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

Abstract

Fermilab Experiment 866 took single muon data from 800 GeV/c ({radical}s = 38.8 GeV) p-Cu and p-Be interactions in an attempt to extract the inclusive nuclear open charm/anti-charm (D/{bar D}) differential cross sections as a function of p{sub T}. The muons were decay products from semi-leptonic decays of open charm mesons as well as decays from lighter non-charmed mesons ({pi}'s and K's). 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 p{sub T} range of approximately 2 to 7 GeV/c, center-of-mass rapidity, y{sub cm}, between 0 and 2, and x{sub F} between 0.2 and 0.8. Previous experimental results for p-p or p-A open charm production at comparable energy was limited to {radical}5 GeV/ Three functions describingmore » the shape of the open charm/anti-charm cross sections were fit to the data; an exponential, A{sub 1} exp (-B p{sub T}), and two polynomials, A{sub 2}/p{sub T}{sup 2} + {alpha}m{sub c}{sup 2}{sup n} and A{sub 2} (1-p{sub T}/p{sub beam}){sup m}/(p{sub T}{sup 2} + {alpha}m{sub c}{sup 2}){sup n}. The first polynomial was fit with the parameter n as a free parameter, and constant with three integer values, 4, 5 and 6. The second was fit with n held fixed at the constant integer values only. The best results were with the first polynomial with n around 6. All three parameterizations resulted in good fits. Extrapolation of the cross sections to small p{sub T} shows good agreement with previous experiments. The power {alpha} of the nuclear dependency A{sup {alpha}(P{sub T})} was calculated as a function of p{sub T}. The result indicates that {alpha} is transverse-momentum dependent, albeit within large errors.« less