Title: Estimating nonlinear effects in forward dijet production in ultra-peripheral heavy ion collisions at the LHC

Abstract

Using the framework that interpolates between the leading power limit of the color glass condensate and the high energy (or k_T ) factorization we calculate the direct component of the forward dijet production in ultra-peripheral Pb–Pb collisions atCMenergy 5.1 TeV per nucleon pair. The formalism is applicablewhen the average transversemomentum of the dijet system P_T is much bigger than the saturation scale Q_s , P_T >> Qs , while the imbalance of the dijet system can be arbitrary. The cross section is uniquely sensitive to theWeizsäcker–Williams (WW) unintegrated gluon distribution, which is far less known from experimental data than the most common dipole gluon distribution appearing in inclusive small-x processes. We also calculated cross sections and nuclear modification ratios using WW gluon distribution obtained from the dipole gluon density through the Gaussian approximation. The dipole gluon distribution used to get WW was fitted to the inclusive HERA data with the nonlinear extension of unified BFKL+DGLAP evolution equation. The saturation effects are visible but rather weak for realistic p_T cut on the dijet system, reaching about 20% with the cut as low as 6 GeV. Finally, we find that the LO collinear factorization with nuclear leading-twist shadowing predicts quite similar effects.

Authors:

Kotko, P.; Kutak, K.; Sapeta, S.; Stasto, A. M.; Strikman, M.

Publication Date:

Sat May 27 00:00:00 EDT 2017

Research Org.:

Pennsylvania State Univ., University Park, PA (United States)

Sponsoring Org.:

USDOE Office of Science (SC)

OSTI Identifier:

1361943

Alternate Identifier(s):

OSTI ID: 1389276

Grant/Contract Number:  

FG02-93ER40771; SC0002145; 2015/17/B/ST2/01838; 2013/10/E/ST2/00656; FG02-93ER20097

Resource Type:

Published Article

Journal Name:

European Physical Journal. C, Particles and Fields

Additional Journal Information:

Journal Name: European Physical Journal. C, Particles and Fields Journal Volume: 77 Journal Issue: 5; Journal ID: ISSN 1434-6044

Publisher:

Springer

Country of Publication:

Germany

Language:

English

Subject:

74 ATOMIC AND MOLECULAR PHYSICS