Abstract
We report the first measurement of the inclusive jet and the dijet longitudinal double-spin asymmetries, $A_{LL}$, at midrapidity in polarized $pp$ collisions at a center-of-mass energy $\sqrt{s} = 510$ GeV. The inclusive jet $A_{LL}$ measurement is sensitive to the gluon helicity distribution down to a gluon momentum fraction of $x\approx 0.015$, while the dijet measurements, separated into four jet-pair topologies, provide constraints on the $x$ dependence of the gluon polarization. Both results are consistent with previous measurements made at $\sqrt{s}= 200$ GeV in the overlapping kinematic region, $x > 0.05$, and show good agreement with predictions from recent next-to-leading order global analyses.
Highlights
The proton consists of quarks and antiquarks, bound by gluons
We report the first measurement of the inclusive jet and the dijet longiptudffiffiinal double-spin asymmetries, ALL, at midrapidity in polarized pp collisions at a center-of-mass energy s 1⁄4 510 GeV
The results have been incorporated, along with inclusive and semi-inclusive lepton-proton scattering data, into the recent DSSV14 [13] and NNPDFpol1.1 [14] next-to-leading order (NLO) perturbative QCD global analyses. These extractions of the helicity parton distribution functions (PDFs) indicate that, at momentum transfer scale of Q2 1⁄4 10 ðGeV=cÞ2 and for momentum fractions x > 0.05 that are sampled by the included Relativistic Heavy Ion Collider (RHIC) data, gluon spins contribute approximately 40% of the total proton spin
Summary
The proton consists of quarks and antiquarks, bound by gluons. The gluons provide about half of the momentum of the proton (see e.g., [1]), and their interactions provide most of the mass [2,3]. The results have been incorporated, along with inclusive and semi-inclusive lepton-proton scattering data, into the recent DSSV14 [13] and NNPDFpol1.1 [14] next-to-leading order (NLO) perturbative QCD global analyses These extractions of the helicity parton distribution functions (PDFs) indicate that, at momentum transfer scale of Q2 1⁄4 10 ðGeV=cÞ2 and for momentum fractions x > 0.05 that are sampled by the included RHIC data, gluon spins contribute approximately 40% of the total proton spin. The s 1⁄4 510 GeV dijet asymmetries here are separated into four pseudorapidity topologies as a that facilitate the extraction of x-dependent function of the dijet invariant mass M34 Together, these inclusive jet and dijet results will provide important new constraints on the magnitude and shape of the gluon polarization over the range 0.015 < x < 0.2.
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