Detecting an invisible Higgs boson at Fermilab Tevatron and CERN LHC
  In this paper, we study the observability of an invisible Higgs boson at Fermilab Tevatron and CERN LHC through the production channel $ q \bar{q} \to Z H \to \ell^+\ell^-+ \ptmiss $, where $\ptmiss$ is reconstructed from the $\ell^+\ell^-$ with $\ell=e$ or $\mu$. A new strategy is proposed to eliminate the largest irreducible background, namely $ q \bar{q} \to Z(\to \ell^+\ell^-) Z(\to \nu \bar\nu)$. This strategy utilizes the precise measurements of $ q \bar{q} \to Z(\to \ell^+\ell^-) Z(\to \ell^+\ell^-)$. For $m_H=120$ GeV and with luminosity $30 fb^{-1}$ at Tevatron, a $5\sigma$ observation of the invisible Higgs boson is possible. For $m_H=114 \sim 140$ GeV with only $10 fb^{-1}$ luminosity at LHC, a discovery signal over $5\sigma$ can be achieved. 
Shou-hua Zhu