Jets and Photons in ALICE

TL;DR

This paper reports measurements of neutral mesons and jets in proton-proton and lead-lead collisions at various energies, comparing experimental results with theoretical predictions and analyzing jet quenching effects in heavy-ion collisions.

Contribution

It provides new experimental data on meson spectra and jet properties in Pb-Pb collisions, and assesses the agreement with NLO pQCD calculations, including background fluctuation analysis for jet studies.

Findings

NLO pQCD overestimates meson production at higher energies.

Strong suppression of high-pt neutral pions in central Pb-Pb collisions.

Background fluctuation analysis enables soft fragmentation studies in quenched jets.

Abstract

ALICE measured transverse momentum spectra of pi0 and eta mesons via the two photon decay in pp collisions at sqrt(s)=0.9, 2.76 and 7 TeV and Pb-Pb collisions at sqrt(sNN)=2.76 TeV. NLO pQCD calculations agree with p-p measurements at 0.9 TeV, but overestimate the data at 2.76 and 7 TeV. The nuclear modification factor for neutral pions shows a strong suppression of high-pt particle production in central Pb-Pb collisions. Raw spectra of charged particle jets have been measured in Pb-Pb collisions. Detailed studies of background fluctuations have been performed and will allow us to unfold the spectra even for low momentum cut offs, giving access to soft fragmentation products in quenched jets.