arXiv subjects

R. Zukanovich Funchal

Publications and source records attributed to R. Zukanovich Funchal.

At least 37 records · Page 2Linked to original sources

arXiv2006

A Reanalysis of the LSND Neutrino Oscillation Experiment

We reanalyse the LSND neutrino oscillation results in the framework of the Projected Quasiparticle Random Phase Approximation (PQRPA), which is the only RPA model that treats the Pauli Principle correctly, and accounts satisfactorily for great majority of the weak decay observables around 12C. We have found that the employment of the PQRPA inclusive DIF 12C(nu_e,e-)12N cross-section, instead of the CRPA used by the LSND collaboration in the (nu_mu ->nu_e) oscillations study of the 1993-1995 data sample, leads to the following: 1) the oscillation probability is increased from (0.26 +/- 0.10 +/- 0.05) percents to (0.33 +/- 0.10 +/- 0.13) percents, and 2) the previously found consistence between the (sin^2 2theta, Delta m^2) confidence level regions for the (nu_mu -> nu_e) and the (bar{nu}_mu -> bar{nu}_e) oscillations is significantly diminished. These effects are not due to the difference in the uncertainty ranges for the neutrino-nucleus cross-section, but to the difference in the cross-sections themselves.

nucl-th↗

arXiv2006

Determining Neutrino Mass Hierarchy by Precision Measurements in Electron and Muon Neutrino Disappearance Experiments

Recently a new method for determining the neutrino mass hierarchy by comparing the effective values of the atmospheric Δm^2 measured in the electron neutrino disappearance channel, Δm^2(ee), with the one measured in the muon neutrino disappearance channel, Δm^2(μμ), was proposed. If Δm^2(ee) is larger (smaller) than Δm^2(μμ) the hierarchy is of the normal (inverted) type. We re-examine this proposition in the light of two very high precision measurements: Δm^2(μμ) that may be accomplished by the phase II of the Tokai-to-Kamioka (T2K) experiment, for example, and Δm^2(ee) that can be envisaged using the novel Mossbauer enhanced resonant \barν_e absorption technique. Under optimistic assumptions for the systematic uncertainties of both measurements, we estimate the parameter region of (θ_13, δ) in which the mass hierarchy can be determined. If θ_13 is relatively large, sin^2 2θ_13 \gsim 0.05, and both of Δm^2(ee) and Δm^2(μμ) can be measured with the precision of \sim 0.5 % it is possible to determine the neutrino mass hierarchy at > 95% CL for 0.3 π\lsim δ\lsim 1.7 πfor the current best fit values of all the other oscillation parameters.

hep-ph↗

arXiv2006

Effects of Environment Dependence of Neutrino Mass versus Solar and Reactor Neutrino Data

In this work we study the phenomenological consequences of the environment dependence of neutrino mass on solar and reactor neutrino phenomenology. Such dependence can be induced, for example, by Yukawa interactions with a light scalar particle which couples to neutrinos and matter and it is expected, among others, in mass varying neutrino scenarios. Under the assumption of one mass scale dominance, we perform a global analysis of solar and KamLAND neutrino data which depends on 4 parameters: the two standard oscillation parameters, Delta m^2 and tan^2(theta), and two new coefficients, which parameterize the environment dependence of the neutrino mass. We find that, generically, the inclusion of the environment dependent terms does not lead to a very statistically significant improvement on the description of the data in the most favoured MSW LMA (or LMA-I) region. It does, however, substantially improve the fit in the high-Delta m^2 LMA (or LMA-II) region which can be allowed at 98.9% CL. Conversely the analysis allow us to place stringent constraints on the size of the environment dependence terms, which can be translated on a bound on the product of the effective neutrino-scalar (lambda^ν) and matter-scalar (lambda^N) Yukawa couplings, as a function of the scalar field mass (m_S) in these models.

hep-ph↗

arXiv2005

Reactor measurement of θ_{12}; Secret of the power

We demonstrate enormous power of dedicated reactor experiment for θ_{12} with a detector placed at around the first oscillation maximum, which we call "SADO". It allows determination of sin^2θ_{12} to the accuracy of \simeq 2% at 1 σCL, which surpasses all the method so far proposed. Unlike reactor θ_{13} experiments, the requirement for the systematic error is very mild, \simeq 4%, which makes it an even more feasible experiment. If we place a detector at \sim 60 km away from the Kashiwazaki-Kariwa nuclear power plant, 0.5 kt yr exposure of SADO is equivalent to \sim 100 kt yr exposure of KamLAND assuming the same systematic error.

hep-ph↗

arXiv2005

Reactor Measurement of theta_12; Principles, Accuracies and Physics Potentials

We discuss reactor measurement of θ_{12} which has a potential of reaching the ultimate sensitivity which surpasses all the methods so far proposed. The key is to place a detector at an appropriate baseline distance from the reactor neutrino source to have an oscillation maximum at around a peak energy of the event spectrum in the absence of oscillation. By a detailed statistical analysis the optimal distance is estimated to be \simeq (50-70) km x [8 x 10^{-5} eV^2/Δm^2_{21}], which is determined by maximizing the oscillation effect in the event number distribution and minimizing geo-neutrino background contamination. To estimate possible uncertainty caused by surrounding nuclear reactors in distance of \sim 100 km, we examine a concrete example of a detector located at Mt. Komagatake, 54 km away from the Kashiwazaki-Kariwa nuclear power plant in Japan, the most powerful reactor complex in the world. The effect turns out to be small. Under a reasonable assumption of systematic error of 4% in the experiment, we find that sin^2{θ_{12}} can be determined to the accuracy of \simeq 2% (\simeq 3%), at 68.27% CL for 1 degree of freedom, for 60 GW_th kton yr (20 GW_th kton yr) operation. We also discuss implications of such an accurate measurement of θ_{12}.

hep-ph↗

arXiv2003

Discriminating among Earth composition models using geo-antineutrinos

It has been estimated that the entire Earth generates heat corresponding to about 40 TW (equivalent to 10,000 nuclear power plants) which is considered to originate mainly from the radioactive decay of elements like U, Th and K, deposited in the crust and mantle of the Earth. Radioactivity of these elements produce not only heat but also antineutrinos (called geo-antineutrinos) which can be observed by terrestrial detectors. We investigate the possibility of discriminating among Earth composition models predicting different total radiogenic heat generation, by observing such geo-antineutrinos at Kamioka and Gran Sasso, assuming KamLAND and Borexino (type) detectors, respectively, at these places. By simulating the future geo-antineutrino data as well as reactor antineutrino background contributions, we try to establish to which extent we can discriminate among Earth composition models for given exposures (in units of kt$\cdot$ yr) at these two sites on our planet. We use also information on neutrino mixing parameters coming from solar neutrino data as well as KamLAND reactor antineutrino data, in order to estimate the number of geo-antineutrino induced events.

hep-ph↗

arXiv2003

Probing the LSND scale and four neutrino scenarios with a neutrino telescope

We show in this paper that the observation of the angular distribution of upward-going muons and cascade events induced by atmospheric neutrinos at the TeV energy scale, which can be performed by a kilometer-scale neutrino telescope, such as the IceCube detector, can be used to probe a large neutrino mass splitting, $| Δm^2 | \sim (0.5-2.0)$ eV$^2$, implied by the LSND experiment and discriminate among four neutrino mass schemes. This is due to the fact that such a large mass scale can promote non negligible muon neutrino to electron/tau neutrino (and/or anti-muon neutrino to anti-electron/anti-tau neutrino) conversions at these energies by the MSW effect as well as vacuum oscillation, unlike what is expected if all the neutrino mass splittings are small.

hep-ph↗

arXiv2003

Determining the oscillation parameters by Solar neutrinos and KamLAND

The neutrino oscillation experiment KamLAND has given the first evidence for disappearance of $\bar ν_e$ coming from nuclear reactors. We have combined their data with all the solar neutrino data assuming two flavor neutrino mixing and obtained allowed parameter regions which are compatible with the so-called large mixing angle MSW solution to the solar neutrino problem. The allowed regions in the plane of mixing angle and mass squared difference are now split into two islands at 99% C.L. We have speculated how these two islands can be separated in the near future. We have shown that a 50% reduction of the error on SNO neutral-current measurement can be important in establishing in each of these islands the true values of these parameters lie. We also have simulated KamLAND positron energy spectrum after 1 year of data taking, assuming the current best fitted values of the oscillation parameters, combined it the with current solar neutrino data and showed how these two split islands can be modified.

hep-ph↗

arXiv2002

Constraining the absolute neutrino mass scale and Majorana CP violating phases by future neutrinoless double beta decay experiments

Assuming that neutrinos are Majorana particles, in a three generation framework, current and future neutrino oscillation experiments can determine six out of the nine parameters which fully describe the structure of the neutrino mass matrix. We try to clarify the interplay among the remaining parameters, the absolute neutrino mass scale and two CP violating Majorana phases, and how they can be accessed by future neutrinoless double beta ($0νββ$) decay experiments, for the normal as well as for the inverted order of the neutrino mass spectrum. Assuming the oscillation parameters to be in the range presently allowed by atmospheric, solar, reactor and accelerator neutrino experiments, we quantitatively estimate the bounds on $m_0$, the lightest neutrino mass, that can be infered if the next generation $0νββ$ decay experiments can probe the effective Majorana mass ($m_{ee}$) down to $\sim$ 1 meV. In this context we conclude that in the case neutrinos are Majorana particles: (a) if $m_0 \gsim 300$ meV, {\em i.e.}, within the range directly attainable by future laboratory experiments as well as astrophysical observations, then $m_{ee} \gsim 30$ meV must be observed; (b) if $m_0 < 300$ meV, results from future $0νββ$ decay experiments combined with stringent bounds on the neutrino oscillation parameters, specially the solar ones, will place much stronger limits on the allowed values of $m_0$ than these direct experiments.

hep-ph↗

arXiv2002

Measuring the Spectra of High Energy Neutrinos with a Kilometer-Scale Neutrino Telescope

We investigate the potential of a future kilometer-scale neutrino telescope such as the proposed IceCube detector in the South Pole, to measure and disentangle the yet unknown components of the cosmic neutrino flux, the prompt atmospheric neutrinos coming from the decay of charmed particles and the extra-galactic neutrinos, in the 10 TeV to 1 EeV energy range. Assuming a power law type spectra, $dϕ_ν/dE_ν\sim αE_ν^β$, we quantify the discriminating power of the IceCube detector and discuss how well we can determine magnitude ($α$) as well as slope ($β$) of these two components of the high energy neutrino spectrum, taking into account the background coming from the conventional atmospheric neutrinos.

hep-ph↗

arXiv2002

A study on quantum decoherence phenomena with three generations of neutrinos

Using the open quantum system approach applied to the neutrino system, we derive three generations neutrino probability formulae considering the oscillation induced by mass plus quantum decoherence contributions. The introduction of these dissipative effects is done through the quantum dynamical semigroup formalism. In addition to the theoretical interest of the approach, at least from the completeness point of view, this extension of the formalism to the three flavors, provide us with a direct application: we can analyze qualitatively the consistency of the two generation pure decoherence solution to the atmospheric neutrino problem, accommodated within this enlarged scheme, with the mean tendencies observed for some of the current neutrino experimental data. This study was performed based on different choices of the $3 \times 3$ mixing matrix selected in order to adjust the $P_{ν_μ \to ν_μ}$ to the same form it has for the decoherence solution in two generations. Our qualitative tests for decoherence with three neutrinos show a clear incompatibility between neutrino data and the theoretical expectations.

hep-ph↗

arXiv2002

Global Analysis of the post-SNO Solar Neutrino Data for Standard and Non-Standard Oscillation Mechanisms

What can we learn from solar neutrino observations? Is there any solution to the solar neutrino anomaly which is favored by the present experimental panorama? After SNO results, is it possible to affirm that neutrinos have mass? In order to answer such questions we analyze the current available data from the solar neutrino experiments, including the recent SNO result, in view of many acceptable solutions to the solar neutrino problem based on different conversion mechanisms, for the first time, using the same statistical procedure. This allows us to do a direct comparison of the goodness of the fit among different solutions, from which we can discuss and conclude on the current status of each proposed dynamical mechanism. These solutions are based on different assumptions: (a) neutrino mass and mixing, (b) non-vanishing neutrino magnetic moment, (c) the existence of non-standard flavor-changing and non-universal neutrino interactions and (d) the tiny violation of the equivalence principle. We investigate the quality of the fit provided by each one of these solutions not only to the total rate measured by all the solar neutrino experiments but also to the recoil electron energy spectrum measured at different zenith angles by the Super-Kamiokande collaboration. We conclude that several non-standard neutrino flavor conversion mechanisms provide a very good fit to the experimental data which is comparable with (or even slightly better than) the most famous solution to the solar neutrino anomaly based on the neutrino oscillation induced by mass.

hep-ph↗

arXiv2002

Neutrino oscillation parameters from MINOS, ICARUS and OPERA combined

We perform a detailed analysis of the capabilities of the MINOS, ICARUS and OPERA experiments to measure neutrino oscillation parameters at the atmospheric scale with their data taken separately and in combination. MINOS will determine $Δm^2_{32}$ and $\sin^2 2θ_{23}$ to within 10% at the 99% C.L. with 10 kton-years of data. While no one experiment will determine $\sin^2 2θ_{13}$ with much precision, if its value lies in the combined sensitivity region of the three experiments, it will be possible to place a lower bound of O(0.01) at the 95% C.L. on this parameter by combining the data from the three experiments. The same bound can be placed with a combination of MINOS and ICARUS data alone.

hep-ph↗

arXiv2001

Quantum Dissipative Effects and Neutrinos : current constraints and future perspectives

We establish the most stringent experimental constraints coming from recent terrestrial neutrino experiments on quantum mechanical decoherence effects in neutrino systems. Taking a completely phenomenological approach, we probe vacuum oscillations plus quantum decoherence between two neutrino species in the channels $ν_μ\to ν_τ$, $ν_μ\to ν_e$ and $ν_e \to ν_τ$, admitting that the quantum decoherence parameter $γ$ is related to the neutrino energy $E_ν$ as : $γ=γ_0 (E_ν/\text{GeV})^{n}$, with $n=-1,0,1$ and 2. Our bounds are valid for a neutrino mass squared difference compatible with the atmospheric, the solar and, in many cases, the LSND scale. We also qualitatively discuss the perspectives of the future long baseline neutrino experiments to further probe quantum dissipation.

hep-ph↗

arXiv2001

Probing Flavor Changing Neutrino Interactions Using Neutrino Beams from a Muon Storage Ring

We discuss the capabilities of a future neutrino factory based on intense neutrino beams from a muon storage ring to explore the non-standard neutrino matter interactions, which are assumed to be sub-leading effects in the standard mass induced neutrino oscillations. The conjunction of these two mechanisms will magnify fake CP violating effect in the presence of matter which is not coming from the CP phase in the neutrino mixing matrix. We show that such fake CP violation can be observed in neutrino factory experiments by measuring the difference between the neutrino and anti-neutrino probabilities. In order to perform such test, we consider three neutrino flavors, admitting the mixing parameters in the range consistent with the oscillation solution to the atmospheric and the solar neutrino problems, as well as with the constraints imposed by the reactor neutrino data. We show that with a 10 kt detector with 5 years of operation, a stored muon energy E_μ\ge 20 GeV, 2 \times 10^{20} muon decays per year, and a baseline L \sim 732 km, such a neutrino facility can probe the non-standard flavor changing neutrino interactions down to the level of (10^{-3}-10^{-2})~G_F, in both ν_μ\to ν_τ/ \bar ν_μ\to \bar ν_τand ν_e \to ν_τ/\bar ν_e \to \bar ν_τmodes.

hep-ph↗

arXiv2001

Quest for the dynamics of $ν_{mu} \to ν_{tau}$ conversion

We perform a quantitative analysis of the capability of K2K, MINOS, OPERA and a neutrino factory in a muon collider to discriminate the standard mass induced vacuum oscillation from the pure decoherence solution to the atmospheric neutrino problem and thereby contribute to unravel the dynamics that governs the observed $ν_mu$ disappearence.

hep-ph↗

arXiv2000

Violation of Equivalence Principle and Solar Neutrinos

We have updated the analysis for the solution to the solar neutrino problem by the long-wavelength neutrino oscillations induced by a tiny breakdown of the weak equivalence principle of general relativity, and obtained a very good fit to all the solar neutrino data.

hep-ph↗

arXiv2000

Three Generation Long-wavelength Vacuum Oscillation Solution to the Solar Neutrino Problem

We investigate the current status of the long-wavelength vacuum oscillation solution to the solar neutrino problem and to what extent the presence of a third neutrino can affect and modify it. Assuming that the smaller mass squared difference that can induce such oscillations, $Δm^2_{12}$, is in the range $10^{-11}-10^{-8}$ eV$^2$ and the larger one, $Δm^2_{23}$, in the range relevant to atmospheric neutrino observations, we analyze the most recent solar neutrino data coming from Homestake, SAGE, GALLEX, GNO and Super-Kamiokande experiments in the context of three neutrino generations. We include in our vacuum oscillation analysis the MSW effect in the Sun, which is relevant for some of the parameter space scrutinized. We have also performed, as an extreme exercise, the fit without Homestake data. % While we found that the MSW effect basically does not affect the best fitted parameters, it significantly modifies the allowed parameter space for $Δm^2_{12}$ larger than $\sim 3 \times 10^{-10}$ eV$^2$, in good agreement with the result obtained by A. Friedland in the case of two generations. % Although the presence of a third neutrino does not essentially improve the quality of the fit, the solar neutrino data alone can give an upper bound on $θ_{13}$, which is constrained to be less than $\sim 60^\circ$ at 95 % C.L.

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