Electroweak interaction

About: Electroweak interaction is a research topic. Over the lifetime, 16333 publications have been published within this topic receiving 468927 citations. The topic is also known as: electroweak force.

Nonlocal electroweak baryogenesis. I. Thin wall regime.

Abstract: We investigate ``nonlocal'' schemes for baryogenesis at a first-order electroweak phase transition, in which the effects of a CP-violating condensate on the bubble wall propagate into the unbroken phase where the sphaleron rate is unsuppressed. Such a condensate exists in multi-Higgs-boson extensions of the standard model, and may exist due to an instability in the minimal standard model. In this paper we first discuss the general problem of determining the perturbations induced by a CP-violating condensate, distinguishing two regimes (quantum and classical). We then give an analytic treatment of quantum-mechanical reflection in the thin wall regime, in which interactions with the plasma can be neglected as a particle propagates across the wall. We focus on leptons because of their much weaker coupling to the plasma. We argue that they are likely to be accurately described by this calculation, but quarks are not. The relative magnitude of the baryon asymmetry produced for different fermions depends on their relative Yukawa couplings (not their zero temperature masses), their transport properties, and their interactions. We calculate the baryon asymmetry for various parameter ranges and conclude that asymmetries comparable with observations can be generated. \textcopyright{} 1996 The American Physical Society.

Dark matter and a new gauge boson through kinetic mixing

Abstract: We consider a hidden sector model of dark matter which is charged under a hidden U(1) X gauge symmetry. Kinetic mixing of U(1) X with the Standard Model hypercharge U(1) Y is allowed to provide communication between the hidden sector and the Standard Model sector. We present various limits on the kinetic mixing parameter and the hidden gauge coupling constant coming from various low energy observables, electroweak precision tests, and the right thermal relic density of the dark matter. Saturating these constraints, we show that the spin-independent elastic cross section of the dark matter off nucleons is mostly below the current experimental limits, but within the future sensitivity. Finally, we analyze the prospect of observing the hidden gauge boson through its dimuon decay channel at hadron colliders.

A Model of Lepton Masses from a Warped Extra Dimension

Abstract: In order to explain the non-hierarchical neutrino mixing angles and the absence of lepton flavor violating processes in the context of warped extra dimensions one needs to introduce bulk flavor symmetries. We present a simple model of lepton masses and mixings in RS models based on the A4 non-abelian discrete symmetry. The virtues of this choice are: (i) the natural appearance of the tri-bimaximal mixing pattern; (ii) the complete absence of tree-level flavor violations in the neutral sector; (iii) the absence of flavor gauge bosons; (iv) the hierarchies in the charged lepton masses are explained via wave-function overlaps. We present the minimal field content and symmetry breaking pattern necessary to obtain a successful model of this type. The bounds from electroweak precision measurements allow the KK mass scale to be as low as 3 TeV. Tree-level lepton flavor violation is absent in this model, while the loop induced mu -> e gamma branching fraction is safely below the experimental bound.

Higgs singlet extension parameter space in the light of the LHC discovery

Abstract: In this article we propose an overview on the current theoretical and experimental limits on a Higgs singlet extension of the Standard Model (SM). We assume that the boson which has recently been observed by the LHC experiments is the lightest Higgs boson of such a model, while for the second Higgs boson we consider a mass range of $600\text{ }\text{ }\mathrm{GeV}\ensuremath{\le}{m}_{H}\ensuremath{\le}1\text{ }\text{ }\mathrm{TeV}$, where our model directly corresponds to a benchmark scenario of the heavy Higgs working group. In this light, we study the impact of perturbative unitarity limits, renormalization group equations analysis, and experimental constraints (electroweak precision tests, measurements of the observed light Higgs coupling strength at the Large Hadron Collider). We show that, in the case of no additional hidden sector contributions, the largest constraints for higher Higgs masses stem from the assumption of perturbativity as well as vacuum stability for scales of the order of the SM metastability scale, and that the allowed mixing range is severely restricted. We discuss implications for current LHC searches in the singlet extension, especially the expected suppression factors for SM-like decays of the heavy Higgs. We present these results in terms of a global scaling factor $\ensuremath{\kappa}$ as well as the total width $\ensuremath{\Gamma}$ of the new scalar.

Resonant relaxation in electroweak baryogenesis

Abstract: We compute the leading, chiral charge-changing relaxation term in the quantum transport equations that govern electroweak baryogenesis using the closed time path formulation of nonequilibrium quantum field theory. We show that the relaxation transport coefficients may be resonantly enhanced under appropriate conditions on electroweak model parameters and that such enhancements can mitigate the impact of similar enhancements in the CP-violating source terms. We also develop a power counting in the time and energy scales entering electroweak baryogenesis and include effects through second order in ratios epsilon of the small and large scales. We illustrate the implications of the resonantly enhanced [script O](epsilon 2) terms using the Minimal Supersymmetric Standard Model, focusing on the interplay between the requirements of baryogenesis and constraints obtained from collider studies, precision electroweak data, and electric dipole moment searches.