Polarized Antimatter in the Proton from Global QCD Analysis

Abstract

We present a global QCD analysis of spin-dependent parton distribution functions (PDFs) that includes the latest polarized W -lepton production data from the STAR collaboration at RHIC. These data allow the first data-driven extraction of a nonzero polarized light quark sea asymmetry ∆ū−∆ d within a global QCD framework with minimal theoretical assumptions. Within our simultaneous extraction of polarized PDFs, unpolarized PDFs, and pion and kaon fragmentation functions, we also extract a self-consistent set of antiquark polarization ratios ∆ū/ū and ∆ d/ d.

Sea Asymmetry from Polarized W Boson Production

“…We thank Jake Ethier and Wally Melnitchouk for the fruitful collaboration on the work in [9,10], which forms the basis for this contribution. We thank Felix Ringer and Werner Vogelsang for the code used for calculating the W -lepton cross sections.…”

“…For the first time we include this data in a full global QCD analysis using the JAM Monte Carlo framework, along with data on polarized lepton-nucleon DIS and polarized jet production [9]. We also perform a simultaneous fit of unpolarized and helicity PDFs in order to properly quantify the errors on both distributions.…”

Isovector helicity quark quasi-distributions inside a large Nc nucleon

“…The idea is tested at the STAR collaboration at RHIC and reported the polarized antiquark asymmetry [12][13][14]. Also, there are upated PDFs reflecting these experimental improvements [15,16].…”