Extracting color octet NRQCD matrix elements from J/ψ production at the EIC

Daniël Boer,Pieter Taels,Cristian Pisano

doi:10.1103/physrevd.103.074012

Abstract

Recently unpolarized and polarized $J/\psi \,(\Upsilon)$ production at the Electron-Ion Collider (EIC) has been proposed as a new way to extract two poorly known color-octet NRQCD long-distance matrix elements: $\langle0\vert{\cal O}_{8}^{J/\psi}(^{1}S_{0})\vert0\rangle$ and $\langle0\vert{\cal O}_{8}^{J/\psi}(^{3}P_{0})\vert0\rangle$. The proposed method is based on a comparison to open heavy-quark pair production ideally performed at the same kinematics. In this paper we analyze this proposal in more detail and provide predictions for the EIC based on the available determinations of the color-octet matrix elements. We also propose two additional methods that do not require comparison to open heavy-quark pair production.

Highlights

AND FORMALISMSemi-inclusive J=ψ and Υ production in deep-inelastic lepton-proton scattering, i.e., ep → e0J=ψðΥÞX, where both the electron and the proton are unpolarized, is sensitive to unpolarized as well as linearly polarized transverse momentum dependent gluon distributions (TMDs) [1,2,3]
Predictions for the asymmetries are hampered by the dependence on two poorly known color-octet (CO) nonrelativistic QCD (NRQCD) long-distance matrix elements: h0jOJ8=ψ ð1S0Þj0i and h0jOJ8=ψ ð3P0Þj0i
In this paper we look into the determination of CO matrix elements in more detail, providing the general expressions and their current estimates, which can be of help in the study of these quantities at the Electron-Ion Collider (EIC)

Summary

INTRODUCTION

Semi-inclusive J=ψ and Υ production in deep-inelastic lepton-proton scattering, i.e., ep → e0J=ψðΥÞX, where both the electron and the proton are unpolarized, is sensitive to unpolarized as well as linearly polarized transverse momentum dependent gluon distributions (TMDs) [1,2,3] The latter lead to azimuthal cos 2φT modulations of the cross section differential in the transverse momentum of the J=ψ or Υ with respect to the lepton scattering plane [4,5,6]. [4] that ratios with the analogous expressions for unpolarized open heavy-quark pair production could be used to cancel out the gluon TMDs so as to determine the CO matrix elements experimentally.

M2Q ð15Þ

NUMERICAL RESULTS

GeV Not specified

SUMMARY AND CONCLUSIONS