# Quark Matter 2017

Feb 5 – 11, 2017
Hyatt Regency Chicago
America/Chicago timezone

## Angular Structure of Jet Quenching within a Hybrid Strong/Weak Coupling Model

Feb 7, 2017, 10:40 AM
20m
Regency D

### Regency D

Oral Jets and High pT Hadrons

### Speaker

Krishna Rajagopal (Massachusetts Inst. of Technology (US))

### Description

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, meaning that
the wake contributes to what is reconstructed as a jet. This effect must
therefore be included in any description of the angular structure
of the soft component of a jet.
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.
More generally, 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.

Preferred Track Jets and High pT Hadrons Not applicable

### Primary author

Krishna Rajagopal (Massachusetts Inst. of Technology (US))