Measurements of $W^+$ and $W^-$ cross sections and their ratio in $pp$ collisions at STAR

While the unpolarized valence quark ($d$ and $u$) distributions are well determined from DIS and $pp/par{p}$ experiments, their sea (anti-)quark counterparts, $ar{d}$ and $ar{u}$, are much less constrained, in particular, near the valence region (momentum fraction, $x sim 0.2$).

Measurements of $W^+$ and $W^-$ production in $pp$ collider experiments can be used to probe the $ar{d}$ and $ar{u}$ at a large $Q^2$ set by the $W$ mass.

Presented in this talk are the latest updates of $W^+$ and $W^-$ cross sections and their ratio using the STAR $pp$ collision data at a center-of-mass energy of $sqrt{s} = 510,mathrm{GeV}$ collected in 2017, corresponding to an integrated luminosity of $350,mathrm{pb^{-1}}$.

The measurements were performed by tagging leptons from the weak decay channel ($W