Heidelberg 2015 – scientific programme

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HK: Fachverband Physik der Hadronen und Kerne

HK 18: Hadron Structure and Spectroscopy 3

HK 18.1: Group Report

Monday, March 23, 2015, 17:00–17:30, T/SR19

Status of the GPD program @ COMPASS II — •Matthias Gorzellik, Horst Fischer, Philipp Jörg, Kay Königsmann, Steffen Landgraf, Christopher Regali, Katharina Schmidt, Stefan Sirtl, Tobias Szameitat, and Johannes ter Wolbeek — for the COMPASS collaboration, Physikalisches Institut, Albert-Ludwigs-Universität Freiburg

The COMPASS-II experiment is a fixed target experiment situated at CERN. A tertiary myon beam from the SPS scattered of protons from a liquid hydrogen target is used to measure Deeply Virtual Compton Scattering (DVCS) and Hard Exclusive Meson Production (HEMP).

Both processes open a unique window to constrain Generalized Parton Distributions, which are related to the total angular momentum of quarks, antiquarks and gluons in the nucleon. An upgrade of the previous experiment was started in 2012. The major parts of the upgrade for the measurement of exclusive reactions are the recoil proton detector (CAMERA) and an additional Electromagnetic Calorimeter.

The close to final setup allows for a measurement of exclusive reactions with very low cross sections in a wide kinematic range. A pilot run, covering five weeks of data taking, was performed at the end of 2012. In this talk we will present first results from the analysis.

Supported by BMBF and EU FP7 (Grant Agreement 283286).