A study of D<sup>0</sup> production from 500 GeV π<sup>-</sup>--nucleon interactions

Abstract

Fermilab experiment E791 took data during six months in 1991 using a 500 GeV {pi}{sup -} beam on platinum and diamond targets for the purpose of studying the production and decay of particles containing a charm quark. In this dissertation, results are presented on the production of the D{sup 0} and {anti D}{sup 0} mesons using fully reconstructed D{sup 0}{yields}K{pi} and D{sup 0}{yields}K{pi}{pi}{pi} decays. Specifically, the total forward production cross section is measured as well as differential cross sections as a function of the scaled longitudinal momentum, Feynman-x (x{sub F}), and the transverse momentum squared (p{sub T}{sup 2}). The results are compared to theoretical predictions from a next-to-leading order (NLO) calculation and from a leading order Monte Carlo event generator, PYTHIA/JETSET, which uses parton showers to account for higher-order terms. The comparison is made to both the c quark predictions and the predictions for D mesons using the Peterson fragmentation scheme for the NLO calculation and the Lund string fragmentation for the PYTHIA/JETSET prediction. The data are also compared to previous measurements by other experiments which used a {pi}{sup -} beam. Assuming an A{sup 1} dependence, the total forward cross section for the sum of D{sup 0} and {anti D}{supmore » 0} production is measured to be {sigma}(D{sup 0}/{anti D}{sup 0}; x{sub F}>0)=15.4{sup +1.8}{sub -2.3} {micro}barns/nucleon, in good agreement with other experiments and the NLO prediction. The differential cross sections agree best with the NLO c quark prediction and the PYTHIA/JETSET D{sup 0} meson prediction. Several functions are fit to the differential cross sections. From the fits to the x{sub F} distribution we find the x{sub F} distribution peaks at x{sub F}=0.013{+-}0.004, significantly above zero as predicted by the harder pion parton distribution function. Fitting the shape of the x{sub F} distribution to (1-x{sub F}){sup n}, while not a good fit, gives n=4.61{+-}0.19 for the rang e0.05<x{sub F}<0.50. The p{sub T}{sup 2} shape is acceptably fit with the function e{sup b'p{sub T}} with b'=2.41{+-}0.03 over the range 1(GeV/c){sup 2}<p{sub T}{sup 2}<18(GeV/c){sup 2}.« less