Conical flow induced by quenched QCD jets

Abstract

Quenching is a recently discovered phenomenon in which QCD jets created in heavy ion collisions deposit a large fraction or even all their energy and momentum into the produced matter . At RHIC and higher energies, where that matter is a strongly coupled Quark-Gluon Plasma (sQGP) with very small viscosity, we suggest that this energy/momentum propagate as a collective excitation or "conical flow". Similar hydrodynamical phenomena are well known, e.g. the so called sonic booms from supersonic planes. We solve the linearized relativistic hydrodynamic equations to detail the flow picture. We argue that for RHIC collisions the direction of this flow should make a cone at a specific large angle with the jet, of about 70 o , and thus lead to peaks in particle correlations at the angle ∆φ = π ± 1.2 rad relative to the large-pt trigger. This angle happens to match perfectly the position of the maximum in the angular distribution of secondaries associated with the trigger recently seen by the STAR and PHENIX collaborations. We also discuss briefly possible alternative explanations and suggest some further tests to clarify the mechanism.

A comparative study of jet-quenching schemes

“…Phenomenological studies of hard-soft correlations indicate that the lost energy seems to excite collective density excitations in the medium [34]. However, alternate explanations in terms of Cherenkov radiation [35] or in-medium Sudakov effects in jet radiation [36] have not been ruled out.…”

Effect of jet quenching on hydrodynamical evolution of QGP

“…In a strongly coupled plasma with overdamped plasma oscillations, which seems to be the preferred interpretation of RHIC data [13,14], the wake field scenario should reduce to the hydrodynamic Mach cone picture. We here study the dynamical consequences of the latter, going beyond the discussion of linearized hydrodynamic equations in a static background offered in [1].We assume that just before hydrodynamics become applicable, a pair of high-p T partons is produced near the surface of the fireball. One of them moves outward and escapes, forming the trigger jet, while the other enters into the fireball along, say, the −x direction.…”

“…In a strongly coupled plasma with overdamped plasma oscillations, which seems to be the preferred interpretation of RHIC data [13,14], the wake field scenario should reduce to the hydrodynamic Mach cone picture. We here study the dynamical consequences of the latter, going beyond the discussion of linearized hydrodynamic equations in a static background offered in [1].…”

“…[1] that a Mach shock ("sonic boom") should develop, resulting in conical flow and preferred particle emission at a specific angle away from the direction of the fast parton which lost its energy. This Mach angle is sensitive to the medium's speed of sound c s and thus offers the possibility to measure one of its key properties.…”

“…One expects [1] azimuthally anisotropic particle emission, peaking at angles φ = π ± θ M relative to the trigger jet where θ M is the Mach angle. Using the standard Cooper-Frye prescription, we have computed the angular distribution of directly emitted pions at a freeze-out temperature T fo = 100 MeV [7].…”