χc production in modified NRQCD

Abstract

In a previous paper, we had modified Non-Relativistic QCD as it applies to quarkonium production by taking into account the effect of perturbative soft-gluon emission from the colour-octet quarkonium states. We tested the model by fitting the unknown non-perturbative parameter in the model from Tevatron data and using that to make parameter-free predictions for J/ψ and ψ′ production at the LHC. In this paper, we study χc production: we fit as before the unknown matrix-element using data from Tevatron. We, then, extend the results of the previous paper for J/ψ production by calculating the effect of χc feed-down to the J/ψ cross-section, which, by comparing with CMS results at s= 13 TeV, we demonstrate to be small. We have also computed χc1 and χc2 at s=7 TeV and find excellent agreement with data from the ATLAS experiment.