Flavor mixing in a Lee-type model

An exactly solvable quantum field theory (QFT) model of Lee type is constructed to study how neutrino flavor eigenstates are created through interactions and how the localization properties of neutrinos follows from the parent particle that decays. The two-particle states formed by the neutrino and the accompanying charged lepton can be calculated exactly as well as their creation probabilities. We can show that the coherent creation of neutrino flavor eigenstates follows from the common negligible contribution of neutrino masses to their creation probabilities. on the other hand, it is shown that it is not possible to associate a well-defined flavor to coherent superpositions of charged leptons.

Search for Heavy Neutrinos and W-R Bosons with Right-Handed Couplings in a Left-Right Symmetric Model in pp Collisions at root s=7 TeV

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Probing neutralino properties in minimal supergravity with bilinear R-parity violation

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Electric charge quantization in a chiral bilepton gauge model

In the context of the standard model the quantization of the electric charge occurs only family by family. When we consider the three families together with massless neutrinos the electric charge is not quantized any more. Here we show that a chiral bilepton gauge model based on the gauge group SU(3)C ⊗ SU(3)L ⊗ U(1)N explains the quantization of the electric charge when we take into account the three families of fermions. This result does not depend on the neutrino masses. Charge quantization occurs whether the neutrinos are massless or Dirac or Majorana massive fields.

Post-sphaleron baryogenesis and an upper limit on the neutron-antineutron oscillation time

A recently proposed scenario for baryogenesis, called post-sphaleron baryogenesis (PSB), is discussed within a class of quark-lepton unified framework based on the gauge symmetry SU(2)L×SU(2) R×SU(4)c realized in the multi-TeV scale. The baryon asymmetry of the Universe in this model is produced below the electroweak phase transition temperature after the sphalerons have decoupled from the Hubble expansion. These models embed naturally the seesaw mechanism for neutrino masses and predict color-sextet scalar particles in the TeV range which may be accessible to the LHC experiments. A necessary consequence of this scenario is the baryon-number-violating ΔB=2 process of neutron-antineutron (n-n̄) oscillations. In this paper we show that the constraints of PSB, when combined with the neutrino oscillation data and restrictions from flavor changing neutral currents mediated by the colored scalars, imply an upper limit on the n-n̄ oscillation time of 5×1010 sec regardless of the quark-lepton unification scale. If this scale is relatively low, in the (200-250) TeV range, τn-n̄ is predicted to be less than 1010 sec, which is accessible to the next generation of proposed experiments. © 2013 American Physical Society.

On baryogenesis from dark matter annihilation

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Complex scalar dark matter in a B-L model

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Search for heavy neutrinos and W bosons with right-handed couplings in proton-proton collisions at root s=8TeV

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Limit on gamma(pi-0-]nu-nu-bar) from SN1987A

We consider the possible neutrino emission from SN1987A generated through the process γγ→π0→νν, which is permitted when the neutrinos have a right-handed component. This energy-loss mechanism is consistent with the supernova neutrino observations if the decay rate I (π0→νν̄) < (0.15-6.3) × 10-13 eV. When the reaction π0→νν̄ is mediated by weak gauge bosons the limit on the decay rate allows us to obtain constraints on neutrino masses, mv<5-27 keV, depending on the core temperature.

O setor leptônico neutro e a violação de CP

Pós-graduação em Física - IFT

A rationale for long-lived quarks and leptons at the LHC: low energy flavour theory

In the framework of gauged flavour symmetries, new fermions in parity symmetric representations of the standard model are generically needed for the compensation of mixed anomalies. The key point is that their masses are also protected by flavour symmetries and some of them are expected to lie way below the flavour symmetry breaking scale(s), which has to occur many orders of magnitude above the electroweak scale to be compatible with the available data from flavour changing neutral currents and CP violation experiments. We argue that, actually, some of these fermions would plausibly get masses within the LHC range. If they are taken to be heavy quarks and leptons, in (bi)-fundamental representations of the standard model symmetries, their mixings with the light ones are strongly constrained to be very small by electroweak precision data. The alternative chosen here is to exactly forbid such mixings by breaking of flavour symmetries into an exact discrete symmetry, the so-called proton-hexality, primarily suggested to avoid proton decay. As a consequence of the large value needed for the flavour breaking scale, those heavy particles are long-lived and rather appropriate for the current and future searches at the LHC for quasi-stable hadrons and leptons. In fact, the LHC experiments have already started to look for them.

Probing neutralino properties in minimal supergravity with bilinear R-parity violation

Supersymmetric models with bilinear R-parity violation can account for the observed neutrino masses and mixing parameters indicated by neutrino oscillation data. We consider minimal supergravity versions of bilinear R-parity violation where the lightest supersymmetric particle is a neutralino. This is unstable, with a large enough decay length to be detected at the CERN Large Hadron Collider. We analyze the Large Hadron Collider potential to determine the lightest supersymmetric particle properties, such as mass, lifetime and branching ratios, and discuss their relation to neutrino properties.

Flavour symmetries in a renormalizable SO(10) model

In the context of a renormalizable supersymmetric SO(10) Grand Unified Theory, we consider the fermion mass matrices generated by the Yukawa couplings to a 10 circle plus 120 circle plus (126) over bar representation of scalars. We perform a complete investigation of the possibilities of imposing flavour symmetries in this scenario; the purpose is to reduce the number of Yukawa coupling constants in order to identify potentially predictive models. We have found that there are only 14 inequivalent cases of Yukawa coupling matrices, out of which 13 cases are generated by 74 symmetries, with suitable n, and one case is generated by a Z(2) x Z(2) symmetry. A numerical analysis of the 14 cases reveals that only two of them-dubbed A and B in the present paper allow good fits to the experimentally known fermion masses and mixings. (C) 2016 The Authors. Published by Elsevier B.V.

Calculable lepton masses, seesaw relations, and four neutrino mixings in a 3-3-1 model with an extra U(1) symmetry

We propose a scheme in which the masses of the heavier leptons obey seesaw type relations. The light lepton masses, except the electron and the electron neutrino ones, are generated by one loop level radiative corrections. We work in a version of the 3-3-1 electroweak model that predicts singlets (charged and neutral) of heavy leptons beyond the known ones. An extra U(1)(Omega) symmetry is introduced in order to avoid the light leptons getting masses at the tree level. The electron mass induces an explicit symmetry breaking at U(1)(Omega). We discuss also the mixing matrix among four neutrinos. The new energy scale required is not higher than a few TeV.

Calculable lepton masses, seesaw relations, and four neutrino mixings in a 3-3-1 model with an extra U(1) symmetry

We propose a scheme in which the masses of the heavier leptons obey seesaw type relations. The light lepton masses, except the electron and the electron neutrino ones, are generated by one loop level radiative corrections. We work in a version of the 3-3-1 electroweak model that predicts singlets (charged and neutral) of heavy leptons beyond the known ones. An extra U(1)(Omega) symmetry is introduced in order to avoid the light leptons getting masses at the tree level. The electron mass induces an explicit symmetry breaking at U(1)(Omega). We discuss also the mixing matrix among four neutrinos. The new energy scale required is not higher than a few TeV.