Invisible decays of Higgs and other mesons in models with singlet neutrinos in large extra dimensions

In light of current atmospheric neutrino oscillation data, we revisit the invisible decay of the standard model Higgs boson and other pseudoscalar mesons which can be enhanced because of large number of KK modes in models with right-handed singlet neutrinos in large extra dimensions. We find that the invisible decay rate of Higgs can be as large as H→bb̄ decay rate only for a very restricted region of parameter space. This parameter space is even further restricted if one demands that the dimensionless neutrino Yukawa coupling λ is O(1). We have also studied the scenarios where singlet neutrino propagate in a sub-space, which lowers the string scale M∗ and keeps neutrino Yukawa coupling O(1). We have also considered decays of other spin-0 mesons to νν̄ and found the rates to be too small for measurement.