Unique Higgs boson signature at colliders
  The HyperCP collaboration has observed three events for the decay $\Sigma^+ \to p \mu^+ \mu^-$. The three events may be interpreted as a new narrow-width CP-odd scalar $a$ with the mass $214.3 \pm 0.5$ MeV. Here $a$ decays dominantly into di-muon ($\mu^+\mu^-$). As the consequence of tiny mass difference between $m_a$ and 2$m_\mu$ ($2 m_{\mu} \approx$ 211.3 MeV), di-muon will be boosted to almost the same direction at colliders. Such kind of di-muon events have been overlooked in the past experiments. Provided that the precision data preferred light SM-like Higgs boson $h$ decays dominantly into $a a$ other than into $b\bar b$, in order to be consistent with null Higgs boson search at LEP, the $h\to aa \to 4\mu$ ($2\mu^+ 2\mu^-$) will be the unique Higgs boson signature which has not been noticed before. The SM-like Higgs boson may hide itself from the usual analysis of LEP and Tevatron experiments, which should be reanalyzed in the light of new theoretical and experimental developments. In this paper, we also investigate this unique Higgs boson signature at colliders and conclude that the SM-like Higgs boson could be discovered with rather low integrated luminosity, provided that the $h\to 4\mu$ reconstruction efficiency is not extremely low. It is not impossible that such kind of unique Higgs boson $4\mu$ events are now lurking in the existing LEP and/or Tevatron data. 
Peng-fei Yin and Shou-hua Zhu (Peking University)