The t-dependence of the pure DVCS cross section at COMPASS

الأصل · EN

The key reactions to study the Generalised Parton Distributions are Deeply Virtual Compton Scattering (DVCS) and Deeply Virtual Meson Production (DVMP). At COMPASS, these processes are investigated using a high intensity muon beam with a momentum of 160GeV/c and a 2.5m-long liquid hydrogen target. In order to optimize the selection of exclusive reactions at these 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 xB domain ranging from 0.01 to 0.15. From the sum of cross sections measured with positive and negative beam polarities, the pure DVCS cross-section and its t-dependence have been extracted resulting in a first model-independent determination of the transverse size of the partonic distribution of the nucleon √<r⊥²>= (0.578 ± 0.042₋ ₀.₀₁₈⁺ ⁰.⁰⁰⁶)fm at a mean xB value of 0.056.