17,799 research outputs found

    The minimal fermionic model of electroweak baryogenesis

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    We present the minimal model of electroweak baryogenesis induced by fermions. The model consists of an extension of the Standard Model with one electroweak singlet fermion and one pair of vector like doublet fermions with renormalizable couplings to the Higgs. A strong first order phase transition is radiatively induced by the singlet-doublet fermions, while the origin of the baryon asymmetry is due to asymmetric reflection of the same set of fermions on the expanding electroweak bubble wall. The singlet-doublet fermions are stabilized at the electroweak scale by chiral symmetries and the Higgs potential is stabilized by threshold corrections coming from a multi-TeV ultraviolet completion which does not play any significant role in the phase transition. We work in terms of background symmetry invariants and perform an analytic semiclassical calculation of the baryon asymmetry, showing that the model may effectively generate the observed baryon asymmetry for percent level values of the unique invariant CP violating phase of the singlet-doublet sector. We include a detailed study of electron electric dipole moment and electroweak precision limits, and for one typical benchmark scenario we also recast existing collider constraints, showing that the model is consistent with all current experimental data. We point out that fermion induced electroweak baryogenesis has irreducible phenomenology at the 13 TeV13 \, \textrm{TeV} LHC since the new fermions must be at the electroweak scale, have electroweak quantum numbers and couple strongly with the Higgs. The most promising searches involve topologies with multiple leptons and missing energy in the final state.Comment: 30 + 10 pages, 6 figure

    Electroweak baryogenesis in the Z3-invariant NMSSM

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    We calculate the baryon asymmetry of the Universe in the Z3-invariant Next-to-Minimal Supersymmetric Standard Model where the interactions of the singlino provide the necessary source of charge and parity violation. Using the closed time path formalism, we derive and solve transport equations for the cases where the singlet acquires a vacuum expectation value (VEV) before and during the electroweak phase transition. We perform a detailed scan to show how the baryon asymmetry varies throughout the relevant parameter space. Our results show that the case where the singlet acquires a VEV during the electroweak phase transition typically generates a larger baryon asymmetry, although we expect that the case where the singlet acquires a VEV first is far more common for any model in which parameters unify at a high scale. Finally, we examine the dependence of the baryon asymmetry on the three-body interactions involving gauge singlets.Comment: 24 pages, version submitted to the journa

    F(R)F(R) gravity in the early Universe: Electroweak phase transition and chameleon mechanism

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    It is widely believed that the screening mechanism is an essential feature for the modified gravity theory. Although this mechanism has been examined thoroughly in the past decade, their analyses are based on the classical configuration of the matter fields. In this paper, we demonstrate a new formulation of the chameleon mechanism in F(R)F(R) gravity theory, to shed light on quantum-field theoretical effects on the chameleon mechanism as well as the related scalaron physics, induced by the matter sector. We show a potential absence of the chameleon mechanism in the cosmic history based on a scale-invariant-extended scenario beyond the standard model of particle physics, in which a realistic electroweak phase transition, possibly yielding the right amount of baryon asymmetry of Universe today, simultaneously breaks the scale invariance in the early Universe. Remarkably enough, the matter sector contribution to the trace of energy-momentum tensor turns out to be on the same order of magnitude as that computed in the classical perfect-fluid approximation, even though the theory involves the nontrivial electroweak-phase transition environment. We also briefly discuss the oscillation of the scalaron field and indirect generation of non-tensorial gravitational waves induced by the electroweak phase transition.Comment: 17 pages, 4 figures, version accepted in Chinese Physics

    Gravitational waves from scale-invariant vector dark matter model: Probing below the neutrino-floor

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    We study the gravitational waves (GWs) spectrum produced during the electroweak phase transition in a scale-invariant extension of the Standard Model (SM), enlarged by a dark U(1)D U(1)_{D} gauge symmetry. This symmetry incorporates a vector dark matter (DM) candidate and a scalar field (scalon). Because of scale invariance, the model has only two independent parameters and for the parameter space constrained by DM relic density, strongly first-order electroweak phase transition can take place. In this model, for a narrow part of the parameter space, DM-nucleon cross section is below the neutrino-floor limit, and therefore, it cannot be probed by the future direct detection experiments. However, for a benchmark point form this narrow region, we show the amplitude and frequency of phase transition GW spectrum fall within the observational window of space-based GW detectors such as eLISA.Comment: 12 pages, 6 figures, references updated, version accepted for publication in The European Physical Journal

    Gravitational wave effects and phenomenology of a two-component dark matter model

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    We study an extension of the Standard Model (SM) which could have two candidates for dark matter (DM) including a Dirac fermion and a Vector Dark Matter (VDM) under new U(1)U(1) gauge group in the hidden sector. The model is classically scale invariant and the electroweak symmetry breaks because of the loop effects. We investigate the parameter space allowed by current experimental constraints and phenomenological bounds. We probe the parameter space of the model in the mass range 1<MV<50001< M_V<5000 GeV and 1<Mψ<50001<M_{\psi}<5000 GeV. It has been shown that there are many points in this mass range that are in agreement with all phenomenological constraints. The electroweak phase transition have been discussed and shown that there is region in the parameter space of the model consistent with DM relic density and direct detection constraints, while at the same time can lead to first order electroweak phase transition. The gravitational waves produced during the phase transition could be probed by future space-based interferometers such as LISA and BBO.Comment: 28 pages, 11 figure
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