This contribution reports on the first measurement of the longitudinal double-spin asymmetry $A_{ LL}$ for the inclusive production of jets in polarized proton-proton collisions at $\sqrt{ s}=200 \mathrm{ GeV}$. The data were collected with STAR at RHIC in the years 2003 and 2004, and correspond to a sampled integrated luminosity of $0.3 \mathrm{ pb}^{ -1}$ with beam polarizations up to 45%. The results on $A_{ LL}$ cover jet transverse momenta $5 < p_{ T} < 17 \mathrm{ GeV/c}$ and agree with perturbative QCD evaluations based on deep-inelastic scattering parametrizations for the gluon polarization in the proton. The results disfavor large positive gluon polarization in the polarized proton.
Categories: hep-ex