The second Kaluza-Klein neutral Higgs bosons in the minimal Universal Extra Dimension model

Understand

Loop-induced decay of a neutral Higgs boson into a pair of gluons or photons has great implications for the Higgs discovery at the LHC.

• If the Higgs boson is heavy with mass above $\sim 500\gev$, however, these radiative branching ratios are very suppressed in the standard model (SM), as the new decay channels are kinematically open.
• We note that these radiative decays can be sizable for the heavy CP-odd second Kaluza-Klein (KK) mode of the Higgs boson, $\chi^\tw$, in the minimal universal extra dimension model: highly degenerate mass spectrum of the theory prohibits kinematically the dominant KK-number-conserving decays into the first KK modes of the $W$, $Z$ and top quark.
• We find that the CP-even decay of $h^{(2)} \to g g$ is absent at one-loop level since $h^{(2)}$ couples with different mass eigenstates of $t_{1,2}^\on$ while a gluon does with the same mass eigenstates.