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 -> pi pi subprocess and reconstructing the pi pi -> N (N) over bar 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. (C) 2014 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license