Polarization and cross section of midrapidity J/$\psi$ production in proton-proton collisions at $\sqrt{s}=510$ GeV

TL;DR

This study measures the polarization and cross section of J/ψ production in proton-proton collisions at 510 GeV, finding no significant polarization at midrapidity and a logarithmic energy dependence of the cross section.

Contribution

It provides the first detailed polarization analysis at midrapidity at 510 GeV and compares the cross section dependence on collision energy with world data.

Findings

No sizable polarization observed at midrapidity.

The cross section shows a logarithmic dependence on collision energy.

Results are consistent with previous measurements at 200 GeV.

Abstract

The PHENIX experiment has measured the spin alignment for inclusive $J/\psi\rightarrow e^{+}e^{-}$ decays in $p$+$p$ collisions at $\sqrt{s}=510$ GeV at midrapidity. The angular distributions have been measured in three different polarization frames, and the three decay angular coefficients have been extracted in a full two-dimensional analysis. Previously, PHENIX saw large longitudinal net polarization at forward rapidity at the same collision energy. This analysis at midrapidity, complementary to the previous PHENIX results, sees no sizable polarization in the measured transverse momentum range of $0.0<p_T<10.0$ GeV/$c$. The results are consistent with a previous one-dimensional analysis at midrapidity at $\sqrt{s}=200$ GeV. The transverse-momentum-dependent cross section for midrapidity $J/\psi$ production has additionally been measured, and after comparison to world data we find a simple logarithmic dependence of the cross section on $\sqrt{s}$.