New constraints on a light CP-odd Higgs boson and related NMSSM Ideal Higgs Scenarios

Abstract

Recent BaBar limits on $\text{br}({\rm Y}(3S)\to \text{gam}a\to \text{gam}{\tau }^{+}{\tau }^{-})$ and $\text{br}({\rm Y}(3S)\to \text{gam}a\to \text{gam}{\mu }^{+}{\mu }^{-})$ provide increased constraints on the $ab\text{anti}b$ coupling of a CP-odd Higgs boson, $a$, with $m_a<M_{{\rm Y}(3S)}$. We extract these limits from the BaBar data and compare to the limits previously obtained using other data sets, especially the CLEO-III $\text{br}({\rm Y}(1S)\to \text{gam}\to {\tau }^{+}{\tau }^{-})$ limits. Comparisons are made to predictions in the context of "ideal"-Higgs NMSSM scenarios, in which the lightest CP-even Higgs boson, $h_1$, can have mass below $105\text{gev}$ (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, $h_1\to a_1{a}_1$, with $m_{a_1}<2m_B$. Most such scenarios with $m_{a_1}<2m_{\tau }$ are eliminated, but the bulk of the $m_{a_1}>7.5\text{gev}$ scenarios, which are theoretically the most favored, survive. We also outline the impact of the new ALEPH LEP results in the $\text{epem}\to Z+4\tau$ channel. For $\tan \beta \ge 3$, only NMSSM ideal Higgs scenarios with $m_{h_1}\text{gsim}98\text{gev}$ and $m_{a_1}$ close to $2m_B$ satisfy the ALEPH limits. For $\tan \beta \text{lsim}2$, the ALEPH limits are easily satisfied for the most theoretically preferred NMSSM scenarios, which are those with $m_{a_1}$ close to $2m_B$ and $m_{h_1}\sim 90\text{gev}-100\text{gev}$.

Comments: 24 pages, 25 figures, paper updated to incorporate final ALEPH limits in Z+4\tau channel.