EPJ

2023 Impact factor 4.2
EPJ C - Particles and Fields
Particles and Fields
Eur. Phys. J. C 8, 495-505
DOI 10.1007/s100529901090

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

M. Krawczyk1 - J. $\dot{\rm Z}$ochowski1 - P. Mättig2

1 Institute of Theoretical Physics, University of Warsaw, PL-00-681 Warsaw, Poland
2 Weizmann Institute, Rehovot, Israel

Received: 28 November 1998 / Published online: 27 April 1999

Abstract
The one-loop branching ratios for the process $Z{\rightarrow}h(A)+\gamma$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 50GeV and $\tan \beta$ of ${\cal O}(1-10)$ the fraction of such Z decays are at the level of 10-7, but can be significantly stronger for very low or high $\tan \beta$, where the dependence of these results on other model parameters like $\sin (\beta - \alpha )$ 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 $Z{\rightarrow}h(A)+\gamma$ of the order 10-5 for masses $\ge $20GeV, but approach 10-6 for low masses. By relating the expectation to the experimental limits, constraints on the parameter space of the 2HDM are derived.

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