Results from cosmics and first LHC beam with the ALICE HMPID detector

TL;DR

This paper reports on the commissioning and initial performance results of the ALICE HMPID detector during cosmics and first LHC beam tests, demonstrating stable operation and successful detector alignment.

Contribution

It provides the first operational experience and performance evaluation of the ALICE HMPID detector during initial LHC runs and cosmic ray data collection.

Findings

Stable operation during LHC beam injection and circulation

Successful detector alignment using TPC tracking

Effective gain mapping and performance assessment

Abstract

The ALICE HMPID (High Momentum Particle IDentification) detector has been designed to identify charged pions and kaons in the range 1 < p < 3 GeV/c and protons in the range 1.5 < p < 5 GeV/c. It consists of seven identical proximity focusing RICH (Ring Imaging Cherenkov) counters, covering in total 11 m2, which exploit large area MWPC equipped with CsI photocathodes for Cherenkov light imaging emitted in a liquid C6F14 radiator. The ALICE detector has been widely commissioned using cosmics and LHC beam from December 2007 until October 2008. During the cosmics data taking the HMPID detector collected a large set of data, using mainly the trigger provided by the TOF detector. We present here preliminary results of detector alignment using TPC tracking. The HMPID could be operated in a stable way, at a safe HV setting, also during LHC beam injection and circulation tests, when a very large occupancy (up to 50%) was achieved. Resulting gain mapping and overall detector performance will also be discussed.