arXiv subjects

C. Peña-Garay

Publications and source records attributed to C. Peña-Garay.

At least 19 recordsLinked to original sources

arXiv2022

Radon Mitigation Applications at the Laboratorio Subterraneo de Canfranc (LSC)

The Laboratorio Subterra neo de Canfranc (LSC) is the national hub for low radioactivity techniques and the associated scientific and technological applications. The concentration of the airborne radon is a major component of the radioactive budget in the neighborhood of the detectors. The LSC hosts a Radon Abatement System (RAS), which delivers a radon suppressed air with < 1 mBq/m3 of 222Rn. The radon content in the air is continuously monitored with an Electrostatic Radon Monitor (ERM). Measurements with the doble beta decay demonstrators NEXT-NEW and CROSS and the gamma HPGe detectors demonstrate the important reduction of the radioactive background due to the replaced air in the vicinity of the detectors. We also discuss the use of this facility in the LSC current program which includes NEXT-100, low background biology experiments and radiopure copper electroformation equipment placed in the radon-free clean room.

physics.ins-det↗

arXiv2013

Discovery potential of xenon-based neutrinoless double beta decay experiments in light of small angular scale CMB observations

The South Pole Telescope (SPT) has probed an expanded angular range of the CMB temperature power spectrum. Their recent analysis of the latest cosmological data prefers nonzero neutrino masses, mnu = 0.32+-0.11 eV. This result, if confirmed by the upcoming Planck data, has deep implications on the discovery of the nature of neutrinos. In particular, the values of the effective neutrino mass involved in neutrinoless double beta decay (bb0nu) are severely constrained for both the direct and inverse hierarchy, making a discovery much more likely. In this paper, we focus in xenon-based bb0nu experiments, on the double grounds of their good performance and the suitability of the technology to large-mass scaling. We show that the current generation, with effective masses in the range of 100 kg and conceivable exposures in the range of 500 kg year, could already have a sizable opportunity to observe bb0nu events, and their combined discovery potential is quite large. The next generation, with an exposure in the range of 10 ton year, would have a much more enhanced sensitivity, in particular due to the very low specific background that all the xenon technologies (liquid xenon, high-pressure xenon and xenon dissolved in liquid scintillator) can achieve. In addition, a high-pressure xenon gas TPC also features superb energy resolution. We show that such detector can fully explore the range of allowed effective Majorana masses, thus making a discovery very likely.

hep-ph↗

arXiv2002

On the Effect of theta_{13} on the Determination of Solar Oscillation Parameters at KamLAND

If the solution to the solar neutrino puzzle falls in the LMA region, KamLAND should be able to measure with good precision the corresponding oscillation parameters after a few years of data taking. Assuming a positive signal, we study their expected sensitivity to the solar parameters (theta_{12},Delta m^2_{21}) when considered in the framework of three-neutrino mixing after taking into account our ignorance on the mixing angle theta_{13}. We find a simple ``scaling'' dependence of the reconstructed theta_{12} range with the value of theta_{13} while the Delta m^2_{12} range is practically unaffected. Our results show that the net effect is approximately equivalent to an uncertainty on the overall neutrino flux normalization of up to sim 10 %.

hep-ph↗

arXiv2001

Update on Solar and Atmospheric Four-Neutrino Oscillations

In this talk we present the update (including the recent SNO results) of our analysis of the neutrino oscillation solutions of the solar and atmospheric neutrino problems in the framework of four-neutrino mixing where a sterile neutrino is added to the three standard ones and the mass spectra present two separated doublets. Such scenarios allow for simultaneous transitions of solar $ν_e$, as well as atmospheric $ν_μ$, into a combination of active and sterile neutrinos. We evaluate the allowed active-sterile admixture in both solar and atmospheric oscillations from the combined analysis. Our results show that, although the Super-Kamiokande data disfavour both the pure $ν_μ\toν_s$ atmospheric channel and, in combination with SNO, the pure $ν_e\toν_s$ solar channel, the result from the combined analysis still favours close-to-pure active and sterile oscillations and disfavours oscillations into a near-maximal active-sterile admixture.

hep-ph↗

arXiv2001

Solving the Solar Neutrino Puzzle with KamLAND and Solar Data

We study what will be learnt about the solar neutrino puzzle and solar neutrino oscillations once the data from the KamLAND reactor neutrino experiment (soon to become available) are combined with those from the current solar neutrino experiments. We find that, in agreement with previous estimates, if the solution to the solar neutrino puzzle falls on the LMA region, KamLAND should be able to ``pin-point'' the right solution with unprecedented accuracy after a few years of data taking. Furthermore, the light side ($θ<π/4$) can be separated from the dark side ($θ>π/4$) at the 95% confidence level (CL) for most of the LMA region allowed by the current data at the 99% CL, while the addition of the KamLAND data need not improve our ability to limit a sterile component in ``solar'' oscillations. If KamLAND does not see an oscillation signal, the solar data would point to the LOW/VAC regions, while the SMA region would still lurk at the two sigma CL, meaning we would probably have to wait for Borexino data in order to finally piece the solar neutrino puzzle.

hep-ph↗

arXiv2001

Status of the Gribov-Pontecorvo Solution to the Solar Neutrino Problem

We discuss the status of the Gribov-Pontecorvo (GP) solution to the solar neutrino problem. This solution naturally appears in bimaximal neutrino mixing and reduces the solar and atmospheric neutrino problems to vacuum oscillations of three active neutrinos. The GP solution predicts an energy-independent suppression of the solar neutrino flux. It is disfavoured by the rate of the Homestake detector, but its statistical significance greatly improves, when the chlorine rate and the boron neutrino flux are slightly rescaled, and when the Super-Kamiokande neutrino spectrum is included in the analysis. Our results show that rescaling of the chlorine signal by only 10% is sufficient for the GP solution to exist, if the boron-neutrino flux is taken 10 -- 20% lower than the SSM prediction. The regions allowed for the GP solution in the parameter space are found and observational signatures of this solution are discussed.

hep-ph↗

arXiv2001

Solar and Atmospheric Four-Neutrino Oscillations

We present an analysis of the neutrino oscillation solutions of the solar and atmospheric neutrino problems in the framework of four-neutrino mixing where a sterile neutrino is added to the three standard ones and the mass spectra presents two separated doublets. Such scenarios allow for simultaneous transitions of solar $ν_e$, as well as atmospheric $ν_μ$, into active and sterile neutrinos controlled by the additional mixing angles $\vartheta_{23}$ and $\vartheta_{24}$, and they contain as limiting cases the pure solar $ν_e$-active and $ν_e$-sterile neutrino oscillations, and the pure atmospheric $ν_μ\toν_s$ and $ν_μ\toν_τ$ oscillations, respectively. We evaluate the allowed active-sterile admixture in both solar and atmospheric oscillations from the combined analysis. Our results show that, although the Super-Kamiokande data disfavour both the pure $ν_μ\toν_s$ atmospheric channel and the pure $ν_e\toν_s$ solar channel, the result from the combined analysis still favours close-to-pure active and sterile oscillations and disfavours oscillations into a near-maximal active-sterile admixture.

hep-ph↗

arXiv2001

Four-Neutrino Oscillations at SNO

We discuss the potential of SNO to constraint the four-neutrino mixing schemes favoured by the results of all neutrino oscillations experiments. These schemes allow simultaneous transitions of solar $ν_e's$ into active $ν_μ$'s, $ν_τ$'s and sterile $ν_s$ controlled by the additional parameter $\cos^2(\vartheta_{23}) \cos^2(\vartheta_{24})$ and they contain as limiting cases the pure $ν_e$-active and $ν_e$-sterile neutrino oscillations. We first obtain the solutions allowed by the existing data in the framework of the BP00 standard solar model and quantify the corresponding predictions for the CC and the NC/CC event ratios at SNO for the different allowed regions as a function of the active-sterile admixture. Our results show that some information on the value of $\cos^2(\vartheta_{23}) \cos^2(\vartheta_{24})$ can be obtained by the first SNO measurement of the CC ratio, while considerable improvement on the knowledge of this mixing will be achievable after the measurement of the NC/CC ratio.

hep-ph↗

arXiv2001

Zenith angle distributions at Super-Kamiokande and SNO and the solution of the solar neutrino problem

We have performed a detailed study of the zenith angle dependence of the regeneration factor and distributions of events at SNO and SK for different solutions of the solar neutrino problem. In particular, we discuss oscillatory behaviour and the synchronization effect in the distribution for the LMA solution, the parametric peak for the LOW solution, etc.. Physical interpretation of the effects is given. We suggest a new binning of events which emphasizes distinctive features of zenith angle distributions for the different solutions. We also find the correlations between the integrated day-night asymmetry and the rates of events in different zenith angle bins. Study of these correlations strengthens the identification power of the analysis.

hep-ph↗

arXiv2000

Four--Neutrino Oscillations at SNO

We discuss the potential of the Sudbury Neutrino Observatory (SNO) to constraint the four--neutrino mixing schemes favoured by the results of all neutrino oscillations experiments. Our results show that some information on the value of $\cos^2(\vartheta_{23}) \cos^2(\vartheta_{24})$ can be obtained by the first SNO measurement of the CC ratio, while considerable improvement on the knowledge of this mixing will be achievable after the measurement of the NC/CC ratio.

hep-ph↗

arXiv2000

Global three-neutrino oscillation analysis of neutrino data

A global analysis of the solar, atmospheric and reactor neutrino data is presented in terms of three-neutrino oscillations. We include the most recent solar neutrino rates of Homestake, SAGE, GALLEX and GNO, as well as the recent 1117 day Super-Kamiokande data sample, including the recoil electron energy spectrum both for day and night periods and we treat in a unified way the full parameter space for oscillations, correctly accounting for the transition from the matter enhanced (MSW) to the vacuum oscillations regime. Likewise, we include in our description conversions with $θ_{12} > π/4$. For the atmospheric data we perform our analysis of the contained events and the upward-going $ν$-induced muon fluxes, including the previous data samples of Frejus, IMB, Nusex, and Kamioka experiments as well as the full 71 kton-yr (1144 days) Super-Kamiokande data set, the recent 5.1 kton-yr contained events of Soudan2 and the results on upgoing muons from the MACRO detector. We first present the allowed regions of solar and atmospheric oscillation parameters $θ_{12}$, $Δm^2_{21}$ and $θ_{23}$, $Δm^2_{32}$, respectively, as a function of $θ_{13}$ and determine the constraints from atmospheric and solar data on the mixing angle $θ_{13}$, common to solar and atmospheric analyses. We also obtain the allowed ranges of parameters from the full five-dimensional combined analysis of the solar, atmospheric and reactor data.

hep-ph↗

arXiv2000

Phenomenology of Maximal and Near-Maximal Lepton Mixing

We study the phenomenological consequences of maximal and near-maximal mixing of the electron neutrino with other ($x$=tau and/or muon) neutrinos. We describe the deviations from maximal mixing in terms of a parameter $ε\equiv1-2\sin^2θ_{ex}$ and quantify the present experimental status for $|ε|<0.3$. We find that the global analysis of solar neutrino data allows maximal mixing with confidence level better than 99% for $10^{-8}$ eV$^2\lsimΔm^2\lsim2\times10^{-7}$ eV$^2$. In the mass ranges $Δm^2\gsim 1.5\times10^{-5}$ eV$^2$ and $4\times10^{-10}$ eV$^2\lsimΔm^2\lsim2\times10^{-7}$ eV$^2$ the full interval $|ε|<0.3$ is allowed within 4$σ$(99.995 % CL). We suggest ways to measure $ε$ in future experiments. The observable that is most sensitive to $ε$ is the rate [NC]/[CC] in combination with the Day-Night asymmetry in the SNO detector. With theoretical and statistical uncertainties, the expected accuracy after 5 years is $Δε\sim 0.07$. We also discuss the effects of maximal and near-maximal $ν_e$-mixing in atmospheric neutrinos, supernova neutrinos, and neutrinoless double beta decay.

hep-ph↗

arXiv2000

Global and Unified Analysis of Solar Neutrino Data

We discuss the status of the solutions of the solar neutrino problem in terms of oscillations of $ν_e$ into active or sterile neutrinos. We present the results of a global fit to the full data set corresponding to the latest data presented at the $ν$-2000 conference. We show the possible solutions in the full parameter space including both MSW and vacuum, as well as quasi-vacuum oscillations (QVO) and matter effects for mixing angles in the second octant (the so called dark side). Our conclusion is that from the statistical point of view, all solutions for oscillations into active neutrinos: LMA, LOW, SMA and the QVO solutions are acceptable since they all provide a reasonable GOF to the full data set. The same holds for the SMA solution for oscillations into sterile neutrinos. LMA and LOW-QVO solutions for oscillations into active neutrinos seem slightly favoured over SMA solutions for oscillations into active or sterile neutrinos. We also analyze the dependence of these conclusions on the uncertainty of the SSM $^8$B flux and on the removal of the data from one of the experimental rates. We also present the results in the framework of four neutrino oscillations which allows for oscillations into a state which is a combination of active and sterile neutrino.

hep-ph↗

arXiv2000

MSW Solutions to the Solar Neutrino Problem in Presence of Noisy Matter Density Fluctuations

We study the effect of random matter density fluctuations in the sun on resonant neutrino conversion in matter by solving numerically the evolution equation for the neutrino system including the full effect of the random matter density fluctuations of given amplitude and correlation length. In order to establish the possible effect on the MSW solutions to the solar neutrino problem we perform a global analysis of all the existing observables including the measured total rates as well as the Super-Kamiokande measurement on the time dependence of the event rates during the day and night and the recoil electron energy spectrum. We find the effects of random noise to be larger for small mixing angles and they are mostly important for correlation lengths in the range few 100 km $\lesssim L_0\lesssim$ few 1000 km. They can be understood as due to a parametric resonance occuring when the phase acquired by the oscillating neutrino state on one fluctuation length L_0 is a multiple of 2$π$. We find that this resonant parametric condition is mainly achieved for low energy neutrinos such as the pp-neutrinos and therefore its effect is mostly seen on the total event rates while the other Super-Kamiokande observables are very marginally sensitive to the presence of noise due to the higher energy threshold.

hep-ph↗

arXiv2000

On the Size of the Dark Side of the Solar Neutrino Parameter Space

We present an analysis of the MSW neutrino oscillation solutions of the solar neutrino problem in the framework of two-neutrino mixing in the enlarged parameter space $(Δm^2, \tan^2θ)$ with $θ\in (0,\fracπ{2})$. Recently, it was pointed out that the allowed region of parameters from a fit to the measured total rates can extend to values $θ\geq \fracπ{4}$ (the so called ``dark side'') when higher confidence levels are allowed. The purpose of this letter is to reanalize the problem including all the solar neutrino data available, to discuss the dependence on the statistical criteria in the determination of the CL of the ``dark side'' and to extract the corresponding limits on the largest mixing allowed by the data. Our results show that when the Super-Kamiokande data on the zenith angle distribution of events and the spectrum information is included, the regions extend more into the dark side.

hep-ph↗

arXiv2000

Four--Neutrino Oscillation Solutions of the Solar Neutrino Problem

We present an analysis of the neutrino oscillation solutions of the solar neutrino problem in the framework of four-neutrino mixing where a sterile neutrino is added to the three standard ones. We perform a fit to the full data set corresponding to the 825-day Super-Kamiokande data sample as well as to Chlorine, GALLEX and SAGE and Kamiokande experiments. In our analysis we use all measured total event rates as well as all Super-Kamiokande data on the zenith angle dependence and the recoil electron energy spectrum. We consider both transitions via the Mikheyev-Smirnov-Wolfenstein (MSW) mechanism as well as oscillations in vacuum (just-so) and find the allowed solutions for different values of the additional mixing angles. This framework permits transitions into active or sterile neutrinos controlled by the additional parameter $\cos^2(\vartheta_{23}) \cos^2(\vartheta_{24})$ . We discuss the maximum allowed values of this additional mixing parameter for the different solutions.

hep-ph↗

arXiv2000

Neutrino Masses and Mixing one Decade from Now

We review the status of neutrino masses and mixings in the light of the solar and atmospheric neutrino data. The result from the LSND experiment is also considered. We discuss the present knowledge and the expected sensitivity to the neutrino mixing parameters in the simplest schemes proposed to reconcile these data some of which include a light sterile neutrino in addition to the three standard ones.

hep-ph↗

arXiv2000

Status of the MSW Solutions to the Solar Neutrino Problem

In this talk we present the results of an updated global analysis of two-flavor MSW solutions to the solar neutrino problem in terms of conversions of $ν_e$ into active or sterile neutrinos including the the full data set corresponding to the 825-day Super-Kamiokande data sample as well as to Chlorine, GALLEX and SAGE experiments.

hep-ph↗