays possible probes of the quark Yukawa couplings and the h → VZ decays probes of the coupling between the Higgs boson, a photon and a Z-boson.

Current issues in perturbative QCD

International Nuclear Information System (INIS)

Hinchliffe, I.

1994-12-01

This review talk discusses some issues of active research in perturbative QCD. The following topics are discussed: (1) current value of αs; (2) heavy quark production in hadron collisions; (3) production of Ψ and Υ in p anti p collisions; (4) prompt photon production; (5) small-x and related phenomena; and (6) particle multiplicity in heavy quark jets

Basics of QCD perturbation theory

International Nuclear Information System (INIS)

Soper, D.E.

1997-01-01

This is an introduction to the use of QCD perturbation theory, emphasizing generic features of the theory that enable one to separate short-time and long-time effects. The author also covers some important classes of applications: electron-positron annihilation to hadrons, deeply inelastic scattering, and hard processes in hadron-hadron collisions. 31 refs., 38 figs

Basics of QCD perturbation theory

Energy Technology Data Exchange (ETDEWEB)

Soper, D.E. [Univ. of Oregon, Eugene, OR (United States). Inst. of Theoretical Science

1997-06-01

This is an introduction to the use of QCD perturbation theory, emphasizing generic features of the theory that enable one to separate short-time and long-time effects. The author also covers some important classes of applications: electron-positron annihilation to hadrons, deeply inelastic scattering, and hard processes in hadron-hadron collisions. 31 refs., 38 figs.

Seven topics in perturbative QCD

International Nuclear Information System (INIS)

Buras, A.J.

1980-09-01

The following topics of perturbative QCD are discussed: (1) deep inelastic scattering; (2) higher order corrections to e + e - annihilation, to photon structure functions and to quarkonia decays; (3) higher order corrections to fragmentation functions and to various semi-inclusive processes; (4) higher twist contributions; (5) exclusive processes; (6) transverse momentum effects; (7) jet and photon physics

Multiplicity distributions in QCD cascades

International Nuclear Information System (INIS)

Gustafson, G.

1992-03-01

Multiplicity distributions for hadrons and for jets are studied in QCD parton cascades. The colour dipole formalism is used and earlier results in the double log approximation are generalized to include terms which are suppressed by colour factors or factors of ln s. The result is a set of coupled differential equations, together with appropriate boundary conditions

Hard QCD at hadron colliders

Energy Technology Data Exchange (ETDEWEB)

Moch, S

2008-02-15

We review the status of QCD at hadron colliders with emphasis on precision predictions and the latest theoretical developments for cross sections calculations to higher orders. We include an overview of our current information on parton distributions and discuss various Standard Model reactions such as W{sup {+-}}/Z-boson, Higgs boson or top quark production. (orig.)

Hard QCD at hadron colliders

International Nuclear Information System (INIS)

Moch, S.

2008-02-01

We review the status of QCD at hadron colliders with emphasis on precision predictions and the latest theoretical developments for cross sections calculations to higher orders. We include an overview of our current information on parton distributions and discuss various Standard Model reactions such as W ± /Z-boson, Higgs boson or top quark production. (orig.)

Equivalence of the AdS-metric and the QCD running coupling

Science.gov (United States)

Pirner, H. J.; Galow, B.

2009-08-01

We use the functional form of the QCD running coupling to modify the conformal metric in AdS/CFT mapping the fifth-dimensional z-coordinate to the energy scale in the four-dimensional QCD. The resulting type-0 string theory in five dimensions is solved with the Nambu-Goto action giving good agreement with the Coulombic and confinement QQbar potential.

Precise tests of QCD in e{sup +}e{sup {minus}} annihilation

Energy Technology Data Exchange (ETDEWEB)

Burrows, P.N.

1997-03-01

A pedagogical review is given of precise tests of QCD in electron-positron annihilation. Emphasis is placed on measurements that have served to establish QCD as the correct theory of strong interactions, as well as measurements of the coupling parameter {alpha}{sub s}. An outlook is given for future important tests at a high-energy e{sup +}e{sup {minus}} collider.

Colour decompositions of multi-quark one-loop QCD amplitudes

DEFF Research Database (Denmark)

Ita, Harald; Ozeren, Kemal

2012-01-01

We describe the decomposition of one-loop QCD amplitudes in terms of colour-ordered building blocks. We give new expressions for the coefficients of QCD colour structures in terms of ordered objects called primitive amplitudes, for processes with up to seven partons. These results are needed in c...... to the cross section for W+4-jet production at the Large Hadron Collider, and verify that it is very well approximated by keeping only the leading terms in an expansion around the formal limit of a large number of colours....

QCD phenomenology of the large P/sub T/ processes

International Nuclear Information System (INIS)

Stroynowski, R.

1979-11-01

Quantum Chromodynamics (QCD) provides a framework for the possible high-accuracy calculations of the large-p/sub T/ processes. The description of the large-transverse-momentum phenomena is introduced in terms of the parton model, and the modifications expected from QCD are described by using as an example single-particle distributions. The present status of available data (π, K, p, p-bar, eta, particle ratios, beam ratios, direct photons, nuclear target dependence), the evidence for jets, and the future prospects are reviewed. 80 references, 33 figures, 3 tables

Stable monopole-antimonopole string background in SU(2) QCD

International Nuclear Information System (INIS)

Cho, Y.M.; Pak, D.G.

2006-01-01

Motivated by the instability of the Savvidy-Nielsen-Olesen (SNO) vacuum we make a systematic search for a stable magnetic background in pure SU(2) QCD. It is shown that a pair of axially symmetric monopole and antimonopole strings is stable, provided that the distance between the two strings is less than a critical value. The existence of a stable monopole-antimonopole string background strongly supports that a magnetic condensation of monopole-antimonopole pairs can generate a dynamical symmetry breaking, and thus the magnetic confinement of color in QCD

QCD Green's Functions and Phases of Strongly-Interacting Matter

Directory of Open Access Journals (Sweden)

Schaefer B.J.

2011-04-01

Full Text Available After presenting a brief summary of functional approaches to QCD at vanishing temperatures and densities the application of QCD Green's functions at non-vanishing temperature and vanishing density is discussed. It is pointed out in which way the infrared behavior of the gluon propagator reflects the (de-confinement transition. Numerical results for the quark propagator are given thereby verifying the relation between (de--confinement and dynamical chiral symmetry breaking (restoration. Last but not least some results of Dyson-Schwinger equations for the color-superconducting phase at large densities are shown.

QCD-suppression by black hole production at the LHC

International Nuclear Information System (INIS)

Loennblad, Leif; Sjoedahl, Malin; Akesson, Torsten

2005-01-01

Possible consequences of the production of small black holes at the LHC for different scenarios with large extra dimensions are investigated. The effects from black hole production on some standard jet observables are examined, concentrating on the reduction of the QCD cross section. It is found that black hole production of partons interacting on a short enough distance indeed seem to generate a drastic drop in the QCD cross section. However from an experimental point of view this will in most cases be camouflaged by energetic radiation from the black holes

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

Quark content of the nucleon in QCD: Perturbative and nonperturbative aspects

International Nuclear Information System (INIS)

Stefanis, N.G.

1989-01-01

We elaborate on two proposed model distribution amplitudes for the nucleon, based on perturbative light-cone QCD supplemented by QCD sum rules. The novel nonperturbative features of these amplitudes are discussed in detail. Reasonable predictions for the Dirac form factor of the proton and the neutron are obtained, paying particular attention to the treatment of the effective coupling constant α s (Q 2 ) and the scale parameter Λ QCD . In addition, the stability properties of the sum rules for the moments of these model distribution amplitudes are analyzed. The range of values of the parameters entering the sum rules is estimated. Relying on expectation values of longitudinal-momentum fractions instead of moments, a heuristic interpretation of the physical content of the model distribution amplitudes is attempted

QCD factorizations in γ*γ*->ρL0ρL0

International Nuclear Information System (INIS)

Pire, B.; Segond, M.; Szymanowski, L.; Wallon, S.

2006-01-01

We calculate the lowest order QCD amplitude, i.e. the quark exchange contribution, to the forward production amplitude of a pair of longitudinally polarized ρ mesons in the scattering of two virtual photons γ*(Q 1 )γ*(Q 2 )->ρ L 0 ρ L 0 . We show that the scattering amplitude simultaneously factorizes in two quite different ways: the part with transverse photons is described by the QCD factorization formula involving the generalized distribution amplitude of two final ρ mesons, whereas the part with longitudinally polarized photons takes the QCD factorized form with the γ L *->ρ L 0 transition distribution amplitude. Perturbative expressions for these, in general, non-perturbative functions are obtained in terms of the ρ-meson distribution amplitude

Dual QCD thermodynamics and quark–gluon plasma

International Nuclear Information System (INIS)

Chandola, H.C.; Punetha, Garima; Dehnen, H.

2016-01-01

Using grand canonical ensemble formulation of a multi-particle statistical system, the thermodynamical description of dual QCD based on magnetic symmetry has been presented and analyzed for the quark–gluon plasma phase of hadronic matter. The dual QCD based bag construction has been shown to lead to the radial pressure on bag surface in terms of the vector glueball masses of magnetically condensed QCD vacuum. Constructing the grand canonical partition function, the energy density and plasma pressure have been derived and used to compute the critical temperatures for QGP–hadron phase transition along with its dynamics. A comparison of the values of critical temperatures for QGP–hadron phase transition with those obtained for the deconfinement-phase transition, has been shown to lead to either the relaxation of the system via a mixed phase of QGP and hot hadron gas or go through a crossover. The associated profiles of the normalized energy density and specific heat have been shown to lead to a large latent heat generation and indicate the onset of a first-order QGP phase transition which turns into a rapid crossover for the case of temperature dependent bag parameter. The squared speed of sound has been shown to act as a physical measure of large thermodynamical fluctuations near transition point. The possible implications of trace anomaly and conformal measure on QGP formation have also been discussed.

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