Abstract
We search for a light Higgs boson (A^{0}) decaying into a τ^{+}τ^{-} or μ^{+}μ^{-} pair in the radiative decays of ϒ(1S). The production of ϒ(1S) mesons is tagged by ϒ(2S)→π^{+}π^{-}ϒ(1S) transitions, using 158×10^{6} ϒ(2S) events accumulated with the Belle detector at the KEKB asymmetric energy electron-positron collider. No significant A^{0} signals in the mass range from the τ^{+}τ^{-} or μ^{+}μ^{-} threshold to 9.2 GeV/c^{2} are observed. We set the upper limits at 90% credibility level (C.L.) on the product branching fractions for ϒ(1S)→γA^{0} and A^{0}→τ^{+}τ^{-} varying from 3.8×10^{-6} to 1.5×10^{-4}. Our results represent an approximately twofold improvement on the current world best upper limits for the ϒ(1S)→γA^{0}(→τ^{+}τ^{-}) production. For A^{0}→μ^{+}μ^{-}, the upper limits on the product branching fractions for ϒ(1S)→γA^{0} and A^{0}→μ^{+}μ^{-} are at the same level as the world average limits, and vary from 3.1×10^{-7} to 1.6×10^{-5}. The upper limits at 90%credibility level on the Yukawa coupling f_{ϒ(1S)} and mixing angle sinθ_{A^{0}} are also given.
Highlights
We search for a light Higgs boson (A0) decaying into a τþτ− or μþμ− pair in the radiative decays of Υð1SÞ
We set the upper limits at 90% credibility level (C.L.) on the product branching fractions for Υð1SÞ → γA0 and A0 → τþτ− varying from 3.8 × 10−6 to 1.5 × 10−4
In 2012, the last missing standard model (SM) particle, a Higgs boson, was discovered by ATLAS and CMS [1,2], demonstrating that the Higgs mechanism would break the electroweak symmetry and give rise to the masses of W and Z bosons as well as quarks and leptons [3,4]. Besides this massive Higgs boson, three CP-even, two CP-odd, and two charged Higgs bosons are predicted by the next-to minimal supersymmetric standard model (NMSSM) [5–9]
Summary
We search for a light Higgs boson (A0) decaying into a τþτ− or μþμ− pair in the radiative decays of Υð1SÞ. No significant A0 signals in the mass range from the τþτ− or μþμ− threshold to 9.2 GeV=c2 are observed.
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