Measuring Quark-Gluon-Plasma Thermalization Time with Dileptons
Abstract
We calculate the medium dilepton yield from a quark-gluon plasma which has a time-dependent local momentum-space anisotropy. A phenomenological model for the hard momentum scale, phard(tau), and plasma anisotropy parameter, xi(tau), is constructed which interpolates between free streaming behavior at early times (tau << tauiso) and ideal hydrodynamic behavior at late times (tau >> tauiso). We show that high-energy dilepton production is sensitive to the assumed plasma isotropization time, tauiso, and can therefore be used to experimentally determine the time of onset for hydrodynamic expansion of a quark-gluon plasma and the magnitude of expected early-time momentum-space anisotropies.
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