Gluon polarization and jet production at STAR

At RHIC kinematics, polarized jet hadroproduction is dominated by $gg$ and $qg$ scattering, making the jet longitudinal double-spin asymmetry, $A_{LL}$, sensitive to gluon polarization in the nucleon. I will present STAR results of $A_{LL}$ from inclusive jet and dijet measurements for the RHIC 2006 run totaling 5.5 pb$^{-1}$ of integrated luminosity with 55% beam polarization at center-of-mass energy 200 GeV. I will also present preliminary results from the analyses of data from the 2009 run, which collected a much larger sample (25 pb$^{-1}$ with 57% polarization) at 200 GeV. The results are compared with theoretical calculations of $A_{LL}$ based on various models of the polarized gluon distribution function in the nucleon. The STAR data place significant constraints on allowed theoretical models.