12 research outputs found
Right-handed neutrino dark matter in the classically conformal U(1)' extended Standard Model
We consider the dark matter (DM) scenario in the context of the classically
conformal U(1)' extended standard model (SM), with three right-handed neutrinos
(RHNs) and the U(1)' Higgs field. The model is free from all the U(1)' gauge
and gravitational anomalies in the presence of the three RHNs. We introduce a
-parity in the model, under which an odd-parity is assigned to one RHN,
while all the other particles is assigned to be -even, and hence the
-odd RHN serves as a DM candidate. In this model, the U(1)' gauge symmetry
is radiatively broken through the Coleman-Weinberg mechanism, by which the
electroweak symmetry breaking is triggered. There are three free parameters in
our model, the U(1)' charge of the SM Higgs doublet (), the new U(1)'
gauge coupling (), and the U(1)' gauge boson () mass (), which
are severely constrained in order to solve the electroweak vacuum instability
problem, and satisfy the LHC Run-2 bounds from the search for boson
resonance. In addition to these constraints, we investigate the RHN DM physics.
Because of the nature of classical conformality, we find that a RHN DM pair
mainly annihilates into the SM particles through the boson exchange. This
is the so-called -portal DM scenario. Combining the electroweak vacuum
stability condition, the LHC Run-2 bounds, and the cosmological constraint from
the observed DM relic density, we find that all constrains complementarily work
to narrow down the allowed parameter regions, and, especially, exclude TeV. For the obtained allowed regions, we calculate the
spin-independent cross section of the RHN DM with nucleons. We find that the
resultant cross section well below the current experimental upper bounds.Comment: 29 pages, 1 table, and 16 figures, version accepted in Phys. Rev. D.
arXiv admin note: substantial text overlap with arXiv:1605.0115
Non-minimal quartic inflation in classically conformal U(1) extended Standard Model
We propose quartic inflation with non-minimal gravitational coupling in the
context of the classically conformal U(1)_X extension of the SM. In this model,
the U(1)_X gauge symmetry is radiatively broken through the Coleman-Weinberg
(CW) mechanism, by which the U(1)_X gauge boson (Z' boson) and the right-handed
neutrinos (RHNs) acquire their masses. We consider their masses in the range of
O(10 GeV)-O(10 TeV), which are accessible to high energy collider experiments.
The radiative U(1)_X gauge symmetry breaking also generates a negative mass
squared for the SM Higgs doublet, and the electroweak symmetry breaking occurs
subsequently. We identify the U(1)_X Higgs field with inflaton and calculate
the inflationary predictions. Due to the CW mechanism, the inflaton quartic
coupling during inflation, which determines the inflationary predictions, is
correlated to the U(1)_X gauge coupling. With this correlation, we investigate
complementarities between the inflationary predictions and the current
constraint from the Z' boson resonance search at the LHC Run-2 as well as the
prospect of the search for the Z' boson and the RHNs at the future collider
experiments. The radiative U(1)_X gauge symmetry breaking also generates a
negative mass squared for the SM Higgs doublet, and the electroweak symmetry
breaking occurs subsequently. We identify the U(1)_X Higgs field with inflaton
and calculate the inflationary predictions. Due to the Coleman-Weinberg
mechanism, the inflaton quartic coupling during inflation, which determines the
inflationary predictions, is correlated to the U(1)_X gauge coupling. With this
correlation, we investigate complementarities between the inflationary
predictions and the current constraint from the Z' boson resonance search at
the LHC Run-2 as well as the prospect of the search for the Z' boson and the
RHNs at the future collider experiments.Comment: 21 pages, 6 figures, accepted for publication in pr
High scale validity of the DFSZ axion model with precision
With the assumption of classical scale invariance at the Planck scale, the DFSZ axion model can generate the Higgs mass terms of the appropriate size through technically natural parameters and may be valid up to the Planck scale. We discuss the high scale validity of the Higgs sector, namely the absence of Landau poles and the vacuum stability. The Higgs sector is identical to that of the type-II two Higgs doublet model with a limited number of the Higgs quartic couplings. We utilize the state-of-the-art method to calculate vacuum decay rates and find that they are enhanced at most by 1010 compared with the tree level evaluation. We also discuss the constraints from flavor observables, perturbative unitarity, oblique parameters and collider searches. We find that the high scale validity tightly constrains the parameter region, but there is still a chance to observe at most about 10% deviation of the 125 GeV Higgs couplings to the fermions