Abstract
We present the complete physical picture for the evolution of a high-energy jet propagating through a weakly-coupled quark-gluon plasma (QGP) by analytical and numerical investigation of thermalization of the soft components of the jet. Our results support the following physical picture: the leading particle emits a significant number of mini-jets which promptly evolve via multiple branching and thus degrade into a myriad of soft gluons, with energies of the order of the medium temperature T. Via elastic collisions with the medium constituents, these soft gluons relax to local thermal equilibrium with the plasma over a time scale which is considerably shorter than the typical lifetime of the mini-jet. The thermalized gluons form a tail which lags behind the hard components of the jet. Together with the background QGP, they behave hydrodynamically.
Highlights
A striking imbalance in dijet transverse momentum has been observed in central lead-lead collisions at the LHC[1, 2]
One natural theoretical interpretation of such a so-called jet quenching phenomenon is that the away-side jet has enough time to degrade into soft gluons due to medium-induced multiple branching
The emergent new picture for the in-medium jet evolution is as follows: the energy of the hard components of the jet is efficiently transmitted, via multiple, quasi-democratic, branchings, to a multitude of comparatively soft gluons[3,4,5,6,7,8], which relax to local thermal equilibrium with the plasma over a time scale considerably shorter than the branching time of the jet[9]
Summary
A striking imbalance in dijet transverse momentum has been observed in central lead-lead collisions at the LHC[1, 2]. One natural theoretical interpretation of such a so-called jet quenching phenomenon is that the away-side jet has enough time to degrade into soft gluons due to medium-induced multiple branching. [9] presented for the first time the picture of this evolution in longitudinal phase-space, with the longitudinal axis defined as the direction of propagation of the leading particle. This picture will be succinctly summarized in what follows
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