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

摘要

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