Multi-Higgs doublet model: Can it account for ℓ⁺ℓ⁻γγ events?

Summary

Motivated by recent experiments at LEP (Z →ℓ⁺ ℓ⁻ γγ, withMγγ-59 GeV), we examine the possibility that such events are explained by a Bjorken process with a resonant Higgs (M _ho ≏59 GeV) decaying to γγ. We investigate theN-doublet-Higgs model withoutCP violation. Under the simplifying assumption that(N-k) doublets (k≥ 1) decouple from the fermion sector, we could only explain the observed events if: i)(N- 1) ≥ 2 and ii) the masses of the corresponding(N- 1) neutral scalars are either completely or almost degenerate,i.e. the decay Z →ℓ⁺ℓ⁻ γγ proceeds now via several overlapping resonances. Such a scenario would require fine tuning. Furthermore, the deficit of the observed decays Z → → vvγ, qqγγ (atMγγ∽59 GeV) indicates that one either has to go beyond simple extensions of the minimal standard model, or one has to wait for more experimental data.