Abstract
We compute modifications to the jet spectrum in the presence of a dense medium. We show that in the large-$N_c$ approximation and at leading logarithmic accuracy the jet nuclear modification factor factorizes into a quenching factor associated to the total jet color charge and a Sudakov suppression factor which accounts for the energy loss of jet substructure fluctuations. This factor, called the jet collimator, implements the fact that subjets, that are not resolved by the medium, lose energy coherently as a single color charge, whereas resolved large angle fluctuations suffer more quenching. For comparison, we show that neglecting color coherence results in a stronger suppression of the jet nuclear modification factor.
Highlights
The properties of fully reconstructed jets in heavy-ion collisions [1,2,3,4] reveal the effects of notable final state interactions
We focus on the leading logarithmic (LL) behavior, that is z ≪ 1 and θ ≫ θc
We have found that substructure fluctuations give rise to an additional suppression of the jet spectrum at high-pT in heavy-ion collisions beyond the energy loss experienced by the total color charge of the jet
Summary
The properties of fully reconstructed jets in heavy-ion collisions [1,2,3,4] reveal the effects of notable final state interactions. Owing to the QCD mass singularity, the jet-initiating parton tends to branch rapidly—in particular inside the medium This leads one to question the single charge energy loss approximation for jet quenching at high-pT. In the medium induced energy loss of the final-state particles causes a mismatch between real and virtual diagrams that is accompanied by logarithms of the available phase space. This takes place whenever the medium resolves the individual color charges created in hard splittings, namely at the time t 1⁄4 td ∼ ðqθ2Þ−1=3, when the transverse distance between the two daughters, r⊥ ∼ θt, becomes of order the medium correlation length ðqtÞ−1=2.
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