Soft interactions in jet quenching

Abstract

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. 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, the ocasional hard collisions produce features characteristic of a Lèvy flight in the q 2 ⊥ plane perpendicular to the jet axis. We suggest one-and two-particle q ⊥ correlations as interesting experimental probes.

On the analytic structure of scalar glueball operators at the Born level

“…The sector of the strong nuclear force contains quarks and gluons, which, however, are not observed directly in experiments. Searches for partial electric charges (see, for example, [1][2][3][4]) have all been negative and also gluons have not been observed [5]. This phenomenon is known as confinement and many scenarios trying to explain the underlying mechanism exist; for summaries see, for instance, [6,7].…”