arXiv subjects
Publications and source records attributed to R. Zukanovich Funchal.
We have found that long-wavelength neutrino oscillations induced by a tiny breakdown of the weak equivalence principle of general relativity can provide a viable solution to the solar neutrino problem.
We have investigated the possibility of discerning mass from flavor changing neutrino interactions induced $ν_μ\to ν_τ$ oscillations in the long baseline neutrino experiments K2K and MINOS. We have found that for virtually any value of the flavor conserving parameter $ε^\prime$ it will be possible to, independently, distinguish these two mechanisms at K2K, if the flavor changing parameter $ε$ is in the range $ε\gsim 0.77$, and at MINOS, if $ε\gsim 0.2$. Moreover, if K2K measures a depletion of the expected $ν_μ$ flux then MINOS will either observe or discard completely flavor changing neutrino oscillations.
We discuss the use of the CP asymmetry parameter (Acp) as a possible observable of CP violation in the leptonic sector. In order to do this, we study for a wide range of values of L/E the behavior of this asymmetry for the corresponding maximal value of the CP violation factor allowed by all present experimental limits on neutrino oscillations in vacuum and the recent Super-Kamiokande atmospheric neutrino result. We work in the three neutrino flavor framework.
We have reexamined the possibility of explaining the solar neutrino problem through long-wavelength neutrino oscillations induced by a tiny breakdown of the weak equivalence principle of general relativity. We found that such gravitationally induce oscillations can provide a viable solution to the solar neutrino problem.
Theoretical models which present flavor changing neutrino interactions and simultaneously prevent this particle from acquiring any mass exist. We discuss some of them and their predictions for neutrino oscillations in matter which can account for the solar neutrino anomaly as well as the zenith-angle dependence of the deficit of atmospheric neutrinos observed by the SuperKamiokande experiment without invoking, therefore, neutrino masses nor mixing.
Flavor changing (FC) neutrino-matter interactions can account for the zenith-angle dependent deficit of atmospheric neutrinos observed in the SuperKamiokande experiment, without directly invoking neither neutrino mass, nor mixing. We find that FC $ν_μ$-matter interactions provide a good fit to the observed zenith angle distributions, comparable in quality to the neutrino oscillation hypothesis. The required FC interactions arise naturally in many attractive extensions of the Standard Model.
We investigate the sensitivity of some weak processes to the simplest extension of the Standard Model with Majorana neutrinos mixing in the leptonic sector. Values for mixing angles and masses compatible with several experimental accelerator data and the most recent neutrinoless double--$β$ decay limit were found.
A Feed Forward Error Back Propagation Artificial Neural Network(ANN) algorithm is developed for electron/positron identification in a wide momentum region (10 - 300 GeV/c). The method was proposed for the Transition Radiation Detector of the E781 experiment at Fermilab. The package consists of two parts: - the program for the ANN training; - the particle classification subroutine. Both parts are built using the object oriented technique and C++ language. The particle identification algorithm is wrapped in FORTRAN closers to be used in the E781 off-line program. The package performance was tested in comparison with the likelihood ratio method using Monte Carlo generated data. Our study has demonstrated the excellent ability of the ANN to learn even small details of the detector response function. The ANN solution gives the same performance and behavior as the likelihood method when using Monte Carlo data with known detector parameters. It demonstrates that if trained with experimental data the package can provide a very good solution to the classification problem of $e^+/e^-$ tracks.
We point out that the usual experimental upper bounds on the ``tau-neutrino mass'' do not apply if neutrino mixing is considered. The suppression of the population of the tau decay spectrum near the end-point, caused by mixing, may be compensated by an enhancement due to a resonant mechanism of hadronization. It is necessary therefore to analyse the whole spectrum to infer some limit to the ``tau-neutrino mass". We argue that, consequently, neutrino mixing evades the objection to interpret KARMEN anomaly as a heavy sequential neutrino.
We find an exact analytic solution for the time evolution of a three Dirac neutrino system adiabatically oscillating in matter, constructing explicitly the relevant $3\times 3$ mixing matrix in matter. Using this result we investigate the solar neutrino data in a scenario where the neutrino masses are such that $m_1\alt m_2\ll m_3$, taking into account several phenomenological constraints on neutrino mixing angles and masses. A solution of the solar neutrino problem for large values of the parameter $δm^2=m_2^2-m_1^2$ which are not usually associated with a resonance is found. This is an essentially three-generation effect.
We investigate the solar neutrino problem in the scenario of three generation neutrino oscillation hypothesis, taking into account other phenomenological constraints to the neutrino mixing and mass parameters.
We investigate the sensitivity of some weak processes to a Cabibbo--Kobayashi--Maskawa mixing in the leptonic sector. Values for mixing angles and masses compatible with several experimental accelerator data were found. We discuss in this context neutrino oscillations, cosmological and astrophysical consequences as well.
We study the constraints on masses and mixing angles imposed by the measured $Z^0$ invisible width, in a model in which a singlet right-handed neutrino mixes with all the Standard Model neutrinos.
We consider the possibility that the $τ$ decay puzzle, if it is confirmed in future experiments, is a consequence of the Kobayashi-Maskawa mixing in the leptonic sector
We analize the current data on $τ$-lepton decays and show that they are consistent with the Standard Model