COMPASS Calorimetry in view of future plans

The COMPASS experiment at the CERN SPS is dedicated to hadron physics with a broad research programme, including the study of the nucleon spin structure using muons as a probe and a variety of issues in meson spectroscopy using hadron beams. The two stage fixed target spectrometer with electromagnetic (em) and hadronic calorimetry in both stages provides photon detection in a wide angular range. As discussed in this paper, the COMPASS em calorimetry plays a crucial r\^{o}le for the Hadron programme started in 2008 as well as for the planned COMPASS future programme of measuring GPDs via exclusive DVCS photons. We present the photon detection coverage foreseen, and first, preliminary results characterising the present performances of both existing COMPASS electromagnetic calorimeters, based on test beam data taken at CERN T9 facility end of 2007

COMPASS Hadron Spectroscopy -- Final states involving neutrals and kaons

The COMPASS experiment at CERN is well designed for light-hadron spectroscopy with emphasis on the detection of new states, in particular the search for $J^{PC}$-exotic states and glueballs. We have collected data with 190 GeV/c charged hadron beams on a liquid hydrogen and nuclear targets in 2008/09. The spectrometer features good coverage by electromagnetic calorimetry and a RICH detector further provides $\pi$ / $K$ separation, allowing for studying final states involving neutral particles like $\pi^0$ or $\eta$ as well as hidden strangeness, respectively. We discuss the status of ongoing analyses with specific focus on diffractively produced $(\pi^0\pi^0\pi)^{-}$ as well as $(K\bar{K}\pi)^{-}$ final states.Comment: 3 pages, 4 figures, Conf. Proc., to appear in the Intern. Journal of Modern Phys. A, 11th Intern. Workshop on Meson Production, Properties and Interaction, KRAK\'OW, POLAND, 10-15 June 201

On the disputed π1(1600)\pi_1(1600) resonance and observation of a new iso-vector resonance

The COMPASS experiment at CERN delivers new results on the search for exotic mesons. A spin-exotic resonance, the $\pi_1(1600)$, was reported by several experiments in the past. Those observations are, however, still to date highly disputed in the community. Especially the $\rho\pi$ decay channel allows for simultaneous observation of well established and less known resonances in different decay modes. The results from amplitude analysis of diffractively produced $(3\pi)^{-}$ final states show consistently a spin-exotic signal, that appears in agreement with previous observations of the $\pi_1(1600)$. The high-statistics 2008 data sample allows and demands for an extended amplitude analysis method that further disentangles resonant and non-resonant particle production. The present status of analysis of COMPASS data and the observation of a new iso-vector meson $a_1(1420)$ is discussed.Comment: 6 pages, 24 figures, DSPIN-13 Conference Proceedings, to appear in the proceedings of the XV Workshop on High Energy Spin Physics, Dubna, Russia, October 8-12, 201

Meson spectroscopy with COMPASS

The COMPASS fixed-target experiment at CERN SPS is dedicated to the study of hadron structure and dynamics. In the physics programme using hadron beams, the focus is on the detection of new states, in particular the search for $J^{PC}$ exotic states and glueballs. After a short pilot run in 2004 (190 GeV/c negative pion beam, lead target), we started our hadron spectroscopy programme in 2008 by collecting an unprecedented statistics with a negative hadron beam (190 GeV/c) on a liquid hydrogen target. A similar amount of data with positive hadron beam (190 GeV/c) has been taken in 2009, as well as some additional data with negative beam on nuclear targets. The spectrometer features a large angular acceptance and high momentum resolution and also good coverage by electromagnetic calorimetry, crucial for the detection of final states involving $\pi^0$ or $\eta$. A first important result is the observation of a significant $J^{PC}$ spin exotic signal consistent with the disputed $\pi_1(1600)$ in the pilot run data. This result was recently published. We present an overview of the status of various ongoing analyses on the 2008/09 data.Comment: 6 pages, 6 figures, to appear in the proceedings of the International Nuclear Physics Conference 2010, Vancouver, Canada, 04-09 Jul 201

A Macroscopic Description of Coherent Geo-Magnetic Radiation from Cosmic Ray Air Showers

We have developed a macroscopic description of coherent electro-magnetic radiation from air showers initiated by ultra-high energy cosmic rays due to the presence of the geo-magnetic field. This description offers a simple and direct insight in the relation between the properties of the air shower and the time-structure of the radio pulse.Comment: 10 pages, 8 figures; submitted to Astroparticle Physic

Hadron Spectroscopy with COMPASS at CERN

The aim of the COMPASS hadron programme is to study the light-quark hadron spectrum, and in particular, to search for evidence of hybrids and glueballs. COMPASS is a fixed-target experiment at the CERN SPS and features a two-stage spectrometer with high momentum resolution, large acceptance, particle identification and calorimetry. A short pilot run in 2004 resulted in the observation of a spin-exotic state with $J^{PC} = 1^{-+}$ consistent with the debated $\pi1(1600)$. In addition, Coulomb production at low momentum transfer data provide a test of Chiral Perturbation Theory. During 2008 and 2009, a world leading data set was collected with hadron beam which is currently being analysed. The large statistics allows for a thorough decomposition of the data into partial waves. The COMPASS hadron data span over a broad range of channels and shed light on several different aspects of QCD.Comment: 4 pages, 5 figure