Exotic Decays Of A Heavy Neutral Higgs Through HZ/AZ Channel

Abstract: Models of electroweak symmetry breaking with extended Higgs sectors are theoretically well motivated. In this study, we focus on the Two Higgs Doublet Model with a low energy spectrum containing scalars $H$ and a pseudoscalar $A$. We study the decays $A\rightarrow HZ$ or $H\rightarrow AZ$, which could reach sizable branching fractions in certain parameter regions. With detailed collider analysis, we obtain model independent exclusion bounds as well as discovery reach at the 14 TeV LHC for the process: $gg\rightarrow A/H\rightarrow HZ/AZ$, looking at final states bbll, \tau\tau ll and ZZZ(4l2j) for l =e,\mu. We further interpret these bounds in the context of the Type II Two Higgs Doublet Model, considering three different classes of processes: $A\rightarrow h^0Z$, $A\rightarrow H^0Z$, and $H^0 \rightarrow AZ$, in which $h^0$ and $H^0$ are the light and heavy CP-even Higgses respectively. For 100 fb$^{-1}$ integrated luminosity at the 14 TeV LHC, we find that for parent particle mass around 300-400 GeV, $A\rightarrow h^0Z$ has the greatest reach when $H^0$ is interpreted as the 126 GeV Higgs: most regions in the tan\beta-sin(\beta-\alpha) parameter space can be covered by exclusion and discovery. For 126 GeV $h^0$, only relatively small tan\beta<10 (5) can be reached by exclusion (discovery). For $A\rightarrow H^0Z$, the reach is typically restricted to sin$(\beta-\alpha)\sim\pm 1$ with tan\beta <10 in bbll and \tau\tau ll channels. The ZZZ (4l2j) channel, on the other hand, covers a wide range of 0.3<|sin(\beta-\alpha)|<1 for tan\beta<4. $H^0\rightarrow AZ$ typically favors negative values of sin(\beta-\alpha), with exclusion/discovery reach possibly extending to all values of tan\beta. A study of exotic decays of extra Higgses would extend the reach at the LHC and provides nice complementarity to conventional Higgs search channels.