Jet measurements in polarized p+p collisions at STAR at RHIC

Jet production in polarized $p+p$ collisions at $\sqrt{s}=200$ GeV and $\sqrt{s}=500$ GeV provides a powerful probe to study gluons inside the proton. The Solenoidal Tracker at RHIC (STAR) has the capability, with nearly full azimuthal ($2\pi$) coverage, to reconstruct jets at mid-rapidity ($|\eta| < 1$)\mathrm{.}ThelatestSTARinclusivejetlongitudinaldouble-spinasymmetry$A_{LL}$measuredin200GeV$p+p$ collisions provides better constraints on the polarized gluon distribution $\mathrm{\Delta }g(x)$ for $0.05<x<0.2$ than previous measurements. A recent global QCD fit (DSSV 2014) which includes the 2009 RHIC results provides the first evidence of non-zero gluon contribution to the proton spin. A new inclusive jet cross section using the anti-$k_T$ algorithm provides potential insights into the unpolarized gluon distribution function, and the new inclusive jet $A_{LL}$ measurement in 510 GeV $p+p$ collisions shows consistent $x_T$ scaling with the 200 GeV result. Future measurements with continuing high energy polarized proton-proton running at $\sqrt{s}=500$ GeV at RHIC and detector upgrades in the forward direction will explore the gluonic contribution to the proton spin at low $x$ region.