28 research outputs found
Discriminative phenomenological features of scale invariant models for electroweak symmetry breaking
Classical scale invariance (CSI) may be one of the solutions for the
hierarchy problem. Realistic models for electroweak symmetry breaking based on
CSI require extended scalar sectors without mass terms, and the electroweak
symmetry is broken dynamically at the quantum level by the Coleman-Weinberg
mechanism. We discuss discriminative features of these models. First, using the
experimental value of the mass of the discovered Higgs boson , we
obtain an upper bound on the mass of the lightest additional scalar boson (~543
GeV), which does not depend on its isospin and hypercharge. Second, a
discriminative prediction on the Higgs-photon-photon coupling is given as a
function of the number of charged scalar bosons, by which we can narrow down
possible models using current and future data for the di-photon decay of
. Finally, for the triple Higgs boson coupling a large deviation (~ +70
%) from the SM prediction is universally predicted, which is independent of
masses, quantum numbers and even the number of additional scalars. These models
based on CSI can be well tested at LHC Run II and at future lepton colliders.Comment: 4 pages, 1 figure, references added, text slightly modifie
SMEFT effects on gravitational wave spectrum from electroweak phase transition
Future gravitational wave observations are potentially sensitive to new
physics corrections to the Higgs potential once the first-order electroweak
phase transition arises. We study the SMEFT dimension-six operator effects on
the Higgs potential, where three types of effects are taken into account: (i)
SMEFT tree level effect on operator, (ii) SMEFT tree level effect
on the wave function renormalization of the Higgs field, and (iii) SMEFT
top-quark one-loop level effect. The sensitivity of future gravitational wave
observations to these effects is numerically calculated by performing a Fisher
matrix analysis. We find that the future gravitational wave observations can be
sensitive to (ii) and (iii) once the first-order electroweak phase transition
arises from (i). The dimension-eight operator effects on the
first-order electroweak phase transition are also discussed. The sensitivities
of the future gravitational wave observations are also compared with those of
future collider experiments.Comment: 32 pages, 16 figures; section 6 was added for more explanation
Gravitational Waves from Phase Transitions in Models with Charged Singlets
We investigate the effect of extra singlets on the electroweak phase
transition (EWPT) strength and the spectrum of the corresponding gravitational
waves (GWs). We consider here the standard model (SM) extended with a singlet
scalar with multiplicity N coupled to the SM Higgs doublet. After imposing all
the theoretical and experimental constraints and defining the region where the
EWPT is strongly first order, we obtain the region in which the GWs spectrum
can be reached by different future experiments such as LISA and DECIGO.Comment: 11 pages, 4 figures, published version matche
Fingerprinting models of first-order phase transitions by the synergy between collider and gravitational-wave experiments
We investigate the sensitivity of future space-based interferometers such as
LISA and DECIGO to the parameters of new particle physics models which drive a
first-order phase transition in the early Universe. We first perform a Fisher
matrix analysis on the quantities characterizing the gravitational wave
spectrum resulting from the phase transition, such as the peak frequency and
amplitude. We next perform a Fisher analysis for the quantities which determine
the properties of the phase transition, such as the latent heat and the time
dependence of the bubble nucleation rate. Since these quantities are determined
by the model parameters of the new physics, we can estimate the expected
sensitivities to such parameters. We illustrate this point by taking three new
physics models for example: (1) models with additional isospin singlet scalars
(2) a model with an extra real Higgs singlet, and (3) a classically conformal
model. We find that future gravitational wave observations play
complementary roles to future collider experiments in pinning down the
parameters of new physics models driving a first-order phase transition.Comment: 64 pages, 35 figure
Gravitational waves from first order electroweak phase transition in models with the gauge symmetry
We consider a standard model extension equipped with a dark sector where the
Abelian gauge symmetry is spontaneously broken by the dark Higgs
mechanism. In this framework, we investigate patterns of the electroweak phase
transition as well as those of the dark phase transition, and examine
detectability of gravitational waves (GWs) generated by such strongly first
order phase transition. It is pointed out that the collider bounds on the
properties of the discovered Higgs boson exclude a part of parameter space that
could otherwise generate detectable GWs. After imposing various constraints on
this model, it is shown that GWs produced by multi-step phase transitions are
detectable at future space-based interferometers, such as LISA and DECIGO, if
the dark photon is heavier than 25 GeV. Furthermore, we discuss the
complementarity of dark photon searches or dark matter searches with the GW
observations in these models with the dark gauge symmetry.Comment: 23 pages, 22 figures, version published in Journal of High Energy
Physic
Gravitational waves and Higgs boson couplings for exploring first order phase transition in the model with a singlet scalar field
We calculate the spectrum of gravitational waves originated from strongly first order electroweak phase transition in the extended Higgs model with a real singlet scalar field. In order to calculate the bubble nucleation rate, we perform a two-field analysis and evaluate bounce solutions connecting the true and the false vacua using the one-loop effective potential at finite temperatures. Imposing the Sakharov condition of the departure from thermal equilibrium for baryogenesis, we survey allowed regions of parameters of the model. We then investigate the gravitational waves produced at electroweak bubble collisions in the early Universe, such as the sound wave, the bubble wall collision and the plasma turbulence. We find that the strength at the peak frequency can be large enough to be detected at future space-based gravitational interferometers such as eLISA, DECIGO and BBO. Predicted deviations in the various Higgs boson couplings are also evaluated at the zero temperature, and are shown to be large enough too. Therefore, in this model strongly first order electroweak phase transition can be tested by the combination of the precision study of various Higgs boson couplings at the LHC, the measurement of the triple Higgs boson coupling at future lepton colliders and the shape of the spectrum of gravitational wave detectable at future gravitational interferometers