"Figure 2" of "Measurement of Direct-Photon Cross Section and Double-Helicity Asymmetry at $\sqrt{s}=510$ GeV in $\vec{p}+\vec{p}$ Collisions"

Metadata

Published
2022-01-01
DOI
  • 10.17182/hepdata.129088.v1/t2
Publisher
HEPData
Creator Name (e-Rad)
  • PHENIX Collaboration

Description

BNL-RHIC. We present the measurement of the cross section and double helicity asymmetry $A_{LL}$ of direct photon production in $\vec{p}+\vec{p}$ collisions at $\sqrt{s}$ = 510 GeV. The measurement has been performed at midrapidity ($|\eta| <$ 0.25) with the PHENIX detector at the Relativistic Heavy Ion Collider. Direct photons are dominantly produced by the quark-gluon scattering at relativistic energies. Since direct photons are produced from the initial partonic hard scattering and do not interact via the strong force, this measurement provides a clean and direct access to the gluons in the polarized proton in the gluon momentum fraction range 0.02 $< x <$ 0.08.

Double helicity asymmetry $A_{LL}$ $vs$ $p_{T}$ for isolated direct-photon production in polarized $\vec{p}+\vec{p}$ collisions at $\sqrt{s}=510$ GeV at midrapidity. Not shown are $3.9 \times 10^{-4}$ shift uncertainty from relative luminosity and 6.6% scale uncertainty from polarization.

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