Reduced branching ratio for H → AA → 4 τ from A − η b mixing

Models with an extended Higgs sector, as the NMSSM, allow for scenarios where the Standard Model-like CP-even Higgs boson H decays dominantly as H → AA → 4τ where A is a light CP-odd Higgs boson. Tight constraints on this scenario in the form of lower bounds on M H have recently been published by the ALEPH group. We show that, due to A − η b mixing, the branching ratio H → AA → 4τ is strongly reduced for M A in the range 9–10.5 GeV. This is the range of M A in which the tension between the observed η b (1S) mass and its prediction based on QCD can be resolved due to mixing, and which is thus still consistent with a light CP-even Higgs boson H satisfying LEP constraints with a masswellbelow114GeV. This result is practically independent from the coupling of A to b quarks.