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We report measurements of the longitudinal double-spin asymmetry, ALL, for inclusive jet and dijet production in polarized proton-proton collisions at midrapidity and center-of-mass energy s√ = 510 GeV, using the high luminosity data sample collected by the STAR experiment in 2013. These measurements complement and improve the precision of previous STAR measurements at the same center-of-mass energy that probe the polarized gluon distribution function at partonic momentum fraction 0.015 ≲x≲ 0.25. The dijet asymmetries are separated into four jet-pair topologies, which provide further constraints on the x dependence of the polarized gluon distribution function. These measurements are in agreement with previous STAR measurements and with predictions from current next-to-leading order global analyses. They provide more precise data at low dijet invariant mass that will better constraint the shape of the polarized gluon distribution function of the proton.
We present measurements of the differential cross sections of inclusive J/ψ meson production as a function of transverse momentum (pJ/ψT) using the μ+μ− and e+e− decay channels in proton+proton collisions at center-of-mass energies of 510 and 500 GeV, respectively, recorded by the STAR detector at the Relativistic Heavy Ion Collider. The measurement from the μ+μ− channel is for 0 <pJ/ψT< 9 GeV/c and rapidity range |yJ/ψ|< 0.4, and that from the e+e− channel is for 4 <pJ/ψT< 20 GeV/c and |yJ/ψ|< 1.0. The ψ(2S) to J/ψ ratio is also measured for 4 <pmesonT< 12 GeV/c through the e+e− decay channel. Model calculations, which incorporate different approaches toward the J/ψ production mechanism, are compared with experimental results and show reasonable agreement within uncertainties.