Low-momentum direct-photon measurement in Cu + Cu collisions at sNN =200 GeV

Summary, in English

We measured direct photons for pT<5GeV/c in minimum bias and 0%–40% most-central events at midrapidity for Cu+Cu collisions at √sNN=200GeV. The e+e− contribution from quasireal direct virtual photons has been determined as an excess over the known hadronic contributions in the e+e− mass distribution. A clear enhancement of photons over the binary scaled p+p fit is observed for pT<4GeV/c in Cu+Cu data. The pT spectra are consistent with the Au+Au data covering a similar number of participants. The inverse slopes of the exponential fits to the excess after subtraction of the p+p baseline are 285±53(stat)±57(syst)MeV/c and 333±72(stat)±45(syst)MeV/c for minimum bias and 0%–40% most-central events, respectively. The rapidity density, dN/dy, of photons demonstrates the same power law as a function of dNch/dη observed in Au+Au at the same collision energy.

• Author: A. Adare; Hans-Åke Gustafsson; Eva Haslum; Anders Oskarsson; Sarah Rosendahl; David Silvermyr; Evert Stenlund; L. Zou
• Department/s: Particle and nuclear physics
• Publishing year: 2018
• Language: English
• Publication/Series: Physical Review C
• Volume: 98
• Issue: 5
• Links: http://dx.doi.org/10.1103/PhysRevC.98.054902
• Document type: Journal article
• Publisher: American Physical Society
• Topic: Subatomic Physics
• Status: Published
• ISBN/ISSN/Other: ISSN: 2469-9985