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

PHENIX has measured the electron–positron pair mass spectrum from 0 to 8 GeV/c28 GeV/c2 in p+pp+p collisions at s=200 GeV. The contributions from light meson decays to e+e−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−e+e− pairs in the mass region below ∼1 GeV/c2∼1 GeV/c2. The e+e−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) μb544±39(stat)±142(syst)±200(model) μb, which is consistent with QCD calculations and measurements of single leptons by PHENIX.