Abstract

COMPASS is a multi-purpose fixed-target experiment at the CERN Super Pro- ton Synchrotron aimed at studying the structure and spectrum of hadrons. One main goal is the search for new hadronic states, in particular hybrid mesons and glueballs. Its large acceptance, high resolution, and high-rate capability make the COMPASS experiment an excellent device to study the spectrum of light-quark mesons in diffractive and central production up to masses of about 2.5 GeV/c 2 . COMPASS is able to measure final states with charged as well as neutral particles, so that resonances can be studied in different re- actions and decay channels. During 2008 and 2009, COMPASS took a large data sample using 190 GeV/c negative and positive hadron beams on various targets. We present new results from the analyses of this data set. One focus lies on the search for new mesons in diffractively produced multi-particle final states. Here novel analysis methods are ap- plied to study the dependence of partial waves on the squared four-momentum transfer t � from the beam to the target. This also leads to a better separation of resonant and non- resonant contributions. Finally an update will be given on the recent analysis of the pion polarizability, which tests chiral dynamics.

Highlights

  • The hadron structure and spectroscopy physics program of COMPASS covers a variety of physics processes and corresponding analyses, such as baryon spectroscopy, possible violations of the OZI rule [2] or the study of processes in the overlap region of strong and electromagnetic interactions [3]

  • The basic concepts of the Partial-Wave Analysis (PWA) applied to the COMPASS data will be explained by means of the diffractively produced three-pion systems

  • During the hadron structure and spectroscopy campaign in 2008 and 2009 large data sets could be obtained with the COMPASS spectrometer

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Summary

Motivation

EPJ Web of C onferences an experimental investigation of the light hadronic spectrum is still neccessary and new obseravtions can sheed light on this kinematical regime

The COMPASS experiment
Light meson spectroscopy
Partial-wave analysis
Tests of chiral dynamics
Conclusions

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