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STAR
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, Delta 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 Delta 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 Delta g(x,Q^2) is positive for x > 0.05.
