Nonprompt direct-photon production in <math><mrow><mtext>Au</mtext><mo>+</mo><mtext>Au</mtext></mrow></math> collisions at <math><mrow><msqrt><msub><mi>s</mi><mrow><mi>N</mi><mi>N</mi></mrow></msub></msqrt><mo>=</mo><mn>200</mn></mrow></math> GeV

Abdulameer, N.J.; Acharya, U.A.; Adare, A.; Aidala, C.; Ajitanand, N.N.; Akiba, Y.; Alfred, M.; Apadula, N.; Asano, H.; Azmoun, B.

doi:10.1103/PhysRevC.109.044912

Nonprompt direct-photon production in $Au + Au$ collisions at $\sqrt{s_{N N}} = 200$ GeV

PHENIX

Collaboration

Mar 31, 2022

26 pages

Published in:

Phys.Rev.C 109 (2024) 4, 044912

Published: Apr 18, 2024

e-Print:

2203.17187 [nucl-ex]

DOI:

10.1103/PhysRevC.109.044912 (publication)

Experiments:

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Abstract: (APS)

The measurement of the direct-photon spectrum from

Au + Au

collisions at

\sqrt{s_{_{N N}}} = 200

GeV is presented by the PHENIX Collaboration using the external-photon-conversion technique for 0%–93% central collisions in a transverse-momentum (

p_{T}

) range of 0.8–10

GeV / c

. An excess of direct photons, above prompt-photon production from hard-scattering processes, is observed for

p_{T} < 6 GeV / c

. Nonprompt direct photons are measured by subtracting the prompt component, which is estimated as

N_{coll}

-scaled direct photons from

p + p

collisions at 200 GeV, from the direct-photon spectrum. Results are obtained for

0.8 < p_{T} < 6.0 GeV / c

and suggest that the spectrum has an increasing inverse slope from

\approx 0.2

to 0.4

GeV / c

with increasing

p_{T}

, which indicates a possible sensitivity of the measurement to photons from earlier stages of the evolution of the collision. In addition, like the direct-photon production, the

p_{T}

-integrated nonprompt direct-photon yields also follow a power-law scaling behavior as a function of collision-system size. The exponent,

α

, for the nonprompt component is found to be consistent with 1.1 with no apparent

p_{T}

dependence.

Note:

336 authors from 71 institutions, 26 pages, 30 figures, 4 tabels, 2014 data. v2 is version accepted for publication in Physical Review C. Plain text data tables for the points plotted in figures for this and previous PHENIX publications are (or will be) publicly available at http://www.phenix.bnl.gov/papers.html

photon: direct production
PHENIX
transverse momentum
hard scattering
impact parameter
experimental results
200 GeV-cms/nucleon

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Nonprompt direct-photon production in Au+Au collisions at sNN=200 GeV

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Nonprompt direct-photon production in $Au + Au$ collisions at $\sqrt{s_{N N}} = 200$ GeV