Delta G from high pT events at SMC and high pT analysis at COMPASS

TL;DR

This paper reports measurements of spin asymmetries in high transverse momentum events from SMC and COMPASS experiments, providing insights into the gluon polarization within the nucleon.

Contribution

It presents new measurements of gluon polarization using high pT hadron events in deep inelastic scattering at SMC and COMPASS, extending previous analyses.

Findings

Gluon polarization $\

Measured asymmetries are consistent with small or zero gluon polarization.

Results suggest limited contribution of gluons to nucleon spin within uncertainties.

Abstract

Measurements of the longitudinal spin cross section asymmetry for deep inelastic muon-nucleon interactions with two high transverse momentum hadrons ($p_T >$ 0.7 GeV) in the final state are presented for SMC data for polarized proton and deuteron and for data on polarized deuteron from COMPASS taken in 2002 and 2003. The muon asymmetries determined with a cut on $Q^2>$ 1 GeV$^2$ in SMC are: $A_p = 0.03 \pm 0.057\pm 0.01$ and $A_d = 0.070 \pm 0.076 \pm 0.010$, respectively. From these values a gluon polarization $\Delta G /G = -0.20\pm 0.28\pm 0.10$ was obtained at an average fraction of nucleon momentum carried by gluons $\eta = 0.07$. The measured asymmetry (with cut on $Q^2>$ 1 GeV$^2$) in COMPASS is $(A_d/D) = -0.015 \pm 0.08 \pm 0.013$ where D is depolarization factor and the gluon polarization $\Delta G /G = 0.06\pm 0.31\pm