Measurements of $W$ and $Z/\gamma^*$ cross sections and their ratios in $p+p$ collisions at RHIC

TL;DR

This paper reports measurements of $W$ and $Z/\gamma^*$ cross sections and ratios in proton-proton collisions at RHIC, providing data to constrain quark and antiquark parton distribution functions at high energy scales.

Contribution

It presents new high-precision measurements of $W$ and $Z/\gamma^*$ cross sections and ratios at RHIC, enhancing constraints on sea quark distributions in global analyses.

Findings

Cross sections and ratios are sensitive to quark and antiquark PDFs.

Results provide constraints on the $\bar{d}/\bar{u}$ and $\bar{u}-\bar{d}$ distributions.

Data from three years improve statistical precision.

Abstract

We report on the $W$ and $Z/\gamma^*$ differential and total cross sections as well as the $W^+$/$W^-$ and $(W^+ + W^-)$/$(Z/\gamma^*)$ cross-section ratios measured by the STAR experiment at RHIC in $p+p$ collisions at $\sqrt{s} = 500$ GeV and $510$ GeV. The cross sections and their ratios are sensitive to quark and antiquark parton distribution functions. In particular, at leading order, the $W$ cross-section ratio is sensitive to the $\bar{d}/\bar{u}$ ratio. These measurements were taken at high $Q^2 \sim M_W^2,M_Z^2$ and can serve as input into global analyses to provide constraints on the sea quark distributions. The results presented here combine three STAR data sets from 2011, 2012, and 2013, accumulating an integrated luminosity of 350 pb$^{-1}$. We also assess the expected impact that our $W^+/W^-$ cross-section ratios will have on various quark distributions, and find sensitivity to the $\bar{u}-\bar{d}$ and $\bar{d}/\bar{u}$ distributions.