Minimal Majoronic Dark Radiation and Dark Matter Model and its Phenomenology

From Lecospa
Jump to: navigation, search

We study the simplest singlet Majoron model for the dark radiation and dark matter and its 1-loop RGE running. We found that a smaller effective number of neutrinos $\triangle N_{eff}\sim 0.05$ is preferred. Moreover, a heavy scalar dark matter, $\rho$, of mass $1.5-4$ TeV is required by the stability of the scalar potential and an operational type-I see-saw mechanism for neutrino masses. A neutral scalar, $S$, of mass in the $10-100$ GeV range and its mixing with the standard model Higgs as large as $0.1$ is also predicted. The dominant decay modes are $S$ into $b\bar{b}$ and/or a pair of Majoron. A sensitive search will come from rare $Z$ decays via the chain $Z\ra S+ f\bar{f}$, where $f$ is a Standard Model fermion, followed by $S$ into a pair of Majoron and/or b-quarks. The interesting consequences of dark matter bound state due to the sizable $S\rho \rho$-coupling are discussed as well. In particular, shower-like events with an apparent neutrino energy at $M_\rho$ could contribute to the observed effective neutrino flux in underground neutrino detectors such as IceCube.