Photons from strange-quark annihilation in a quark-gluon plasma.

Given the present knowledge about strong interaction, one has to assume that in collisions of heavy nuclei with sufficiently high kinetic energy, a high-energy-density region can be formed in which the hadrons dissolve into their constituents, i.e., into quark-gluon Several estimates2 lead to 0.5-2 ~ e ~ / f m ~ or the critical energy density. The quark-gluon plasma represents a new physical phase and its physics can often approximately be described by methods of perturbation theory.'r2 In order to verify this hypothesis of the existence of a new phase of matter one has to consider all processes, which could give a hint to the existence of the plasma. In this paper we consider certain processes leading to high-energy photons. These photons will, in general, leave the interaction region without further interactions. Numerous photon production processes which have little to do with the plasma state will normally dominate the photon spectra. However, one can perform an in-depth study of various contributions3 and it is conceivable that even a small effect may become visible in certain kinematic domains, such as small X , large P I , once a correlation with strangeness overabundance is established. In the plasma phase, numerous pairs of strange and antistrange quarks are created by gluons,4 which occasionally annihilate again. One possible, though rare, annihilation process is to create a gluon and a photon. Naively one expects that these photons possess a relatively high energy. The energy of photons is given by E,=Es +E,-E, and it should be recorded that strange quarks and antiquarks carry their rest mass, in addition to the thermal kinetic energy, into the reaction while emission of low-energy gluons is stimulated by the existence of numerous low-energy gluons in plasma. In this paper we calculate the spectrum of the photons which are produced in such processes ( s S + y g ) quantitatively to first order in the perturbative approach. 11. TRANSITION PROBABILITY: sF4yg