J/psi polarization at hadron colliders in nonrelativistic QCD

TL;DR

This paper provides a comprehensive next-to-leading order QCD calculation of J/psi polarization at hadron colliders, offering insights into the polarization puzzle by analyzing contributions from various Fock states.

Contribution

It introduces a full NLO computation including all key Fock states, offering a potential resolution to the longstanding J/psi polarization puzzle.

Findings

The $^3P_J[8]$ channel contributes positively to longitudinal polarization.

The transverse polarization cancels between $^3S_1[8]$ and $^3P_J[8]$ channels.

Predictions for LHC J/psi polarization are provided.

Abstract

With nonrelativistic QCD factorization, we present a full next-to-leading order computation of the polarization observable for $J/psi$ production at hadron colliders including all important Fock states, i.e. $^3S_1[1,8]$, $^1S_0[8]$, and $^3P_J[8]$. We find the $^3P_J[8]$ channel contributes a positive longitudinal component and a negative transverse component. So the $J/psi$ polarization puzzle may be understood as the transverse components canceling between $^3S_1[8]$ and $^3P_J[8]$ channels, which results in mainly the unpolarized (even slightly longitudinally polarized) $J/psi$. This may give a possible solution to the long-standing $J/psi$ polarization puzzle. Predictions for $J/psi$ polarization at the LHC are also presented.