Abstract
The production of the massive bosons $Z^0$ and $W^{\pm}$ could provide an excellent tool to study cold nuclear matter effects and the modifications of nuclear parton distribution functions (nPDFs) relative to 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 $\sqrt{s_{NN}}=63$TeV and in Pb+Pb collisions at $\sqrt{s_{NN}}=39$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 in the massive vector boson productions 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 W boson will be reduced significantly as compared to that at the LHC. 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 $Z^0$ and $W$ in the future HIC.
Highlights
The production of massive vector bosons Z 0/W ± in highenergy nuclear collisions has long been regarded as an excellent tool to probe the initial-state cold nuclear matter (CNM)Future Circular Collider (FCC) at CERN [12], and the Circular Electron Positron Collider with a subsequent Super proton–proton Collider (CEPC-SPPC) in China [13], the vector gauge boson productions may still play a very important role in investigating the high-density QCD in the initial state and making precise constraints on CNM effects and nuclear parton distribution functions at very small x
The results demonstrate that sea quarks play an important role in the Z 0 boson production, especially at the future heavy-ion collisions (HIC)
Since isospin effect is very weak at the central rapidity, the suppression on the W boson production at the future HIC is mainly due to the shadowing effect on the nuclear sea quarks
Summary
The production of massive vector bosons Z 0/W ± in highenergy nuclear collisions has long been regarded as an excellent tool to probe the initial-state cold nuclear matter (CNM). Recent studies have shown that the heavy gauge boson production in nuclear reactions at the LHC energies could shed light on several CNM effects, especially the shadowing and anti-shadowing effects (for Z /W ) and isospin effect (for W ±) [11,19,20,21,22,23]. With much higher colliding energies available in future HIC, the vector boson would be produced by initial partons with the much smaller momentum fraction x, in which region the shadowing effect will be more pronounced and sea quarks and gluons may play a more important role. 2, we briefly introduce the framework of our calculation and compute the nuclear modification ratios for Z 0 boson rapidity distributions and the charged lepton pseudorapidity dependence of W ± production in Pb + Pb and p + Pb collisions in the future HIC.
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