Hadroproduction of the Chi1 and Chi2 States of Charmonium in 800 GeV/c Proton-Silicon Interactions

TL;DR

This paper reports measurements of the production cross sections of Chi1 and Chi2 charmonium states in proton-silicon collisions at 38.8 GeV, providing experimental data that inform theoretical models of quarkonium production.

Contribution

First measurement of Chi1 and Chi2 hadroproduction cross sections in proton-silicon interactions at this energy, with detailed comparison to theoretical predictions.

Findings

Chi1 cross section: 263+-69(stat)+-32(syst) nb

Chi2 cross section: 498+-143(stat)+-67(syst) nb

Chi1/Chi2 ratio: 0.53+-0.20(stat)+-0.07(syst)

Abstract

The cross sections for the hadroproduction of the Chi1 and Chi2 states of charmonium in proton-silicon collisions at sqrt{s}=38.8 GeV have been measured in Fermilab fixed target Experiment 771. The Chi states were observed via their radiative decay to J/psi+gamma, where the photon converted to e+e- in the material of the spectrometer. The measured values for the Chi1 and Chi2 cross sections for x_F>0 are 263+-69(stat)+-32(syst) and 498+-143(stat)+-67(syst) nb per nucleon respectively. The resulting sigma(Chi1}/sigma(Chi2) ratio of 0.53+-0.20(stat)+-0.07(syst), although somewhat larger than most theoretical expectations, can be accomodated by the latest theoretical estimates.