Electroproduction of ψ′ and polarized gluon distribution in a proton

In order to get information about the polarized gluon distribution in a proton, we studied the electroproduction of ψ′ in polarized electron and polarized proton collisions in the framework of the NRQCD factorization approach. The value of the cross section dΔσ/dpT2 for color-octet mechanism is about 5 times larger than that for color-singlet one, and it might be another test of the color-octet model if the polarized gluon distribution Δg(x) is well known. Furthermore, we found that this reaction is quite effective for testing the model of gluon polarization by measuring the double spin asymmetry ALL for the initial electron and proton. Though the shape of pT2 distribution of ALL is quite similar for the production mechanism with color-octet and color-singlet, we can see a big difference in ALL among various models of the polarized gluon distribution function Δg(x).