Speaker
Mr
Andrea Ferrero
(CEA-Saclay/IRFU/DPhN)
Description
Together, GPDs and TMDs provide the most complete description of the
partonic structure of the nucleon, and their study represents the major
goal of the COMPASS-II program.
GPDs are experimentally accessible via lepton-induced exclusive reactions, in
particular DVCS and DVMP. At COMPASS, these processes are investigated
using a 160 GeV high intensity muon beam impinging on a 2.5~m 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.
The pure DVCS cross-section and its $|t|$-dependence
are extracted from the sum of cross-sections measured with opposite beam
charges and polarizations.
From this measurement, the first estimate of the transverse size
of the nucleon in the uncharted $x_{Bj}$ domain from 0.02 to
0.20 will be given.
COMPASS is also capable of accessing several DVMP channels, from which
different combinations of quark and gluon GPDs can be extracted. In this
talk we will report on the first measurement of the exclusive $\pi^0$
cross section and its $|t|$-dependence in the same $x_{Bj}$ domain from
0.02 to 0.20.
Primary author
Mr
Andrea Ferrero
(CEA-Saclay/IRFU/DPhN)
