Sphalerons in the standard model with a real Higgs singlet

Abstract:We investigate an extension of the standard model (SM) with a singlet fermionic dark matter (DM) particle which interacts with the SM sector through a real singlet scalar. The presence of a new scalar provides the possibility of generating a strongly first order phase transition needed for electroweak baryogenesis. Taking into account the latest Higgs search results at the LHC and the upper limits from the DM direct detection experiments especially that from the LUX experiment, and combining the constraints from the LEP experiment and the electroweak precision test, we explore the parameter space of this model which can lead to the strongly first order phase transition. Both the tree-and loop-level barriers are included in the calculations. We find that the allowed mass of the second Higgs particle is in the range ∼ 30-350 GeV. The allowed mixing angle α between the SM-like Higgs particle and the second Higgs particle is constrained to α 28 • . The DM particle mass is predicted to be in the range ∼15-350 GeV. The future XENON1T experiment can rule out a significant proportion of the parameter space of this model. The constraint can be relaxed only when the mass of the SM-like Higgs particle is degenerate with that of the second Higgs particle, or the mixing angle is small enough.

Section: Sphaleron Solution With Magnetic Momentmentioning

confidence: 99%

“…We adopt the ansatz for the fields from Refs. [88][89][90][91] The sphaleron energy can be minimized by the solving the variational field equations…”

Section: Sphaleron Solution With Magnetic Momentmentioning

confidence: 99%

Strongly first order phase transition in the singlet fermionic dark matter model after LUX

Zhou

2014

“…the energy of the sphaleron [7]. Such baryon number violation induced by the sphaleron is one of the essential ingredients of Electroweak Baryogenesis [8][9][10][11][12][13] and therefore it has been extensively studied not only in the SM [14][15][16][17][18][19][20][21][22][23][24] and but also in extended SM variants such as, SM with a singlet [25,26], two Higgs doublet model [27], Minimal Supersymmetric Standard Model [28], the next-to-Minimal Supersymmetric Standard Model [29] and 5-dimensional model [30].…”

Section: Introductionmentioning

confidence: 99%

Sphalerons and the electroweak phase transition in models with higher scalar representations

Ahriche

Chowdhury

Nasri

2014

In this work we investigate the sphaleron solution in a SU(2) × U(1) X gauge theory, which also encompasses the Standard Model, with higher scalar representation(s) (J (i) , X (i) ). We show that the field profiles describing the sphaleron in higher scalar multiplet, have similar trends like the doublet case with respect to the radial distance. We compute the sphaleron energy and find that it scales linearly with the vacuum expectation value of the scalar field and its slope depends on the representation. We also investigate the effect of U(1) gauge field and find that it is small for the physical value of the mixing angle, θ W and resembles the case for the doublet. For higher representations, we show that the criterion for strong first order phase transition, v c /T c > η, is relaxed with respect to the doublet case, i.e. η < 1.

Sphaleron in the Higgs Triplet Model

Hu,

Yu,

Zhou

2023

The Higgs triplet model (HTM) extends the Standard Model (SM) by one complex triplet scalar (also known as the type-II seesaw model), offering a simple and viable way to account for nonzero neutrino masses. On the other hand, the nontrivial couplings of the triplet to the gauge fields and to the SM Higgs field are expected to influence the topological vacuum structure of the SM, and consequently, the energy and the field configuration of the electroweak sphaleron. The sphaleron process plays a crucial role in dynamically generating the baryon asymmetry of the Universe. In this work, we study the vacuum structure of the gauge and Higgs fields and calculate the saddle-point sphaleron configuration in the HTM. The coupled nonlinear equations of motion of the sphaleron are solved using the spectral method. We find the inclusion of the triplet scalar could in principle significantly change the sphaleron energy compared with the SM. Nevertheless, at zero temperature, the current stringent experimental constraint on the vacuum expectation value of the triplet suppresses the difference. Interestingly, we find that there still exists some narrow parameter space where the sphaleron energy can be enhanced up to 30% compared with the SM case.