Eur. Phys. J. C (2009) 61: 905-913
https://doi.org/10.1140/epjc/s10052-008-0851-8

Regular Article - Theoretical Physics

Suppression of forward dilepton production from an anisotropic quark–gluon plasma

¹ Helmholtz Research School and Otto Stern School, Goethe-Universität Frankfurt am Main, Ruth-Moufang-Str. 1, 60438, Frankfurt am Main, Germany
² Institute für Theoretische Physik and Frankfurt Institute for Advanced Studies, Goethe-Universität Frankfurt am Main, Max-von-Laue-Straße 1, 60438, Frankfurt am Main, Germany
³ Department of Physics, Gettysburg College, Gettysburg, PA, 17325, USA

^* e-mail: guerrero@fias.uni-frankfurt.de

Received: 28 August 2008
Published online: 13 January 2009

Abstract

We calculate the rapidity dependence of leading-order medium dilepton yields resulting from a quark–gluon plasma which has a local time-dependent anisotropy in momentum space. We present a phenomenological model which includes the temporal evolution of the plasma anisotropy parameter, ξ, and the hard momentum scale, p _hard. Our model interpolates between a 1+1 dimensional collisionally broadened expansion at early times and a 1+1 dimensional ideal hydrodynamic expansion at late times. Using our model, we find that at LHC energies, forward high-energy medium dilepton production would be suppressed by a factor of up to 3 if one assumes an isotropization/thermalization time of 2 fm/c. Therefore, it may be possible to use forward dilepton yields to experimentally determine the time of the onset of locally isotropic hydrodynamic expansion of the quark–gluon plasma as produced in ultrarelativistic heavy-ion collisions.