The DVCS physics program at COMPASS

29 Apr 2015, 08:55


WG6 Spin Physics WG6 Spin Physics


Philipp Karl Jorg (Albert-Ludwigs-Universitaet Freiburg (DE))


A major part of the COMPASS-II program will be dedicated to the investigation of generalized parton distributions (GPDs) and transverse momentum dependent parton distributions (TMDs), which aim for the most complete description of the partonic structure of the nucleon. GPDs are experimentally accessible via lepton-induced exclusive reactions, in particular the Deeply Virtual Compton Scattering (DVCS) and Deeply Virtual Meson Production (DVMP). At COMPASS, those processes are investigated using an high intensity muon beam of 160 GeV and a 2.5 m-long liquid hydrogen target. In order to optimize the selection of exclusive reactions at those energies, the target is surrounded by a new barrel-shaped time-of-flight system to detect the recoiling particles. COMPASS-II covers the up to now unexplored $x_{Bj}$ domain ranging from 0.01 to 0.15. The option to change simultaneously the charge and polarization of the muon beam allows to access the Compton form factor related to the dominant GPD $H$, and thus to provide new experimental constraints on the theoretical GPD models in the intermediate $x_{Bj}$ regime. Moreover, the $x_{Bj}$-dependence of the nucleon transverse size is investigated via the pure DVCS cross-section that can be extracted from the sum of cross-sections measured with positive and negative beam polarity. Preliminary results of pilot measurements and projections on the achievable accuracies will be presented. Supported by BMBF and EU FP7 (Grant Agreement 283286) On Behalf of the COMPASS Collaboration

Primary author

Philipp Karl Jorg (Albert-Ludwigs-Universitaet Freiburg (DE))

Presentation Materials