Speakers
Description
We present the preliminary results of unpolarized cross section and transverse single spin asymmetry (TSSA) of $Z^{0}$ measured by the STAR experiment. The cross section results combine 500/510 GeV $p$$+$$p$ data from 2011, 2012, 2013 and 2017, corresponding to a total luminosity of 700 pb$^{-1}$. The differential $Z^{0}$ cross section, measured as a function of the boson's transverse momentum, provides important constraints on the energy dependence of the transverse momentum dependent parton distribution functions (TMDs). The TSSA of $Z^{0}$ is measured using 510 GeV $p^{\uparrow}$$+$$p$ data from 2017 with the integrated luminosity of 350 pb$^{-1}$. This observable is sensitive to one of the TMDs, the Sivers function, which is predicted to have the opposite sign in $p+p\rightarrow W/Z+ X$ from that observed in semi-inclusive deep inelastic scatterings. Our data aim to investigate the non-universality of the Sivers function.
