The study of gluon energy loss in cold nuclear matter from J / ψ production

Abstract

The energy loss effects of the incident quark, gluon, and the color octet cc on J/ψ suppression in p-A collisions are studied by means of the experimental data at E866, RHIC, and LHC energy. We extracted the transport coefficient for gluon energy loss from the E866 experimental data in the middle xF region (0.20 < xF < 0.65) based on the Salgado-Wiedemann (SW) quenching weights and the recent EPPS16 nuclear parton distribution functions together with nCTEQ15. It was determined that the difference between the values of the transport coefficient for light quark, gluon, and heavy quark in cold nuclear matter is very small. The theoretical results modified by the parton energy loss effects are consistent with the experimental data for E866 and RHIC energy, and the gluon energy loss plays a remarkable role on J/ψ suppression in a broad variable range. Because the corrections of the nuclear parton distribution functions in the J/ψ channel are significant at LHC energy level, the nuclear modification due to the parton energy loss is minimal. It is worth noting that we use the color evaporation model (CEM) at leading order to compute the p-p baseline, and the conclusion in this paper is CEM model dependent.

The study of the incoming parton energy loss effect on the NLO nuclear Drell–Yan ratios

“…From the above analysis, we can arrive at the conclusion that the influence of gluon energy loss embedded in the QCD next-to-leading order correction is not significant for the Drell-Yan differential cross section ratio from E906, E866 and Na3 experiment. However, in our previous work [28], at the leading order calculation, we find that the incoming gluon energy loss in the initial state plays an important role (approximately 10%) on the J/ψ suppression in a broad variable range at E866 and RHIC energies. The reason may be that the influence of the QCD next-to-leading order correction on the Drell-Yan differential cross section ratio as a function of the quark momentum fraction…”

“…) minimizes the QCD next-to-leading order correction, it is very difficult to accurately constrain the gluon energy loss embodied in the primary next- to-leading order Compton scattering subprocess from the available data on Drell-Yan differential cross section ratio. In our previous work [28], we find that J/ψ production process provides a good opportunity to constrain the gluon energy loss. By fitting the nuclear Drell-Yan data including the latest E906 data, and fixing the value of the incoming gluon transport coefficientq g to 0.31±0.02 GeV 2 fm −1 [28], the transport coefficientq q is obtained by minimizing χ 2 with the CERN subroutine MINUIT [32] and the SW quenching weights [26].…”

“…In our previous work [28], we find that J/ψ production process provides a good opportunity to constrain the gluon energy loss. By fitting the nuclear Drell-Yan data including the latest E906 data, and fixing the value of the incoming gluon transport coefficientq g to 0.31±0.02 GeV 2 fm −1 [28], the transport coefficientq q is obtained by minimizing χ 2 with the CERN subroutine MINUIT [32] and the SW quenching weights [26]. One standard deviation of the optimum parameter correspond to an increase of χ 2 by 1 unit from its minimum c min 2 .…”

“…The same as the incoming quarks, the incoming gluons also lose some energy when propagating through the nucleus in the Drell-Yan production. Here, by using the value of the parameter ˆ=  q 0.31 0.02 g GeV 2 fm −1 [28] extracted from the E866 J/ψ experimental data [34] at the range 0.20<x F <0.65, we investigate the gluon energy loss effect on the suppression of the nuclear Drell-Yan production. The calculations obtained with both the quark and gluon energy loss effects are shown as the dotted lines in figures 1-3.…”

“…It is found that the transport coefficient ˆ=  q 0.32 0.04 q GeV 2 fm −1 extracted with the SW quenching weights is approximately equal to the value ˆ=  q 0.37 0.05 q GeV 2 fm −1 extracted with the analytic parametrizations of BDMPS quenching weights. In addition, by means of J/ψ production in p-A collisions, we considered the initial-state energy loss from the quark and gluon of the incident proton, and extracted the transport coefficient qg for the incoming gluon ( ˆ=  q 0.31 0.02 g GeV 2 fm −1 ) [28] with the SW quenching weights for gluon. In view of the E906 measurements providing high statistics and high precision data, in this work we will do a new global analysis of the nuclear Drell-Yan data including the latest E906 data with the SW quenching weights.…”