engleski

Energy dependence of acceptance-corrected dielectron excess mass spectrum at mid-rapidity in Au+Au collisions at snn=19.6 and 200 GeV

The acceptance-corrected dielectron excess mass spectra, where the known hadronic sources have been subtracted from the inclusive dielectron mass spectra, are reported for the first time at mid-rapidity |yee|<1 in minimum-bias Au+Au collisions at View the MathML source and 200 GeV. The excess mass spectra are consistently described by a model calculation with a broadened ρ spectral function for Mee<1.1 GeV/c2 . The integrated dielectron excess yield at View the MathML source for 0.4<Mee<0.75 GeV/c2 , normalized to the charged particle multiplicity at mid-rapidity, has a value similar to that in In+In collisions at View the MathML source . For View the MathML source , the normalized excess yield in central collisions is higher than that at View the MathML source and increases from peripheral to central collisions. These measurements indicate that the lifetime of the hot, dense medium created in central Au+Au collisions at View the MathML source is longer than those in peripheral collisions and at lower energies.

STAR ; dependence

STAR Collaboration.