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A. M. Gago

Publications and source records attributed to A. M. Gago.

85 records · Page 5Linked to original sources
arXiv2005

On the Parameters determining the Neutrino Flux from observed Active Galactic Nuclei

Extrapolating from a sample of 39 AGNs, we examine the impact on the total number of high energy muon-neutrino induced events (PeV-EeV) expected in IceCube (a 1Km^3 ``neutrino telescope''), due to variations in different parameters involved in the neutrino flux, such as the emission region geometry, the estimation models and distributions of the Doppler factor and the variability time. This work has been done taking into account different limits of the extragalactic neutrino flux. Among our conclusions, we find, in the case of the largest variability time, that the cylindrical geometry hypothesis for the emission region, produce a separation of 3 sigma in the total number of events relative to the spherical hypothesis. In addition, for similar choices of the burst time, spherical geometry and for the upper neutrino flux bound, we obtain a separation of 2.5 sigma in the total number of events, for some of the Doppler factor estimations. These differences are undistinguishable for other input values.

astro-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.

hep-ph↗
arXiv1999

Testing Flavor Changing Neutrino Interactions in Long Baseline Experiments

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.

hep-ph↗
arXiv1999

CP Violation in Vacuum Neutrino Oscillation Experiments

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.

hep-ph↗