Longitudinal double-spin asymmetry for inclusive jet and dijet production in polarized proton collisions at $\sqrt{s}=200$ GeV

Abstract

We report high-precision measurements of the longitudinal double-spin asymmetry, $A_{LL}$, for midrapidity inclusive jet and dijet production in polarized $pp$ collisions at a center-of-mass energy of $\sqrt{s}=200\mathrm{GeV}$. The new inclusive jet data are sensitive to the gluon helicity distribution, $\hat{I}”g(x,Q^2)$, for gluon momentum fractions in the range from $x\simeq 0.05$ to $x\simeq 0.5$, while the new dijet data provide further constraints on the $x$ dependence of $\hat{I}”g(x,Q^2)$. The results are in good agreement with previous measurements at $\sqrt{s}=200\mathrm{GeV}$ and with recent theoretical evaluations of prior world data. Our new results have better precision and thus strengthen the evidence that $\hat{I}”g(x,Q^2)$ is positive for $x>0.05$.

14 pages, 4 figures