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Title: Chiral dynamics and partonic structure at large transverse distances

Abstract

We study large-distance contributions to the nucleon's parton densities in the transverse coordinate (impact parameter) representation based on generalized parton distributions (GPDs). Chiral dynamics generates a distinct component of the partonic structure, located at momentum fractions x < or approx. M{sub {pi}}/M{sub N} and transverse distances b{approx}1/M{sub {pi}}. We calculate this component using phenomenological pion exchange with a physical lower limit in b (the transverse 'core' radius estimated from the nucleon's axial form factor, R{sub core}=0.55 fm) and demonstrate its universal character. This formulation preserves the basic picture of the 'pion cloud' model of the nucleon's sea quark distributions, while restricting its application to the region actually governed by chiral dynamics. It is found that (a) the large-distance component accounts for only {approx}1/3 of the measured antiquark flavor asymmetry d-u at x{approx}0.1; (b) the strange sea quarks s and s are significantly more localized than the light antiquark sea; (c) the nucleon's singlet quark size for x<0.1 is larger than its gluonic size, <b{sup 2}>{sub q+q}><b{sup 2}>{sub g}, as suggested by the t-slopes of deeply-virtual Compton scattering and exclusive J/{psi} production measured at HERA and FNAL. We show that our approach reproduces the general N{sub c}-scaling of parton densities inmore » QCD, thanks to the degeneracy of N and {delta} intermediate states in the large-N{sub c} limit. We also comment on the role of pionic configurations at large longitudinal distances and the limits of their applicability at small x.« less

Authors:
 [1];  [2]
  1. Department of Physics, Pennsylvania State University, University Park, Pennsylvania 16802 (United States)
  2. Theory Center, Jefferson Lab, Newport News, Virginia 23606 (United States)
Publication Date:
OSTI Identifier:
21313484
Resource Type:
Journal Article
Journal Name:
Physical Review. D, Particles Fields
Additional Journal Information:
Journal Volume: 80; Journal Issue: 11; Other Information: DOI: 10.1103/PhysRevD.80.114029; (c) 2009 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0556-2821
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; ANTIQUARKS; ASYMMETRY; CHIRALITY; COMPTON EFFECT; COMPUTERIZED SIMULATION; CONFIGURATION; DENSITY; DISTRIBUTION; FLAVOR MODEL; FORM FACTORS; HERA STORAGE RING; IMPACT PARAMETER; INTERMEDIATE STATE; J PSI-3097 MESONS; NUCLEONS; PARTICLE PRODUCTION; PIONS; QUANTUM CHROMODYNAMICS; QUARK MATTER; SCATTERING

Citation Formats

Strikman, M., and Weiss, C. Chiral dynamics and partonic structure at large transverse distances. United States: N. p., 2009. Web. doi:10.1103/PHYSREVD.80.114029.
Strikman, M., & Weiss, C. Chiral dynamics and partonic structure at large transverse distances. United States. doi:10.1103/PHYSREVD.80.114029.
Strikman, M., and Weiss, C. Tue . "Chiral dynamics and partonic structure at large transverse distances". United States. doi:10.1103/PHYSREVD.80.114029.
@article{osti_21313484,
title = {Chiral dynamics and partonic structure at large transverse distances},
author = {Strikman, M. and Weiss, C.},
abstractNote = {We study large-distance contributions to the nucleon's parton densities in the transverse coordinate (impact parameter) representation based on generalized parton distributions (GPDs). Chiral dynamics generates a distinct component of the partonic structure, located at momentum fractions x < or approx. M{sub {pi}}/M{sub N} and transverse distances b{approx}1/M{sub {pi}}. We calculate this component using phenomenological pion exchange with a physical lower limit in b (the transverse 'core' radius estimated from the nucleon's axial form factor, R{sub core}=0.55 fm) and demonstrate its universal character. This formulation preserves the basic picture of the 'pion cloud' model of the nucleon's sea quark distributions, while restricting its application to the region actually governed by chiral dynamics. It is found that (a) the large-distance component accounts for only {approx}1/3 of the measured antiquark flavor asymmetry d-u at x{approx}0.1; (b) the strange sea quarks s and s are significantly more localized than the light antiquark sea; (c) the nucleon's singlet quark size for x<0.1 is larger than its gluonic size, <b{sup 2}>{sub q+q}><b{sup 2}>{sub g}, as suggested by the t-slopes of deeply-virtual Compton scattering and exclusive J/{psi} production measured at HERA and FNAL. We show that our approach reproduces the general N{sub c}-scaling of parton densities in QCD, thanks to the degeneracy of N and {delta} intermediate states in the large-N{sub c} limit. We also comment on the role of pionic configurations at large longitudinal distances and the limits of their applicability at small x.},
doi = {10.1103/PHYSREVD.80.114029},
journal = {Physical Review. D, Particles Fields},
issn = {0556-2821},
number = 11,
volume = 80,
place = {United States},
year = {2009},
month = {12}
}