Measurement of Direct-Photon Cross Section and Double-Helicity Asymmetry at s =510 GeV in p → + p → Collisions

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Abstract

We present measurements of the cross section and double-helicity asymmetry ALL of direct-photon production in p→+p→ collisions at s=510 GeV. The measurements have been performed at midrapidity (|η|<0.25) with the PHENIX detector at the Relativistic Heavy Ion Collider. At relativistic energies, direct photons are dominantly produced from the initial quark-gluon hard scattering and do not interact via the strong force at leading order. Therefore, at s=510 GeV, where leading-order-effects dominate, these measurements provide clean and direct access to the gluon helicity in the polarized proton in the gluon-momentum-fraction range 0.02<x<0.08, with direct sensitivity to the sign of the gluon contribution.

Original languageEnglish
Article number251901
Number of pages8
JournalPhysical review letters
Volume130
Issue number25
DOIs
StatePublished - 21 Jun 2023

All Science Journal Classification (ASJC) codes

  • General Physics and Astronomy

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