Diagnosing quark matter by measuring the total entropy and the photon or dilepton emission rates

Abstract

The rates of thermal emission of photons and lepton pairs from quark matter formed in ultrarelativistic nuclear collisions are related to the conserved total entropy of the quark matter. The transient existence of quark matter can be diagnosed by measuring the entropy separately from particle multiplicities and comparing the predicted and observed rates. The thermal soft-multiple-scattering rates are compared with the direct hard-single-scattering rates. Transverse-momentum effects, the background due to DD\ifmmode\bar\else\textasciimacron\fi{}\ensuremath{\rightarrow}\ensuremath{\mu}\ensuremath{\mu}\ifmmode\bar\else\textasciimacron\fi{}X decays, and fluctuations are discussed.