Beam parameter determination using beamstrahlung photons and incoherent pairs

The beam calorimeter BeamCal and the photon calorimeter GamCal of the ILC detectors will be used to obtain a set of parameters describing the beam properties at the interaction point. The real-time determination of the parameters is a challenge, but is mandatory to achieve the best possible luminosity for the ILC. We report on our studies about the possibilities to reduce the number of readout channels of BeamCal without significant loss of precision in the beam parameter determination. In addition, the benefit of measuring the beamstrahlung photons energy using GamCal is evaluated. Finally we report on the achievable precision of and the observed correlations between the beam parameters reconstructed in the multi-parameter regime. We also comment on possible solutions how to deal with these correlations.