Dispersive evaluation of the D-term form factor in deeply virtual   Compton scattering
  We present a dispersive representation of the D-term form factor for hard exclusive reactions, using unsubtracted $t$-channel dispersion relations. The $t$-channel unitarity relation is saturated with the contribution of two-pion intermediate states, using the two-pion distributions amplitude for the $\gamma^*\gamma\rightarrow \pi\pi$ subprocess and reconstructing the $\pi\pi\rightarrow N\bar N$ subprocess from available information on pion-nucleon partial-wave helicity amplitudes. Results for the D-term form factor as function of $t$ as well as at $t=0$ are discussed in comparison with available model predictions and phenomenological parametrizations. 
B. Pasquini (Pavia U. and INFN, Pavia), M.V. Polyakov (Ruhr U.,   Bochum), and M. Vanderhaeghen (Mainz U., Inst. Kernphys. a...
hep-ph hep-ex nucl-ex nucl-th