Diffractive photon production at high momentum transfer in $ep$ collisions

The diffractive photon production at large momentum transfer and large energies is a probe of the parton dynamics of the diffractive exchange. In this paper we revisit the leading order (LO) BFKL equation approach for this process and estimate, for the first time, the differential and total cross sections considering the next-to-leading order (NLO) corrections for the BFKL characteristic function. We obtain a reasonable agreement with the DESY HERA data.