Light sterile neutrinos with a mass around 1 eV have been studied for many years as a possible explanation of the so called short-baseline neutrino oscillation anomalies. Recently, several neutrino oscillation experiments reported preferences for non-zero values of the mixing angles and squared mass differences for active-sterile mixing, which however are not always in agreement. I will review our current knowledge on the light sterile neutrino in the 3+1 model, starting with a separate discussion on the status of the most relevant searches and then analyzing the problems that arise when combining different probes in a global fit.
This is an extension of estimates of the probability of $ν$ to $e$ neutrino oscillation with one sterile neutrino to three sterile neutrinos, using a 6x6 matrix. Since the mixing angle for only one sterile neutrino has been experimentally determined, we estimate the $ν$ to $e$ neutrino oscillation probability with different mixing angles for two of the sterile neutrinos.
This work estimates the probability of $μ$ to $e$ neutrino oscillation with two sterile neutrinos using a 5x5 U-matrix, an extension of the previous estimate with one sterile neutrino and a 4x4 U-matrix. The sterile neutrino-active neutrino mass differences and the mixing angles of the two sterile neutrinos with the three active neutrinos are taken from recent publications, and the oscillation probability for one sterile neutrino is compared to the previous estimate.
This brief report is an extension of a prediction of neutrino oscillation with a sterile neutrino using parameters of the sterile neutrino mass and mixing angle recently extracted from experiment.
Recently neutrino oscillation experiments have shown that it is very likely that there are one or two sterile neutrinos. In this review neutrino oscillations with one, two, three sterile and three active neutrinos, and parameters that are consistent with experiments, are reviewed.
It is shown that a 1980 proposal to search for heavy sterile neutrinos by observing the energy of the associated lepton in weak decays rests on an questionable assumption, and that the possibility of such a detection might be inconsistent with the observability of neutrino oscillations.
Using a 3 + 1 neutrino model with one sterile and the three standard active neutrinos with a 4x4 unitary transformation matrix, U, relating flavor to mass neutrino states, the probability of $ν_μ$ to $ν_e$ transition is estimated using sterile-active neutrino masses determined by MiniBooNE and other experiments and sterile-active neutrino angles in the 4x4 U matrix.
Neutrino asymmetry generation from active-sterile neutrino oscillations in the early Universe has different important cosmological effects. We discuss its basic features and present recent results on the borders of the generation for mixing angles $\sin^2 2θ_0\leq 10^{-7}$.
Sterile neutrino conversion in meter scale baselines can be sensitively probed using monoenergetic, sub-MeV, flavor pure e-neutrinos from an artificial MCi source and the unique technology of LENS designed to oberve the low energy solar neutrino spectrum via tagged CC e-neutrino capture in 115-In. Active-sterile oscillations can be directly observed in the granular LENS detector itself to critically test and extend resuls of short baseline accelerator and reactor experiments.
Anomalies in several short-baseline neutrino oscillation experiments suggest the possible existence of sterile neutrinos at about eV scale having appreciable mixing with the already known three neutrinos. We find that if such a light sterile neutrino exists, through a combined study of the leptonic decays of $μ^-$, $τ^-$, $π^-$ and $K^-$, some semi-leptonic decays of $τ^-$ and the invisible decay width of the $Z$ boson, it is possible to constrain the relevant mixing matrix elements. Furthermore, we compare the constraints, derived by using the method presented here, with the experimental resu…
The question of the existence of light sterile neutrinos is of great interest in many areas of particle physics, astrophysics, and cosmology. Furthermore, should the MiniBooNE experiment at Fermilab confirm the LSND oscillation signal, then new measurements are required to identify the mechanism responsible for these oscillations. Possibilities include sterile neutrinos, CP or CPT violation, variable mass neutrinos, Lorentz violation, and extra dimensions. In this paper, we consider an experiment at a stopped pion neutrino source to determine if active-sterile neutrino oscillations with delta-…
Sterile neutrino models with new gauge interactions in the sterile sector are phenomenologically interesting since they can lead to novel effects in neutrino oscillation experiments, in cosmology and in dark matter detectors, possibly even explaining some of the observed anomalies in these experiments. Here, we use data from neutrino oscillation experiments, in particular from MiniBooNE, MINOS and solar neutrino experiments, to constrain such models. We focus in particular on the case where the sterile sector gauge boson $A'$ couples also to Standard Model particles (for instance to the baryon…
The matter effects for solar neutrino oscillations are studied in a general scheme with an arbitrary number of sterile neutrinos, without any constraint on the mixing, assuming only a realistic hierarchy of neutrino squared-mass differences in which the smallest squared-mass difference is effective in solar neutrino oscillations. The validity of the analytic results are illustrated with a numerical solution of the evolution equation in three examples of the possible mixing matrix in the simplest case of four-neutrino mixing.
A relic lepton asymmetry orders of magnitude bigger than the baryon one may hide in the relic neutrino background. No direct theoretical or experimental limitations on its magnitude and sign are known. Indirect cosmological constraints exist ranging from $|L|<0.01$ to $L<10$. We discuss a BBN model with late electron-sterile neutrino oscillations which is a fine leptometer - it is capable of feeling extremely small relic lepton asymmetry - $|L|>10^{-8}$. This sensitivity is achieved through the influence of such small $L$ on the neutrino oscillations, suppressing or enhancing them, and thus ch…
I summarize here the results of a global fit to the full data set corresponding to 33.0 kt-yr of data of the Super-Kamiokande experiment as well as to all other experiments in order to compare the active-active and active-sterile neutrinos oscillation channels to the atmospheric neutrino anomaly.
We develop a thorough description of neutrino oscillations in a magnetized protoneutron star, based on a resonance layer for neutrinos with different momentum directions. We apply our approach to the calculation of the asymmetry in the neutrino emission during the birth of a neutron star and the pulsar acceleration in the case of an active-sterile neutrino resonant conversion. The observed velocities can be obtained with the magnetic fields expected in the interior of a protoneutron star, for sterile neutrino masses of the order of KeV and small mixing angles.
The scenario of baryogenesis through GeV-scale sterile neutrino oscillations is governed by non-linear differential equations for the time evolution of a sterile neutrino density matrix and Standard Model lepton and baryon asymmetries. By employing up-to-date rate coefficients and a non-perturbatively estimated Chern-Simons diffusion rate, we present a numerical solution of this system, incorporating the full momentum and helicity dependences of the density matrix. The density matrix deviates significantly from kinetic equilibrium, with the IR modes equilibrating much faster than the UV modes.…
The neutrino oscillation probabilities in vacuum and matter are discussed, considering the framework of three active and one light sterile neutrinos. We study in detail the rephasing invariants and CP asymmetry observables, and investigate the four-neutrino oscillations in long-baseline neutrino experiments, such as DUNE, NO$ν$A and T2HK. Our results show that the matter effect enhances quite a significantly the oscillation probabilities of electron neutrino and electron antineutrino appearance channels within a certain energy range, while no considerable change arises in the CP asymmetry anal…
We suggest the possibility that the anomalies observed in the LSND experiment and the Gallium radioactive source experiments may be due to neutrino oscillations generated by a large squared-mass difference of about 20 - 30 eV^2. We consider the simplest 3+1 four-neutrino scheme that can accommodate also the observed solar and atmospheric neutrino oscillations. We show that, in this framework, the disappearance of nu_e and nu_mu in short-baseline neutrino oscillation experiments is mainly due to active-sterile transitions. The implications of the first MiniBooNE results, appeared after the comp…
We study the matter effects for solar neutrino oscillations in a general scheme, without any constraint on the number of sterile neutrinos and the mixing matrix elements, only assuming a realistic hierarchy of neutrino squared-mass differences in which the smallest squared-mass difference is effective in solar neutrino oscillations. The validity of the analytic results are illustrated with a numerical solution of the evolution equation in the simplest case of four-neutrino mixing with the realistic matter density profile inside the Sun.
We review the status of light sterile neutrino searches, motivated by the original Short BaseLine (SBL) anomalies. Here, we discuss how sterile neutrino properties can be constrained by different types of neutrino oscillation experiments (considering appearance or disappearance probes in different oscillation channels) and non-oscillation measurements. These latter include experiments aiming at obtaining a value for the absolute scale of neutrino masses ($β$ decay probes) and the indirect constraints that we could obtain from cosmological observations.
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 atmosph…
Sterile neutrinos are one candidate to explain anomalies in neutrino oscillations. The mass-difference-driving oscillation between flavors can be probed only within specific combinations of baseline and flight energy. For a neutrino whose mass is completely unknown, it is necessary to scan all available ranges in spectrum and all accessible baselines. Here, we present four-neutrino analysis of the results announced by RENO and Daya Bay, which performed the definitive measurements of $θ_{13}$ based on the disappearance of the inverse-beta-decay antineutrino at km-order baselines. Our results wi…
We investigate resonant active-sterile neutrino oscillations emergent from the interplay between matter, CPT- and Lorentz-violating coefficients with different energy dependences. Novel and experimentally accessible resonant neutrino oscillation phenomenologies are predicted and possible implications for observed, but yet unexplained, neutrino oscillation anomalies such as LSND and MiniBooNE are discussed.
We have provided a numerical study of the influence of the resonant active-sterile neutrino oscillations between electron and sterile neutrinos, on the primordial production of helium-4. The evolution of the neutrino ensembles was followed selfconsistently with the evolution of the nucleons, using exact kinetic equations for the neutrino density matrix and the nucleon number densities in momentum space, from the time of neutrino decoupling till the freeze-out of nucleons at 0.3 MeV. The exact kinetic approach enabled us to study precisely the neutrino depletion, spectrum distortion and neutrin…
In view of the recent results from the MiniBooNE experiment we revisit the global neutrino oscillation fit to short-baseline neutrino data by adding one or two sterile neutrinos with eV-scale masses to the three Standard Model neutrinos, and for the first time we consider also the global fit with three sterile neutrinos. Four-neutrino oscillations of the (3+1) type have been only marginally allowed before the recent MiniBooNE results, and become even more disfavored with the new data (at the level of $4σ$). In the framework of so-called (3+2) five-neutrino mass schemes we find severe tension b…
Recent neutrino oscillation results have evoked renewed interest in sterile neutrino oscillation models. This paper reviews the data from MiniBooNE and short-baseline reactor antineutrino experiments within the context of sterile neutrinos. The results are incorporated into combined fits to test the viability of sterile neutrino oscillation models, which are later expanded to address matter effects. Finally, future experiments that can resolve the questions that have been raised are discussed.
Light sterile neutrinos contributions both for active neutrinos oscillations and neutrinoless double beta decay characteristics are estimated in the framework of the phenomenological model with three active and three sterile neutrinos assuming the Majorana nature of neutrino. Appearance and survival probabilities for active neutrinos with contributions of eV-sterile neutrinos in application to the short-baseline anomalies in neutrino data are obtained at the same test values of the model parameters. Modified graphical dependences for the survival probability of electron neutrinos/antineutrinos…
The down-going atmospheric ν_μ and {\bar{ν_μ}} fluxes can be significantly altered due to the presence of eV^2-scale active-sterile oscillations. We study the sensitivity of a large Liquid Argon detector and a large magnetized iron detector (like the proposed ICAL at INO) to these oscillations. Such oscillations are indicated by results from LSND, and more recently, from MiniBooNE and from reanalyses of reactor experiments following recent recalculations of reactor fluxes. There are other tentative indications of the presence of sterile states in both the νand {\barν} sectors as well. Using th…
New parameter region in sterile neutrino searches: a scenario to alleviate cosmological neutrino mass bound and its testability at oscillation experiments
In this paper, we study the effect of conversion of super-light sterile neutrino (SLSN) to electron neutrino in matter like that of the Earth. In the Sun the resonance conversion between SLSN and electron neutrino via the neutral current is suppressed due to the smallness of neutron number. On the other hand, neutron number density can play an important role in the Earth, making the scenario of SLSN quite interesting. The effect of CP-violating phases on active-SLSN oscillations is also discussed. Reactor neutrino experiments with medium or short baseline may probe the scenario of SLSN.
Standard active--sterile neutrino oscillations do not provide a satisfactory description of the LSND evidence for neutrino oscillations together with the constraints from MiniBooNE and other null-result short-baseline oscillation experiments. However, if the mass or the mixing of the sterile neutrino depends in an exotic way on its energy all data become consistent. I explore the phenomenological consequences of the assumption that either the mass or the mixing scales with the neutrino energy as $1/E_ν^r (r > 0)$. Since the neutrino energy in LSND is about 40 MeV, whereas MiniBooNE operates at…
A phenomenological model with active and sterile neutrinos is used for calculations of neutrino oscillation characteristics at the normal mass hierarchy of active neutrinos. Taking into account the contributions of sterile neutrinos, appearance and survival probabilities for active neutrinos are calculated. Modified graphical dependencies for the probability of appearance of electron neutrinos/antineutrinos in muon neutrino/antineutrino beams as a function of the ratio of the distance to the neutrino energy and other model parameters are obtained. It is shown that in the case of a certain type…
We study two possible explanations for short baseline neutrino oscillation anomalies, such as the LSND and MiniBooNE anti-neutrino data, and for the reactor anomaly. The first scenario is the mini-seesaw mechanism with two eV-scale sterile neutrinos. We present both analytic formulas and numerical results showing that this scenario could account for the short baseline and reactor anomalies and is consistent with the observed masses and mixings of the three active neutrinos. We also show that this scenario could arise naturally from an effective theory containing a TeV-scale VEV, which could be…
We address the phenomenology of light sterile neutrinos, with emphasis on short-baseline neutrino oscillations. After a review of the observed short-baseline neutrino oscillation anomalies, we discuss the global fit of the data and the current appearance-disappearance tension. We also review briefly the effects of light sterile neutrinos in $β$ decay, neutrinoless double-$β$ decay and cosmology. Finally, we discuss the future perspective in the search for the effects of eV-scale sterile neutrinos.
We show how active-sterile neutrino oscillations in the early Universe can play an interesting role in explaining the current observations of CMBR anisotropies and light element abundances. We describe different possible phenomenological scenarios in the interpretation of present data and how active-sterile neutrino oscillations can provide a viable theoretical framework.
We show that in a reactor disappearance oscillation experiment the sensitivity to the mixing parameter can be substantially improved for $(1 - 5\cdot10^{-4}) eV^{2}$ mass parameter range which includes both the LSND and the atmospheric neutrino oscillation regions. The objectives are: to search for the sterile neutrinos and to get a better understanding of the atmospheric neutrino oscillation mechanism. The parameters of the underground (600 m.w.e.) Krasnoyarsk reactor and data from the CHOOZ reactor oscillation experiment are used to estimate the effect and background rates.
The current case for atmospheric $ν_μ$ oscillations into active or sterile neutrinos is reviewed. It is argued that neither the study of neutral current events at Super-Kamiokande, nor the information obtained from future long baseline experiments might be sufficient to unambigously decide between these two scenarios. However, a combination of these results with the results from future short or intermediate baseline $τ$ appearance experiments would clearly resolve most of the remaining ambiguities. This conclusion does not strongly depend on whether the results from LSND will be confirmed or n…
Ordinary-sterile neutrino oscillations can generate a significant lepton number asymmetry in the early Universe. We study this phenomenon in detail. We show that the dynamics of ordinary-sterile neutrino oscillations in the early Universe can be approximately described by a single integro-differential equation which we derive from both the density matrix and Hamiltonian formalisms. This equation reduces to a relatively simple ordinary first order differential equation if the system is sufficiently smooth (static limit). We study the conditions for which the static limit is an acceptable approx…
If Nature has chosen the vacuum oscillation solution to the Solar neutrino puzzle, a key theoretical challenge is to understand the extreme smallness of the $Δm^2_{ν_e-ν_X}$ ($\sim 10^{-10} eV^2$) required for the purpose. We find that in a class of models such as [SU(3)]^3 or its parent group E_6, which contain one sterile neutrino, $ν_{is}$ for each family, the $Δm^2_{ν_i-ν_{is}}$ is proportional to the cube of the lepton Yukawa coupling. Therefore fitting the atmospheric neutrino data then predicts the $ν_e-ν_{es}$ mass difference square to be $\sim (\frac{m_e}{m_μ})^3 Δm^2_{atmos}$, where …
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 re…
We investigate the ability of the Short Baseline Neutrino (SBN) experimental program at Fermilab to test the globally-allowed (3+$N$) sterile neutrino oscillation parameter space. We explicitly consider the globally-allowed parameter space for the (3+1), (3+2), and (3+3) sterile neutrino oscillation scenarios. We find that SBN can probe with $5σ$ sensitivity more than 85\%, 95\% and 55\% of the parameter space currently allowed at 99\% confidence level for the (3+1), (3+2) and (3+3) scenarios, respectively. In the case of the (3+2) and (3+3) scenarios, CP-violating phases appear in the oscilla…
We investigate the extent to which leptonic CP-violation in (3+2) sterile neutrino models leads to different oscillation probabilities for $\barν_μ\to\barν_e$ and $ν_μ\toν_e$ oscillations at MiniBooNE. We are using a combined analysis of short-baseline (SBL) oscillation results, including the LSND and null SBL results, to which we impose additional constraints from atmospheric oscillation data. We obtain the favored regions in MiniBooNE oscillation probability space for both (3+2) CP-conserving and (3+2) CP-violating models. We further investigate the allowed CP-violation phase values and the …
We derive the neutrino oscillation probabilities including sterile neutrinos by using the Dirac equation. If neutrinos have both the Dirac and the Majorana mass terms, left-handed neutrino $ν_L$ and right-handed anti-neutrino $ν_R^c$ enter the same multiplet and can transfer each other. Sterile neutrinos have been introduced by hand as the fourth generation neutrino in many papers, however, we can understand sterile neutrinos naturally in the framework of three generations. We also point out that the oscillations into sterile neutrinos strongly suggest the existence of both the Dirac and the M…
The smallness of the $θ_{13}$ mixing angle as observed in neutrino oscillation experiments can be understood through an approximated $μ- τ$ exchange symmetry in the neutrino mass matrix. Using recent oscillation neutrino data, but assuming no \textit{CP} violation, we study $μ-τ$ breaking parameter space to establish the conditions under which such a breaking could have a perturbative origin. According to the so-obtained conditions, we suggest that a sterile neutrino, matching LSND/MiniBooNE neutrino oscillation results, could provide the necessary ingredients to properly fix atmospheric and $…
Active-sterile neutrino mixing is known to affect the neutrino oscillation probabilities at both short as well as long-baselines. In particular, constraints on active-sterile neutrino oscillation parameters can be obtained from long-baseline experiments such as T2HK and DUNE. We present here existence of fake solution in the appearance channel for the 3+1 scenario at long-baseline experiments. We show that the appearance probability is same for values of $Δm_{41}^2$ for which the fast oscillations are averaged out and for $Δm_{41}^2=(1/2)Δm_{31}^2$. The fake solution does not appear for the di…
DUNE (Deep Underground Neutrino Experiment) is a proposed long-baseline neutrino experiment in the US with a baseline of 1300 km from Fermi National Accelerator Laboratory (Fermilab) to Sanford Underground Research Facility, which will house a 40 kt Liquid Argon Time Projection Chamber (LArTPC) as the far detector. The experiment will also have a fine grained near detector for accurately measuring the initial fluxes. We show that the energy range of the fluxes and baseline of the DUNE near detector is conducive for observing $ν_μ\to ν_e$ oscillations of $Δm^2 \sim$ eV$^2$ scale sterile neutrin…
Starting from operator equations of motion and making arguments based on a separation of time scales, a set of equations is derived which govern the non-equilibrium time evolution of a GeV-scale sterile neutrino density matrix and active lepton number densities at temperatures T > 130 GeV. The density matrix possesses generation and helicity indices; we demonstrate how helicity permits for a classification of various sources for leptogenesis. The coefficients parametrizing the equations are determined to leading order in Standard Model couplings, accounting for the LPM resummation of 1+n <-> 2…
We investigate adding two sterile neutrinos to resolve the apparent tension existing between short-baseline neutrino oscillation results and CPT-conserving, four-neutrino oscillation models. For both (3+1) and (3+2) models, the level of statistical compatibility between the combined dataset from the null short-baseline experiments Bugey, CHOOZ, CCFR84, CDHS, KARMEN, and NOMAD, on the one hand; and the LSND dataset, on the other, is computed. A combined analysis of all seven short-baseline experiments, including LSND, is also performed, to obtain the favored regions in neutrino mass and mixing …
We extend a simple and compact method for calculating the three flavor neutrino oscillation probabilities in uniform matter density to schemes with sterile neutrinos, with favorable features inherited. The only constraint of the extended method is that the scale of the matter potential is not significantly larger than the atmospheric $Δm^2$, which is satisfied by all the running and proposed accelerator oscillation experiments. Degeneracy of the zeroth order eigensystem around solar and atmospheric resonances are resolved. Corrections to the zeroth order results are restricted to no larger tha…
In a scenario with two almost mass degenerate heavy sterile Majorana neutrinos with a mass $\sim 1$ GeV, we present the semileptonic decay widths of heavy charged pseudoscalars such as $B$ mesons, either lepton-number-violating ($B^{\pm} \to μ^{\pm} e^{\pm} π^{\mp}$), or lepton-number-conserving ($B^{\pm} \to μ^{\pm} e^{\mp} π^{\pm}$), mediated by such on-shell neutrinos. It had been explained in the literature that such decays may be eventually detected, and that they can present even detectable CP violation effects. In this work we point out that, in addition, such decays may present detecta…
This is a pedagogical introduction to the main concepts of the sterile neutrino - a hypothetical particle, coined to resolve some anomalies in neutrino data and retain consistency with observed widths of the $W$ and $Z$ bosons. We briefly review existing anomalies and the oscillation parameters that best describe these data. We discuss in more detail how sterile neutrino can be observed, as well as the consequences of its possible existence. In particular, we pay attention to a possible loss of coherence in a model of neutrino oscillations with sterile neutrinos, where this effect might be of …
The existence of light sterile neutrinos is a long standing question for particle physics. Several experimental ``anomalies'' could be explained by introducing ~eV mass scaled light sterile neutrinos. Many experiments are actively hunting for such light sterile neutrinos through neutrino oscillation. For long baseline experiments, matter effect needs to be treated carefully for precise neutrino oscillation probability calculation. However, it is usually time-consuming or analytical complexity. In this manuscript we adopt the Jacobi-like method to diagonalize the Hermitian Hamiltonian matrix an…
We examine the MiniBooNE neutrino, MiniBooNE antineutrino and LSND antineutrino data sets in a two-neutrino $\stackrel{\tiny{(-)}}ν_μ\rightarrow\stackrel{\tiny{(-)}}ν_e$ oscillation approximation subject to non-standard matter effects. We assume those effects can be parametrized by an $L$-independent effective potential, $V_s=\pm A_s$, experienced only by an intermediate, non-weakly-interacting (sterile) neutrino state which we assume participates in the oscillation, where $+/-$ corresponds to neutrino/antineutrino propagation. We discuss the mathematical framework in which such oscillations a…
A scenario based on the TopFlavor model is presented to explain the origin of a light sterile neutrino as indicated by all combined neutrino oscillation experiments. The model is phenomenologically well motivated and compatible with all available low-energy data. The derived nuetrino mass matrix can qualitatively explain the observed hierarchy in the neutrino mass splittings as indicated by the neutrino oscillation data. Numerical results are obtained for special cases.
Flux-integrated semiexclusive cross sections for charged-current quasielastic and neutral-current elastic neutrino scattering off ${}^{40}$Ar and a sterile neutrino oscillation study
A generalized phenomenological (3 + 2 + 1)-model with three active and three sterile neutrinos is considered for the calculation of the neutrino oscillation characteristics at normal mass hierarchy of active neutrinos and significant splitting between the mass of one sterile neutrino and the masses of other two sterile neutrinos. A new parametrization and a certain form of the general neutrino mixing matrix for active and sterile neutrinos are suggested taking into account the possible violation of CP invariance in the lepton sector. The test values of the neutrino masses and the mixing parame…
A large lepton asymmetry could be generated in the Early Universe by oscillations of active to sterile neutrinos with a small mixing angle sin 2 θ< 10^-2. The final order of magnitude of the lepton asymmetry ηis mainly determined by its growth in the last stage of evolution when the MSW resonance dominates the kinetic equations. In this paper we present a simple way of calculating the maximum possible lepton asymmetry which can be created. Our results are in good agreement to previous calculations. Furthermore, we find that the growth of asymmetry does not obey any particular power law. We fin…
In this work, we present a realistic analysis of the potential of the present-day reactor experiments Double Chooz, Daya Bay and RENO for probing the existence of sterile neutrinos. We present exclusion regions for sterile oscillation parameters for each of these experiments, using simulations with realistic estimates of systematic errors and detector resolutions, and compare the sterile parameter sensitivity regions we obtain with the existing bounds from other reactor experiments. We find that these experimental set-ups give significant bounds on the parameter Θ_{ee} especially in the low st…
