The Sound Edge of the Quenching Jets

Abstract

When quenching jets deposit certain amount of energy and momentum into ambient matter, part of it propagates in the form of shocks/sounds. The "sound surface", separating disturbed and undisturbed parts of the fireball, makes what we call the sound edge of jets. In this work we semi-analytically study its shape, in various geometries. We further argue that since hadrons with in the kinematical range of $p_\perp\sim 2\, GeV$ originate mostly from the "rim" of the fireball, near the maximum of the radial flow at the freezeout surface, only the intersection of the "sound surface" with this "rim" would be observable. The resulting "jet edge" has a form of extra matter at the elliptic curve, in $\Delta \phi, \Delta \eta$ coordinates, with radius $|\Delta \phi| \sim |\Delta \eta |\sim 1$. In the case of large energy/momentum deposition $\sim 100 \, GeV$ we argue that the event should be considered as two sub-events, with interior of the "sound surface" having modified radial and directed flow. We further argue that in the kinematical range of $p_\perp\sim 3\, GeV$ the effect of that can be large enough to be seen on event-by-event basis. If so, this effect has a potential to become a valuable tool to address geometry of jet production and quenching.