Speaker
Mr
Carl Gagliardi
(Texas A&M University)
Description
The STAR Collaboration is performing a wide range of measurements to determine the gluon and antiquark helicity distributions in the proton. The longitudinal double-spin asymmetries, $A_{LL}$, for inclusive jet and dijet production provide direct access to the gluon polarization. The parity-violating single-spin asymmetries, $A_L$, for $W^{+/-}$ production are sensitive to the $\bar{u}$ and $\bar{d}$ antiquark polarizations. STAR recorded large polarized proton data sets in 2009 at $\sqrt{s}$ = 200 GeV and in 2012 and 2013 at $\sqrt{s}$ = 510 GeV. The 2009 mid-rapidity inclusive jet $A_{LL}$ results place stringent new constraints on the polarized gluon distribution and provide evidence for positive gluon polarization in the Bjorken-$x$ region $x > 0.05$. The 2012 $W$ asymmetry results show a preference for a sizable, positive $\bar{u}$ antiquark polarization in the range $0.05 < x < 0.2$. The inclusive jet $A_{LL}$ and $W$ $A_L$ measurements will be discussed, and status reports will be provided regarding similar measurements with the more recent data sets.
Primary author
Mr
Carl Gagliardi
(Texas A&M University)
