Finding The Charm In 800 GeV/c p-Cu and p-Be Single Muon Spectra

TL;DR

This paper reports on measurements of single muon spectra from 800 GeV/c proton interactions with copper and beryllium, aiming to extract open charm production cross sections and study nuclear dependence across various transverse momenta.

Contribution

It provides the first detailed analysis of open charm cross sections as a function of transverse momentum in high-energy proton-nucleus collisions, including nuclear dependence.

Findings

Open charm cross sections measured from 2 to 7 GeV/c in transverse momentum.

Good agreement with previous experiments when extrapolated to small p_T.

Nuclear dependence parameter alpha varies with transverse momentum.

Abstract

Fermilab Experiment 866 took single muon data from 800 GeV/c (sqrt{s}=38.8 GeV) p-Cu and p-Be interactions in an attempt to extract the inclusive nuclear open charm/anti-charm differential cross sections as a function of transverse momentum. The muons were decay products from semi-leptonic decays of open charm mesons as well as decays from lighter non-charmed mesons (pions and kaons). Data were taken simultaneously from two interaction regions; one of two thin nuclear targets and a copper beam dump 92 inches downstream. The open decay length for hadrons produced in the targets increased the contribution to the muon spectrum from light hadron decays, relative to those from the dump. Production cross sections for light hadrons from previous experiments were used in conjunction with parameterized open charm cross sections to produce total Monte Carlo single muon spectra that were subsequently fit to the data. The sensitivity of this measurement covered an open charm hadron transverse momentum range of approximately 2 to 7 GeV/c, center-of-mass rapidity, y, between 0 and 2, and Feynman-x between 0.2 and 0.8. Extrapolation of the cross sections to small transverse momentum shows good agreement with previous experiments. The power alpha of the nuclear dependency A^{alpha(p_T)} was calculated as a function of transverse momentum. The result indicates that alpha is transverse-momentum dependent, albeit within large errors.