Naoyuki Haba

Vanishing Higgs potential at the Planck scale in a singlet extension of the standard model

We discuss the realization of a vanishing effective Higgs potential at the Planck scale, which is required by the multiple-point criticality principle (MPCP), in the standard model with singlet scalar dark matter and a right-handed neutrino. We find the scalar dark matter and the right-handed neutrino play crucial roles for realization of the MPCP, where a neutrino Yukawa becomes effective above the Majorana mass of the right-handed neutrino. Once the top mass is fixed, the MPCP at the (reduced) Planck scale and the suitable dark matter relic abundance determine the dark matter mass,

A new dynamics of electroweak symmetry breaking with classically scale invariance

m_S

Higgs inflation and Higgs portal dark matter with right-handed neutrinos

, and the Majorana mass of the right-handed neutrino,

Bosonic seesaw mechanism in a classically conformal extension of the Standard Model

M_R

Gauge coupling unification in a classically scale invariant model

, as

Multiple-point principle with a scalar singlet extension of the standard model

8.5~(8.0)\times10^2~{\rm GeV}\leq m_S\leq1.4~(1.2)\times10^3~{\rm GeV}

Vacuum stability and naturalness in type-II seesaw

and

Gravitational effects on vanishing Higgs potential at the Planck scale

6.3~(5.5)\times10^{13}~{\rm GeV}\leq M_R\leq1.6~(1.2)\times10^{14}~{\rm GeV}

Higgs Pair Production at the LHC and ILC from general potential

within current experimental values of the Higgs and top masses. This scenario is consistent with current dark matter direct search experiments, and will be checked by future experiments such as LUX with further exposure and/or the XENON1T.

A model realizing inverse seesaw and resonant leptogenesis

We propose a new dynamics of the electroweak symmetry breaking in a classically scale invariant version of the standard model. The scale invariance is broken by the condensations of additional fermions under a strong coupling dynamics. The electroweak symmetry breaking is triggered by negative mass squared of the elementary Higgs doublet, which is dynamically generated through the bosonic seesaw mechanism. We introduce a real pseudo-scalar singlet field interacting with additional fermions and Higgs doublet in order to avoid massless Nambu–Goldstone bosons from the chiral symmetry breaking in a strong coupling sector. We investigate the mass spectra and decay rates of these pseudo-Nambu–Goldstone bosons, and show they can decay fast enough without cosmological problems. We further show that our model can make the electroweak vacuum stable.