Abstract
Within the context of a hybrid strong/weak coupling model of jet quenching, we study the consequences of the fact that the plasma produced in a heavy ion collision cannot resolve the substructure of a collimated parton shower propagating through it with arbitrarily fine spatial resolution. We introduce a screening length parameter, Lres, proportional to the inverse of the local temperature in the plasma, estimating a range for the value of the proportionality constant via comparing weakly coupled QCD calculations and holographic calculations appropriate in strongly coupled plasma. We then modify the hybrid model so that when a parton in a jet shower splits, its two offspring are initially treated as unresolved, and are only treated as two separate partons losing energy independently after they are separated by a distance Lres. This modification delays the quenching of partons with intermediate energy, resulting in the survival of more hadrons in the final state with pT in the several GeV range. We analyze the consequences of different choices for the value of the resolution length, Lres, and demonstrate that introducing a nonzero Lres results in modifications to the jet shapes and jet fragmentations functions, as it makes it more probable for particles carrying a small fraction of the jet energy at larger angles from the jet axis to survive their passage through the quark-gluon plasma. These effects are, however, small in magnitude, something that we confirm via checking for effects on missing-pT observables.
Highlights
Produced at the moment of the collision in initial hard scatterings, as probes
Within the context of a hybrid strong/weak coupling model of jet quenching, we study the consequences of the fact that the plasma produced in a heavy ion collision cannot resolve the substructure of a collimated parton shower propagating through it with arbitrarily fine spatial resolution
These interactions lead to a reduction in the jet energy and to modifications of the properties of jets produced in heavy ion collisions relative to those of their counterparts produced in proton-proton collisions, that propagate in vacuum
Summary
When one parton in a jet shower splits into two, the two offspring will initially be arbitrarily close together. We conclude that in a strongly coupled plasma, Lres is of order λD, not shorter. For a thick medium at weak coupling, the argument is more subtle because quantum interference over the course of multiple soft interactions with the√medium as a hard parton propagates for a distance L introduces a new length scale, 1/ qL. In the strict weak coupling limit, this argument suffices We shall take this as sufficient evidence to proceed using the assumption that Lres ∼ λD, as this is valid in a strongly coupled plasma as well as in a weakly coupled plasma except for the case where θant < O(g) in a plasma that is both thick and weakly coupled, a case that can be returned to in future work. We will explore the consequences of choosing the proportionality constant Rres = 1 and Rres = 2, spanning the reasonable range for the resolution length in either strongly coupled or weakly coupled QCD plasma. We do so in order to check the robustness of our results, i.e. for the purpose of confirming that none of the results we report are hypersensitive to the value of Lres that we choose
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
