Constraints on electroweak baryogenesis in models involving an extended Higgs sector
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EMENTARY PARTICLES AND FIELDS Theory
Constraints on Electroweak Baryogenesis in Models Involving an Extended Higgs Sector M. V. Dolgopolov* and E. N. Rykova** Samara State University, ul. Akademika Pavlova 1, Samara, 443011 Russia Received March 21, 2008
Abstract—Consequences for electroweak baryogenesis within models featuring an extended Higgs sector are analyzed. The phenomenology of extensions of the scalar sector in the Standard Model and its significance for the electroweak phase transition are studied. Conditions for the effective potential of the two-doublet model that lead to a strong first-order phase transition necessary for generating the observed baryon–antibaryon asymmetry are determined. PACS numbers: 11.30.Fs, 12.60.Fr DOI: 10.1134/S1063778809010207
1. INTRODUCTION The emergence of a baryon–antibaryon asymmetry or of a dynamical generation of a nonzero baryon charge in the Universe is referred to as baryogenesis. Within a CP T -invariant theory, baryogenesis must be validated in such a way as to explain the observed asymmetry nB − nB¯ ∼ 6 × 10−10 , (1) η= nγ where nB is the baryon concentration. This value was obtained independently from an analysis of data on cosmic microwave background radiation (CMBR) and from an analysis of data on primordial nucleosynthesis also known as Big Bang nucleosynthesis (BBN) [1]. The explanation for the baryon–antibaryon asymmetry of the Universe hinges on fulfillment of the conditions proposed by Sakharov [2]: (i) baryon-number nonconservation, (ii) C and CP violation, and (iii) the presence of a deviation from a thermodynamic equilibrium at the stage of baryogenesis. These conditions may be realized in the electroweak phase transition [3, 4]. The majority of scenarios for the generation of a baryon–antibaryon asymmetry requires the presence of a strong first-order phase transition; otherwise, the baryon–antibaryon asymmetry generated in the electroweak phase transition disappears in the subsequent evolution. Cosmological bubbles are used to * **
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describe such processes [5, 6]. In all of these scenarios, a baryon–antibaryon asymmetry appears in the vicinity of the walls of scalar-field (ϕ) bubbles. A phase transition occurs at a temperature below the critical temperature owing to the tunneling of real-vacuum bubbles, which grow and fill the Universe [6, 7]. In the present study, we consider electroweak baryogenesis in the two-doublet model, employing the finite-temperature effective potential at the one-loop level. In relation to the Standard Model (SM), which involves one Higgs boson, the twodoublet model contains two additional neutral and two charged Higgs bosons. If these states are rather strongly bound, then their finite-temperature corrections lead to a strong first-order phase transition. In this case, the mass of the light Higgs boson may amount to 170 GeV, while the masses of extra Higgs bosons must be higher than 300 GeV, depending on model parameters. It is shown that, within the twodoublet model, t
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