Speaker
Description
The Solenoidal Tracker at the Relativistic Heavy Ion Collider (STAR) experiment probes the gluon helicity distribution $\Delta G(x)$ using collisions of longitudinally polarized protons at $\sqrt{s} = $ 200 GeV and $\sqrt{s} =$ 510 GeV. Access to $\Delta G(x)$ is possible through the double spin asymmetries $A_{LL}$ in gluon-dominated hard scattering processes of inclusive jet and di-jet production.
Previously published results on inclusive jet processes at $\sqrt{s}=$ 200 GeV and $|\eta_{\mathrm{jet}}| < 1$ are based on data collected in 2009, which correspond to an integrated luminosity ($L$) of 20 pb$^{-1}$ with an average beam polarization ($P$) of 57%. When included in perturbative QCD analysis of global data, they provide evidence for positive gluon polarization for a momentum fraction $x > 0.05$ at a hard perturbative scale $Q^2 = 10$ GeV$^2$. Additional data were collected in 2015 with an approximately twice larger figure of merit $\left(LP^4\right)$. This contribution will cover the status of the analysis of 2015 inclusive jet and di-jet data, as well as, the jet measurements based on the most recent high-luminosity 510 GeV data collected in 2013, which will further constrain $\Delta G(x)$ at lower $x$.
