Martti Raidal

New parametrization of the seesaw mechanism and applications in supersymmetric models

We present a new parametrization of the minimal seesaw model, expressing the heavy-singlet neutrino Dirac Yukawa couplings (Y n) ij and Majorana masses MNi in terms of effective light-neutrino observables and an auxiliary Hermitian matrix H. In the minimal supersymmetric version of the seesaw model, the latter can be related directly to other low-energy observables, including processes that violate charged lepton flavor and CP . This parametrization enables one to respect the stringent constraints on muon-number violation while studying the possible ranges for other observables by scanning over the allowed parameter space of the model. Conversely, if any of the lepton-flavor-violating process is observed, this measurement can be used directly to constrain ( Y n) ij and MN i . As applications, we study flavor-violating t decays and the electric dipole moments of leptons in the minimal supersymmetric seesaw model.

Is the resonance at 125 GeV the Higgs boson

The recently discovered resonance at 125 GeV has properties remarkably close to those of the Standard Model Higgs boson. We perform model-independent ts of all presently available data. The non

Reconstructing Higgs boson properties from the LHC and Tevatron data

A bstractWe perform a phenomenological fit to all ATLAS, CMS, CDF and D0 Higgs boson data available after Moriond 2012. We allow all Higgs boson branching fractions, its couplings to standard model particles, as well as to an hypothetical invisible sector to vary freely, and determine their current favourite values. The standard model Higgs boson with a mass 125xa0GeV correctly predicts the average observed rate and provides an acceptable global fit to data. However, better fits are obtained by non-standard scenarios that reproduce anomalies in the present data (more γγ and less WW signals than expected) such as modified rates of loop processes or partial fermiophobia. We find that present data disfavours Higgs boson invisible decays. We consider implications for the standard model, for supersymmetric and fermiophobic Higgs bosons, for dark matter models, for warped extra-dimensions.

Fermi 130 GeV gamma-ray excess and dark matter annihilation in sub-haloes and in the Galactic centre

We analyze publicly available Fermi-LAT high-energy gamma-ray data and confirm the existence of clear spectral feature peaked at Eγ = 130 GeV. Scanning over the Galaxy we identify several disconnected regions where the observed excess originates from. Our best optimized fit is obtained for the central region of Galaxy with a clear peak at 130 GeV with local statistical significance 4.5σ. The observed excess is not correlated with Fermi bubbles. We compute the photon spectra induced by dark matter annihilations into two and four standard model particles, the latter via two light intermediate states, and fit the spectra with data. Since our fits indicate sharper and higher signal peak than in the previous works, data favors dark matter direct two-body annihilation channels into photons or other channels giving only line-like spectra. If Einasto halo profile correctly predicts the central cusp of Galaxy, dark matter annihilation cross-section to two photons is of order ten percent of the standard thermal freeze-out cross-section. The large dark matter two-body annihilation cross-section to photons may signal a new resonance that should be searched for at the CERN LHC experiments.

Leptogenesis and the violation of lepton number and CP at low energies

Abstract In the context of the minimal supersymmetric seesaw model, we study the implications of the current neutrino data for thermal leptogenesis, ββ0ν decay, and leptonic flavour- and CP-violating low-energy observables. We express the heavy singlet-neutrino Dirac–Yukawa couplings (Yν)ij and Majorana masses MNi in terms of the light-neutrino observables and an auxiliary Hermitian matrixxa0H, which enables us to scan systematically over the allowed parameter space. If the lightest heavy neutrino N1 decays induce the baryon asymmetry, there are correlations between the MN1, the lightest active neutrino mass and the primordial lepton asymmetry ϵ1 on the one hand, and the ββ0ν decay parameter mee on the other hand. However, leptogenesis is insensitive to the neutrino oscillation phase. We find lower bounds MN1≳1010 GeV for the normal light-neutrino mass hierarchy, and MN1≳1011 GeV for the inverted mass hierarchy, respectively, indicating a potentially serious conflict with the gravitino problem. Depending on MN1, we find upper (upper and lower bounds) on the lightest active neutrino mass for the normal (inverted) mass hierarchy, and a lower bound on mee even for the normal mass ordering. The low-energy lepton-flavour- and CP-violating observables induced by renormalization are almost independent of leptogenesis. The electron–electric dipole moment may be close to the present bound, reaching d e ∼10 −(27−28) e cm in our numerical examples, while dμ may reach d μ ∼10 −25 e xa0cm.

Predictions of the most minimal see-saw model

Abstract We derive the most minimal see-saw texture from an extra-dimensional dynamics. It predicts θ13=0.078±0.015 and m ee =2.6±0.4 meV . Assuming thermal leptogenesis, the sign of the CP-phase measurable in neutrino oscillations, together with the sign of baryon asymmetry, determines the order of heavy neutrino masses. Unless heavy neutrinos are almost degenerate, successful leptogenesis fixes the lightest mass. Depending on the sign of the neutrino CP-phase, the supersymmetric version of the model with universal soft terms at high scale predicts BR(μ→eγ) or BR(τ→μγ), and gives a lower bound on the other process.

CP Violation in the Minimal Supersymmetric Seesaw Model

Abstract We study CP violation in the lepton sector of the supersymmetric extension of the Standard Model with three generations of massive singlet neutrinos with Yukawa couplings Yν to lepton doublets, in a minimal seesaw model for light neutrino masses and mixing. This model contains six physical CP-violating parameters, namely the phase δ observable in oscillations between light neutrino species, two Majorana phases φ1,2 that affect ββ0ν decays, and three independent phases appearing in Y ν Y ν † , that control the rate of leptogenesis. Renormalization of the soft supersymmetry-breaking parameters induces observable CP violation at low energies, including T-odd asymmetries in polarized μ→eee and τ→lll decays, as well as lepton electric dipole moments. In the leading-logarithmic approximation in which the massive singlet neutrinos are treated as degenerate, these low-energy observables are sensitive via Y ν † Y ν to just one combination of the leptogenesis and light-neutrino phases. We present numerical results for the T-odd asymmetry in polarized μ→eee decay, which may be accessible to experiment, but the lepton electric dipole moments are very small in this approximation. To the extent that the massive singlet neutrinos are not degenerate, low-energy observables become sensitive also to two other combinations of leptogenesis and light-neutrino phases, in this minimal supersymmetric seesaw model.

Sneutrino inflation in the light of WMAP: reheating, leptogenesis and flavour-violating lepton decays

Abstract We reconsider the possibility that inflation was driven by a sneutrino—the scalar supersymmetric partner of a heavy singlet neutrino—in the minimal seesaw model of neutrino masses. We show that this model is consistent with data on the cosmic microwave background (CMB), including those from the WMAP satellite. We derive and implement the CMB constraints on sneutrino properties, calculate reheating and the cosmological baryon asymmetry arising via direct leptogenesis from sneutrino decays following sneutrino inflation, and relate them to light neutrino masses. We show that this scenario is compatible with a low reheating temperature that avoids the gravitino problem, and calculate its predictions for flavour-violating decays of charged leptons. We find that μ → eγ should occur close to the present experimental upper limits, as might also τ → μγ .

Lepton electric dipole moments in non-degenerate supersymmetric seesaw models

Abstract In the context of supersymmetric seesaw models of neutrino masses with non-degenerate heavy neutrinos, we show that Dirac Yukawa interactions Nci(Yν)ijLjH2 induce large threshold corrections to the slepton soft masses via renormalization. While still yielding rates for lepton-flavour-violating processes below the experimental bounds, these contributions may increase the muon and electron electric dipole moments dμ and de by several orders of magnitude. In the leading logarithmic approximation, this is due to three additional physical phases in Yν, one of which also contributes to leptogenesis. The naive relation dμ/de≈−mμ/me is violated strongly in the case of successful phenomenological textures for Yν, and the values of dμ and/or de may be within the range of interest for the future experiments.

Higgs-mediated Bs,d0→μτ,eτ and τ→3μ,eμμ decays in supersymmetric seesaw models

We study the rates allowed for the Higgs-mediated decays