Extracting the jet transport coefficient from hadron suppressions by confronting current NLO parton fragmentation functions

Abstract

Nuclear modification factors of single hadrons and dihadrons at large transverse momentum ($p_{\mathrm{T}}$) in high-energy heavy-ion collisions are studied in a next-to-leading-order (NLO) perturbative QCD parton model. Parton fragmentation functions (FFs) in $A+A$ collisions are modified due to jet energy loss which is proportional to the jet transport coefficient $\hat{q}$ characterizing the interaction between the parton jet and the produced medium. By confronting 6 current sets of NLO parton FFs for large $p_{\mathrm{T}}$ hadron productions, we extract $\hat{q}$ quantitatively via a global fit to data for both single hadron and dihadron suppressions, and obtain $\hat{q}/T^3=4.74-6.72$ at $T=370$ MeV in central $Au+Au$ collisions at $\sqrt{s_{\mathrm{NN}}}=200$ GeV, and $\hat{q}/T^3=3.07-3.98$ at $T=480$ MeV in central $Pb+Pb$ collisions at $\sqrt{s_{\mathrm{NN}}}=2.76$ TeV. The numerical results show that the uncertainties for $\hat{q}$ extraction are brought by the different contributions of gluon-to-hadron in the 6 sets of FFs due to gluon energy loss being $9/4$ times of quark energy loss.

Comments: 16 pages, 21 figures