The present status of experimental measurements of the nucleon structure functions is reviewed. The results from nearly all deep inelastic experiments are in good mutual agreement. Principles of the analysis of these structure function data in the framework of QCD are described. The specific features of the perturbative QCD predictions are observed in the data. This provides quantitative tests of the validity of QCD as well as determinations of the various parton distributions in the nucleon and some of the most precise measurements of the strong coupling constant αs. The future of this field of experimental physics is sketched
Statistical Model for the Nucleon Structure Functions
Bhalerao, R. S.
1996-01-01
A phenomenological model for the nucleon structure functions is presented. Visualising the nucleon as a cavity filled with parton gas in equilibrium and parametrizing the effects due to the finiteness of the nucleon volume, we obtain a good fit to the data on the structure function $F_2^p$. The model then successfully predicts other unpolarized structure function data.
Nucleon Structure Functions from a Chiral Soliton
Weigel, H.(Physics Department, Stellenbosch University, Matieland 7602, South Africa); Gamberg, L.(Department of Physics, Penn State University-Berks, Reading, PA, 19610, U.S.A.); Reinhardt, H.
1996-01-01
Nucleon structure functions are studied within the chiral soliton approach to the bosonized Nambu-Jona-Lasinio model. The valence quark approximation is employed which is justified for moderate constituent quark masses ($\\sim$ 400 MeV) as the contribution of the valence quark level dominates the predictions of nucleon properties. As examples the unpolarized structure functions for the ${\
Nucleon structure functions from a chiral soliton
We study nucleon structure functions within the bosonized version of the Nambu-Jona-Lasinio (NJL) model in which the nucleon emerges as the soliton in the chiral field. Upon boosting to the infinite momentum frame and performing the q2-evolution in the context of the Gottfried sum rule for electron nucleon scattering we determine the intrinsic scale ?2 of the NJL chiral soliton. We also compute the leading twist contributions of the polarized structure functions g1 and g2. We compare these model predictions with experiment by evolving them from ?2 to the scale where the data are taken. Analogously we analyze the chiral-odd structure functions hT and hL. Finally we generalize the treatment to flavor SU(3)
Nucleon structure functions and light front dynamics
Traini, Marco; Faccioli, Pietro; Vento Torres, Vicente
1999-01-01
We present a quark-parton model to describe polarized and unpolarized nucleon structure functions. The twist-two matrix elements for the QCD evolution analysis of lepton-hadron scattering are calculated within a light-front covariant quark model. The relativistic effects in the three-body wave function are discussed for both the polarized and unpolarized cases. Predictions are given for the polarized gluon distributions as will be seen in future experiments.
Phenomenological study of the nucleon structure functions
This thesis is devoted to the study of the deep inelastic scattering. Its purpose is the development of phenomenological models describing experimental results on unpolarized (F2) and polarized (g1) nucleon structure functions in the wide range of the kinematical domain. Special attention is paid to the small-x behaviour of F2 and to the link between deep inelastic scattering and photoproduction process. The investigation of the Pomeron in deep inelastic scattering shows that one single Pomeron compatible with the Froissard-Martin limit can account for all the present HERA data. A phenomenological model of the proton structure function is developed, based on a two-component structure including various features expected from both perturbative quantum chromodynamics and non perturbative Regge theory. A link with the photoproduction process is provided. A detailed analysis of the perturbative components, based on the Gribov-Lipatov-Altarelli-Parisi evolution equations is presented. Taking into account the different parton distribution, this approach allows to describe data on proton and neutron structure functions, on deep inelastic neutrino scattering, and to reproduce the gluons distribution extracted by the ZEUS collaboration. The model is applied to the polarized deep inelastic scattering and the axial anomaly effect appearing both in the description of results on the spin dependent structure functions gp,n,d and in the interpretation of the nucleon spin structure is discussed. (J.S.). 260 refs., 34 figs., 8 tabs., 6 appends
Nucleon Structure Functions from a Chiral Soliton
Weigel, Herbert
1998-10-01
In an attempt to merge the parton model description of deep inelastic scattering with the phenomenologically successful picture of baryons as chiral solitons we study nucleon structure functions in the Nambu--Jona--Lasinio (NJL) chiral soliton model(R. Alkofer, H. Reinhardt and H. Weigel, Phys. Rep. 265) (1996) 139.. We compute the unpolarized structure function for electron--nucleon scattering which enters the Gottfried sum rule, S_G. The model calculation not only explains the observed deviation from the historical value S_G=1/3 but also reproduces the gross features of the exerimental data when accounting for projection and Q^2--evolution(H. Weigel, L. Gamberg and H. Reinhardt, Mod. Phys. Lett. A11) (1996) 3021; Phys. Lett. B399 (1997) 287.. The latter operation further serves to determine the low--momentum scale, Q_0^2, of the model. Subsequently we turn to the polarized structure functions g_1(x,Q^2) and g_2(x,Q^2)(H. Weigel, L. Gamberg and H. Reinhardt, Phys. Rev. D55) (1997) 6910.. These are particularly interesting in the present model because chiral soliton models nicely account for the smallness of the first moment of g_1(x,Q^2). In addition we report on the calculation(L. Gamberg, H. Reinhardt and H. Weigel, Phys. Rev. D58) (1998) 054014. of the chiral odd quark distributions and the corresponding structure functions h_T(x,Q^2) and h_L(x,Q^2). At the low model scale, Q_0^2, we find that the leading twist effective quark distributions, f_1^(q)(x,Q_0^2), g_1^(q)(x,Q_0^2) and h_T^(q)(x,Q_0^2) satisfy Soffer's inequality for both quark flavors q=u,d. The Q^2 evolution of the twist--2 contributions is performed according to the standard GLAP formalism while the twist--three pieces, \\overlineg_2(x) and \\overlineh_L(x), are evolved according to the large NC scheme. Finally we explain the generalization of chiral soliton models to three flavors and discuss the strange quark contribution to g1 as an example(box[t]15cm)O. Schrder, H. Reinhardt and H. Weigel, ``Strangeness Contribution to the Polarized Nucleon Structure Function g_1'', hep--ph/9805251, Phys. Lett. B to appear..
Nucleon Structure Functions within a Chiral Soliton Model
Gamberg, L.(Department of Physics, Penn State University-Berks, Reading, PA, 19610, U.S.A.); Reinhardt, H.; Weigel, H.(Physics Department, Stellenbosch University, Matieland 7602, South Africa)
1997-01-01
We study nucleon structure functions within the bosonized Nambu--Jona--Lasinio model where the nucleon emerges as a chiral soliton. We discuss the model predictions on the Gottfried sum rule for electron--nucleon scattering. A comparison with a low--scale parametrization shows that the model reproduces the gross features of the empirical structure functions. We also compute the leading twist contributions of the polarized structure functions $g_{1}(x)$ and $g_{2}(x)$ in this model. We compare...
Nucleon structure functions at small $x$ via holographic Pomeron exchange
Watanabe, Akira
2015-01-01
The analysis on nucleon structure functions at small Bjorken $x$ in the framework of holographic QCD is presented. In the model setup, the complicated nonperturbative interaction between the virtual photon and the target nucleon is described via the Pomeron exchange, which corresponds to the reggeized graviton exchange in the AdS space. We show that our calculations for both $F_2$ and $F_L$ structure functions are in agreement with the experimental data measured at HERA.
A no extensive statistical model for the nucleon structure function
Trevisan, Luis A. [Departamento de Matematica e Estatistica, Universidade Estadual de Ponta Grossa, 84010-790, Ponta Grossa, PR (Brazil); Mirez, Carlos [Instituto de Ciencia, Engenharia e Tecnologia - ICET, Universidade Federal dos Vales do Jequitinhonha e Mucuri - UFVJM, Campus do Mucuri, Rua do Cruzeiro 01, Jardim Sao Paulo, 39803-371, Teofilo Otoni, Minas Gerais (Brazil)
2013-03-25
We studied an application of nonextensive thermodynamics to describe the structure function of nucleon, in a model where the usual Fermi-Dirac and Bose-Einstein energy distribution were replaced by the equivalent functions of the q-statistical. The parameters of the model are given by an effective temperature T, the q parameter (from Tsallis statistics), and two chemical potentials given by the corresponding up (u) and down (d) quark normalization in the nucleon.
A no extensive statistical model for the nucleon structure function
We studied an application of nonextensive thermodynamics to describe the structure function of nucleon, in a model where the usual Fermi-Dirac and Bose-Einstein energy distribution were replaced by the equivalent functions of the q-statistical. The parameters of the model are given by an effective temperature T, the q parameter (from Tsallis statistics), and two chemical potentials given by the corresponding up (u) and down (d) quark normalization in the nucleon.
Photo-production of Nucleon Resonances and Nucleon Spin Structure Function in the Resonance Region
Qing, D; Qing, Di; Schmidt, Ivan
2002-01-01
The photo-production of nucleon resonances is calculated based on a chiral constituent quark model including both relativistic corrections H{rel} and two-body exchange currents, and it is shown that these effects play an important role. We also calculate the first moment of the nucleon spin structure function g1 (x,Q^2) in the resonance region, and obtain a sign-changing point around Q^2 ~ 0.27 {GeV}^2 for the proton.
Polarized nucleon structure functions within a chiral soliton model
We study polarized-spin structure functions of the nucleon within the bosonized Nambu endash Jona-Lasinio model where the nucleon emerges as a chiral soliton. We present the electromagnetic polarized structure functions g1(x) and g2(x) for ep scattering and discuss various sum rules in the valence quark approximation. This approximation is justified because in this model axial properties of the nucleon are dominated by their valence quark contributions. We find that these structure functions are well localized in the interval 0?x?1. We compare the model predictions on the polarized structure functions with data from the E143 experiment by evolving them from the scale characteristic of the NJL model to the scale of the data. Additionally, a comparison is made with parametrized data at a momentum scale commensurate with the model calculation. copyright 1997 The American Physical Society
Nucleon structure functions in a chiral soliton model
The computation of nucleon structure functions within the Nambu-Jona-Lasinio chiral soliton model is outlined. After some technical remarks on the issue of regularization numerical results for the both unpolarized and polarized structure functions are presented. The generalization to flavor SU(3) is sketched
Nucleon structure functions in a chiral soliton model
Weigel, Herbert
2000-05-08
The computation of nucleon structure functions within the Nambu-Jona-Lasinio chiral soliton model is outlined. After some technical remarks on the issue of regularization numerical results for the both unpolarized and polarized structure functions are presented. The generalization to flavor SU(3) is sketched.
Bertini, M.
1995-05-12
This thesis is devoted to the study of the deep inelastic scattering. Its purpose is the development of phenomenological models describing experimental results on unpolarized (F{sub 2}) and polarized (g{sub 1}) nucleon structure functions in the wide range of the kinematical domain. Special attention is paid to the small-x behaviour of F{sub 2} and to the link between deep inelastic scattering and photoproduction process. The investigation of the Pomeron in deep inelastic scattering shows that one single Pomeron compatible with the Froissard-Martin limit can account for all the present HERA data. A phenomenological model of the proton structure function is developed, based on a two-component structure including various features expected from both perturbative quantum chromodynamics and non perturbative Regge theory. A link with the photoproduction process is provided. A detailed analysis of the perturbative components, based on the Gribov-Lipatov-Altarelli-Parisi evolution equations is presented. Taking into account the different parton distribution, this approach allows to describe data on proton and neutron structure functions, on deep inelastic neutrino scattering, and to reproduce the gluons distribution extracted by the ZEUS collaboration. The model is applied to the polarized deep inelastic scattering and the axial anomaly effect appearing both in the description of results on the spin dependent structure functions g{sup p,n,d} and in the interpretation of the nucleon spin structure is discussed. (J.S.). 260 refs., 34 figs., 8 tabs., 6 appends.
Truncated Moment Analysis of Nucleon Structure Functions
A. Psaker; W. Melnitchouk; M. E. Christy; C. E. Keppel
2007-11-16
We employ a novel new approach using "truncated" moments, or integrals of structure functions over restricted regions of x, to study local quark-hadron duality, and the degree to which individual resonance regions are dominated by leading twists. Because truncated moments obey the same Q^2 evolution equations as the leading twist parton distributions, this approach makes possible for the first time a description of resonance region data and the phenomenon of quark-hadron duality directly from QCD.
Determination of nucleon structure functions from neutrino-iron scattering
In the present thesis from inelastic neutrino-iron scattering the nucleon structure functions 2xF1, F2, xF3, anti q are determined. The data acquisition was performed 1983 at CERN in the 400 GeV neutrino broad-band beam with the improved CDHS detector. The statistics could be essentially raised against the last CDHS structure-function measurement. (orig./HSI)
Diquark contributions to the nucleon deep inelastic structure functions
The contributions of diquarks to the nucleon structure functions are discussed in the framework of the parton model and in the most general case of both vector and scalar diquarks inside unpolarized and polarized nucleons. The vector diquark anomalous magnetic moment and the scalar-vector and vector-scalar diquark transitions are also taken into account. The properties of the diquarks and of their form factors, required in order for the resulting scaling violations to be compatible with the observed ones, are discussed. (author)
Measurements of spin structure functions of the nucleon
After a recall of the history of researches on nucleon structure, this research thesis addresses the measurements of spin structure functions of a proton and of a neutron as they have been performed during the NA47 experiment at the CERN. The author first develops the formalism of the deeply inelastic scattering of polarised leptons on polarised nucleons, with a peculiar attention to the definition of structure functions. The various obtained results are re-determined in a more general framework based on the Operator Product Expansion formalism which allows, within the framework of Quantum Chromodynamics, to relate some moments of structure functions to elements of hadron matrices. The author then describes the experimental situation for the measurement of the proton spin structure function at the end of the 1980's, and presents the experimental installation of the NA47 experiment. Reconstruction programs are then addressed, and the author explains how he determines, event by event, the kinematics of the highly inelastic scattering of a muon on a nucleon, and the vertex position within the target. Sources of errors are identified, and the author presents methods aimed at reducing and at assessing the detection efficiency of all detectors, and of their evolutions in time. The author explains how results on asymmetries and structure functions are extracted from counting rates associated with two cells, as well as the method of calculation of various systematic errors associated with these asymmetries and structure functions. He finally presents results obtained for the measurement of the spin structure function for the proton and for the deuton. The Ellis-Jaffe sum rule is then tested, and spin share of the nucleon born by quarks is determined. Results are compared with those of other experiments, and the Bjorken sum rule is also tested
Nucleon structure functions and light-front dynamics
We present a quark-parton model to describe polarized and unpolarized nucleon structure functions. The twist-two matrix elements for the QCD evolution analysis of lepton-hadron scattering are calculated within a light-front covariant quark model. The relativistic effects in the three-body wave function are discussed for both the polarized and unpolarized cases. Predictions are given for the polarized gluon distributions as will be seen in future experiments. Refs. 16 (author)
Spin And Nuclear Effects In Nucleon Structure Function
Full text: The two experimental results on the structure functions of the nucleon obtained by the European muon collaboration (EMC) from the experiments on deep inelastic scattering of muons on nuclear and scattering of polarized muons on polarized nucleons have become a source of great confusion. From these data the surprising and counter- intuitive results have been obtained indicating that quark distribution in nuclear nucleon is much different than in that free nucleon (so-called nuclear EMC effect) and the total projection of the spin of all quarks and antiquarks in the direction of the spin of the polarized nucleon is close to zero (so-called spin crisis). It is shown that the suppression of soft-gluon emission in the evolution of the nonsinglet structure function of a nucleon within a nucleus describes to a certain extent the EMC effect. High order corrections to the photon polarization degree due to radiative emissions at longitudinal polarized deep inelastic lepton-nucleon scattering are calculated in the framework of the structure-function formalism. We consider the changing of polarization degree of the virtual photon due to the initial state radiation of real photons at longitudinal polarized lepton-nucleon scattering. Usually the photon depolarization factor is taken into account only in low order of perturbative theory. To take into account the radiative correction we used the structure function method for the polarization case. The Born cross section at deep-inelastic lepton-nucleon scattering is modified due to additional real and virtual bosons from either the lepton or quark line. The quarkonic corrections are absorbed into quark structure function, like the gluon radiation, whereas corrections from interference between the lepton and quark line proved to be small. The dominant contribution to the virtual corrections is the vertex corrections and the vacuum polarization. In leading logarithmical approximation, the emitted real photon is collinear with initial (final) lepton. The radiative corrections (RC) change the kinematics of the events. We find that the RC changes the structure of depolarization factor and there is big difference between low and high order at small value of energy fraction of the virtual photon. Therefore, it is necessary to use the expression of photon depolarization factor in high order. It has been shown that the associate production of a J/? meson and a photon at polarized proton-proton collisions can serve as a very clean probe of the gluon polarization. It presents the calculations of the differential cross section for the production with a high transverse momentum of J/? (Jpc = 1--) meson accompanied by the hard photon at the CERN in Large Hadron Collider (LHC) proton-proton (pp) collisions at the energy ?s =14 TeV : p+p = J/?+?+X. In low order J/? meson and photon in the final state with high transverse momenta can only be produced via QCD gluon fusion: g+g = J/?+?. The associated production of a J/? meson and a photon at the LHC energy should not be dominated by fragmentation contributions up to transverse momentum pt values of 50 GeV. This should be due to the fact that quark-antiquark (qq- ) initial states are suppressed at the CERN LHC energy. We use the following cuts: pt?40 GeV. The method to extract the gluon structure function can be based on fitting the J/?-? cross section to the predictions. (authors)
In Medium Nucleon Structure Functions, SRC, and the EMC effect
Hen, O; Gilad, S; Wood, S A
2014-01-01
A proposal approved by the Jefferson Lab PAC to study semi-inclusive deep inelastic scattering (DIS) off the deuteron, tagged with high momentum recoiling protons or neutrons emitted at large angle relative to the momentum transfer. This experiment aims at studying the virtuality dependence of the bound nucleon structure function as a possible cause to the EMC effect and the EMC-SRC correlations. The experiment was approved in 2011 for a total run time of 40 days.
Nuclear effects in F_3 structure function of nucleon
Athar, M Sajjad; Vacas, M J Vicente
2007-01-01
We study nuclear effects in the $F^A_3(x)$ structure function in the deep inelastic neutrino reactions on iron by using a relativistic framework to describe the nucleon spectral functions in the nucleus. The results for the ratio $R(x,Q^2)=\\frac{F^A_3(x,Q^2)}{AF^N_3(x, Q^2)}$ and the Gross-Llewellyn Smith(GLS) integral $G(x,Q^2)=\\int_x^1 dx F^A_3(x,Q^2)$ in nuclei are discussed and compared with the recent results available in literature from theoretical and phenomenological analyses of experimental data.
Nuclear effects in F3 structure function of nucleon
We study nuclear effects in the F3A(x) structure function in the deep inelastic neutrino reactions on iron by using a relativistic framework to describe the nucleon spectral functions in the nucleus. The results for the ratio R(x,Q2)=(F3A(x,Q2))/(AF3N(x,Q2)) and the Gross-Llewellyn Smith (GLS) integral G(x,Q2)=∫x1dxF3A(x,Q2) in nuclei are discussed and compared with the recent results available in literature from theoretical and phenomenological analyses of experimental data
A measurement of the ratio of the nucleon structure function in copper and deuterium
Results are presented on the ratios of the nucleon structure function in copper to deuterium from two separate experiments. The data confirm that the nucleon structure function, F2, is different for bound nucleons than for the quasi-free ones in the deuteron. The redistribution in the fraction of the nucleon's momentum carried by quarks is investigated and it is found that the data are compatible with no integral loss of quark momenta due to nuclear effects. (orig.)
Collinear Structure Functions of the Nucleon: Status and Future
While our ultimate goal is a complete three-dimensional picture of the nucleon in terms of its fundamental constituents, there are still important lessons to be learned about its ''one-dimensional'' collinear parton distribution functions (PDFs) like f1(x) and g1(x). There are rigorous proofs for factorization and universality (process independence) which make these PDFs fundamental. They also appear as limits of Generalized Parton Distributions (GPD) and as integrals of transverse momentum-dependent (TMD) parton distribution functions. Experimentally, the unpolarized structure functions F1(x,Q2), F2(x,Q2) have been studied over a huge kinematic range in both variables. Information on the polarized structure functions g1(x,Q2), g2(x,Q2) is somewhat more limited, both in kinematics and in statistical precision. In both cases, much less is known about the neutron than the proton, due to the absence of a free neutron target. Accessing these structure functions at large x (where valence quarks dominate) has been challenging due to the high luminosity and the high resolution required. Finally, much information can be extracted from studying higher twist contributions to these structure functions and the connection between the DIS limit and the region where nucleon resonance excitation dominates. In my talk, I will present an overview of recent experimental results (with special emphasis on the valence region and the transition from quark to hadronic degrees of freedom). I will also give an outlook on the next round of experiments coming online with the energy-upgraded Jefferson Lab electron beam, and future projects like the Electron Ion Collider
Detailed Measurements of Structure Functions from Nucleons and Nuclei
2002-01-01
The experiment will study deep inelastic muon nucleon scattering in a wide range of Q|2~(1-200 (GeV/c)|2) and x~(0.005-0.75). The main aims of the experiment are: \\item a)~~~~Detailed measurements of the nuclear dependence of the structure function F^2|A, of R~=~@s^L/@s^T and of the cross-section for J/@y production. They will provide a basis for the understanding of the EMC effect: the modification of quark and gluon distributions due to the nuclear environment. \\item b)~~~~A simultaneous high luminosity measurement of the structure function F^2 on hydrogen and deuterium. This will provide substantially improved accuracy in the knowledge of the neutron structure function F^2|n, of F^2|p-F^2|n and F^2|n/F^2|p and their Q|2 dependence. Furthermore, the data will allow a determination of the strong coupling constant @a^s(Q|2) with reduced experimental and theoretical uncertainties as well as of the ratio of the down to up quark distributions in the valence region. Due to the large x range covered by the experim...
Measurement of the nucleon structure function using high energy muons
We have measured the inclusive deep inelastic scattering of muons on nucleons in iron using beams of 93 and 215 GeV muons. To perform this measurement, we have built and operated the Multimuon Spectrometer (MMS) in the muon beam at Fermilab. The MMS is a magnetized iron target/spectrometer/calorimeter which provides 5.61 kg/cm2 of target, 9% momentum resolution on scattered muons, and a direct measure of total hadronic energy with resolution sigma/sub nu/ = 1.4√nu(GeV). In the distributed target, the average beam energies at the interaction are 88.0 and 209 GeV. Using the known form of the radiatively-corrected electromagnetic cross section, we extract the structure function F2(x,Q2) with a typical precision of 2% over the range 5 2 2/c2. We compare our measurements to the predictions of lowest order quantum chromodynamics (QCD) and find a best fit value of the QCD scale parameter Λ/sub LO/ = 230 +- 40/sup stat/ +- 80/sup syst/ MeV/c, assuming R = 0 and without applying Fermi motion corrections. Comparing the cross sections at the two beam energies, we measure R = -0.06 +- 0.06/sup stat/ +- 0.11/sup syst/. Our measurements show qualitative agreement with QCD, but quantitative comparison is hampered by phenomenological uncertainties. The experimental situation is quite good, with substantial agreement between our measurements and those of others. 86 references
Bound nucleon structure function in the picture of relativistic constituent quarks
The structure function F2N of nucleons in the deuterium, carbon and iron nuclei is calculated as a function of Q2 in two approaches: taking into account the nucleon swelling in nuclei due to the partial deconfinement of quarks in nuclear medium; in the conventional approach of nuclear physics, taking into account the getting off the mass shell of the bound nucleon and Fermi motion in nucleons. It is shown that the conventional approach of nuclear physics does not explain the EMC effect in the region of small x
Measurement of the nucleon structure function using high energy muons
Meyers, P.D.
1983-12-01
We have measured the inclusive deep inelastic scattering of muons on nucleons in iron using beams of 93 and 215 GeV muons. To perform this measurement, we have built and operated the Multimuon Spectrometer (MMS) in the muon beam at Fermilab. The MMS is a magnetized iron target/spectrometer/calorimeter which provides 5.61 kg/cm/sup 2/ of target, 9% momentum resolution on scattered muons, and a direct measure of total hadronic energy with resolution sigma/sub nu/ = 1.4..sqrt..nu(GeV). In the distributed target, the average beam energies at the interaction are 88.0 and 209 GeV. Using the known form of the radiatively-corrected electromagnetic cross section, we extract the structure function F/sub 2/(x,Q/sup 2/) with a typical precision of 2% over the range 5 < Q/sup 2/ < 200 GeV/sup 2//c/sup 2/. We compare our measurements to the predictions of lowest order quantum chromodynamics (QCD) and find a best fit value of the QCD scale parameter ..lambda../sub LO/ = 230 +- 40/sup stat/ +- 80/sup syst/ MeV/c, assuming R = 0 and without applying Fermi motion corrections. Comparing the cross sections at the two beam energies, we measure R = -0.06 +- 0.06/sup stat/ +- 0.11/sup syst/. Our measurements show qualitative agreement with QCD, but quantitative comparison is hampered by phenomenological uncertainties. The experimental situation is quite good, with substantial agreement between our measurements and those of others. 86 references.
Structure functions of bound nucleons: from the EMC effect to nuclear shadowing
We describe the nuclear structure functions in the whole range of the Bjorken variable x, by combining various effects in a many-step procedure. First, we present a QCD motivated model of nucleons, treated, in the limit of vanishing Q2, as bound states of three relativistic constituent quarks. Gluons and sea quarks are generated radiatively from the input valence quarks. All parton distributions are described in terms of the confinement (or nucleon's) radius. The results for free nucleons are in agreement with the experimental determinations. The structure functions of bound nucleons are calculated by assuming that the main effect of nucleon binding is stretching of nucleons. The larger size of bound nucleons lowers the valence momentum and enhances the radiatively generated glue and sea densities. In the small-x region the competitive mechanism of nuclear shadowing takes place. It also depends on the size of the nucleons. By combining stretching, shadowing and Fermi motion effects (the latter confined to very large x), the structure function ratio is well reproduced. Results are also presented for the A-dependence of the momentum integral of charged partons, the nuclear gluon distribution and the hadron-nuclei cross sections. (orig.)
Nuclear medium effects in structure functions of nucleon at moderate $Q^2$
Haider, H; Athar, M Sajjad; Singh, S K; Simo, I Ruiz
2015-01-01
Recent experiments performed on inclusive electron scattering from nuclear targets have measured the nucleon electromagnetic structure functions $F_1(x,Q^2)$, $F_2(x,Q^2)$ and $F_L(x,Q^2)$ in $^{12}C$, $^{27}Al$, $^{56}Fe$ and $^{64}Cu$ nuclei. The measurements have been done in the energy region of $1 GeV^2 < W^2 < 4 GeV^2$ and $Q^2$ region of $0.5 GeV^2 < Q^2 < 4.5 GeV^2$. We have calculated nuclear medium effects in these structure functions arising due to the Fermi motion, binding energy, nucleon correlations, mesonic contributions from pion and rho mesons and shadowing effects. The calculations are performed in a local density approximation using relativistic nucleon spectral function which include nucleon correlations. The numerical results are compared with the recent experimental data from JLab and also with some earlier experiments.
Preliminary Results on the Experimental Investigation of the Structure Functions of Bound Nucleons
Bodek, Arie [University of Rochester, Rochester, NY
2015-09-01
We present preliminary results on an experimental study of the nuclear modification of the longitudinal (sL) and transverse (sT ) structure functions of nucleons bound in nuclear targets. The origin of these modifications (commonly referred as as the EMC effect) is not fully understood. Our measurements of R= sL=sT for nuclei (RA) and for deuterium (RD) indicate that nuclear modifications of the structure functions of bound nucleons are different for the longitudinal and transverse structure functions, and that contrary to expectation from several theoretical models, RA < RD.
Linear estimates of structure functions from deep inelastic lepton-nucleon scattering data. Part 2
The paper concerns the linear estimation of structure functions from (anti)neutrino-nucleon scattering. The expressions obtained for the structure functions estimate provide correct analysis of their random error and the bias. The bias arises because of the finite number of experimental data and the finite resolution of experiment. 10 refs
Zhu, Wei; Ruan, Jianhong
2015-10-01
This paper contains three parts relating to the nucleon spin structure in a simple picture of the nucleon: (i) The polarized gluon distribution in the proton is dynamically predicted starting from a low scale by using a nonlinear quantum chromodynamics (QCD) evolution equation — the Dokshitzer-Gribov-Lipatov-Altarelli-Paris (DGLAP) equation with the parton recombination corrections, where the nucleon is almost consisted only of valence quarks. We find that the contribution of the gluon polarization to the nucleon spin structure is much larger than the predictions of most other theories. This result suggests that a significant orbital angular momentum of the gluons is required to balance the gluon spin momentum. (ii) The spin structure function g1p of the proton is studied, where the perturbative evolution of parton distributions and nonperturbative vector meson dominance (VMD) model are used. We predict g1p asymptotic behavior at small x from lower Q2 to higher Q2. The results are compatible with the data including the early HERA estimations and COMPASS new results. (iii) The generalized Gerasimov-Drell-Hearn (GDH) sum rule is understood based on the polarized parton distributions of the proton with the higher twist contributions. A simple parameterized formula is proposed to clearly present the contributions of different components in the proton to Γ 1p(Q2). The results suggest a possible extended objects with size 0.2-0.3 fm inside the proton.
The polarized structure function of the nucleons with a non-extensive statistical quark model
We studied an application of nonextensive thermodynamics to describe the polarized structure function of nucleon, in a model where the usual Fermi-Dirac and Bose-Einstein energy distribution, often used in the statistical models, were replaced by the equivalent functions of the q-statistical. The parameters of the model are given by an effective temperature T, the q parameter (from Tsallis statistics), and the chemical potentials given by the corresponding up (u) and down (d) quark normalization in the nucleon and by Δu and Δd of the polarized functions.
The polarized structure function of the nucleons with a non-extensive statistical quark model
Trevisan, Luis A. [Departamento de Matematica e Estatistica, Universidade Estadual de Ponta Grossa, 84010-790, Ponta Grossa, PR (Brazil); Mirez, Carlos [Instituto de Ciencia, Engenharia e Tecnologia - ICET, Universidade Federal dos Vales do Jequitinhonha e Mucuri - UFVJM, Campus do Mucuri, Rua do Cruzeiro 01, Jardim Sao Paulo, 39803-371, Teofilo Otoni, Minas Gerais (Brazil)
2013-05-06
We studied an application of nonextensive thermodynamics to describe the polarized structure function of nucleon, in a model where the usual Fermi-Dirac and Bose-Einstein energy distribution, often used in the statistical models, were replaced by the equivalent functions of the q-statistical. The parameters of the model are given by an effective temperature T, the q parameter (from Tsallis statistics), and the chemical potentials given by the corresponding up (u) and down (d) quark normalization in the nucleon and by {Delta}u and {Delta}d of the polarized functions.
Recent lattice QCD results on nucleon structure
Konstantinos Orginos
2006-06-25
I review recent developments in lattice calculations of nucleon structure. In particular, I cover the calculations of nucleon matrix elements related to generalized parton distribution functions, structure functions and form factors.
Recent lattice QCD results on nucleon structure
Konstantinos Orginos
2006-07-01
I review recent developments in lattice calculations of nucleon structure. In particular, I cover the calculations of nucleon matrix elements related to generalized parton distribution functions, structure functions and form factors.
One-loop factorization of the nucleon g2-structure function in the nonsinglet case
We consider the one-loop factorization of the simplest twist-3 process: inclusive deep-inelastic scattering of longitudinally polarized leptons on a transversely polarized nucleon target. By studying the Compton amplitudes for certain quark and gluon states at one loop, we find the coefficient functions for the nonsinglet twist-3 distributions in the factorization formula of g2(xB,Q2). The result marks the first step towards a next-to-leading order formalism for this transverse-spin-dependent structure function of the nucleon
Structure functions of the nucleon in a statistical model
Cleymans, J; Joubert, J
1993-01-01
Deep inelastic scattering is considered in a statistical model of the nucleon. This incorporates certain features which are absent in the standard parton model such as quantum statistical correlations which play a role in the propagation of particles when considering Feynman diagrams containing internal lines. The inclusion of the ${\\cal O}(\\alpha_{s})$ corrections in our numerical calculations allows a good fit to the data for $x\\geq 0.25$. The fit corresponds to values of temperature and chemical potential of approximately $T=0.067$ GeV and $\\mu=0.133$ GeV. The latter values of parameters, however, give rise, for all $x$, to a large value for $R=\\sigma_{L}/\\sigma_{T}$.
Within the framework of quenched lattice QCD and using O(a) improved Wilson fermions and nonperturbative renormalization, a high statistics computation of low moments of the unpolarized nucleon structure functions is given. Particular attention is paid to the chiral and continuum extrapolations
The ratio of the nucleon structure functions Fsup(N)2 for iron and deuterium
Using the data on deep inelastic muon scattering on iron and deuterium the ratio of the nucleon structure functions F2sup(N)(Fe)/F2sup(N)(D) is presented. The observed x-dependence of this ratio is in disagreement with existing theoretical predictions. (orig.)
Linear estimates of structure functions from deep inelastic lepton-nucleon scattering data. Part 1
This paper concerns the linear estimation of structure functions from muon(electron)-nucleon scattering. The expressions obtained for the structure functions estimate provide correct analysis of the random error and the bias The bias arises because of the finite number of experimental data and the finite resolution of experiment. The approach suggested may become useful for data handling from experiments at HERA. 9 refs
Once more on the radiative corrections to the nucleon structure functions in QCD
A new representation of the next to leading QCD corrections to the nucleon structure functions is given in terms of parton distributions. All O(αs) corrections to the leading logarithmic approximation (LLA) are included. In contrast to the similar representations in the literature terms of order O(α2s) do not attend in our expressions for the nucleon structure functions taken in the next to leading logarithmic approximation. This result is generalized for any order in αs beyond the LLA. Terms of order O(αns) which belong only tot he approximation in consideration are present in such a representation for the structure functions. (author). 11 refs
Nucleon size and nucleon structure
Hidden-color basis states of multiquark systems are expressed in terms of states involving color-singlet hadrons. The size of various nucleon form factors is used to separate the interior perturbative region of quarks from the exterior nonperturbative region of hadrons. The distinction between the baryon interior and its exterior appears to be relevant in baryon spectroscopy and in nuclear forces. 26 refs.; 1 figure
Study of the spin structure functions of the nucleon: the E143 experiment at SLAC
In this thesis, we present the results of the E143 experiment of deep inelastic scattering of 29 GeV polarized electrons from polarized NH3 and ND3 targets, at SLAC. The goal of the experiment is the measurement of the spin structure functions g1 and g2 of the nucleon which provide information on its internal spin structure. Experimentally, the structure functions are extracted from the measurement of cross section asymmetries. Our measured values of the first moment of g1 are two and three standard deviations below the Ellis-Jaffe sum rule predictions, for the proton and for the deuteron, respectively. The Bjoerken sum rule, a QCD fundamental prediction, has been confirmed. We find the quark contribution to the nucleon spin to be around 30 pc. Our results on g2 are well described by the Wandzura-Wilczek expression. (author)
Nucleon structure functions from νmu-Fe scattering at the Tevatron
We present preliminary results for nucleon structure functions measured in high energy neutrino interactions. Included are new results for the Gross-Llewellyn Smith Sum Rule, ∫x/1xF3dx = 2.66 ± .03(stat)±.08(syst), the ratio of cross-sections, σbarν/σν = .511 ± .002(stat) ± .005(syst), and an analysis of the Q2 evolution of xF3. 16 refs., 5 figs
Moments of nuclear and nucleon structure functions at low Q2 and the momentum sum rule
New nuclear structure function data from Jefferson Lab covering the higher x and lower Q2 regime make it possible to extract the higher order F2 moments for iron and deuterium at low four-momentum transfer squared Q2. These moments allow for an experimental investigation of the nuclear momentum sum rule and a direct comparison of the non-singlet nucleon moment with Lattice QCD results
Structure function measurements in the deep inelastic muon-nucleon scattering
Measurements of deep inelastic scattering events on a combined copper and deuterium target were performed by the European Muon Collaboration (EMC) using a muon beam at CERN's SPS with energies at 100 GeV and 280 GeV. The data are analysed and compared with a detailed Monte-Carlo simulation and allow the determination of structure functions from both targets. In the light of the present discrepancy between EMC's and BCDMS's structure functions, stringend cuts were applied to the data. The results confirm the EMC structure function measurements on unbound nucleons. The comparison between the copper structure function from this experiment and the NA2 iron structure function shows a trend to lower values at low xBj. (orig.)
Spin structure functions of the nucleon at low Q2 and ?
Phenomenological approaches to describe the spin structure functions an spin sum rules for proton and neutrons at low momentum transfer Q2 and energy transfer ?, i.e. in the region of the nucleon resonances are discussed. Experiments to measure A1p, A2p and N1n structure functions at CEBAF in a Q2 range from 0.15 to 2.0 GeV2, and a W range from threshold to 2.2 GeV are presented
Spin structure functions of the nucleon at low Q{sup 2} and {nu}
Burkert, V.D.
1993-06-30
Phenomenological approaches to describe the spin structure functions an spin sum rules for proton and neutrons at low momentum transfer Q{sup 2} and energy transfer {nu}, i.e. in the region of the nucleon resonances are discussed. Experiments to measure A{sub 1}{sup p}, A{sub 2}{sup p} and N{sub 1}{sup n} structure functions at CEBAF in a Q{sup 2} range from 0.15 to 2.0 GeV{sup 2}, and a W range from threshold to 2.2 GeV are presented.
On the relation between nuclear and nucleon Structure Functions and their moments
Rinat, A S
2006-01-01
Calculations of nuclear Structure Functions (SF) F_k^A(x,Q^2) routinely exploit a generalized convolution, involving the SF for nucleons F_k^N and the linking SF f^{PN,A} of a fictitious nucleus, composed of point-particles, with the latter usually expressed in terms of hadronic degrees of freedom. For finite Q^2 the approach seemed to be lacking a solid justification and the same is the case for recently proposed, effective nuclear parton distribution functions (pdf), which exactly reproduce the above-mentioned hadronically computed F_k^A. Many years ago Jaffe and West proved the above convolution in the Plane Wave Impulse Approximation (PWIA) for the nuclear components in the convolution. In the present note we extend the above proof to include classes of nuclear Final State Interactions (FSI). One and the same function appears to relate parton distribution functions (pdf) in nuclei and nucleons, and SF for nuclear targets and for nucleons. That relation is the previously conjectured one,with an entirely di...
In this thesis results of measurements of the differential cross sections of the elastic and inelastic electron deuteron scattering are presented. The data were taken at several scattering angles and in the electron energy range of 150 MeV up to 320 MeV. The extracted form factors and structure functions are compared with theoretical results which are sensitive to details of nucleon structure and of the nucleon-nucleon forces. (FKS)
Strangeness content and structure function of the nucleon in a statistical quark model
Trevisan, L A; Tomio, L
1999-01-01
The strangeness content of the nucleon is determined from a statistical model using confined quark levels, and is shown to have a good agreement with the corresponding values extracted from experimental data. The quark levels are generated in a Dirac equation that uses a linear confining potential (scalar plus vector). With the requirement that the result for the Gottfried sum rule violation, given by the new muon collaboration (NMC), is well reproduced, we also obtain the difference between the structure functions of the proton and neutron, and the corresponding sea quark contributions. (27 refs).
Asymptotic solutions of the evolution equation for the polarized nucleon structure function g2(?,Q2)
We show that quark operators of twist 3 contributing to the polarized nucleon structure function g2tw.3(x, Q2) decouple from the evolution equation for the quark-gluon operators of the same twist in two important limits, Nc?? and n?? (Nc is the number of colours and n refers to the n-th moment of g2). The anomalous dimensions for the quark operators turn out to be always the lowest ones in the spectrum. Asymptotic behaviour of g2(x, Q2) in the region 1-xc?? cases are presented. (orig.)
Modelling the nucleon structure
Burkardt, M
2015-01-01
We review the status of our understanding of nucleon structure based on the modelling of different kinds of parton distributions. We use the concept of generalized transverse momentum dependent parton distributions and Wigner distributions, which combine the features of transverse-momentum dependent parton distributions and generalized parton distributions. We revisit various quark models which account for different aspects of these parton distributions. We then identify applications of these distributions to gain a simple interpretation of key properties of the quark and gluon dynamics in the nucleon.
Determination of nucleon structure functions on the assumption of diquark presence
In this thesis, we asked for the presence in the nucleons of either scalar or axial vector diquarks. After the introduction of the basis notions on diquarks and their interest in the understanding of various physical problems, we present in the first chapter the theoretical frame in SU(6) symmetry. Chapter 2 and 3 are respectively devoted to the Stockholm and Torino models. We point out to get a very nice fit of the experimental data with models we had to put in a small Q2 dependence in the various quarks distribution functions previously determined. In chapter 4, we used our distribution functions and compared our predictions with experimental results: the ratio of the neutron electromagnetic structure function to that of the proton, the ratio of the longitudinal component to the transverse one for the lepton-nucleon scattering cross-section, so the dileptons production in Drell-Yan process. The conclusion of that study is that the presence of diquarks does not lead, at the moment, to any obvious contradiction with the experimental data; diquarks as constituents are a viable idea, which in certain kinematical regions could be of crucial importance
Nuclear effects in F{sub 3} structure function of nucleon
Athar, M. Sajjad [Department of Physics, Aligarh Muslim University, Aligarh-202 002 (India)], E-mail: sajathar@rediffmail.com; Singh, S.K. [Department of Physics, Aligarh Muslim University, Aligarh-202 002 (India); Vacas, M.J. Vicente [Departamento de Fisica Teorica and IFIC, Centro Mixto Universidad de Valencia-CSIC, 46100 Burjassot (Valencia) (Spain)
2008-10-02
We study nuclear effects in the F{sub 3}{sup A}(x) structure function in the deep inelastic neutrino reactions on iron by using a relativistic framework to describe the nucleon spectral functions in the nucleus. The results for the ratio R(x,Q{sup 2})=(F{sub 3}{sup A}(x,Q{sup 2}))/(AF{sub 3}{sup N}(x,Q{sup 2})) and the Gross-Llewellyn Smith (GLS) integral G(x,Q{sup 2})={integral}{sub x}{sup 1}dxF{sub 3}{sup A}(x,Q{sup 2}) in nuclei are discussed and compared with the recent results available in literature from theoretical and phenomenological analyses of experimental data.
N Barik; R N Mishra
2001-04-01
Considering the nucleon as consisting entirely of its valence quarks conﬁned independently in a scalar-vector harmonic potential; unpolarized structure functions 1(,2) and 2(x,2) are derived in the Bjorken limit under certain simplifying assumptions; from which valence quark distribution functions (,2) and (,2) are appropriately extracted satisfying the normalization constraints. QCD-evolution of these input distributions from a model scale of 2=0.07 GeV2 to a higher $Q^{2}$ scale of $Q^{2}_{0} = 15$ GeV2 yields (, $Q^{2}_{0}$) and (, $Q^{2}_{0}$) in good agreement with experimental data. The gluon and sea-quark distributions such as (,$Q^{2}_{0}$) and (, $Q^{2}_{0}$) are dynamically generated with a reasonable qualitative agreement with the available data; using the leading order renormalization group equations with appropriate valence-quark distributions as the input.
A detailed study of nucleon structure function in nuclei in the valence quark region
Bianchi, N. [INFN-Laboratori, Nazionali di Frascati (Italy)
1994-04-01
The so called {open_quotes}EMC effect{close_quotes} discovered during the 1980`s, has caused a big controversy in the community of nuclear and high energy physicists; during the last ten years, five experiments have been performed in different laboratories and several hundreds of papers about the possible interpretation of the modification of the nucleon structure function inside nuclei have been published. However, from the experimental point of view, the main goal of four experiments (EMC, BCDMS, NMC, FNAL) has been to emphasize the region of low x{sub b}, where shadowing effects appear. In the region of valence quarks and nuclear effects (x{sub b} > 0.1 - 0.2) the most reliable data presently available are from the SLAC E139 experiment performed in 1983 with only 80 hours of beam time. New precise data in the valence quark region are necessary to measure separate structure functions F{sub 2}(x{sub b}, Q{sup 2}) and R{sup lt}(x{sub b},Q{sup 2}) = {sigma}{sub l}/{sigma}{sub t}, and to investigate the real A-dependence of the ratio between bound and free-nucleon structure functions which is not completely defined by the SLAC data. Moreover, from the nuclear physics point of view, a measurement on some unexplored nuclei, like {sup 3}He and {sup 48}Ca, would be of great interest. The intermediate scaling region (0.1 < x{sub b} < 0.7) would be accessible at CEBAF if the machine energy will reach 6-8 GeV, as suggested by all the tests performed on the RF cavities. This physics program has been already presented in two letter of intents.
The third moment d2 of the twist-3 part of the nucleon spin structure function g2 is generalized to arbitrary momentum transfer Q2 and is evaluated in heavy baryon chiral perturbation theory (HBChPT) up to order Ο(p4) and in a unitary isobar model (MAID). We show how to link d2 as well as higher moments of the nucleon spin structure functions g1 and g2 to nucleon spin polarizabilities. We compare our results with the most recent experimental data, and find a good description of these available data within the unitary isobar model. We proceed to extract the twist-4 matrix element f2 which appears in the 1/Q2 suppressed term in the twist expansion of the spin structure function g1 for proton and neutron
Nucleon structure using lattice QCD
Alexandrou, C.; Kallidonis, C. [Cyprus Univ., Nicosia (Cyprus). Dept. of Physics; The Cyprus Institute, Nicosia (Cyprus). Computational-Based Science and technology Research Center; Constantinou, M.; Hatziyiannakou, K. [Cyprus Univ., Nicosia (Cyprus). Dept. of Physics; Drach, V. [DESY Zeuthen (Germany). John von Neumann-Institut fuer Computing NIC; Jansen, K. [DESY Zeuthen (Germany). John von Neumann-Institut fuer Computing NIC; Cyprus Univ., Nicosia (Cyprus). Dept. of Physics; Koutsou, G.; Vaquero, A. [The Cyprus Institute, Nicosia (Cyprus). Computational-Based Science and technology Research Center; Leontiou, T. [Frederick Univ, Nicosia (Cyprus). General Dept.
2013-03-15
A review of recent nucleon structure calculations within lattice QCD is presented. The nucleon excited states, the axial charge, the isovector momentum fraction and helicity distribution are discussed, assessing the methods applied for their study, including approaches to evaluate the disconnected contributions. Results on the spin carried by the quarks in the nucleon are also presented.
Axial structure of the nucleon
Veronique Bernard; Latifa Elouadrhiri; Ulf-G Meissner
2002-01-01
We review the current status of experimental and theoretical understanding of the axial nucleon structure at low and moderate energies. Topics considered include (quasi)elastic (anti)neutrino-nucleon scattering, charged pion electroproduction off nucleons and ordinary as well as radiative muon capture on the proton.
Axial structure of the nucleon
Bernard, Véronique(Institut de Physique Nucléaire, CNRS/Univ. Paris-Sud 11 (UMR 8608), Orsay Cedex, F-91406, France); Elouadrhiri, Latifa; Meißner, Ulf-G.
2001-01-01
We review the current status of experimental and theoretical understanding of the axial nucleon structure at low and moderate energies. Topics considered include (quasi)elastic (anti)neutrino-nucleon scattering, charged pion electroproduction off nucleons and ordinary as well as radiative muon capture on the proton.
Nucleon structure using lattice QCD
A review of recent nucleon structure calculations within lattice QCD is presented. The nucleon excited states, the axial charge, the isovector momentum fraction and helicity distribution are discussed, assessing the methods applied for their study, including approaches to evaluate the disconnected contributions. Results on the spin carried by the quarks in the nucleon are also presented.
Low x Double ln2(1/x) Resummation Effects at the Sum Rules for Nucleon Structure Function g1
We have estimated the contributions to the moments of polarized nucleon structure function g1(x,Q2) coming from the region of the very low x (10-52(1/x) resummation. The Q2 evolution of g1 was described by the unified evolution equations incorporating both the leading order Altarelli-Parisi evolution at large and moderate x, and the double ln2(1/x) resummation at small x. The moments were obtained by integrating out the extrapolated nucleon structure function in the region 10-5< x<1. (author)
Nucleon structure from lattice QCD
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(a2) discretization effects.
Nucleon structure from lattice QCD
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.
Nematollahi, H.; Yazdanpanah, M. M.
2015-07-01
We investigate the structure of the light nuclei based on the modified chiral quark model (? QM ) , for the first time. To this end, we first calculate the parton distribution functions (PDFs) of the bounded nucleons using the ? QM and then compute those of the light nuclei. For this purpose, it is first needed to obtain the bare quark densities inside the bounded nucleons of the nucleus. These bare distributions are calculated by applying the quark exchange model (QEM) in this article. Finally, we obtain the quark, antiquark, and gluon distributions and also the structure functions (SFs) of the bound state nucleons and the light nuclei at low Q2 scale (Q2=0.35 GeV2) . These distributions can be evolved to the higher scales using DGLAP evolution equations. It is shown that the results of our theoretical framework are in good agreement with the experimental data and they also have appropriate behavior in comparison with the different parametrization models.
Study of the nucleon spin structure functions: the E154 experiment at SLAC
In experiment E154 at SLAC, the spin dependent structure function g1n was measured by scattering longitudinally polarized 50 GeV electrons off a longitudinally polarized helium 3 target. We report the integral over the measured x range to be ?0.0140.7g1n(x,5 GeV2)dx = -0.0348 0.0033 0.0043 0.0014. We observe relatively large values of g1n at low x, calling into question the reliability of the data extrapolation down to x equal 0. Such a divergent behavior seems to disagree with the prediction of the Regge theory but can be quantitatively explained by perturbative QCD. Moreover, we have performed a NLO perturbative QCD analysis of the world data on g1, paying careful attention to both the theoretical hypothesis and the calculation of errors. Using a parametrization of the polarized parton distribution at a low scale, we can access the fraction of spin carried by quarks: ?? = 29 6 pc in the MS-bar scheme, and ?? = 37 7 pc in the AB scheme. The gluon contribution to the nucleon spin is not well enough constrained by the current data, but seems to lie between 0 and 2. This study allows us to extract the first moment of the g1 structure function and we find agreement with the Bjorken sum rule expectations. (author)
Nucleon Spin Structure: Experiment
Miller, Andy
2003-04-01
The experimental study of nucleon spin structure is at a transitional stage. Deeply inelastic scattering of leptons has revealed much about quark helicity distributions, and is approaching the limits of what is possible with present experimental facilities. The latest results from semi-inclusive measurements at HERMES will be presented. Precise new complementary data are expected soon from W production at RHIC-Spin. The gluon polarization will also be measured soon at COMPASS and RHIC. Meanwhile, single-spin asymmetries that promise to provide access to the unknown transversity distribution have been observed, and will be discussed. Based on these signals, the first measurements of transversity are underway. Finally, single spin asymmetries have also been recently observed in hard exclusive processes such as deeply virtual Compton scattering. These signals have the potential to provide a new window on both orbital angular momentum of partons, and on correlations between their longitudinal momentum and transverse position.
The Spin Structure of the Nucleon
Pretz, Jörg
2007-01-01
This article reviews recent results on the spin structure of the nucleon from polarized deep inelastic lepton-nucleon scattering and polarized proton-proton scattering. For a description of the nucleon in terms of parton distribution functions (pdf) the knowledge of three basic distributions is needed: The relatively well known unpolarized pdfs, the helicity distributions and the transversity distributions. The latter two play an essential role in understanding the spin structure of the nucleon. New results on the gluon helicity distribution $\\Delta G(x)$ and the helicity distributions for strange and valence quarks are discussed. A first determination of the up to now unknown transversity distributions $\\Delta_{T}q(x)$ is presented. Finally results from deep virtual Compton scattering, giving access to the orbital angular momentum contribution of quarks to the nucleon spin, are discussed.
In consideration of the lowest order non-perturbative effect due to the quark condensate and gluon condensate on the quark propagator, we calculate QCD non-perturbative quark propagator under the chain approximation. Using the obtained non-perturbative quark propagator, we analyse the non-perturbative effect in the nucleon structure functions and show the non-trivial Q2-dependence in the nucleon structure functions
From nuclear structure to nucleon structure
Similarities between nuclear structure study with many-body theory approach and nucleon structure calculations with lattice QCD are pointed out. We will give an example of how to obtain the connected sea partons from a combination of the experimental data, a global fit of parton distribution functions and a lattice calculation. We also present a complete calculation of the quark and glue decomposition of the proton momentum and angular momentum in the quenched approximation. It is found that the quark orbital angular momentum constitutes about 50% of the proton spin
Higher twist effects in the deeply inelastic scattering are studied. We start with a short review of the theoretical results on higher twists in QCD. Within the saturation model we perform a twist analysis of the nucleon structure functions FT and FL at small value of the Bjorken variable x. The parameters of the model are fitted to the HERA F2 data, and we derive a prediction for the longitudinal structure function FL. We conclude that for FL the higher twist corrections are sizable whereas for F2=FT+FL there is a nearly complete cancellation of twist-4 corrections in FT and FL. We discuss a few consequences for future LHC measurements.
Bartels, Jochen; Motyka, Leszek
2009-01-01
Higher twist effects in the deeply inelastic scattering are studied. We start with a short review of the theoretical results on higher twists in QCD. Within the saturation model we perform a twist analysis of the nucleon structure functions FT and FL at small value of the Bjorken variable x. The parameters of the model are fitted to the HERA F2 data, and we derive a prediction for the longitudinal structure function FL. We conclude that for FL the higher twist corrections are sizable whereas for F2 = FT + FL there is a nearly complete cancellation of twist-4 corrections in FT and FL. We discuss a few consequences for future LHC measurements.
Constituent quark description of nucleon structure
Nucleon structure functions are calculated within the constituent quark in the leading order. The results compare well with the experimental data for entire range of kinematics in x and Q2and with the next - to - leading order calculation of GRV
Axial vector diquark correlations in the nucleon: structure functions and static properties
In order to extract information on the strength of quark-quark correlations in the axial vector (a.v.) diquark channel (JP=1+,T=1), we analyze the quark light cone momentum distributions in the nucleon, in particular their flavor dependencies, and the static properties of the nucleon. To construct the nucleon as a relativistic 3-quark bound state, we use a simple 'static' approximation to the full Faddeev equation in the Nambu-Jona-Lasinio model, including correlations in the scalar (JP=0+,T=0) and a.v. diquark channels. It is shown that the a.v. diquark correlations should be rather weak compared to the scalar ones. From our analysis we extract information on the strength of the correlations as well as on the probability of the a.v. diquark channel
SU(6)-strong breaking: structure functions and small momentum transfer properties of the nucleon
Evidence for SU(6) breaking of the baryonic ground state, the connection between the quark model and the quark--parton model, the nucleon in a pure 56 at rest with relativistic quark motion, and SU(6) mixing (56, L = 0) + (70, L = 0) for the nucleon, without the small components effects, description of the F2/sup en//F2/sup ep/ behavior, and the neutron charge radius are treated. Gluons and the q anti q sea are introduced, and final results given combining the various effects. Finally the distinction between constituent and current quarks is discussed with regards to its relevance. 48 references
The spin and flavor structure of quarks and gluons in nucleons and nuclei is more complicated than expected in the original naive quark model. Recent results which show some of the key failures of the naive picture are summarized here with emphasis on recent results from the HERMES experiment. Some future options to study the quarks structure in exclusive processes in electroproduction, photoproduction and pp annihilation are presented. (orig.)
E.R. Nocera
2015-03-01
Full Text Available I investigate the behavior of spin-dependent parton distribution functions in the regions of small and large momentum fractions x. I present a systematic comparison between predictions for relevant observables obtained with various models of nucleon spin structure and a recent global analysis of spin-dependent distributions, NNPDFpol1.1. Together with its unpolarized counterpart, NNPDF2.3, they form a mutually consistent set of parton distributions. Because they include most of the available experimental information, and are determined with a minimally biased methodology, these are especially suited for such a study. I show how NNPDFpol1.1 can discriminate between different theoretical models, even though NNPDF uncertainties remain large near the endpoints x→0 and x→1, due to the lack of experimental information. I discuss how our knowledge of nucleon spin structure may be improved at small x by future measurements at an Electron–Ion Collider, and at large x by recent measurements at Jefferson Lab, also in view of its 12 GeV upgrade.
Nocera, Emanuele Roberto
2014-01-01
I investigate the behavior of spin-dependent parton distribution functions in the regions of small and large momentum fractions $x$. I present a systematic comparison between predictions for relevant observables obtained with various models of nucleon spin structure and a recent global analysis of spin-dependent distributions, NNPDFpol1.1. Together with its unpolarized counterpart, NNPDF2.3, they form a mutually consistent set of parton distributions. Because they include most of the available experimental information, and are determined with a minimally biased methodology, these are especially suited for such a study. I show how NNPDFpol1.1 can discriminate between different theoretical models, even though NNPDF uncertainties remain large near the endpoints $x\\to 0$ and $x\\to 1$, due to the lack of experimental information. I discuss how our knowledge of nucleon spin structure may be improved at small-$x$ by future measurements at an Electron-Ion Collider, and at large-$x$ by recent measurements at Jefferson...
Measurement of the nucleon g sub 2 spin structure function at SLAC
Rondon, Oscar A
1999-01-01
The deep inelastic polarized structure functions g sup p sup , sup n sub 2 and g sup p sup , sup n sub 1 have been recently measured at the Stanford Linear Accelerator Center (SLAC) End Station A facility by the E155 Collaboration using 48.4 GeV and 38.8 GeV longitudinally polarized electrons incident on longitudinally and transversely polarized ammonia (NH sub 3) and lithium deuteride ( sup 6 Li sup 2 H sub 3) targets. The proton and deuteron data are combined to extract the neutron structure functions.
Nucleon structure from stochastic estimators
Bali, Gunnar S; Gläßle, Benjamin; Göckeler, Meinulf; Najjar, Johannes; Rödl, Rudolf; Schäfer, Andreas; Sternbeck, André; Söldner, Wolfgang
2013-01-01
Using stochastic estimators for connected meson and baryon three-point functions has successfully been tried in the past years. Compared to the standard sequential source method we trade the freedom to compute the current-to-sink propagator independently of the hadron sink for additional stochastic noise in our observables. In the case of the nucleon we can use this freedom to compute many different sink-momentum/polarization combinations, which grants access to more virtualities. We will present preliminary results on the scalar, electro-magnetic and axial form factors of the nucleon in $N_f=2+1$ lattice QCD and contrast the performance of the stochastic method to the sequential source method. We find the stochastic method to be competitive in terms of errors at fixed cost.
Use of leptons to study the internal structure of nucleons
In the light of recent results in leptoproduction experiments, a review of the lepton deep inelastic scattering is given. The nucleon structure functions are introduced in the frame of the Quark Parton Model, their Q2 evolution is described with the formalism of Quantum Chromodynamic (QCD) to the leading order. The last experimental results from high energy muon-nucleon and neutrino-nucleon scattering experiments are reported and compared with the QCD predictions. All the experiments are in fair agreement and show a small but clear scaling violation corresponding to the rise with Q2 of the quark-antiquark sea and gluon contributions to the nucleon structure functions
The quark structure of the nucleons
The suitableness of the non-relativistic potential model for the description of quarks in nucleons is proved and the model extensively presented. Practical applications are some contributions to the nucleon-nucleon interaction which result from the quark structure of the nucleons. These are especially the quark-gluon exchange and the quark-pion exchange between nucleons. The influences of these interactions on the s and p scattering of the nucleons are calculated in the framework of the resonating-group method. Furthermore we study the change of the quark structure if two nucleons approach very closely. The interaction of the nucleons by quark-gluon exchange causes an increase of the nucleon radius and a shift of the quark momenta to lower values. On this base the momentum distribution of quarks in nuclei is calculated and a natural explanation of the EMC effect is given. The distance distribution of nucleons and their Fermi motion are calculated for this in the shell model. Then we make further considerations in connection with the flavor symmetry, the collapse of the nucleons and the properties of six-quark bags. Altogether it is shown that in the potential model the most different effects of the quark structure of nucleons can be surprisingly well described in an illustrative way. (orig.)
It is unavoidable to deal with the quark and gluon momentum and angular momentum contributions to the nucleon momentum and spin in the study of nucleon internal structure. However we never have the quark and gluon momentum, orbital angular momentum and gluon spin operators which satisfy both the gauge invariance and the canonical momentum and angular momentum commutation relation. The conflicts between the gauge invariance and canonical quantization requirement of these operators are discussed. A new set of quark and gluon momentum, orbital angular momentum and spin operators, which satisfy both the gauge invariance and canonical momentum and angular momentum commutation relation, are proposed. The key point to achieve such a proper decomposition is to separate the gauge field into the pure gauge and the gauge covariant parts. The same conflicts also exist in QED and quantum mechanics and have been solved in the same manner. The impacts of this new decomposition to the nucleon internal structure are discussed. (authors)
Measurement of the nucleon structure function F2 in the nuclear medium and evaluation of its moments
We report on the measurement of inclusive electron scattering off a carbon target performed with CLAS at Jefferson Laboratory. A combination of three different beam energies 1.161, 2.261 and 4.461 GeV allowed us to reach an invariant mass of the final-state hadronic system W∼2.4 GeV with four-momentum transfers Q2 ranging from 0.2 to 5(GeV/c)2. These data, together with previous measurements of the inclusive electron scattering off proton and deuteron, which cover a similar continuous two-dimensional region of Q2 and Bjorken variable x, permit the study of nuclear modifications of the nucleon structure. By using these, as well as other world data, we evaluated the F2 structure function and its moments. Using an OPE-based twist expansion, we studied the Q2-evolution of the moments, obtaining a separation of the leading-twist and the total higher-twist terms. The carbon-to-deuteron ratio of the leading-twist contributions to the F2 moments exhibits the well-known EMC effect, compatible with that discovered previously in x-space. The total higher-twist term in the carbon nucleus appears, although with large systematic uncertainties, to be smaller with respect to the deuteron case for n<7, suggesting partial parton deconfinement in nuclear matter. We speculate that the spatial extension of the nucleon is changed when it is immersed in the nuclear medium.
570 000 neutrino-iron and 370 000 antineutrino-iron charged-current events were obtained from the Wide Band Beam exposure of the CDHS detector at CERN in 1983, at energies ranging from 20 to 400 GeV. These large statistics allowed a precise measurement of the charged-current differential cross-sections and a detailed study of systematic effects. The nucleon structure functions have been determined in the framework of the quark-parton model, in the kinematic range: 0.01522/c2. The longitudinal structure function FL(x) is in good agreement with the QCD predicted shape. Deviations from scale invariance are clearly seen from the functions F2 and xF3. The Q2 evolution of the valence quark distribution has been compared with the QCD prediction in order to measure the scale parameter ?. A good agreement is obtained only if the low Q2 points are removed from the comparison. Our experiment favours a value of ? between 50 and 250 MeV
We have studied the nuclear effects on high energy antineutrino charged current interactions by comparing the data which were taken in the Bubble Chamber BEBC filled with Neon and Deuterium. On the one hand, the study of nuclear reinteractions gave us the possibility to estimate the formation time of hadrons. On the other hand, the comparison of structure functions does not show any significant difference between Neon and Deuterium. Though this result does not contradict the effects observed with charged leptons by the EMC and SLAC experiments, it is strongly incompatible with certain theoretical interpretations which implied a stronger effect in antineutrino interactions
New measurements of nucleon structure functions from the CCFR/NuTeV collaboration
We report on the extraction of the structure functions F2 and ΔxF3=xF3ν-xF3ν-bar from CCFR νμ-Fe and ν-barμ-Fe differential cross sections. The extraction is performed in a physics model independent (PMI) way. This first measurement for ΔxF3, which is useful in testing models of heavy charm production, is higher than current theoretical predictions. The F2 (PMI) values measured in νμ and μ scattering are in good agreement with the predictions of Next to Leading Order PDFs (using massive charm production schemes), thus resolving the long-standing discrepancy between the two sets of data
New Results on Nucleon Spin Structure
Jian-Ping Chen
2005-09-10
Recent precision spin structure data from Jefferson Lab have significantly advanced our knowledge of nucleon structure in the valence quark (high-x) region and improved our understanding of higher-twist effects, spin sum rules and quark-hadron duality. First, results of a precision measurement of the neutron spin asymmetry, A{sub 1}{sup n}, in the high-x region are discussed. The new data shows clearly, for the first time, that A{sub 1}{sup n} becomes positive at high x. They provide crucial input for the global fits to world data to extract polarized parton distribution functions. Preliminary results on A{sub 1}{sup p} and A{sub 1}{sup d} in the high-x region have also become available. The up and down quark spin distributions in the nucleon were extracted. The results for {Delta}d/d disagree with the leading-order pQCD prediction assuming hadron helicity conservation. Then, results of a precision measurement of the g{sub 2}{sup n} structure function to study higher-twist effects are presented. The data show a clear deviation from the lead-twist contribution, indicating a significant higher-twist (twist-3 or higher) effect. The second moment of the spin structure functions and the twist-3 matrix element d{sub 2}{sup n} results were extracted at a high Q{sup 2} of 5 GeV{sup 2} from the measured A{sub 2}{sup n} in the high-x region in combination with existing world data and compared with a Lattice QCD calculation. Results for d{sub 2}{sup n} at low-to-intermediate Q{sup 2} from 0.1 to 0.9 GeV{sup 2} were also extracted from the JLab data. In the same Q{sup 2} range, the Q{sup 2} dependence of the moments of the nucleon spin structure functions was measured, providing a unique bridge linking the quark-gluon picture of the nucleon and the coherent hadronic picture. Sum rules and generalized forward spin polarizabilities were extracted and compared with Chiral Perturbation Theory calculations and phenomenological models. Finally, preliminary results on the resonance spin structure functions in the Q{sup 2} range from 1 to 4 GeV{sup 2} were presented, which, in combination with DIS data, will enable a detailed study of the quark-hadron duality in spin structure functions.
Nasseripour, R; Ambrozewicz, P; Carman, D S; Amaryan, M J; Anciant, E; Anghinolfi, M; Asavapibhop, B; Asryan, G; Audit, G; Auger, T; Avakian, H; Bagdasaryan, H; Baillie, N; Ball, J P; Baltzell, N A; Barrow, S; Battaglieri, M; Beard, K; Bedlinskiy, I; Bektasoglu, M; Bellis, M; Benmouna, N; Berman, B L; Biselli, A S; Blaszczyk, L; Bonner, B E; Bouchigny, S; Boiarinov, S; Bradford, R; Branford, D; Briscoe, W J; Brooks, W K; Burkert, V D; Butuceanu, C; Calarco, J R; Careccia, S L; Casey, L; Cetina, C; Chen, S; Cheng, L; Cole, P L; Collins, P; Coltharp, P; Cords, D; Corvisiero, P; Crabb, D; Credé, V; Dale, D; Dashyan, N; De Masi, R; De Vita, R; De Sanctis, E; Degtyarenko, P V; Dennis, L; Deur, A; Dhuga, K S; Dickson, R; Djalali, C; Dodge, G E; Doughty, D; Dragovitsch, P; Dugger, M; Dytman, S; Dzyubak, O P; Egiyan, H; Egiyan, K S; El Fassi, L; Elouadrhiri, L; Eugenio, P; Fatemi, R; Fedotov, G; Feldman, G; Feuerbach, R J; Forest, T A; Fradi, A; Funsten, H; Garçon, M; Gavalian, G; Gevorgyan, N; Gilfoyle, G P; Giovanetti, K L; Girard, P; Girod, F X; Goetz, J T; Gothe, R W; Griffioen, K A; Guidal, M; Guillo, M; Guler, N; Guo, L; Gyurjyan, V; Hafidi, K; Hakobyan, H; Hanretty, C; Hardie, J; Heddle, D; Hersman, F W; Hicks, K; Hleiqawi, I; Holtrop, M; Hu, J; Hyde-Wright, C E; Ilieva, Y; Ireland, D G; Ishkhanov, B S; Isupov, E L; Ito, M M; Jenkins, D; Jo, H S; Johnstone, J R; Joo, K; Jüngst, H G; Kalantarians, N; Kellie, J D; Khandaker, M; Kim, K Y; Kim, K; Kim, W; Klein, A; Klein, F J; Kossov, M; Krahn, Z; Kramer, L H; Kubarovski, V; Kühn, J; Kuhn, S E; Kuleshov, S V; Kuznetsov, V; Lachniet, J; Laget, J M; Langheinrich, J; Lawrence, D; Livingston, K; Lu, H Y; Lukashin, K; MacCormick, M; Manak, J J; Markov, N; Mattione, P; McAleer, S; McKinnon, B; McNabb, J W C; Mecking, B A; Mestayer, M D; Meyer, C A; Mibe, T; Mikhailov, K; Minehart, R; Mirazita, M; Miskimen, R; Mokeev, V; Moreno, B; Moriya, K; Morrow, S A; Moteabbed, M; Müller, J; Munevar, E; Mutchler, G S; Nadel-Turonski, P; Niccolai, S; Niculescu, G; Niculescu, I; Niczyporuk, B B; Niroula, M R; Niyazov, R A; Nozar, M; Osipenko, M; Ostrovidov, A I; Park, K; Pasyuk, E; Paterson, C; Anefalos Pereira, S; Peterson, G; Philips, S A; Pierce, J; Pivnyuk, N; Pocanic, D; Pogorelko, O; Pozdniakov, S; Preedom, B M; Price, J W; Procureur, S; Prok, Y; Protopopescu, D; Qin, L M; Riccardi, G; Ricco, G; Ripani, M; Ritchie, B G; Rosner, G; Rossi, P; Rubin, P D; Sabati, F; Salamanca, J; Salgado, C; Santoro, J P; Sapunenko, V; Sayre, D; Schumacher, R A; Serov, V S; Shafi, A; Sharabyan, Yu G; Sharov, D; Shvedunov, N V; Simionatto, S; Skabelin, A V; Smith, E S; Smith, L C; Sober, D I; Sokhan, D; Stavinsky, A; Stepanyan, S S; Stepanyan, S; Stokes, B E; Stoler, P; Strakovsky, I I; Strauch, S; Taiuti, M; Taylor, S; Tedeschi, D J; Thoma, U; Thompson, R; Tkabladze, A; Tkachenko, S; Ungaro, M; Vineyard, M F; Vlassov, A V; Wang, K; Watts, D P; Weinstein, L B; Weygand, D P; Williams, M; Wolin, E; Wood, M H; Yegneswaran, A; Yun, J; Zana, L; Zhang, J; Zhao, B; Zhao, Z W
2008-01-01
The first measurements of the polarized structure function $\\sigma_{LT'}$ for the reaction $p(\\vec e,e'K^+)\\Lambda$ in the nucleon resonance region are reported. Measurements are included from threshold up to $W$=2.05 GeV for central values of $Q^2$ of 0.65 and 1.00 GeV$^2$, and nearly the entire kaon center-of-mass angular range. $\\sigma_{LT'}$ is the imaginary part of the longitudinal-transverse response and is expected to be sensitive to interferences between competing intermediate s-channel resonances, as well as resonant and non-resonant processes. The results for $\\sigma_{LT'}$ are comparable in magnitude to previously reported results from CLAS for $\\sigma_{LT}$, the real part of the same response. An intriguing sign change in $\\sigma_{LT'}$ is observed in the high $Q^2$ data at $W\\approx 1.9$ GeV. Comparisons to several existing model predictions are shown.
Long Range Structure of the Nucleon
Vanderhaeghen, Marc; Walcher, Thomas
2010-01-01
The long range structure of the nucleon is discussed starting from the old model of a quark bag with a pion cloud (``cloudy bag'') carrying on to the more recent ideas of the parton model of the nucleon. On the basis of the most recent measurements of the form factors at MAMI, JLab and MIT quantitative results for nucleon charge densities are presented within both non-relativistic and relativistic frameworks.
In the deep inelastic neutrino scattering experiment of the CERN-Dortmund-Heidelberg-Saclay collaboration realized on the CERN SPS narrow band beam, we have measured 23000 charged current neutrino and 6200 antineutrino interactions. The structure functions of the nucleon have been extracted from the differential cross sections on iron and compared with parton model predictions. The total cross sections and the fraction of momentum carried by the antiquarks in the nucleon have been measured as function of the neutrino energy. The structure functions obtained for different Q2 bins show significant deviations from scale invariance. The data are in agreement with QCD predictions for a value of the scale parameter ? between 300 and 700 MeV
Chiral nucleon-nucleon forces in nuclear structure calculations
Coraggio, L; Holt, J W; Itaco, N; Machleidt, R; Marcucci, L E; Sammarruca, F
2016-01-01
Realistic nuclear potentials, derived within chiral perturbation theory, are a major breakthrough in modern nuclear structure theory, since they provide a direct link between nuclear physics and its underlying theory, namely the QCD. As a matter of fact, chiral potentials are tailored on the low-energy regime of nuclear structure physics, and chiral perturbation theory provides on the same footing two-nucleon forces as well as many-body ones. This feature fits well with modern advances in ab-initio methods and realistic shell-model. Here, we will review recent nuclear structure calculations, based on realistic chiral potentials, for both finite nuclei and infinite nuclear matter.
Chiral nucleon-nucleon forces in nuclear structure calculations
Coraggio L.
2016-01-01
Full Text Available Realistic nuclear potentials, derived within chiral perturbation theory, are a major breakthrough in modern nuclear structure theory, since they provide a direct link between nuclear physics and its underlying theory, namely the QCD. As a matter of fact, chiral potentials are tailored on the low-energy regime of nuclear structure physics, and chiral perturbation theory provides on the same footing two-nucleon forces as well as many-body ones. This feature fits well with modern advances in ab-initio methods and realistic shell-model. Here, we will review recent nuclear structure calculations, based on realistic chiral potentials, for both finite nuclei and infinite nuclear matter.
Nucleon spin structure functions
This paper reviews the history of deep inelastic scattering of polarized leptons from polarized protons, culminating in this most recent dramatic claim. I will show that, for the last decade, data have appeared consistent with predictions of the quark model and highlight what the new and potentially exciting data are. I will conclude with suggestions for the future, and discuss the polarization dependence of inclusive hadron production
Various aspects of nuclear physics at intermediate energies, in connection with the description of the nucleon-nucleon potential in terms of mesons, are presented in this thesis. The meson exchange current contribution is studied in the case of the deuteron (np capture and electrodisintegration near threshold). A consistent description of these processes is discussed, with particular emphasis on the effective range of the current, for momentum transfers as large as q2∼1 (GeV/c)2. The structure of finite nuclei and nuclear matter is then analysed in the framework of a relativistic formalism, in which the negative energy component of the nucleon wave function is explicitly taken into account. The nuclear matter saturation mechanism is studied in details and compared with the non-relativistic limit. Properties of finite nuclei are also discussed. Finally, the structure of the nucleon itself in the nuclear medium is investigated. A connection between the polarisation of the nucleon (three valence quark component), the incompressibility parameter and the mass of the first monopole excitation of the nucleon is presented
Weak and electromagnetic probes of nucleon structure
We present some highlights of recent attempts to use the electro-weak interaction to learn about the structure of the nucleon (free and bound). Particular emphasis is placed upon the role of deep-inelastic scattering
Nucleon Resonances and Quark Structure
Londergan, J T
2009-01-01
A pedagogical review of the past 50 years of study of resonances, leading to our understanding of the quark content of baryons and mesons. The level of this review is intended for undergraduates or first-year graduate students. Topics covered include: the quark structure of the proton as revealed through deep inelastic scattering; structure functions and what they reveal about proton structure; and prospects for further studies with new and upgraded facilities, particularly a proposed electron-ion collider.
Transverse Spin Structure of the Nucleon
Perdekamp, Matthias Grosse
2015-01-01
We review the current status and future perspectives of theory and experiments of transverse spin phenomena in high-energy scattering processes off nucleon targets and related issues in nucleon structure and QCD. Systematic exploration of transverse spin effects requires measurements in polarized deep-inelastic scattering, polarized pp collisions, and e+e- annihilations. Sophisticated QCD-based techniques are also needed to analyze the experimental data sets.
Nucleon-pion-state contribution to nucleon two-point correlation functions
Bar, Oliver
2015-01-01
We study the nucleon-pion-state contribution to the QCD two-point function of the standard nucleon interpolating fields. For sufficiently small quark masses these two-particle states are expected to have a smaller total energy than the single-particle excited states. We calculate the nucleon-pion-state contribution to leading order in chiral perturbation theory. Both parity channels are considered. We find the nucleon-pion-state contribution to be small, contributing at the few percent level ...
The spin structure of the nucleon
This document describes the recent experimental results on the spin structure of the nucleon obtained with the electron accelerator Thomas Jefferson National Facility (Jefferson Lab), Virginia. We first discuss the goal of studying the nucleon spin structure and give the basis and phenomenology of high energy lepton scattering. Then, we discuss with some details a few sum rules concerning the spin structure of the nucleon. Those are important tools for studying the nucleon spin structure at Jefferson Lab. We then describe the present experimental situation and analyze the results. We have been able to determine an effective coupling constant for the strong interaction for any regime of quantum chromodynamics which proves that QCD is an approximately conformal theory. We conclude on the perspectives for this field of research, in particular with the 12 GeV energy upgrade of Jefferson Lab. The top priority will be the measurement of generalised parton distributions. The only issue that will stay misunderstood is the role of the very low x domain on the spin structure of the nucleon
In this thesis the nucleon structure function xF3 is determined from the inclusive measurement of the deep inelastic neutrino nucleon charged current interaction. The data were taken in the CERN wide band neutrino beam using the detector of the CERN-Dortmund-Heidelberg-Saclay collaboration. This detector serves at the same time as target, as hadron energy calorimeter and as muon spectrometer. One major aspect of this work was to study the possibility of using high statistics wide band beam data for structure function analysis. The systematic errors specific to this kind of beam are investigated. To obtain the differential cross sections about 100000 neutrino and 75000 antineutrino events in the energy range 20-200 GeV are analysed. The differential cross sections are normalized to the total cross sections, as measured in the narrow band beam by the same collaboration. The calculated structure function xF3 shows significant deviations from scaling. These scaling violations are compared quantitatively with the predictions of quantum chromodynamics. (orig.)
New insights into the spin structure of the nucleon
Bernard, V; Krebs, H; Meißner, U -G
2012-01-01
We analyze the low-energy spin structure of the nucleon in a covariant effective field theory with explicit spin-3/2 degrees of freedom to third order in the small scale expansion. Using the available data on the strong and electromagnetic width of the Delta-resonance, we give parameter-free predictions for various spin-polarizabilities and moments of spin structure functions. We find an improved description of the nucleon spin structure at finite photon virtualities for some observables and point out the necessity of a fourth order calculation.
We report on a detailed study of longitudinal strength in the nucleon resonance region, presenting new results from inclusive electron-proton cross sections measured at Jefferson Lab Hall C in the four-momentum transfer range 0.2 2 2. The data have been used to accurately perform over 170 Rosenbluth-type longitudinal/transverse separations. The precision R σL/σT data are presented here, along with the first separate values of the inelastic structure functions F1 and FL in this regime. The resonance longitudinal component is found to be significant. With the new data, quark-hadron duality is observed above Q2 = 1 GeV2 in the separated structure functions independently
Liang, Y; Ahmidouch, A; Armstrong, C S; Arrington, J; Asaturyan, R; Avery, S; Baker, O K; Beck, D H; Blok, H P; Bochna, C W; Böglin, W; Bosted, P; Bouwhuis, M; Breuer, H; Brown, D S; Brüll, A; Carlini, R D; Cha, J; Chant, N S; Cochran, A; Cole, L; Danagulyan, S; Day, D B; Dunne, J; Dutta, D; Ent, R; Fenker, H C; Fox, B; Gan, L; Gao, H; Garrow, K; Gaskell, D; Gasparian, A; Geesaman, D F; Gilman, R; Gueye, P L J; Harvey, M; Holt, R J; Jiang, X; Jones, M; Keppel, C E; Kinney, E; Lorenzon, W; Lung, A; Mack, D J; Markowitz, P; Martin, J W; McIlhany, K; McKee, D; Meekins, D; Miller, M A; Milner, R G; Mitchell, J H; Mkrtchyan, H G; Müller, B A; Nathan, A; Niculescu, G; Niculescu, I; O'Neill, T G; Papavassiliou, V; Pate, S F; Piercey, R B; Potterveld, D; Ransome, R D; Reinhold, J; Rollinde, E; Rondon, Oscar A; Roos, P; Sarty, A J; Sawafta, R; Schulte, E C; Segbefia, E; Smith, C; Stepanyan, S; Strauch, S; Tadevosyan, V; Tang, L; Tieulent, R; Tvaskis, V; Uzzle, A; Vulcan, W F; Wood, S A; Xiong, F; Yuan, L; Zeier, M; Zihlmann, B; Ziskin, V
2004-01-01
We report on a detailed study of longitudinal strength in the nucleon resonance region, presenting new results from inclusive electron-proton cross sections measured at Jefferson Lab Hall C in the four-momentum transfer range 0.2 < Q^2 < 5.5 GeV^2. The data have been used to accurately perform over 170 Rosenbluth-type longitudinal / transverse separations. The precision R = sigma_L / sigma_T data are presented here, along with the first separate values of the inelastic structure functions F_1 and F_L in this regime. The resonance longitudinal component is found to be significant. With the new data, quark-hadron duality is observed above Q^2 = 1 GeV^2 in the separated structure functions independently.
Yongguang Liang; Michael Christy; Abdellah Ahmidouch; Christopher Armstrong; John Arrington; Arshak Asaturyan; Steven Avery; O. Baker; Douglas Beck; Henk Blok; C.W. Bochna; Werner Boeglin; Peter Bosted; Maurice Bouwhuis; Herbert Breuer; Daniel Brown; Antje Bruell; Roger Carlini; Jinseok Cha; Nicholas Chant; Anthony Cochran; Leon Cole; Samuel Danagoulian; Donal Day; James Dunne; Dipangkar Dutta; Rolf Ent; Howard Fenker; B. Fox; Liping Gan; Haiyan Gao; Kenneth Garrow; David Gaskell; Ashot Gasparian; Don Geesaman; Ronald Gilman; Paul Gueye; Mark Harvey; Roy Holt; Xiaodong Jiang; Mark Jones; Cynthia Keppel; Edward Kinney; Wolfgang Lorenzon; Allison Lung; David Mack; Pete Markowitz; J.W. Martin; Kevin McIlhany; Daniella Mckee; David Meekins; M.A. Miller; Richard Milner; Joseph Mitchell; Hamlet Mkrtchyan; Robert Mueller; Alan Nathan; Gabriel Niculescu; Maria-Ioana Niculescu; Thomas O' neill; Vassilios Papavassiliou; Stephen Pate; Rodney Piercey; David Potterveld; Ronald Ransome; Joerg Reinhold; E. Rollinde; Oscar Rondon-Aramayo; Philip Roos; Adam Sarty; Reyad Sawafta; Elaine Schulte; Edwin Segbefia; C. Smith; Samuel Stepanyan; Steffen Strauch; Vardan Tadevosyan; Liguang Tang; Raphael Tieulent; Vladas Tvaskis; Alicia Uzzle; William Vulcan; Stephen Wood; Feng Xiong; Lulin Yuan; Markus Zeier; Benedikt Zihlmann; Vitaliy Ziskin
2004-10-01
We report on a detailed study of longitudinal strength in the nucleon resonance region, presenting new results from inclusive electron-proton cross sections measured at Jefferson Lab Hall C in the four-momentum transfer range 0.2 < Q{sup 2} < 5.5 GeV{sup 2}. The data have been used to accurately perform over 170 Rosenbluth-type longitudinal/transverse separations. The precision R = {sigma}{sub L}/{sigma}{sub T} data are presented here, along with the first separate values of the inelastic structure functions F{sub 1} and F{sub L} in this regime. The resonance longitudinal component is found to be significant. With the new data, quark-hadron duality is observed above Q{sup 2} = 1 GeV{sup 2} in the separated structure functions independently.
Nucleon structure and the chiral filter
I discuss the issues of quenched gA in nuclei, pionic enhancement of nuclear electromagnetic form factors, manifestation of the anomalous Wess-Zumino term in nuclear medium, all on the same footing, in terms of the nucleon structure as 'derived' from a low-energy effective theory of QCD
Nucleon structure study by virtual Compton scattering
It is proposed to study nucleon structure by virtual Compton scattering using the Hall A HRS spectrometers. This reaction is planned to be measured in the Roper resonance region and at the highest center of mass energy to observe the beginning of the hard scattering regime. (author) 25 refs.; 8 figs.; 6 tabs
A covariant model for the nucleon spin structure
Ramalho, G
2015-01-01
We present the results of the covariant spectator quark model applied to the nucleon structure function $f(x)$ measured in unpolarized deep inelastic scattering, and the structure functions $g_1(x)$ and $g_2(x)$ measured in deep inelastic scattering using polarized beams and targets ($x$ is the Bjorken scaling variable). The nucleon is modeled by a valence quark-diquark structure with $S,P$ and $D$ components. The shape of the wave functions and the relative strength of each component are fixed by making fits to the deep inelastic scattering data for the structure functions $f(x)$ and $g_1(x)$. The model is then used to make predictions on the function $g_2(x)$ for the proton and neutron.
Nucleon spin structure studies at COMPASS
Marchand, Claude
2006-01-01
One of the main goal of the COMPASS experiment at CERN is the study of the spin structure of the nucleon in DIS, by scattering 160 GeV polarized muon beam on a longitudinally (or transversely) polarized $^{6}$LiD target. Besides the scattered muon, the particles produced in the deep inelastic scattering are detected by a two stage magnetic spectrometer equipped with state of the art tracking and particle ID detectors. The emphasis of COMPASS muon program is the direct determination of the gluon polarization $\\Delta G/G$, accessed via asymmetries involving photon-gluon fusion mechanism (PGF). Both open charm production (detecting $D^{0}$s), as well as production of hight $p_{T}$ hadron pairs are used to tag PGF. Preliminary results for $\\Delta G/G$ based on the analysis of 2002 and 2003 data are shown. In addition, improved measurement of the deuteron structure function $g^{d}_{1}$ at small $x$, as well as studies of transverse distribution functions in the deuteron by measuring Collins and Sivers azimuthal...
Preliminary results on the measurement of the structure functions F2p(xBj, Q2) and F2d(xBj, Q2) and of the ratio F2n/F2p from experiment E665 are presented. The data were obtained using 465 GeV/c muons scattering off liquid hydrogen and deuterium targets. The dependence of the structure functions on xBj and Q2 is examined in the kinematic range xBj > 8 x 10-4 and Q2 > 0.2 GeV2/c2. The structure function ratio is presented as a function of xBj, for xBj > 10-6
Structure and Spin of the Nucleon
Avakian, Harut A. [JLAB
2014-03-01
Parton distribution functions, describing longitudinal momentum, helicity and transversity distributions of quarks and gluons, have been recently generalized to account also for transverse degrees of freedom. Two new sets of more general distributions, Transverse Momentum Distributions and Generalized Parton Distributions, were introduced to describe transverse momentum and space distributions of partons. Great progress has been made since then in measurements of different Single Spin Asymmetries (SSAs) in semi-inclusive and hard exclusive processes providing access to TMDs and GPDs, respectively. Facilities world-wide involved in studies of the 3D structure of nucleon include HERMES, COMPASS, BELLE, BaBar, Halls A, B, and C at JLab, and PHENIX and STAR at RHIC (BNL). TMD studies in the Drell-Yan process are also becoming an important part of the program of hadron scattering experiments. Studies of TMDs are also among the main driving forces of the JLab 12-GeV upgrade project, several of the forward upgrade proposals of STAR and PHENIX at RHIC, and future facilities, such as the Electron Ion Collider (EIC), FAIR in Germany, and NICA in Russia. In this contribution we present an overview of the latest developments in studies of parton distributions and discuss newly released results, ongoing activities, as well as some future measurements.
Nucleon structure and high energy interactions
Selyugin, O V
2015-01-01
On the basis of the representation of the generalized structure of nucleons a new model of the hadron interaction at high energies is presented. The new t-dependence of the generalized parton distributions (GPDs) is obtained from the comparative analysis of different sets of the parton distribution functions (PDFs), based on the description of the whole sets of experimental data of electromagnetic form factors of the proton and neutron. Taking into account the different moments of GPDs of the hadron the quantitative descriptions of all existing experimental data of the proton-proton and proton-antiproton elastic scattering from $\\sqrt{s} = 9.8$ GeV to $8$ TeV, including the Coulomb range and large momentum transfers up to $-t=15$ GeV$^2$, are obtained with a few free fitting high energy parameters. The real part of the hadronic elastic scattering amplitude is determined only through complex $s$ satisfying the dispersion relations. The negligible contributions of the hard Pomeron and the presence of the non-sm...
Nucleon Structure and Generalized Parton Distributions
Eric Voutier
2006-06-28
This paper discusses a selected part of the experimental program dedicated to the study of Generalized Parton Distributions, a recently introduced concept which provides a comprehensive framework for investigations of the partonic structure of the nucleon. Particular emphasis is put on the Deeply Virtual Compton Scattering program performed at the Jefferson Laboratory. The short and long term future of this program is also discussed in the context of the several experimental efforts aiming at a complete and exhaustive mapping of Generalized Parton Distributions.
Within the chiral bag model (CBM) the spin-dependent structure functions of a polarized proton g1p(x) and polarized neutron g1n(x) are investigated. The results obtained within CBM with a scalar πqq coupling agree with EMC experimental data rather well. 11 refs.; 1 fig.; 2 tabs
Nucleon structure as a background for determination of fundamental parameters
We consider deep inelastic, (quasi-) elastic lepton-nucleon scattering and investigate the possibilities of eliminating or suppressing theoretical uncertainties induced by nucleon structure in measuring the Standard Model parameters or in searching for new physics. On the basis of rather general hypothesis about nucleon structure we have obtained new relations between cross sections and neutral current parameters which are independent of the nucleon structure. We also investigate a dependence of the QCD Λ-parameter extracted from the data on unknown large scale nucleon structure and propose a modification of the conventional QCD predictions which are weakly dependent of this uncertainty factor. (author). 9 refs, 1 tab
THE SPIN STRUCTURE OF THE NUCLEON
For many years now, spin has played a very prominent role in QCD. The field of QCD spin physics has been carried by the hugely successful experimental program of polarized deeply-inelastic lepton-nucleon scattering (DIS), and by a simultaneous tremendous progress in theory. A new milestone has now been reached with the advent of RHIC, the world's first polarized proton-proton collider. RHIC is poised to help answer many of the important question pertaining to the spin structure of the nucleon. Recently, it has also been proposed to study spin phenomena in transversely polarized (bar p)p collisions at the planned GSI-FAIR facility. This talk describes some of the opportunities provided by RHIC and the proposed GSI experiments
Spin structure of the nucleon at low energies
Bernard, Véronique(Institut de Physique Nucléaire, CNRS/Univ. Paris-Sud 11 (UMR 8608), Orsay Cedex, F-91406, France); Hemmert, Thomas R.; Meißner, Ulf-G.
2002-01-01
The spin structure of the nucleon is analyzed in the framework of a Lorentz-invariant formulation of baryon chiral perturbation theory. The structure functions of doubly virtual Compton scattering are calculated to one-loop accuracy (fourth order in the chiral expansion). We discuss the generalization of the Gerasimov-Drell-Hearn sum rule, the Burkhardt-Cottingham sum rule and moments of these. We give predictions for the forward and the longitudinal-transverse spin polarizabilities of the pr...
Bollini, D; Benvenuti, Alberto C; Bozzo, M; Brun, R; Cvach, J; Dobrowolski, T; Fadeev, N G; Feltesse, J; Frabetti, P L; Gennow, H; Golutvin, I A; Goossens, M; Heiman, G; Jamnik, D; Kiryushin, Yu T; Kisselev, V S; Klein, M; Kopp, R; Krivokhizhin, V G; Kukhtin, V V; Maillard, J; Malasoma, J M; Meyer-Berkhout, U; Milsztajn, A; Monari, L; Navach, F; Navarria, Francesco Luigi; Nowak, Wolf-Dieter; Piemontese, L; Pilcher, J E; Renardy, J F; Sacquin, Yu; Savin, I A; Schinzel, D; Smadja, G; Smirnov, G I; Staude, A; Teichert, K M; Tirler, R; Verrecchia, P; Vesztergombi, G; Virchaux, M; Volodko, A G; Voss, R; Zácek, J; Zupancic, Crtomir
1981-01-01
Deep inelastic scattering cross sections have been measured with the CERN SPS muon beam at incident energies of 120 and 200 GeV. Approximately 10000 events at each energy used to obtain the structure function F/sub 2/(x, Q/sup 2/) in the kinematic region 0.3
Di-hadron fragmentation and mapping of the nucleon structure
Pisano, Silvia
2015-01-01
The fragmentation of a colored parton directly into a pair of colorless hadrons is a non-perturbative mechanism that offers important insights into the nucleon structure. Di-hadron fragmentation functions can be extracted from semi-inclusive electron-positron annihilation data. They also appear in observables describing the semi-inclusive production of two hadrons in deep-inelastic scattering of leptons off nucleons or in hadron-hadron collisions. When a target nucleon is transversely polarized, a specific chiral-odd di-hadron fragmentation function can be used as the analyzer of the net density of transversely polarized quarks in a transversely polarized nucleon, the so-called transversity distribution. The latter can be extracted through suitable single-spin asymmetries in the framework of collinear factorization, thus in a much simpler framework with respect to the traditional one in single-hadron fragmentation. At subleading twist, the same chiral-odd di-hadron fragmentation function provides the cleanest...
Electromagnetic studies of nucleon and nuclear structure
Important objectives of the group are the study of subatomic structure through experimental measurements and the interpretation of the data through modeling. The common theme that unifies the studies of strong interactions and hadronic systems is the effort to determine the electromagnetic response as completely as possible. The general approach is coincidence detection of exclusive final states and determination of the dependence on the spin variables using polarized beams and targets and outgoing nucleon polarimetry. Direct reaction and giant resonance studies of electron quasi-elastic scattering on 12C and 16O are reported, as well as work on nuclear structure models and instrumentation development
Internal Spin Structure of the Nucleon in Polarized Deep Inelastic Muon-Nucleon Scattering
We present the study of the internal spin structure of the nucleon in spin-dependent deep inelastic scattering of muons on nucleons. The data were taken by the NA47 experiment of the Spin Muon Collaboration (SMC) on the high energy muon beam at CERN. The experiment used the polarized proton and deuteron targets. The structure function g1p(x) and g1d(x) were determined from the asymmetries of the spin-dependent event rates in the range of 0.0032>=10 GeV2. Using the first moments of these structure functions an agreement with the Bjorken sum rule prediction was found within one standard deviation. The first moments of g1(x), for both proton and deuteron, are smaller than the Ellis-Jaffe sum rule prediction. This disagreement can be interpreted in terms of negative polarization of the strange sea in the nucleon. The singlet part of the axial current matrix element can be interpreted as an overall spin carried by quarks in the nucleon. Its value is significantly smaller than nucleon spin. Semi-inclusive asymmetries of yields of positive and negative hadrons produced on both targets were also measured and analysed in term of quark-parton model, together with inclusive asymmetries. From this analysis the quark spin distributions were determined, separately for valence u and d quarks and for non-strange sea quarks. Valence u quarks are positively polarized and their polarization increases with x. Valence d quarks are negatively polarized and their polarization does not exhibit any x-dependence. The non-strange sea is unpolarized in the whole measured range of x. The first moments of the valance quark spin distributions were found consistent with the values obtained from weak decay constants F and D and their second moments are consistent with lattice QCD calculations. In the QCD analysis of the world data the first moment of the gluon spin distribution was found with a large error. Also, a search for a non-perturbative anomaly at high x was done on the world data and the result was consistent with null. An extensive discussion of the SMC results and a comparison with results of SLAC experiment is presented. The new experiment of the COMPASS Collaboration, approved and being currently in preparation at CERN, was presented. The main physics issues of the muon part of this experiment, which are the gluon polarization and a continuation of the physics program of the SMC, were discussed. (author)
Nucleon structure and properties of dense matter
We consider the properties of dense matter in a framework of the Skyrme soliton model and the chiral bag model. The influence of the nucleon structure on the equation of state of dense matter is emphasized. We find that in both models the energy per unit volume is proportional to n4/3, n being the baryon number density. We discuss the properties of neutron stars with a derived equation of state. The role of many-body effects is investigated. The effect of including higher order terms in the chiral lagrangian is examined. The phase transition to quark matter is studied. 29 refs., 6 figs. (author)
Structure of the nucleon and nuclei studied by HERMES
Recent results from studies of inclusive and semi-inclusive deep-inelastic lepton scattering are presented. Data with polarization provide the first measurement of the b1(x, Q2) structure function in the deuteron, a five component flavor decomposition of quark helcity distributions in the nucleon, as well as results pertaining to transverse spin physics and deep virtual Compton scattering. Data from unpolarized targets constrain models of quark hadronization and give a measure of parton energy loss in cold nuclear matter
Nucleon-nucleon scattering in the functional quantum theory of the nonlinear spinor field
The author calculates the S matrix for the elastic nucleon-nucleon scattering in the lowest approximation using the quantum theory of nonlinear spinor fields with special emphasis to the ghost configuration of this theory. Introducing a general scalar product a new functional channel calculus is considered. From the results the R and T matrix elements and the differential and integral cross sections are derived. (HSI)
Nucleon wave function from lattice QCD
Warkentin, Nikolaus
2008-04-15
In this work we develop a systematic approach to calculate moments of leading-twist and next-to-leading twist baryon distribution amplitudes within lattice QCD. Using two flavours of dynamical clover fermions we determine low moments of nucleon distribution amplitudes as well as constants relevant for proton decay calculations in grand unified theories. The deviations of the leading-twist nucleon distribution amplitude from its asymptotic form, which we obtain, are less pronounced than sometimes claimed in the literature. The results are applied within the light cone sum rule approach to calculate nucleon form factors that are compared with recent experimental data. (orig.)
Nucleon wave function from lattice QCD
In this work we develop a systematic approach to calculate moments of leading-twist and next-to-leading twist baryon distribution amplitudes within lattice QCD. Using two flavours of dynamical clover fermions we determine low moments of nucleon distribution amplitudes as well as constants relevant for proton decay calculations in grand unified theories. The deviations of the leading-twist nucleon distribution amplitude from its asymptotic form, which we obtain, are less pronounced than sometimes claimed in the literature. The results are applied within the light cone sum rule approach to calculate nucleon form factors that are compared with recent experimental data. (orig.)
A Study of Nucleon Spin Structure from Quantum Chromodynamics
Osborne, J
2001-01-01
I present an introduction to the field of Quantum Chromodynamics (QCD) with emphasis on nucleon spin structure and perturbative methods. After a somewhat comprehensive overview of perturbative QCD, including the systematics of renormalization, I introduce deeply-inelastic scattering and deeply-virtual Compton scattering along with the nonperturbative distribution functions appearing in these processes. I show how these processes can be used to extract the distribution of longitudinal spin of nucleons, and briefly discuss the complications associated with transverse spin components. There are five appendices which accompany this work, discussing topics ranging from canonical field quantization to dimensional regularization to the structure of several important Lie groups. These appendices are meant to give the reader a certain basic understanding of some of the mathematical details underlying the main text, as well as provide a useful reference. This work was submitted in a slightly different form to the Facul...
Nucleon wave function from lattice QCD
Warkentin, Nikolaus
2008-01-01
In this work we develop a systematic approach to calculate moments of leading-twist and next-to-leading twist baryon distribution amplitudes within lattice QCD. Using two flavours of dynamical clover fermions we determine low moments of nucleon distribution amplitudes as well as constants relevant for proton decay calculations in grand unified theories. The deviations of the leading-twist nucleon distribution amplitude from its asymptotic form, which we obtain, are less pronounced than someti...
The results from a high statistics study of the nucleon structure function F2(x, Q2) in the kinematic range x ≥ 0.25 and Q2 ≥ 25 GeV2 are presented. The analysis is based on 1.5x106 reconstructed events recorded at beam energies of 120, 200 and 280 GeV. By comparing data taken at different beam energies, it is found that a ratio R=δL/δT=0.015±0.013 (stat.) ±0.026 (syst.) is independent of x in the range 0.25 ≤ x ≤ 0.7 and 50 GeV2 ≤ Q2 ≤ 150 GeV2. The kinematic region of these data makes them well suited for quantitative tests of quantum chromodynamics (QCD). From a next-to-leading order nonsinglet fit, a QCD mass scale parameter ΛM-barS-bar=225±20 (stat.)-60+70 (syst.) MeV is founded
Nasseripour, Rakhsha; Raue, Brian; Ambrozewicz, Pawel; Carman, Daniel; Amaryan, Moscov; Amaryan, Moskov; Anciant, Eric; Anghinolfi, Marco; Asavapibhop, Burin; Asryan, Gegham; Audit, Gerard; Auger, Thierry; Avagyan, Harutyun; Baghdasaryan, Hovhannes; Baillie, Nathan; Ball, J.P.; Ball, Jacques; Ball, J.P.; Ball, Jacques; Ball, J.P.; Ball, Jacques; Ball, J.P.; Ball, Jacques; Baltzell, Nathan; Barrow, Steve; Battaglieri, Marco; Beard, Kevin; Bedlinskiy, Ivan; Bektasoglu, Mehmet; Bellis, Matthew; Benmouna, Nawal; Berman, Barry; Biselli, Angela; Blaszczyk, Lukasz; Bonner, Billy; Bouchigny, Sylvain; Boyarinov, Sergey; Bradford, Robert; Branford, Derek; Briscoe, William; Brooks, William; Burkert, Volker; Butuceanu, Cornel; Calarco, John; Careccia, Sharon; Casey, Liam; Cetina, Catalina; Chen, Shifeng; Cheng, Lu; Cole, Philip; Collins, Patrick; Coltharp, Philip; Cords, Dieter; Corvisiero, Pietro; Crabb, Donald; Crede, Volker; Dale, Daniel; Dashyan, Natalya; De Masi, Rita; De Vita, Raffaella; De Sanctis, Enzo; Degtiarenko, Pavel; Dennis, Lawrence; Deur, Alexandre; Dhuga, Kalvir; Dickson, Richard; Djalali, Chaden; Dodge, Gail; Doughty, David; Dragovitsch, Peter; Dugger, Michael; Dytman, Steven; Dzyubak, Oleksandr; Egiyan, Hovanes; Egiyan, Kim; Elfassi, Lamiaa; Elouadrhiri, Latifa; Eugenio, Paul; Fatemi, Renee; Fedotov, Gleb; Feldman, Gerald; Feuerbach, Robert; Forest, Tony; Fradi, Ahmed; Funsten, Herbert; Garcon, Michel; Gavalian, Gagik; Gevorgyan, Nerses; Gilfoyle, Gerard; Giovanetti, Kevin; Girard, Pascal; Girod, Francois-Xavier; Goetz, John; Gothe, Ralf; Gothe, Ralf; Griffioen, Keith; Guidal, Michel; Guillo, Matthieu; Guler, Nevzat; Guo, Lei; Gyurjyan, Vardan; Hafidi, Kawtar; Hakobyan, Hayk; Hanretty, Charles; Hardie, John; Heddle, David; Hersman, F.; Hicks, Kenneth; Hleiqawi, Ishaq; Holtrop, Maurik; Hu, Jicun; Hyde, Charles; Ilieva, Yordanka; Ireland, David; Ishkhanov, Boris; Isupov, Evgeny; Ito, Mark; Jenkins, David; Jo, Hyon-Suk; Johnstone, John; Joo, Kyungseon; Juengst, Henry; Kalantarians, Narbe; Kellie, James; Khandaker, Mahbubul; Kim, Kui; Kim, Kyungmo; Kim, Wooyoung; Klein, Andreas; Klein, Franz; Kossov, Mikhail; Krahn, Zebulun; Kramer, Laird; Kubarovsky, Valery; Kuhn, Joachim; Kuhn, Sebastian; Kuleshov, Sergey; Kuznetsov, Viacheslav; Lachniet, Jeff; Laget, Jean; Langheinrich, Jorn; Lawrence, David; Livingston, Kenneth; Lu, Haiyun; Lukashin, Konstantin; MacCormick, Marion; Manak, Joseph; Markov, Nikolai; Mattione, Paul; McAleer, Simeon; McKinnon, Bryan; McNabb, John; Mecking, Bernhard; Mestayer, Mac; Meyer, Curtis; Mibe, Tsutomu; Mikhaylov, Konstantin; Minehart, Ralph; Mirazita, Marco; Miskimen, Rory; Mokeev, Viktor; Moreno, Brahim; Moriya, Kei; Morrow, Steven; Moteabbed, Maryam; Mueller, James; Munevar Espitia, Edwin; Mutchler, Gordon; Nadel-Turonski, Pawel; Niccolai, Silvia; Niculescu, Gabriel; Niculescu, Maria-Ioana; Niczyporuk, Bogdan; Niroula, Megh; Niyazov, Rustam; Nozar, Mina; Osipenko, Mikhail; Ostrovidov, Alexander; Park, Kijun; Pasyuk, Evgueni; Paterson, Craig; Pereira, Sergio; Peterson, Gerald; Philips, Sasha; Pierce, Joshua; Pivnyuk, Nikolay; Pocanic, Dinko; Pogorelko, Oleg; Pozdnyakov, Sergey; Preedom, Barry; Price, John; Procureur, Sebastien; Prok, Yelena; Protopopescu, Dan; Qin, Liming; Riccardi, Gregory; Ricco, Giovanni; Ripani, Marco; Ritchie, Barry; Rosner, Guenther; Rossi, Patrizia; Rubin, Philip; Sabatie, Franck; Salamanca, Julian; Salgado, Carlos; Santoro, Joseph; Sapunenko, Vladimir; Sayre, Donald; Schumacher, Reinhard; Serov, Vladimir; Shafi, Aziz; Sharabian, Youri; Sharov, Dmitri; Shvedunov, Nikolay; Simionatto, Sebastio; Skabelin, Alexander; Smith, Elton; Smith, Lee; Sober, Daniel; Sokhan, Daria; Stavinsky, Aleksey; Stepanyan, Samuel; Stepanyan, Stepan; Stokes, Burnham; Stoler, Paul; Strakovski, Igor; Strauch, Steffen; Taiuti, Mauro; Taylor, Shawn; Tedeschi, David; Thoma, Ulrike; Thompson, Richard; Tkabladze, Avtandil; Tkachenko, Svyatoslav; Ungaro, Maurizio; Vineyard, Michael; Vlassov, Alexander; Wang,
2008-06-01
The first measurements of the polarized structure function $\\sigma_{LT'}$ for the reaction $p(\\vec e,e'K^+)\\Lambda$ in the nucleon resonance region are reported. Measurements are included from threshold up to $W$=2.05 GeV for central values of $Q^2$ of 0.65 and 1.00 GeV$^2$, and nearly the entire kaon center-of-mass angular range. $\\sigma_{LT'}$ is the imaginary part of the longitudinal-transverse response and is expected to be sensitive to interferences between competing intermediate s-channel resonances, as well as resonant and non-resonant processes. The results for $\\sigma_{LT'}$ are comparable in magnitude to previously reported results from CLAS for $\\sigma_{LT}$, the real part of the same response. An intriguing sign change in $\\sigma_{LT'}$ is observed in the high $Q^2$ data at $W\\approx 1.9$ GeV. Comparisons to several existing model predictions are shown.
Polarized structure function σLT#prime#, for p((rvec e),e(prime)K+)Λ in the nucleon resonance region
The first measurements of the polarized structure function σLT#prime#, for the reaction p((rvec e),e(prime)K+)Λ in the nucleon resonance region are reported. Measurements are included from threshold up to W = 2.05 GeV for central values of Q2 of 0.65 and 1.00 GeV2, and nearly the entire kaon center-of-mass angular range. σLT#prime# is the imaginary part of the longitudinal-transverse response and is expected to be sensitive to interferences between competing intermediate s-channel resonances, as well as resonant and non-resonant processes. The results for σLT#prime# are comparable in magnitude to previously reported results from CLAS for σLT#prime#, the real part of the same response. An intriguing sign change in σLT#prime# is observed in the high Q2 data at W ∼ 1.9 GeV. Comparisons to several existing model predictions are shown
Equidistant structure and effective nucleon mass in nuclear matter
The effective nucleon mass of the Equidistant Multi-Layer Structure (EMULS) is discussed self-consistently. In the density region where the Fermi gas state in nuclear matter is unstable against the density fluctuation, the EMULS gives lower binding energy. It is, however, shown that such a structure with an ordinary nucleon mass collapses due to too strong attraction. We point out that such a collapse can be avoided by taking account of an effective nucleon mass affected by the localization of nucleons. (author)
The pion-cloud contribution to the electromagnetic nucleon structure
Kupelwieser, D
2015-01-01
The present contribution continues and extends foregoing work on the calculation of electroweak form factors of hadrons using the point-form of relativistic quantum mechanics. Here we are particularly interested in studying pionic effects on the electromagnetic structure of the nucleon. To this aim we employ a hybrid constituent-quark model that comprises, in addition to the $3q$ valence component, also a $3q$+$\\pi$ non-valence component. With a simple wave function for the $3q$ component we get reasonable results for the nucleon form factors. In accordance with other authors we find that the pionic effect is significant only below $Q^2\\lesssim 0.5$~GeV$^2$.
Structure and spin of the nucleon
Avakian H.
2014-03-01
Great progress has been made since then in measurements of different Single Spin Asymmetries (SSAs in semi-inclusive and hard exclusive processes providing access to TMDs and GPDs, respectively. Facilities world-wide involved in studies of the 3D structure of nucleon include HERMES, COMPASS, BELLE, BaBar, Halls A, B, and C at JLab, and PHENIX and STAR at RHIC (BNL. TMD studies in the Drell-Yan process are also becoming an important part of the program of hadron scattering experiments. Studies of TMDs are also among the main driving forces of the JLab 12-GeV upgrade project, several of the forward upgrade proposals of STAR and PHENIX at RHIC, and future facilities, such as the Electron Ion Collider (EIC, FAIR in Germany, and NICA in Russia. In this contribution we present an overview of the latest developments in studies of parton distributions and discuss newly released results, ongoing activities, as well as some future measurements.
Nucleon effective mass effects on the Pauli-blocking function
The effects of nucleon effective mass on the Pauli-blocking function are worked out. We have shown that such effects on the quasi-deuteron mechanism of photonuclear absorption are rather relevant. The pauli-blocking function has been evaluated by applying a Monte Carlo calculation particularly suitable for simulation of intranuclear cascade process of intermediate-energy nuclear reactions. The nucleon binding in the photonuclear absorption mechanism is accordingly taken into account. (author)
The structure of the nucleon: Elastic electromagnetic form factors
Precise proton and neutron form factor measurements at Jefferson Lab, using spin observables, have recently made a significant contribution to the unraveling of the internal structure of the nucleon. Accurate experimental measurements of the nucleon form factors are a test-bed for understanding how the nucleon's static properties and dynamical behavior emerge from QCD, the theory of the strong interactions between quarks. There has been enormous theoretical progress, since the publication of the Jefferson Lab proton form factor ratio data, aiming at reevaluating the picture of the nucleon. We will review the experimental and theoretical developments in this field and discuss the outlook for the future. (orig.)
Spin and Orbital Angular Momentum Distribution Functions of the Nucleon
Wakamatsu, M.; Watabe, T
1999-01-01
A theoretical prediction is given for the spin and orbital angular momentum distribution functions of the nucleon within the framework of an effective quark model of QCD, i.e. the chiral quark soliton model. An outstanding feature of the model is that it predicts fairly small quark spin fraction of the nucleon $\\Delta \\Sigma \\simeq 0.35$, which in turn dictates that the remaining 65% of the nucleon spin is carried by the orbital angular momentum of quarks and antiquarks at the model energy sc...
Nucleon Structure and Hyperon Form Factors from Lattice QCD
In this work, I report the latest lattice QCD calculations of nucleon and hyperon structure from chiral fermions in 2+1-flavor dynamical simulations. All calculations are done with a chirally symmetric fermion action, domain-wall fermions, for valence quarks. I begin with the latest lattice results on the nucleon structure, focusing on results from RBC/UKQCD using 2+1-flavor chiral fermion actions. We find the chiral-extrapolated axial coupling constant at physical pion mass point. to be 1.23(5), consistent with experimental value. The renormalization constants for the structure functions are obtained from RI/MOM-scheme non-perturbative renormalization. We find first moments of the polarized and unpolarized nucleon structure functions at zero transfer momentum to be 0.133(13) and 0.203(23) respectively, using continuum chiral extrapolation. These are consistent with the experimental values, unlike previous calculations which have been 50% larger. We also have a prediction for the transversity, which we find to be 0.56(4). The twist-3 matrix element is consistent with zero which agrees with the prediction of the Wandzura-Wilczek relation. In the second half of this work, I report an indirect dynamical estimation of the strangeness proton magnetic moments using mixed actions. With the analysis of hyperon form factors and using charge symmetry, the strangeness of proton is found to be -0.066(2G), consistent with the Adelaide-JLab Collaboration's result. The hyperon Σ and Ξ axial coupling constants are also performed for the first time in a lattice calculation, gσσ = 0.441(14) and gΞΞ -0.277(11)
Nucleon Structure and hyperon form factors from lattice QCD
In this work, I report the latest lattice QCD calculations of nucleon and hyperon structure from chiral fermions in 2+1-flavor dynamical simulations. All calculations are done with a chirally symmetric fermion action, domain-wall fermions, for valence quarks. I begin with the latest lattice results on the nucleon structure, focusing on results from RBC/UKQCD using 2+1-flavor chiral fermion actions. We find the chiral-extrapolated axial coupling constant at physical pion mass point to be 1.23(5), consistent with experimental value. The renormalization constants for the structure functions are obtained from RI/MOM-scheme non-perturbative renormalization. We find first moments of the polarized and unpolarized nucleon structure functions at zero transfer momentum to be 0.133(13) and 0.203(23) respectively, using continuum chiral extrapolation. These are consistent with the experimental values, unlike previous calculations which have been 50% larger. We also have a prediction for the transversity, which we find to be 0.56(4). The twist-3 matrix element is consistent with zero which agrees with the prediction of the Wandzura-Wilczek relation. In the second half of this work, I report an indirect dynamical estimation of the strangeness proton magnetic moments using mixed actions. With the analysis of hyperon form factors and using charge symmetry, the strangeness of proton is found to be -0.066(26), consistent with the Adelaide-JLab Collaboration's result. The hyperon Sigma and Xi axial coupling constants are also performed for the first time in a lattice calculation, g#Sigma##Sigma# = 0.441(14) and g#Xi##Xi# = -0.277(11)
Boson-exchange nucleon-nucleon potential and nuclear structure
A fully momentum-dependent one-boson-exchange potential is derived which takes into account the mesons, π, eta, sigma, rho, ω and phi. Scattering bound states and nuclear matter properties are studied in momentum space. The use of such potential is shown to be as easy as the use of more simple phenomenological interactions. In nuclear matter the formalism of Bethe-Goldstone is chosen to compute the binding energy versus density in the approximation of two-body and three-body correlations. The three-body correlated wave function obtained is then used
Short-range correlations of partons & 3D nucleon structure
Schweitzer P.
2014-03-01
Full Text Available Dynamical breaking of chiral symmetry in QCD is caused by non-perturbative interactions on a scale ρ ∼ 0.3 fm much smaller than the hadronic size R ∼ 1 fm. This has important consequences for the nucleon structure such as the prediction that the transverse momentum distribution of sea quarks is significantly broader than the pT -distribution of valence quarks due to short-range correlations between sea quarks in the nucleon’s light-cone wave function.
Nuclear energy density functional from chiral two-nucleon aaand three-nucleon interactions
Holt, J. W.; Kaiser, N.; Weise, W.
2011-10-01
An improved density-matrix expansion is used to calculate the nuclear energy density functional from chiral two- and three-nucleon interactions. The two-body interaction comprises long-range one- and two-pion exchange contributions and a set of contact terms contributing up to fourth power in momenta. In addition we employ the leading-order chiral three-nucleon interaction with its parameters c E , c D and c 1,3,4 fixed in calculations of nuclear few-body systems. With this input the nuclear energy density functional is derived to first order in the two- and three-nucleon interaction. We find that the strength functions F ?( ?) and F so ( ?) of the surface and spin-orbit terms compare in the relevant density range reasonably with the results of phenomenological Skyrme forces. However, an improved description requires (at least) the treatment of the two-body interaction to second order. This observation is in line with the deficiencies in the nuclear matter equations of state bar E(? ) that remain in the Hartree-Fock approximation with low-momentum two- and three-nucleon interactions.
Photoproduction of nucleon resonances and their structure
Review of available data on radiative decay of non-strange nucleon resonators is presented. The radiative decay amplirude values presented by different authors differ appreciably, which testifies to availability of significant systematic errors. Determination of amplitude of electric quadrupole excitation of ?33(1232) isobar and R11(1440) Roper resonance, arousing great interest due to possibilities of studying features of quark interaction in nucleons and search of hydride (quark-gluon) states, is considered in details. 87 refs.; 5 tabs
Probing nucleon structure on the lattice
The QCDSF/UKQCD collaboration has an ongoing program to calculate nucleon matrix elements with two flavours of dynamical O(a) improved Wilson fermions. Here we present recent results on the electromagnetic form factors, the quark momentum fraction left angle x right angle and the first three moments of the nucleon's spin-averaged and spin-dependent generalised parton distributions, including preliminary results with pion masses as low as 320 MeV. (orig.)
Probing nucleon structure on the lattice
Goeckeler, M. [Regensburg Univ. (Germany). Inst. fuer Theoretische Physik; Haegler, P. [Technische Univ. Muenchen, Garching (Germany). Physik-Department, Inst. fuer Theoretische Physik T39; Horsley, R. [Edinburgh Univ. (GB). School of Physics] (and others)
2006-08-15
The QCDSF/UKQCD collaboration has an ongoing program to calculate nucleon matrix elements with two flavours of dynamical O(a) improved Wilson fermions. Here we present recent results on the electromagnetic form factors, the quark momentum fraction left angle x right angle and the first three moments of the nucleon's spin-averaged and spin-dependent generalised parton distributions, including preliminary results with pion masses as low as 320 MeV. (orig.)
Spin Structure of Nucleon and Equivalence Principle
Teryaev, O. V.(Bogoliubov Laboratory of Theoretical Physics, JINR, 141980, Dubna, Russia)
1999-01-01
The partition of nucleon spin between total angular momenta of quarks and gluons is described by the energy momentum tensor formfactors manifested also in the nucleon scattering by weak classical gravitational field. Natural generalization of equivalence principle is resulting in the identically zero "Anomalous gravitomagnetic moment" being the straightforward analog of its electromagnetic counterpart. This, in turn, means the equal partition of momentum and total angular momentum, anticipate...
This report covers many aspects and some of the singular events which occurred over a two year period (November 1975-November 1977) in the field of nucleonics. Tables (I-IV) include listings of new books, reviews, bibliographies, and conference proceedings. Table III, (the list of conference proceedings) is not as complete as the authors had wished because of the often-experienced long delay time between oral presentation and proceedings publication; therefore, some of the publication dates were not available. By referring to these tables, however, one can find information on almost any facet of nucleonics. According to the authors, their brief written summary emphasizes only the new, interesting, or occasionally, the peculiar aspects of the subject. Discussed are developments in radiation detectors, radiotracer techniques, nuclear archeology, growth in application of activation analysis, decay rate perturbations, and environmental concerns. 213 references
Generalized Parton Distributions and the Spin Structure of the Nucleon
Ji, Xiangdong
2002-01-01
Generalized parton distributions are a new type of hadronic observables which has recently stimulated great interest among theorists and experimentalists alike. Introduced to delineate the spin structure of the nucleon, the orbital angular momentum of quarks in particular, the new distributions contain vast information about the internal structure of the nucleon, with the usual electromagnetic form factors and Feynman parton distributions as their special limits. While new perturbative QCD pr...
Study of excited nucleons and their structure
Burkert, Volker D. [JLAB, Newport News, VA (United States)
2014-01-01
Recent advances in the study of excited nucleons are discussed. Much of the progress has been achieved due to the availability of high precision meson production data in the photoproduction and electroproduction sectors, the development of multi-channel partial wave analysis techniques, and advances in Lattice QCD with predictions of the full excitation spectrum.
Structure Functions from Chiral Soliton Models
Weigel, H.(Physics Department, Stellenbosch University, Matieland 7602, South Africa); Gamberg, L.(Department of Physics, Penn State University-Berks, Reading, PA, 19610, U.S.A.); Reinhardt, H.
1997-01-01
We study nucleon structure functions within the bosonized Nambu-Jona-Lasinio (NJL) model where the nucleon emerges as a chiral soliton. We discuss the model predictions on the Gottfried sum rule for electron-nucleon scattering. A comparison with a low-scale parametrization shows that the model reproduces the gross features of the empirical structure functions. We also compute the leading twist contributions of the polarized structure functions $g_{1}(x)$ and $g_{2}(x)$ in this model. We compa...
Experimental study of the nucleon spin structure
After introducing the theoretical framework, which includes DIS, the Quark Parton Model (QPM) and QCD, we describe the implementation of the experiment. The SMC uses a beam of 190 GeV naturally polarized muons, scattering off nucleons in a large cryogenic target containing protons or deuterons that are polarized through Dynamic Nuclear Polarization (DNP). The target material is located in two cells in a row, with opposite polarizations. Every 5 hours the polarizations of both cells are reversed. The target polarization is measured by an NMR system. The polarization of the beam is measured in a polarimeter, located downstream of the main experimental setup. (orig.)
Experimental study of the nucleon spin structure
Litmaath, M.F.
1996-05-07
After introducing the theoretical framework, which includes DIS, the Quark Parton Model (QPM) and QCD, we describe the implementation of the experiment. The SMC uses a beam of 190 GeV naturally polarized muons, scattering off nucleons in a large cryogenic target containing protons or deuterons that are polarized through Dynamic Nuclear Polarization (DNP). The target material is located in two cells in a row, with opposite polarizations. Every 5 hours the polarizations of both cells are reversed. The target polarization is measured by an NMR system. The polarization of the beam is measured in a polarimeter, located downstream of the main experimental setup. (orig.).
Modelling the nucleon wave function from soft and hard processes
Bolz, J
1996-01-01
Current light-cone wave functions for the nucleon are unsatisfactory since they are in conflict with the data of the nucleon's Dirac form factor at large momentum transfer. Therefore, we attempt a determination of a new wave function respecting theoretical ideas on its parameterization and satisfying the following constraints: It should provide a soft Feynman contribution to the proton's form factor in agreement with data; it should be consistent with current parameterizations of the valence quark distribution functions and lastly it should provide an acceptable value for the \\jp \\to N \\bar N decay width. The latter process is calculated within the modified perturbative approach to hard exclusive reactions. A simultaneous fit to the three sets of data leads to a wave function whose x-dependent part, the distribution amplitude, shows the same type of asymmetry as those distribution amplitudes constrained by QCD sum rules. The asymmetry is however much more moderate as in those amplitudes. Our distribution ampl...
The spin structure of the nucleon
The nucleon is a spin 1/2 particle. This spin can be decomposed into the contributions of its constituents: 1/2 equals 1/2*ΔΣ + Δg + Lq + Lg where the first term is the contribution from the spin of the quarks, the second term is the contribution from the spin of the gluons and Lq and Lg are the orbital momentum of the quark and the gluon respectively. The ΔΣ contribution of the spin of quarks can be studied through polarized deep inelastic scattering (DIS). We introduce DIS and the so-called parton model and then turn to the case of polarized DIS in the inclusive and semi-inclusive cases. We also discuss how a third parton distribution, called transversity, appears together with the unpolarized and the longitudinally polarized (or helicity) ones. We show how the longitudinally polarized gluon distribution can be measured. Then we focus on the SMC and COMPASS experiments performed at CERN. SMC confirmed a previous result by showing that the contribution of the spin of the quark to the spin of the nucleon was small. SMC also performed a measurement on the deuterium in order to test, for the first time, the Bjorker sum rules, which is a fundamental prediction of quantum chromodynamics. The COMPASS experiment started collecting data in 2002. Its main objectives are the gluon polarization Δg/g and the so-called transversity. (A.C.)
Spin structure of nucleon in QCD: inclusive and exclusive processes
There are two basically independent ways to describe the nucleon spin structure. One is related to quark and gluon spins and another one to their total angular momenta. The latter spin structure may be studied, in principle, in hard exclusive processes
Generalized Parton Distributions and the Spin Structure of the Nucleon
Ji, X
2002-01-01
Generalized parton distributions are a new type of hadronic observables which has recently stimulated great interest among theorists and experimentalists alike. Introduced to delineate the spin structure of the nucleon, the orbital angular momentum of quarks in particular, the new distributions contain vast information about the internal structure of the nucleon, with the usual electromagnetic form factors and Feynman parton distributions as their special limits. While new perturbative QCD processes, such as deeply virtual Compton scattering and exclusive meson production, have been found to measure the distributions directly in experiments, lattice QCD offers a great promise to provide the first-principle calculations of these interesting observables.
Generalized parton distributions and the spin structure of the nucleon
Ji, Xiangdong
2003-05-01
Generalized parton distributions are a type of hadronic observables which has recently stimulated great interest among theorists and experimentalists alike. Introduced to delineate the spin structure of the nucleon, the orbital angular momentum of quarks in particular, the new distributions contain vast information about the internal structure of the nucleon, with the usual electromagnetic form factors and Feynman parton distributions as their special limits. While new perturbative QCD processes, such as deeply virtual Compton scattering and exclusive meson production, have been found to measure the distributions directly in experiments, lattice QCD offers a great promise to provide the first-principle calculations of these interesting observables.
Generalized parton distributions and the spin structure of the nucleon
Generalized parton distributions are a type of hadronic observables which has recently stimulated great interest among theorists and experimentalists alike. Introduced to delineate the spin structure of the nucleon, the orbital angular momentum of quarks in particular, the new distributions contain vast information about the internal structure of the nucleon, with the usual electromagnetic form factors and Feynman parton distributions as their special limits. While new perturbative QCD processes, such as deeply virtual Compton scattering and exclusive meson production, have been found to measure the distributions directly in experiments, lattice QCD offers a great promise to provide the first-principle calculations of these interesting observables
The spin structure of the nucleon
Le Goff, J.M
2005-02-15
The nucleon is a spin 1/2 particle. This spin can be decomposed into the contributions of its constituents: 1/2 equals 1/2*{delta}{sigma} + {delta}g + L{sub q} + L{sub g} where the first term is the contribution from the spin of the quarks, the second term is the contribution from the spin of the gluons and L{sub q} and L{sub g} are the orbital momentum of the quark and the gluon respectively. The {delta}{sigma} contribution of the spin of quarks can be studied through polarized deep inelastic scattering (DIS). We introduce DIS and the so-called parton model and then turn to the case of polarized DIS in the inclusive and semi-inclusive cases. We also discuss how a third parton distribution, called transversity, appears together with the unpolarized and the longitudinally polarized (or helicity) ones. We show how the longitudinally polarized gluon distribution can be measured. Then we focus on the SMC and COMPASS experiments performed at CERN. SMC confirmed a previous result by showing that the contribution of the spin of the quark to the spin of the nucleon was small. SMC also performed a measurement on the deuterium in order to test, for the first time, the Bjorker sum rules, which is a fundamental prediction of quantum chromodynamics. The COMPASS experiment started collecting data in 2002. Its main objectives are the gluon polarization {delta}g/g and the so-called transversity. (A.C.)
Delineating the polarized and unpolarized partonic structure of the nucleon
Jimenez-Delgado, Pedro [JLAB
2015-03-01
Reports on our latest extractions of parton distribution functions of the nucleon are given. First an overview of the recent JR14 upgrade of our unpolarized PDFs, including NNLO determinations of the strong coupling constant and a discussion of the role of the input scale in parton distribution analysis. In the second part of the talk recent results on the determination of spin-dependent PDFs from the JAM collaboration are reported, including a careful treatment of hadronic and nuclear corrections, as well as reports on the impact of present and future data in our understanding of the spin of the nucleon.
Delineating the polarized and unpolarized partonic structure of the nucleon
Jimenez-Delgado, Pedro [JLAB
2015-03-01
Our latest results on the extraction of parton distribution functions of the nucleon are reported. First an overview of the recent JR14 upgrade of our unpolarized PDFs, including NNLO determinations of the strong coupling constant and a discussion of the role of the input scale in parton distribution analysis. In the second part of the talk recent results on the determination of spin-dependent PDFs from the JAM collaboration are given, including a careful treatment of hadronic and nuclear corrections, as well as results on the impact of present and future data in our understanding of the spin of the nucleon.
The possibility of analyzing the mesonic structure of the nucleon by studying the quasielastic knockout of pions from nucleons is discussed. In the region where the pole approximation is applicable, the cross section for the exclusive electroproduction of a pion on a nucleon can be represented in a form that involves the momentum distribution of pions in the channel p?n+?+ (quasielastic knockout). This distribution is extracted from experimental data and is consistent with the wave function of a bound pion in the nucleon as given by the potential of ?N scattering. The spectroscopic factor Sn?(p) (this is the normalization of the momentum distribution, the number of mesons in a given channel) is estimated. A wide set of accessible, albeit as-yet-unexplored, fundamental features of the nucleon, such as the momentum distributions and spectroscopic factors in various channels (p?B+?, ?+K, etc.), can extend our knowledge about the structure of the nucleon, thereby furnishing information necessary for further development of nonperturbative QCD
Spin structure of the nucleon on the light front
Lorcé, Cédric
2014-01-01
We briefly review the spin structure of the nucleon and show that it is best thought in the light-front formulation. We discuss in particular the longitudinal and transverse spin sum rules, the proper definition of canonical orbital angular momentum and the spin-orbit correlation.
About Anomalous Magnetic Moment and Structure of Nucleon
Kopylov, A V
1999-01-01
The comparison of magnetic moments of neutron and proton enables to outline qualitatively the structure of nucleon by using a model similar to the one suggested by Ida and Kobayashi that "baryons consist of a qq pair (or diquark) and another quark moving around it with orbital angular momentum L"
About Anomalous Magnetic Moment and Structure of Nucleon
Kopylov, A. V.
1999-01-01
The comparison of magnetic moment of neutron and proton enables to outline qualitatively the structure of nucleon by using a model similar to the one suggested by Ida and Kobayashi that "baryons consist of a qq pair (or a diquark) and another quark moving around it with orbital angular momentum L".
Nucleon-nucleon interactions are at the heart of nuclear physics, bridging the gap between QCD and the effective interactions appropriate for the shell model. We discuss the current status of NN data sets, partial-wave analyses, and some of the issues that go into the construction of potential models. Our remarks are illustrated by reference to the Argonne v18 potential, one of a number of new potentials that fit elastic nucleon-nucleon data up to 350 MeV with a Χ2 per datum near 1. We also discuss the related issues of three-nucleon potentials, two-nucleon charge and current operators, and relativistic effects. We give some examples of calculations that can be made using these realistic descriptions of NN interactions. We conclude with some remarks on how our empirical knowledge of NN interactions may help constrain models at the quark level, and hence models of nucleon structure
Studying nucleon structure using an Electron-Ion Collider
Burton, Thomas; EIC Team
2011-04-01
The detailed composition of the spin of the nucleon remains unknown. Numerous experiments over the past two decades have shown that the spin of quarks alone cannot account for more than a third of the nucleon's spin. Proton-proton collisions at RHIC suggest a small gluon polarisation, but uncertainties remain large. An Electron-Ion Collider is proposed as future machine for precision studies of nucleon and nuclear structure. It will allow the study of the spin contribution from gluons and quarks, including their flavour decomposition, in heretofore unprecedented precision, and will access a much wider kinematic space than ever before, in particular extending to the currently unmeasured low Bjorken-x sea. The formalism of generalised parton distributions (GPDs), accessible for example via deeply-virtual Compton scattering, promises to allow study of the role of orbital angular momentum in nucleon spin. Furthermore, GPDs will extend understanding of parton distributions beyond the well-known one-dimensional PDFs, accessing three-dimensional structure via the impact parameter distributions of partons.
Understanding the nucleon structure is currently one of the main challenges encountered in nuclear physics. The present work represents a contribution to the study of the nucleon structure and deals, in particular, with the study of the role of strange quarks in the nucleon. The latter can be investigated by determining the strange quark distribution in the nucleon as well as the contribution of the spins of strange quarks to the nucleon spin. This work first presents a measurement of the nucleon spin performed via Deeply Inelastic Scattering (DIS) of a muon beam off polarized proton and deuterium targets. The result is found to be strongly dependent on the quark fragmentation functions into hadrons (FFs), which define the probability that a quark of a given flavour fragments into a final state hadron. The FFs are poorly known, in particular, the FF of strange quark into kaons, which play an important role in the determination of the nucleon spin. In deep inelastic scattering process, the access to the FFs is provided by the hadron multiplicities which, in turn, define the average number of hadrons produced per DIS event. Pion and kaon multiplicities have been extracted versus different kinematic variables, using DIS data collected by deeply inelastic scattering of a 160 GeV/c muons off a deuterium target. A first Leading Order (LO) extraction of the fragmentation functions has then been performed using the measured pion and kaon multiplicities. (author)
Nucleon and pion distribution functions in the valence region
An experimental and theoretical perspective is provided on the behavior of unpolarized distribution functions for the nucleon and pion on the valence-quark domain, namely, Bjorken x(greater-or-similar sign)0.4. This domain is a key to much of hadron physics; e.g., a hadron is defined by its flavor content and that is a valence-quark property. Furthermore, its accurate parametrization is crucial to the provision of reliable input for large collider experiments. The focus is on experimental extractions of distribution functions via electron and muon inelastic scattering, and from Drell-Yan interactions; and on theoretical treatments that emphasize an explanation of the distribution functions, providing an overview of major contemporary approaches and issues. Valence-quark physics is a compelling subject, which probes at the heart of our understanding of the standard model. There are numerous outstanding and unresolved challenges, which experiment and theory must confront. In connection with experiment, an explanation that an upgraded Jefferson Laboratory facility is well suited to provide new data on the nucleon is provided, while a future electron-ion collider could provide essential new data for the mesons. There is also great potential in using Drell-Yan interactions, at FNAL, CERN, J-PARC, and GSI, to push into the large-x domain for both mesons and nucleons. Furthermore, it is argued that explanation, in contrast to modeling and parametrization, requires a widespread acceptance of the need to adapt theory: to the lessons learnt already from the methods of nonperturbative quantum-field theory and a fuller exploitation of those methods.
In this report a nucleon structure function analysis will be discussed. In CHORUS experiment, lead-scintillator calorimeter was used as active target and in 1998 run a high statistics sample of CC interactions of muon (anti-) neutrinos were collected. This sample was used to extract the structure functions of the nucleons in neutrino interactions. A Monte-Carlo program has been developed to study the efficiencies of the detector and for the proper corrections to be applied to the data. The structure functions, F1, F2, xF3, were extracted using three different kinds of fits. The effects of different systematic dependencies have also been studied. Results have been compared to the earlier experiments, CCFR and CDHSW
On the structure of the nucleon optical potential
The structure of the nucleon generalized optical potential (GOP) is investigated in the framework of Green's function (GF) theory. First an exact relation between its imaginary part and the total reaction cross section is derived. In the second part the GOP is decomposed using a kind of projection formalism which enables to couple in the continuum in successive steps. This is achieved by splitting up the one particle GF into a discrete and a continuous part and by summing up all contributions to the GOP containing a given number n >= 0 continuum propagators. Three expressions are extracted corresponding to different processes involving the scattering of at most two particles in the continuum in intermediate states. The remaining terms are argued to be small. Further support for retaining only the above three terms is given by evaluating the diagonal element of their imaginary part between the exact eigenstates of the GOP. This is shown to be approximately proportional to the sum of the total inelastic, charge exchange, pick-up and knock-out cross sections. The corresponding matrix element of the exact potential is proportional to the total reaction cross section. (orig.)
Nuclear energy density functional from chiral pion-nucleon dynamics
We use a recently improved density-matrix expansion (B. Gebremariam, T. Duguet, S.K. Bogner, nucl-th:0910.4979) to calculate the nuclear energy density functional in chiral perturbation theory. Our calculation treats systematically the effects from 1π-exchange, iterated 1π-exchange, and irreducible 2π-exchange with intermediate Δ-isobar excitations, including Pauli-blocking corrections up to three-loop order. We find that the effective nucleon mass M*(ρ) is identical to the one of Fermi-liquid theory. The strength F∇(ρ) of the (vector ∇ρ)2 surface-term as provided by the pion-exchange dynamics is in good agreement with that of phenomenological Skyrme forces in the density region ρ0/2 0. The spin-orbit coupling strength Fso(ρ) receives contributions from iterated 1π-exchange (of the ''wrong sign'') and from three-nucleon interactions mediated by 2π-exchange with virtual Δ-excitation (of the ''correct sign''). In the region around ρ0/2 ≅0.08 fm-3 where the spin-orbit interaction in nuclei gains most of its weight these two components tend to cancel, thus leaving all room for the short-range spin-orbit interaction. The strength function FJ(ρ) multiplying the squared spin-orbit density vector J2 is also studied.
Feasibility studies for nucleon structure measurements with PANDA
Atomssa, Ermias; Ma, Binsong
2014-11-01
The study of nucleon structure is one of the main physics goals of PANDA to be built at the FAIR accelerator complex. The excellent particle identification performance of the PANDA detector will enable measurements of exclusive channels p¯ p → e+e- and p¯ p → π0 J/ψ → π0e+e- to extract the electromagnetic form factors of protons and π-nucleon Transition Distribution Amplitudes (π-N TDAs). After a brief description of the PANDA apparatus and a method to handle momentum resolution degradation due to Bremsstrahlung, the physics of π-N TDAs is discussed. An estimate for the expected signal to background ratio for p¯ p → π0 J/ψ → π0e+e- that takes into account the main background source is given.
Feasibility studies for nucleon structure measurements with PANDA
Atomssa Ermias
2014-01-01
Full Text Available The study of nucleon structure is one of the main physics goals of PANDA to be built at the FAIR accelerator complex. The excellent particle identification performance of the PANDA detector will enable measurements of exclusive channels p̄ p → e+e− and p̄ p → π0 J/ψ → π0e+e− to extract the electromagnetic form factors of protons and π-nucleon Transition Distribution Amplitudes (π-N TDAs. After a brief description of the PANDA apparatus and a method to handle momentum resolution degradation due to Bremsstrahlung, the physics of π-N TDAs is discussed. An estimate for the expected signal to background ratio for p̄ p → π0 J/ψ → π0e+e− that takes into account the main background source is given.
The triton binding energy and the nd-scattering lengths with account of a quark nucleon structure
A simple model for the nucleon-nucleon interaction is suggested which takes into account the quark nucleon structure. Using this model the triton binding energy and the nd-scattering lengths are calculated
Electromagnetic response functions of few-nucleon systems
Inclusive electromagnetic reactions in few-nucleon systems are studied basing on accurate three- and four-body calculations. The longitudinal 4He(e, e') response function obtained at q ≤ 600 MeV/c completely agrees with experiment. The exact 4He spectral function obtained in a semirealistic potential model is presented, and the accuracy of the quasielastic response calculated with its help is assessed, as well as the accuracy of some simpler approximations for the response. The photodisintegration cross section of 3He obtained with the realistic AV14 NN force plus UrbanaVIII NNN force agrees with experiment. It is shown that this cross section is very sensitive to underlying nuclear dynamics in the Eγ ≅ 100 MeV region. In particular, the NNN nuclear force clearly manifests itself in this region. (author)
Wakamatsu, M.
2014-08-01
It is now widely recognized that a key to unraveling the nonperturbative chiral dynamics of QCD hidden in the deep-inelastic-scattering observables is the flavor structure of sea-quark distributions in the nucleon. We analyze the flavor structure of the nucleon sea in both the unpolarized and longitudinally polarized parton distribution functions within the flavor SU(3) chiral quark-soliton model, which contains only one adjustable parameter, ?ms, the effective mass difference between the strange and nonstrange quarks. Particular attention is paid to a nontrivial correlation between the flavor asymmetry of the unpolarized and longitudinally polarized sea-quark distributions and also to a possible particle-antiparticle asymmetry of the strange-quark distributions in the nucleon. We also investigate the charge-symmetry-violation effects in the parton distribution functions exactly within the same theoretical framework, which is expected to provide us with valuable information on the relative importance of the asymmetry of the strange and antistrange distributions and the charge-symmetry-violation effects in the valence-quark distributions inside the nucleon in the resolution scenario of the so-called NuTeV anomaly in the extraction of the Weinberg angle.
Chen, Lie-Wen; V. Greco; Ko, C. M.; Li, Bao-An
2003-01-01
Using an isospin-dependent transport model, we study isospin effects on two-nucleon correlation functions in heavy-ion collisions induced by neutron-rich nuclei at intermediate energies. We find that these correlation functions are sensitive to the density dependence of nuclear symmetry energy, but not to the incompressibility of symmetric nuclear matter and the medium dependence of nucleon-nucleon cross sections. This sensitivity is mainly due to effects of nuclear symmetry energy on the emi...
European Muon Collaboration; Arneodo, M.; Arvidson, A.; Aubert, J. J.; Badelek, B.; Beaufays, J.; Bee, C. P.; Benchouk, C.; Berghoff, G.; Bird, I. G.; Blum, D.; Böhm, E.; de Bouard, X.; Brasse, F. W.; Braun, H.; Broll, C.; Brown, S. C.; Brück, H.; Calén, H.; Chima, J. S.; Ciborowski, J.; Clifft, R.; Coignet, G.; Combley, F.; Coughlan, J.; d'Agostini, G.; Dahlgren, S.; Derado, I.; Dreyer, T.; Drees, J.; Düren, M.; Eckardt, V.; Edwards, A.; Edwards, M.; Ernst, T.; Eszes, G.; Favier, J.; Ferrero, M. I.; Figiel, J.; Flauger, W.; Foster, J.; Gabathuler, E.; Gajewski, J.; Gamet, R.; Geddes, N.; Grafström, P.; Gustafsson, L.; Haas, J.; Hagberg, E.; Hasert, F. J.; Hayman, P.; Heusse, P.; Jaffre, M.; Jacholkowska, A.; Janata, F.; Jancso, G.; Johnson, A. S.; Kabuss, E. M.; Kellner, G.; Krüger, A.; Krüger, J.; Kullander, S.; Landgraf, U.; Lanske, D.; Loken, J.; Long, K.; Maire, M.; Malecki, P.; Manz, A.; Maselli, S.; Mohr, W.; Montanet, F.; Montgomery, H. E.; Nagy, E.; Nassalski, J.; Norton, P. R.; Oakham, F. G.; Osborne, A. M.; Pascaud, C.; Pawlik, B.; Payre, P.; Peroni, C.; Peschel, H.; Pessard, H.; Pettingale, J.; Pietrzyk, B.; Poensgen, B.; Pötsch, M.; Renton, P.; Ribarics, P.; Rith, K.; Rondio, E.; Sandacz, A.; Scheer, M.; Schlagböhmer, A.; Schiemann, H.; Schmitz, N.; Schneegans, M.; Scholz, M.; Schouten, M.; Schröder, T.; Schultze, K.; Sloan, T.; Stier, H. E.; Studt, M.; Taylor, G. N.; Thenard, J. M.; Thompson, J. C.; de la Torre, A.; Toth, J.; Urban, L.; Urban, L.; Wallucks, W.; Whalley, M.; Wheeler, S.; Williams, W. S. C.; Wimpenny, S. J.; Windmolders, R.; Wolf, G.
1990-03-01
Small angle scattering of 280 GeV positive muons by deuterium, carbon and calcium has been measured at scattering angles down to 2 mrad. The nucleon structure function F2 extracted from deuterium does not show a significant x dependence in the measured range of Q2 and its Q2 dependence is linear in logQ2. For calcium, a depletion of F2 is observed at low x by 30% as compared with the values at x = 0.1 where F2(Ca) and F2 (D) are not significantly different. This depletion is attributed to shadowing. The carbon structure function exhibits a similar, but less pronounced, x dependence. Such behaviour is observed to be independent of Q2. The data are consistent with those obtained from other charged lepton experiments both at similar and higher values of x and Q2 and considerably extend the range of the measurements down to the low values of x to be measured in forthcoming experiments at HERA.
Nucleon Polarizabilities from Deuteron Compton Scattering within a Green's-Function Hybrid Approach
Hildebrandt, R P; Hemmert, T R; Griesshammer, Harald W.; Hemmert, Thomas R.; Hildebrandt, Robert P.
2005-01-01
We examine elastic Compton scattering from the deuteron for photon energies ranging from zero to 100 MeV, using state-of-the-art deuteron wave functions and NN-potentials. Nucleon-nucleon rescattering between emission and absorption of the two photons is treated by Green's functions in order to ensure gauge invariance and the correct Thomson limit. With this Green's-function hybrid approach, we fulfill the low-energy theorem of deuteron Compton scattering and there is no significant dependence on the deuteron wave function used. Concerning the nucleon structure, we use Chiral Effective Field Theory with explicit \\Delta(1232) degrees of freedom within the Small Scale Expansion up to leading-one-loop order. Agreement with available data is good at all energies. Our 2-parameter fit to all elastic $\\gamma d$ data leads to values for the static isoscalar dipole polarizabilities which are in excellent agreement with the isoscalar Baldin sum rule. Taking this value as additional input, we find \\alpha_E^s= (11.3+-0.7...
Using the structure functions F2 measured in E.M.C., we have extracted the following values for the QCD scale parameter Λ, at next to leading order: hydrogen target: Λsub(MS) = 139(+170-100)MeV; iron target: Λsub(MS) = 170(+160-100)MeV we have performed a study of the 1/Q2 effects on the Q2 domain covered by SLAC and E.M.C. We have extracted the ratio R = sigma sub(L)/sigma sub(T) for various chi bins and compared it with other experimental values and theoretical predictions. The mean value = 0+-.15 was found and is compatible with zero
Studies of nucleon resonance structure in exclusive meson electroproduction
Studies of the structure of excited baryons are key factors to the N* program at Jefferson Lab (JLab). Within the first year of data taking with the Hall B CLAS12 detector following the 12 GeV upgrade, a dedicated experiment will aim to extract the N* electrocouplings at high photon virtualities Q2. This experiment will allow exploration of the structure of N* resonances at the highest photon virtualities ever achieved, with a kinematic reach up to Q2 = 12 GeV2. This high-Q2 reach will make it possible to probe the excited nucleon structures at distance scales ranging from where effective degrees of freedom, such as constituent quarks, are dominant through the transition to where nearly massless bare-quark degrees of freedom are relevant. In this document, we present a detailed description of the physics that can be addressed through N* structure studies in exclusive meson electroproduction. The discussion includes recent advances in reaction theory for extracting N* electrocouplings from meson electroproduction off protons, along with Quantum Chromodynamics (QCD)-based approaches to the theoretical interpretation of these fundamental quantities. This program will afford access to the dynamics of the nonperturbative strong interaction responsible for resonance formation, and will be crucial in understanding the nature of confinement and dynamical chiral symmetry breaking in baryons, and how excited nucleons emerge from QCD. (author)
Ab initio coupled-cluster approach to nuclear structure with modern nucleon-nucleon interactions
We perform coupled-cluster calculations for the doubly magic nuclei 4He, 16O, 40,48Ca, for neutron-rich isotopes of oxygen and fluorine, and employ ''bare'' and secondary renormalized nucleon-nucleon interactions. For the nucleon-nucleon interaction from chiral effective field theory at order next-to-next-to-next-to leading order, we find that the coupled-cluster approximation including triples corrections binds nuclei within 0.4 MeV per nucleon compared to data. We employ interactions from a resolution-scale dependent similarity renormalization group transformations and assess the validity of power counting estimates in medium-mass nuclei. We find that the missing contributions from three-nucleon forces are consistent with these estimates. For the unitary correlator model potential, we find a slow convergence with respect to increasing the size of the model space. For the G-matrix approach, we find a weak dependence of ground-state energies on the starting energy combined with a rather slow convergence with respect to increasing model spaces. We also analyze the center-of-mass problem and present a practical and efficient solution.
Polarized lepton-nucleon scattering
Deep inelastic polarized lepton-nucleon scattering is reviewed in three lectures. The first lecture covers the polarized deep inelastic scattering formalism and foundational theoretical work. The second lecture describes the nucleon spin structure function experiments that have been performed up through 1993. The third lecture discusses implication of the results and future experiments aimed at high-precision measurements of the nucleon spin structure functions
Contribution of nucleon-nucleon correlations to the EMC effect
Quark momentum distributions in nuclei are calculated by solving for the nucleon-nucleon scattering in the nucleus a generalized Bethe-Goldstone equation with quark degrees of freedom in a nonrelativistic quark model, including Pauli blocking due to other nucleons and six-quark bags with different radii. The structure functions of a nucleon in /sup 56/Fe and /sup 107/Ag are calculated. The largest part of the EMC effect is explained by binding of the single nucleons. But the short range correlations including six-quark bags give the important contributions to explain details and the A-dependence of the EMC effect
Wiringa, R.B.
1996-12-31
Nucleon-nucleon interactions are at the heart of nuclear physics, bridging the gap between QCD and the effective interactions appropriate for the shell model. We discuss the current status of {ital NN} data sets, partial-wave analyses, and some of the issues that go into the construction of potential models. Our remarks are illustrated by reference to the Argonne {ital v}{sub 18} potential, one of a number of new potentials that fit elastic nucleon-nucleon data up to 350 MeV with a {Chi}{sup 2} per datum near 1. We also discuss the related issues of three-nucleon potentials, two-nucleon charge and current operators, and relativistic effects. We give some examples of calculations that can be made using these realistic descriptions of {ital NN} interactions. We conclude with some remarks on how our empirical knowledge of {ital NN} interactions may help constrain models at the quark level, and hence models of nucleon structure.
Sidewise dispersion relations and the structure of the nucleon vertex
Davidson, R. M.; Poulis, G.I.
1996-01-01
We revisit sidewise dispersion relations as a method to relate the nucleon off-shell form factor to observable quantities, namely the meson-nucleon scattering phase shifts. It is shown how for meson-nucleon scattering a redefinition of the intermediate fields leaves the scattering amplitude invariant, but changes the behavior of the off-shell form factor as expressed through dispersion relations, thus showing representation dependence. We also employ a coupled-channel unitary model to test th...
Nucleon electromagnetic structure studies in the spacelike and timelike regions
The thesis investigates the nucleon structure probed by the electromagnetic interaction. One of the most basic observables, reflecting the electromagnetic structure of the nucleon, are the form factors, which have been studied by means of elastic electron-proton scattering with ever increasing precision for several decades. In the timelike region, corresponding with the proton-antiproton annihilation into a electron-positron pair, the present experimental information is much less accurate. However, in the near future high-precision form factor measurements are planned. About 50 years after the first pioneering measurements of the electromagnetic form factors, polarization experiments stirred up the field since the results were found to be in striking contradiction to the findings of previous form factor investigations from unpolarized measurements. Triggered by the conflicting results, a whole new field studying the influence of two-photon exchange corrections to elastic electron-proton scattering emerged, which appeared as the most likely explanation of the discrepancy. The main part of this thesis deals with theoretical studies of two-photon exchange, which is investigated particularly with regard to form factor measurements in the spacelike as well as in the timelike region. An extraction of the two-photon amplitudes in the spacelike region through a combined analysis using the results of unpolarized cross section measurements and polarization experiments is presented. Furthermore, predictions of the two-photon exchange effects on the e+p/e-p cross section ratio are given for several new experiments, which are currently ongoing. The two-photon exchange corrections are also investigated in the timelike region in the process p anti p → e+e- by means of two factorization approaches. These corrections are found to be smaller than those obtained for the spacelike scattering process. The influence of the two-photon exchange corrections on cross section measurements as well as asymmetries, which allow a direct access of the two-photon exchange contribution, is discussed. Furthermore, one of the factorization approaches is applied for investigating the two-boson exchange effects in parity-violating electron-proton scattering. In the last part of the underlying work, the process p anti p→π0e+e- is analyzed with the aim of determining the form factors in the so-called unphysical, timelike region below the two-nucleon production threshold. For this purpose, a phenomenological model is used, which provides a good description of the available data of the real photoproduction process p anti p→>π0γ.
Nucleon electromagnetic structure studies in the spacelike and timelike regions
Guttmann, Julia
2013-07-23
The thesis investigates the nucleon structure probed by the electromagnetic interaction. One of the most basic observables, reflecting the electromagnetic structure of the nucleon, are the form factors, which have been studied by means of elastic electron-proton scattering with ever increasing precision for several decades. In the timelike region, corresponding with the proton-antiproton annihilation into a electron-positron pair, the present experimental information is much less accurate. However, in the near future high-precision form factor measurements are planned. About 50 years after the first pioneering measurements of the electromagnetic form factors, polarization experiments stirred up the field since the results were found to be in striking contradiction to the findings of previous form factor investigations from unpolarized measurements. Triggered by the conflicting results, a whole new field studying the influence of two-photon exchange corrections to elastic electron-proton scattering emerged, which appeared as the most likely explanation of the discrepancy. The main part of this thesis deals with theoretical studies of two-photon exchange, which is investigated particularly with regard to form factor measurements in the spacelike as well as in the timelike region. An extraction of the two-photon amplitudes in the spacelike region through a combined analysis using the results of unpolarized cross section measurements and polarization experiments is presented. Furthermore, predictions of the two-photon exchange effects on the e{sup +}p/e{sup -}p cross section ratio are given for several new experiments, which are currently ongoing. The two-photon exchange corrections are also investigated in the timelike region in the process p anti p → e{sup +}e{sup -} by means of two factorization approaches. These corrections are found to be smaller than those obtained for the spacelike scattering process. The influence of the two-photon exchange corrections on cross section measurements as well as asymmetries, which allow a direct access of the two-photon exchange contribution, is discussed. Furthermore, one of the factorization approaches is applied for investigating the two-boson exchange effects in parity-violating electron-proton scattering. In the last part of the underlying work, the process p anti p→π{sup 0}e{sup +}e{sup -} is analyzed with the aim of determining the form factors in the so-called unphysical, timelike region below the two-nucleon production threshold. For this purpose, a phenomenological model is used, which provides a good description of the available data of the real photoproduction process p anti p→>π{sup 0}γ.
Correlations and the Dirac Structure of the Nucleon Self-Energy
Schiller, E.; Müther, H
2000-01-01
The Dirac structure of the nucleon self-energy in symmetric nuclear matter as well as neutron matter is derived from a realistic meson exchange model for the nucleon-nucleon (NN) interaction. It is demonstrated that the effects of correlations on the effective NN interaction in the nuclear medium can be parameterized by means of an effective meson exchange. This analysis leads to a very intuitive interpretation of correlation effects and also provides an efficient parametrization of an effect...
Shell-structure influence on the multinucleon transfer in nucleon transfer matrix elements
An analysis of the experimental data on the charge (mass) distributions of products in nuclear reactions with heavy ions [1], dependence of yield of fragments on their isotope numbers and ones of projectile- and target nuclei [2], and cross sections of the formation of evaporation residues at synthesis of new superheavy elements [3] shows that the individual peculiarities (shell structure, N/Z-ratio) of interacting nuclei play decisive role at formation and evolution of dinuclear system. Therefore, the appropriate microscopic model should be used for the theoretical analysis of the above mentioned effects. The main quantities which must be included into model are the realistic scheme of single-particle states, nucleon separation energy, single-particle matrix elements of nucleon transitions in nuclei and nucleon exchange between them caused by influence of the mean-field of partner-nucleus. In this work the nucleon transfer matrix elements were calculated for the Wood-Saxon potential for spherical nucleus. The eigenvalues and wave functions of single-particle states were obtained by numerical solving Schroedinger's equation. The integral estimation of the matrix elements is found by comparing the calculated width of the charge distributions of the reaction products with the experimental data. In the early paper [4], the same matrix elements were calculated analytically using an approximation for wave functions: authors have used wave functions of the spherical potential well. The numerical values of squares of proton transfer matrix elements found in this work are nearly in coincidence with that presented in [4]. There is a difference between curves of dependencies of the matrix elements under discussion on the relative distance between centres of nuclei when this distance is smaller than sum of nuclei radii. (author)
Nonequilibrium distribution functions of nucleons in relativistic nucleus-nucleus collisions
D. Anchishkin
2013-03-01
Full Text Available The collision smearing of the nucleon momenta about their initial values during relativistic nucleus-nucleus collisions is investigated. To a certain degree, our model belongs to the transport type, and we investigate the evolution of the nucleon system created at a nucleus-nucleus collision. However, we parameterize this development by the number of collisions of every particle during evolution rather than by the time variable. It is assumed that the group of nucleons which leave the system after the same number of collisions can be joined in a particular statistical ensemble. The nucleon nonequilibrium distribution functions are derived which depend on a certain number of collisions of a nucleon before a freeze-out.
Studies of Nucleon Resonance Structure in Exclusive Meson Electroproduction
Aznauryan, I G; Braun, V; Brodsky, S J; Burkert, V D; Chang, L; Chen, Ch; El-Bennich, B; Clot, I C; Cole, P L; Edwards, R G; Fedotov, G V; Giannini, M M; Gothe, R W; Lin, Huey-Wen; Kroll, P; Lee, T -S H; Melnitchouk, W; Mokeev, V I; Pea, M T; Ramalho, G; Roberts, C D; Santopinto, E; de Teramond, G F; Tsushima, K; Wilson, D J
2013-01-01
Studies of the structure of excited baryons are key to the N* program at Jefferson Lab. Within the first year of data taking with the Hall B CLAS12 detector following the 12 GeV upgrade, a dedicated experiment will aim to extract the N* electrocouplings at high photon virtualities Q2. This experiment will allow exploration of the structure of N* resonances at the highest photon virtualities ever yet achieved, with a kinematic reach up to Q2 = 12 GeV2. This high-Q2 reach will make it possible to probe the excited nucleon structures at distance scales ranging from where effective degrees of freedom, such as constituent quarks, are dominant through the transition to where nearly massless bare-quark degrees of freedom are relevant. In this document, we present a detailed description of the physics that can be addressed through N* structure studies in exclusive meson electroproduction. The discussion includes recent advances in reaction theory for extracting N* electrocouplings from meson electroproduction off pro...
Szczurek, A
1999-01-01
The experimental information on nucleon production in lepton deep inelastic scattering (DIS) is rather scarce. Recently there is a growing interest in understanding the mechanism of the production of baryons in DIS, stimulated by recent results on leading protons and neutrons from electron-proton scattering at HERA. I review on different peripheral mechanisms of nucleon (proton or neutron) production in lepton DIS and discuss their role in understanding the spectra of nucleons for both fixed target and collider experiments. In DIS ep to e'Xh, the QCD hardness scale gradually diminishes from the hard scale, Q/sup 2/, in the virtual photon (current) fragmentation region to the soft, hadronic, scale in the proton (target) fragmentation region. This suggests a similarity of the inclusive spectra of leading protons and neutrons, h=p, n, in high energy hadron-proton collisions and in lepton DIS at small Bjorken-x. The semi-inclusive cross section for production of slow protons in charged-current deep inelastic (ant...
Nucleon structure function at small χ
This is a status report on the behaviour of deeply inelastic scattering in the low x region, where a new physics to be expected. It is bound to be theoretical review, since there is no data available at truely small values of x, say x -3. New data from HERA are anticipated and I am viewing on this talk as summary of the theoretical situation in the region of small x, as is just before this new area of physics will be studied experimentally. This is an extended version of the talk which was presented at EP-HEP 91 Conference. (orig.)
Parton sum rules and nucleon structure functions
Ma, B Q
1996-01-01
A brief summary on the Wigner rotation effect in the understanding of the proton spin ``crisis" related with the Ellis-Jaffe sum rule violation, and on the proton-neutron isospin symmetry breaking explanation of the Gottfried sum rule violation. The proton spin could be fully provided by the spin sum of quarks if one considers the Wigner rotation effect in the measured quark helicity distributions.
Relationship between Feshbach's and Green's function theories of the nucleon-nucleus mean field
We clarify the relationship and difference between theories of the optical-model potential which had previously been developed in the framework of Feshbach's projection operator approach to nuclear reactions and of Green's function theory, respectively. For definiteness, we consider the nucleon-nucleus system but all results can readily be adapted to the atomic case. The effects of antisymmetrization are properly taken into account. It is shown that one can develop along closely parallel lines the theories of open-quotes holeclose quotes and open-quotes particleclose quotes mean fields. The open-quotes holeclose quotes one-body Hamiltonians describe the single-particle properties of the system formed when one nucleon is taken away from the target ground state, for instance in knockout of pickup processes. The particle one-body Hamiltonians are associated with the system formed when one nucleon is elastically scattered from the ground state, or is added to it by means of stripping reactions. An infinite number of particle, as well as of hole, Hamiltonians are constructed which all yield exactly the same single-particle wave functions. Many open-quotes equivalentclose quotes one-body Hamiltonians can coexist because these operators have a complicated structure: they are nonlocal, complex, and energy-dependent. They do not have the same analytic properties in the complex energy plane. Their real and imaginary parts fulfill dispersion relations which may be different. It is shown that hole and particle Hamiltonians can also be constructed by decomposing any vector of the Hilbert space into two parts which are not orthogonal to one another, in contrast to Feshbach's original theory; one interest of this procedure is that the construction and properties of the corresponding hole Hamiltonian can be justified in a mathematically rigorous way. We exhibit the relationship between the hole and particle Hamiltonians and the open-quotes mass operator.close quotes
Nuclear Effects in Neutrino Structure Functions
Kulagin, S A
2007-01-01
We discuss calculation of nuclear corrections to the structure functions for the deep-inelastic scattering of muon and (anti)neutrino. Our approach includes a QCD description of the nucleon structure functions as well as the treatment of Fermi motion and nuclear binding, off-shell correction to bound nucleon structure functions, nuclear pion excess and nuclear shadowing. We emphasize the dependence of nuclear effects on the type and C-parity of (anti)neutrino structure functions. We also examine the interplay between different nuclear effects in the Adler and the Gross-Llewellyn-Smith sum rules for nuclei.
Nuclear Effects in Neutrino Structure Functions
We discuss calculation of nuclear corrections to the structure functions for the deep-inelastic scattering of muon and (anti)neutrino. Our approach includes a QCD description of the nucleon structure functions as well as the treatment of Fermi motion and nuclear binding, off-shell correction to bound nucleon structure functions, nuclear pion excess and nuclear shadowing. We emphasize the dependence of nuclear effects on the type and C parity of (anti)neutrino structure functions. We also examine the interplay between different nuclear effects in the Adler and the Gross-Llewellyn-Smith sum rules for nuclei
The physical importance of nucleon-nucleon diffraction and the main differences with well understood nucleon nucleus diffraction is discused. In the theoretical description of nucleon-nucleon diffraction in terms of the eikonal model, the hypothesis of factorization is shown to be in contradiction with the energy dependence of the impact parameter profile in proton-proton scattering at CERN - ISR. This dependence is highly non-uniform in impact parameter, giving rise to a pronounced peripheral increase with energy of the inelastic overlap function. Two experimental findings in inelastic diffraction indicate the existence of a deep relation of this process with the peripheral increase of the profile function. The first refers to the clear-cut proof that inelastic diffraction is peripheral in impact parameter space, in coherent production on deuteron. The second is the analysis of the integrated cross sections for inelastic diffraction, which leads to the conclusion that most of the total cross section increase in the ISR energy range comes from this process. It is then clear that the eikonal model should be modified in order to include inelastic diffraction. A recent trial in this direction by Miettinen and Thomas shows the existence of a substantial difference between the matter and the charge distribution inside the proton. Their results favours a description of the proton in terms of the string model. (Author)
Nucleon Resonance Structure Studies Via Exclusive KY Electroproduction
Carman, Daniel S
2016-01-01
Studying the structure of excited nucleon states employing the electroproduction of exclusive reactions is an important avenue for exploring the nature of the non-perturbative strong interaction. The electrocouplings of $N^*$ states in the mass range below 1.8~GeV have been determined from analyses of CLAS $\\pi N$, $\\eta N$, and $\\pi \\pi N$ data. This work has made it clear that consistent results from independent analyses of several exclusive channels with different couplings and non-resonant backgrounds but the same $N^*$ electro-excitation amplitudes, is essential to have confidence in the extracted results. In terms of hadronic coupling, many high-lying $N^*$ states preferentially decay through the $\\pi \\pi N$ channel instead of $\\pi N$. Data from the $KY$ channels will therefore be critical to provide an independent analysis to compare the extracted electrocouplings for the high-lying $N^*$ states against those determined from the $\\pi N$ and $\\pi \\pi N$ channels. A program to study excited $N^*$ state s...
We have performed a separation of the longitudinal and transverse structure functions for the 40Ca(e,e'p)39K reaction in the quasi-elastic region. Their ratio (L/T) is found reduced by about 30% from the Distorted Wave Impulse Approximation prediction. This result is compatible with the quenching of the Coulomb Sum-Rule observed in the inclusive ee' reaction. Since a possible swelling of the nucleon in nuclear matter has been advocated to explain this quenching, we have also measured the q-dependence of both structure functions to test this hypothesis. The results are not in favour of a large modification of the electromagnetic radius of the nucleon. From the transverse component, an upper limit of 5% can be derived for a possible increase of the radius
Structure of dipole nucleon collective movement in atomic nuclei
Atomic nuclei have different forms of dipole collective movement of nucleons. Here is a very known example - giant (isovector) dipole resonance that were predicted more than 40 years. Another form of dipole collective mode appears from valence nucleons. In Bose particle theory such a collective mode is described by means of s, p, d Bose particles. These Bose particles can be considered duplex nucleons images in the condition jπ=0'+, 1-, 2+. If conditions with jπ=0+ and jπ=2+, are generated by means of identical nucleon coupling then conditions with jπ=1- can occur by neutron/proton coupling. In the field of heavy nuclei valence neutrons and protons are at close by different parity energies conditions and strong neutron-proton interaction of these nucleon pairs in excited state generates collective movement of dipole nature. The fact that there is p-Bose particle freedom in atomic nuclei is confirmed by the following. In 210Bi (where there is one proton and neutron over 208Pb magic shell) 1- condition is basic and assigned
The controversial role of strangeness in the spin structure of the nucleon
Although the strangeness content of the nucleon is small, it has played a major role in provoking puzzles and controversies in our understanding of the internal structure of the nucleon, particularly as concerns the spin structure. We recall the role of the strange polarization in precipitating the ''spin crisis in the parton model'' and discuss our present knowledge of the shape and sign of ?s(x). (orig.)
Nucleon structure with pion clouds in a flux-tube quark model
Nucleon structure with pion clouds is studied in the framework of a flux-tube quark model. The meson clouds are produced by breaking flux tubes in the nucleon; then a baryon is described by three valence quarks connected by color fields and other configurations including sea quarks. These sea quarks (or meson clouds) generate baryon decay widths and shift their masses; therefore, the hadron spectroscopy in constitutent-quark models should be investigated again by including these mass shifts. In this flux-tube model, the Yukawa potential is explained by a piece of the flux tube breaking off from a nucleon and attaching itself to the other
Nuclear energy density functional from chiral two- and three-nucleon interactions
Holt, J W; Weise, W
2011-01-01
An improved density-matrix expansion is used to calculate the nuclear energy density functional from chiral two- and three-nucleon interactions. The two-body interaction comprises long-range one- and two-pion exchange contributions and a set of contact terms contributing up to fourth power in momenta. In addition we employ the leading order chiral three-nucleon interaction with its parameters $c_E, c_D$ and $c_{1,3,4}$ fixed in calculations of nuclear few-body systems. With this input the nuclear energy density functional is derived to first order in the two- and three-nucleon interaction. We find that the strength functions $F_\
Nucleon structure from 2+1f dynamical DWF lattice QCD at nearly physical pion mass
Ohta, Shigemi
2011-01-01
Current status of nucleon structure calculations with joint RBC and UKQCD 2+1-flavor dynamical domain-wall fermions (DWF) lattice QCD is reported: Two ensembles with pion mass of about (m_\\pi=170) MeV and 250 MeV are used. The lattice cutoff is set at about 1.4 GeV, allowing a large spatial volume of about (L=4.6) fm across while maintaining a sufficiently small residual breaking of chiral symmetry with the dislocation-suppressing-determinant-ratio (DSDR) gauge action. We calculate all the isovector form factors and some low moments of isovector structure functions. We confirm the finite-size effect in isovector axialvector-current form factors, in particular the deficit in the axial charge and its scaling in terms of (m_\\pi L), that we reported from our earlier calculation at heavier pion masses.
Quark-parton structure functions of nuclei
The previously available and new experimental data are used to discuss the properties of the structure functions of nuclei as independent (irreducible to one-nucleon) objects of hadron physics. The basic data have been obtained by the Stavinsky group in experiments on limiting fragmentation of more than 20 nuclei from 7Li to 238U. The discovered properties of the quark-parton structure functions give evidence for the existence in nuclei of multiquark configurations which essentially differ from those present in both free nucleons and two-, three- and more nucleon systems. Experiments on deep inelastic scattering of leptons on nuclei performed by the CERN-Dubna NA-4 Collaboration, the European Muon Collaboration and at SLAC confirm the conclusions about the structure functions of nuclei drawn from nuclear limiting fragmentation studies
Shell structure and few-nucleon removal in intranuclear cascade
It is well known that intranuclear-cascade models generally overestimate the cross sections for one-proton removal from heavy, stable nuclei by a high-energy proton beam, but they yield reasonable predictions for one-neutron removal from the same nuclei and for one- nucleon removal from light targets. We use simple shell-model calculations to investigate the reasons of this deficiency. We find that a correct description of the neutron skin and of the energy density in the nuclear surface is crucial for the aforementioned observables. Neither ingredient is sufficient if taken separately
Shell structure and few-nucleon removal in intranuclear cascade
Mancusi, Davide; Carbonell, Jaume; Cugnon, Joseph; David, Jean-Christophe; Leray, Sylvie
2014-01-01
It is well known that intranuclear-cascade models generally overestimate the cross sections for one-proton removal from heavy, stable nuclei by a high-energy proton beam, but they yield reasonable predictions for one-neutron removal from the same nuclei and for one-nucleon removal from light targets. We use simple shell-model calculations to investigate the reasons of this deficiency. We find that a correct description of the neutron skin and of the energy density in the nuclear surface is crucial for the aforementioned observables. Neither ingredient is sufficient if taken separately.
Recent results on the nucleon resonance spectrum and structure from the CLAS detector
Mokeev, Viktor I. [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Aznauryan, Inna G. [Skobeltsyn Nuclear Physics Institute and Physics Department at Moscow State University, Moscow, Russia; Burkert, Volker D. [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Gothe, Ralf W. [Univ. of South Carolina, Columbia, SC (United States)
2016-03-01
The CLAS detector at Jefferson Lab has provided the dominant part of all available worldwide data on exclusive meson electroproduction off protons in the resonance region. New results on the $\\gamma_{v}pN^*$ transition amplitudes (electrocouplings) are available from analyses of the CLAS data and will be presented. Their impact on understanding of hadron structure will be discussed emphasizing the credible access to the dressed quark mass function that has been achieved for the first time by a combined analysis of the experimental results on the electromagnetic nucleon elastic and $N \\rightarrow N^*$ transition form factors. We will also discuss further convincing evidences for a new baryon state $N^{\\, '}(1720)3/2^+$ found in a combined analysis of charged double pion photo- and electroproduction cross sections off the protons.
Recent results on the nucleon resonance spectrum and structure from the CLAS detector
Mokeev, V. I.; Aznauryan, I. G.; Burkert, V. D.; Gothe, R. W.
2016-03-01
The CLAS detector at Jefferson Lab has provided the dominant part of all available worldwide data on exclusive meson electroproduction off protons in the resonance region. New results on the γυpN* transition amplitudes (electrocouplings) are available from analyses of the CLAS data and will be presented. Their impact on understanding of hadron structure will be discussed emphasizing the credible access to the dressed quark mass function that has been achieved for the first time by a combined analysis of the experimental results on the electromagnetic nucleon elastic and N → N* transition form factors. We will also discuss further convincing evidences for a new baryon state N' (1720)3/2+ found in a combined analysis of charged double pion photo- and electroproduction cross sections off the protons.
Recent results on the nucleon resonance spectrum and structure from the CLAS detector
Mokeev V. I.
2016-01-01
Full Text Available The CLAS detector at Jefferson Lab has provided the dominant part of all available worldwide data on exclusive meson electroproduction off protons in the resonance region. New results on the γυpN* transition amplitudes (electrocouplings are available from analyses of the CLAS data and will be presented. Their impact on understanding of hadron structure will be discussed emphasizing the credible access to the dressed quark mass function that has been achieved for the first time by a combined analysis of the experimental results on the electromagnetic nucleon elastic and N → N* transition form factors. We will also discuss further convincing evidences for a new baryon state N′ (17203/2+ found in a combined analysis of charged double pion photo- and electroproduction cross sections off the protons.
Nucleon and hadron structure changes in the nuclear medium and the impact on observables
Saito, K.; Tsushima, K.; Thomas, A. W.
2007-01-01
We study the effect of hadron structure changes in a nuclear medium using the quark-meson coupling (QMC) model. The QMC model is based on a mean field description of non-overlapping nucleon (or baryon) bags bound by the self-consistent exchange of scalar and vector mesons in the isoscalar and isovector channels. The model is extended to investigate the properties of finite nuclei, in which, using the Born-Oppenheimer approximation to describe the interacting quark-meson system, one can derive the effective equation of motion for the nucleon (or baryon), as well as the self-consistent equations for the meson mean fields. In conventional nuclear physics, the Skyrme effective forces are very popular, but, there is no satisfactory interpretation of the parameters appearing in the Skyrme forces. Comparing a many-body Hamiltonian generated by the QMC model in the zero-range limit with that of the Skyrme effective forces, it is possible to obtain a remarkable agreement between the Skyrme force and the QMC effective interaction. One can also investigate the relationship between the QMC model and Quantum Hadrodynamics, by carrying out a re-definition of the scalar field in matter. Furthermore, by using naive dimensional analysis, it is possible to see that the QMC model can provide remarkably natural coupling constants and hence the model itself is regarded as a natural effective field theory for nuclei. The model is first applied to nuclear matter, where the coupling constants are determined so as to produce the saturation condition at normal nuclear matter density. We find a new, simple scaling relation for the changes of hadron masses in a nuclear medium, which can be described in terms of the number of light quarks in a hadron and the value of the scalar mean field in matter. Once the coupling constants are fixed, the model can be applied to various finite nuclei, including strange and exotic hypernuclei. In this article, we discuss in detail the properties of hypernuclei and meson-nucleus deeply bound states. It is also of great interest that the QMC model predicts a variation of the nucleon form factors in nuclear matter, which will certainly affect the analysis of electron scattering off nuclei, including polarization transfer experiments. Recent experimental analysis of data taken at Jefferson Laboratory (JLab) and MAMI does indeed seem to support such a variation of nucleon form factors in nuclei. The change of nucleon structure in a nuclear medium is also expected to modify nuclear structure functions (the nuclear EMC effect), which are measured by scattering with high energy charged leptons and/or neutrinos. We study such possibilities, including consideration of the empirically observed, Bloom-Gilman (quark-hadron) duality. We also study hadronic reactions in a nuclear medium, namely, subthreshold kaon production in heavy ion collisions, D and Dbar meson production in antiproton-nucleus collisions, and J/Ψ suppression. In particular, the modification of the D and Dbar meson properties in a nuclear medium derived from the QMC model can lead to a large J/Ψ absorption cross section, which is required to explain the observed J/Ψ suppression in the microscopic hadronic comover dissociation scenario, without assuming the formation of a QGP phase. The present investigation indicates that the traditional nuclear/hadronic physics approach may have its limitations. It further suggests the need for the study of alternative approaches which include subhadronic degrees of freedom, even at normal nuclear matter density.
Polarized Structure Functions and Spin Physics
Stsslein, U
2002-01-01
Recent progress in the field of spin physics of high energy particle interactions is reviewed with particular emphasis on the spin structure functions as measured in polarized deep inelastic lepton-nucleon scattering (DIS). New measurements are presented to obtain more direct information on the composition of the nucleon angular momentum, with results from semi-inclusive DIS accessing flavour-separated parton distribution functions (PDF) and with first data from hard exclusive reactions which may be interpreted in terms of recently developed generalizations of parton distribution functions (GPD). Finally, experimental prospects are outlined which will lead to a further development of the virtues of QCD phenomenology of the spin structure of the nucleon.
An overview of recent nucleon spin structure measurements at Jefferson Lab
Allada, Kalyan [Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States); Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
2016-02-01
Jefferson Lab have made significant contributions to improve our knowledge of the longitudinal spin structure by measuring polarized structure functions, g1 and g2, down to Q2 = 0.02 GeV2. The low Q2 data is especially useful in testing the Chiral Perturbation theory (cPT) calculations. The spin-dependent sum rules and the spin polarizabilities, constructed from the moments of g1 and g2, provide an important tool to study the longitudinal spin structure. We will present an overview of the experimental program to measure these structure functions at Jefferson Lab, and present some recent results on the neutron polarizabilities, proton g1 at low Q2, and proton and neutron d2 measurement. In addition to this, we will discuss the transverse spin structure of the nucleon which can be accessed using chiral-odd transversity distribution (h1), and show some results from measurements done on polarized 3He target in Hall A.
Studies of the nucleon structure in back-to-back SIDIS
Avakian, Harut [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
2016-03-01
The Deep Inelastic Scattering (DIS) proved to be a great tool in testing of the theory of strong interactions, which was a major focus in last decades. Semi-Inclusive DIS (SIDIS), with detection of an additional hadron allowed first studies of 3D structure of the nucleon, moving the main focus from testing the QCD to understanding of strong interactions and quark gluon dynamics to address a number of puzzles accumulated in recent years. Detection of two hadrons in SIDIS, which is even more complicated, provides access to details of quark gluon interactions inaccessible in single-hadron SIDIS, providing a new avenue to study the complex nucleon structure. Large acceptance of the Electron Ion Collider, allowing detection of two hadrons, produced back-to-back in the current and target fragmentation regions, combined with clear separation of two regions, would provide a unique possibility to study the nucleon structure in target fragmentation region, and correlations of target and current fragmentation regions.
We performed a self-consistent calculation of the nuclear matter properties within the Green's function scheme. Essential is the self-energy Σ(p;epsilon) (effective single-particle potential or mass operator), which determines the properties of the system. Necessary for the calculation of the effective single-particle potential is the knowledge of the scattering matrix (T-matrix) in matter, which plays in the calculation the role of an effective two-body potential. Our calculations were performed for the 'phenomenological' hardcore potential of Hamada-Johnston, the Reid-soft-core potential and the 'realistic' Paris-Nucleon-Nucleon potential. A binding energy of -5.88 MeV per nucleon was obtained. For the Reid-soft-core potential and the Paris potential we found -11 MeV and -12.2 MeV respectively. (orig./HSI)
Evolution of the nucleon structure in light nuclei
The evolution of the EMC effect as a function of atomic mass A is considered for the first time for the lightest nuclei, D, 3He and , 4He, with an approach based on the Bethe-Salpeter formalism. We show that the pattern of the oscillation of the ratio rA(x)=F2A/F2N(D) with respect to the line rA(x)=1 varies with A, unlike the pattern for nuclei with masses A>4, where only the amplitude of the oscillation changes. It is found that the shape of the structure function distortions, which is typical for metals, is being reached in 3He
The surprising answer to this question Is nucleon deformed? is : Yes. The evidence comes from a study of the quark model of the single nucleon and when it is found in a nucleus. It turns out that many of the long standing problems of the Naive Quark Model are taken care of if the nucleon is assumed to be deformed. Only one value of the parameter PD ?1/4 (which specifies deformation) fits gA (the axial vector coupling constant) for all the semileptonic decay of baryons, the F/D ratio, the pion-nucleon-delta coupling constant fsub(?N?), the double delta coupling constant1 fsub(???), the Ml transition moment ??N and g1p the spin structure function of proton2. All this gives strong hint that both neutron and proton are deformed. It is important to look for further signatures of this deformation. When this deformed nucleon finds itself in a nuclear medium its deformation decreases. So much that in a heavy nucleus the nucleons are actually spherical. We look into the Gamow-Teller strengths, magnetic moments and magnetic transition strengths in nuclei to study this property. (author). 15 refs
Short-Range Nucleon-Nucleon Correlations
Arrington, J; Rosner, G; Sargsian, M
2011-01-01
The strong interaction of nucleons at short distances leads to a high-momentum component to the nuclear wave function, associated with short-range correlations between nucleons. These short-range, high-momentum structures in nuclei are one of the least well understood aspects of nuclear matter, relating to strength outside of the typical mean-field approaches to calculating the structure of nuclei. While it is difficult to study these short-range components, significant progress has been made over the last decade in determining how to cleanly isolate short-range correlations in nuclei. We have moved from asking if such structures exist, to mapping out their strength in nuclei and studying their microscopic structure. A combination of several different measurements, made possible by high-luminosity and high-energy accelerators, coupled with an improved understanding of the reaction mechanism issues involved in studying these structures, has led to significant progress, and provided significant new information ...
Chen, Lie-Wen; Greco, Vincenzo(Department of Physics and Astronomy, University of Catania, Via S. Sofia 64, Catania, 1-95125, Italy); Ko, Che Ming; Li, Bao-An
2002-01-01
Using an isospin-dependent transport model, we study the effects of nuclear symmetry energy on two-nucleon correlation functions in heavy ion collisions induced by neutron-rich nuclei. We find that the density dependence of the nuclear symmetry energy affects significantly the nucleon emission times in these collisions, leading to larger values of two-nucleon correlation functions for a symmetry energy that has a stronger density dependence. Two-nucleon correlation functions are thus useful t...
Study of two-nucleon wave functions in 3He
The 3He(p,2p)pn reaction has been studied in a quasi-free scattering arrangement characterized by (anti) p(recoil) = 0 and various excitation or total energies E(recoil) of the unobserved p-n pair. Data were obtained at 250 and 400 MeV at symmetric and asymmetric pairs of angles. The 3He spectral function deduced in the framework of the plane wave impulse approximation is compared to the predictions of Faddeev and variational calculations. Comparisons are also made with p-n relative motion momentum distributions as the overlap between plane waves for the p-n pair and Irving, Irving-Gunn and Khanna wave functions for 3He
Effect of nucleon and hadron structure changes in-medium and its impact on observables
K. Saito; K. Tsushima; A.W. Thomas
2005-07-05
We study the effect of hadron structure changes in a nuclear medium using the quark-meson coupling (QMC) model. The QMC model is based on a mean field description of non-overlapping nucleon (or baryon) bags bound by the self-consistent exchange of scalar and vector mesons in the isoscalar and isovector channels. The model is extended to investigate the properties of finite nuclei, in which, using the Born-Oppenheimer approximation to describe the interacting quark-meson system, one can derive the effective equation of motion for the nucleon (or baryon), as well as the self-consistent equations for the meson mean fields.
Exploring the nucleon structure through GPDs and TDAs in hard exclusive processes
Pire, B; Szymanowski, L; Wagner, J
2011-01-01
Generalized Parton Distributions (GPDs) offer a new way to access the quark and gluon nucleon structure. We review recent progress in this domain, emphasizing the need to supplement the experimental study of deeply virtual Compton scattering by its crossed version, timelike Compton scattering. We also describe the extension of the GPD concept to three quark operators and the relevance of their nucleon to meson matrix elements, namely the transition distribution amplitudes (TDAs) which factorize in backward meson electroproduction and related processes. We discuss the main properties of the TDAs. \\
Nucleon structure in the chiral regime with domain wall fermions on an improved staggered sea
Moments of unpolarized, helicity, and transversity distributions, electromagnetic form factors, and generalized form factors of the nucleon are presented from a preliminary analysis of lattice results using pion masses down to 359 MeV. The twist two matrix elements are calculated using a mixed action of domain wall valence quarks and asqtad staggered sea quarks and are renormalized perturbatively. Several observables are extrapolated to the physical limit using chiral perturbation theory. Results are compared with experimental moments of quark distributions and electromagnetic form factors and phenomenologically determined generalized form factors, and the implications on the transverse structure and spin content of the nucleon are discussed. (orig.)
Nucleon structure from Lattice QCD using a nearly physical pion mass
We report the first Lattice QCD calculation using the almost physical pion mass m?=149 MeV that agrees with experiment for four fundamental isovector observables characterizing the gross structure of the nucleon: the Dirac and Pauli radii, the magnetic moment, and the quark momentum fraction. The key to this success is the combination of using a nearly physical pion mass and excluding the contributions of excited states. An analogous calculation of the nucleon axial charge governing beta decay has inconsistencies indicating a source of bias at low pion masses not present for the other observables and yields a result that disagrees with experiment
Initial nucleon structure results with chiral quarks at the physical point
Syritsyn, S; Engelhardt, M; Green, J; Izubuchi, T; Jung, C; Krieg, S; Lin, M; Meinel, S; Negele, J; Ohta, S; Pochinsky, A; Shintani, E
2014-01-01
We report initial nucleon structure results computed on lattices with 2+1 dynamical M\\"obius domain wall fermions at the physical point generated by the RBC and UKQCD collaborations. At this stage, we evaluate only connected quark contributions. In particular, we discuss the nucleon vector and axial-vector form factors, nucleon axial charge and the isovector quark momentum fraction. From currently available statistics, we estimate the stochastic accuracy of the determination of $g_A$ and $_{u-d}$ to be around 10%, and we expect to reduce that to 5% within the next year. To reduce the computational cost of our calculations, we extensively use acceleration techniques such as low-eigenmode deflation and all-mode-averaging (AMA). We present a method for choosing optimal AMA parameters.
Low energy structure of the nucleon from chiral effective field theory
Alarcón Jose Manuel
2014-01-01
Full Text Available We present some updated results regarding the scalar and electromagnetic structure of the nucleon obtained by the relativistic formulation of chiral effective field theory with baryons. We compare them with previous determinations available in the literature, and show their relevance for searches of physics beyond the standard model in the low energy frontier.
Higher Twists in the Pion Structure Function
We calculate QCD moments of the pion structure function using Drell-Yan data on the quark distributions in the pion and a phenomenological model for the resonance region. The extracted higher twist corrections are found to be larger than those for the nucleon, contributing around 50% of the lowest moment at Q2 = 1 GeV2
Isovector part of nuclear energy density functional from chiral two- and three-nucleon forces
Kaiser, N.
2012-03-01
A recent calculation of the nuclear energy density functional from chiral two- and three-nucleon forces is extended to the isovector terms pertaining to different proton and neutron densities. An improved density-matrix expansion is adapted to the situation of small isospin asymmetries and used to calculate in the Hartree-Fock approximation the density-dependent strength functions associated with the isovector terms. The two-body interaction comprises of long-range multi-pion exchange contributions and a set of contact terms contributing up to fourth power in momenta. In addition, the leading-order chiral three-nucleon interaction is employed with its parameters fixed in computations of nuclear few-body systems. With this input one finds for the asymmetry energy of nuclear matter the value A( ? 0) ? 26.5 MeV, compatible with existing semi-empirical determinations. The strength functions of the isovector surface and spin-orbit coupling terms come out much smaller than those of the analogous isoscalar coupling terms and in the relevant density range one finds agreement with phenomenological Skyrme forces. The specific isospin and density dependences arising from the chiral two- and three-nucleon interactions can be explored and tested in neutron-rich systems.
Isovector part of nuclear energy density functional from chiral two- and three-nucleon forces
Kaiser, N. [Technische Universitaet Muenchen, Physik Department T39, Garching (Germany)
2012-03-15
A recent calculation of the nuclear energy density functional from chiral two- and three-nucleon forces is extended to the isovector terms pertaining to different proton and neutron densities. An improved density-matrix expansion is adapted to the situation of small isospin asymmetries and used to calculate in the Hartree-Fock approximation the density-dependent strength functions associated with the isovector terms. The two-body interaction comprises of long-range multi-pion exchange contributions and a set of contact terms contributing up to fourth power in momenta. In addition, the leading-order chiral three-nucleon interaction is employed with its parameters fixed in computations of nuclear few-body systems. With this input one finds for the asymmetry energy of nuclear matter the value A({rho}{sub 0}) {approx_equal} 26.5 MeV, compatible with existing semi-empirical determinations. The strength functions of the isovector surface and spin-orbit coupling terms come out much smaller than those of the analogous isoscalar coupling terms and in the relevant density range one finds agreement with phenomenological Skyrme forces. The specific isospin and density dependences arising from the chiral two- and three-nucleon interactions can be explored and tested in neutron-rich systems. (orig.)
Can a many-nucleon structure be visible in bremsstrahlung emission during $\\alpha$ decay?
Maydanyuk, Sergei P; Zou, Li-Ping
2015-01-01
We analyze if the nucleon structure of the $\\alpha$ decaying nucleus can be visible in the experimental bremsstrahlung spectra of the emitted photons which accompany such a decay. We develop a new formalism of the bremsstrahlung model taking into account distribution of nucleons in the $\\alpha$ decaying nuclear system. We conclude the following: (1) After inclusion of the nucleon structure into the model the calculated bremsstrahlung spectrum is changed very slowly for a majority of the $\\alpha$ decaying nuclei. However, we have observed that visible changes really exist for the $^{106}{\\rm Te}$ nucleus ($Q_{\\alpha}=4.29$ MeV, $T_{1/2}$=70 mks) even for the energy of the emitted photons up to 1 MeV. This nucleus is a good candidate for future experimental study of this task. (2) Inclusion of the nucleon structure into the model increases the bremsstrahlung probability of the emitted photons. (3) We find the following tendencies for obtaining the nuclei, which have bremsstrahlung spectra more sensitive to the ...
The density matrix expansion (DME) of Negele and Vautherin is a convenient tool to map finite-range physics associated with vacuum two- and three-nucleon interactions into the form of a Skyrme-like energy density functional (EDF) with density-dependent couplings. In this work, we apply the improved formulation of the DME proposed recently in (arXiv:0910.4979) by Gebremariam et al. to the non-local Fock energy obtained from chiral effective field theory (EFT) two-nucleon (NN) interactions at next-to-next-to-leading-order (N2LO). The structure of the chiral interactions is such that each coupling in the DME Fock functional can be decomposed into a coupling constant arising from zero-range contact interactions and a coupling function of the density arising from the universal long-range pion exchanges. This motivates a new microscopically-guided Skyrme phenomenology where the density-dependent couplings associated with the underlying pion-exchange interactions are added to standard empirical Skyrme functionals, and the density-independent Skyrme parameters subsequently refit to data. A link to a downloadable Mathematica notebook containing the novel density-dependent couplings is provided.
Gebremariam, B., E-mail: gebremar@gmail.co [National Superconducting Cyclotron Laboratory, 1 Cyclotron Laboratory, East-Lansing, MI 48824 (United States); Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States); Bogner, S.K., E-mail: bogner@nscl.msu.ed [National Superconducting Cyclotron Laboratory, 1 Cyclotron Laboratory, East-Lansing, MI 48824 (United States); Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States); Duguet, T., E-mail: thomas.duguet@cea.f [National Superconducting Cyclotron Laboratory, 1 Cyclotron Laboratory, East-Lansing, MI 48824 (United States); Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States); CEA, Centre de Saclay, IRFU/Service de Physique Nucleaire, F-91191 Gif-sur-Yvette (France)
2011-02-01
The density matrix expansion (DME) of Negele and Vautherin is a convenient tool to map finite-range physics associated with vacuum two- and three-nucleon interactions into the form of a Skyrme-like energy density functional (EDF) with density-dependent couplings. In this work, we apply the improved formulation of the DME proposed recently in (arXiv:0910.4979) by Gebremariam et al. to the non-local Fock energy obtained from chiral effective field theory (EFT) two-nucleon (NN) interactions at next-to-next-to-leading-order (N{sup 2}LO). The structure of the chiral interactions is such that each coupling in the DME Fock functional can be decomposed into a coupling constant arising from zero-range contact interactions and a coupling function of the density arising from the universal long-range pion exchanges. This motivates a new microscopically-guided Skyrme phenomenology where the density-dependent couplings associated with the underlying pion-exchange interactions are added to standard empirical Skyrme functionals, and the density-independent Skyrme parameters subsequently refit to data. A link to a downloadable Mathematica notebook containing the novel density-dependent couplings is provided.
Recent COMPASS results on the nucleon longitudinal spin structure and QCD fits
Andrieux Vincent
2014-01-01
Full Text Available The latest measurements of the proton longitudinal spin structure function, ɡ1p, in the deep inelastic (DIS regime are presented. They improve the statistical accuracy of the existing data and extend the kinematic domain to a lower value of x and higher values of Q2. A global NLO QCD fit of all ɡ1 world data on the proton, deuteron and neutron has been achieved. The results give a quantification of the quark spin contribution to the nucleon spin, 0.26 < ΔΣ < 0.34 at 3 (GeV/c2 in M̅S̅ scheme. The errors are dominated by the uncertainty on the shape of the functional forms assumed in the fit. A new verification of the fundamental Bjorken sum rule is obtained at a 9% level, using only COMPASS ɡ1 proton and deuteron measurements. Preliminary results of a reevaluation of the gluon polarization Δɡ/ɡ are presented. The analysis is based on double spin asymmetry of high-pT hadron production cross-sections in the DIS regime. A positive value of 〈Δɡ/ɡ〉 = 0.113 ± 0.038 ± 0.035 is obtained at leading order at x ~ 0.1. In parallel, the double spin asymmetry in the photoproduction regime is also studied. Finally, preliminary results on quark fragmentation functions into pions extracted from a LO fit of pion multiplicities in semi-inclusive DIS are presented.
Self-consistent Green's functions calculation of the nucleon mean-free path
Transport coefficients provide a unique insight into the near-equilibrium behavior of quantum many-body systems. The mean-free path, ?, of a particle within a dense medium is a basic transport coefficient, at the basis of several theoretical concepts and closely related to experimentally measured quantities. Green's functions techniques are particularly well suited to study such transport properties, since they are naturally formulated in the time domain. We present a calculation of the mean-free path of a nucleon in symmetric nuclear matter using self-consistent ladder self-energies extended to the complex energy plane. Our results indicate that, for energies above 50 MeV at densities close to saturation, a nucleon has a mean-free path of 4 to 5 femtometers.
When the new data on polarised lepton nucleon scattering are compared at the same value of Q2 and with a common set of assumptions, a consistent picture of the spin content of the nucleon begins to emerge. Higher order effects in 0(αs), higher twist effects, modern data on unpolarized structure functions and an updated value for F/D are all important in analysing the data. The detailed x dependences of the polarisation asymmetry in the valence quark region are shown to confirm 20 year old predictions of the quark model and I argue that these are an important ingredient in decoding the nucleon spin puzzle. (author)
When the new data on polarised lepton nucleon scattering are compared at the same value of Q2 and with a common set of assumptions, a consistent picture of the spin content of the nucleon begins to emerge. Higher order effects in O(?s), higher twist effects, modern data on unpolarised structure functions and an updated value for F/D are all important in analysing the data. The detailed x dependences of the polarisation asymmetry in the valence quark region are shown to confirm 20 year old predictions of the quark model and I argue that these are an important ingredient in decoding the nucleon spin puzzle. (author)
Electromagnetic structure of few-nucleon ground states
Marcucci, L. E.; Gross, F.; Pea, M. T.; Piarulli, M.; Schiavilla, R.; Sick, I.; Stadler, A.; Van Orden, J. W.; Viviani, M.
2016-02-01
Experimental form factors of the hydrogen and helium isotopes, extracted from an up-to-date global analysis of cross sections and polarization observables measured in elastic electron scattering from these systems, are compared to predictions obtained in three different theoretical approaches: the first is based on realistic interactions and currents, including relativistic corrections (labeled as the conventional approach); the second relies on a chiral effective field theory description of the strong and electromagnetic interactions in nuclei (labeled ?EFT) the third utilizes a fully relativistic treatment of nuclear dynamics as implemented in the covariant spectator theory (labeled CST). For momentum transfers below Q? 5 fm?1 there is satisfactory agreement between experimental data and theoretical results in all three approaches. However, at Q? 5 fm?1, particularly in the case of the deuteron, a relativistic treatment of the dynamics, as is done in the CST, is necessary. The experimental data on the deuteron A structure function extend to Q? 12 fm?1, and the close agreement between these data and the CST results suggests that, even in this extreme kinematical regime, the study of few-body form factors provides no evidence for new effects coming from quark and gluon degrees of freedom at short distances.
Wave functions of the nucleon and its parity partner from lattice QCD
We compute moments of distribution amplitudes using gauge configurations with two flavors of clover fermions from QCDSF/DIK and operators which are optimized with respect to their behavior under the lattice symmetries. The knowledge of these quantities helps in understanding the internal structure of hadrons and in the analysis of (semi-)exclusive processes. We present results for the nucleon distribution amplitude which suggest that the asymmetries (the deviations from the asymptotic form) are smaller than indicated by sum rule calculations. Using the same approach we were also able to calculate the same quantities for the N*(1535), the parity partner of the nucleon. These results show a stronger deviation from the asymptotic form. (orig.)
Wave functions of the nucleon and its parity partner from lattice QCD
Warkentin, Nikolaus; Braun, Vladimir M.; Goeckeler, Meinulf [Regensburg Univ. (DE). Inst. fuer Theoretische Physik] (and others)
2008-11-15
We compute moments of distribution amplitudes using gauge configurations with two flavors of clover fermions from QCDSF/DIK and operators which are optimized with respect to their behavior under the lattice symmetries. The knowledge of these quantities helps in understanding the internal structure of hadrons and in the analysis of (semi-)exclusive processes. We present results for the nucleon distribution amplitude which suggest that the asymmetries (the deviations from the asymptotic form) are smaller than indicated by sum rule calculations. Using the same approach we were also able to calculate the same quantities for the N{sup *}(1535), the parity partner of the nucleon. These results show a stronger deviation from the asymptotic form. (orig.)
A model study of nuclear structure functions
Gonzlez Marhuenda, Pedro; Vento Torres, Vicente; Traini, Marco; Zambarda, Andrea
1994-01-01
We calculate the structure function for a deuteron using the hadronic quark cluster decomposition. By assuming that nuclei might be composed of quasi deuterons, we study their structure functions. The procedure enables a quantum mechanical parametrization of various scenarios, among them nuclear dynamics and nucleon swelling. Moreover it is specially suited to study quark exchange effects. We show, within a scheme where perturbative evolution effects are minimized, that the region around x=1 ...
Matthias Burkardt
2009-07-01
Polarized structure functions at low $Q^2$ have the physical interpretation of (generalized) spin polarizabilities. At high $Q^2$, the polarized parton distribution $g_2(x)$ provides access to quark-gluon correlations in the nucleon. We discuss the interpretation of the $x^2$ moment of $\\bar{g}_2(x)$ as an average transverse force on quarks in deep-inelastic scattering from a transversely polarized target. Qualitative connections with generalized parton distributions are emphasized. The $x^2$ moment of the chirally-odd twist-3 parton distribution $e(x)$ provides information on the dependence of the average transverse force on the transversity of the quark.
The Structure of the Nucleon and its Excited States
The past year has been an exciting and productive one for particle physics research at Abilene Christian University. The thrust of our experimental investigations is the study of the nucleon and its excited states. Laboratories where these investigations are presently being conducted are the AGS at Brookhaven, Fermilab and LAMPF. Some analysis of the data for experiments at the Petersburg Nuclear Physics Institute (Gatchina, Russia) is still in progress. Scheduling of activities at different laboratories inevitably leads to occasional conflicts. This likelihood is increased by the present budget uncertainties at the laboratories that make long-term scheduling difficult. For the most part, the investigators have been able to avoid such conflicts. Only one experiment received beam time in 1994 (E890 at the AGS). The situation for 1995-1996 also appears manageable at this point. E890 and another AGS experiment (E909) will run through May, 1995. El 178 at LAMPF is presently scheduled for August/September 1995. E866 at Fermilab is scheduled to start in Spring/Summer 1996. Undergraduate student involvement has been a key element in this research contract since its inception. Summer students participated at all of the above laboratories in 1994 and the same is planned in 1995. A transition to greater involvement by graduate students will provide cohesiveness to ACU involvement at a given laboratory and full-time on-site involvement in the longer running experiments at FNAL and BNL. Funds to support a full-time graduate student are requested this year. Finally, collaboration by Russian, Croatian and Bosnian scientists has proven to be mutually beneficial to these experimental programs and to the overall programs at the institutions involved. Past support has been augmented by other grants from government agencies and from the Research Council at Abilene Christian University. Additional funds are requested in this renewal to enable more programmatic support for these efforts, so that long-range plans can be made to carry out the experiments and to perform the analysis
Measurements of the neutron polarized structure function at SLAC
Detailed measurements of unpolarized or spin-averaged nucleon structure functions over the past two decades have led to detailed knowledge of the nucleon's internal momentum distribution. Polarized nucleon structure function measurements, which probe the nucleon's internal spin distribution, started at SLAC in 1976. E-142 has recently measured the neutron polarized structure function g1n(x) over the range 0.03 ≤ x ≤ 0.6 at an average Q2 of 2 GeV2 and found the integral In = ∫01g1n(x)dx=-0.022±0.011. E-143, which took data recently, has measured g1p and g14. Two more experiments (E-154 and E-155) will extend these measurements to lower x and higher Q2
Gebremariam, B; Duguet, T
2010-01-01
The density matrix expansion (DME) of Negele and Vautherin is a convenient tool to map finite-range physics associated with vacuum two- and three-nucleon interactions into the form of a Skyme-like energy density functional (EDF) with density-dependent couplings. In this work, we apply the improved formulation of the DME proposed recently in arXiv:0910.4979 by Gebremariam {\\it et al.} to the non-local Fock energy obtained from chiral effective field theory (EFT) two-nucleon (NN) interactions at next-to-next-to-leading-order (N$^2$LO). The structure of the chiral interactions is such that each coupling in the DME Fock functional can be decomposed into a cutoff-dependent coupling {\\it constant} arising from zero-range contact interactions and a cutoff-independent coupling {\\it function} of the density arising from the universal long-range pion exchanges. This motivates a new microscopically-guided Skyrme phenomenology where the density-dependent couplings associated with the underlying pion-exchange interactions...
Nuclear energy density functional from chiral pion-nucleon dynamics revisited
Kaiser, N
2009-01-01
We use a recently improved density-matrix expansion to calculate the nuclear energy density functional in the framework of in-medium chiral perturbation theory. Our calculation treats systematically the effects from $1\\pi$-exchange, iterated $1\\pi$-exchange, and irreducible $2\\pi$-exchange with intermediate $\\Delta$-isobar excitations, including Pauli-blocking corrections up to three-loop order. We find that the effective nucleon mass $M^*(\\rho)$ entering the energy density functional is identical to the one of Fermi-liquid theory when employing the improved density-matrix expansion. The strength $F_\
Lynn, J E
2015-01-01
I discuss our recent work on Green's function Monte Carlo (GFMC) calculations of light nuclei using local nucleon-nucleon interactions derived from chiral effective field theory (EFT) up to next-to-next-to-leading order (N$^2$LO). I present the natural extension of this work to include the consistent three-nucleon (3N) forces at the same order in the chiral expansion. I discuss our choice of observables to fit the two low-energy constants which enter in the 3N sector at N$^2$LO and present some results for light nuclei.
Polarized Structure Functions with Neutrino Beams
Forte, Stefano
2005-01-01
We review the potential impact of neutrino data on the determination of the spin structure of the nucleon. We show that a flavour decomposition of the parton structure of the nucleon as required by present-day precision phenomenology could only be achieved at a neutrino factory. We discuss how neutrino scattering data would allow a full resolution of the nucleon spin problem.
This book contains the lectures given at the International Summer School on Structure and Stability of Nucleon and Nuclear Systems held in Predeal, Romania, in the period August 24 - September 5, 1998. The program of the school covered the following six topics: Nuclear structure (11 lectures); Dynamics of nuclear systems explored by collisions with various projectiles at different energies (8 lectures); Light and heavy cluster emission, cold and ternary fission (4 lectures); β+-, 2νββ, 0νββ and other neutrino processes; Structure and stability of nucleons (3 lectures); Nuclear matter under exotic conditions (2 lectures). Related to these topics were 17 short communications whose full text can be obtained on request from the authors or from a special issue of Romanian Journal of Physics. The aim of the school was concentrated on the behaviour of nuclear systems under extreme conditions, to understand newly discovered properties of complex nuclei and nucleons, to approach subjects bordering nuclear and particle physics, to identify specific phenomena taking place under conditions met presumably in stars, to investigate the newly explored systems of very short half-life. Exotic phenomena like halo structure of some light nuclei, superdeformation, structure of nuclei lying far from the stability line, specific properties of hot nuclei were also considered in many lectures
Studies of partonic transverse momentum and spin structure of the nucleon
Contalbrigo M.
2014-06-01
Full Text Available The investigation of the partonic degrees of freedom beyond collinear approximation (3D description has been gained increasing interest in the last decade. The Thomas Jefferson National Laboratory, after the CEBAF upgrade to 12 GeV, will become the most complete facility for the investigation of the hadron structure in the valence region by scattering of polarized electron off various polarized nucleon targets. A compendium of the planned experiments is here presented.
Studies of partonic transverse momentum and spin structure of the nucleon
Contalbrigo, Marco M. [INFN, Ferrara, Italy
2014-06-01
The investigation of the partonic degrees of freedom beyond collinear approximation (3D description) has been gained increasing interest in the last decade. The Thomas Jefferson National Laboratory, after the CEBAF upgrade to 12 GeV, will become the most complete facility for the investigation of the hadron structure in the valence region by scattering of polarized electron off various polarized nucleon targets. A compendium of the planned experiments is here presented.
The scale dependence of single-nucleon shell structure
Som, V.; Duguet, T.; Hergert, H.; Holt, J. D.
2015-10-01
We address the scale dependence of (effective) single-particle energies, non-observable quantities that are commonly used for interpreting nuclear structure observables measured in experiments and computed in many-body theories. We first demonstrate their scale dependence on a formal level, making them intrinsically theoretical objects, before illustrating this point via ab initio calculations in the oxygen isotopes. Finally, we consider a modified definition of effective single-particle energy and investigate its running properties.
Nucleon structure in lattice QCD with dynamical domain-wall fermions quarks
Huey-Wen Lin; Shigemi Ohta
2006-07-23
We report RBC and RBC/UKQCD lattice QCD numerical calculations of nucleon electroweak matrix elements with dynamical domain-wall fermions (DWF) quarks. The first, RBC, set of dynamical DWF ensembles employs two degenerate flavors of DWF quarks and the DBW2 gauge action. Three sea quark mass values of 0.04, 0.03 and 0.02 in lattice units are used with about 200 gauge configurations each. The lattice cutoff is about 1.7 GeV and the spatial volume is about (1.9 fm){sup 3}. Despite the small volume, the ratio of the isovector vector and axial charges g{sub A}/g{sub V} and that of structure function moments
NUCLEON STRUCTURE IN LATTICE QCD WITH DYNAMICAL DOMAIN--WALL FERMIONS QUARKS.
LIN H.-W.; OHTA, S.
2006-10-02
We report RBC and RBC/UKQCD lattice QCD numerical calculations of nucleon electroweak matrix elements with dynamical domain-wall fermions (DWF) quarks. The first, RBC, set of dynamical DWF ensembles employs two degenerate flavors of DWF quarks and the DBW2 gauge action. Three sea quark mass values of 0.04, 0.03 and 0.02 in lattice units are used with 220 gauge configurations each. The lattice cutoff is a{sup -1} {approx} 1.7GeV and the spatial volume is about (1.9fm){sup 3}. Despite the small volume, the ratio of the isovector vector and axial charges g{sub A}/g{sub V} and that of structure function moments
Isovector part of nuclear energy density functional from chiral two- and three-nucleon forces
Kaiser, N
2012-01-01
A recent calculation of the nuclear energy density functional from chiral two- and three-nucleon forces is extended to the isovector terms pertaining to different proton and neutron densities. An improved density-matrix expansion is adapted to the situation of small isospin-asymmetries and used to calculate in the Hartree-Fock approximation the density-dependent strength functions associated with the isovector terms. The two-body interaction comprises of long-range multi-pion exchange contributions and a set of contact terms contributing up to fourth power in momenta. In addition, the leading order chiral three-nucleon interaction is employed with its parameters fixed in computations of nuclear few-body systems. With this input one finds for the asymmetry energy of nuclear matter the value $A(\\rho_0) \\simeq 26.5\\,$MeV, compatible with existing semi-empirical determinations. The strength functions of the isovector surface and spin-orbit coupling terms come out much smaller than those of the analogous isoscalar...
Navratil, P; Caurier, E
2003-10-14
The authors calculate properties of A = 6 system using the accurate charge-dependent nucleon-nucleon (NN) potential at fourth order of chiral perturbation theory. By application of the ab initio no-core shell model (NCSM) and a variational calculation in the harmonic oscillator basis with basis size up to 16 {h_bar}{Omega} they obtain the {sup 6}Li binding energy of 28.5(5) MeV and a converged excitation spectrum. Also, they calculate properties of {sup 10}B using the same NN potential in a basis space of up to 8 {h_bar}{Omega}. The results are consistent with results obtained by standard accurate NN potentials and demonstrate a deficiency of Hamiltonians consisting of only two-body terms. At this order of chiral perturbation theory three-body terms appear. It is expected that inclusion of such terms in the Hamiltonian will improve agreement with experiment.
Unified approach to structure factors and neutrino processes in nucleon matter
We present a unified approach to neutrino processes in nucleon matter based on Landau's theory of Fermi liquids that includes one and two quasiparticle-quasihole pair states as well as mean-field effects. We show how rates of neutrino processes involving two nucleons may be calculated in terms of the collision integral in the Landau transport equation for quasiparticles. Using a relaxation time approximation, we solve the transport equation for density and spin-density fluctuations and derive a general form for the response functions. We apply our approach to neutral-current processes in neutron matter, where the spin response function is crucial to the calculation of neutrino elastic and inelastic scattering and neutrino-pair bremsstrahlung and absorption from strongly interacting nucleons. We calculate the relaxation rates using modern nuclear interactions and including many-body contributions, and find that rates of neutrino processes are reduced compared with estimates based on the one-pion exchange interaction, which is used in current simulations of core-collapse supernovae
What we can learn about nucleon spin structure from recent data
We have used recent data from the CERN and SLAC to extract information about nucleon spin structure. We find that the SMC proton data on ∫01g1pdx, the E142 neutron data on ∫01g1ndx, and the deuteron data from the SMC and E143 give different results for fractions of the spin carried by each of the constituents. These appear to lead to two different and incompatible models for the polarized strange sea. The polarized gluon distribution occurring in the gluon anomaly does not have to be large in order to be consistent with either set of experimental data. However, it appears that the discrepancies in the implications of these data cannot be resolved with any simple theoretical arguments. We conclude that more experiments must be performed in order to adequately determine the fraction of spin carried by each of the nucleon constituents. copyright 1997 The American Physical Society
What we can learn about nucleon spin structure from recent data
Goshtasbpour, M; Ramsey, Gordon P
1997-01-01
We have used recent polarized deep-inelastic scattering data from CERN and SLAC to extract information about nucleon spin structure. We find that the SMC proton data, the E142 neutron data and the deuteron data from SMC and E143 give different results for fractions of the spin carried by each of the constituents. These appear to lead to two different and incompatible models for the polarized strange sea. The polarized gluon distribution occuring in the gluon anomaly does not have to be large in order to be consistent with either set of experimental data. However, it appears that the discrepancies in the implications of these data cannot be resolved with any simple theoretical arguments. We conclude that more experiments must be performed in order to adequately determine the fraction of spin carried by each of the nucleon constituents.
Meson-nucleon scattering in the functional quantum theory of the non linear spinor field
The results of this work are sumarized in the following points: 1. Determination of coupling constants, based on the nucleon eigenvalue equation with the two-point function, regularized by two single poles with small masses, gives a result deviating only little from the values given the theory with dipolar regularisation. These masses are considered here only as a means for regularisation and are not connected with physical particles. 2. The meson masses calculated are satisfying, too. So the two-point function, modified owing to the scalar product, has been shown to give equally good results for the calculation of coupling constants and mass eigenvalues. 3. In forward direction the differential cross section for pion-proton-scattering qualitively shows the correct behaviour. Indeed for back scattering a singularity exists which is characteristic for a theory with particles of zero mass. Thus ist seems necessary to first adapt the Greens function and to leave the unsymmetrical treatment of F and G. (orig.)
We present high statistics results for the structure of the nucleon from a mixed-action calculation using 2+1 flavors of asqtad sea and domain-wall valence fermions. We perform extrapolations of our data based on different chiral effective field theory schemes and compare our results with available information from phenomenology. We discuss vector and axial form factors of the nucleon, moments of generalized parton distributions, including moments of forward parton distributions, and implications for the decomposition of the nucleon spin.
On the effect of nucleon mass-shift and nucleon correlations on the EMC effect
The influence on the EMC effect of nucleon mass-shift and short-range correlations determining a high momentum part of the nucleon momentum distribution is studied. The dispersion relation technique is used, the nucleus being related as a system consisting of A nucleons. It is shown that the ratio of the structure functions F2A(x)/F2N(x) is very sensitive to the correlations in the region x?0.3. It is demonstrated that decrease of the effective nucleon mass by 65 MeV, compared to the free value, leads to a quite satisfactory description of the EMC effect
Towards AN Understanding of Nucleon Spin Structure:. from Hard to Soft Scales
Bass, Steven D.; Aidala, Christine A.
The workshop The Helicity Structure of the Nucleon (BNL June 5, 2006) was organized as part of the 2006 RHIC & AGS Users' Meeting to review the status of the spin problem and future directions. The presentations can be found at the workshop's website:1 www.phenix.bnl.gov/WWW/publish/caidala/UsersHelicityWorkshop2006/. Recent data suggest small polarized glue and strangeness in the proton. Here we present a personal summary of the main results and presentations. What is new and exciting in the data, and what might this tell us about the structure of the proton?
The role of spectator diquarks in deep inelastic structure functions
The significance of the spectral distribution of diquarks in the nucleon for the SU(6) symmetry breaking in deep inelastic structure functions is investigated in a field theoretical framework, which ensures correct kinematical and symmetry properties for the structure functions. (orig.)
Structure functions extracted from muon pair production at the SPS
Dimuon data provided by πN interactions were analysed in the framework of the Drell-Yan quark fusion model in order to extract the pion and nucleon structure functions. Our results are compared to the structure functions obtained in other experiments
Electro-magnetic nucleon form factors and their spectral functions in soliton models
Holzwarth, G
1996-01-01
It is demonstrated that in simple soliton models essential features of the electro-magnetic nucleon form factors observed over three orders of magnitude in momentum transfer t are naturally reproduced. The analysis shows that three basic ingredients are required: an extended object, partial coupling to vector mesons, and relativistic recoil corrections. We use for the extended object the standard skyrmion, one vector meson propagator for both isospin channels, and the relativistic boost to the Breit frame. Continuation to timelike t leads to quite stable results for the spectral functions in the regime from the 2- or 3-pion threshold to about two rho masses. Especially the onset of the continuous part of the spectral functions at threshold can be reliably determined and there are strong analogies to the results imposed on dispersion theoretic approaches by the unitarity constraint.
The form factors of the nucleons
The study of the electromagnetic form factors of the nucleons are of fundamental importance in understanding nucleon structure. The form factors contain all the information about the deviation from pointlike structure of the charge and magnetization current distributions of the nucleons. The hope is that measurements at sufficiently large momentum transfers can provide a microscopic understanding of the nucleon wave functions in terms of their constituent quark amplitudes. Recent measurements of the electric GE(Q2) and magnetic GM(Q2) form factors of the nucleons are reviewed and compared to theoretical calculations based on non-perturbative QCD sum rules, diquark, relativistic constituent quark, and vector meson dominance (VMD) models. A short summary of ongoing and future measurements is also presented
Polarised structure functions from the SMC experiment
Lamanna, M. [Istituto Nazionale di Fisica Nucleare, Trieste (Italy). Lab. Area di Ricerca
1998-06-01
The spin muon collaboration (SMC, NA47) at CERN has measured polarised structure functions of the nucleon in the years 1991-1996. All the published data on g{sub 1}{sup p} and g{sub 1}{sup d} are discussed and the new preliminary results of g{sub 1}{sup p} are presented. The test of the Bjorken sum rule and the violation of the Ellis-Jaffe sum rules are also discussed. (orig.). 30 refs.
Study of the Nucleon Spin Structure by the Drell–Yan Process in the COMPASS-II Experiment
Quaresma, M
2012-01-01
The Parton Distribution Functions (PDFs) and the spin structure of the nucleon are important topics studied by the COMPASS experiment. The Drell–Yan (DY) process will be used in the future COMPASS-II measurements to access the Transverse Momentum Dependent PDFs (TMD PDFs). Studying the angular distributions of dimuons from the DY reactions with a negative pion beam with 190 GeV/c momentum and a transversely polarised proton target, we will be able to extract the azimuthal spin asymmetries and to access the various TMD PDFs, such as Sivers and Boer–Mulders functions. The start of the COMPASS DY experiment is scheduled for 2014. Three beam tests have been already performed, one of them in 2009 using a prototype hadron absorber downstream of the target, to understand the background reduction factors and the spectrometer response, and also to verify our results from Monte Carlo simulations. COMPASS aims at performing the first DY experiment with a transversely polarised target.
Status of nucleon structure calculations with 2+1 flavors of domain wall fermions
Lin, Meifeng
2013-01-01
We report the status of our nucleon structure calculations with 2+1 flavors of domain wall fermions on the RBC-UKQCD $32^3\\times64$ gauge ensembles with the Iwasaki+DSDR action. These ensembles have a fixed lattice scale of 1/a = 1.37 GeV, and two pion masses of about 170 and 250 MeV. Preliminary results for the isovector electromagnectic form factors and their corresponding root-mean-squared (r.m.s.) radii will be presented.
Isospin dependence of nucleon Correlations in ground state nuclei
Charity, R J; Sobotka, L G; Waldecker, S J
2013-01-01
The dispersive optical model (DOM) as presently implemented can investigate the isospin (nucleon asymmetry) dependence of the Hartree-Fock-like potential relevant for nucleons near the Fermi energy. Data constraints indicate that a Lane-type potential adequately describes its asymmetry dependence. Correlations beyond the mean-field can also be described in this framework, but this requires an extension that treats the non-locality of the Hartree-Fock-like potential properly. The DOM has therefore been extended to properly describe ground-state properties of nuclei as a function of nucleon asymmetry in addition to standard ingredients like elastic nucleon scattering data and level structure. Predictions of nucleon correlations at larger nucleon asymmetries can then be made after data at smaller asymmetries constrain the potentials that represent the nucleon self-energy. A simple extrapolation for Sn isotopes generates predictions for increasing correlations of minority protons with increasing neutron number. S...
Structure functions in the bag model
In this paper we present calculations of nucleon structure functions in the three-dimensional MIT bag model. The nucleon wave functions are modified by the Peierls Yoccoz projection in order to give eigenstates of the total momentum operator. Pair creation by the probe is taken into account. Without this the quark distributions would not obey normalization requirements. The quark distributions have vanishing support for x>1. The effect of one-gluon exchange, yielding the N-Δ mass splitting, is incorporated. This has significant effects on the d/u ratio as well as the spin-dependent g1(x) of the neutron. Finally, the results are compared to data after allowing for perturbative QCD evolution
Maydanyuk, Sergei P.; Zhang, Peng-Ming; Zou, Li-Ping
2016-01-01
We analyze the nucleon structure of the α -decaying nucleus to see if it can be visible in the experimental bremsstrahlung spectra of the emitted photons which accompany such a decay. We develop a new formalism of the bremsstrahlung model taking into account the distribution of nucleons in the α -decaying nuclear system. We conclude the following. (1) After inclusion of the nucleon structure in the model the calculated bremsstrahlung spectrum is changed very slowly for a majority of the α -decaying nuclei. However, we have observed that visible changes really exist for the 106Te nucleus (Qα=4.29 MeV, T1 /2=70 μs) even for the energy of the emitted photons up to 1 MeV. This nucleus is a good candidate for future experimental study of this task. (2) Inclusion of the nucleon structure in the model increases the bremsstrahlung probability of the emitted photons. (3) We find the following tendencies for obtaining the nuclei, which have bremsstrahlung spectra more sensitive to the nucleon structure: (a) direction to nuclei with smaller Z and (b) direction to nuclei with larger Qα values.
Chang, Wen-Chen
2015-01-01
The observation of the violation of Lam-Tung relation in the $\\pi N$ Drell-Yan process triggered many theoretical speculations. The TMD Boer-Mulders functions characterizing the correlation of transverse momentum and transverse spin for partons in unpolarized hadrons could nicely account for the violation. The COMPASS experiment at CERN will measure the angular distributions of dimuons from the unpolarized Drell-Yan process over a wide kinematic region and study the beam particle dependence. Significant statistics is expected from a successful run in 2015 which will bring further understanding of the origin of the violation of Lam-Tung relation and of the partonic transverse spin structure of the nucleon.
Neutrino charged-current structure functions
Charged current total cross sections and structure functions were extracted from neutrino and antineutrino data taken with the Fermilab narrow band beam. The cross section results are sigma/sup nu//E = 0.701 +- 0.004 +- 0.025 x 10-38 cm2/GeV and sigma/sup nu-bar//E = 0.350 +- 0.04 +- 0.022 x 10-38 cm2/GeV. The structure functions exhibit scaling violations. A comparison with structure functions obtained in muon scattering experiments indicates a ratio consistent with 18/5 within the systematic errors of both experiments. The structure function function xF3 is used to test the Gross-Llewellyn Smith sum rule. The data is in agreement with the prediction of 3 for the number of valence quarks on the nucleon
The topic of lepton-nucleon inclusive scattering is reviewed. Some of the experiments providing data on these interactions are described first. Then the constituent model of the nucleon and the contribution of various types of experiments are discussed; data from the experiments are compared and some simple predictions of the quark model are covered. Next, some of the fundamental notions behind quantum chromodynamics (QCD) are presented. Subsequent sections examine detailed tests of QCD. These include the ratio of longitudinal to transverse photoabsorption cross sections, the proton form factor in elastic ep scattering, and the dependence of structure functions on Q2. In conclusion, all the tests of QCD are tabulated, and the results are evaluated. 32 references, 33 figures, 4 tables
Litvinova, Elena
2016-04-01
The relativistic particle-vibration coupling (RPVC) model is extended by the inclusion of isospin-flip excitation modes into the phonon space, introducing a new mechanism of dynamical interaction between nucleons with different isospin in the nuclear medium. Protons and neutrons exchange by collective modes which are formed by isovector π and ρ-mesons, in turn, softened considerably because of coupling to nucleons of the medium. These modes are investigated within the proton-neutron relativistic random phase approximation (pn-RRPA) and relativistic proton-neutron time blocking approximation (pn-RTBA). The appearance of isospin-flip states with sizable transition probabilities at low energies points out that they are likely to couple to the single-particle degrees of freedom and, in addition to isoscalar low-lying phonons, to modify their spectroscopic characteristics. Such a coupling is quantified for the shell structure of 100,132Sn and found significant for the location of the dominant single-particle states.
Litvinova, Elena
2015-01-01
The relativistic particle-vibration coupling (RPVC) model is extended by the inclusion of spin- and isospin-flip excitation modes into the phonon space, introducing a new mechanism of dynamical interaction between nucleons with different isospin in the nuclear medium. Protons and neutrons exchange by collective modes which are formed by isovector $\\pi$ and $\\rho$-mesons, in turn, softened considerably because of coupling to nucleons of the medium. These modes are investigated within the proton-neutron relativistic random phase approximation (pn-RRPA) and relativistic proton-neutron time blocking approximation (pn-RTBA). The appearance of isospin-flip states with sizable transition probabilities at low energies points out that they are likely to couple to the single-particle degrees of freedom and, in addition to isoscalar low-lying phonons, to modify their spectroscopic characteristics. Such a coupling is quantified for the shell structure of $^{100,132}$Sn and found significant for the location of the domina...
Moments of Spin Structure Functions: Sum Rules and Polarizabilities
Chen, Jian-ping
2010-01-01
Nucleon structure study is one of the most important research areas in modern physics and has challenged us for decades. Spin has played an essential role and often brought surprises and puzzles to the investigation of the nucleon structure and the strong interaction. New experimental data on nucleon spin structure at low to intermediate momentum transfers combined with existing high momentum transfer data offer a comprehensive picture in the strong region of the interaction and of the transition region from the strong to the asymptotic-free region. Insight for some aspects of the theory for the strong interaction, Quantum Chromodynamics (QCD), is gained by exploring lower moments of spin structure functions and their corresponding sum rules. These moments are expressed in terms of an operator-product expansion using quark and gluon degrees of freedom at moderately large momentum transfers. The higher-twist contributions have been examined through the evolution of these moments as the momentum transfer varies...
Elastic electron-deuteron scattering with new nucleon-nucleon potentials and nucleon form factors
We present elastic e-d scattering observables obtained from the recent N-N interaction models proposed by the Bonn and Nijmegen groups. In particular, we discuss the pertinent results for the electric and magnetic structure functions as well as the deuteron tensor polarization and charge form factor, especially with respect to their dependence on the choice of the nucleon form factors. We find that for these new N-N potentials only a particular model of nucleon form factors, different from the traditional ones, allows for a comprehensive reproduction of all elastic e-d data at low and moderate momentum transfers. (author)
New measurements of high-momentum nucleons and short-range structures in nuclei
Fomin, N; Asaturyan, R; Benmokhtar, F; Boeglin, W; Bosted, P; Bruell, A; Bukhari, M H S; Chudakov, E; Clasie, B; Connell, S H; Dalton, M M; Daniel, A; Day, D B; Dutta, D; Ent, R; Fassi, L El; Fenker, H; Filippone, B W; Garrow, K; Gaskell, D; Hill, C; Holt, R J; Horn, T; Jones, M K; Jourdan, J; Kalantarians, N; Keppel, C E; Kiselev, D; Kotulla, M; Lindgren, R; Lung, A F; Malace, S; Markowitz, P; McKee, P; Meekins, D G; Mkrtchyan, H; Navasardyan, T; Niculescu, G; Opper, A K; Perdrisat, C; Potterveld, D H; Punjabi, V; Qian, X; Reimer, P E; Roche, J; Rodriguez, V M; Rondon, O; Schulte, E; Seely, J; Segbefia, E; Slifer, K; Smith, G R; Solvignon, P; Tadevosyan, V; Tajima, S; Tang, L; Testa, G; Trojer, R; Tvaskis, V; Vulcan, W F; Wasko, C; Wesselmann, F R; Wood, S A; Wright, J; Zheng, X
2011-01-01
We present new, high-Q^2 measurements of inclusive electron scattering from high-momentum nucleons in nuclei. This yields an improved extraction of the strength of two-nucleon correlations for several nuclei, including light nuclei where clustering effects can, for the first time, be examined. The data extend to the kinematic regime where three-nucleon correlations are expected to dominate and we observe significantly greater strength in this region than previous measurements.
Gauge invariance, Lorentz covariance and canonical quantization in nucleon structure studies
Wang, Fan; Sun, W M; Zhang, P M; Wong, C W
2014-01-01
There are different operators of quark and gluon momenta, orbital angular momenta, and gluon spin in the nucleon structure study. The precise meaning of these operators are studied based on gauge invariance, Lorentz covariance and canonical quantization rule. The advantage and disadvantage of different definitions are analyzed. A gauge invariant canonical decomposition of the total momentum and angular momentum into quark and gluon parts is suggested based on the decomposition of the gauge potential into gauge invariant (covariant) physical part and gauge dependent pure gauge part. Challenges to this proposal are answered. \\keywords{Physical and pure gauge potentials; Gauge invariant canonical quark and gluon momenta, orbital angular momenta and spins; Homogeneous and non-homogeneous Lorentz transformations; Gauge invariant decomposition and gauge invariant extension; Classical and quantum measurements.
Nuclear Effects on the Spin-Dependent Structure Functions
We address the question how the spin-dependent nucleon structure function g1(x,Q2) gets modified when the nucleon is bound inside a nucleus. We analyze the influence of nuclear interactions using the Δ - π model, known to describe well the unpolarized effect, and the free polarized parton distributions. The results for the neutron in 3He and proton in 3H,7Li and 19F are presented, showing significant changes in the parton spin distributions and in their moments. Scattering processes off polarized 7Li are suggested which could justify these theoretical calculations and shed more light on both nuclear spin structure and short distance QCD. (author)
Influence of a shift of the nucleon mass and of nucleon correlations on the EMC effect
We study the influence of a shift of the nucleon mass, and of the short-range nucleon correlations which determine the hard part of the nucleon momentum distribution, on the EMC effect. We use the technique of dispersion integration, within the framework of which the nucleus is described as a system consisting of A nucleons. We demonstrate that the ratio of the structure functions F/sup A/2(x)F/sup N/2(x) is rather sensitive to the correlations in the region of xapprox. >0.3 and show that a decrease of the effective nucleon mass by ?65 MeV in comparison with the free value leads to a rather satisfactory description of the EMC effect
Sea and gluon spin structure function measurements at RHIC
Yokosawa, A.
1995-02-01
The first polarized collider where one collides 250-GeV/c beams of 70% polarized protons at high luminosity is under construction. This will allow a determination of the nucleon spin-dependent structure functions over a large range in x and a collection of sufficient W and Z events to investigate extremely interesting spin-related phenomena.
Polarized Structure Functions and the GDH Integral from Lattice QCD
Schierholz, G
2004-01-01
The Gerasimov-Drell-Hearn integral $I_{GDH}(Q^2)$, and its relation to polarized nucleon structure functions, is discussed from the lattice perspective. Of particular interest is the variation of $I_{GDH}(Q^2)$ with $Q^2$, and what it may teach us about the origin and magnitude of higher-twist contributions.
Studying the Phase-Space Structure of Nucleons Using Generalized Parton Distributions
Ahmad, Saeed; Liuti, Simonetta; Honkanen, Heli; Taneja, Swadhin K.
2006-11-01
We study the correlation of momentum and coordinate space distributions of partons which are measured in Deeply Virtual Compton Scattering (DVCS) reactions. Being able to understand the phase-space distributions of quarks, we hope to look into the question of `how much quark orbital angular momentum contributes towards the nucleon spin?' It was in fact suggested recently [1] that using the information provided by DVCS experiments, one can develop a complete three dimensional spatial picture of nucleons, along with the momentum distributions (the so-called Wigner distributions). However, in order pin down the spatial distribution in the longitudinal direction one has to take into account the constraint imposed by the uncertainty principle. In addition, similarly to inclusive deep-inelastic scattering, the lectromagnetic probe has an extended length in the longitudinal direction, known in the literature as ``Ioffe time'' [2]. Using the Generalized Parton Distributions (GPDs) obtained in [3] we define and evaluate ``Generalized Ioffe time'' distributions as a function of the additional degrees of freedom--both transverse, t = -2̂ and longitudinal, ξ--extracted from DVCS experiments. [1] A. V. Belitsky, X. d. Ji and F. Yuan, Phys. Rev. D 69, 074014 (2004) [2] B. L. Ioffe, Phys. Lett. B 30, 123 (1969); V. Del Duca, S. J. Brodsky and P. Hoyer, Phys. Rev. D 46, 931 (1992); V. Braun, P. Gornicki and L. Mankiewicz, Phys. Rev. D 51, 6036 (1995). [3] S. Liuti and S. K. Taneja, Phys. Rev. D 70, 074019 (2004); H. Honkanen, S. K. Taneja, S. Ahmad and S. Liuti, in preparation.
The longitudinal charge function in the quasi-elastic peak region is calculated, including effects of two-nucleon collisions. The coupled RPA equation for 2p2h states is solved, using a Thomas-Fermi type theory. To calculate the response function for RPA orders, the Gogny force (a density dependent finite range force) is used, both for the mean field and the residual ph interaction. To include the 2p2h states it was necessary to study the dynamic nuclear mass operator M in the 2p1h (2h1p) approximation. The Gogny force was used as interaction at the vertex of the mass operator. The density dependence of the Gogny force gives a pronounced surface peak in the imaginary part of M. The inclusion of the mass operator in the ph motion gives 2p2h states. Their influence considerably reduces the RPA order response and generally produces a better agreement between theory and experiment, although inexplicable exceptions remain. The investigation suggests that it is not necessary to modify the nuclear form factor
Ab initio Nuclear structure Theory with chiral two- plus three-nucleon interactions
Low-energy nuclear theory has entered an era of ab initio nuclear structure and reaction calculations based on input from QCD. One of the most promising paths from QCD to nuclear observables employs Hamiltonians constructed within chiral effective field theory as consistent starting point for precise ab initio nuclear structure and reaction studies. However, the full inclusion of chiral two- plus three-nucleon (NN+3N) interactions in exact and approximate many-body calculations still poses a formidable challenge. We discuss recent developments towards this goal, ranging from consistent Similarity Renormalization Group evolutions of NN+3N Hamiltonians to large-scale ab initio calculations for ground states and spectra in the Importance-Truncated No-Core Shell Model with full 3N interactions. We highlight recent achievements and discuss open issues and future perspectives for nuclear structure theory with QCD-based interactions. Moreover, we discuss successful steps towards merging ab initio structure and reaction theory and show applications to low-energy reactions in the p-shell relevant for astrophysics.
Nucleon Electromagnetic Form Factors
Although nucleons account for nearly all the visible mass in the universe, they have a complicated structure that is still incompletely understood. The first indication that nucleons have an internal structure, was the measurement of the proton magnetic moment by Frisch and Stern (1933) which revealed a large deviation from the value expected for a point-like Dirac particle. The investigation of the spatial structure of the nucleon, resulting in the first quantitative measurement of the proton charge radius, was initiated by the HEPL (Stanford) experiments in the 1950s, for which Hofstadter was awarded the 1961 Nobel prize. The first indication of a non-zero neutron charge distribution was obtained by scattering thermal neutrons off atomic electrons. The recent revival of its experimental study through the operational implementation of novel instrumentation has instigated a strong theoretical interest. Nucleon electro-magnetic form factors (EMFFs) are optimally studied through the exchange of a virtual photon, in elastic electron-nucleon scattering. The momentum transferred to the nucleon by the virtual photon can be selected to probe different scales of the nucleon, from integral properties such as the charge radius to scaling properties of its internal constituents. Polarization instrumentation, polarized beams and targets, and the measurement of the polarization of the recoiling nucleon have been essential in the accurate separation of the charge and magnetic form factors and in studies of the elusive neutron charge form factor
Probing spin-1 diquarks in deep inelastic structure functions
Within the scope of a new diquark model for deep inelastic structure functions presented by us recently we use the existing data on F1sup(ep)(x,Q2) to learn about the admixture of spin-1 diquarks in nucleons. It turns out that they are so rare, heavy and extended compared to spin-0 diquarks that they are presumably accidental and not dynamical. Their number and form factors can be understood qualitatively within this picture. Still, the spin-1 diquarks give interesting structures in data and, together with quarks and spin-0 diquarks, carry enough momentum to account for the full nucleon energy. A gluon component is hence not needed in the nucleon. (orig.)
Phenomenological nucleon-nucleon potential
The present situation of the nucleon-nucleon problems and the essential points concerning the one-boson-exchange model and the Paris potential are briefly reviewed. The extension of the nucleon-nucleon potential up to 2.5 GeV is discussed, and our recent phenomenological method for this extension is explained. Some of the successful results obtained by this phenomenological method are also shown. (author)
On the influence of nucleon correlations and nucleon mass-shift on the EMC effect
We study the influence of the EMC effect of nucleon mass-shift and short-range correlations determining a high momentum part of the nucleon momentum distribution. The dispersion relation technique is used, the nucleus being treated as a system consisting of A nucleus. It is shown that the ratio of the structure functions F2A(x)/F2N(x) is very sensitive to the correlations in the region x > or approx. 0.3. It is also shown that decrease of the nucleon mass by ? 65 MeV, compared to the free value, leads to a quite satisfactory description of the EMC effect. (orig.)
The x dependence of hadron structure functions is investigated. If quarks can exist in very low mass states (10 MeV for d and u quarks) the pion structure function is predicted to behave like (1-x) and not (1-x)2 in a x-region around 1. Relativistic and non-relativistic quark bound state pictures of hadrons are considered together with their relation with the Q2 evolution of structure functions. Good agreement with data is in general obtained
Arrington, J.; Coester, F.; Holt, R. J.; Lee, T. -S. H.
2008-01-01
Neutron structure functions can be extracted from proton and deuteron data and a representation of the deuteron structure. This procedure does not require DIS approximations or quark structure assumptions. We find that the results depend critically on properly accounting for the Q^2 dependence of proton and deuteron data. We interpolate the data to fixed Q^2, and extract the ratio of neutron to proton structure functions. The extracted ratio decreases with increasing x, up to x \\approx 0.9, w...
In-medium nucleon-nucleon potentials in configuration space
Based on the thermodynamic Green function approach two-nucleon correlations in nuclear matter at finite temperatures are revisited. To this end, we derive phase-equivalent effective r-space potentials that include the effect of Pauli blocking at a given temperature and density. These potentials enter into a Schroedinger equation that is the r-space representation of the Galitskii-Feynman equation for two nucleons. We explore the analytical structure of the equation in the complex k-plane by means of Jost functions. We find that despite the Mott effect the correlation with deuteron quantum numbers are manifested as antibound states, i.e. as zeros of the Jost function on the negative imaginary axis of the complex momentum space. The analysis presented here is also suited for Coulombic systems. (author)
Nucleon-nucleon correlations in dense nuclear matter
In this thesis new results on the problematics of the formation of nucleon-nucleon correlations in nuclear matter could be presented. Starting from a general study of the two-particle problem in matter we studied the occurrence of a suprafluid phase (pair condensate of nucleons). The Gorkov decoupling by means of anomalous Green functions was generalized, so that also Cooper pairs with spin 1 (triplet pairing) can be described. A generalized gap equation resulted, which permits to determine the order parameters of the suprafluied phase in arbitrary channels of the nucleon-nucleon scattering states. This equation was solvd in the 1S0-, in the 3P2-3F2, and in the 3S1-3D1 channel under application of realistic nucleon-nucleon potentials. The behaviour of the resulting gap parameters in the single channels was studied as function of density and temperature. (orig.)
Chromosome structure and function
Risley, M.S.
1986-01-01
This book presents topics in chromosome structure and function. Topics covered include: the structure of interphase chromatin; chromatin structure, gene expression and differentiation; organization of mitotic chromosomes; organization of meiotic chromosomes and synaptonimal complexes; the lampbrush chromsome of animal oocytes; dosage compensation in mammals: x chromosome inactivation; and polytene chromosomes.
A systematic survey on form factors and structure functions of deuteron electrodisintegration
Electromagnetic form factors and structure functions of deuterium are systematically studied in the non-relativistic domain in order to obtain information on the structure of the two-nucleon system, in particular, on the effects of meson exchange currents and isobar configurations. In this respect, the determination of the small interference structure functions of a coincidence experiment would be particularly rewarding. (orig.)
D. Day
2007-03-01
The nucleon form factors are still the subject of active investigation even after an experimental effort spanning 50 years. This is because they are of critical importance to our understanding of the electromagnetic properties of nuclei and provide a unique testing ground for QCD motivated models of nucleon structure. Progress in polarized beams, polarized targets and recoil polarimetry have allowed an important and precise set of data to be collected over the last decade. I will review the experimental status of elastic electron scattering from the nucleon along with an outlook for future progress.
Nucleon and pion structure with lattice QCD simulations at physical value of the pion mass
Abdel-Rehim, A; Constantinou, M; Dimopoulos, P; Frezzotti, R; Hadjiyiannakou, K; Jansen, K; Kallidonis, Ch; Kostrzewa, B; Koutsou, G; Mangin-Brinet, M; Oehm, M; Rossi, G C; Urbach, C; Wenger, U
2015-01-01
We present results on the nucleon scalar, axial and tensor charges as well as on the momentum fraction, and the helicity and transversity moments. The pion momentum fraction is also presented. The computation of these key observables is carried out using lattice QCD simulations at a physical value of the pion mass. The evaluation is based on gauge configurations generated with two degenerate sea quarks of twisted mass fermions with a clover term. We investigate excited states contributions with the nucleon quantum numbers by analyzing three sink-source time separations. We find that, for the scalar charge, excited states contribute significantly and to a less degree to the nucleon momentum fraction and helicity moment. Our analysis yields a value for the nucleon axial charge agrees with the experimental value and we predict a value of 1.027(62) in the $\\overline{\\text{MS}}$ scheme at 2 GeV for the isovector nucleon tensor charge directly at the physical point. The pion momentum fraction is found to be $\\langl...
Correlations probed in direct two-nucleon removal reactions
Final-state-exclusive momentum distributions of fast, forward-traveling residual nuclei, following two-nucleon removal from fast secondary radioactive beams of projectile nuclei, can and have now been measured. Assuming that the most important reaction mechanism is the sudden direct removal of a pair of nucleons from a set of relatively simple, active shell-model orbital configurations, such distributions were predicted to depend strongly on the total angular momentum I carried by the two nucleons--the final-state spin for spin 0+ projectiles. The sensitivity of these now-accessible observables to specific details of the (correlated) two-nucleon wave functions is of importance. We clarify that it is the total orbital angular momentum L of the two nucleons that is the primary factor in determining the shapes and widths of the calculated momentum distributions. It follows that, with accurate measurements, this dependence upon the L makeup of the two-nucleon wave functions could be used to assess the accuracy of (shell- or many-body-) model predictions of these two-nucleon configurations. By using several tailored examples, with specific combinations of active two-nucleon orbitals, we demonstrate that more-subtle structure aspects may be observed, allowing such reactions to probe and/or confirm the details of theoretical model wave functions.
EM vs Weak Structure Functions in DIS processes
Athar, M Sajjad; Simo, I Ruiz; Vacas, M J Vicente
2013-01-01
We obatin the ratio $F_i^A/F_i^{D}$(i=2,3, A=Be, C, Fe, Pb; D=Deuteron) in the case of weak and electromagnetic nuclear structure functions. For this, relativistic nuclear spectral function which incorporate the effects of Fermi motion, binding and nucleon correlations is used. We also consider the pion and rho meson cloud contributions and shadowing and antishadowing effects.
Deuteron Spin Structure Functions in the Resonance and DIS Regions
S. Kulagin; W. Melnitchouk
2007-10-03
We derive relations between spin-dependent nuclear and nucleon g_1 and g_2 structure functions, valid at all Q^2, and in both the resonance and deep inelastic regions. We apply the formalism to the specific case of the deuteron, which is often used as a source of neutron structure information, and compare the size of the nuclear corrections calculated using exact kinematics and using approximations applicable at large Q^2.
Bound Nucleon Form Factors, Quark-Hadron Duality, and Nuclear EMC Effect
Tsushima, K; Melnitchouk, W; Saitô, K; Thomas, A W
2003-01-01
We discuss the electromagnetic form factors, axial form factors, and structure functions of a bound nucleon in the quark-meson coupling (QMC) model. Free space nucleon form factors are calculated using the improved cloudy bag model (ICBM). After describing finite nuclei and nuclear matter in the quark-based QMC model, we compute the in-medium modification of the bound nucleon form factors in the same framework. Finally, limits on the medium modification of the bound nucleon $F_2$ structure function are obtained using the calculated in-medium electromagnetic form factors and local quark-hadron duality.
Chiral perturbation theory with nucleons
Meissner, U.G.
1991-09-01
I review the constraints posed on the interactions of pions, nucleons and photons by the spontaneously broken chiral symmetry of QCD. The framework to perform these calculations, chiral perturbation theory, is briefly discussed in the meson sector. The method is a simultaneous expansion of the Greens functions in powers of external moments and quark masses around the massless case, the chiral limit. To perform this expansion, use is made of a phenomenological Lagrangian which encodes the Ward-identities and pertinent symmetries of QCD. The concept of chiral power counting is introduced. The main part of the lectures of consists in describing how to include baryons (nucleons) and how the chiral structure is modified by the fact that the nucleon mass in the chiral limit does not vanish. Particular emphasis is put on working out applications to show the strengths and limitations of the methods. Some processes which are discussed are threshold photopion production, low-energy compton scattering off nucleons, {pi}N scattering and the {sigma}-term. The implications of the broken chiral symmetry on the nuclear forces are briefly described. An alternative approach, in which the baryons are treated as very heavy fields, is touched upon.
Chiral perturbation theory with nucleons
I review the constraints posed on the interactions of pions, nucleons and photons by the spontaneously broken chiral symmetry of QCD. The framework to perform these calculations, chiral perturbation theory, is briefly discussed in the meson sector. The method is a simultaneous expansion of the Greens functions in powers of external moments and quark masses around the massless case, the chiral limit. To perform this expansion, use is made of a phenomenological Lagrangian which encodes the Ward-identities and pertinent symmetries of QCD. The concept of chiral power counting is introduced. The main part of the lectures of consists in describing how to include baryons (nucleons) and how the chiral structure is modified by the fact that the nucleon mass in the chiral limit does not vanish. Particular emphasis is put on working out applications to show the strengths and limitations of the methods. Some processes which are discussed are threshold photopion production, low-energy compton scattering off nucleons, πN scattering and the σ-term. The implications of the broken chiral symmetry on the nuclear forces are briefly described. An alternative approach, in which the baryons are treated as very heavy fields, is touched upon
Chiral three-nucleon interactions in ab-initio nuclear structure and reactions
The prediction of nuclear structure and reaction observables based on nuclear Hamiltonians including two- and three-nucleon (NN+3N) interactions derived from chiral effective field theory constitutes a challenging task for ab-initio nuclear theory. In particular, the consistent inclusion of 3N interactions requires formal extensions of the many-body methods and, at the same time, causes a significant increase of the computational cost. This work presents the necessary steps for the inclusion and the subsequent application of 3N interactions in different ab-initio nuclear structure and reaction approaches. The first part is dedicated to the preparation of the chiral nuclear forces before they enter the many-body methods. It addresses the similarity renormalization group (SRG) as a tool to soften the initial chiral interactions and its generalization to consistently include 3N interactions. Moreover, the technically important 3N matrix-element management in a convenient basis for the subsequent many-body methods including an efficient storage scheme is discussed. In addition, a possibility to derive approximative schemes for 3N interactions using normal ordering is presented. In the second part the SRG-evolved chiral NN+3N Hamiltonians are applied in nuclear structure calculations using the importance truncated no-core shell model (IT-NCSM) as well as coupled-cluster theory. The impact of SRG-induced and chiral 3N interactions on ground-state energies and low-energy spectra of different p-shell nuclei is studied, including a sensitivity analysis concerning uncertainties of the chiral interactions in the 12C and 10B spectra. Furthermore, the first ab-initio study of even oxygen isotopes with explicit 3N interactions is presented, and by means of the normal-ordered two-body approximation the ground-state energy systematics of selected closed-shell nuclei throughout the calcium, nickel, and tin isotopic chains are obtained in qualitative agreement with experiment. The third part of this work focuses on 3N interactions in ab-initio nuclear scattering approaches. This includes a detailed discussion of the inclusion of 3N interactions in the no-core shell model combined with the resonating-group method (NCSM/RGM) with emphasis on the ability to treat targets beyond the lightest nuclei. The extended formalism is then applied to nucleon-4He scattering, where the 3N interaction overall improves scattering phase shifts, differential cross sections and analyzing powers. Finally, the no-core shell model with continuum approach, which constitutes a unified ab-initio approach to bound and scattering states resulting from the combination of the NCSM and the NCSM/RGM, is generalized to 3N interactions and applied to the neutron-8Be system to study the impact of the continuum on the 9Be energy levels. The results demonstrate the importance of the consistent treatment of continuum states.
This report summarizes the work on experimental research in intermediate energy nuclear physics carried out by New Mexico State University from April 1, 1994, through March 31, 1996 under a grant from the US Department of Energy. During this period we began phasing out our programs of study of pion-nucleus and pion-nucleon interaction and of nucleon-nucleus charge-exchange reactions, which have been our major focus of the past two or three years. At the same time we continued moving in a new direction of research on studies of the internal structure of nucleons and nuclei in terms of quarks and gluons. The pion and nucleon work has been aimed at improving our understanding of the nature of pion and proton interactions in the nuclear medium and of various aspects of nuclear structure. The studies of the quark-gluon structure of nucleons are aimed at clarifying such problems as the nature of the quark sea and the relation of the nucleon spin to the spins of the quarks within the nucleon, questions which are of a very fundamental nature
NONE
1996-10-01
This report summarizes the work on experimental research in intermediate energy nuclear physics carried out by New Mexico State University from April 1, 1994, through March 31, 1996 under a grant from the US Department of Energy. During this period we began phasing out our programs of study of pion-nucleus and pion-nucleon interaction and of nucleon-nucleus charge-exchange reactions, which have been our major focus of the past two or three years. At the same time we continued moving in a new direction of research on studies of the internal structure of nucleons and nuclei in terms of quarks and gluons. The pion and nucleon work has been aimed at improving our understanding of the nature of pion and proton interactions in the nuclear medium and of various aspects of nuclear structure. The studies of the quark-gluon structure of nucleons are aimed at clarifying such problems as the nature of the quark sea and the relation of the nucleon spin to the spins of the quarks within the nucleon, questions which are of a very fundamental nature.
Purely Functional Structured Programming
Obua, Steven
2010-01-01
The idea of functional programming has played a big role in shaping today's landscape of mainstream programming languages. Another concept that dominates the current programming style is Dijkstra's structured programming. Both concepts have been successfully married, for example in the programming language Scala. This paper proposes how the same can be achieved for structured programming and PURELY functional programming via the notion of LINEAR SCOPE. One advantage of this proposal is that m...
McGraw, John T. (Placitas, NM); Zimmer, Peter C. (Albuquerque, NM); Ackermann, Mark R. (Albuquerque, NM)
2012-01-24
Methods and apparatus for a structure function monitor provide for generation of parameters characterizing a refractive medium. In an embodiment, a structure function monitor acquires images of a pupil plane and an image plane and, from these images, retrieves the phase over an aperture, unwraps the retrieved phase, and analyzes the unwrapped retrieved phase. In an embodiment, analysis yields atmospheric parameters measured at spatial scales from zero to the diameter of a telescope used to collect light from a source.
Colleen Ellis
2010-07-01
The G0 backward angle experiment, completed in Hall C of the Thomas Jefferson National Accelerator Facility (TJNAF), measured parity-violating asymmetries in elastic electron-proton and quasielastic electron-deuteron scattering at Q2 = 0.22 and 0.63 (GeV/c)2. The asymmetries are sensitive to strange quark contributions to currents in the nucleon and the nucleon axial-vector current. The results indicate strange quark contributions of lte 10% of the charge and magnetic nucleon form factors at these four-momentum transfers. This was also the first measurement of the anapole moment effects in the axial-vector current at these four-momentum transfers.
Electromagnetic Structure and Reactions of Few-Nucleon Systems in χEFT
Schiavilla R.
2010-04-01
Full Text Available We summarize our recent work dealing with the construction of the nucleon-nucleon potential and associated electromagnetic currents up to one loop in chiral eﬀective ﬁeld theory (χEFT. The magnetic dipole operators derived from these currents are then used in hybrid calculations of static properties and low-energy radiative capture processes in few-body nuclei. A preliminary set of results are presented for the magnetic moments of the deuteron and trinucleons and thermal neutron captures on p, d, and 3He.
Study of the η' Meson Structure, Width and Interactions with Nucleons at COSY-11
We present results on the isospin dependence of the η' production cross section in nucleon-nucleon collisions, as well as the results of comparative analysis of the invariant mass distributions for the pp → ppη' and pp → ppη reactions in the context of the proton-η and proton-η' interaction. Additionally, the value of the total width of the η' is reported as derived directly from the measurement of the mass distribution and an explanation of the experimental technique used in order to achieve a precision about an order of magnitude better then former experiments is included. (author)
Chromatin Structure and Function
Wolffe, Alan P
1999-01-01
The Third Edition of Chromatin: Structure and Function brings the reader up-to-date with the remarkable progress in chromatin research over the past three years. It has been extensively rewritten to cover new material on chromatin remodeling, histone modification, nuclear compartmentalization, DNA methylation, and transcriptional co-activators and co-repressors. The book is written in a clear and concise fashion, with 60 new illustrations. Chromatin: Structure and Function provides the reader with a concise and coherent account of the nature, structure, and assembly of chromatin and its active
Quark cluster model in the three-nucleon system
The quark cluster model is used to investigate the structure of the three-nucleon systems. The nucleon-nucleon interaction is proposed considering the colour-nucleon clusters and incorporating the quark degrees of freedom. The quark-quark potential in the quark compound bag model agrees with the central force potentials. The confinement potential reduces the short-range repulsion. The colour van der Waals force is determined. Then, the probability of quark clusters in the three-nucleon bound state systems are numerically calculated using realistic nuclear wave functions. The results of the present calculations show that quarks cluster themselves in three-quark systems building the quark cluster model for the trinucleon system. (author)
Lepton-nucleon scattering at high energies
Recent theoretical developments in the field of inelastic lepton-nucleon scattering are reviewed with emphasis on physics at HERA. Structure functions at small Bjorken-x are discussed in detail. Further topics are photoproduction of jets, the gluon densities in proton and photon, charm physics, electroweak processes and the search for new particles and interactions. (orig.)
Spin Structure Functions from Electron Scattering
The spin structure of the nucleon can play a key testing ground for Quantum Chromo-Dynamics (QCD) at wide kinematic ranges from smaller to large four momentum transfer Q2. The pioneering experiments have confirmed several QCD sum rules at high Q2 where a perturbative picture holds. For a full understanding of QCD at various scales, various measurements were made at intermediate and small Q2 region and their interpretation would be a challenging task due to the non-perturbative nature. Jefferson Lab has been one of the major experimental facilities for the spin structure with its polarized electron beams and various polarized targets. A few QCD sum rules have been compared with the measured spin structure functions g1(x, Q2) and g2(x, Q2) at low Q2 and surprising results have been obtained for the spin polarizabilities, ?0 and (delta)LT . As for the proton spin structure functions, the lack of data for g2(x,Q2) structure functions has been complemented with a new experiment at Jefferson Lab, SANE. The results from SANE will provide a better picture of the proton spin structure at a wide kinematic range in x and Q2.
First moment of the flavour octet nucleon parton distribution function using lattice QCD
Alexandrou, C; Dinter, S; Drach, V; Hadjiyiannakou, K; Jansen, K; Koutsou, G; Vaquero, A
2015-01-01
We perform a lattice computation of the flavour octet contribution to the average quark momentum in a nucleon, $\\la x\\ra^{(8)} _{\\mu^2 = 4~\\gev^2 }$. In particular, we fully take the disconnected contributions into account in our analysis for which we use a generalization of the technique developed in \\cite{Dinter:2012tt}. We investigate systematic effects with a particular emphasis on the excited states contamination. We find that in the renormalization free ratio $\\frac{\\la x \\ra^{(3)}}{\\la x \\ra^{(8)}}$ (with $\\la x \\ra^{(3)}$ the non-singlet moment) the excited state contributions cancel to a large extend making this ratio a promising candidate for a comparison to phenomenological analyses. Our final result for this ratio is in agreement with the phenomenological value and we find, including systematic errors, $\\frac{\\la x \\ra^{(3)}}{\\la x \\ra^{(8)}} = 0.39(1)(4)$.
Mathematics for structure functions
Vermaseren, J. A. M.; Moch, S.(Deutsches Elektronensynchrotron DESY, Platanenallee 6, 15738, Zeuthen, Germany)
2000-01-01
We show some of the mathematics that is being developed for the computation of deep inelastic structure functions to three loops. These include harmonic sums, harmonic polylogarithms and a class of difference equations that can be solved with the use of harmonic sums.
A-dependence of weak nuclear structure functions
Effect of nuclear medium on the weak structure functions F2A(x, Q2) and F3A(x, Q2) have been studied using charged current (anti)neutrino deep inelastic scattering on various nuclear targets. Relativistic nuclear spectral function which incorporate Fermi motion, binding and nucleon correlations are used for the calculations. We also consider the pion and rho meson cloud contributions calculated from a microscopic model for meson-nucleus self-energies. Using these structure functions, FiA/Fiproton and FiA/Fideuteron(i=2,3, A=12C, 16O, CH and H2O) are obtained
Parity doubling structure of nucleon at non-zero density in the holographic mean field theory
He Bing-Ran
2014-06-01
Full Text Available We summarize our recent work in which we develope the holographic mean field approach to study the dense baryonic matter in a bottom-up holographic QCD model including baryons and scalar mesons in addition to vector mesons. We first show that, at zero density, the rate of the chiral invariant mass of nucleon is controlled by the ratio of the infrared boundary values of two baryon fields included in the model. Then, at non-zero density, we find that the chiral condensate decreases with the increasing density indicating the partial restoration of the chiral symmetry. Our result shows that the more amount of the proton mass comes from the chiral symmetry breaking, the faster the effective nucleon mass decrease with density.
Results from the forward G0 experiment. Strange quark contribution to the nucleon structure
The G0 experiment is dedicated to the determination of the strange quark contribution to the electric and magnetic nucleon form factors for a large range of momentum transfers between 0.1 to 1 (GeV/c)2. This information is provided by the asymmetries of cross-sections measured with longitudinally polarized electrons in elastic electron-proton scattering and quasi-elastic electron-deuteron scattering. A set of measurements at two different Q2 will allow the complete separation of the electric and magnetic weak, as well as axial nucleon form factors. This report summarizes the physics case, gives details about the dedicated set-up used, and shows the results of the combination of the strange quark contribution in the electric and magnetic form factors of the protons. The experiment was performed at the Jefferson Laboratory, during years 2003 and 2004, and will be completed after backward-angle measurements in 2006, 2007. (orig.)
Measurements of the deuteron elastic structure function
The deuteron elastic structure function A(Q2) has been extracted in the range of 0.7 (le) Q2 (le) 6.0 (GeV/c)2 from cross section measurements of elastic electron-deuteron in coincidence. Measurements of the elastic deuteron electromagnetic form factors offer unique opportunities to test models of short-range aspects of the nucleon-nucleon interaction, meson-exchange currents, isobaric configurations and, quark degrees of freedom. The elastic electron-deuteron cross section is given by dσ/d(Omega) = σM[A(Q2) + B(Q2) tan2(θ/2)] where θ is the electron scattering angle, σM = α2E(prime) cos2 (θ/2)/[4E3 sin4(θ/2)] is the Mott cross section, α is the fine-structure constant, E and E(prime) are the incident and scattered electron energies and Q2 = 4EE(prime) sin2(θ/2) is the four momentum transfer squared. The deuteron elastic structure functions A(Q 2) and B(Q2) are given in terms of the charge, quadrupole and magnetic form factors Fc(Q2), F1(Q2) and Fm(Q2) by A(Q2) = Fc2(Q2) + (8/9)τ2 F12(Q2) + (2/3)τFm2(Q2) and B(Q2) = (4/3)τ(1+τ)Fm2(Q2) and to resolve inconsistencies in previous data sets by measuring elastic electron-deuteron (e-d) cross sections for 0.7 (le) Q2 (le) 6.0 (GeV/c)2
Phenomenology of dark matter-nucleon effective interactions
Catena, Riccardo
2015-01-01
I compare the non-relativistic effective theory of one-body dark matter-nucleon interactions to current dark matter direct detection experiments and neutrino telescope observations, presenting exclusion limits on the coupling constants of the theory. In the analysis of direct detection experiments, I focus on the interference of different dark matter-nucleon interaction operators and on predictions observable at directional detectors. Interpreting neutrino telescope observations, I use new nuclear response functions recently derived through nuclear structure calculations and show that hydrogen is not the most important element in the exclusion limit calculation for the majority of the spin-dependent dark matter-nucleon interaction operators
The experimental techniques related to NN resonance measurements are described. The technique used is the good geometry transmission experiment. The basic idea is to measure the difference in the attenuation factor for the corresponding difference between the total cross sections of N + N interactions for forward and reverse momentum as a function of the solenoid current. 26 references
The three-nucleon bound state with isobaric and pionic degrees of freedom
Wave function components containing a single Δ-isobar are included in the calculation of the three-nucleon bound states. The two-nucleon interaction acts in all partial waves up to total angular momentum I=2. The presence of a Δ-isobar increases the three-nucleon binding energy by about 0.3 MeV, 0.6 MeV repulsion being a dispersive two-body effect, 0.9 MeV attraction arising from the three-nucleon force with intermediate Δ-isobar. The effect of the Δ on the three-nucleon charge and magnetic form factors is investigated. The possibility of treating the Δ-isobar as a dynamic pion-nucleon system in nuclear structure and nuclear-structure corrections beyond single Δ excitation in the coupled channel approach are also discussed
Sinden, Richard R.; E. Pearson, Christopher; N. Potaman, Vladimir; Ussery, David
This chapter discusses the structure and function of DNA. DNA occupies a critical role in cells, because it is the source of all intrinsic genetic information. Chemically, DNA is a very stable molecule, a characteristic important for a macromolecule that may have to persist in an intact form for a...... long period of time before its information is accessed by the cell. Although DNA plays a critical role as an informational storage molecule, it is by no means as unexciting as a computer tape or disk drive. The structure of the DNA described by Watson and Crick in 1953 is a right handed helix of two...
Charge structure of the hadronic final state in deep-inelastic muon-nucleon scattering
Arneodo, M.; Arvidson, A.; Aubert, J. J.; Bedełek, J.; Beaufays, J.; Bee, C. P.; Benchouk, C.; Berghoff, G.; Bird, I.; Blum, D.; Böhm, E.; de Bouard, X.; Brasse, F. W.; Braun, H.; Broll, C.; Brown, S.; Brück, H.; Calen, H.; Chima, J. S.; Ciborowski, J.; Clifft, R.; Coignet, G.; Combley, F.; Coughlan, J.; D'Agostini, G.; Dahlgren, S.; Dengler, F.; Derado, I.; Dreyer, T.; Drees, J.; Düren, M.; Eckardt, V.; Edwards, A.; Edwards, M.; Ernst, T.; Eszes, G.; Favier, J.; Ferrero, M. I.; Figiel, J.; Flauger, W.; Foster, J.; Ftáčnik, J.; Gabathuler, E.; Gajewski, J.; Gamet, R.; Gayler, J.; Geddes, N.; Grafström, P.; Grard, F.; Haas, J.; Hagberg, E.; Hasert, F. J.; Hayman, P.; Heusse, P.; Jaffré, M.; Jachołkowska, A.; Janata, F.; Jancsó, G.; Johnson, A. S.; Kabuss, E. M.; Kellner, G.; Korbel, V.; Krüger, J.; Kullander, S.; Landgraf, U.; Lanske, D.; Loken, J.; Long, K.; Maire, M.; Malecki, P.; Manz, A.; Maselli, S.; Mohr, W.; Montanet, F.; Montgomery, H. E.; Nagy, E.; Nassalski, J.; Norton, P. R.; Oakham, F. G.; Osborne, A. M.; Pascaud, C.; Pawlik, B.; Payre, P.; Peroni, C.; Peschel, H.; Pessard, H.; Pettinghale, J.; Pietrzyk, B.; Pietrzyk, U.; Pönsgen, B.; Pötsch, M.; Renton, P.; Ribarics, P.; Rith, K.; Rondio, E.; Sandacz, A.; Scheer, M.; Schlagböhmer, A.; Schiemann, H.; Schmitz, N.; Schneegans, M.; Schneider, A.; Scholz, M.; Schröder, T.; Schultze, K.; Sloan, T.; Stier, H. E.; Studt, M.; Taylor, G. N.; Thénard, J. M.; Thompson, J. C.; de La Torre, A.; Toth, J.; Urban, L.; Wallucks, W.; Whalley, M.; Wheeler, S.; Williams, W. S. C.; Wimpenny, S. J.; Windmolders, R.; Wolf, G.
1988-09-01
The general charge properties of the hadronic final state produced in μ + p and μ + d interactions at 280 GeV are investigated. Quark charge retention and local charge compensation is observed. The ratio F {2/ n }/ F {2/ p } of the neutron to proton structure function is derived from the measurement of the average hadronic charge in μ d interactions.
Art and Structural Functionality
Franco González, Fidel
2015-01-01
The learning in architecture has a complexity that is a field that must be synthetize aesthetics and functionality. Somehow students are not very effective when they try to mix this terms, in most of the physical topics. To reach this there is a subject “ Applied Physics to Structures “ that shows development of a unification process for learning, crucial to energetic parameters where Energy is the most fundamental parameter for all processes. After the theoretical explanati...
The role of quark exchange in the structure function of lithium nucleus
The quark exchange formalism is formulated to calculate the quark momentum distribution in the iso-scalar lithium nucleus. Then by boosting the nucleus to an infinite momentum frame, the lithium structure function is evaluated at different nucleon “sizes”, i.e., b = 0.7, 0.8, 0.9 and 1 fm and the Bjorken scale (x) values. It is shown that the lithium structure function becomes narrower, and it is pushed to the smaller x values, as the nucleon size is increased. Similar to our previous works for three nucleon systems, the lithium nucleus European muon collaboration (EMC) ratio decreases, as we increase the x and b values and it shows larger effect, with respect to the free nucleon and three nucleons iso-scalar nucleus. On the other hand, present calculation of the EMC ratio for lithium nucleus shows a good agreement with the corresponding NMC data, which is available for 1.4 × 10-4 ≤ x ≤ 0.65. Since the atomic number is still small (A = 6), in this work as usual, we ignore the possibility of simultaneous exchange of quarks between more than two nucleons, which can be important as one moves to the heavy nuclei. Although, according to Hen et al., in the neutron rich nuclei the protons have a greater probability than neutrons to have momentum greater than the Fermi momentum, the three-body contribution may be suppressed. (author)
First moment of the flavour octet nucleon parton distribution function using lattice QCD
Alexandrou, Constantia [Cyprus Univ., Nicosia (Cyprus). Dept. of Physics; The Cyprus Institute, Nicosia (Cyprus). Computation-based Science and Technology Research Center (CaSToRC); Constantinou, Martha; Hadjiyiannakou, Kyriakos; Koutsou, Giannis [Cyprus Univ., Nicosia (Cyprus). Dept. of Physics; Dinter, Simon [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC; Drach, Vincent [Univ. of Southern Denmark, Odense (Denmark). CP3-Origins and the Danish Institute for Advanced Study DIAS; Jansen, Karl [Cyprus Univ., Nicosia (Cyprus). Dept. of Physics; The Cyprus Institute, Nicosia (Cyprus). Computation-based Science and Technology Research Center (CaSToRC); Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC; Vaquero, Alejandro [INFN, Sezione di Milano-Bicocca, Milano (Italy); Collaboration: European Twisted Mass Collaboration
2015-03-15
We perform a lattice computation of the flavour octet contribution to the average quark momentum in a nucleon, left angle x right angle {sup (8)}{sub μ{sup 2}=4} {sub GeV{sup 2}}. In particular, we fully take the disconnected contributions into account in our analysis for which we use a generalization of the technique developed by S. Dinter et. al. (2012). We investigate systematic effects with a particular emphasis on the excited states contamination. We find that in the renormalization free ratio (left angle x right angle {sup (3)})/(left angle x right angle {sup (8)}) (with left angle x right angle {sup (3)} the non-singlet moment) the excited state contributions cancel to a large extend making this ratio a promising candidate for a comparison to phenomenological analyses. Our final result for this ratio is in agreement with the phenomenological value and we find, including systematic errors, (left angle x right angle {sup (3)})/(left angle x right angle {sup (8)})=0.39(1)(4).
Alvioli, M; Kaptari, L P; Mezzetti, C B; Morita, H
2012-01-01
The nucleon momentum distribution n_A(k) for A=2, 3, 4, 16, and 40 nuclei is systematically analyzed in terms of wave functions resulting from advanced solutions of the non-relativistic Schr\\"{o}dinger equation, obtained within different many-body approaches and different realistic nucleon-nucleon (NN) interactions. In order to analyze and understand the frequently addressed question concerning the relationships between the nucleus, n_A(k), and the deuteron, n_D(k), momentum distributions, the spin(S)-isospin (T) structure of few-nucleon systems and complex nuclei is analyzed in terms of realistic NN interactions and many-body approaches. To this end the number of NN pairs in agiven (ST) state, viz. (ST)=(10), (00), (01), and (11), and the contribution of these states to the nucleon momentum distributions, are calculated. It is shown that, apart from the (00) state which has very small effects, all other spin-isospin states contribute to the momentum distribution in a wide range of momenta. It is shown that t...
Flavor asymmetry of the polarized nucleon sea
Nocera, Emanuele Roberto
2014-01-01
We discuss the flavor asymmetry of polarized light antiquarks in the nucleon, $\\Delta\\bar{u}-\\Delta\\bar{d}$. We present a determination of this quantity based on two global QCD analyses of experimental data, DSSV08 and NNPDFpol1.1, in which sea-quark parton distribution functions are determined respectively either from semi-inclusive deep-inelastic scattering or W-boson production data. The latter have become available only very recently, and their effect on the polarized flavor asymmetry is presented here for the first time. We find that the flavor asymmetry of polarized antiquarks in the nucleon is definitely positive, and has almost the same absolute size as its unpolarized counterpart. We compare this result with various theoretical models of the nucleon structure in order to test their validity. We show that some of them are clearly disfavored.
Hard probes of short-range nucleon-nucleon correlations
J. Arrington, D. W. Higinbotham, G. Rosner, M. Sargsian
2012-10-01
The strong interaction of nucleons at short distances leads to a high-momentum component to the nuclear wave function, associated with short-range correlations between nucleons. These short-range, high-momentum structures in nuclei are one of the least well understood aspects of nuclear matter, relating to strength outside of the typical mean-field approaches to calculating the structure of nuclei. While it is difficult to study these short-range components, significant progress has been made over the last decade in determining how to cleanly isolate short-range correlations in nuclei. We have moved from asking if such structures exist, to mapping out their strength in nuclei and studying their microscopic structure. A combination of several different measurements, made possible by high-luminosity and high-energy accelerators, coupled with an improved understanding of the reaction mechanism issues involved in studying these structures, has led to significant progress, and provided significant new information on the nature of these small, highly-excited structures in nuclei. We review the general issues related to short-range correlations, survey recent experiments aimed at probing these short-range structures, and lay out future possibilities to further these studies.
Axial structure of the nucleon in a three-flavor chiral quark-meson model
Nucleon matrix elements of the 0, 3 and 8 flavor components of the axial current are calculated in an SU(3)L x SU(3)R chiral quark-meson model. An extension of the Gell-Mann-Levy lagrangian with effects of meson mixing is used. The cranking projection method is applied. The results are consistent with the recent EMC experiment, reinterpreted by taking into account non-perturbative effects. In particular, I find a sizable value of the flavor singlet axial current matrix element and a negligible contribution of the ss-bar components. 36 refs., 3 figs., 3 tabs. (author)
Rowe, D. J.; McCoy, A. E.; Caprio, M. A.
2016-03-01
The nuclear collective models introduced by Bohr, Mottelson and Rainwater, together with the Mayer-Jensen shell model, have provided the central framework for the development of nuclear physics. This paper reviews the microscopic evolution of the collective models and their underlying foundations. In particular, it is shown that the Bohr-Mottelson models have expressions as macroscopic limits of microscopic models that have precisely defined expressions in many-nucleon quantum mechanics. Understanding collective models in this way is especially useful because it enables the analysis of nuclear properties in terms of them to be revisited and reassessed in the light of their microscopic foundations.
The effect of confinement size on nuclear structure functions
The differences in the structure function of a heavy nucleus, such as iron, compared to a light nucleus, are considered. In the context of QCD, a suggestion that these differences arise as a result of differences in the scale of confinement of the nuclear constituents is investigated. This results in a simple relationship between heavy and light nucleus structure functions which is in reasonable agreement with experiment if the confinement size in iron is around 10-20% greater than in a free nucleon. (author)
Color transparency of nuclear matter to hard-scattered hadrons and the nucleon spectral functions
The cross sections for fixed wide angle exclusive interactions have been known to scale. Namely, the energy dependence of the cross sections can be obtained simply by counting the total number of valence quarks in the initial and the final state particles. The model of S. Brodsky and G. Farrar predicts this scaling behavior by assuming that the scattering hadrons shrink to anomalously small configurations at the point of interaction, while that of V. Landshoff accounts for the scaling by assuming that the interaction goes through large distance, independent constituent collisions. One way of differentiating between the two models is by measuring hadron nucleon scattering cross sections off nuclear targets: if the hadrons are indeed small, as assumed by the small hadron model, there must be some time interval before and after the interaction in which the hadrons remain small. During this period the color fields surrounding the hadrons should be weaker than those in the interior of a normal hadron. Thus, the interactions between these hadrons and the medium should be weaker. This means that the quasi elastic scattering cross section between a hadron and a proton from the nucleus at high momentum transfer should be higher than what has been observed at low energies, and should increase with energy. To test these hypotheses, an experimental program was carried out at Brookhaven National Laboratory, Long Island, New York, in which pp and πp quasi elastic scattering cross sections off lithium, carbon, aluminum, copper and lead, and off hydrogen were observed simultaneously at beam energies of 6 and 10 Gev
Charge structure of the hadronic final state in deep-inelastic muon-nucleon scattering
The general charge properties of the hadronic final state produced in μ+p and μ+d interactions at 280 GeV are investigated. Quark charge retention and local charge compensation is observed. The ratio F2n/F2p of the neutron to proton structure function is derived from the measurement of the average hadronic charge in μd interactions. (orig.)
Meson exchange model for the nucleon-nucleon interaction
Nucleon-nucleon interactions obtained from several models for the field theoretic scattering amplitude are studied. The interaction includes contributions from one-pion and one-omega exchange and from two-pion exchange as calculated in a dispersion theory framework. The resulting interaction is regularized by a cut-off factor obtained by the eikonal approximation to multiple vector meson exchange processes. The Blankenbecler-Sugar equation is solved with the interaction and nucleon-nucleon scattering phase parameters are computed. For the best model good agreement with phenomenological phase parameters is achieved for physically reasonable values of the meson-nucleon coupling constants and the spectral functions needed for the evaluation of the two-pion exchange effects. The deuteron wave function is computed as are the deuteron charge and quadrupole form factors. The interaction is shown to have significantly weaker short-range repulsion than commonly found in local phenomenological potentials and in one-boson exchange models. (Auth.)
Hupin, Guillaume; Quaglioni, Sofia; Navrátil, Petr
2015-05-29
We provide a unified ab initio description of the ^{6}Li ground state and elastic scattering of deuterium (d) on ^{4}He (α) using two- and three-nucleon forces from chiral effective field theory. We analyze the influence of the three-nucleon force and reveal the role of continuum degrees of freedom in shaping the low-lying spectrum of ^{6}Li. The calculation reproduces the empirical binding energy of ^{6}Li, yielding an asymptotic D- to S-state ratio of the ^{6}Li wave function in the d+α configuration of -0.027, in agreement with a determination from ^{6}Li-^{4}He elastic scattering, but overestimates the excitation energy of the 3^{+} state by 350 keV. The bulk of the computed differential cross section is in good agreement with data. These results endorse the application of the present approach to the evaluation of the ^{2}H(α,γ)^{6}Li radiative capture, responsible for the big-bang nucleosynthesis of ^{6}Li. PMID:26066431
Hupin, Guillaume; Quaglioni, Sofia; Navrtil, Petr
2015-05-01
We provide a unified ab initio description of the Li 6 ground state and elastic scattering of deuterium (d ) on He 4 (? ) using two- and three-nucleon forces from chiral effective field theory. We analyze the influence of the three-nucleon force and reveal the role of continuum degrees of freedom in shaping the low-lying spectrum of Li 6 . The calculation reproduces the empirical binding energy of Li 6 , yielding an asymptotic D - to S -state ratio of the Li 6 wave function in the d +? configuration of -0.027 , in agreement with a determination from Li 6 -He 4 elastic scattering, but overestimates the excitation energy of the 3+ state by 350 keV. The bulk of the computed differential cross section is in good agreement with data. These results endorse the application of the present approach to the evaluation of the H 2 (? ,? )Li 6 radiative capture, responsible for the big-bang nucleosynthesis of Li 6 .
The topics presented at the 1989 Joliot-Curie Lectures are reported. Two main subjects were retained: a simplified description of the N-body motion of particles in the quasi-particle configuration; study of the dynamics of nuclear components which are not described by nucleons in their ground state. The following themes were presented: quasiparticles and the Green functions, relativistic aspects of the quasiparticle concept, the dimensions of nucleons in the nuclei and the EMC effect, quarks and gluons in the nuclei, the delta in the nuclei, the strangeness, quasiparticles far from the Fermi sea, diffusion of electrons, stellar evolution and nucleosynthesis
Nuclear medium modification of the F2 structure function
Athar, M Sajjad; Vacas, M J Vicente
2009-01-01
We study the nuclear effects in the electromagnetic structure function $F_{2}(x, Q^2)$ in nuclei in the deep inelastic lepton nucleus scattering process by taking into account Fermi motion, binding, pion and rho meson cloud contributions. Calculations have been done in a local density approximation using relativistic nuclear spectral functions which include nucleon correlations for nuclear matter. The ratios $R_{F2}^A(x,Q^2)=\\frac{2F_2^A(x,Q^2)}{AF_{2}^{Deut}(x,Q^2)}$ are obtained and compared with the recent JLAB results for light nuclei that show a non trivial A dependence.
Nuclear effects in the F3 structure function
Marco, E; Singh, S K
1998-01-01
By using a relativistic framework and accurate nuclear spectral functions we evaluate the ratio F_{3A}/AF_{3N} of deep inelastic neutrino scattering. Parametrizations of this ratio for different values of Q^2 are provided. These results should be useful for taking into account the nuclear effects in analyses of experimental data in neutrino reactions in nuclear targets, and test QCD predictions for the nucleon structure functions. In particular, the size of the nuclear corrections is of the same order of magnitude as the size of the QCD corrections to the Gross-Llewellyn Smith sum rule.
Multiplicities for the semi-inclusive production of each charge state of π± and K± mesons in deep-inelastic scattering are presented as a function of the kinematic quantities x, Q2, z and Phperpendicularto. The multiplicities were extracted from data collected by the HERMES experiment at the HERA storage ring using 27.6 GeV electron and positron beams on a hydrogen or deuterium gas target. These results for identified hadrons constitute the most precise measurement to date, and will significantly enhance our understanding of the proton structure, as well as the fragmentation process in deep-inelastic scattering. Furthermore, the 3D binning at an unprecedented level of precision provides a handle to help disentangle the transverse momentum structure of both. The high level of precision coupled with an intermediate energy regime requires a careful study of the complex interaction between the experimental systematics, theoretical uncertainties, and the applicability of the factorization theorem within the standard framework of leading-twist collinear QCD. This is illustrated by the extraction of the valence quark ratio dν/uν at leading-order in αs. These results show a strong z-dependence below z ∼ 0.30, which could be interpreted as evidence for factorization breaking. This evidence weakens somewhat when isospin invariance of the fragmentation functions is assumed to be broken. Additionally, the multiplicities for the semi-inclusive production of π0 mesons in deep-inelastic scattering are presented as a function of z. These multiplicities were extracted from the same data sample as used for the charged meson results. The neutral pion multiplicity is the same as the average charged pion multiplicity, up to z ∼ 0.70. This is consistent with isospin invariance below z ∼ 0.70. The results at high values of z show strong signs of isospin symmetry breaking.
Models for the pre-equilibrium emission of fast light particles are given based on exciton model. For the light ion reaction, energy spectra of p, d, 3He and alpha emission are given together with the calculation of the angular distribution of nucleon and alpha. A new model for the fast particle emission in heavy-ion reaction is introduced and applied to data analysis. (Auth.)
F Zolfagharpour
2012-03-01
Full Text Available In this paper, we calculate nuclear structure function and EMC effect of 40Ca and 56Fe nuclei. To achive the goals, we consider Fermi motion and binding energy contrbiution in the harmonic oscillator model. In this model, harmonic oscillator parameter ?? related to shells root mean square radius and for free nucleon structure functions, is obtained from GRVs free nucleon structure functions. Then, we calculate differential cross section of lepton scattering from those nuclei at the E=4.8 GeV and E=4.032 GeV. The obtained results show good agreement with available experimental data.
Pion-nucleon vertex function and the one-pion exchange potential
The authors calculate the πNN vertex function from field theory and dispersion relations. It contains no adjustable parameters, the only input being S- and P- waves for ππ→Nanti N. The vertex function, having an effective cut-off mass of 5μ and an rms radius of 0.52 fm, compares well with previous experimental determinations. They find negligible effects from the 3π dressing of the π propagator. The corrected OPEP is significantly different from the uncorrected OPEP for r<1.5 fm. The inclusion of the corrected OPEP in meson exchange potentials will improve agreement with phenomenology. (Auth.)
Jossten, Sylvester Johannes
2013-10-15
Multiplicities for the semi-inclusive production of each charge state of {pi}{sup {+-}} and K{sup {+-}} mesons in deep-inelastic scattering are presented as a function of the kinematic quantities x, Q{sup 2}, z and P{sub h} {sub perpendicular} {sub to}. The multiplicities were extracted from data collected by the HERMES experiment at the HERA storage ring using 27.6 GeV electron and positron beams on a hydrogen or deuterium gas target. These results for identified hadrons constitute the most precise measurement to date, and will significantly enhance our understanding of the proton structure, as well as the fragmentation process in deep-inelastic scattering. Furthermore, the 3D binning at an unprecedented level of precision provides a handle to help disentangle the transverse momentum structure of both. The high level of precision coupled with an intermediate energy regime requires a careful study of the complex interaction between the experimental systematics, theoretical uncertainties, and the applicability of the factorization theorem within the standard framework of leading-twist collinear QCD. This is illustrated by the extraction of the valence quark ratio d{sub {nu}}/u{sub {nu}} at leading-order in {alpha}{sub s}. These results show a strong z-dependence below z {approx} 0.30, which could be interpreted as evidence for factorization breaking. This evidence weakens somewhat when isospin invariance of the fragmentation functions is assumed to be broken. Additionally, the multiplicities for the semi-inclusive production of {pi}{sup 0} mesons in deep-inelastic scattering are presented as a function of z. These multiplicities were extracted from the same data sample as used for the charged meson results. The neutral pion multiplicity is the same as the average charged pion multiplicity, up to z {approx} 0.70. This is consistent with isospin invariance below z {approx} 0.70. The results at high values of z show strong signs of isospin symmetry breaking.
Sum rule measurements of the spin-dependent compton amplitude (nucleon spin structure at Q2 = 0)
Energy weighted integrals of the difference in helicity-dependent photo-production cross sections (σ1/2 - σ3/2) provide information on the nucleon's Spin-dependent Polarizability (γ), and on the spin-dependent part of the asymptotic forward Compton amplitude through the Drell-Hearn-Gerasimov (DHG) sum rule. (The latter forms the Q2=0 limit of recent spin-asymmetry experiments in deep-inelastic lepton-scattering.) There are no direct measurements of σ1/2 or σ3/2, for either the proton or the neutron. Estimates from current π-photo-production multipole analyses, particularly for the proton-neutron difference, are in good agreement with relativistic-l-loop Chiral calculations (χPT) for γ but predict large deviations from the DHG sum rule. Either (a) both the 2-loop corrections to the Spin-Polarizability are large and the existing multipoles are wrong, or (b) modifications to the Drell-Hearn-Gerasimov sum rule are required to fully describe the isospin structure of the nucleon. The helicity-dependent photo-reaction amplitudes, for both the proton and the neutron, will be measured at LEGS from pion-threshold to 470 MeV. In these double-polarization experiments, circularly polarized photons from LEGS will be used with SPHICE, a new frozen-spin target consisting of rvec H · rvec D in the solid phase. Reaction channels will be identified in SASY, a large detector array covering about 80% of 4π. A high degree of symmetry in both target and detector will be used to minimize systematic uncertainties
High energy nucleon incident optical potential by relativistic impulse approximation
The optical potentials by relativistic impulse approximation (RIA) are utilized for the high energy nucleon incidence. The nucleon-nucleon scattering amplitudes are derived from the phase shift and parametrized as a function of the incident nucleon energy. The optical potential by RIA reproduces the experimental data. (author)
The EMC effect and the swelling of nucleons in nuclei
The idea that nucleons could swell in the nuclear medium is issued from the EMC (European Muon Collaboration) effect, the observation that the deep inelastic structure functions in the scaling region differ from the bound nucleon and the free one. The structure function f2(x) for a free nucleon is shown. In this study, x is the Bjorken scaling variable x = Q2/2pq = Q2/2M? where (? q, ?) is the photon four-momentum and p that of the nucleon, and Q2 = q2 - ?2. Grouping all the experimental information the EMC effect divides in four regions, as shown in this paper. Very accurate data are now available from the NMC collaboration (New Muon Collaboration). They show that at very small x the ratio r between the structure function of a bound nucleon and that of a free one, r = F2A(x)/F2N(x), is smaller than unity, owing to the hadronization of the photon, the so-called shadow region. The small-x enhancement, first displayed by EMC and later questioned, is now confirmed, with a more moderate enhancement. This is the so-called antishadow region
Unquenched simulations of four-nucleon interactions
Montvay, I.
2012-10-15
Exploratory simulations of four-nucleon interactions are performed taking into account the dynamical effects of internal nucleon loops. The four-nucleon interactions in the isoscalar and isovector channels are described by Yukawa interactions with auxiliary scalar fields. The nucleon mass and the average field lengths of the scalar fields are determined as a function of nucleon hopping parameter and Yukawa coupling strengths. There are no problems with ''exceptional configurations'' at strong couplings which make quenched simulations unreliable.
Chen, Lie-Wen; Ko, C. M.; Li, Bao-An
2004-01-01
Using an isospin- and momentum-dependent transport model, we study the effects due to the momentum dependence of isoscalar nuclear potential as well as that of symmetry potential on two-nucleon correlation functions and light cluster production in intermediate energy heavy-ion collisions induced by neutron-rich nuclei. It is found that both observables are affected significantly by the momentum dependence of nuclear potential, leading to a reduction of their sensitivity to the stiffness of nu...
Nucleon-nucleon interactions and observables
A class of nucleon-nucleon interactions which are exactly phase equivalent to a given realistic nucleon-nucleon interaction is exhibited. These interactions have the property that the rms radius of the deuteron can be made arbitrarily large without changing the deuteron binding energy or any of the nucleon-nucleon scattering matrix elements. With this construction it is possible to find realistic interactions that do not obey the linear relation between the rms radius and the triplet scattering length observed by Klarsfeld et al.. The interpretation of this result is discussed. copyright 1998 The American Physical Society
The nucleon-alpha potential is calculated using a microscopic model with antisymmetrization effects included from Brink and Boeker, Soper and Serber nucleon-nucleon interactions. The energy dependence of the potentials is also derived
Nucleon-nucleon interaction of a chiral ?-? model at finite temperature
By using the imaginery time Green's function method, the nucleon-nucleon interaction of the chiral ?-? model has been investigated under the one-loop approximation. The effective masses of the pion, ?-meson and ?-meson at finite temperature are given. We have found that the potential well of the nucleon-nucleon interaction becomes shallow as the temperature increases. At a critical temperature Tc (70 MEV) the potential well disappears. (author)
Symmetry Breaking and Quark-Hadron Duality in Structure Functions
We identify conditions under which a summation over nucleon resonances can yield, via quark-hadron duality, parton model results for electromagnetic and neutrino structure functions at large x. While a summation over the lowest even and odd parity multiplets is sufficient to achieve duality in the symmetric quark model, a suppression of transitions to specific final states is required for more realistic cases incorporating SU(6) breaking. We outline several scenarios consistent with duality, discuss their implications for the high Q2 behavior of transition form factors, and illustrate how they can expose the patterns in the flavor-spin dependence of short-distance forces in the strong-QCD limit
The EMC Effect and High Momentum Nucleons in Nuclei
Hen, Or; Higinbotham, Douglas W.; Miller, Gerald A.; Piasetzky, Eli; Weinstein, Lawrence B.
2013-07-01
Recent developments in understanding the influence of the nucleus on deep-inelastic structure functions, the EMC effect, are reviewed. A new data base which expresses ratios of structure functions in terms of the Bjorken variable xA = AQ2/(2MA q0) is presented. Information about two-nucleon short-range correlations (SRC) from experiments is also discussed and the remarkable linear relation between SRC and the EMC effect is reviewed. A convolution model that relates the underlying source of the EMC effect to modification of either the mean-field nucleons or SRC nucleons is presented. It is shown that both approaches are equally successful in describing the current EMC data.
The EMC Effect and High Momentum Nucleons in Nuclei
Hen, Or; Higinbotham, Douglas; Miller, Gerald A; Piasetzky, Eliazer; Weinstein, Lawrence
2013-07-01
Recent developments in understanding the influence of the nucleus on deep-inelastic structure functions, the EMC effect, are reviewed. A new data base which expresses ratios of structure functions in terms of the Bjorken variable x{sub A}=AQ{sup 2}/(2M{sub A}q{sub 0}) is presented. Information about two-nucleon short-range correlations from experiments is also discussed and the remarkable linear relation between short-range correlations and the EMC effect is reviewed. A convolution model that relates the underlying source of the EMC effect to modification of either the mean-field nucleons or the short-range correlated nucleons is presented. It is shown that both approaches are equally successful in describing the current EMC data.
Multipole decomposition of the nucleon transverse phase space
Lorcé, C.; Pasquini, B.
2016-02-01
We present a complete study of the leading-twist quark Wigner distributions in the nucleon, discussing both the T -even and T -odd sectors, along with all the possible configurations of the quark and nucleon polarizations. We identify the basic multipole structures associated with each distribution in the transverse phase space, providing a transparent interpretation of the spin-spin and spin-orbit correlations of quarks and nucleons encoded in these functions. Projecting the multipole parametrization of the Wigner functions onto the transverse-position and the transverse-momentum spaces, we find a natural link with the corresponding multipole parametrizations for the generalized parton distributions and transverse-momentum dependent parton distributions, respectively. Finally, we show results for all the distributions in the transverse phase space, introducing a representation that allows one to visualize simultaneously the multipole structures in both the transverse-position and transverse-momentum spaces.
Multipole decomposition of the nucleon transverse phase space
Lorcé, C
2015-01-01
We present a complete study of the leading-twist quark Wigner distributions in the nucleon, discussing both the $\\mathsf T$-even and $\\mathsf T$-odd sector, along with all the possible configurations of the quark and nucleon polarizations. We identify the basic multipole structures associated with each distribution in the transverse phase space, providing a transparent interpretation of the spin-spin and spin-orbit correlations of quarks and nucleon encoded in these functions. Projecting the multipole parametrization of the Wigner functions onto the transverse-position and the transverse-momentum spaces, we find a natural link with the corresponding multipole parametrizations for the generalized parton distributions and transverse-momentum dependent parton distributions, respectively. Finally, we show results for all the distributions in the transverse phase space, introducing a representation that allows one to visualize simultaneously the multipole structures in both the transverse-position and transverse-m...
The EMC Effect and High Momentum Nucleons in Nuclei
Hen, O; Miller, G A; Piasetzky, E; Weinstein, L B
2013-01-01
Recent developments in understanding the influence of the nucleus on deep-inelastic structure functions, the EMC effect, are reviewed. A new data base which expresses ratios of structure functions in terms of the Bjorken variable $x_A=AQ^2/(2M_A q_0)$ is presented. Information about two-nucleon short-range correlations from experiments is also discussed and the remarkable linear relation between short-range correlations and teh EMC effect is reviewed. A convolution model that relates the underlying source of the EMC effect to modification of either the mean-field nucleons or the short-range correlated nucleons is presented. It is shown that both approaches are equally successful in describing the current EMC data.
Deuteron A(Q2) structure function and the neutron electric form factor
We present new measurements of the deuteron A(Q2) structure function in the momentum transfer region between 1 and 18 fm-2. The accuracy of the data ranges from 2% to 6%. We investigate the sensitivity of A(Q2) to the nucleon-nucleon interaction and to the neutron electric form factor GEn. Our analysis shows that below 20 fm-2 GEn can be inferred from these data with a significantly improved accuracy. The model dependence of this analysis is discussed
Improved chiral nucleon-nucleon potential up to next-to-next-to-next-to-leading order
We present improved nucleon-nucleon potentials derived in chiral effective field theory up to next-to-next-to-next-to-leading order. We argue that the nonlocal momentum-space regulator employed in the two-nucleon potentials of previous works (Nucl. Phys. A 747, 362 (2005) and Phys. Rev. C 68, 041001 (2003)) is not the most efficient choice, in particular since it affects the long-range part of the interaction. We are able to significantly reduce finite-cutoff artefacts by using an appropriate regularization in coordinate space which maintains the analytic structure of the amplitude. The new potentials do not require the additional spectral function regularization employed in (Nucl. Phys. A 747, 362 (2005)) to cut off the short-range components of the two-pion exchange and make use of the low-energy constants ci and di determined from pion-nucleon scattering without any fine tuning. We discuss in detail the construction of the new potentials and convergence of the chiral expansion for two-nucleon observables. We also employ a simple approach for estimating the theoretical uncertainty in few-nucleon calculations from the truncation of the chiral expansion that replaces previous reliance on cutoff variation. (orig.)
Improved chiral nucleon-nucleon potential up to next-to-next-to-next-to-leading order
Epelbaum, E.; Krebs, H. [Ruhr-Universitaet Bochum, Institut fuer Theoretische Physik II, Bochum (Germany); Meissner, U.G. [Universitaet Bonn, Helmholtz-Institut fuer Strahlen- und Kernphysik and Bethe Center for Theoretical Physics, Bonn (Germany); Forschungszentrum Juelich, Institut fuer Kernphysik, Institute for Advanced Simulation, and Juelich Center for Hadron Physics, Juelich (Germany); Forschungszentrum Juelich, JARA - High Performance Computing, Juelich (Germany)
2015-05-15
We present improved nucleon-nucleon potentials derived in chiral effective field theory up to next-to-next-to-next-to-leading order. We argue that the nonlocal momentum-space regulator employed in the two-nucleon potentials of previous works (Nucl. Phys. A 747, 362 (2005) and Phys. Rev. C 68, 041001 (2003)) is not the most efficient choice, in particular since it affects the long-range part of the interaction. We are able to significantly reduce finite-cutoff artefacts by using an appropriate regularization in coordinate space which maintains the analytic structure of the amplitude. The new potentials do not require the additional spectral function regularization employed in (Nucl. Phys. A 747, 362 (2005)) to cut off the short-range components of the two-pion exchange and make use of the low-energy constants c{sub i} and d{sub i} determined from pion-nucleon scattering without any fine tuning. We discuss in detail the construction of the new potentials and convergence of the chiral expansion for two-nucleon observables. We also employ a simple approach for estimating the theoretical uncertainty in few-nucleon calculations from the truncation of the chiral expansion that replaces previous reliance on cutoff variation. (orig.)
A-dependence of weak nuclear structure functions
Haider, H.; Simo, I. Ruiz; Athar, M. Sajjad
2015-05-01
Effect of nuclear medium on the weak structure functions F2A(x , Q2) and F3A(x , Q2) have been studied using charged current (anti)neutrino deep inelastic scattering on various nuclear targets. Relativistic nuclear spectral function which incorporate Fermi motion, binding and nucleon correlations are used for the calculations. We also consider the pion and rho meson cloud contributions calculated from a microscopic model for meson-nucleus self-energies. Using these structure functions, FiA/Fip r o t o n and FiA/Fid e u t e r o n (i=2,3, A=12C, 16O, CH and H2O) are obtained.
A-dependence of weak nuclear structure functions
Haider, H.; Athar, M. Sajjad [Department of Physics, Aligarh Muslim University, Aligarh-202 002 (India); Simo, I. Ruiz [Dipartimento di Fisica, Universitá degli studi di Trento Via Sommarive 14, Povo (Trento) I-38123 (Italy)
2015-05-15
Effect of nuclear medium on the weak structure functions F{sub 2}{sup A}(x, Q{sup 2}) and F{sub 3}{sup A}(x, Q{sup 2}) have been studied using charged current (anti)neutrino deep inelastic scattering on various nuclear targets. Relativistic nuclear spectral function which incorporate Fermi motion, binding and nucleon correlations are used for the calculations. We also consider the pion and rho meson cloud contributions calculated from a microscopic model for meson-nucleus self-energies. Using these structure functions, F{sub i}{sup A}/F{sub i}{sup proton} and F{sub i}{sup A}/F{sub i}{sup deuteron}(i=2,3, A={sup 12}C, {sup 16}O, CH and H{sub 2}O) are obtained.
A-dependence of weak nuclear structure functions
Haider, H; Athar, M Sajjad
2013-01-01
Effect of nuclear medium on the weak structure functions $F_2^A(x,Q^2)$ and $F_3^A(x,Q^2)$ have been studied using charged current (anti)neutrino deep inelastic scattering on various nuclear targets. Relativistic nuclear spectral function which incorporate Fermi motion, binding and nucleon correlations are used for the calculations. We also consider the pion and rho meson cloud contributions calculated from a microscopic model for meson-nucleus self-energies. Using these structure functions, $F_i^A/F_i^{proton}$ and $F_i^A/F_i^{deuteron}$(i=2,3, A=$^{12}C$, $^{16}O$, $CH$ and $H_{2}O$) are obtained.
Dominguez, Roberto; Holmes, Kenneth C.
2011-01-01
Actin is the most abundant protein in most eukaryotic cells. It is highly conserved and participates in more protein-protein interactions than any known protein. These properties, along with its ability to transition between monomeric (G-actin) and filamentous (F-actin) states under the control of nucleotide hydrolysis, ions, and a large number of actin-binding proteins, make actin a critical player in many cellular functions, ranging from cell motility and the maintenance of cell shape and p...
New results from deep inelastic muon-nucleon scattering
New results obtained by three distinct muon-nucleon scattering experiments are reviewed. They concern the F2 structure function measurements, the open and hidden charm production from multimuon events, and the evidence for forward jets and forward protons/antiprotons production from hadronic final states
Probing the transversity spin structure of a nucleon in neutrino-production of a charmed meson
Pire, B; Wagner, J
2016-01-01
Including O(m_c) terms in the coefficient functions and/or O(m_D) twist 3 contributions in the heavy meson distribution amplitudes leads to a non-zero transverse amplitude for exclusive neutrino production of a D pseudoscalar charmed meson on an unpolarized target. We work in the framework of the collinear QCD approach where chiral-odd transversity generalized parton distributions (GPDs) factorize from perturbatively calculable coefficient functions.
Sensitivity to properties of the phi-meson in the nucleon structure in the chiral soliton model
Mukhopadhyay, N.C.; Zhang, L. [Rensselaer Polytechnic Inst., Troy, NY (United States)
1994-04-01
The influence of the {phi}-meson on the nucleon properties in the chiral soliton model is discussed. Properties of the {phi}-meson and its photo- and electroproduction are of fundamental interest to CEBAF and its possible future extension. The quark model assigns {phi} an s{bar s} structure, thus forbidding the radiative decay {phi}{yields}{pi}{sup 0}{gamma}. Experimentally it is also found to be suppressed, yielding a branching fraction of 1.3{times}10{sup {minus}3}. However, {phi}{yields}{rho}{pi} and {phi}{yields}{pi}{sup +}{pi}{sup {minus}}{pi}{sup 0} are not suppressed at all. Thus, it is possible to incorporate the widths of these decays into the framework of the chiral soliton model, by making use of a specific model for the compliance with OZI rule. Such a model is for example, the {omega}-{phi} mixing model. Consequence of this in the context of a chiral soliton model, which builds on the {pi}{rho}{omega}a{sub 1}(f{sub 1}) meson effective Lagrangian, is the context of this report.
Granier, Thierry
Dans ce mmoire est prsente l'analyse, dans le but de l'extraction des fonctions de structure, d'une partie des donnes de diffusion profondment inlastique de muons sur cibles fixes d'hydrogne et de detrium obtenues dans l'exprience NMC (New Muon Collaboration) du CERN. Les fonctions de structure, partir desquelles s'exprime la probabilit de diffusion un certain angle et une certaine nergie, contiennent de l'information sur la structure interne du nuclon, plus prcisment sur la distribution en nergie des quarks l'intrieur de celui-ci. L'tude de la variation des fonctions de structure avec le degr d'inlasticit de la diffusion permet de tester la validit de la chromodynamique quantique, la thorie de jauge des interactions fortes
Nucleon-nucleon theory and phenomenology
Signell, P.
1981-03-01
This project involves five inter-related subprojects: (1) derivation of the intermediate range nucleon-nucleon interaction using a new method that utilizes much shorter and simpler analytic continuation through the unphysical region that lies between the ..pi..N and ..pi pi.. physical regions of the N anti N ..-->.. ..pi pi.. amplitude (with significantly improved accuracy for the nucleon-nucleon interaction); (2) construction of a short range phenomenological potential that, with the theoretical part mentioned above, gives a precise fit to the nucleon-nucleon data and is parameterized for easy use in nucleon calculations; (3) phase shift analyses of the world data below 400 MeV, especially the large amount of very precise data below 20 MeV and the new data near 55 MeV that have never been analyzed properly; (4) the introduction of a K-matrix formulation of the Optimal Polynomial Expansion in order to accelerate convergence of the partial wave series at LAMPF energies; and (5) setting up of a cooperatively evaluated permanent nucleon-nucleon data bank in the 0-1200 MeV range that can be used by all nucleon-nucleon reseachers.
Nucleon-nucleon theory and phenomenology
This project involves five inter-related subprojects: (1) derivation of the intermediate range nucleon-nucleon interaction using a new method that utilizes much shorter and simpler analytic continuation through the unphysical region that lies between the πN and ππ physical regions of the N anti N → ππ amplitude (with significantly improved accuracy for the nucleon-nucleon interaction); (2) construction of a short range phenomenological potential that, with the theoretical part mentioned above, gives a precise fit to the nucleon-nucleon data and is parameterized for easy use in nucleon calculations; (3) phase shift analyses of the world data below 400 MeV, especially the large amount of very precise data below 20 MeV and the new data near 55 MeV that have never been analyzed properly; (4) the introduction of a K-matrix formulation of the Optimal Polynomial Expansion in order to accelerate convergence of the partial wave series at LAMPF energies; and (5) setting up of a cooperatively evaluated permanent nucleon-nucleon data bank in the 0-1200 MeV range that can be used by all nucleon-nucleon reseachers
x- and xi-scaling of the Nuclear Structure Function at Large x
Arrington, J; Averett, T; Baker, O K; De Bever, L; Bochna, C W; Böglin, W; Bray, B; Carlini, R D; Collins, G; Cothran, C D; Crabb, D; Day, D; Dunne, J A; Dutta, D; Ent, R; Filippone, B W; Honegger, A; Hughes, E W; Jensen, J; Jourdan, J; Keppel, C E; Koltenuk, D M; Lindgren, R; Lung, A; Mack, D J; McCarthy, J; McKeown, R D; Meekins, D G; Mitchell, J H; Mkrtchyan, H G; Niculescu, G; Niculescu, I; Petitjean, T; Rondon, Oscar A; Sick, I; Smith, C; Terburg, B; Vulcan, W F; Wood, S A; Yan, C; Zhao, J; Zihlmann, B
2001-01-01
Inclusive electron scattering data are presented for ^2H and Fe targets at an incident electron energy of 4.045 GeV for a range of momentum transfers from Q^2 = 1 to 7 (GeV/c)^2. Data were taken at Jefferson Laboratory for low values of energy loss, corresponding to values of Bjorken x greater than or near 1. The structure functions do not show scaling in x in this range, where inelastic scattering is not expected to dominate the cross section. The data do show scaling, however, in the Nachtmann variable \\xi. This scaling may be the result of Bloom Gilman duality in the nucleon structure function combined with the Fermi motion of the nucleons in the nucleus. The resulting extension of scaling to larger values of \\xi opens up the possibility of accessing nuclear structure functions in the high-x region at lower values of Q^2 than previously believed.
Transversity of quarks in a nucleon
K Bora; D K Choudhury
2003-11-01
The transversity distribution of quarks in a nucleon is one of the three fundamental distributions, that characterize nucleon’s properties in hard scattering processes at leading twist (twist 2). It measures the distribution of quark transverse spin in a nucleon polarized transverse to its (inﬁnite) momentum. It is a chiral-odd twist-two distribution function – gluons do not couple to it. Quarks in a nucleon/hadron are relativistically bound and transversity is a measure of the relativistic nature of bound quarks in a nucleon. In this work, we review some important aspects of this less familiar distribution function which has not been measured experimentally so far.
Structure functions at large x
Zhang, Z
2002-01-01
Structure function data together with other measurements from fixed-target deep inelastic scattering and hadron-hadron collider experiments which contribute to our knowledge of the parton density functions are reviewed. The inclusive cross-section measurements of neutral and charged current interactions at HERA are presented and their impact on the parton density functions is discussed. Future prospects for an improved knowledge of the parton density functions at large x are briefly mentioned.
Neutrino Production of a Charmed Meson and the Transverse Spin Structure of the Nucleon.
Pire, B; Szymanowski, L
2015-08-28
We calculate the amplitude for exclusive neutrino production of a charmed meson on an unpolarized target in the collinear QCD approach, where generalized parton distributions (GPDs) factorize from perturbatively calculable coefficient functions. We demonstrate that the transversity chiral odd GPDs contribute to the transverse cross section if the hard amplitude is calculated up to order m_{c}/Q. We show how to access these GPDs through the azimuthal dependence of the νN→μ^{-}D^{+}N differential cross section. PMID:26371643
Nucleon spin-flavor structure in the SU(3)-breaking chiral quark model
The SU(3) symmetric chiral quark model, which describes interactions between quarks, gluons, and the Goldstone bosons, explains reasonably well many aspects of the flavor and spin structure of the proton, except for the values of f3/f8 and ?3/?8. Introducing the SU(3)-breaking effect suggested by the mass difference between the strange and nonstrange quarks, we find that this discrepancy can be removed and better overall agreement obtained. copyright 1997 The American Physical Society
The Jlab Upgrade - Nucleon Studies with CLAS12
An overview is presented on the program to study the nucleon structure at the 12 GeV Jlab Upgrade using the CLAS12 detector. The focus is on deeply virtual exclusive processes to access the generalized parton distributions, semi-inclusive processes to study transveresx momentum-dependent distributions functions, and inclusive spin structure functions and resonance transition form factors at high Q2 and with high precision
Neutron-star matter within the energy-density functional theory and neutron-star structure
In this lecture, we will present some nucleonic equations of state of neutron-star matter calculated within the nuclear energy-density functional theory using generalized Skyrme functionals developed by the Brussels-Montreal collaboration. These equations of state provide a consistent description of all regions of a neutron star. The global structure of neutron stars predicted by these equations of state will be discussed in connection with recent astrophysical observations
Hidden Color and the b1 Structure Function of the Deuteron
The b1 structure function is an observable feature of a spin-1 system sensitive to non-nucleonic components of the target nuclear wave function. A simple model for hidden-color, six-quark configurations is proposed and found to give substantial contributions for values of x > 0.2. Good agreement with Hermes data is obtained. Predictions are made for an upcoming JLab experiment. (author)
Neutron-star matter within the energy-density functional theory and neutron-star structure
Fantina, A. F.; Chamel, N.; Goriely, S. [Institut d' Astronomie et d' Astrophysique, CP226, Université Libre de Bruxelles (ULB), 1050 Brussels (Belgium); Pearson, J. M. [Dépt. de Physique, Université de Montréal, Montréal (Québec), H3C 3J7 (Canada)
2015-02-24
In this lecture, we will present some nucleonic equations of state of neutron-star matter calculated within the nuclear energy-density functional theory using generalized Skyrme functionals developed by the Brussels-Montreal collaboration. These equations of state provide a consistent description of all regions of a neutron star. The global structure of neutron stars predicted by these equations of state will be discussed in connection with recent astrophysical observations.
Chiral odd structure functions from a chiral soliton
We calculate the chiral odd quark distributions and the corresponding structure functions hT(x,Q2) and hL(x,Q2) within the Nambu endash Jona-Lasinio chiral soliton model for the nucleon. The Q2 evolution of the twist-2 contributions is performed according to the standard GLAP formalism while the twist-3 piece bar hL(x) is evolved according to the large NC scheme. We carry out a comparison between the chiral odd structure functions of the proton and the neutron. At the low model scale (Q02) we find that the leading twist effective quark distributions f1(q)(x,Q02), g1(q)(x,Q02) and hT(q)(x,Q02) satisfy Soffer close-quote s inequality for both quark flavors q=u,d. copyright 1998 The American Physical Society
Nuclear structure functions in carbon near x=1
Data from deep inelastic scattering of 200 GeV muons on a carbon target with squared four-momentum transfer 52 GeV2≤Q2≤200 GeV2 were analysed in the region of the Bjorken variable close to x=1, which is the kinematic limit for scattering on a free nucleon. At this value of x, the carbon structure function is found to be F2C∼1.2.10-4. The x dependence of the structure function for x>0.8 is well described by an exponential F2C∝exp(-sx) with s=16.5±0.6. (orig.)
Orbital angular momentum in the nucleons
Lorcé, Cédric(IPNO, Université Paris-Sud, CNRS/IN2P3, Orsay, 91406, France)
2014-01-01
In the last decade, it has been realized that the orbital angular momentum of partons inside the nucleon plays a major role. It contributes significantly to nucleon properties and is at the origin of many asymmetries observed in spin physics. It is therefore of paramount importance to determine this quantity if we want to understand the nucleon internal structure and experimental observables. This triggered numerous discussions and controversies about the proper definition of orbital angular ...
Nucleon Resonance Structure from Exclusive Meson Electroproduction with CLAS and CLAS12
The CLAS detector at Jefferson Lab is a unique instrument, which has provided the lion's share of the world's data on meson photo- and electroproduction in the resonance excitation region. The electroexcitation amplitudes for the low-lying resonances P33(1232), P11(1440), D13(1520), and S11(1535) were determined over a wide range of Q22 in a comprehensive analysis of exclusive single-meson (π+n,π0p) reactions in the electroproduction off protons. Further, CLAS was able to precisely measure π+π−p electroproduction differential cross sections provided by the nearly full kinematic coverage of the detector. The electrocouplings of the P11(1440) and D13(1520) excited states are determined from the exclusive-π+π−p reaction. Consistent results on the electrocouplings from two-independent analyses (single- and double-pion electroproduction) have provided compelling evidence for the reliable extraction of the N⁎ electrocouplings. Preliminary results on the electrocouplings of the S31(1620), S11(1650), D33(1700), and P13(1720) states have recently become available. Theoretical analyses of these results have revealed that there are two major contributions to the resonance structure: a) an internal quark core and b) an external meson-baryon cloud. These CLAS results have had considerable impact on QCD-based studies on N⁎ structure and in the search for manifestations of the dynamical masses of the dressed quarks. Future CLAS12 N⁎ structure studies at high photon virtualities will considerably extend our capabilities in exploring the nature of confinement in baryons
Metallothioneins: Structure and Functions.
Dziegiel, Piotr; Pula, Bartosz; Kobierzycki, Christopher; Stasiolek, Mariusz; Podhorska-Okolow, Marzenna
2016-01-01
All metallothioneins (MTs) possess a highly conserved amino acid sequence and present only a few structural changes even when isolated from different animal species. In mammals, a single MT molecule is made up of 61-68 amino acids, depending on the isoform (the MT-1, MT-2, and MT-4 isoforms consist of 61-62 amino acids, whereas the MT-3 isoform comprises 68 amino acids), and the protein sequence is composed of up to 20 cysteine (Cys) residues (Vasak 2005; Vasak and Meloni 2011). Furthermore, in mammals, no aromatic amino acids are found in the MT molecules. Protein sequencing has revealed that the MT molecule is a single polypeptide chain, in which the Cys residues are organized in the sequences Cys-X-Cys, Cys-X-X-Cys, and Cys-Cys, where "X" denotes an amino acid other than Cys (Kojima et al. 1976; Huang and Yoshida 1977). The Cys residues are the metal-binding domains of the MT molecule, in which they are juxtaposed with lysine (Lys) and arginine (Arg) amino acid residues and arranged in two thiol-rich sites designated domains α and β (Fig. 2.1). The two metal-binding domains are separated by a non-cysteine-containing sequence often designated as the spacer or linker (Zangger et al. 2001; Babula et al. 2012). The α-domain consists of amino acids 31-68 and is located on the C-terminal edge, whereas the N-terminal β-domain contains amino acids 1-30 (Zangger et al. 2001; Dziegiel 2004). It has been demonstrated that the α-domain is capable of binding up to four, and the β-domain up to three, bivalent metal ions such as zinc, cadmium, mercury, or lead (Coyle et al. 2002b; Duncan et al. 2006). The part of the protein with no bound metal ions is termed apo-metallothionein (apo-MT) or thionein (Coyle et al. 2002b). Metallothioneins are also capable of reacting with up to 12 univalent metal ions (Palmiter 1998; Coyle et al. 2002b). Zinc ions, which naturally occur in the organism, are regarded as the main binding partner of apo-MT. However, other nonessential metal ions occurring pathologically in the organism-such as lead, copper, cadmium, mercury, platinum, chromate, bismuth, and silver-often possess higher affinity to the apo-MT-binding sites (Nordberg and Nordberg 2000; Ngu and Stillman 2009; Ngu et al. 2010b; Gumulec et al. 2011; Babula et al. 2012). So far, only iron ions (Fe(2+)) have been identified to possess lower affinity to the metal-binding sites of the apo-MT domains (Foster and Robinson 2011). Interestingly, only a small proportion of MT molecules was found bound to zinc ions in various organisms. In rat tissues, apo-MT has been shown to constitute up to 54 % of the total amount of MT, whereas higher apo-MT levels were detected in rat cancer cells (Yang et al. 2001). Recent studies have also identified small amounts of sulfide ligands bound to recombinant MT-1 and MT-4 proteins overexpressed in Escherichia coli (Capdevila et al. 2005; Tio et al. 2006). Nevertheless, studies analyzing MT proteins in the cytoplasm of mammalian cells have failed to detect sulfide ligands bound to their molecules (Mounicou et al. 2010). PMID:26847564
Tensor-polarized structure functions: Tensor structure of deuteron in 2020's
We explain spin structure for a spin-one hadron, in which there are new structure functions, in addition to the ones (F1, F2, g1, g2) which exist for the spin-1/2 nucleon, associated with its tensor structure. The new structure functions are b1, b2, b3, and b4 in deep inelastic scattering of a charged-lepton from a spin-one hadron such as the deuteron. Among them, twist- two functions are related by the Callan-Gross type relation b2 = 2xb1 in the Bjorken scaling limit. First, these new structure functions are introduced, and useful formulae are derived for projection operators of b1-4 from a hadron tensor Wμν. Second, a sum rule is explained for b1, and possible tensor-polarized distributions are discussed by using HERMES data in order to propose future experimental measurements and to compare them with theoretical models. A proposal was approved to measure b1 at the Thomas Jefferson National Accelerator Facility (JLab), so that much progress is expected for b1 in the near future. Third, formalisms of polarized proton-deuteron Drell-Yan processes are explained for probing especially tensor- polarized antiquark distributions, which were suggested by the HERMES data. The studies of the tensor-polarized structure functions will open a new era in 2020's for tensor-structure studies in terms of quark and gluon degrees of freedom, which are very different from ordinary descriptions in terms of nucleons and mesons
Nuclear Structure Functions at Low-$x$ in a Holographic Approach
Agozzino, L; Colangelo, P
2014-01-01
Nuclear effects in deep inelastic scattering at low$-x$ are phenomenologically described changing the typical dynamical and/or kinematical scales characterizing the free nucleon case. In a holographic approach, this rescaling is an analytical property of the computed structure function $F_2(x,Q^2)$. This function is given by the sum of a conformal term and of a contribution due to quark confinement, depending on IR hard-wall parameter $z_0$ and on the mean square distances, related to a parameter $Q^\\prime$, among quarks and gluons in the target. The holographic structure function per nucleon in a nucleus $A$ is evaluated showing that a rescaling of the typical nucleon size, $z_0$ and $Q^\\prime$, due to nuclear binding, can be reabsorbed in a $Q^2$-rescaling scheme. The difference between neutron and proton structure functions and the effects of the longitudinal structure functions can also be taken into account. The obtained theoretical results favourably compare with the experimental data.
Measurement of the Proton and Deuteron Spin Structure Functions G1 and G2
The SLAC experiment E155 was a deep-inelastic scattering experiment that scattered polarized electrons off polarized proton and deuteron targets in the effort to measure precisely the proton and deuteron spin structure functions. The nucleon structure functions g1 and g2 are important quantities that help test our present models of nucleon structure. Such information can help quantify the constituent contributions to the nucleon spin. The structure functions g1p and G1d have been measured over the kinematic range 0.01 (le) x (le) 0.9 and 1 (le) Q2 (le) 40 GeV2 by scattering 48.4 GeV longitudinally polarized electrons off longitudinally polarized protons and deuterons. In addition, the structure functions g2p and g2d have been measured over the kinematic range 0.01 (le) x (le) 0.7 and 1 (le) Q2 (le) 17 GeV2 by scattering 38.8 GeV longitudinally polarized electrons off transversely polarized protons and deuterons. The measurements of g1 confirm the Bjorken sum rule and find the net quark polarization to be ΔΣ = 0.23 ± 0.04 ± 0.6 while g2 is found to be consistent with the g2WW model
Twist-2 Generalized TMDs and the Spin/Orbital Structure of the Nucleon
Kanazawa, K; Metz, A; Pasquini, B; Schlegel, M
2014-01-01
Generalized transverse-momentum dependent parton distributions (GTMDs) encode the most general parton structure of hadrons. Here we focus on two twist-2 GTMDs which are denoted by $F_{1,4}$ and $G_{1,1}$ in parts of the literature. As already shown previously, both GTMDs have a close relation to orbital angular momentum of partons inside a hadron. However, recently even the mere existence of $F_{1,4}$ and $G_{1,1}$ has been doubted. We explain why this claim does not hold. We support our model-independent considerations by calculating the two GTMDs in the scalar diquark model and in the quark-target model, where we also explicitly check the relation to orbital angular momentum. In addition, we compute $F_{1,4}$ and $G_{1,1}$ at large transverse momentum in perturbative Quantum Chromodynamics and show that they are nonzero.
In the framework of the Quantum Chromodynamics (QCD), the nucleon is described as being composed of three valence quarks surrounded by a sea of virtual quark-antiquark pairs and gluons. If the role of this virtual sea in the nucleon properties is inferred to be important, this contribution is still poorly understood. In this context, we study the role of the strange quarks in the nucleon since this is the lightest quark flavor of the sea with no valence contribution. We are determining its contribution to the charge and magnetization distributions in the nucleon via parity violation experiments. The measurement is performed by elastically scattering polarized electrons from nucleon target. A world wide program in which the G0 experiment takes place has been performing for a decade. The G0 experiment and the analysis of the results from its forward angles phase are the topics of this thesis. This document presents the physics case of the strangeness content of the nucleon (mass, spin, impulsion). It describes also the formalism related to the electroweak probe and the form factors, and then the principle of parity violating asymmetry measurement. The G0 experimental setup, which was built and installed in the Hall C of the Jefferson Laboratory (Usa), is detailed. This set-up was designed for the measurement of asymmetries of the order of 10-6 with an overall relative uncertainty better than 10 %, over a momentum transfer range 0.1-1 (GeV/c)2. The various steps of the data analysis are exposed. They have allowed us to start from measured counting rates to reach parity violating physics asymmetries. This required a careful treatment of the various sources of systematical errors which is discussed extensively. Finally the results from the G0 forward angle measurement, its comparison with others experiments and with theoretical models, are presented. They support a non null strange quark contribution. (author)
First measurement of the gluon polarisation in the nucleon using D mesons at COMPASS
von Hodenberg, Martin
2005-01-01
The complicated structure of the nucleon has been studied with great success in deep-inelastic lepton-nucleon scattering (DIS) experiments at CERN, SLAC and DESY. As a result the unpolarised structure functions have been measured accurately over a wide kinematic range. From these measurements it is possible to determine the gluon density in the nucleon with good accuracy via a so-called QCD fit. In the case of the spin structure of the nucleon the situation is different. Even after decades of experimental and theoretical efforts it remains to be understood how the spin of the nucleon of 1/2 in units of h-bar is to be accounted for in terms of contributions from the quarks and gluons inside the nucleon. Of particular interest is the question whether the polarised gluon density can explain the unexpected smallness of the quark contribution to the nucleon spin. The QCD fit, which worked well in the unpolarised case, yields a polarised gluon density Delta G which is only badly constrained. This is due to the fact...
Strangeness in proton and properties of nucleons in nuclear matter revisited
Chandar, A; Chakrabarti, B
2013-01-01
The properties of the nucleons in nuclear medium have been investigated in the context of the flux tube model incorporating strangeness $(s\\bar{s})$ contribution to proton structure in conformity with the experimental indication. Proton is described as a pentaquark system with strange quark contribution whereas neutron is described in three quark configuration. The Quasi particle model of diquark is used to describe the structures of the nucleons. Modifications of the properties like swelling, mass, incompressibility, ratio of the structure functions ($\\frac{F_{2}^{n}(x)}{F_{2}^{p}(x)}$), Gottfried Sum rule for nucleons in nuclear medium have been studied and significant effects have been observed. It has been suggested that the change of the size degree of freedom of the nucleon in the nuclear medium plays an important role in describing the properties in medium. The results are discussed in detail and compared with existing experimental and theoretical predictions. Some interesting observations are made.
Nucleon mass dependence of the central nucleon-nucleon potential
Higa, Renato; Robilotta, Manoel Roberto [Sao Paulo Univ. (USP), SP (Brazil). Inst. de Fisica
2000-07-01
Full text follows: In this work we analyse the nucleon mass dependence of the central component of the nucleon-nucleon potential at large distances, derived from a relativistic effective chiral Lagrangian. This component is directly related to the nucleon scalar form factor and describes the energy density of its mesonic cloud. Results considering only pionic processes, consistent with the Argonne potential, show that the heavy baryon limit is about 30% larger than those with the nucleon mass at its experimental value, and therefore to have realistic descriptions of the NN system this mass must remain finite. Further discussions concerning the delta resonance as well as the strangeness sector, due to the exchange of two uncorrelated kaons, is also presented. (author)
Spin observables in nucleon-nucleus scattering
The curse of inelastic nucleon scattering and charge exchange has always been the enormous complexity of the nucleon-nucleon (N-N) interaction. This complexity, however, can also be viewed as the ultimate promise of nucleons as probes of nuclear structure. Given an adequate theoretical basis, inelastic nucleon scattering is capable of providing information not obtainable with other probes. Recently a revolution of experimental technique has taken place that makes it desirable to re-examine the question of what physics is ultimately obtainable from inelastic nucleon scattering. It is now feasible to perform complete polarization transfer (PT) experiments for inelastic proton scattering with high efficiency and excellent energy resolution. Programs to measure PT obsevables are underway at several laboratories, and results are beginning to appear. Objectives of this presentation are to examine how such experiments are done, and what physics is presently obtained and may ultimately be learned from them
This report details progress toward completion of a long-term pion-nucleon partial wave analysis, summarizing results and conclusions to date. The report also discussed progress in using partial wave and resonance parameter results to test dynamical models of the baryon and in better understanding interquark forces within baryons
This report outlines the progress made in the past 15 months toward completion of a long-term pion-nucleon partial wave analysis in collaboration with R.E. Cuthosky at Carnegie-Mellon University. The report details other theoretical work done during this time period, including work on the Table of Particle Properties, 1982
Nucleon Spin - Results from Jefferson Lab
Kuhn, Sebastian
2013-10-01
Over thirty years after the first experiments probed the spin structure of the nucleon, the pace of experimental and theoretical exploration of this subject keeps increasing. During its fifteen-year run with beam energies up to 6 GeV, Jefferson Lab has made many important contributions to this field - from measurements of the inclusive spin structure functions of the proton and the neutron over a wide kinematic range to seminal experiments accessing the three-dimensional nucleon spin structure through Generalized Parton Distributions and Transverse Momentum Dependent structure functions. An even brighter future lies ahead - after the 12 GeV upgrade, Jefferson Lab will completely map the spin-dependent parton distribution functions for all quark flavors in the valence region. In this talk, I will present an overview of this program, with special emphasis on recent and forthcoming results from the 6 GeV run and a glimpse of the future program with 12 GeV. Supported by DOE grant DE-FG02-96ER40960.
The triton with long-range chiral N3LO three nucleon forces
Skibinski, R; Topolnicki, K; Witala, H; Epelbaum, E; Gloeckle, W; Krebs, H; Nogga, A; Kamada, H
2011-01-01
Long-range contributions to the three-nucleon force that have been recently worked out in chiral effective field theory at next-to-next-to-next-to-leading order are for the first time included in the triton and the doublet nucleon-deuteron scattering length calculations. The strengths of the two short-range terms available at this order in the chiral expansion are determined from the triton binding energy and the neutron-deuteron doublet scattering length. The structure of the resulting three-nucleon force is explored and effects for the two-nucleon correlation function in the triton are investigated. Expectation values of the individual contributions to the three-nucleon force in the triton are found to be in the range from a few 100 keV to about 1 MeV. Our study demonstrates that the very complicated operator structure of the novel chiral three-nucleon forces can be successively implemented in three-nucleon Faddeev calculations.
Two-particle correlation functions were measured for the emission of protons, deuterons, tritons, ?, and lithium fragment at small relative momenta in 40Ar-induced reactions on 197Au at 25 MeV/nucleon. Based on three-body trajectory calculations the emission time scales for the particles were extracted from p-d, d-d, t-t, and lithium-lithium correlation functions.The mean emission time was found to decrease with increasing sum of the kinetic energies of the particle in a correlated pairs, indicating the emission of more energetic particles at earlier stages of the reaction than at later stages. The time scale for the emission of lithium fragments emission suggests that sequential binary disassembly occurs in 40Ar+197Au reaction at MeV/nucleon. The mean emission temperatures of 3.5+1.3-0.8 and 3.60.4 MeV were also extracted from the relative populations of the excited and ground states of the respective emitted nuclides 8Be and 4He. (orig.)
Direct instantons in QCD nucleon sum rules
Forkel, H; Forkel, Hilmar; Banerjee, Manoj K.
1993-01-01
We study the role of direct (i.e. small-scale) instantons in QCD correlation functions for the nucleon. They generate sizeable, nonperturbative corrections to the conventional operator product expansion, which improve the quality of both QCD nucleon sum rules and cure the long-standing stability problem, in particular, of the chirally odd sum-rule.
Nucleon momentum and density distributions of nuclei
In the framework of recently suggested density coherent fluctuations model the nucleon momentum and density distributions are examined. Nucleon momentum and density distributions are expressed in terms of the fluctuation's function, experimentally obtainable from the elastic electron-nuclei scattering. (author)
Spin-orbit correlations in the nucleon
Lorcé, Cédric
2014-01-01
We investigate the correlations between the quark spin and orbital angular momentum inside the nucleon. Similarly to the Ji relation, we show that these correlations can be expressed in terms of specific moments of measurable parton distributions. This provides a whole new piece of information about the partonic structure of the nucleon.
Avakian, H; Hasch, D; Schweitzer, P
2012-01-01
The three-dimensional nucleon structure is central to many theoretical and experimental activities, and research in this field has seen many advances in the last two decades, addressing fundamental questions such as the orbital motion of quarks and gluons inside the nucleons, their spatial distribution, and the correlation between spin and intrinsic motion. A real three-dimensional imaging of the nucleon as a composite object, both in momentum and coordinate space, is slowly emerging. This book presents lectures and seminars from the Enrico Fermi School: Three-Dimensional Partonic Structure of the Nucleon, held in Varenna, Italy, in June and July 2011. The topics covered include: partonic distributions, fragmentation functions and factorization in QCD; theory of transverse momentum dependent partonic distributions (TMDs) and generalized partonic distributions (GPDs); experimental methods in studies of hard scattering processes; extraction of TMDs and GPDs from data; analysis tools for azimuthal asymmetries; ...
Structure functions and parton distributions
Martin, A.D.; Stirling, W.J. [Univ. of Durham (United Kingdom); Roberts, R.G. [Rutherford Appleton Lab., Chilton, Didcot (United Kingdom)
1995-07-01
The MRS parton distribution analysis is described. The latest sets are shown to give an excellent description of a wide range of deep-inelastic and other hard scattering data. Two important theoretical issues-the behavior of the distributions at small x and the flavor structure of the quark sea-are discussed in detail. A comparison with the new structure function data from HERA is made, and the outlook for the future is discussed.
Nucleon-Nucleon Scattering in a Three Dimensional Approach
Fachruddin, I; Glöckle, W; Elster, Ch.
2000-01-01
The nucleon-nucleon (NN) t-matrix is calculated directly as function of two vector momenta for different realistic NN potentials. To facilitate this a formalism is developed for solving the two-nucleon Lippmann-Schwinger equation in momentum space without employing a partial wave decomposition. The total spin is treated in a helicity representation. Two different realistic NN interactions, one defined in momentum space and one in coordinate space, are presented in a form suited for this formulation. The angular and momentum dependence of the full amplitude is studied and displayed. A partial wave decomposition of the full amplitude it carried out to compare the presented results with the well known phase shifts provided by those interactions.
Dynamical rescaling, the EMC effect and universality of hadron structure functions
Data are compared on the EMC effect, with the hypothesis that the quark confinement size increases in going from a free nucleon to a nucleus. In QCD a dynamical rescaling is predicted: Q2 variation of the distribution function in a given target parallels the dependence on confinement size, R, at fixed Q2. Thus a dynamical scale invariance obtains when both R and Q2 are varied, yielding the dynamical rescaling relation F2sup(A)(x, Q2) = F2sup(N)(x, zetaQ2) where zeta > 1 is predicted for any nucleus and is a function of the confinement size. Data on 12 nuclei agree with this, implying that confinement size is governed by nuclear density. The formalism is tested by relating the pion and nucleon structure functions. (author)
Nuclear Dependence in Weak Structure Functions and the Determination of Weak Mixing Angle
Athar, M Sajjad; Simo, I Ruiz; Vacas, M J Vicente
2013-01-01
We have studied nuclear medium effects in the weak structure functions $F^A_2(x)$ and $F^A_3(x)$ and in the extraction of weak mixing angle using Paschos Wolfenstein(PW) relation. We have modified the PW relation for nonisoscalar nuclear target. We have incorporated the medium effects like Pauli blocking, Fermi motion, nuclear binding energy, nucleon correlations, pion $\\&$ rho cloud contributions, and shadowing and antishadowing effects.
On the resumed gluon anomalous dimension and structure functions at small x
The impact of the recently evaluated open-quotes irreducibleclose quotes contributions to the resummed next-to-leading logarithmic small-x anomalous dimension γgg is evaluated for the unpolarized parton densities and structure functions of the nucleon. These new terms diminish the gluon distribution and are found to overcompensate the enhancement caused by the resummed leading logarithmic small-x anomalous dimension and the quarkonic contributions beyond next-to-leading order. copyright 1997 The American Physical Society
Production cross sections of dimuons and experimental analysis of hadronic structure functions
Analysis, by spectrometry (spectrometer Lezard NA3), of the particle structure (nucleons, mesons) and determination of a multiplicative factor (nearly 2) for the Drell-Yan cross section. Description of the experimental apparatus, production of dimuons on hydrogen and heavy nuclei (platinum), exploration of the nucleon (by inelastic diffusion of leptons, especially neutrinos, and use of the parton model), utilization of the Drell-Yan mechanism describing the production of a continuous spectrum of muons pairs (with experimental test), study of the effects (and subsequent corrections) of the quantum chromodynamics on the amplitude of the strong coupling and on the evolution of the hadronic structure observed as a function of the sensor energy, and at last, after presenting how data are processed analysis of the hadronic structure appearing during the pair production of muons of great masses (4.2< Mμμ<8,5 GeV)
Deep recent data and phenomenology on low-x structure functions are discussed inelastic scattering. We will be interested primordially in the regions Q2 → 0 i.e. the transition from γp to, and x → 10-4 - 10-6 i.e. the region of high parton densities
Burkert, Volker D
2016-01-01
Recent results of meson photo-production at the existing electron machines with polarized real photon beams and the measurement of polarization observables of the final state baryons have provided high precision data that led to the discovery of new excited nucleon and $\\Delta$ states using multi-channel partial wave analyses procedures. The internal structure of several prominent excited states has been revealed employing meson electroproduction processes. On the theoretical front, lattice QCD is now predicting the baryon spectrum with very similar characteristics as the constituent quark model, and continuum QCD, such as is represented in the Dyson-Schwinger Equations approach and in light front relativistic quark models, describes the non-perturbative behavior of resonance excitations at photon virtuality of $Q^2 > 1.5GeV^2$. In this talk I discuss the need to continue a vigorous program of nucleon spectroscopy and the study of the internal structure of excited states as a way to reveal the effective degre...
Non-empirical energy density functional for the nuclear structure
The energy density functional (EDF) formalism is the tool of choice for large-scale low-energy nuclear structure calculations both for stable experimentally known nuclei whose properties are accurately reproduced and systems that are only theoretically predicted. We highlight in the present dissertation the capability of EDF methods to tackle exotic phenomena appearing at the very limits of stability, that is the formation of nuclear halos. We devise a new quantitative and model-independent method that characterizes the existence and properties of halos in medium- to heavy-mass nuclei, and quantifies the impact of pairing correlations and the choice of the energy functional on the formation of such systems. These results are found to be limited by the predictive power of currently-used EDFs that rely on fitting to known experimental data. In the second part of this dissertation, we initiate the construction of non-empirical EDFs that make use of the new paradigm for vacuum nucleon-nucleon interactions set by so-called low-momentum interactions generated through the application of renormalization group techniques. These soft-core vacuum potentials are used as a step-stone of a long-term strategy which connects modern many-body techniques and EDF methods. We provide guidelines for designing several non-empirical models that include in-medium many-body effects at various levels of approximation, and can be handled in state-of-the art nuclear structure codes. In the present work, the first step is initiated through the adjustment of an operator representation of low-momentum vacuum interactions using a custom-designed parallel evolutionary algorithm. The first results highlight the possibility to grasp most of the relevant physics for low-energy nuclear structure using this numerically convenient Gaussian vertex. (author)
Neutrino-pair bremsstrahlung from nucleon-nucleon scattering
Li, Yi; Liou, M. K.; Schreiber, W. M.; Gibson, B. F.
2015-07-01
Background: Neutrino-pair bremsstrahlung processes from nucleon-nucleon scattering N N ν ν ¯ (n n ν ν ¯ ,p p ν ν ¯ , and n p ν ν ¯ ) have recently attracted attention in studies of neutrino emission in neutron stars, because of the implications for the neutron star cooling. The calculated N N ν ν ¯ emissivities within the neutron star environment are relatively insensitive to the two-nucleon dynamical model used in the calculations, but differ significantly from those obtained using an one-pion-exchange (OPE) model. Purpose: We investigate the free N N ν ν ¯ cross sections using a realistic nucleon-nucleon scattering amplitude, comparing the relative sizes of the cross sections for the three processes n n ν ν ¯ ,p p ν ν ¯ , and n p ν ν ¯ . Method: We employ a realistic one-boson-exchange (ROBE) model for N N scattering and combine those strong scattering amplitudes with the well-known nucleon weak interaction vertices to construct weak bremsstrahlung amplitudes. Using the resulting N N ν ν ¯ amplitudes we investigate the relative importance of the vector (ΓVμ) , axial vector (ΓAμ) , and tensor (ΓTμ) terms. The ROBE model bremsstrahlung amplitudes are also used as a two-nucleon dynamical model with which we calculate the cross sections d/σ d ω for n n ν ν ¯ ,p p ν ν ¯ , and n p ν ν ¯ . Results: The three free N N ν ν ¯ cross sections d/σ d ω are of similar order of magnitude. Each increases with increasing neutrino-pair energy ω . For the neutrino-pair energy of ω =1 MeV our n n ν ν ¯ results are in quantitative agreement with those previously reported by Timmermans et al. [Phys. Rev. C 65, 064007 (2002), 10.1103/PhysRevC.65.064007], who used the leading-order term of the soft-neutrino-pair bremsstrahlung amplitude to calculate the cross sections. Differences between the n n ν ν ¯ and p p ν ν ¯ cross section are not discernible over the nucleon-nucleon incident energy region considered, due to the complete dominance of the axial vector component of the weak interaction nucleon vertex function Γμ as demonstrated analytically in Appendix A. The n p ν ν ¯ cross section is smaller than either the n n ν ν ¯ or the p p ν ν ¯ cross section for low to moderate values of ω ; this characteristic only changes at larger neutrino-pair energies around ω ˜50 MeV , which is above the low energy region characterized in Appendix B. Conclusions: The free N N ν ν ¯ cross sections, calculated using a realistic nucleon-nucleon amplitude model, are new except for the n n ν ν ¯ cross section at ω =1 MeV that was first reported by Timmermans et al., and at ω =0.5 ,1 ,2 MeV by Li et al. [Phys. Rev. C 80, 035505 (2009), 10.1103/PhysRevC.80.035505]. The n n ν ν ¯ and p p ν ν ¯ cross sections are virtually identical in magnitude. All three N N ν ν ¯ processes are dominated by the axial vector component of the vertex function Γμ, with only slight deviations from this behavior being seen in the n p ν ν ¯ process at large neutrino-pair energies.
Studies on regge behaviour and spin-independent and spin-dependent structure functions
Jamil, Begum Umme
2010-01-01
Deep Inelastic Scattering (DIS) experiments have provided important information on the structure of hadrons and ultimately the structure of matter and on the nature of interactions between leptons and hadrons, since the discovery of partons. Various high energy deep inelastic interactions lead to different evolution equations from which we obtain various structure functions giving information about the partons i.e. quarks and gluons involved in different scattering processes. Actually structure function is a mathematical picture of the hadron structure in the high energy region. Understanding the behaviour of the structure functions of the nucleon at low-x, where x is the Bjorken variable, is interesting both theoretically and phenomenologically. Structure functions are important inputs in many high energy processes and also important for examination of perturbative quantum chromodynamics (PQCD), the underlying dynamics of quarks and gluons. In PQCD, for high-Q2, where Q2 is the four momentum transfer in a DI...
We review experimental results concerning polarization phenomena in nucleon-nucleon scattering in which both the elastic scattering and hadron-production reaction are included. We also present summary of S = 0 dibaryon resonances and candidates by reviewing experimental data in the nucleon-nucleon system, ?d channel, ?d elastic scattering, pp ? ?d channel, deuteron break-up reactions, and narrow structures in missing-mass spectra. 93 refs., 26 figs
Structure functions in ?-->3?? decay
Xiong, Zhaohua; Chen, Guoming; Chen, Hesheng
1999-01-01
The structure functions in the ?-->3?? decay are extracted using the model proposed by Li. We compare the predictions of the Li model with the KS ones and the data from the OPAL experiment, and find that predictions by the model for wA(Q2) are consistent with the data except for in the high energy region (Q2>1.2 GeV2), and wC,wD,wE normalized to wA are in reasonable agreement with the experimental results. A running mass function of ma1 is proposed to the model.
Pauli blocking effects for nucleon-nucleus scattering
Theoretical predictions for nucleon-nucleus scattering are customarily based on multiple-scattering formalisms in which the projectile-nucleon--struck-target-nucleon two-body subsystem is antisymmetrized and in which the target wave function is antisymmetric with respect to the nucleon constituents. Although formalisms exist for nucleon-nucleus scattering which account for full (A+1)-body antisymmetrization, these theories have not been adequately implemented in numerical applications. Pauli blocking of the struck target nucleon in intermediate scattering states is implicitly included in standard optical potential calculations which consistently include terms through second-order in the projectile-target nucleon scattering t matrix. In this work the multiple scattering expansion of the fully antisymmetrized nucleon-nucleus optical potential is organized so as to make explicit corrections to the standard optical potential due to Pauli blocking of the projectile nucleon in intermediate scattering states. Numerical calculations are presented for the resulting density dependent, projectile-target nucleon effective interaction and comparison with a previous density dependent model is given. It is shown that density dependent effective interaction t matrices for nucleon-nucleus scattering calculations should include Pauli blocking of just the projectile nucleon and binding potential corrections for just the target nucleon
Measuring spin-dependent structure functions at CEBAF
Schaefer, A. [Universitaet Frankfurt (Germany)
1994-04-01
The author analyses whether CEBAF with a 10 GeV beam could contribute significantly to the understanding of spin-dependent deep-inelastic scattering as well as semi-inclusive reactions. The main advantage of CEBAF is the much better attainable statistics, its great disadvantage its comparably low energy, which limits the accessible x-range to about 0.15 to 0.7. Within these constraints CEBAF could provide (1) high precision data which would be very valuable to understand the Q{sup 2} dependence of the spin-dependent structure functions g{sub 1}(x) and G{sub 2}(x) and (2) the by far most precise determination of the third moments of g{sub 1}(x) and g{sub 2}(x) the latter of which the author argues to be related to a fundamental property of the nucleon.
Measuring spin-dependent structure functions at CEBAF
The author analyses whether CEBAF with a 10 GeV beam could contribute significantly to the understanding of spin-dependent deep-inelastic scattering as well as semi-inclusive reactions. The main advantage of CEBAF is the much better attainable statistics, its great disadvantage its comparably low energy, which limits the accessible x-range to about 0.15 to 0.7. Within these constraints CEBAF could provide (1) high precision data which would be very valuable to understand the Q2 dependence of the spin-dependent structure functions g1(x) and G2(x) and (2) the by far most precise determination of the third moments of g1(x) and g2(x) the latter of which the author argues to be related to a fundamental property of the nucleon
Proton and neutron polarized targets for nucleon-nucleon experiments at SATURNE II
Ball, J.; Combet, M.; Sans, J.L. [Laboratoire National Saturne, Centre d`Etudes de Saclay, 91 - Gif-sur-Yvette (France); Benda, B.; Chaumette, P.; Deregel, J.; Durand, G.; Dzyubak, A.P.; Gaudron, C.; Lehar, F. [CEA Centre d`Etudes de Saclay, 91 - Gif-sur-Yvette (France). Dept. d`Astrophysique, de la Physique des Particules, de la Physique Nucleaire et de l`Instrumentation Associee; Janout, Z.; Khachaturov, B.A. [Joint Inst. for Nuclear Research, Dubna (Russian Federation). Lab. of Nuclear Problems] [and others
1996-12-31
A SATURNE polarized target has been used for nucleon-nucleon elastic scattering and transmission experiments for 15 years. The polarized proton target is a 70 cm{sup 3} cartridge loaded with Pentanol-2. For polarized neutron target, two cartridges loaded with {sup 6}LiD and {sup 6}LiH are set in the refrigerator and can be quickly inserted in the beam. First experiments using {sup 6}Li products in quasielastic pp or pn analyzing power measurements are compared with the same observables measured in a free nucleon-nucleon scattering using polarized proton targets. Angular distribution as a function of a kinematically conjugate angle and coplanarity in nucleon-nucleon scattering is shown for different targets. (author). 15 refs.; Submitted to Nuclear Instruments and Methods (NL).
Proton and neutron polarized targets for nucleon-nucleon experiments at SATURNE II
A SATURNE polarized target has been used for nucleon-nucleon elastic scattering and transmission experiments for 15 years. The polarized proton target is a 70 cm3 cartridge loaded with Pentanol-2. For polarized neutron target, two cartridges loaded with 6LiD and 6LiH are set in the refrigerator and can be quickly inserted in the beam. First experiments using 6Li products in quasielastic pp or pn analyzing power measurements are compared with the same observables measured in a free nucleon-nucleon scattering using polarized proton targets. Angular distribution as a function of a kinematically conjugate angle and coplanarity in nucleon-nucleon scattering is shown for different targets. (author)
The Soudan nucleon decay program is being carried out in the Soudan iron mine in northeastern Minnesota, at a depth of 2000 m of water equivalent. A 30-ton prototype experiment, Soudan 1, has been built and is now being operated by a University of Minnesota - Argonne National Laboratory collaboration. The detector is a block of iron-loaded concrete instrumented with 3456 gas proportional tubes. It can detect nucleon decay at the 2 x 1030 year level, and will measure cosmic-ray induced backgrounds. Soudan 1 is also obtaining data on very high energy cosmic-ray interactions. Monte-Carlo predictions of performance have been checked by calibration of a detector module in a charged-particle test beam. A proposal to build a 1000-ton experiment, Soudan 2, has been submitted to funding agencies in the USA and the UK by a Minnesota - Argonne - Oxford University collaboration. The proposed detector utilizes drift chambers with 50-cm drifts to obtain very fine-grained ionization and tracking information at low cost. This tracking-calorimeter detector has a fiducial mass of 650 tons, and could be operating in 1985. A drifting scheme utilizing 50 cm x 5 m x 1 cm planar chambers has been shown feasible, and prototypes of alternate drifting structures are also being studied. A plan to provide expandability to an eventual 5000 tons has been developed
Functional nanometer-scale structures
Chan, Tsz On Mario
Nanometer-scale structures have properties that are fundamentally different from their bulk counterparts. Much research effort has been devoted in the past decades to explore new fabrication techniques, model the physical properties of these structures, and construct functional devices. The ability to manipulate and control the structure of matter at the nanoscale has made many new classes of materials available for the study of fundamental physical processes and potential applications. The interplay between fabrication techniques and physical understanding of the nanostructures and processes has revolutionized the physical and material sciences, providing far superior properties in materials for novel applications that benefit society. This thesis consists of two major aspects of my graduate research in nano-scale materials. In the first part (Chapters 3--6), a comprehensive study on the nanostructures based on electrospinning and thermal treatment is presented. Electrospinning is a well-established method for producing high-aspect-ratio fibrous structures, with fiber diameter ranging from 1 nm--1 microm. A polymeric solution is typically used as a precursor in electrospinning. In our study, the functionality of the nanostructure relies on both the nanostructure and material constituents. Metallic ions containing precursors were added to the polymeric precursor following a sol-gel process to prepare the solution suitable for electrospinning. A typical electrospinning process produces as-spun fibers containing both polymer and metallic salt precursors. Subsequent thermal treatments of the as-spun fibers were carried out in various conditions to produce desired structures. In most cases, polymer in the solution and the as-spun fibers acted as a backbone for the structure formation during the subsequent heat treatment, and were thermally removed in the final stage. Polymers were also designed to react with the metallic ion precursors during heat treatment in some cases, which led to desired chemical phase formation. The residue of polymer thermal decomposition was also controlled and utilized for certain functionality in some nanostructures. Throughout this study, we successfully fabricated several novel functional structures and revealed a new formation mechanism of metal/metal oxide nanotubes. The magnetic and electrical properties of these nanostructures were studied and optimized for applications in soft magnetic materials and spintronics devices. In the second part, (Chapter 7) a study on memristive switching devices with magnetron-sputtered metal-semiconductor-metal thin film structures based on ZnO is presented. Resistive random access memory (RRAM) is a new, non-volatile memory based on the memristor effect theoretically predicted by Leon Chua in 1971 and first experimentally demonstrated by Hewlett Packard in 2008. The unit cell of a RRAM (a memristor) is a two-terminal device in which the switching medium is sandwiched between the top and bottom electrodes and the resistance of the switching medium can be modulated by applying an electrical signal (current or voltage) to the electrodes. On the other hand, the significance of a memristor, as the fourth element of circuit elements besides resistor, capacitor and inductor, is not limited to just being a candidate for next-generation memory. Owing to the unique i-v characteristics of non-linear memristors that cannot be duplicated with any combinations of the other three basic elements in a passive circuitry, many new electrical functions are being developed based on the memristors. In our study, various contact electrode combinations and semiconductor doping profiles were utilized to achieve different functional resistive switching behaviors and to help fundamentally understand the underlying switching mechanisms in ZnO-based thin film structures. Two distinctive switching mechanisms (ferroelectric charge-induced resistive switching and dopant-induced filament-type resistive switching) have been identified in specified structures. Among them, the ferroelectric charg
Structure and Function of Glucansucrases
Dijkstra, B. W.; Vuji?i?-agar, A.
2008-03-01
Glucansucrases are relatively large (~160 kDa) extracellular enzymes produced by lactic acid bacteria. Using sucrose as a substrate they synthesize high molecular mass glucose polymers, called ?-glucans, which allow the bacteria to adhere to surfaces and create a biofilm. The glucan polymers are of importance for the food and dairy industry as thickening and jellying agents. An overview is given of the current insights into the structure and functioning of these and related enzymes.
On the photon structure function
The solution of the inhomogeneous evolution equations for the parton distributions of the photon in moment space with a general Born term and three arbitrary energy parameters has been investigated. In some special cases, the general solution can be reduced to the formulas which have been obtained by the previous papers. The differences between our result and those given by the previous papers for the photon structure function are significant not only numerically, but also in singularity behavior. (author). 10 refs
Quark models for nucleon-nucleon scattering
The results of the quark model for the short range nucleon-nucleon interaction are shortly reviewed. The Born-Oppenheimer approach and the Resonating Group Method for the S-phase shift of the n-n scattering are described. The symmetry and the Hamiltonian for the six-quark system are studied. The results are reviewed by using the Fermi-Breit coloured potential for short distances and OPEP for large distances.(author)
Pionic background for nucleon-nucleon observables
A method is presented that allows the unambiguous definition of the one pion exchange contribution to nucleon-nucleon scattering observables and then use it to determine those waves where values of phase shifts and mixing parameters may be understood as sums of pionic and non-pionic dynamical effects. This helps the assessment of the explicative power of the various existing phenomenological potentials and may eventually lead to ways of discriminating their effectiveness. (author) 16 refs.; 19 figs.; 2 tabs
Nucleon pair approximation description of the low-lying structure of $^{108,109}$Te and $^{109}$I
Jiang, H; Lei, Y; Liotta, R; Wyss, R; Zhao, Y M
2013-01-01
The low-lying level schemes and electromagnetic transitions of $^{109}$Te, $^{109}$I, and the neighboring even-even nucleus $^{108}$Te, are calculated within the framework of the $SD$-pair approximation of the nuclear shell model. Good agreement is obtained between the calculated results and experimental data. The favored components of low-lying bands are discussed in the collective nucleon-pair subspace. The weak-coupling picture shown in these nuclei and its relationship with residual quadrupole-quadrupole interaction between valence protons and neutrons are analyzed.
Monons, nucleons and electromagnetic field theory
A sub-nucleon group consisting of monons (Ω) Mullickons (Ωmk) and half-Mullickons (1/2Ωmk) has been theorized and worked out. It is assumed that the monon has mass equal to 1/10 that of a neutrino whose mass Nm is calculated to be .0001345 mu and a Mullickon is supposed to have a mass 1/10 that of a monon, i.e. .000001345 mu. The half-Millickon is considered to be the smallest conceived sub-nucleon element in the universe carrying electromagnetic charge and is at the base of all electromagnetic field creation, mass and electric charge. The first concept of creation, the sequence of development of sub-nucleons and nucleons, their structure, force balance, mass balance and electric balances have all been explained on the basis of this theory. The excitation charges, binding charges of the nucleons, the factors for monon units for each group of sub-nucleons and nucleons, their masses have been worked out according to this theory and shown to tally completely with the known nuclear masses. The possibility that the chain of nucleons dealt here are only those detectable on this earth and in some stars and not in the entire universe, has been pointed out. (K.B.)
Two theoretical approaches to extract the neutron structure functions from combined experimental data on the proton and deuteron are considered. It is shown that the consideration only of the Fermi motion of nucleons in the deuteron in the light cone kinematics gives wrong results at large x (x > 0.7). The meson exchange corrections and binding effects in the deuteron must be taken into account. A new treatment of the experimental neutron structure function obtained from BCDMS-collaboration data is given. (author). 18 refs, 4 figs, 2 tabs
Electromagnetic form factors of nucleons and Delta*
Li, BingAn
2000-01-01
A relativistic quark model and a new set of wave functions of nucleon and Delta have been used to study the electromagnetic propertities of (1/2)^+ baryons and photoelectric production of Delta(1236).
Muangma, I Korover N; Shneor, R; Sulkosky, V; Kelleher, A; Gilad, S; Higinbotham, D W; Watson, E Piasetzky J; Wood, S; Rakhman, Abdurahim; Aguilera, P; Ahmed, Z; Albataineh, H; Allada, K; Anderson, B; Anez, D; Aniol, K; Annand, J; Armstrong, W; Arrington, J; Averett, T; Badman, T; Baghdasaryan, H; Bai, X; Beck, A; Beck, S; Bellini, V; Benmokhtar, F; Bertozzi, W; Bittner, J; Boeglin, W; Camsonne, A; Chen, C; Chen, J -P; Chirapatpimol, K; Cisbani, E; Dalton, M; Daniel, A; Day, D; de Jager, C W; De Leo, R; Deconinck, W; Defurne, M; Flay, D; Fomin, N; Friend, M; Frullani, S; Fuchey, E; Garibaldi, F; Gaskell, D; Gilman, R; Glamazdin, O; Gu, C; Gueye, P; Hamilton, D; Hanretty, C; Hansen, O; Shabestari, M Hashemi; Holmstrom, T; Huang, M; Iqbal, S; Jin, G; Kalantarians, N; Kang, H; Khandaker, M; LeRose, J; Leckey, J; Lindgren, R; Long, E; Mammei, J; Margaziotis, D J; Markowitz, P; Jimenez-Arguello, A Marti; Meekins, D; Meziani, Z; Michaels, R; Mihovilovic, M; Monaghan, P; Camacho, C Munoz; Norum, B; Nuruzzaman,; Pan, K; Phillips, S; Pomerantz, I; Posik, M; Punjabi, V; Qian, X; Qiang, Y; Qiu, X; Reimer, P E; Riordan, S; Ron, G; Rondon-Aramayo, O; Saha, A; Schulte, E; Selvy, L; Shahinyan, A; Sirca, S; Sjoegren, J; Slifer, K; Solvignon, P; Sparveris, N; Subedi, R; Tireman, W; Wang, D; Weinstein, L B; Wojtsekhowski, B; Yan, W; Yaron, I; Ye, Z; Zhan, X; Zhang, J; Zhang, Y; Zhao, B; Zhao, Z; Zheng, X; Zhu, P; Zielinski, R
2014-01-01
We measured simultaneously the 4He(eep), 4He(eepp), and 4He(e,e'pn) reactions at Q^2=2 [GeV/c]2 and x_B>1, for a (e,e'p) missing-momentum range of 400 to 830 MeV/c. The knocked-out proton was detected in coincidence with a proton or neutron recoiling almost back to back to the missing momentum, leaving the residual A=2 system at low excitation energy. These data were used to identify two-nucleon short-range correlated pairs and to deduce their isospin structure as a function of missing momentum in a region where the nucleon-nucleon force is expected to change from predominantly tensor to repulsive. Neutron-proton pairs dominate the high-momentum tail of the nucleon momentum distributions, but their abundance is reduced as the nucleon momentum increases beyond ~500 MeV/c. The extracted fraction of proton-proton pairs is small and almost independent of the missing momentum in the range we studied. Our data are compared with ab-initio calculations of two-nucleon momentum distributions in 4He.
The structure of the neutron rich light nuclei 11Be and 10Li has been investigated by means of one nucleon transfer reactions. The experiments have been carried out at GANIL in inverse kinematics using 11Be secondary beams. The 11Be(p,d)10Be reaction bas been studied at 35.3 MeV/u. The 10Be ejectiles were analyzed by the spectrometer SPEG, and coincident deuterons were detected in the position sensitive silicon detector CHARISSA. Transfer cross sections to 0+1 and 2+1, states in 10Be were measured up to θCM = 16 deg. and compared to DWBA and CRC predictions. The effects of neutron-cure couplings on reaction form factors have been studied by solving coupled equations in the framework of a vibrational model. It is shown that the rate of core excitation 10Be2+ in the 11Begs wave function is overestimated by a standard analysis with form factors given by the usual Separation Energy prescription. The former model predicts a rate of core excitation of 16% and leads to theoretical cross sections which are in good agreement with the experimental data. The aim of the 11Be(d,3He)10Li experiment, realized at 37 MeV/u, was to measure the distribution of the 2s neutron strength in the unbound nucleus 10Li. The energy spectrum was deduced from the 3He energy and angle measured by the silicon strip detector array MUST. An asymmetric peak is clearly observed near the threshold, with a maximum at -Sn = 130 keV. This constitutes a direct proof of the inversion of 2s and 1p1/2 shells in 10Li, which was until now a controversial question in spite of many experimental efforts. On the other band the analysis of the 11Be(d,t)10Be reaction studied in the same experiment confirms the results obtained in the 11Be(p,d)10Be reaction concerning the 11Begs structure. This work shows the interest and feasibility of studies of the shell properties of exotic nuclei using transfer reactions induced by radioactive beams and constitutes the beginning of a program devoted to this kind of experiment. (author)
The isospin structure of photoproduction of pi-eta pairs from the nucleon in the threshold region
Kser, A; Annand, J R M; Arends, H J; Bantawa, K; Bartolome, P A; Beck, R; Bekrenev, V; Berghuser, H; Braghieri, A; Branford, D; Briscoe, W J; Brudvik, J; Cherepnya, S; Costanza, S; Demissie, B; Dieterle, M; Downie, E J; Drexler, P; Fil'kov, L V; Fix, A; Glazier, D I; Hamilton, D; Heid, E; Hornidge, D; Howdle, D; Huber, G M; Jahn, O; Jaegle, I; Jude, T C; Kashevarov, V L; Keshelashvili, I; Kondratiev, R; Korolija, M; Kruglov, S P; Krusche, B; Lisin, V; Livingston, K; MacGregor, I J D; Maghrbi, Y; Mancell, J; Manley, D M; Marinides, Z; McGeorge, J C; McNicoll, E; Mekterovic, D; Metag, V; Micanovic, S; Middleton, D G; Mushkarenkov, A; Nikolaev, A; Novotny, R; Oberle, M; Ostrick, M; Otte, P; Oussena, B; Pedroni, P; Pheron, F; Polonski, A; Prakhov, S N; Robinson, J; Rosner, G; Rostomyan, T; Schumann, S; Sikora, M H; Sober, D I; Starostin, A; Supek, I; Thiel, M; Thomas, A; Unverzagt, M; Watts, D P; Werthmller, D; Witthauer, L
2015-01-01
Photoproduction of $\\pi\\eta$-pairs from nucleons has been investigated from threshold up to incident photon energies of $\\approx$~1.4~GeV. The quasi-free reactions $\\gamma p\\rightarrow p\\pi^0\\eta$, $\\gamma n\\rightarrow n\\pi^0\\eta$, $\\gamma p\\rightarrow n\\pi^+\\eta$, and $\\gamma n\\rightarrow p\\pi^-\\eta$ were for the first time measured from nucleons bound in the deuteron. The corresponding reactions from a free-proton target were also studied to investigate final-state interaction effects (for neutral pions the free-proton results could be compared to previous measurements; the $\\gamma p\\rightarrow n\\pi^+\\eta$ reaction was measured for the first time). For the $\\pi^0\\eta$ final state coherent production via the $\\gamma d\\rightarrow d\\pi^0\\eta$ reaction was also investigated. The experiments were performed at the tagged photon beam of the Mainz MAMI accelerator using an almost $4\\pi$ coverage electromagnetic calorimeter composed of the Crystal Ball and TAPS detectors. The total cross sections for the four differ...
A Determination of the Neutron Spin Structure Function
The authors report the results of the experiment E142 which measured the spin dependent structure function of the neutron, g1n(x, Q2). The experiment was carried out at the Stanford Linear Accelerator Center by measuring an asymmetry in the deep inelastic scattering of polarized electrons from a polarized 3He target, at electron energies from 19 to 26 GeV. The structure function was determined over the kinematic range 0.03 2 2. An evaluation of the integral ∫01 g1n(x,Q2)dx at fixed Q2 = 2 (GeV/c)2 yields the final result Λ1n = -0.032 ± 0.006 (stat.) ± 0.009 (syst.). This result, when combined with the integral of the proton spin structure function measured in other experiments, confirms the fundamental Bjorken sum rule with O(αs3) corrections to within one standard deviation. This is a major success for perturbative Quantum Chromodynamics. Some ancillary results include the findings that the Ellis-Jaffe sum rule for the neutron is violated at the 2 σ level, and that the total contribution of the quarks to the helicity of the nucleon is 0.36 ± 0.10. The strange sea polarization is estimated to be small and negative, Δs = -0.07 ± 0.04
Structure and Function of Lipase
Skjold-Jørgensen, Jakob
waterlipidinterface. For Thermomyces lanuginosus lipase (TlL) and related lipases, activation of the enzymeinvolves a rearrangement of a structural domain, called the “lid”, which covers the active site inhomogenous aqueous solution. At the water-lipid interface, the lid is displaced from the active site andmoves...... towards an open conformation enabling the substrate to gain access, thus initiating catalysis.Lipases have been studied for decades and their functional features have drawn much attention withinindustrial applications since their first discovery. However, given that their molecular action takes placeat...... the water-lipid interface, structural movements occurring during activation have been difficult to probeexperimentally. In this work, novel variants of TlL were constructed based on rational design with amutated lid-region in order to elucidate the impact of the lid-residue composition and...
Supramolecular Structure and Function 9
Pifat-Mrzljak, Greta
2007-01-01
The book is based on International Summer Schools on Biophysics held in Croatia which, contrary to other workshops centered mainly on one topic or technique, has very broad scope providing advanced training in areas related to biophysics. This volume is presenting papers in the field of biophysics for studying biological phenomena by using physical methods (NMR, EPR, FTIR, Mass Spectrometry, etc.) and/or concepts (predictions of protein-protein interactions, virtual ligand screening etc.). The interrelationship of supramolecular structures and there functions is enlightened by applications of principals of these physical methods in the biophysical and molecular biology context.
A Study of Nucleon Spin Struture from Quantum Chromodynamics
Osborne, Jonathan
2001-01-01
I present an introduction to the field of Quantum Chromodynamics (QCD) with emphasis on nucleon spin structure and perturbative methods. After a somewhat comprehensive overview of perturbative QCD, including the systematics of renormalization, I introduce deeply-inelastic scattering and deeply-virtual Compton scattering along with the nonperturbative distribution functions appearing in these processes. I show how these processes can be used to extract the distribution of longitudinal spin of ...
Experimental results on the multiplicity distributions of various particles produced in the interactions of 7Li with emulsion nuclei at a momentum of 3 GeV/c per projectile nucleon are reported. A comparison with data on collisions induced by other nuclei at a nearly identical momentum per nucleon is presented in order to reveal the dependence on the projectile mass. The internal structure of 7Li is explored by studying the projectile fragment.The mean multiplicity of shower particles, s>, induced by 7Li is found to be less than that in the case of 6Li projectiles. The angular distributions of target fragments and relativistic charged secondaries are investigated. No shock-wave phenomena are observed. Forward-to-backward ratios are calculated for each case. The probability distributions for relativistic secondaries produced per unit rapidity are studied in detail, along with the rapidity densities and their dependence on the projectile and the target mass. A comparison of the angular spectra of shower particles produced in central and peripheral collisions supports the limiting-fragmentation hypothesis. The collisions in question seem to become more central with increasing shower-particle multiplicity
Time-reversal-invariance-violating nucleon-nucleon potential in the 1/N_c expansion
Samart, Daris; Schindler, Matthias R; Phillips, Daniel R
2016-01-01
We apply the large-$N_c$ expansion to the time-reversal-invariance-violating (TV) nucleon-nucleon potential. The operator structures contributing to next-to-next-to-leading order in the large-$N_c$ counting are constructed. For the TV and parity-violating case we find a single operator structure at leading order. The TV but parity-conserving potential contains two leading-order terms, which however are suppressed by 1/$N_c$ compared to the parity-violating potential. Comparison with phenomenological potentials, including the chiral EFT potential in the TV parity-violating case, leads to large-$N_c$ scaling relations for TV meson-nucleon and nucleon-nucleon couplings.
Orbital angular momentum in the nucleons
Lorcé, Cédric
2014-01-01
In the last decade, it has been realized that the orbital angular momentum of partons inside the nucleon plays a major role. It contributes significantly to nucleon properties and is at the origin of many asymmetries observed in spin physics. It is therefore of paramount importance to determine this quantity if we want to understand the nucleon internal structure and experimental observables. This triggered numerous discussions and controversies about the proper definition of orbital angular momentum and its extraction from experimental data. We summarize the present situation and discuss recent developments in this field.
The double differential cross sections are measured as a function of the mass number and total kinetic energy for products of the 40Ar (220 MeV)+124Sn, 40Ar(220 MeV)+108Ag, 40Ar(220 MeV)+139La and 64Zn (315 MeV)+122Sn, 64Zn(315 MeV)+108Ag, 64Zn (315 MeV)+139La reactions. The effect of specific features of the shell structure of colliding nuclei on the maximum position of the fragment mass distribution is studied within the microscopic approach. A qualitative difference in dependences of the maximum position on the total kinetic energy of products of the reactions with 64Zn and 40Ar observed experimentally points to the shell structure of interacting nuclei
Experimental Review of Photon Structure Function Data
Nisius, Richard
2009-01-01
The present knowledge of the structure of the photon is presented based on results obtained by measurements of photon structure functions at e+e- collider. Results are presented both for the QED structure of the photon as well as for the hadronic structure, where the data are also compared to recent parametrisations of the hadronic structure function F2Gamma(x,Q^2). Prospects of future photon structure function measurements, especially at an International Linear Collider are outlined.
Structures and Functions of Oligosaccharins
Albersheim, Peter
1995-12-01
We have made considerable progress during the 2.5 year funding period just ending in our studies of the structures and functions of oligosaccharide signal molecules (oligosaccharins). We have emphasized studies of the enzymes that solubilize, process, and degrade oligosaccharins and of the proteins that inhibit those enzymes. We have been especially interested in elucidating how oligosaccharins and their processing enzymes participate in determining the outcome of challenges to plants by pathogenic microbes. We have studied, to a lesser extent, the roles of oligosaccharins in plant growth and development. Abstracts of papers describing results acquired with support from this grant that have been published, submitted, or in preparation are presented to summarize the progress made during the last two and one half years. The report highlights the most important contributions made in our oiigosaccharin research during this time period, and the corresponding abstract is referenced. Results of work in progress are described primarily in conjunction with our application for continued support.
Improved chiral nucleon-nucleon potential up to next-to-next-to-next-to-leading order
Epelbaum, E; Meißner, U -G
2014-01-01
We present improved nucleon-nucleon potentials derived in chiral effective field theory up to next-to-next-to-next-to-leading order. We argue that the nonlocal momentum-space regulator employed in the two-nucleon potentials of Refs. [E. Epelbaum, W. Gloeckle, U.-G. Mei{\\ss}ner, Nucl. Phys. A747 (2005) 362], [D.R. Entem, R. Machleidt, Phys. Rev. C68 (2003) 041001] is not the most efficient choice, in particular since it affects the long-range part of the interaction. We are able to significantly reduce finite-cutoff artefacts by using an appropriate regularization in coordinate space which maintains the analytic structure of the amplitude. The new potentials do not require the additional spectral function regularization employed in Ref. [E. Epelbaum, W. Gloeckle, U.-G. Mei{\\ss}ner, Nucl. Phys. A747 (2005) 362] to cut off the short-range components of the two-pion exchange and make use of the low-energy constants c_i and d_i determined from pion-nucleon scattering without any fine tuning. We discuss in detail t...
Airway Gland Structure and Function.
Widdicombe, Jonathan H; Wine, Jeffrey J
2015-10-01
Submucosal glands contribute to airway surface liquid (ASL), a film that protects all airway surfaces. Glandular mucus comprises electrolytes, water, the gel-forming mucin MUC5B, and hundreds of different proteins with diverse protective functions. Gland volume per unit area of mucosal surface correlates positively with impaction rate of inhaled particles. In human main bronchi, the volume of the glands is ∼ 50 times that of surface goblet cells, but the glands diminish in size and frequency distally. ASL and its trapped particles are removed from the airways by mucociliary transport. Airway glands have a tubuloacinar structure, with a single terminal duct, a nonciliated collecting duct, then branching secretory tubules lined with mucous cells and ending in serous acini. They allow for a massive increase in numbers of mucus-producing cells without replacing surface ciliated cells. Active secretion of Cl(-) and HCO3 (-) by serous cells produces most of the fluid of gland secretions. Glands are densely innervated by tonically active, mutually excitatory airway intrinsic neurons. Most gland mucus is secreted constitutively in vivo, with large, transient increases produced by emergency reflex drive from the vagus. Elevations of [cAMP]i and [Ca(2+)]i coordinate electrolyte and macromolecular secretion and probably occur together for baseline activity in vivo, with cholinergic elevation of [Ca(2+)]i being mainly responsive for transient increases in secretion. Altered submucosal gland function contributes to the pathology of all obstructive diseases, but is an early stage of pathogenesis only in cystic fibrosis. PMID:26336032
Homing endonuclease structure and function.
Stoddard, Barry L
2005-02-01
Homing endonucleases are encoded by open reading frames that are embedded within group I, group II and archael introns, as well as inteins (intervening sequences that are spliced and excised post-translationally). These enzymes initiate transfer of those elements (and themselves) by generating strand breaks in cognate alleles that lack the intervening sequence, as well as in additional ectopic sites that broaden the range of intron and intein mobility. Homing endonucleases can be divided into several unique families that are remarkable in several respects: they display extremely high DNA-binding specificities which arise from long DNA target sites (14-40 bp), they are tolerant of a variety of sequence variations in these sites, and they display disparate DNA cleavage mechanisms. A significant number of homing endonucleases also act as maturases (highly specific cofactors for the RNA splicing reactions of their cognate introns). Of the known homing group I endonuclease families, two (HNH and His-Cys box enzymes) appear to be diverged from a common ancestral nuclease. While crystal structures of several representatives of the LAGLIDADG endonuclease family have been determined, only structures of single members of the HNH (I-HmuI), His-Cys box (I-PpoI) and GIY-YIG (I-TevI) families have been elucidated. These studies provide an important source of information for structure-function relationships in those families, and are the centerpiece of this review. Finally, homing endonucleases are significant targets for redesign and selection experiments, in hopes of generating novel DNA binding and cutting reagents for a variety of genomic applications. PMID:16336743
EN YO,H.; SAITO,N.; SHIBATA,T.A.; YAZAKI,K.; BUNCE,G.
2002-03-29
The RIKEN School on ''Quark-Gluon Structure of the Nucleon and QCD'' was held from March 29th through 31st at the Nishina Memorial Hall of RIKEN, Wako, Saitama, Japan, sponsored by RIKEN (the Institute of Physical and Chemical Research). The school was the second of a new series with a broad perspective of hadron and nuclear physics. The purpose of the school was to offer young researchers an opportunity to learn theoretical aspects of hadron physics based on QCD and related experimental programs being or to be carried out by Japanese groups. We had 3 theoretical courses, each consisting of 3 one-hour lectures, and 6 experimental courses, each consisting of a one-hour lecture.
Large Q2 electrodisintegration of the deuteron in the virtual nucleon approximation
The two-body breakup of the deuteron is studied at high-Q2 kinematics, with the main motivation to probe the deuteron at small internucleon distances. Such studies are associated with the probing of the high-momentum component of the deuteron wave function. For this, two main theoretical issues have been addressed: electromagnetic interaction of the virtual photon with the bound nucleon and the strong interaction of produced baryons in the final state of the breakup reaction. Within virtual nucleon approximation we developed a new prescription to account for the bound nucleon effects in electromagnetic interaction. The final-state interaction at high-Q2 kinematics is calculated within the generalized eikonal approximation (GEA). We studied the uncertainties involved in the calculation and performed comparisons with the first experimental data on deuteron electrodisintegration at large Q2. We demonstrate that the experimental data confirm the GEA's early prediction that the rescattering is maximal at ∼70 deg. of recoil nucleon production relative to the momentum of the virtual photon. Comparisons also show that the forward recoil nucleon angles are best suited for studies of the electromagnetic interaction of bound nucleons and the high-momentum structure of the deuteron. Backward recoil angle kinematics show sizable effects owing to the Δ-isobar contribution. The latter indicates the importance of further development of the GEA to account for the inelastic transitions in the intermediate state of the electrodisintegration reactions.
A study of nuclear effect in $F_3$ structure function in the deep inelastic $\
Athar, M Sajjad; Singh, S K; Vacas, M J Vicente
2009-01-01
We study nuclear effect in the $F^A_3(x)$ structure function in the deep inelastic neutrino reactions on iron by taking into account Fermi motion, binding, target mass correction, shadowing and anti-shadowing corrections. Calculations have been done in a local density approximation using relativistic nuclear spectral functions which include nucleon correlations for nuclear matter. Results for $F^A_3(x)$ have been compared with the results reported at NuTeV and also with some of the older experiments reported in the literature.
Gauge-Invariant Decomposition of Nucleon Spin
I introduce a gauge-invariant decomposition of the nucleon spin into quark helicity, quark orbital, and gluon contributions. The total quark (and hence the quark orbital) contribution is shown to be measurable through virtual Compton scattering in a special kinematic region where single quark scattering dominates. This deeply virtual Compton scattering has much potential to unravel the quark and gluon structure of the nucleon. copyright 1997 The American Physical Society
Measurement of the neutron spin structure function---Test of the Bjorken sum rule
As experiment to measure the neutron spin-dependent structure function g1n (x) over a range in x from 0.04 to 0.7 and with Q2 > 1 (GeV/c)2 is presented. The experiment consists of scattering a longitudinally polarized electron beam from the Stanford Linear Accelerator off a polarized 3He target and detecting scattered electrons in two magnetic spectrometers. The experiment will provide a critical test of the Bjorken sum rule and valuable information in understanding the nucleon spin structure and the violation of the Ellis-Jaffe sum rule. 3 figs., 1 tab
Quark-parton model for the structure function W2 of the proton and neutron in their rest systems
The deep-inelastic structure function W2 is calculated using the impulse approximation for mass-shell partons in the target-nucleon rest system. Bjorken scaling and the approach to scaling are shown to follow from parton kinematics in the rest system. The partons are identified as quarks and a simple harmonic-oscillator quark model is used to fit the proton and neutron structure functions down to x approx. 0.1. The neutron structure function requires an inherently non-SU(6) quark model based on relative coordinates that we argue should replace shell-model SU(6) quark models that have been used extensively
Measurement of the deuteron elastic structure functions A(Q2) and B(Q2) at large momentum transfers
The cross section for elastic electron-deuteron scattering was measured in Jefferson Lab experiment 91-026. The deuteron elastic structure functions A(Q2) and B(Q2) have been extracted from the data. The final results for the electric structure function, A(Q2), in the range of 0.722, are presented. Preliminary results for the magnetic structure function, B(Q2), are presented in the range of 0.72< or=1.35 (GeV/c)2. These data are compared to the theoretical predictions of both meson-nucleon and quark-gluon based models
Precision measurement of the neutron spin dependent structure functions
In experiment E154 at the Stanford Linear Accelerator Center the spin dependent structure function g1n (x, Q2) of the neutron was measured by scattering longitudinally polarized 48.3 GeV electrons off a longitudinally polarized 3He target. The high beam energy allowed the author to extend the kinematic coverage compared to the previous SLAC experiments to 0.014 ≤ x ≤ 0.7 with an average Q2 of 5 GeV2. The author reports the integral of the spin dependent structure function in the measured range to be ∫0.0140.7 dx g1n(x, 5 GeV2) = -0.036 ± 0.004(stat.) ± 0.005(syst.). The author observes relatively large values of g1n at low x that call into question the reliability of data extrapolation to x → 0. Such divergent behavior disagrees with predictions of the conventional Regge theory, but is qualitatively explained by perturbative QCD. The author performs a Next-to-Leading Order perturbative QCD analysis of the world data on the nucleon spin dependent structure functions g1p and g1n paying careful attention to the experimental and theoretical uncertainties. Using the parameterizations of the helicity-dependent parton distributions obtained in the analysis, the author evolves the data to Q2 = 5 GeV2, determines the first moments of the polarized structure functions of the proton and neutron, and finds agreement with the Bjorken sum rule
Haider, H; Athar, M Sajjad; Singh, S K; Simo, I Ruiz
2016-01-01
We have studied nuclear structure functions $F_{1A}(x,Q^2)$ and $F_{2A}(x,Q^2)$ for electromagnetic and weak processes in the region of $1 GeV^2 < Q^2 <8 GeV^2$. The nuclear medium effects arising due to Fermi motion, binding energy, nucleon correlations, mesonic contributions and shadowing effects are taken into account using a many body field theoretical approach. The calculations are performed in a local density approximation using a relativistic nucleon spectral function. The results are compared with the available experimental data. Implications of nuclear medium effects on the validity of Callan-Gross relation are also discussed.
Studies of the dilepton emission from nucleon-nucleon interactions
The real- and virtual-photon emission during interactions between few-nucleon systems have been investigated at KVI with a 190 MeV proton beam. Here I will concentrate the discussion on the results of the virtual-photon emission for the proton-proton system and proton-deuteron capture. Predictions of a fully-relativistic microscopic-model of the proton-proton interaction are discussed. For the proton-deuteron capture process the data is compared with predictions of a relativistic gauge-invariant impulse approximation and a Faddeev calculation. For the virtual photon processes, the nucleonic electromagnetic response functions were obtained for the first time and are compared to model predictions. (author)
Nuclear shell model calculations with fundamental nucleon-nucleon interactions
Pan, X W; Vallires, M
1995-01-01
Some fundamental Nucleon-Nucleon interactions and their applications to finite nuclei are reviewed. Results for the few-body systems and from Shell-Model calculations are discussed and compared to point out the advantages and disadvantages of the different Nucleon-Nucleon interactions. The recently developed Drexel University Shell Model (DUSM) code is mentioned.
Off-shell properties of the Paris nucleon-nucleon potential and implications for few-body systems
We investigate the half-off-shell properties for the Paris nucleon-nucleon potential and for a separable representation of it. Deuteron bound-state and scattering wave functions as well as Noyes-Kowalski functions are considered. Essential features with respect to elastic electron-deuteron and nucleon-deuteron scattering are discussed. We find that some polarization observables of these processes dismiss certain off-shell behaviours encountered, for instance, in various phenomenological separable potentials
Deep Inelastic Scattering from A=3 Nuclei and the Neutron Structure Function
We present a comprehensive analysis of deep inelastic scattering from 3He and 3H, focusing in particular on the extraction of the free neutron structure function, Fn2. Nuclear corrections are shown to cancel to within 1-2% for the isospin-weighted ratio of 3He to 3H structure functions, which leads to more than an order of magnitude improvement in the current uncertainty on the neutron to proton ratio F2n2/Fp2 at large x. Theoretical uncertainties originating tom the nuclear wave function, including possible non-nucleonic components, are evaluated. Measurement of the 3He and 3H structure functions will, in addition, determine the magnitude of the EMC effect in all A [lte] 3 nuclei
What do we learn from polarization measurements in deep-inelastic electron-nucleon scattering
We examine what can be learned from deep-inelastic electron-nucleon scattering with polarized initial electrons and measurement of the polarization of the final electrons. A direct evaluation of the separate structure functions W1 and W2 is shown to be possible
The spin of the nucleon in deep inelastic lepton scattering experiments
Mallot, G.K. [European Organization for Nuclear Research, Geneva (Switzerland). PPE Div.]|[Mainz Univ. (Germany). Inst. fuer Kernphysik
1992-09-01
The current experimental status of the spin dependent structure functions as measured in polarized deep inelastic scattering of charged leptons from nucleons is reviewed. The proposals for new experiments at CERN, SLAC and HERA are discussed with special emphasis on the experiment of the Spin Muon collaboration at CERN which has started data taking.
The spin of the nucleon in deep inelastic lepton scattering experiments
Mallot, G.K. (European Organization for Nuclear Research, Geneva (Switzerland). PPE Div. Mainz Univ. (Germany). Inst. fuer Kernphysik)
1992-01-01
The current experimental status of the spin dependent structure functions as measured in polarized deep inelastic scattering of charged leptons from nucleons is reviewed. The proposals for new experiments at CERN, SLAC and HERA are discussed with special emphasis on the experiment of the Spin Muon collaboration at CERN which has started data taking.
Neutral-current x-distributions in the neutrino-nucleon scattering
In this thesis the measurement of the x distribution of the structure functions for deep inelastic charged-current and neutral-current neutrino-nucleon interactions at the CERN 200 GeV narrow-band neutrino beam is described. (HSI)
PUFAs: Structures, Metabolism and Functions.
Wiktorowska-Owczarek, Anna; Berezi?ska, Ma?gorzata; Nowak, Jerzy Z
2015-01-01
Polyunsaturated fatty acids (PUFAs) include two series of fatty acids: omega-6 and omega-3 series. PUFAs have amphiphatic properties: hydrophilic head and hydrophobic tail. Such structure and other properties of unsaturated fatty acids are responsible for exerting the following biological action: maintaining cell-membrane fluidity, inhib- iting inflammatory processes, decreasing secretion of proinflammatory cytokines by monocytes/macrophages, decreasing susceptibility to ventricular rhythm disorders of the heart, improving functions of vascular endothe- lial cells, inhibiting blood platelet aggregation and decreasing triglyceride synthesis in the liver. In an organism, aracidonic acid (ARA) is converted to prostanoids series 2 (PGE2, PGI2, TXA2) and leukotrienes series 4 (LTB4, LTC4, LTD4) which are endowed with pro-inflammatory potential and are able to induce platelet aggregation and vasoconstriction. The metabolism of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) gives prostanoids series 3 (PGE3, PGI3, TXA3) and leukotrienes series 5 (LTB5, LTC5, LTD5); this group of eicosanoids shows anti-inflammatory, antiplatelet and antiarrhythmic properties. PMID:26771963
Cottingham formula and nucleon polarisabilities
Gasser, J.; Leutwyler, H. [Universitaet Bern, Albert Einstein Center for Fundamental Physics, Institut fuer theoretische Physik, Bern (Switzerland); Hoferichter, M. [Universitaet Bern, Albert Einstein Center for Fundamental Physics, Institut fuer theoretische Physik, Bern (Switzerland); Technische Universitaet Darmstadt, Institut fuer Kernphysik, Darmstadt (Germany); GSI Helmholtzzentrum fuer Schwerionenforschung GmbH, ExtreMe Matter Institute EMMI, Darmstadt (Germany); University of Washington, Institute for Nuclear Theory, Seattle, WA (United States); Rusetsky, A. [Universitaet Bonn, Helmholtz-Institut fuer Strahlen- und Kernphysik (Theorie) and Bethe Center for Theoretical Physics, Bonn (Germany)
2015-08-15
The difference between the electromagnetic self-energies of proton and neutron can be calculated with the Cottingham formula, which expresses the self-energies as an integral over the electroproduction cross sections - provided the nucleon matrix elements of the current commutator do not contain a fixed pole. We show that, under the same proviso, the subtraction function occurring in the dispersive representation of the virtual Compton forward scattering amplitude is determined by the cross sections. The representation in particular leads to a parameter-free sum rule for the nucleon polarisabilities. We evaluate the sum rule for the difference between the electric polarisabilities of proton and neutron by means of the available parameterisations of the data and compare the result with experiment. (orig.)
Cottingham formula and nucleon polarizabilities
Gasser, J; Leutwyler, H; Rusetsky, A
2015-01-01
The difference between the electromagnetic self-energies of proton and neutron can be calculated with the Cottingham formula, which expresses the self-energies as an integral over the electroproduction cross sections---provided the nucleon matrix elements of the current commutator do not contain a fixed pole. We show that, under the same proviso, the subtraction function occurring in the dispersive representation of the virtual Compton forward scattering amplitude is determined by the cross sections. The representation in particular leads to a parameter-free sum rule for the nucleon polarizabilities. We evaluate the sum rule for the difference between the electric polarizabilities of proton and neutron by means of the available parameterizations of the data and compare the result with experiment.
Cottingham formula and nucleon polarisabilities
The difference between the electromagnetic self-energies of proton and neutron can be calculated with the Cottingham formula, which expresses the self-energies as an integral over the electroproduction cross sections - provided the nucleon matrix elements of the current commutator do not contain a fixed pole. We show that, under the same proviso, the subtraction function occurring in the dispersive representation of the virtual Compton forward scattering amplitude is determined by the cross sections. The representation in particular leads to a parameter-free sum rule for the nucleon polarisabilities. We evaluate the sum rule for the difference between the electric polarisabilities of proton and neutron by means of the available parameterisations of the data and compare the result with experiment. (orig.)
From skyrmions to the nucleon-nucleon potential
The large NC limit implies that nucleons are topological solitons of an effective meson field theory. When deriving the nucleon-nucleon potential in such a picture one has to deal with interacting solitons. Numerical simulations of soliton collisions are presented. At low kinetic energy the complexity of such events is reduced and an adiabatic treatment becomes possible. Semiclassical quantization within the Born-Oppenheimer Approximation yields a potential which shows the basic features of empirical nucleon-nucleon interaction. (orig.)
The E142 SLAC experiment: measurement of the neutron gn1(x) spin structure function
This thesis describes the E142 experiment which has been carried out at the Stanford Linear Accelerator (SLAC), USA, from October to December 1992. This experiment of polarized inelastic scattering of a 22.6 GeV electron beam on a polarized helium 3 target has allowed the first measurement of the neutron gn1(x) spin structure function. The knowledge of this structure function gives informations on the nucleon spin structure. On the other hand, the gn1(x) structure function integral value on the 02 mean value of 2 GeV2 after some extrapolations. This value is at about two standard deviations away from the theoretical predictions of the Ellis-Jaffe rule. Thanks to the existing experimental results for the proton (E143 experiment), the Bjorken sum rule has been precisely tested and is perfectly compatible with the theoretical value. The results have allowed to estimate the nucleon spin fraction carried by the quarks. (J.S.). 86 refs., 58 figs., 13 tabs
Mesonic folded diagram theory of the nucleon-nucleon potential
Based on a T-matrix equivalence theory, an energy independent nucleon-nucleon potential V derived from meson exchanges is studied. The potential, given as a series expansion of folded diagrams is off-energy-shell and independent of the asymptotic energy of the scattering nucleons. The theory makes use of right-hand side on-shell T-matrix equivalence of the field theoretical and potential descriptions when limited to the space of neutrons and protons only. This preserves not only scattering (e.g. phase shifts, projections of wave functions) but also bound state properties. The matrix elements of V were calculated for two potential models, one based on one-pion exchange (OPEP) and the other on one-boson exchange (OBEP) using (π, rho, sigma, omega, delta, eta). Three types of phase shift calculations were carried out to study the viability of constructing an energy independent potential using the folded diagram expansion: (A) NN phase shifts for the 1S0, 1P1, 1D2, 3P1, 3D2, 3S1, 2D1, and 3P2 channels using an energy dependent OPEP and OBEP. For the OBEP the author used adjusted form factor parameters to fit experimental data. (b) The same phase shifts for the energy independent case for both OPEP and OBEP. (C) Repetition of (B) with effects of the two-pion folded diagrams included
Clustering effect of nucleonic matter in low-density region
Full text: We consider clustering effect of symmetric and asymmetric nucleonic matter in low-density situation. To describe such a system, we adopt a Bloch function (B.F.) as a single-particle state. When clusters form and the matter has a periodic structure, a nucleon feels a periodic mean field. In analogy with electrons in a crystal, such a single-particle state of a nucleon is described by linear combination of atomic orbitals, Ψ Α Π from i=1 until A φcki (ri) Xi (σi, τi), φck (r) = (a/L)3/2 (1/Nck)3/2 Σ eikma φc (r-ma), where φck and Xi are the spatial and spin-isospin part of a single-particle wave function, respectively, and φc is an atomic orbital. a is the periodic distance, L3 is the normalization volume, and Nck is the normalization factor. In the case of an alpha-particle-like density fluctuation in symmetric nucleonic matter, we adopt the s-wave function as φc, φs(r) = (b/ √ π)3/2 exp [-b2/2 r2], For the purpose of describing asymmetric nucleonic matter, we have to prepare a B.F. constructed by a p-wave function, φpx (r) = (b/√ π)3/2 √ 2 bx exp [-b2/2 r2], but such a p-wave B.F. is not orthogonal to a s-wave B.F. Here we define the orthogonal p-wave B.F. to the s-wave B.F. as follows: φopx,k (r) = (1/Nopk)1/2 [φpxk (r) - [φsk/φpxk] φsk (r)], φopyk and φopxk are also defined in the similar way. It should be noticed that these orthogonal p-wave B.F. are not only orthogonal to the s-wave B.F. but also orthogonal among them. By the use of such B.F s. we can describe both completely clusterized matter in one limit and uniform matter in another limit, and also in-medium states. In this report we discuss clustering phenomena of both symmetric and asymmetric nucleonic matter under low-density situation. (Author)
Nucleon transfer at the example of the 13C(13C,12C)14C reactions
On the basis of molecular wave functions a theory of nucleon-transfer in heavy ion reactions is presented. The particle-core-model for a system of two cores and N- valence nucleons is applied by using two-center shell model (TCSM) wavefunctions for the extra particles and describing to collectively excitable cores by rotator- vibrator models. Potentials for shape polarization are contained in the two-center shell model and in the interaction between the cores. The transfer (and excitation) of the valence particles is caused by the radial and rotational couplings. Using the same TCSM in all fragmentations, numerical calculations are made for the real neutron transfer reaction 13C (13C, 12C) 14C. The excitation function shows prominent structures as seen in experiment but not produced in a single-step (DWBA-) treatment. Therefore, the nucleon transfer in this system relies on a molecular orbital mechanism. (orig.)
The behavior of a nucleon in nuclear medium is discussed in Chiral Color Dielectric Model. It is assumed that the nucleons in nuclear medium produces a background dielectric field and the quark and dielectric field equations are solved self consistently in presence of the dielectric field. A nucleon in nuclear medium is then constructed by means of standard procedure followed in chiral bag models. The corrections due to center of mass motion, color magnetic interaction and meson interaction are included. The calculations show that the nucleon becomes bigger in the medium but its mass does not change much. It is found that beyond a certain density, bound solutions in which quarks are bound in self-generated dielectric field are not possible. Thus, the calculations indicate that there is a critical density beyond which the matter consists of deconfined quarks. (author)
Charmonium absorption by nucleons
Sibirtsev, A.; Tsushima, K; Thomas, A. W.
2000-01-01
$J/\\Psi$ dissociation in collisions with nucleons is studied within a boson exchange model and the energy dependence of the dissociation cross section is calculated from the threshold for $\\Lambda_c{\\bar D}$ production to high energies. We illustrate the agreement of our results with calculations based on short distance QCD and Regge theory. The compatibility between our calculations and the data on $J/\\Psi$ photoproduction on a nucleon is discussed. We evaluate the elastic $J/\\Psi{+}N$ cross...
Nucleon form factors, generalized parton distributions and quark angular momentum
Diehl, Markus [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Kroll, Peter [Bergische Univ., Wuppertal (Germany). Fachbereich Physik; Regensburg Univ. (Germany). Institut fuer Theoretische Physik
2013-02-15
We extract the individual contributions from u and d quarks to the Dirac and Pauli form factors of the proton, after a critical examination of the available measurements of electromagnetic nucleon form factors. From this data we determine generalized parton distributions for valence quarks, assuming a particular form for their functional dependence. The result allows us to study various aspects of nucleon structure in the valence region. In particular, we evaluate Ji's sum rule and estimate the total angular momentum carried by valence quarks at the scale {mu}=2 GeV to be J{sup u}{sub v}=0.230{sup +0.009}{sub -0.024} and J{sup d}{sub v}=-0.004{sup +0.010}{sub -0.016}.
Carbone, Arianna; Polls, Artur
2013-01-01
We present calculations for symmetric nuclear matter using chiral nuclear interactions within the Self-Consistent Green's Functions approach in the ladder approximation. Three-body forces are included via effective one-body and two-body interactions, computed from an uncorrelated average over a third particle. We discuss the effect of the three-body forces on the total energy, computed with an extended Galitskii-Migdal-Koltun sum-rule, as well as on single-particle properties. Saturation properties are substantially improved when three-body forces are included, but there is still some underlying dependence on the renormalization scale.
A NEW METHOD FOR EXTRACTING SPIN-DEPENDENT NEUTRON STRUCTURE FUNCTIONS FROM NUCLEAR DATA
Kahn, Y.F.; Melnitchouk, W.
2009-01-01
High-energy electrons are currently the best probes of the internal structure of nucleons (protons and neutrons). By collecting data on electrons scattering off light nuclei, such as deuterium and helium, one can extract structure functions (SFs), which encode information about the quarks that make up the nucleon. Spin-dependent SFs, which depend on the relative polarization of the electron beam and the target nucleus, encode quark spins. Proton SFs can be measured directly from electron-proton scattering, but those of the neutron must be extracted from proton data and deuterium or helium-3 data because free neutron targets do not exist. At present, there is no reliable method for accurately determining spin-dependent neutron SFs in the low-momentum-transfer regime, where nucleon resonances are prominent and the functions are not smooth. The focus of this study was to develop a new method for extracting spin-dependent neutron SFs from nuclear data. An approximate convolution formula for nuclear SFs reduces the problem to an integral equation, for which a recursive solution method was designed. The method was then applied to recent data from proton and deuterium scattering experiments to perform a preliminary extraction of spin-dependent neutron SFs in the resonance region. The extraction method was found to reliably converge for arbitrary test functions, and the validity of the extraction from data was verifi ed using a Bjorken integral, which relates integrals of SFs to a known quantity. This new information on neutron structure could be used to assess quark-hadron duality for the neutron, which requires detailed knowledge of SFs in all kinematic regimes.
Spin Structure Function Measurements from E143 at SLAC
Recent high statistics measurements of the nucleon spin structure functions by the E143 Collaboration are presented. The structure functions g1n and g1d have been measured over the range 0.029 2 2 using deep inelastic scattering of polarized electrons from polarized ammonia and deuterated ammonia targets. Evaluation of the integral Γ1p = ∫01 g1p(x, Q2)dx at fixed Q2 = 3 (GeV/c)2 yields 0.127 ± 0.004 ± 0.010, in agreement with previous experiments, but well below the Ellis-Jaffe sum rule prediction of 0.160 ± 0.006. The integral Γ1d = ∫01 g1d(x,Q2)dx also evaluated at fixed Q2 = 3 (GeV/c)2 gives 0.041 ± 0.004 ± 0.004, again below the Ellis-Jaffe sum rule prediction of 0.068 ± 0.005. From g1p and g1d, the neutron structure function g1n can be computed with Γ1n measured as -0.037 ± 0.008 ± 0.010. Combined with the measurement of g1p, they find Γ1p - Γ1n = 0.163 ± 0.010 ± 0.016 which agrees with the prediction of the Bjorken sum rule with Ο(αs3) corrections, Γ1p- 1n = 0.171 ± 0.008. In the quark-parton model, this implies that the net helicity carried by the quarks is Δq = 0.34 ± 0.04
Measurement of the deuteron elastic structure functions up to large momentum transfers
The cross section for elastic electron-deuteron scattering was measured in JLab experiment 91-026. The deuteron elastic structure functions A(Q2) and B(Q2) have been extracted from this data. The final results for the ''electric'' structure function A(Q2), in the range of 0.7 less than or equal to Q2 less than or equal to 6.0 (GeV/c)2 are presented. Preliminary results for the ''magnetic'' structure function B(Q2) are presented in the range of 0.7 less than or equal to Q2 less than or equal to 1.35 (GeV/c)2. These data are compared with theoretical predictions of both meson-nucleon and quark-gluon based models
Recent results on nucleon sigma terms in lattice QCD
It has proven a significant challenge to experiment and phenomenology to extract a precise values of the nucleon sigma terms. This difficulty opens the window for lattice QCD simulations to lead the field in resolving this aspect of nucleon structure. Here we report on recent advances in the extraction of nucleon sigma terms in lattice QCD. In particular, the strangeness component is now being resolved to a precision that far surpasses best phenomenological estimates.
Chiral Odd Structure Functions in The Nambu--Jona--Lasinio Soliton Model
Gamberg, Leonard; Reinhardt, Hugo; Weigel, Herbert
1998-10-01
We study unpolarized and polarized nucleon structure functions(H. Weigel, L. Gamberg, and H. Reinhardt, Mod. Phys. Lett. A11) (1996) 3021; Phys. Lett. B399 (1997) 287;Phys. Rev. D55(1997) 6910. within the bosonized Nambu--Jona--Lasinio (NJL) model where the nucleon emerges as a chiral soliton(R. Alkofer, H. Reinhardt and H. Weigel, Phys. Rep. 265) (1996) 139.. These considerations attempt to merge the parton model description of deep inelastic scattering with the phenomenologically successful picture of baryons as chiral solitons. In addition we report on the calculation of the chiral odd quark distributions(L. Gamberg, H. Reinhardt and H. Weigel, "Chiral odd structure functions from a chiral soliton", hep-ph/9801379, Phys. Rev. D. in press.) and the corresponding structure functions h_T(x,Q^2) and h_L(x,Q^2). At the low model scale, Q_0^2, we find that the leading twist effective quark distributions, f_1^(q)(x,Q_0^2), g_1^(q)(x,Q_0^2) and h_T^(q)(x,Q_0^2) satisfy Soffer's inequality for both quark flavors q=u,d. The Q^2 evolution of the twist--2 contributions is performed according to the standard GLAP formalism while the twist--three pieces, \\overlineg_2(x) and \\overlineh_L(x), are evolved according to the large NC scheme.
Measurement of the deuteron elastic structure functions at large momentum transfers
Kathy McCormick
1999-08-01
The cross section for elastic electron-deuteron scattering has been measured using the Hall A Facility of Jefferson Laboratory. Scattered electrons and recoiling deuterons were detected in coincidence in the two 4 GeV/c High Resolution Spectrometers (HRS) of Hall A. The deuteron elastic structure functions A(Q{sup 2}) and B(Q{sup 2}) have been extracted from these data. Results for the measurement of A(Q{sup 2}) in the range of 0.7 ≤ Q{sup 2} ≤ 6.0 (GeV/c){sup 2} are reported. Results for the magnetic structure function, B(Q{sup 2}), are presented in the range of 0.7 ≤ Q{sup 2} ≤ 1.35 (GeV/c){sup 2}. The results for both structure functions are compared to predictions of meson-nucleon based models, both with and without the inclusion of meson-exchange currents. The A(Q{sup 2}) results are compared to predictions of the dimensional scaling quark model and perturbative quantum chromodynamics. The results can provide insights into the transition from meson-nucleon to quark-gluon descriptions of the nuclear two-body system.
x- and xi-scaling of the Nuclear Structure Function at Large x
J. Arrington; C. S. Armstrong; T. Averett; O. K. Baker; L. de Bever; C. W. Bochna; W. Boeglin; B. Bray; R. D. Carlini; G. Collins; C. Cothran; D. Crabb; D. Day; J. A. Dunne; D. Dutta; R. Ent; B. W. Filippone; A. Honegger; E. W. Hughes; J. Jensen; J. Jourdan; C. E. Keppel; D. M. Koltenuk; R. Lindgren; A. Lung; D. J Mack; J. McCarthy; R. D. McKeown; D. Meekins; J. H. Mitchell; H. G. Mkrtchyan; G. Niculescu; I. Niculescu; T. Petitjean; O. Rondon; I. Sick; C. Smith; B. Terburg; W. F. Vulcan; S. A. Wood; C. Yan; J. Zhao; B. Zihlmann
2001-07-01
Inclusive electron scattering data are presented for {sup 2}H and Fe targets at an incident electron energy of 4.045 GeV for a range of momentum transfers from Q{sup 2} = 1 to 7 (GeV/c){sup 2}. Data were taken at Jefferson Laboratory for low values of energy loss, corresponding to values of Bjorken x greater than or near 1. The structure functions do not show scaling in x in this range, where inelastic scattering is not expected to dominate the cross section. The data do show scaling, however, in the Nachtmann variable {xi}. This scaling may be the result of Bloom Gilman duality in the nucleon structure function combined with the Fermi motion of the nucleons in the nucleus. The resulting extension of scaling to larger values of {xi} opens up the possibility of accessing nuclear structure functions in the high-x region at lower values of Q{sup 2} than previously believed.