# Probing jet energy redistribution and broadening in pp and Pb-Pb collisions with ALICE

- Institution: CERN
- Department: LHC Seminar
- Speaker: Jaime Norman
- Year: 2023
- Language: English
- Subjects: Earth and environment
- Source: [CERN](https://videos.cern.ch/record/3014542)
- Licence: [CERN](http://copyright.web.cern.ch)
- Who can watch: Tweens profiles and older (sources give no ratings; placed by Invisible Network from the source's own words)

Jets are generated in heavy-ion collisions, and their interactions with the Quark-Gluon Plasma (QGP) produced in such collisions provide unique probes of QGP properties. Experimentally observable consequences of jet-QGP interactions include jet energy loss, modification of intra-jet structure, and jet angular deflection. Jet deflection can occur via multiple soft scatterings or single-hard Moliere scatterings off QGP constituents, and its observation will probe the nature of QGP quasi-particles. Such effects are expected to be most prominent at low jet transverse momentum ($p_\mathrm{T}$), which is where jet measurements are also sensitive to wake effects due to response of the QGP itself to the jet-medium energy transfer. Measurements that are differential in jet $p_\mathrm{T}$, jet radius $R$, and acoplanarity (deflection angle) may be able to disentangle these various mechanisms.

This talk presents new measurements of the semi-inclusive distribution of charged-particle jets recoiling from a trigger hadron in pp and central Pb--Pb collisions at $\sqrt{s_\mathrm{NN}}=5.02$ GeV. The measurement is performed using a background-subtraction technique which provides a precise data-driven subtraction of the large uncorrelated background contaminating the measurement, uniquely enabling the measurement of jet production and acoplanarity over a wide phase space, including the low jet $p_\mathrm{T}$ region for large $R$. This measurement in pp collisions provides a test of pQCD predictions for this process. We observe a striking medium-induced enhancement in recoil jet yield at low $p_\mathrm{T,jet}$, whose R-dependence enables a clear discrimination of in-medium jet scattering and QGP wake effects. The in-medium suppression of recoil yield at higher $p_\mathrm{T,jet}$ provides new insight into the mechanisms underlying jet quenching. Comparison to model calculations and their dependence on jet $R$ will be shown to interpret the results.

Refreshments will be served at…

## Lectures

1. [Probing jet energy redistribution and broadening in pp and Pb-Pb collisions with ALICE](https://invisiblenetwork.ai/learn/cern/3014542/244325273858), 1 h 14 min (CERN's player)