Gabriel Lopez Castro

Bounding resonant Majorana neutrinos from four-body B and D decays

Searches of lepton-number violation in different processes are very useful to constrain the parameter space of Majorana neutrinos. Here we use available upper bounds on the branching fractions of B^- -> D^0pi^+mu^-mu^- and D^0 -> (pi^-pi^-/K^-pi^-) mu^-mu^- decays to derive constraints on the mass and mixings of Majorana neutrinos by assuming they are produced resonantly in these four-body decays. While the excluded region obtained from B^- decays are competitive with existing limits from three-body D^- and B^- decays, it is shown that experimental improvements on D^0 decays offer a good potential to provide similar results.

Recent progress on isospin breaking corrections and their impact on the muon g ? 2 value

We describe some recent results on isospin breaking corrections which are of relevance for predictions of the leading order hadronic contribution to the muon anomalous magnetic moment ahad,LOμ when using τ lepton data. When these corrections are applied to the new combined data on the π±π0 spectral function, the prediction for ahad,LOμ based on τ lepton data gets closer to the one obtained using e+e− data.

Heavy Majorana Neutrinos and Delta L=2 B and top decays in B factories

Majorana neutrinos can induced Lepton number violation (LNV)in four-body decays of the neutral B meson and the top quark. We study the effects of Majorana neutrinos in these |∆L| = 2 decays in an scenario where a single heavy neutrino can enhance the amplitude via the resonant mechanism. Using current bounds on heavy neutrino mixings, the most optimistic branching ratios turn out to be at the level of 10−6 for B0 → D+e−e−π+ and t → bl+l+W− decays. Searches for these LNV decays at future facilities can provide complementary constraints on masses and mixings of Majorana neutrinos.

A new strategy for probing the Majorana neutrino CP violating phases and masses1

We propose a new strategy for detecting the CP‐violating phases and the effective mass of muon Majorana neutrinos by measuring observables associated with neutrino‐antineutrino oscillations in π± decays. Within the generic framework of quantum field theory, we compute the non‐factorizable probability for producing a pair of same‐charged muons in π± decays as a distinctive signature of νμ‐νμ oscillations. Using the neutrino‐antineutrino oscillation probability reported by MINOS collaboration, a new stringent bound on the effective muon‐neutrino mass is derived.

CP asymmetry in Neutrino Oscillations and New Physics1

The CP asymmetry in neutrino oscillations, assuming new physics at production and/or detection processes, is analyzed. We compute this CP asymmetry using the standard quantum field theory within a general new physics scenario that may generate new sources of CP and flavor violation. Well known results for the CP asymmetry are reproduced in the case of V‐A operators, and additional contributions from new physics operators are derived.

New Physics in ΔL = 2 neutrino oscillations

We propose a general framework to constrain ΔL = 2 processes by measuring observ-ables associated with neutrino-antineutrino oscillations in π± decays. First, we use this formalism as a new strategy for detecting the CP-violating phases and the effective mass of muon Majorana neutrinos. Within the generic framework of quantum field theory, we compute the non-factorizable probability for producing a pair of same-charged muons in π± decays as a distinctive signature of oscillations. Using the neutrino-antineutrino oscillation probability reported by MINOS collaboration, a new stringent bound on the effective muon-neutrino mass is derived. Secondly, we interpret the production of the pair of same-charged muons as a result of lepton number violating (LNV) interactions at the neutrino source, which allow us to constrain New Physics.

Unstable Particles, Gauge Invariance and the Δ++ Resonance Parameters

AbstractThe elastic and radiative π+p scattering are studied in the framework of an effective Lagrangian model for the Δ++ resonance and its interactions. The finite width effects of this spin-3/2 resonance are introduced in the scattering amplitudes through a complex mass scheme to respect electromagnetic gauge invariance. The resonant pole (Δ++) and background contributions (ρ0, σ, Δ, and neutron states) are separated according to the principles of the analytic S-matrix theory. The mass and width parameters of the Δ++ obtained from a fit to experimental data on the total cross section are in agreement with the results of a model-independent analysis based on the analytic S-matrix approach. The magnetic dipole moment determined from the radiative π+p scattering is n

(?,?)P- decays of tau leptons

mu _{Delta ^{ + + } } = (6.14 pm 0.51)