New constraints on a light CP-odd Higgs boson and related NMSSM ideal Higgs scenarios

Recent BABAR limits on BR(Υ(3S)→γa→γτ⁺τ^-) and BR(Υ(3S)→γa→γμ⁺μ^-) provide increased constraints on the abb¯ coupling of a CP-odd Higgs boson, a, with m_a<M_Υ(3S). We extract these limits from the BABAR data and compare to the limits previously obtained using other data sets, especially the CLEO-III BR(Υ(1S)→γ→τ⁺τ^-) limits. Comparisons are made to predictions in the context of “ideal”-Higgs NMSSM scenarios, in which the lightest CP-even Higgs boson, h₁, can have mass below 105 GeV (as preferred by precision electroweak data) and yet can escape old LEP limits by virtue of decays to a pair of the lightest CP-odd Higgs bosons, h₁→a₁a₁, with m_a1<2m_B. Most such scenarios with m_a1<2m_τ are eliminated, but the bulk of the m_a1>7.5GeV scenarios, which are theoretically the most favored, survive. We also outline the impact of the new ALEPH LEP results in the e⁺e^-→Z+4τ channel. For tan⁡β≥3, only NMSSM ideal Higgs scenarios with m_h1≳98GeV and m_a1 close to 2m_B satisfy the ALEPH limits. For tan⁡β≲2, the ALEPH limits are easily satisfied for the most theoretically preferred NMSSM scenarios, which are those with m_a1 close to 2m_B and m_h1∼90-100GeV.