Soft interactions in jet quenching

We study the collisional aspects of jet quenching in a high-energy nuclear collision, especially in the final state pion gas. The jet has a large energy, and acquires momentum transverse to its axis more effectively by multiple soft collisions than by few hard scatterings (as known from analogous systems such as J/ψ production at Hera). Such regime of large E and small momentum transfer corresponds to Regge kinematics and is characteristically dominated by the pomeron. From this insight we estimate the jet quenching parameter in the hadron medium (largely a pion gas) at the end of the collision, which is naturally small and increases with temperature in line with the gas density and compare it to the jet quenching parameter obtained within the quark–gluon plasma (QGP) phase in widely known perturbative approximations. The physics in the quark–gluon plasma/liquid phase is less obvious, and here we revisit a couple of simple estimates that suggest indeed that the pomeron-mediated interactions are very relevant and should be included in analysis of the jet quenching parameter. Finally, since the occasional hard collisions produce features characteristic of a Lèvy flight in the [Formula: see text] plane perpendicular to the jet axis, we suggest one- and two-particle q⊥correlations as interesting experimental probes sensitive to the nature (softness versus hardness) of the interactions of a jet inside the QGP.

Photon production in high energy nuclear collision of quark–gluon plasma

We extend to investigate photon production through annihilation with scattering (AWS), and Compton and annihilation processes from a stabilized high energy nuclear collision of quark–gluon plasma (QGP) incorporating finite value of quark mass obtained through a strong coupling value. The production rate is represented in the region of low and intermediate photon energy and it is observed to be a decreasing function with temperature. The calculation is extended to the case of photon spectra with the photon transverse momentum. The current observation shows little enhancement in both processes at the temperature T = 0.25 GeV and it is in conformity with the recent direct photon production of other works at temperature T = 0.30 GeV .