Dilepton mass spectra in p + p collisions at sqrt(s) = 200 GeV and the contribution from open charm

Abstract

PHENIX has measured the electron-positron pair mass spectrum from 0 to 8 GeV / c2 in p + p collisions at sqrt(s) = 200 GeV. The contributions from light meson decays to e+ e- pairs have been determined based on measurements of hadron production cross sections by PHENIX. Within the systematic uncertainty of ∼20% they account for all e+ e- pairs in the mass region below ∼ 1 GeV / c2. The e+ e- pair yield remaining after subtracting these contributions is dominated by semileptonic decays of charmed hadrons correlated through flavor conservation. Using the spectral shape predicted by PYTHIA, we estimate the charm production cross section to be 544 ± 39 (stat) ± 142 (syst) ± 200 (model) μb, which is consistent with QCD calculations and measurements of single leptons by PHENIX. © 2008 Elsevier B.V. All rights reserved.