Abstract
The measurement of direct photons from Au+Au collisions at sNN=39 and 62.4 GeV in the transverse-momentum range 0.4<pT<3Gev/c is presented by the PHENIX collaboration at the BNLRelativistic Heavy Ion Collider. A significant direct-photon yield is observed in both collision systems. A universal scaling is observed when the direct-photon pT spectra for different center-of-mass energies and for different centrality selections at sNN=62.4 GeV is scaled with (dNch/dη)α for α=1.21±0.04. This scaling also holds true for direct-photon spectra from Au+Au collisions at sNN=200 GeV measured earlier by PHENIX, as well as the spectra from Pb+Pb at sNN=2760 GeV published by ALICE. The scaling power α seems to be independent of pT, center of mass energy, and collision centrality. The spectra from different collision energies have a similar shape up to pT of 2 Gev/c. The spectra have a local inverse slope Teff increasing with pT of 0.174±0.018Gev/c in the range 0.4<pT<1.3Gev/c and increasing to 0.289±0.024Gev/c for 0.9<pT<2.1Gev/c. The observed similarity of low-pT direct-photon production from sNN=39 to 2760 GeV suggests a common source of direct photons for the different collision energies and event centrality selections, and suggests a comparable space-time evolution of direct-photon emission.
| Original language | English |
|---|---|
| Article number | 024914 |
| Journal | Physical Review C |
| Volume | 107 |
| Issue number | 2 |
| DOIs | |
| State | Published - Feb 2023 |
Funding
We thank the staff of the Collider-Accelerator and Physics Departments at Brookhaven National Laboratory and the staff of the other PHENIX participating institutions for their vital contributions. We also thank J. F. Paquet for many fruitful discussions and sharing additional information. We acknowledge support from the Office of Nuclear Physics in the Office of Science of the Department of Energy, the National Science Foundation, Abilene Christian University Research Council, Research Foundation of SUNY, and Dean of the College of Arts and Sciences, Vanderbilt University (U.S.A), Ministry of Education, Culture, Sports, Science, and Technology and the Japan Society for the Promotion of Science (Japan), Conselho Nacional de Desenvolvimento Cient\u00EDfico e Tecnol\u00F3gico and Funda c\u00E3o de Amparo \u00E0 Pesquisa do Estado de S\u00E3o Paulo (Brazil), Natural Science Foundation of China (People's Republic of China), Croatian Science Foundation and Ministry of Science and Education (Croatia), Ministry of Education, Youth and Sports (Czech Republic), Centre National de la Recherche Scientifique, Commissariat \u00E0 l'\u00C9nergie Atomique, and Institut National de Physique Nucl\u00E9aire et de Physique des Particules (France), J. Bolyai Research Scholarship, EFOP, the New National Excellence Program (\u00DANKP), NKFIH, and OTKA (Hungary), Department of Atomic Energy and Department of Science and Technology (India), Israel Science Foundation (Israel), Basic Science Research and SRC(CENuM) Programs through NRF funded by the Ministry of Education and the Ministry of Science and ICT (Korea), Physics Department, Lahore University of Management Sciences (Pakistan), Ministry of Education and Science, Russian Academy of Sciences, Federal Agency of Atomic Energy (Russia), VR and Wallenberg Foundation (Sweden), University of Zambia, the Government of the Republic of Zambia (Zambia), the U.S. Civilian Research and Development Foundation for the Independent States of the Former Soviet Union, the Hungarian American Enterprise Scholarship Fund, the US-Hungarian Fulbright Foundation, and the US-Israel Binational Science Foundation.