Speaker
Description
The production of jets from polarized p+p collisions at STAR is dominated by quark-gluon and gluon-gluon scattering. The di-jet double spin asymmetry ($A_{LL}$) is sensitive to the polarized gluon distribution ($\Delta G$). Di-jets are also advantageous because the parton momentum fraction, x, of initial partons may be reconstructed to first order from the final state measurements. Both jet (PRL 115,092002) and di-jet (arXiv:1610.06616) $A_{LL}$ measurements at $\sqrt{s}$ = 200 GeV have helped to constrain $\Delta G$ in the range $0.05 < x < 0.3$. In 2012, data were collected at $\sqrt{s}$ = 510 GeV in order to probe lower values of x, these data are consistent with the $\sqrt{s}$ = 200 GeV results in the overlapping $x_T$ region. Jet and di-jet preliminary $A_{LL}$ results have been released and will soon be incorporated into theoretical fits. In 2013, high luminosity data, with an estimated 250 pb$^{-1}$ of integrated luminosity were collected at $\sqrt{s}$ = 510 GeV. These data have a figure of merit $\approx$3 times that of the 2012 data. An update on the di-jet $A_{LL}$ measurement will be presented using polarized p+p data collected at STAR during 2013.
