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Adare, A.*; 長谷川 勝一; 今井 憲一; 永宮 正治*; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他666名*
Physical Review Letters, 123(2), p.022301_1 - 022301_10, 2019/07
被引用回数:36 パーセンタイル:86.23(Physics, Multidisciplinary)The PHENIX collaboration presents first measurements of low-momentum (0.4 3 GeV/
) direct-photon yields from Au
Au collisions at
= 39 and 62.4 GeV. For both beam energies the direct-photon yields are substantially enhanced with respect to expectations from prompt processes, similar to the yields observed in Au
Au collisions at
= 200. Analyzing the photon yield as a function of the experimental observable
reveals that the low-momentum (
1 GeV/
) direct-photon yield
is a smooth function of
and can be well described as proportional to
with
1.25. This new scaling behavior holds for a wide range of beam energies at the Relativistic Heavy Ion Collider and Large Hadron Collider, for centrality selected samples, as well as for different,
collision systems. At a given beam energy the scaling also holds for high
(
5 GeV/
) but when results from different collision energies are compared, an additional
-dependent multiplicative factor is needed to describe the integrated-direct-photon yield.