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Dielectron Mass Spectra from Au+Au Collisions at $\sqrt{s_{\rm NN}}$ = 200 GeV

Abstract : We report the STAR measurements of dielectron ($e^+e^-$) production at midrapidity ($|y_{ee}|<$1) in Au+Au collisions at $\sqrt{s_{\rm NN}}$ = 200 GeV. The measurements are evaluated in different invariant mass regions with a focus on 0.30-0.76 ($\rho$-like), 0.76-0.80 ($\omega$-like), and 0.98-1.05 ($\phi$-like) GeV/$c^{2}$. The spectrum in the $\omega$-like and $\phi$-like regions can be well described by the hadronic cocktail simulation. In the $\rho$-like region, however, the vacuum $\rho$ spectral function cannot describe the shape of the $\rho$-like dielectron excess. In this range, an enhancement of 1.77$\pm$0.11(stat.)$\pm$0.24(sys.)$\pm$0.34(cocktail) is determined with respect to the hadronic cocktail simulation that excludes the $\rho$ meson. The enhancement shows no significant dependence on the collision centrality in 0-80% and on the dielectron transverse momentum ($p_{\rm T}$) in $p_{\rm T}<$2 GeV/$c$. Theoretical models with in-medium broadened $\rho$ contributions can provide a consistent description of the dilepton mass spectra for the measurement presented here and the earlier data at the Super Proton Synchrotron energies.
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http://hal.in2p3.fr/in2p3-00926059
Contributor : Sylvie Flores <>
Submitted on : Thursday, January 9, 2014 - 9:41:08 AM
Last modification on : Thursday, February 7, 2019 - 3:18:45 PM

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L. Adamczyk, W. Borowski, S. Kabana. Dielectron Mass Spectra from Au+Au Collisions at $\sqrt{s_{\rm NN}}$ = 200 GeV. Physical Review Letters, American Physical Society, 2013, 113, pp.022301. ⟨10.1103/PhysRevLett.113.022301⟩. ⟨in2p3-00926059⟩

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