Measurement of the relative prompt production rate of chi(c2) and chi(c1) in pp collisions at sqrt(s) = 7 TeV

TL;DR

This paper reports a measurement of the ratio of production rates of chi(c2) and chi(c1) particles in proton-proton collisions at 7 TeV, using CMS data, and compares the results with theoretical models.

Contribution

It provides the first detailed measurement of the chi(c2) to chi(c1) production ratio at 7 TeV with photon conversion detection.

Findings

The ratio varies across different pt(J/psi) intervals.

Results are consistent with some theoretical predictions.

Provides data for refining quarkonium production models.

Abstract

A measurement is presented of the relative prompt production rate of chi(c2) and chi(c1) with 4.6 inverse femtobarns of data collected by the CMS experiment at the LHC in pp collisions at sqrt(s) = 7 TeV. The two states are measured via their radiative decays chi(c) to J/psi + gamma, with the photon converting into a dielectron pair for J/psi rapidity abs(y(J/psi)) < 1.0 and photon transverse momentum pt(gamma) > 0.5 GeV. The measurement is given for six intervals of pt(J/psi) between 7 and 25 GeV. The results are compared to theoretical predictions.