Speaker
Description
Searches are being carried out at the Large Hadron Collider (LHC) for the decay of the CP-odd scalar $(A^{0})$ in Two-Higgs-Doublet Models (2HDMs) with Natural Flavour Conservation (NFC) in the channel $A^{0}\rightarrow h^{0}Z^{*}$ (with $m_{h^{0}}=125 GeV$ and Z on-shell). In the absence of any signal, limits on the parameter space of $[tan\beta , cos(\beta -\alpha ), m_{A^{0}}]$in each 2HDM are derived form $m_{A^{0}}> 225 GeV$. In this work we consider the scenario of inverted hierarchy with $m _{h^{0}}< 125 GeV$ and $m _{H^{0}}=125 GeV$ in which the decay $A^{0}\rightarrow h^{0}Z^{*}$ (i.e. including the case of an off-shell Z) can have a large branching ratio in the 2HDM (Type I) for $m_{A^{0}}< 225 GeV$. We calculate the signal cross section $\sigma (gg\to A^{0})\times BR(A^{0}\to h^{0}Z^{()*)})\times BR(h^{0}\to b \bar{b} )$ in the 2HDM (Type I) with NFC and compare its magnitude with the cross section for the case of normal hierarchy ($m _{h^{0}}=125 GeV$) that is currently being searched for at the LHC. For the experimentally unexplored region $m_{A^{0}}< 225 GeV$ it is shown that the above cross section for signal events in the scenario of inverted hierarchy can be of the order of a few picobarns. Such sizeable cross sections are several orders of magnitude larger than the cross sections for the case of normal hierarchy, thus motivating an extension of the ongoing searches for $A^{0}\rightarrow h^{0}Z^{*}$ to probe the scenario of inverted hierarchy.
