Measurements of DVCS and DVMP at COMPASS

The study of DVCS and DVMP processes over a wide range in $x_{B}$ is an outstanding part of the scientific proposal for the COMPASS program after 2011. The measurement of the double-differential DVCS cross-section will provide information on the transverse size of the nucleon as function of $x_{B}$, often referred to as "nucleon tomography". Also, the combination of data samples collected with opposite beam charge and polarization will allow to single out terms related to the GPD $H$. The physics goals of the COMPASS GPD program will be discussed in detail, and projections on the achievable statistical and systematic accuracies will be given. The sensitivity of the COMPASS experimental apparatus to the DVCS signal has been investigated during dedicated pilot measurements in the years 2008 and 2009. Preliminary results on the observed DVCS and Bethe-Heitler signals are presented, and the comparison with Monte-Carlo simulations is discussed.