Jet structure in 2.76 TeV Pb Pb collisions at ALICE

TL;DR

This paper analyzes how high-energy jets are modified in heavy-ion collisions at 2.76 TeV, using a novel background subtraction method to compare Pb Pb and pp collisions and study jet quenching effects.

Contribution

It introduces a new technique for background subtraction in jet measurements that avoids fragmentation bias, enabling more accurate comparisons between Pb Pb and pp collisions.

Findings

Jet structure is modified in Pb Pb collisions compared to pp.

Background subtraction method effectively isolates jet signals.

Jet quenching effects depend on cone radius and constituent pT cutoff.

Abstract

We present the analysis of the semi-inclusive distribution of reconstructed charged particle jets recoiling from a high pT hadron trigger in central Pb Pb collisions at $\sqrt{s_{NN}}=2.76$ TeV. We measure, subtract and unfold the large underlying event background in such collisions, utilizing a novel technique that does not impose fragmentation bias on the measured jet population. The Pb Pb measurements are compared to a pp PYTHIA reference distribution generated at the same $\sqrt{s}$. Modification of jet structure due to quenching is explored by varying the cone radius $R$ (0.2, 0.4) and the lower pT cutoff of charged particle constituents (0.15, 2.0 GeV/$c$).