First Measurement of Timelike Compton Scattering

We present the first measurement of the timelike Compton scattering process, gamma p -> p'gamma* (gamma*-> e(+)e(-)) obtained with the CLAS12 detector at Jefferson Lab. The photon beam polarization and the decay lepton angular asymmetries are reported in the range of timelike photon virtualities 2.25 < Q'(2 )< 9 GeV2, squared momentum transferred 0.1 < -t < 0.8 GeV2, and average total center-of-mass energy squared s = 14.5 GeV2. The photon beam polarization asymmetry, similar to the beam-spin asymmetry in deep virtual Compton scattering, is sensitive to the imaginary part of the Compton form factors and provides a way to test the universality of the generalized parton distributions. The angular asymmetry of the decay leptons accesses the real part of the Compton form factors and thus the D-term in the parametrization of the generalized parton distributions.