The COMPASS Setup for Physics with Hadron Beams

TL;DR

The paper describes the design, components, and performance of the COMPASS experimental setup for hadron physics, highlighting its capabilities for exclusive measurements with high flux, large coverage, and good mass resolution.

Contribution

It introduces new and upgraded detectors and systems enabling precise hadron physics measurements at CERN with high flux and broad acceptance.

Findings

Successful operation with positive and negative hadron beams

High angular and momentum coverage achieved

Good two- and three-particle mass resolutions obtained

Abstract

The main characteristics of the COMPASS experimental setup for physics with hadron beams are described. This setup was designed to perform exclusive measurements of processes with several charged and/or neutral particles in the final state. Making use of a large part of the apparatus that was previously built for spin structure studies with a muon beam, it also features a new target system as well as new or upgraded detectors. The hadron setup is able to operate at the high incident hadron flux available at CERN. It is characterised by large angular and momentum coverages, large and nearly flat acceptances, and good two and three-particle mass resolutions. In 2008 and 2009 it was successfully used with positive and negative hadron beams and with liquid hydrogen and solid nuclear targets. This article describes the new and upgraded detectors and auxiliary equipment, outlines the reconstruction procedures used, and summarises the general performance of the setup.