Speaker
Description
The Relativistic Heavy Ion Collider (RHIC) has been serving the community as the first and only polarized proton-proton ($pp$) collider in the world, providing unique perspectives on the inner structure of the proton.
In particular, $W$ bosons produced at RHIC are used to probe the light flavor structure in the proton.
At leading order, $W$ bosons arise in $pp$ collisions via Drell-Yan type processes, $q\bar{q} \rightarrow W$, which directly provide sensitivity to the anti-quark densities in the proton.
The large momentum scale set by the $W$ mass allows for perturbative calculations needed for theory predictions.
The STAR experiment at RHIC measures the $W$ boson production in order to probe the flavor asymmetry between the $\bar{d}$ and $\bar{u}$ distributions.
The $W$ bosons produced at the STAR interaction point typically are typically tagged via their leptonic decay, $W \rightarrow e\nu$, which leaves a characteristically large imbalance in energy deposit in the STAR electromagnetic calorimeter (EMC).
The STAR barrel (BEMC) and endcap (EEMC) calorimeters cover the mid ($|\eta| < 1$) and intermediate ($1 < \eta < 2$) rapidities, respectively, providing kinematic coverage over a proton momentum fraction range of $0.06 < x < 0.4$.
Presented in this talk are the recent results of measurements of $W$ and $Z/\gamma^*$ cross sections and their ratios via leptonic-decay tagging, using the STAR $pp$ collision data at a center-of-mass energy of $\sqrt{s} = 510\,\mathrm{GeV}$ collected in 2011, 2012, 2013 and 2017, corresponding to an integrated luminosity of $\sim 700\,\mathrm{pb^{-1}}$.
