Systematic studies on the nuclear parton distribution with photon and hadron productions in nuclear collisions at the LHC* *Supported by the National Key Research and Development Program of China (2018YFE0104700, 2018YFE0104800), the National Natural Science Foundation of China (12061141008, 12175085), and the Fundamental Research Funds for the Central Universities ( CCNU220N003)

Abstract

A systematic study on the impact of widely-used nuclear-modified parton distribution function (nPDF) parameterizations on the production of direct photons and charged hadrons is performed by employing a next-to-leading order Monte Carlo event generator JETPHOX in hadronic collisions at LHC energies. The nuclear modification factors of photon and charged hadron productions are studied in three types of collision systems, i.e., small ( and ), medium , and large , in a wide rapidity acceptance. The results illustrate that the direct photon production process is a sensitive probe to decipher the difference of the nPDF parameterization implementations, which provides new insights for the experimental measurements to refine the nuclear modifications of the parton distributions. To provide a benchmark for searching for quark gluon plasma in the upcoming small system measurements at LHC energies, we carry out detailed studies on the cold nuclear matter effect in collisions. Our outcomes show that the cold nuclear matter effects are negligible for the charged hadron production in collisions, which can be used as a baseline to subtract the initial state contribution.