Two-Spin Asymmetry for $\psi^{\prime}$ Photoproduction with Color-Octet Mechanism

TL;DR

This paper investigates the two-spin asymmetry in $psi^{\u2032}$ photoproduction at HERA energies, demonstrating its potential to test the color-octet mechanism within the NRQCD framework and constrain matrix elements.

Contribution

It introduces the use of two-spin asymmetry measurements in polarized $$ collisions to test the color-octet mechanism and constrain NRQCD matrix elements.

Findings

The reaction effectively tests the color-octet mechanism.

Two-spin asymmetry can severely constrain NRQCD matrix elements.

Process depends on polarized gluon distribution $ g(x)$.

Abstract

We studied the photoproduction of $\psi^{\prime}$ in the forward regions in polarized $\gamma p$ collisions at relevant HERA energies. We found that this reaction is very effective to test the color-octet mechanism which is based on the NRQCD factorization formalism. Furthermore we found that the value of the NRQCD matrix elements can be severely constrained by measuring the two-spin asymmetry, though the process depends on the polarized gluon distribution $\Delta g(x)$.