Process Z{\rightarrow}h(A)+\gamma in the 2HDM and the experimental constraints from LEP

The one-loop branching ratios for the process are calculated in the general two Higgs doublet model (Model II), taking into account existing constraints on the model parameters. For Higgs boson masses below 50 GeV and of the fraction of such Z decays are at the level of , but can be significantly stronger for very low or high , where the dependence of these results on other model parameters like and the mass of the charged Higgs boson is found to be of little importance. The results are compared to the LEP measurements, which are sensitive to branching ratios of of the order for masses GeV, but approach for low masses. By relating the expectation to the experimental limits, constraints on the parameter space of the 2HDM are derived. Received: 28 November 1998 / Published online: 27 April 1999