Beam Energy and Centrality Dependence of Direct-Photon Emission from Ultrarelativistic Heavy-Ion Collisions

(PHENIX Collaboration)

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

The PHENIX collaboration presents first measurements of low-momentum (0.4<pT<3 GeV/c) direct-photon yields from Au+Au collisions at sNN=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 sNN=200. Analyzing the photon yield as a function of the experimental observable dNch/dη reveals that the low-momentum (>1 GeV/c) direct-photon yield dNγdir/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.

Original languageEnglish
Article number022301
JournalPhysical Review Letters
Volume123
Issue number2
DOIs
Publication statusPublished - 2019 Jul 10

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ionic collisions
photons
scaling
collisions
energy
heavy ions
momentum

ASJC Scopus subject areas

  • Physics and Astronomy(all)

Cite this

Beam Energy and Centrality Dependence of Direct-Photon Emission from Ultrarelativistic Heavy-Ion Collisions. / (PHENIX Collaboration).

In: Physical Review Letters, Vol. 123, No. 2, 022301, 10.07.2019.

Research output: Contribution to journalArticle

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abstract = "The PHENIX collaboration presents first measurements of low-momentum (0.41 GeV/c) direct-photon yield dNγdir/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.",
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AU - Akiba, Y.

AU - Akimoto, R.

AU - Al-Bataineh, H.

AU - Alexander, J.

AU - Alfred, M.

AU - Al-Jamel, A.

AU - Al-Ta'Ani, H.

AU - Angerami, A.

AU - Aoki, K.

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AU - Barish, K. N.

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AU - Belmont, R.

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AU - Bhom, J. H.

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