Neutral meson and direct photon analysis with ALICE

Abstract

The measurement of neutral mesons, particularly π0, s and η’s, plays an important role in the study of the Quark-Gluon Plasma (QGP), the hot and dense medium created in high-energy heavy-ion collisions. Parton energy loss in the QGP, often called jet quenching, can be assessed via measuring the suppression of high-pT π0, s in heavy-ion collisions, when compared to pp collisions using the nuclear modification factor (Raa). Furthermore, neutral mesons are the dominant source of photons in pp and Pb-Pb collisions, and their precise measurement is required to measure direct photons that are produced thermally within the QGP or in hard initial scatterings in the earliest phases of the collision. In both cases, high- quality measurements in pp collisions are required as a reference for Pb-Pb collisions. ALICE measurements of neutral meson spectra cover a large pT range, with the Photon Conversion Method - which requires measurements from the ITS and TPC - covering low to intermediate pT and the PHOS and EMCal electromagnetic calorimeters covering an intermediate to high pT range. In this presentation, measurements of π0, s and η’s obtained from the ALICE experiment, for pp collisions at several collisional center of mass energies from 0.9 TeV to 8 TeV and in Pb-Pb collisions at will be presented. The reconstruction of neutral mesons using the Photon Conversion Method (PCM) will also be discussed.