Dilepton production in p+p, Cu+Cu and Au+Au collisions at 200 AGeV

TL;DR

This study models dilepton production in various high-energy collisions, revealing discrepancies with experimental data and highlighting the significance of correlated decay backgrounds, yet still falling short of observed spectra.

Contribution

It extends the statistical hadronization model by including transport calculations for uncorrelated dileptons from D meson decays in heavy-ion collisions.

Findings

Standard models match p+p data but fail in heavy-ion collisions.

Correlated decay backgrounds are significant in low-mass regions.

Calculated spectra are still below experimental measurements.

Abstract

We study dilepton production in proton-proton, Cu+Cu as well as in Au+Au collisions at the center-of-mass energy 200 GeV per participating nucleon pair within an extended statistical hadronization model. In extension to earlier studies we incorporate transport calculations for an estimate of uncorrelated e+e- -pairs from semileptonic D meson decays. While the invariant mass spectrum of dielectrons is well understood in the p+p collisions, severe discrepancies among different model scenarios based on hadronic degrees of freedom and recent data from the PHENIX Collaboration are found in heavy-ion collisions in the low mass region from 0.15 to 0.6 GeV as well as in the intermediate mass regime from 1.1 to 3 GeV when employing the standard dilepton sources. We investigate, furthermore, the background from correlated dileptons that are not emitted as a pair from a parent hadron but emerge from semileptonic decays of two correlated daughter hadrons. Our calculations suggest a sizeable contribution of such sources in central heavy-ion collisions in the low mass region. However, even the upper limits of our calculations are found to be far below the dilepton mass spectra of the PHENIX Collaboration.