On the Potential of Leptonic Minimal Flavour Violation

Minimal Flavour Violation can be realized in several ways in the lepton sector due to the possibility of Majorana neutrino mass terms. We derive the scalar potential for the fields whose background values are the Yukawa couplings, for the simplest See-Saw model with just two right-handed neutrinos, and explore its minima. The Majorana character plays a distinctive role: the minimum of the potential allows for large mixing angles -in contrast to the simplest quark case- and predicts a maximal Majorana phase. This points in turn to a strong correlation between neutrino mass hierarchy and mixing pattern.Comment: 6 pages; version published on Physics Letters

Flavor constraints on electroweak ALP couplings

We explore the signals of axion-like particles (ALPs) in flavor-changing neutral current (FCNC) processes. The most general effective linear Lagrangian for ALP couplings to the electroweak bosonic sector is considered, and its contribution to FCNC decays is computed up to one-loop order. The interplay between the different couplings opens new territory for experimental exploration, as analyzed here in the ALP mass range $0<m_a \lesssim 5$ GeV. When kinematically allowed, $K\to \pi \nu \bar{\nu}$ decays provide the most stringent constraints for channels with invisible final states, while $B$-meson decays are more constraining for visible decay channels, such as displaced vertices in $B\to K^{(\ast)} \mu^+ \mu^-$ data. The complementarity with collider constraints is discussed as well.Comment: 12 pages, 6 figure

The Axion and the Goldstone Higgs

We consider the renormalizable $SO(5)/SO(4)$ $\sigma$-model, in which the Higgs particle has a pseudo-Nambu-Goldstone boson character, and explore what the minimal field extension required to implement the Peccei-Quinn symmetry (PQ) is, within the partial compositeness scenario. It turns out that the minimal model does not require the enlargement of the exotic fermionic sector, but only the addition of a singlet scalar: it is sufficient that the exotic fermions involved in partial compositeness and the singlet scalar become charged under Peccei-Quinn transformations. We explore the phenomenological predictions for photonic signals in axion searches for all models discussed. Because of the constraints imposed on the exotic fermion sector by the Standard Model fermion masses, the expected range of allowed axion-photon couplings turns out to be generically narrowed with respect to that of standard invisible axion models, impacting the experimental quest.Comment: 31 pages, 2 Figures. Description improved, results unchange

Statistical Matrix for Electroweak Baryogenesis

In electroweak baryogenesis, a domain wall between the spontaneously broken and unbroken phases acts as a separator of baryon (or lepton) number, generating a baryon asymmetry in the universe. If the wall is thin relative to plasma mean free paths, one computes baryon current into the broken phase by determining the quantum mechanical transmission of plasma components in the potential of the spatially changing Higgs VEV. We show that baryon current can also be obtained using a statistical density operator. This new formulation of the problem provides a consistent framework for studying the influence of quasiparticle lifetimes on baryon current. We show that when the plasma has no self-interactions, familiar results are reproduced. When plasma self-interactions are included, the baryon current into the broken phase is related to an imaginary time temperature Green's function.Comment: 20 pages, no figures, Late

Dark Coupling and Gauge Invariance

We study a coupled dark energy-dark matter model in which the energy-momentum exchange is proportional to the Hubble expansion rate. The inclusion of its perturbation is required by gauge invariance. We derive the linear perturbation equations for the gauge invariant energy density contrast and velocity of the coupled fluids, and we determine the initial conditions. The latter turn out to be adiabatic for dark energy, when assuming adiabatic initial conditions for all the standard fluids. We perform a full Monte Carlo Markov Chain likelihood analysis of the model, using WMAP 7-year data.Comment: 16 pages, 2 figures, version accepted for publication in JCA

A Light Dynamical Scalar Boson

With the discovery of a scalar resonance at ATLAS and CMS, the understanding of the electroweak symmetry breaking origin seems a much closer goal. A strong dynamics at relatively low scales is still a good candidate. In this talk, the complete effective Lagrangian up to d < 6 will be presented, both for the gauge and the flavour sectors. Interesting features in the flavour phenomenology will be discussed.Comment: 10 pages, 3 figures, Talk given at the XLVIIIth Rencontres de Moriond session devoted to ELECTROWEAK INTERACTIONS AND UNIFIED THEORIES, La Thuile (Italy), 2-9 March 201

CP Violation and the Baryonic Asymmetry of the Universe

The physics of electroweak baryogenesis is described with the aim of making the essentials clear to non-experts. Several models for the source of the necessary CP violation are discussed: CKM phases as in the minimal standard model, general two higgs doublet models, the supersymmetric standard model, $Z$ condensates, and the singlet majoron model. In a more technical section, a strategy is introduced for consistently treating quark dynamics in the neighborhood of the bubble wall, where both local and non-local interactions are important. This provides a method for deciding whether gluonic corrections wash out the elecroweak contribution to the baryonic asymmetry in the minimal standard model.Comment: latex, 42pp, no figs. Invited talk at Trends in Astroparticle Physics, Stockholm, Sept 1994

Relations among Zero Momentum Correlators for Heavy-Light Systems in QCD

Relations connecting various zero momentum correlators of interpolating fields for pseudoscalar and scalar channel, containing one heavy and one light quark field, are derived from the Euclidean space formulation of the QCD functional integral. These relations may serve as constraints on the phenomenological models or approaches motivated from QCD, and suggest a method to extract the chiral quark condensates. It is also found that the correlator for pseudoscalar channel differs from that for scalar channel even in the large heavy quark mass limit.Comment: 9 pages in ReVTeX, UMD preprint #94-14

On The Potential of Minimal Flavour Violation

Assuming the Minimal Flavour Violation hypothesis, we derive the general scalar potential for fields whose background values are the Yukawa couplings. We analyze the minimum of the potential and discuss the fine-tuning required to dynamically generate the mass hierarchies and the mixings between different quark generations. Two main cases are considered, corresponding to Yukawa interactions being effective operators of dimension five or six (or, equivalently, resulting from bi-fundamental and fundamental scalar fields, respectively). At the renormalizable and classical level, no mixing is naturally induced from dimension five Yukawa operators. On the contrary, from dimension six Yukawa operators one mixing angle and a strong mass hierarchy among the generations result.Comment: 33 pages, 6 figures; Note added in proof on the stability of the minima of the scalar potential; results unchanged; references adde