79 research outputs found

    Gravitational waves from the first order electroweak phase transition in the Z3Z_3 symmetric singlet scalar model

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    Among various scenarios of baryon asymmetry of the Universe, electroweak baryogenesis is directly connected with physics of the Higgs sector. We discuss spectra of gravitational waves which are originated by the strongly first order phase transition at the electroweak symmetry breaking, which is required for a successful scenario of electroweak baryogenesis. In the Z3Z_3 symmetric singlet scalar model, the significant gravitational waves are caused by the multi-step phase transition. We show that the model can be tested by measuring the characteristic spectra of the gravitational waves at future interferometers such as LISA and DECIGO.Comment: 5 pages, 9 figures, contribution to the proceedings of Joint Conference of ICGAC-XIII and IK15, Korea, 3--7 July 2017, based on arXiv:1706.09721 [hep-ph

    Higgs inflation in a radiative seesaw model

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    We investigate a simple model to explain inflation, neutrino masses and dark matter simultaneously. This is based on the so-called radiative seesaw model proposed by Ma in order to explain neutrino masses and dark matter by introducing a Z2Z_2-odd isospin doublet scalar field and Z2Z_2-odd right-handed neutrinos. We study the possibility that the Higgs boson as well as neutral components of the Z2Z_2-odd scalar doublet field can satisfy conditions from slow-roll inflation and vacuum stability up to the inflation scale. We find that a part of parameter regions where these scalar fields can play a role of an inflaton is compatible with the current data from neutrino experiments and those of the dark matter abundance as well as the direct search results. A phenomenological consequence of this scenario results in a specific mass spectrum of scalar bosons, which can be tested at the LHC, the International Linear Collider and the Compact Linear Collider.Comment: 18 pages, 3 figure

    Loop Suppression of Dirac Neutrino Mass in the Neutrinophilic Two Higgs Doublet Model

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    We extend the scalar sector of the neutrinophilic two Higgs doublet model, where small masses of Dirac neutrinos are obtained via a small vacuum expectation value v_nu of the neutrinophilic SU(2)_L-doublet scalar field which has a Yukawa interaction with only right-handed neutrinos. A global U(1)_X symmetry is used for the neutrinophilic nature of the second SU(2)_L-doublet scalar field and also for eliminating Majorana mass terms of neutrinos. By virtue of an appropriate assignment of the U(1)_X-charges to new particles, our model has an unbroken Z_2 symmetry, under which the lightest Z_2-odd scalar boson can be a dark matter candidate. In our model, v_nu is generated by the one-loop diagram to which Z_2-odd particles contribute. We briefly discuss a possible signature of our model at the LHC.Comment: 15 pages, 2 figures, published in Physics Letters

    Strong First Order EWPT and Strong Gravitational Waves in Z3Z_3-symmetric Singlet Scalar Extension

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    The nature of electroweak (EW) phase transition (PT) is of great importance. It may give a clue to the origin of baryon asymmetry if EWPT is strong first order. Although it is second order within the standard model (SM), a great many extensions of the SM are capable of altering the nature. Thus, gravitational wave (GW), which is supposed to be relics of strong first order PT, is a good complementary probe to new physics beyond SM (BSM). We in this paper elaborate the patterns of strong first order EWPT in the next to simplest extension to the SM Higgs sector, by introducing a Z3Z_3-symmetric singlet scalar. We find that, in the Z3Z_3-symmetric limit, the tree level barrier could lead to strong first order EWPT either via three or two-step PT. Moreover, they could produce two sources of GW, despite of the undetectability from the first-step strong first order PT for the near future GW experiments. But the other source with significant supercooling which then gives rise to α∼O(0.1)\alpha\sim{\cal O}(0.1) almost can be wholly covered by future space-based GW interferometers such as eLISA, DECIGO and BBO.Comment: references adde
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