The Drell-Yan nuclear modification due to the nuclear effects of nPDFs and initial-state parton energy loss

Abstract

By globally analyzing nuclear Drell-Yan data including all incident energies, the nuclear effects of nPDFs and initial-state parton energy loss are investigated. Based on Landau-Pomeranchuk-Migdal (LPM) regime, the calculations are carried out by means of the analytic parametrizations of quenching weights derived from the Baier-Dokshitzer-Mueller-Peign$\acute{e}$-Schiff (BDMPS) formalism and using the new EPPS16 nPDFs. It is found that the results are in good agreement with the data and the role of the energy loss effect on the suppression of Drell-Yan ratios is prominent, especially for low-mass Drell-Yan measurements. The nuclear effects of nPDFs becomes more obvious with the nuclear mass number A, the same as the energy loss effect. By global fit, the transport coefficient extracted is $\hat{q}=0.26\pm0.04$ GeV$^{2}$/fm. In addition, to avoid diminishing the QCD NLO correction on the data form of Drell-Yan ratios, the separate calculations about the Compton differential cross section ratios $R_{Fe(W)/C}(x_{F})$ at 120GeV are performed, which provides a feasible way to better distinguish the gluon energy loss in Compton scattering. It is found that the role of the initial-state gluon energy loss on the suppression of Compton scattering rations is not very important and becomes disappear with the increase of $x_{F}$.