Accessing the Sign and Magnitude of $\Delta$G via high $p_{T}$, $A_{LL}^{\pi^{\pm}}$ in Polarized p+p Collisions at PHENIX

TL;DR

This paper reports measurements of double-helicity asymmetries in charged pion production at high transverse momentum in polarized proton collisions, providing insights into the gluon polarization within protons.

Contribution

It presents new experimental data on $A_{LL}$ for $^{+}$ and $^{-}$ pions at high $p_T$, sensitive to the sign and magnitude of gluon polarization, aiding future global analyses.

Findings

Charged pion asymmetries are sensitive to gluon polarization.

Results show differences in $A_{LL}$ among pion species at high $p_T$.

Data supports constraints on the sign of $$G in proton spin structure.

Abstract

The double-helicity asymmetries ($A_{LL}$) of $\pi^{+}$ and $\pi^{-}$ production in polarized proton proton collisions are specially interesting probes of the gluon's polarization. Relative differences among $A_{LL}$ of positive, neutral, and negative pions at high transverse momentum are sensitive to the sign and of magnitude of $\Delta$G. Quark-gluon (qg) scattering starts to dominate mid-rapidity pion production at RHIC at transverse momenta above 5GeV/c. In this kinematic region the favored and unfavored fragmentation functions for each pion species are sensitive to both the gluon and the quark distributions, with different flavors having different weights for each pion species. Charged pion asymmetry measurements will be an important component in future global analyses, aiming to determine the gluon polarization over a wide range in x, the most recent results using polarized longitudinal data at $\sqrt{s}=$200GeV, are presented.