Probing shadowed nuclear sea with massive gauge bosons in the future heavy-ion collisions

The production of the massive bosons Z⁰ and W^± could provide an excellent tool to study cold nuclear matter effects and the modifications of nuclear parton distribution functions (nPDFs) relative to the parton distribution functions (PDFs) of a free proton in high-energy nuclear reactions at the LHC as well as in heavy-ion collisions (HIC)with much higher center-of-mass energies available in the future colliders. In this paper we calculate the rapidity and transverse momentum distributions of the vector boson and their nuclear modification factors in p + Pb collisions at @√(s_NN) = 63 TeV and in Pb + Pb collisions at @@√(s_NN) = 39 TeV in the framework of perturbative QCD by utilizing three parametrization sets of nPDFs: EPS09, DSSZ, and nCTEQ. It is found that in heavy-ion collisions at such high colliding energies, both the rapidity distribution and the transverse momentum spectrum of vector bosons are considerably suppressed in wide kinematic regions with respect to p + p reactions due to large nuclear shadowing effect. We demonstrate that the massive vector boson production processes with sea quarks in the initial state may give more contributions than those with valence quarks in the initial state; therefore in future heavy-ion collisions the isospin effect is less pronounced and the charge asymmetry of the W boson will be reduced significantly as compared to that at the LHC. A large difference between results with nCTEQ and results with EPS09 and DSSZ is observed in nuclear modifications of both rapidity and p_T distributions of Z⁰ and W in the future HIC. (orig.)