The remaining parts for the long-standing J/psi polarization puzzle

TL;DR

This paper calculates the polarization parameters of J/psi hadroproduction at NLO using NRQCD, including feeddown effects, and successfully fits the experimental data from the LHC.

Contribution

First NLO calculation of J/psi polarization parameters in helicity frame within NRQCD including feeddown contributions, achieving good agreement with LHC measurements.

Findings

Theoretical predictions match LHC polarization data.

Feeddown from $J$ and $(2S)$ decays are significant.

NLO calculations improve understanding of J/psi polarization.

Abstract

Based on the non-relativistic quantum chromodynamics factorization formalism, the polarization parameters $\lambda_{\theta\phi}$ and $\lambda_{\phi}$ of $J/\psi$ hadroproduction are analyzed in helicity frame and calculated at QCD next-to-leading order for the first time. For prompt $J/\psi$ production, we take into account the feeddown contributions from $\chi_{cJ}$ and $\psi(2S)$ decays. The theoretical predictions for the polarization parameters $\lambda_{\theta\phi}$ and $\lambda_{\phi}$ of $J/\psi$ are presented. With the theoretical results we have done the fit to the experimental measurements on yield and polarization for $J/\psi$ hadroproduction simultaneously, and found that the results are coincide with the experimental measurements at the LHC quite well.