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 γ⁎γ→ππγ⁎γ→ππ subprocess and reconstructing the ππ→NN¯ 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=0t=0 are discussed in comparison with available model predictions and phenomenological parametrizations.