Measurements of dielectron production in <math><mrow><mi>Au</mi><mo>+</mo><mi>Au</mi></mrow></math> collisions at <math><mrow><msqrt><msub><mi>s</mi><mrow><mi>N</mi><mi>N</mi></mrow></msub></msqrt><mo>=</mo><mn>27</mn></mrow></math>, 39, and 62.4 GeV from the STAR experiment

Abdulhamid, M.I.; Aboona, B.E.; Adam, J.; Adamczyk, L.; Adams, J.R.; Aggarwal, I.; Aggarwal, M.M.; Ahammed, Z.; Anderson, D.M.; Aschenauer, E.C.

doi:10.1103/PhysRevC.107.L061901

Measurements of dielectron production in $Au + Au$ collisions at $\sqrt{s_{N N}} = 27$ , 39, and 62.4 GeV from the STAR experiment

STAR

Collaboration

Jun 1, 2023

7 pages

Published in:

Phys.Rev.C 107 (2023) 6, L061901

Published: Jun 1, 2023

DOI:

10.1103/PhysRevC.107.L061901 (publication)

Experiments:

BNL-RHIC-STAR

View in:

Nuclear Science References

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Abstract: (APS)

We report systematic measurements of dielectron (

e^{+} e^{-}

) invariant-mass

M_{e e}

spectra at midrapidity in

Au + Au

collisions at

\sqrt{s_{N N}}

= 27, 39, and 62.4 GeV taken with the STAR detector at the Relativistic Heavy Ion Collider. For all energies studied, a significant excess yield of dielectrons is observed in the low-mass region (

0.40 < M_{e e} < 0.75 MeV / c^{2}

) compared to hadronic cocktail simulations at freeze-out. Models that include an in-medium broadening of the

ρ

-meson spectral function consistently describe the observed excess. In addition, we report acceptance-corrected dielectron-excess spectra for

Au + Au

collisions at midrapidity (

| y_{e e} | <

1) in the 0–80% centrality bin for each collision energy. The integrated excess yields for

0.4 < M_{e e} < 0.75 GeV / c^{2}

, normalized by the charged particle multiplicity at midrapidity, are compared with previously published measurements for

Au + Au

at

\sqrt{s_{N N}}

= 19.6 and 200 GeV. Models that include an in-medium broadening of the

ρ

-meson spectral function consistently describe the observed excess. The normalized excess yields in the low-mass region show no significant collision energy dependence. The data, however, are consistent with model calculations that demonstrate a modest energy dependence.

dilepton: production
charged particle: multiplicity
heavy ion: scattering
broadening
STAR
spectral representation
energy dependence
freeze-out
experimental results
27: 39: 62.4 GeV-cms/nucleon

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