Color Octet Contribution to High p_T J/\Psi Production in pp Collisions at \sqrt s = 500 and 200 GeV at RHIC

Abstract

We compute \frac{d\sigma}{dp_T} of the J/\psi production in pp collisions at RHIC at \sqrt s = 500 and 200 GeV by using both the color octet and singlet models in the framework of non-relativistic QCD. The J/\psi we compute here includes the direct J/\psi from the partonic fusion processes and the J/\psi coming from the radiative decays of \chi_J's both in the color octet and singlet channel. The high p_T J/\psi production cross section is computed within the PHENIX detector acceptance ranges: -0.35 < \eta < 0.35 and 1.2 < \|\eta| < 2.4, the central electron and forward muon arms. It is found that the color octet contribution to J/\psi production is dominant at RHIC energy in comparison to the color singlet contributions. We compare our results with the recent preliminary data obtained by PHENIX detector for the high p_T J/\psi measurements. While the color singlet model fails to explain the data completely the color octet model is in agreement with the single data point above 2 GeV transverse momentum. A measurement of J/\psi production at RHIC in the next run with better statistics will allow us to determine the validity of the color octet model of J/\psi production at RHIC energies. This is very important because it is necessary to know the exact mechanism for J/\psi production in pp collisions at RHIC if one is to make predictions of J/\psi suppression as a signature of quark-gluon plasma. These mechanisms also play an important role in determining the polarized spin structure function of the proton at RHIC.