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

Nuclear modification factors of single hadrons and dihadrons at large transverse momentum ( p_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 q̂ characterizing the interaction between the parton jet and the produced medium. By confronting 6 current sets of NLO parton FFs for large p_T hadron productions, we extract q̂ quantitatively via a global fit to data for both single hadron and dihadron suppressions and obtain q̂/T^3 = 4.74 - 6.72 at T = 370 MeV in central Au+Au collisions at √(s_NN)=200 GeV, and q̂/T^3 = 3.07 - 3.98 at T = 480 MeV in central Pb+Pb collisions at √(s_NN)=2.76 TeV. The numerical results show that the uncertainties for q̂ extraction are brought by the different contributions of gluon-to-hadron in the six sets of FFs due to gluon energy loss being 9/4 times of quark energy loss.