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

TL;DR

This paper reports measurements of electron-positron pair mass spectra in proton-proton collisions at 200 GeV, identifying contributions from light mesons and open charm decays, and estimating charm production cross section consistent with QCD.

Contribution

It provides the first detailed measurement of dilepton spectra in p+p collisions at this energy, including a novel estimate of open charm production cross section.

Findings

Light meson decays account for nearly all pairs below 1 GeV/c^2.

Remaining pairs are dominated by charm decays.

Estimated charm cross section aligns with QCD predictions.

Abstract

The PHENIX experiement has measured the electron-positron pair mass spectrum from 0 to 8 GeV/c^2 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. They account for nearly all e^+e^- pairs in the mass region below 1 GeV/c^2. 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) \mu b, which is consistent with QCD calculations and measurements of single leptons by PHENIX.