arXiv : Angular Structure of Jet Quenching Within a Hybrid Strong/Weak Coupling Model

Casalderrey-Solana, Jorge; Gulhan, Doga; Pablos, Daniel; Milhano, Guilherme; Rajagopal, Krishna

doi:10.1007/JHEP03(2017)135

Article
Report number	arXiv:1609.05842 ; ICCUB-16-033 ; CERN-TH-2016-201 ; MIT-CTP-4830
Title	Angular Structure of Jet Quenching Within a Hybrid Strong/Weak Coupling Model
Author(s)	Casalderrey-Solana, Jorge (Oxford U., Theor. Phys. ; Barcelona U. ; ICC, Barcelona U.) ; Gulhan, Doga (CERN) ; Milhano, Guilherme (Lisbon, CENTRA ; LIP, Lisbon ; CERN) ; Pablos, Daniel (Barcelona U. ; ICC, Barcelona U.) ; Rajagopal, Krishna (MIT, Cambridge, CTP)
Publication	2017-03-27
Imprint	19 Sep 2016
Number of pages	62
Note	62 pages, 14 figures
In:	JHEP 03 (2017) 135
DOI	10.1007/JHEP03(2017)135
Subject category	nucl-th ; Nuclear Physics - Theory ; hep-ph ; Particle Physics - Phenomenology
Abstract	Within the context of a hybrid strong/weak coupling model of jet quenching, we study the modification of the angular distribution of the energy within jets in heavy ion collisions, as partons within jet showers lose energy and get kicked as they traverse the strongly coupled plasma produced in the collision. To describe the dynamics transverse to the jet axis, we add the effects of transverse momentum broadening into our hybrid construction, introducing a parameter $K\equiv \hat q/T^3$ that governs its magnitude. We show that, because of the quenching of the energy of partons within a jet, even when $K\neq 0$ the jets that survive with some specified energy in the final state are narrower than jets with that energy in proton-proton collisions. For this reason, many standard observables are rather insensitive to $K$. We propose a new differential jet shape ratio observable in which the effects of transverse momentum broadening are apparent. We also analyze the response of the medium to the passage of the jet through it, noting that the momentum lost by the jet appears as the momentum of a wake in the medium. After freezeout this wake becomes soft particles with a broad angular distribution but with net momentum in the jet direction. We show that the particles coming from the response of the medium to the momentum and energy deposited in it leads to a correlation between the momentum of soft particles well separated from the jet in angle with the direction of the jet momentum, and find qualitative but not quantitative agreement with experimental data on observables designed to extract such a correlation. By confronting the results that we obtain upon introducing transverse momentum broadening and the response of the medium to the jet with available jet data, we highlight the importance of these processes for understanding the internal, soft, angular structure of high energy jets.
Copyright/License	arXiv nonexclusive-distrib. 1.0 preprint: © 2016-2024 CERN (License: CC-BY-4.0) publication: © 2017-2024 The Author(s) (License: CC-BY-4.0), sponsored by SCOAP³

$When we introduce transverse momentum broadening via a nonzero value of the broadening parameter $K$, this introduces a small increase in energy loss. This means that for each nonzero value of $K$ we need to refit the value of the energy loss parameter $\aSC$ to the measured value~\cite{Raajet:HIN} of $\RAA^{\rm jet}$ for jets with 100~GeV$<p_{\rm T}< 110$~GeV and $-2<\eta<2$, as in Refs.~\cite{Casalderrey-Solana:2014bpa,Casalderrey-Solana:2015vaa}. The resulting dependence of $\aSC$ on the broadening parameter $K$ is mild. As in Refs.~\cite{Casalderrey-Solana:2014bpa,Casalderrey-Solana:2015vaa}, the width of the band of values of $\aSC$ in this figure (and the consequent widths of the bands depicting our hybrid model predictions in subsequent figures) comes both from the error bar on the experimentally measured data point used to fix $\aSC$ and from varying the crossover temperature $T_c$ as described in Section~\ref{MC} in order to get some sense of the systematic uncertainties in the hybrid model.$ $Dependence of $\RAA^{\rm jet}$ on the anti-$k_t$ jet reconstruction parameter $R$ for $K=0$ (no broadening, left panel) and $K=40$ (right panel). For comparison, we show the suppression of jets reconstructed using the anti-$k_t$ algorithm with $R=0.3$ as measured by CMS in the same interval of rapidity~\cite{Raajet:HIN}.$ $Dependence of $\RAA^{\rm jet}$ on the anti-$k_t$ jet reconstruction parameter $R$ for $K=0$ (no broadening, left panel) and $K=40$ (right panel). For comparison, we show the suppression of jets reconstructed using the anti-$k_t$ algorithm with $R=0.3$ as measured by CMS in the same interval of rapidity~\cite{Raajet:HIN}.$ Show more plots

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