Physics and Astronomy
Journal or Book Title
The PHENIX collaboration presents first measurements of low-momentum (0.41\,GeV/c) direct-photon yield dNdirγ/dη is a smooth function of dNch/dη and can be well described as proportional to (dNch/dη)α with α≈1.25. This scaling behavior holds for a wide range of beam energies at the Relativistic Heavy Ion Collider and the Large Hadron Collider, for centrality selected samples, as well as for different, A+A collision systems. At a given beam energy the scaling also holds for high pT (>5\,GeV/c) but when results from different collision energies are compared, an additional sNN−−−√-dependent multiplicative factor is needed to describe the integrated-direct-photon yield.
Adare, A.; Apadula, Nicole J.; Belikov, Sergey; Constantin, Paul; Ding, Lei; Dion, Alan; Grau, Nathan C.; Hill, John C.; Hotvedt, Nels J.; Kempel, Todd; Lajoie, John G.; Lebedev, Alexandre; Lee, S. H.; Ogilvie, Craig; Patel, Milap R.; Pei, H.; Rak, Jan; Rinn, Timothy T.; Rosati, Marzia; Runchey, Jonathan C.; Semenov, Alexey Yu.; Sen, Abhisek; Shimomura, M.; Silva, C. L.; Skutnik, S.; Vale, Carla; Wei, Feng; et al.; and PHENIX Collaboration, "Beam-energy and centrality dependence of direct-photon emission from ultra-relativistic heavy-ion collisions" (2019). Physics and Astronomy Publications. 511.