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

Abstract

We compute \frac{dσ}{dp_T} of the J/ψproduction 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/ψwe compute here includes the direct J/ψfrom the partonic fusion processes and the J/ψcoming from the radiative decays of χ_J's both in the color octet and singlet channel. The high p_T J/ψproduction cross section is computed within the PHENIX detector acceptance ranges: -0.35 < η< 0.35 and 1.2 < \|η| < 2.4, the central electron and forward muon arms. It is found that the color octet contribution to J/ψproduction 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/ψmeasurements. 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/ψproduction at RHIC in the next run with better statistics will allow us to determine the validity of the color octet model of J/ψproduction at RHIC energies. This is very important because it is necessary to know the exact mechanism for J/ψproduction in pp collisions at RHIC if one is to make predictions of J/ψsuppression 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.

16 pages latex, 6 figures