[Deeppwg] [EXTERNAL] Deep exclusive process abstract for IWHSS2020

[Marco Contalbrigo]

Dear all,
below is a deep exclusive process abstract by Maxime
Defurne for the IWHSS2020 Workshop. If you have
suggestions, they are welcome.
Best regards, Marco.

Recent CLAS12 results on deep exclsuive processes

While it has been known since the 60s that nucleons are composed of
quarks and gluons, very little is understood about the mechanisms
responsible for the emergence of nucleons from these partons. Defined in
the 90s, Generalized Parton Distributions (GPDs) provide the opportunity
to obtain a 3-dimensional, tomographic picture of a nucleon. Moreover,
GPDs are related, via QCD-based sum rules, to total angular momentum,
mass and pressure distributions inside the nucleon. GPDs are
experimentally accessible via deep exclusive processes (DES), i.e.
the absorption of a highly virtual photon by the proton and the
subsequent emission of a high-energy photon or meson.

At Jefferson Lab, the brand new CLAS12 spectrometer has been
commissioned and has collected data with a 10.6 GeV longitudinally-polarized
continuous electron beam since 2018. Its central part,
containing the cylindrical silicon and micromegas trackers within a
5T-solenoidal field surrounding the liquid hydrogen target, is ideal to
detect the recoil proton of a DES event. The forward detectors, placed
in a toroidal magnetic field, detect the associated scattered electron
and photon/meson. We will present preliminary results regarding
DVCS on neutron and proton, as well as neutral pion electroproduction on
proton.