Speaker
Description
Generalized Parton Distributions (GPDs) describe the correlations between the longitudinal
momentum and the transverse position of the partons inside the nucleon. They give access to the
contribution of the orbital momentum of the quarks to the nucleon spin. They are nowadays the
subject of an intense effort of research, in the perspective of understanding nucleon structure. GPDs
have been studied in several experiments worldwide mainly using Deeply Virtual Compton
Scattering (DVCS, ep → e’p’γ).
This talk will be composed of two parts. In the first part, the Central Neutron Detector will be
presented. This scintillator time-of-flight detector has been built at IPN and installed in CLAS12 at
Jlab in the Fall 2017. The CND will allow to perform DVCS measurements on neutron (en →
e’n’γ). In the second part, the measurement, using CLAS12 data, of the time-reversal conjugate
process of DVCS, Timelike Compton Sattering (TCS) will be discussed. TCS (γp → γ*p’ →e + e -
p’ ) is the photoproduction of a virtual timelike photon off the proton, which then decays into a
lepton pair. Experimental studies of DVCS and TCS are complementary.
