A
bstract
We consider a simple extension of the standard model with a singlet fermionic dark matter. Its thermal relic density can be easily accommodated by a real singlet scalar messenger that mixes ...with the standard model Higgs boson. The model can change significantly the Higgs signals at the LHC via sizable invisible decays of two Higgs-like scalar bosons. After imposing the constraints from the electroweak precision tests, colliders and dark matter search experiments, one concludes that two or one or none of the two Higgs bosons, depending on the mass relations among two scalar bosons and the dark matter fermion and their couplings. In particular, if a standard model Higgs-like scalar boson is discovered around 120-125 GeV region at the LHC, it would be almost impossible to find the second Higgs-like boson since it is mostly a singlet scalar, whether it is heavier or lighter. This model can be further tested by direct dark matter search experiments.
We show that, if they exist, lepton number asymmetries (
L
α
) of neutrino flavors should be distinguished from the ones (
L
i
) of mass eigenstates, since Big Bang Nucleosynthesis (BBN) bounds on ...the flavor eigenstates cannot be directly applied to the mass eigenstates. Similarly, Cosmic Microwave Background (CMB) constraints on the mass eigenstates do not directly constrain flavor asymmetries. Due to the difference of mass and flavor eigenstates, the cosmological constraint on the asymmetries of neutrino flavors can be much stronger than the conventional expectation, but they are not uniquely determined unless at least the asymmetry of the heaviest neutrino is well constrained. The cosmological constraint on
L
i
for a specific case is presented as an illustration.
We investigate the gravitational wave background from a first order phase transition in a matter-dominated universe, and show that it has a unique feature from which important information about the ...properties of the phase transition and thermal history of the universe can be easily extracted. Also, we discuss the inverse problem of such a gravitational wave background in view of the degeneracy among macroscopic parameters governing the signal.
We explore the gravitational wave spectrum generated by string-wall structures in an SO(10) (Spin(10)) based scenario of pseudo-Goldstone boson dark matter (pGDM) particle. This dark matter candidate ...is a linear combination of the Standard Model (SM) singlets present in the 126 and 16 dimensional Higgs fields. The Higgs 126-plet vacuum expectation value (VEV) 〈126H〉 leaves unbroken the Z2 subgroup of Z4, the center of SO(10). Among other things, this yields topologically stable cosmic strings with a string tension μ∼〈126H〉2. The subsequent (spontaneous) breaking of Z2 at a significantly lower scale by the 16-plet VEV 〈16H〉 leads to the appearance of domain walls bounded by the strings produced earlier. We display the gravitational wave spectrum for Gμ values varying between 10−15 and 10−9 (〈126H〉∼1011 - 1014 GeV), and 〈16H〉∼0.1 - 102 TeV range (G denotes Newton's constant.) These predictions can be tested, as we show, by a variety of (proposed) experiments including LISA, ET, CE and others.
Spontaneous baryogenesis in spiral inflation Barenboim, Gabriela; Park, Wan-Il
The European physical journal. C, Particles and fields,
06/2019, Letnik:
79, Številka:
6
Journal Article
Recenzirano
Odprti dostop
We examined the possibility of spontaneous baryogenesis driven by the inflaton in the scenario of
spiral inflation
, and found the parametric dependence of the late-time baryon number asymmetry. As a ...result, it is shown that, depending on the effective coupling of baryon/lepton number violating operators, it is possible to obtain the right amount of asymmetry even in the presence of a matter-domination era as long as such era is relatively short. In a part of the parameter space, the required expansion rate during inflation is close to the current upper-bound, and hence can be probed in the near future experiments.
Direct detection of and LHC search for the singlet fermion dark matter (SFDM) model with Higgs portal interaction are considered in a renormalizable model where the full Standard Model (SM) gauge ...symmetry is imposed by introducing a singlet scalar messenger. In this model, direct detection is described by an effective operator mqq¯qχ¯χ as usual, but the full amplitude for monojet + E̸T involves two intermediate scalar propagators, which cannot be seen within the effective field theory (EFT) or in the simplified model without the full SM gauge symmetry. We derive the collider bounds from the ATLAS monojet + E̸T as well as the CMS tt¯+E̸T data, finding out that the bounds and the interpretation of the results are completely different from those obtained within the EFT or simplified models. It is pointed out that it is important to respect unitarity, renormalizability and local gauge invariance of the SM.
Conformal portal to dark matter Kaneta, Kunio; Ko, Pyungwon; Park, Wan-Il
Physical review. D,
10/2021, Letnik:
104, Številka:
7
Journal Article
Recenzirano
Odprti dostop
We propose a new portal coupling to dark matter by taking advantage of the nonminimally coupled portal sector to the Ricci scalar. Such a portal sector conformally induces couplings to the trace of ...the energy-momentum tensor of matters including highly secluded dark matter particles. The portal coupling is so feeble that dark matter is produced by freeze-in processes of scatterings and/or the decay of the mediator. We consider two concrete realizations of the portal: conformally induced Higgs portal and conformally induced mediator portal. The former case is compatible with the Higgs inflation, while the latter case can be tested by dark matter direct detection experiments.
Higgs portal vector dark matter: revisited Baek, Seungwon; Ko, P.; Park, Wan-Il ...
The journal of high energy physics,
05/2013, Letnik:
2013, Številka:
5
Journal Article
Recenzirano
Odprti dostop
A
bstract
We revisit the Higgs portal vector dark matter model including a hidden sector Higgs field that generates the mass of the vector dark matter. The model becomes renormalizable and has two ...scalar bosons, the mixtures of the standard model (SM) Higgs and the hidden sector Higgs bosons. The strong bound from direct detection such as XENON100 is evaded due to the cancellation mechanism between the contributions from two scalar bosons. As a result, the model becomes still viable in large range of dark matter mass, contrary to some claims in the literature. The Higgs properties are also affected, the signal strengths for the Higgs boson search being universally suppressed relative to the SM value, which could be tested at the LHC in the future.
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