Measuring the charged particle multiplicity with ALICE

Abstract

The charged particle multiplicity distribution is one of the first measurements that ALICE will be able to perform. The knowledge of this basic property at a new energy is needed to configure Monte Carlo generators correctly with the aim of understanding the background of other, especially rare, processes including new physics. It allows to study the scaling behaviour and to verify model predictions. The unfolding of the measurement is a non-trivial task due to the finite precision and acceptance of the detector. Solutions are based on ? 2 minimization or iteratively using Bayes' theorem. Both approaches to unfold the spectrum are presented. Furthermore, the capabilities of the SPD fast OR trigger are shown that enable physics at very high multiplicities.

Reconstruction of jet properties in Pb-Pb collisions with the ALICE-Experiment

“…At lower p t,trig where particle production is not dominated by jet fragmentation, collective effects [7], have a strong influence on the ∆φ distributions and a Fourier-decomposition can be used to quantify the role of long range correlations (see e.g. [8]). Here, the trigger particle p t has been chosen such that collective effects on the ∆φ distribution are small and jet-like correlations dominate (p t,trig > 8 GeV/c, p t,assoc > 3 GeV/c).…”