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Title: Quark contribution to the small-x evolution of color dipole

Abstract

The small-x deep inelastic scattering in the saturation region is governed by the nonlinear evolution of Wilson-lines operators. In the leading logarithmic approximation it is given by the Balitsky-Kovchegov (BK) equation for the evolution of color dipoles. In the next-to-leading order (NLO) the nonlinear equation gets contributions from quark and gluon loops. In this paper I calculate the quark-loop contribution to small-x evolution of Wilson lines in the NLO. It turns out that there are no new operators at the one-loop level--just as at the tree level, the high-energy scattering can be described in terms of Wilson lines. In addition, from the analysis of quark loops I find that the argument of coupling constant in the BK equation is determined by the size of the parent dipole rather than by the size of produced dipoles. These results are to be supported by future calculation of gluon loops.

Authors:
 [1];  [2]
  1. Physics Department, Old Dominion University, Norfolk Virginia 23529 (United States)
  2. (United States)
Publication Date:
OSTI Identifier:
20933216
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. D, Particles Fields; Journal Volume: 75; Journal Issue: 1; Other Information: DOI: 10.1103/PhysRevD.75.014001; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; APPROXIMATIONS; COLOR MODEL; COUPLING CONSTANTS; DEEP INELASTIC SCATTERING; DIPOLES; EQUATIONS; GLUONS; MATHEMATICAL EVOLUTION; NONLINEAR PROBLEMS; QUANTUM CHROMODYNAMICS; QUARKS

Citation Formats

Balitsky, Ian, and Theory Group, Jefferson Lab, 12000 Jefferson Avenue, Newport News, Virginia 23606. Quark contribution to the small-x evolution of color dipole. United States: N. p., 2007. Web. doi:10.1103/PHYSREVD.75.014001.
Balitsky, Ian, & Theory Group, Jefferson Lab, 12000 Jefferson Avenue, Newport News, Virginia 23606. Quark contribution to the small-x evolution of color dipole. United States. doi:10.1103/PHYSREVD.75.014001.
Balitsky, Ian, and Theory Group, Jefferson Lab, 12000 Jefferson Avenue, Newport News, Virginia 23606. Mon . "Quark contribution to the small-x evolution of color dipole". United States. doi:10.1103/PHYSREVD.75.014001.
@article{osti_20933216,
title = {Quark contribution to the small-x evolution of color dipole},
author = {Balitsky, Ian and Theory Group, Jefferson Lab, 12000 Jefferson Avenue, Newport News, Virginia 23606},
abstractNote = {The small-x deep inelastic scattering in the saturation region is governed by the nonlinear evolution of Wilson-lines operators. In the leading logarithmic approximation it is given by the Balitsky-Kovchegov (BK) equation for the evolution of color dipoles. In the next-to-leading order (NLO) the nonlinear equation gets contributions from quark and gluon loops. In this paper I calculate the quark-loop contribution to small-x evolution of Wilson lines in the NLO. It turns out that there are no new operators at the one-loop level--just as at the tree level, the high-energy scattering can be described in terms of Wilson lines. In addition, from the analysis of quark loops I find that the argument of coupling constant in the BK equation is determined by the size of the parent dipole rather than by the size of produced dipoles. These results are to be supported by future calculation of gluon loops.},
doi = {10.1103/PHYSREVD.75.014001},
journal = {Physical Review. D, Particles Fields},
number = 1,
volume = 75,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
  • The small-x deep inelastic scattering in the saturation region is governed by the non-linear evolution of Wilson-lines operators. In the leading logarithmic approximation it is given by the BK equation for the evolution of color dipoles. In the NLO the nonlinear equation gets contributions from quark and gluon loops. In this paper I calculate the quark-loop contribution to small-x evolution of Wilson lines in the NLO. It turns out that there are no new operators at the one-loop level--just as at the tree level, the high-energy scattering can be described in terms of Wilson lines. In addition, from the analysismore » of quark loops I find that the argument of coupling constant in the BK equation is determined by the size of the parent dipole rather than by the size of produced dipoles. These results are to be supported by future calculation of gluon loops.« less
  • The problem of kinematic effects in gluon and color dipole cascades is addressed in the large N{sub c} limit of SU(N{sub c}) Yang-Mills theory. We investigate the tree-level multigluon components of the gluon light-cone wave functions in the light-cone gauge keeping the exact kinematics of the gluon emissions. We focus on the components with all helicities identical to the helicity of the incoming gluon. The recurrence relations for the gluon wave functions are derived. In the case when the virtuality of the incoming gluon is neglected the exact form of the multigluon wave function is obtained. Furthermore, we propose anmore » approximate scheme to treat the kinematic effects in the color dipole evolution kernel. The new kernel entangles longitudinal and transverse degrees of freedom and leads to a reduced diffusion in the impact parameter. When evaluated in the next-to-leading logarithmic (NLL) accuracy, the kernel reproduces the correct form of the double logarithmic terms of the dipole size ratios present in the exact NLL dipole kernel. Finally, we analyze the scattering of the incoming gluon light-cone components off a gluon target and the fragmentation of the scattered state into the final state. The equivalence of the resulting amplitudes and the maximally helicity-violating amplitudes is demonstrated in the special case when the target gluon is far in rapidity from the evolved gluon wave function.« less
  • We consider the contribution to psi hadroproduction due to the elementary subprocess qq-bar..-->..psiGG. The color-singlet nature and observed spin-parity of the psi are incorporated and the normalization of the cross section is predicted by the psi wave function at the origin as measured in the leptonic psi decay. We expect this process to dominate the difference in psi production from particle versus antiparticle beams. The energy dependence of psi production as well as distributions in x/sub F/ and P/sub T/ are predicted.