Paper Page - Longitudinal double-spin asymmetry for inclusive jet and dijet production at 200 GeV (2015 dataset)

Title: Longitudinal double-spin asymmetry for inclusive jet and dijet production in polarized proton collisions at √s = 200 GeV

PAs: Nick Lukow, Ernst Sichtermann, Bernd Surrow, Maria Żurek 

Target Journal: Physical Review D Letters 

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Analysis Code: https://www.star.bnl.gov/cgi-bin/protected/viewvc.cgi/cvsroot/offline/paper/psn0756/

Abstract:
We  report  high-precision  measurements  of  the  longitudinal  double-spin  asymmetries, ALL, for midrapidity inclusive jet and dijet production in polarized pp collisions at a center-of-mass energy of √s = 200 GeV.  The new inclusive jet data are sensitive to the gluon helicity distribution ∆g(x,Q2) for gluon  momentum  fractions  in  the  range  from x≃0.05  to x≃0.5,  while  the  new  dijet  data provide further constraints on the x-dependence of ∆g(x,Q2). The results are in good agreement with previous measurements at √s = 200 GeV and with recent theoretical evaluations of prior world data.  Our new results have better precision and thus strengthen the evidence that ∆g(x,Q2) is positive for x>0.05. 

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Conclusions:
In summary, we have presented ALL for midrapidity inclusive jet and dijet production based on data recorded by the STAR collaboration during RHIC operations with polarized proton beams at √s=200 GeV in 2015. The data provide sensitivity to the polarized gluon distribution ∆g(x,Q2) for gluon momentum fractions 0.05≲x≲0.5. Our new results are consistent with and have better precision than our previous data at √s=200 GeV. The results provide further evidence that ∆g(x,Q2) is positive for x>0.05.