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

TL;DR

This paper constrains light CP-odd Higgs bosons in the NMSSM using BaBar and ALEPH data, narrowing down viable scenarios and highlighting the impact of recent experimental limits on theoretical models.

Contribution

It provides new experimental constraints on light CP-odd Higgs bosons within the NMSSM and assesses their implications for ideal Higgs scenarios.

Findings

Most scenarios with $m_{a_1}<2m_\tau$ are eliminated.

Surviving scenarios have $m_{a_1}>7.5$ GeV, aligning with theoretical preferences.

ALEPH limits restrict parameter space for certain $m_{h_1}$ and $m_{a_1}$ values.

Abstract

Recent BaBar limits on $\br(\Upsilon(3S)\to \gam a\to \gam \tau^+\tau^-)$ and $\br(\Upsilon(3S)\to \gam a\to \gam \mu^+\mu^-)$ provide increased constraints on the $a b\anti b$ coupling of a CP-odd Higgs boson, $a$, with $m_a<M_{\Upsilon(3S)}$. We extract these limits from the BaBar data and compare to the limits previously obtained using other data sets, especially the CLEO-III $\br(\Upsilon(1S)\to \gam\to\tau^+\tau^-)$ 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 $105\gev$ (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, $h_1\to a_1a_1$, with $m_{a_1}<2m_B$. Most such scenarios with $m_{a_1}<2m_\tau$ are eliminated, but the bulk of the $m_{a_1}>7.5\gev$ scenarios, which are theoretically the most favored, survive. We also outline the impact of the new ALEPH LEP results in the $\epem\to Z+4\tau$ channel. For $\tan\beta\geq 3$, only NMSSM ideal Higgs scenarios with $m_{h_1}\gsim 98\gev$ and $m_{a_1}$ close to $2m_B $ satisfy the ALEPH limits. For $\tan\beta\lsim 2$, 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 $m_{h_1}\sim 90\gev-100\gev$.