We have analyzed the atmospheric neutrino data to study the octant of $θ_{23}$ and the precision of the oscillation parameters for a large Iron CALorimeter (ICAL) detector. The ICAL being a tracking detector has the ability to measure the energy and the direction of the muon with high resolution. From bending of the track in magnetic field it can also distinguish its charge. We have generated events by Nuance and then considered only the muons (directly measurable quantities) produced in charge current interactions in our analysis. This encounters the main problem of wide resolutions of energy and baseline. The energy-angle correlated two dimensional resolution functions are used to migrate the energy and the zenith angle of the neutrino to those of the muon. A new type of binning has been introduced to get better reflection of the oscillation pattern in chi-square analysis. Then the marginalization of the $χ^2$ over all parameters has been carried out for neutrinos and anti-neutrinos separately. We find that the measurement of $θ_{13}$ is possible at a significant precision with atmospheric neutrinos. The precisions of $Δm_{32}^2$ and $\sin^2θ_{23}$ are found $\sim$ 8% and 38%, respectively, at 90% CL. The discrimination of the octant as well as the deviation from maximal mixing of atmospheric neutrinos are also possible for some combinations of ($θ_{23}, ~θ_{13}$). We also discuss the impact of the events at near horizon on the precision studies.
We perform realistic simulations of the current and future long baseline experiments such as T2K, NO$ν$A, DUNE and T2HK in order to determine their ultimate potential in probing neutrino oscillation parameters. We quantify the potential of these experiments to underpin the octant of the atmospheric angle $θ_{23}$ as well as the value and sign of the CP phase $δ_{CP}$.
In the wake of the SuperKamiokande announcement of atmospheric neutrino oscillations which favor the large mixing of $ν_μ$ with $ν_τ$, there is considerable theoretical activity towards a possible understanding of the solar neutrino deficit also in terms of the mixing of $ν_e$ with the other two neutrinos. A specific dynamical model is presented here for the first time which naturally chooses the large (small) mixing solution to atmospheric (solar) neutrino oscillations.
We consider the effects of Planck scale on four flavour neutrino mixings. The gravational interaction at $M_{x}=M_{\rm planck}$, we find that for degenerate neurino mass order, the Planck scale effects changes the mixing angle $θ'_{23}$, $θ'_{12}$ values and $θ'_{13}$, $θ'_{14}$, $θ'_{34}$, $θ'_{24}$ are unchanged above the GUT scale. In this paper, we study neutrino mixing in four flavor above the GUT scale.
We study the prospects for testing classes of atmospheric mixing sum rules at precision neutrino facilities. Such sum rules, which correlate the atmospheric mixing angle theta23 with the recently measured reactor angle theta13 and the cosine of the oscillation phase delta, are predicted by a variety of semi-direct models based on discrete family symmetry, classified in terms of finite von Dyck groups. We perform a detailed simulation of the performance of the next generation of oscillation experiments, including the wide band superbeam and low-energy neutrino factory proposals, and compare the…
One of the unknown parameters in neutrino oscillations is the octant of the mixing angle theta_{23}. In this paper, we discuss the possibility of determining the octant of theta_{23} in the long baseline experiments T2K and NOvA in conjunction with future atmospheric neutrino detectors, in light of non-zero value of theta_{13} measured by reactor experiments. We consider two detector technologies for atmospheric neutrinos - magnetized iron calorimeter and non-magnetized Liquid Argon Time Projection Chamber. We present the octant sensitivity for T2K/NOvA and atmospheric neutrino experiments sep…
We study the second and third generation masses in the context of the minimal renormalizable SO(10) theory. We show that if the see-saw takes the non-canonical (type II) form, large atmospheric neutrino mixing angle requires b-tau unification.
Using data from atmospheric neutrino mixing, and a simple functional form for mixing angles, the absolute values of three neutrino masses are calculated: $m_3\cong 5.37\times 10^{-2} eV$, $m_2\cong 1.94\times 10^{-2} eV$, $m_1\cong 1.46\times 10^{-2} eV$. The quantities relevant for solar neutrino mixing are calculated: $(m_2^2-m_1^2) \cong 1.63\times 10^{-4} eV^2$, with non-maximal mixing $\tan^2θ_\sol \cong 0.56$. The analysis gives a suggestion of a dynamical origin for the empirical, large CP-violating phase associated with an intrinsically, very small mixing angle in the quark sector.
Assuming atmospheric neutrino oscillations with dominant nu_mu<--->nu_tau transitions, we discuss how subdominant nu_e mixing (within the Chooz reactor bounds) can alter the zenith distributions of neutrino-induced electrons and muons. We isolate two peculiar distortion effects, one mainly related to nu_e mixing in vacuum and the other to matter oscillations, that may be sufficiently large to be detected by the SuperKamiokande atmospheric nu experiment. These effects (absent for pure two-flavor nu_mu<--->nu_tau transitions) do not vanish in the limit of energy-averaged oscillations.
We discuss two types of neutrino mass matrices which both give $θ_{23} = 45^\circ$, i.e., a maximal atmospheric mixing angle. We review three models, based on the seesaw mechanism and on simple extensions of the scalar sector of the Standard Model, where those mass matrices are obtained from symmetries.
In the flavor basis there are seven cases of two vanishing minors in the neutrino mass matrix which can accommodate the present neutrino oscillation data including the recent T2K data. It is found that two of these cases, namely $B_5$ and $B_6$ predict near maximal atmospheric neutrino mixing in the limit of large effective neutrino mass. This feature remains irrespective of the values of solar and reactor mixing angles. A non-zero reactor mixing angle is naturally accommodated in these textures.
Observations of atmospheric neutrinos are usually analyzed using the simplifying approximation that either \(ν_μ\leftrightarrow ν_τ\) or \(ν_e \leftrightarrow ν_μ\) two-flavor mixing is relevant. Here we instead consider the data using the simplifying approximation that only one neutrino mass scale is relevant. This approximation is the minimal three-flavor notation that includes the two relevant two-flavor approximations. The constraints in the parameter space orthogonal to the usual, two-flavor analyses are studied.
The India-based Neutrino Observatory (INO) will host a 50 kt magnetized iron calorimeter (ICAL@INO) for the study of atmospheric neutrinos. Using the detector resolutions and efficiencies obtained by the INO collaboration from a full-detector GEANT4-based simulation, we determine the reach of this experiment for the measurement of the atmospheric neutrino mixing parameters ($\sin^2 θ_{23}$ and $|Δm_{32}^2 |$). We also explore the sensitivity of this experiment to the deviation of $θ_{23}$ from maximal mixing, and its octant.
The PMNS neutrino mixing matrix is given, in general, by the product of two unitary matrices associated with the diagonalization of the charged lepton and neutrino mass matrices, respectively. Assuming that the active flavor neutrinos possess a Majorana mass matrix which is diagonalized by a bimaximal mixing matrix, we give the allowed forms of the charged lepton mixing matrix and the corresponding implied forms of the charged lepton mass matrix. We further assume that the origin of bimaximal mixing is a weakly broken flavor symmetry of the neutrino Majorana mass matrix, corresponding to the c…
The effect of matter enhanced neutrino oscillations on atmosheric neutrinos is investigated systematically in the framework of one mass dominant model of three neutrinos. The resonance conditions of neutrino crossing the earth are determined by the three parameters, namely, the zenith angle, ${Δm^2/E}$, and the mixing angle ${θ_3}$ of the electron neutrinos with tau neutrinos. The values of the triplet under the resonance is found numerically.
Extrapolating the tau and b masses in the MSSM tends to give for their ratio at the GUT scale a number around 1.2, for most viable values \tan β, rather than the minimal SU(5) prediction of 1. We suggest that this may be due to large off-diagonal elements in the charged lepton mass matrix M_L that can also explain the large atmospheric neutrino mixing angle. Several simple models with definite predictions for m_{tau}/m_b(M_{GUT}) are presented.
This talk, given at CPT'13, showed Super-Kamiokande atmospheric-neutrino Monte Carlo sensitivity to Lorentz-violation effects using the perturbative model derived from the Standard-Model Extension.
Solutions to the atmospheric neutrino anomaly which smoothly interpolate between nu_mu -> nu_tau and nu_mu -> nu_s oscillations are studied. It is shown that, although the Super-Kamiokande data disfavor the pure nu_mu -> nu_s channel, one cannot exclude sizable amplitude for the nu_mu -> nu_s channel in addition to nu_mu -> nu_tau oscillations.
We discuss a neutrino mass matrix $\mathcal{M}_ν$ originally found by Babu, Ma, and Valle (BMV) and show that this mass matrix can be characterized by a simple algebraic relation. From this relation it follows that atmospheric neutrino mixing is exactly maximal while at the same time an arbitrary mixing angle $θ_{13}$ of the lepton mixing matrix $U$ is allowed and--in the usual phase convention--CP violation in mixing is maximal; moreover, neither the neutrino mass spectrum nor the solar mixing angle are restricted. We put forward a simple seesaw extension of the Standard Model where the famil…
We point out an elegant mechanism to predict a maximal atmospheric angle, which is based on a maximal CP violating phase difference between second and third lepton families in the flavour symmetry basis. In this framework, a discussion of the predictions for theta_{12}, |U_{e3}|, delta and their possible correlations is provided. We also present an explicit realisation in terms of an SO(3) flavour symmetry model.
Superkamiokande atmospheric neutrino data for 990 days are analyzed in the framework of four neutrinos without imposing constraints of Big Bang Nucleosynthesis. It is shown that the wide range of the oscillation parameters is allowed at 90% confidence level ($0.1\lsim |U_{s1}|^2+|U_{s2}|^2\le 1$).
We determine the neutrino mixing and mass parameters that are allowed by the Super-Kamiokande atmospheric neutrino data in a three-neutrino model with one mass-squared difference contributing to the oscillations. We find that although $ν_μ\toν_τ$ oscillations are favored, $ν_μ\to ν_e$ oscillations with amplitude as large as 0.18 are allowed even after accounting for the limit from the CHOOZ reactor experiment. The range of allowed parameters permit observable $ν_μ\leftrightarrowν_e$ and $ν_e\toν_τ$ oscillations in future long-baseline experiments.
The sensitivity of a huge underground water/ice Cherenkov detector, such as PINGU in IceCube, to the neutrino mass hierarchy, the atmospheric mixing angle and its octant, is studied in detail. Based on the event rate decomposition in the propagation basis, we illustrate the smearing effects from the neutrino scattering, the visible energy and zenith angle reconstruction procedures, the energy and angular resolutions, and the muon mis-identification rate, as well as the impacts of systematic errors in the detector resolutions, the muon mis-identification rate, and the overall normalization. The…
We discuss the problem of the small ratio of muon mass to tau mass in a class of seesaw models where maximal atmospheric neutrino mixing is enforced through a $μ$--$τ$ interchange symmetry. We introduce into those models an additional symmetry $T$ such that $m_μ= 0$ in the case of exact $T$ invariance. The symmetry $T$ may be softly broken in the Higgs potential, and one thus achieves $m_μ\ll m_τ$ in a technically natural way. We speculate on a wider applicability of this mechanism.
We argue that regardless of the outcome of future Long Baseline experiments, additional information will be needed to unambiguously decide among the different scenarios of neutrino mixing. We use, for this purpose, a simple test of underground data: an asymmetry between downward and upward going events. Such an asymmetry, in which matter effects can be crucial, tests electron and muon neutrino data separately and can be compared with the theoretical prediction without relying on any simulation program.
The implications of a large value of the effective Majorana neutrino mass for a class of two texture zero neutrino mass matrices have been studied in the flavor basis. It is found that these textures predict near maximal atmospheric neutrino mixing angle in the limit of large effective Majorana neutrino mass. It is noted that this prediction is independent of the values of solar and reactor neutrino mixing angles. We present the symmetry realization of these textures using the discrete cyclic group $Z_3$. It is found that the texture zeros realised in this work remain stable under renormalizat…
Pioneering atmospheric muon neutrino experiments have demonstrated the near-maximal magnitude of the flavor mixing angle $θ_{23}$. But the precise value of the deviation $D \equiv 1/2 - \sin^2 θ_{23}$ from maximality (if nonzero) needs to be known, being of great interest -- especially to builders of neutrino mass and mixing models. We quantitatively investigate in a three generation framework the feasibility of determining $D$ in a statistically significant manner from studies of the atmospheric $ν_μ,\barν_μ$ survival probability including both vacuum oscillations and matter effects. We show …
We discuss two extensions of the Standard Model based on the seesaw mechanism and on non-abelian family symmetry groups O(2) and $D_4$, respectively. Both models have a twofold-degenerate neutrino Dirac mass matrix $M_D$, a Majorana mass matrix invariant under a $μ$--$τ$ interchange symmetry and the predictions of maximal atmospheric neutrino mixing and vanishing mixing angle $θ_{13}$. Leptogenesis can naturally be incorporated if $10^{-3} \lesssim m_1 \lesssim 10^{-2}$ eV where $m_1$ the mass of the lightest neutrino and if the relevant heavy neutrinos are in the range $10^{11}$ to $10^{12}$ …
The recent data describing the evidence for neutrino oscillations by Super Kamiokande implies that two neutrinos are very strongly mixed. We ask the question: can approximate maximal neutrino mixing be natural in unified (GUT or string) models? We attempt to answer this question in as much generality as possible. Without specifying a particular model, we are able to show that a gauged family symmetry can naturally provide the required maximal mixing between mu and tau neutrinos. The second and third family neutrino mass eigenstates are almost degenerate with masses of order 0.2 eV.
We analyze the atmospheric neutrino data in the context of three flavor neutrino oscillations taking account of the matter effects in the earth. With the hierarchy among the vacuum mass eigenvalues $μ_3^2 \gg μ_2^2 \geq μ_1^2$, the solution of the atmospheric neutrino problem depends on $δ_{31}=μ_3^2 - μ_1^2$ and the $13$ and $23$ mixing angles $ϕ$ and $ψ$. Whereas the sub-GeV atmospheric neutrino data imposes only a lower limit on $δ_{31} > 10^{-3} eV^2$, the zenith angle dependent suppression observed in the multi-GeV data limits $δ_{31}$ from above also. The allowed regions of the parameter…
Neutrino oscillation experiments suggest existence of new flavor-violating interactions in high energy scale. It may be possible to probe them by the flavor- and CP-violating processes in leptons and hadrons in the supersymmetric (SUSY) models. In this article the third-generation flavor violation is reviewed in the SUSY seesaw model and SUSY SU(5) GUT with the right-handed neutrinos.
We performed a simulation on the DUNE experiment to probe the capability of future neutrino long-baseline experiments' ability to constrain the parameter space of high-energy models by using the correlation between the atmospheric and reactor mixing angles. As an example, we took the Tetrahedral Flavour Symmetry model, which predicts a strong relation between the non-zero value of $θ_{13}$ and deviation of $θ_{23}$ from the maximality. We show that in this case, the model can realistically be excluded in more than $3σ$ for most of the parameter space. We also study the octant degeneracy at DUN…
It is well-known that, in the basis where the charged-lepton mass matrix is diagonal, there are seven cases of two texture zeros in Majorana neutrino mass matrices that are compatible with all experimental data. We show that two of these cases, namely B3 and B4 in the classification of Frampton, Glashow and Marfatia, are special in the sense that they automatically lead to near-maximal atmospheric neutrino mixing in the limit of a quasi-degenerate neutrino mass spectrum. This property holds true irrespective of the values of the solar and reactor mixing angles because, for these two cases, in …
I review the status of neutrino masses and mixings in the light of the solar and atmospheric neutrino data in the framework of two--, three-- and four neutrino mixing.
In this paper, we derive in a novel approach the possible textures of neutrino mass matrix that can lead us to maximal atmospheric mixing angle and Dirac CP phase which are consistent with the current neutrino oscillation data. A total of eleven textures are thus found. Interestingly, the specific texture given by the $μ$-$τ$ reflection symmetry can be reproduced from one of the obtained textures. For these textures, some neutrino mass sum rules which relate the neutrino masses and Majorana CP phases will emerge.
Charge-Parity-Time (CPT) symmetry governs that the oscillation parameters for neutrinos and anti-neutrinos are to be identical. Different mass and mixing parameters for these particles may give us a possible hint for CPT violation in the neutrino sector. Using this approach, we discuss the ability of long-baseline and atmospheric neutrino experiments to determine the difference between mass squared splittings ($Δm^{2}_{32}-Δ\bar{m}^{2}_{32}$) and atmospheric mixing angles ($\sin^{2}θ_{23}-\sin^{2}\barθ_{23}$) of neutrinos and anti-neutrinos. We show the joint sensitivity of the T2K, NOvA and I…
Exotic explanations are considered for atmospheric neutrino observations. Our analysis includes matter effects and the mixing of all three neutrinos under the simplifying assumption of only one relevant mixing scale. Constraints from accelerator, reactor and solar neutrinos are included. We find that the proposed mixing mechanisms based on violations of Lorentz invariance or on violations of the equivalence principle cannot explain the recent observations of atmospheric neutrino mixing. However the data still allow a wide range of energy dependences for the vacuum mixing scale, and also allow …
We show that if the solar and atmospheric data are both described by maximal vacuum oscillations at the relevant mass scales then there exists a unique mixing matrix for three neutrino flavors. The solution necessarily conserves CP and automatically implies that there is no disappearance of atmospheric $ν_e$, consistent with indications from the Super-Kamiokande experiment. We also investigate the consequences for three-neutrino mixing if the solar and atmospheric oscillations exhibit mixing that is large but not maximal. For non-maximal mixing $ν_e\leftrightarrowν_τ$ and $ν_e\leftrightarrowν_…
The measurement of the deviation of the 2-3 leptonic mixing from maximal, D_23 = 1/2 - sin^2(theta_23), is one of the key issues for understanding the origin of the neutrino masses and mixing. In the three-neutrino context we study the dependence of various observables in the atmospheric neutrinos on D_23. We perform a global three-neutrino analysis of the atmospheric and reactor neutrino data taking into account the effects of both the oscillations driven by the "solar" parameters (Delta_m_21^2 and theta_12) and the 1-3 mixing. The departure from the one-dominant mass scale approximation resu…
We propose a discrete non-abelian symmetry group which enforces maximal atmospheric neutrino mixing, while $θ_{13} = 0$ and the solar mixing angle $θ_{12}$ remains undetermined; without finetuning, $θ_{12}$ will be large but non-maximal. Our extension of the Standard Model has three right-handed neutrino singlets $ν_R$ and implements the seesaw mechanism. Furthermore, we have an enlarged scalar sector with three Higgs doublets and two scalar gauge singlets; the latter have masses and vacuum expectation values of the order of the seesaw scale. Lepton mixing stems exclusively from the $ν_R$ Majo…
We consider a pattern of neutrino masses in which there is an approximate mass degeneracy between the two mass eigenstates most coupled to the $ν_μ$ and $ν_τ$ flavour eigenstates. Earth-matter effects can lift this degeneracy and induce an effectively maximal mixing between these two generations. This occurs if $ν_e$'s contain comparable admixtures of the degenerate eigenstates, even rather small ones. This provides an explanation of the atmospheric neutrino anomaly in which the {\it ab initio} introduction of a large mixing angle is not required. To test this possibility we perform a novel an…
We point out that the correlation between the large atmospheric neutrino mixing and the $b \to s$ transition, if exists, comes from the lopsided flavor structure in SO(10) grand unification theory. We suggest testing the correlation by studying the deviation of $S_{ϕK_S}$ and $S_{η' K_S}$ from the standard model predictions along with the constraints from $ΔM_{B_S}$ and $b\to s γ$ in a realistic SO(10) model with lopsided flavor structure. We find a specific correlation between $S_{ϕK_S}$ and $S_{η' K_S}$ that is intrinsic to the lopsided structure and discuss how to confirm or rule out this f…
We have considered the results of solar and atmospheric neutrino oscillation experiments in the scheme of mixing of three neutrinos with a mass hierarchy. It is shown that the recent results of the CHOOZ experiment imply that |U_{e3}|^2<<1 (U is the neutrino mixing matrix), that the oscillations of solar neutrinos are described by the two-generation formalism and that the oscillations of solar and atmospheric neutrinos decouple. It is also shown that if not only |U_{e3}|^2<<1 but also |U_{e3}|<<1, then the oscillations of atmospheric neutrinos do not depend on matter effects and are described …
One of the main neutrino oscillation parameters whose value has not been determined very precisely is the leptonic $δ_{CP}$ phase. Since neutrinos have a tiny but finite mass they can undergo decay both visibly and invisibly. The effect of invisible decay of the third mass eigen state $ν_3$ on the sensitivity to $δ_{CP}$ is analysed here using atmospheric neutrino and anti-neutrino events. Effects of detector resolutions and systematic uncertainties are studied to identify the optimum resolutions and efficiencies required by a detector to obtain a significant sensitivity even in presence of de…
From recent groundbreaking experiments, it is now known that the Pontecorvo-Maki-Nakagawa-Sakata mixing differs significantly from the tribimaximal model in which theta_13=0 and theta_23=pi/4. Flavor symmetry can require that the departures from these two equations are linearly related. T' and A_4, which successfully accommodated the pre-T2K Pontecorvo-Maki-Nakagawa-Sakata matrix, predict that 38.07 deg.< theta_23 <39.52 deg. at 95% C.L.. The best fit values, combining the model predictions with T2K, MINOS, Double Chooz, Daya Bay, and RENO data, are theta_23=38.7 deg. and theta_13=8.9 deg..
Recently T2K gives hint in favor of large reactor angle. Most of the models, with tri-bimaximal mixing at the leading order, can not reproduce such a large mixing angle since they predict typically corrections for the reactor angle of the order of the Cabibbo angle. In this letter, we discuss the possibility to have large reactor angle within the T2K region with maximal atmospheric mixing angle and trimaximal solar mixing angle, through the deviation from tri-bimaximal. We derive the structure of neutrino mass matrix that leads to the large reactor angle leaving maximal atmospheric angle and t…
The simplest unified extension of the MSSM with bi-linear R--Parity violation naturally predicts a hierarchical neutrino mass spectrum, in which one neutrino acquires mass by mixing with neutralinos, while the other two get mass radiatively. We have performed a full one-loop calculation of the neutralino-neutrino mass matrix in the bi-linear \rp MSSM, taking special care to achieve a manifestly gauge invariant calculation. Moreover we have performed the renormalization of the heaviest neutrino, needed in order to get meaningful results. The atmospheric mass scale and maximal mixing angle arise…
The simplest unified extension of the Minimal Supersymmetric Standard Model with bi-linear R--Parity violation provides a predictive scheme for neutrino masses which can account for the observed atmospheric and solar neutrino anomalies in terms of bi-maximal neutrino mixing. The maximality of the atmospheric mixing angle arises dynamically, by minimizing the scalar potential, while the solar neutrino problem can be accounted for either by large or by small mixing oscillations. One neutrino picks up mass by mixing with neutralinos, while the degeneracy and masslessness of the other two is lifte…
In this paper, we derive in a novel approach the possible textures of neutrino mass matrix that can lead to maximal atmospherical mixing angle ($θ^{}_{23} = π/4$) and Dirac CP phase ($δ= - π/2$) in two phenomenologically appealing scenarios: (1) one neutrino mass matrix element being vanishing (2) one neutrino mass being vanishing. For the obtained textures, some neutrino mass sum rules which relate the neutrino masses and mixing parameters will emerge. With the help of these sum rules, the unknown absolute neutrino mass scale and Majorana CP phases can be determined. Some discussions about th…
Single right-handed neutrino dominance (SRHND) in the 23 sector of the light effective neutrino mass matrix has been proposed as a natural explanation for the concurrent large 23 mixing angle and large 23 mass hierarchy. In this paper we show how large 12 mixing angles, suitable for the large mixing angle (LMA) MSW solution to the solar neutrino problem, may arise from SRHND. In order to understand the conditions for SRHND and LMA MSW we first consider the case of one and two right-handed neutrinos, and obtain simple analytic conditions which are then extended to the case of three right-handed…
Neutrino mixing and basics of neutrino oscillations are considered. Recent evidences in favour of neutrino oscillations, obtained in the solar and atmospheric neutrino experiments, are discussed. Neutrino oscillations in the solar and atmospheric ranges of $Δm^{2}$ are considered in the framework of the minimal scheme with the mixing of three massive neutrinos.
The large observed mixing angle in atmospheric neutrinos, coupled with Grand Unification, motivates the search for a large mixing between right-handed strange and bottom squarks. Such mixing does not appear in the standard CKM phenomenology, but may induce significant b to s transitions through gluino diagrams. Working in the mass eigenbasis, we show quantitatively that an order one effect on CP violation in B_d to phi+K_S is possible due to a large mixing between right-handed b and s squarks, while still satisfying constraints from b to s + gamma. We also include the effect of right- and left…
We show that maximal atmospheric and large solar neutrino mixing can be implemented in SU(5) gauge theories, by making use of the $U(1)_F$ symmetry associated with a suitably defined family number $F$, together with a $\mathbbm{Z}_2$ symmetry which does not commute with $F$. $U(1)_F$ is softly broken by the mass terms of the right-handed neutrino singlets, which are responsible for the seesaw mechanism; in addition, $U(1)_F$ is also spontaneously broken at the electroweak scale. In our scenario, lepton mixing stems exclusively from the right-handed-neutrino Majorana mass matrix, whereas the CK…
We study the sensitivity of the Iron Calorimeter (ICAL) at the India-Based Neutrino Observatory (INO) to Lorentz and CPT violation in the neutrino sector. Its ability to identify the charge of muons in addition to their direction and energy makes ICAL a useful tool in putting constraints on these fundamental symmetries. Using resolution, efficiencies, errors and uncertainties obtained from ICAL detector simulations, we determine sensitivities to $δ{b}_{31}$, which parametizes the violations in the muon neutrino sector. We carry out calculations for three generic cases representing mixing in th…
We study the sensitivity of atmospheric neutrino experiments to the neutrino non-standard interactions (NSI) which is motivated by the tension between the two mass squared differences extracted from the KamLAND and solar neutrino experiments. In this study the sensitivity of the future Hyper-Kamiokande experiments for 4438 days to NSI is shown. Assuming that the mass hierarchy is known, we find that the best-fit value from the solar neutrino and KamLAND data can be tested at more than 8 $σ$, while the one from the global analysis can be examined at 5.0 $σ$ (1.4 $σ$) for the normal (inverted) m…
I attempt to quantify how far from maximal one should expect the atmospheric mixing angle to be given a neutrino mass-matrix that leads, at zeroth order, to a nu_3 mass-eigenstate that is 0% nu_e, 50% nu_mu, and 50% nu_tau. This is done by assuming that the solar mass-squared difference is induced by an "anarchical" first order perturbation, an approach than can naturally lead to experimentally allowed values for all oscillation parameters. In particular, both |cos 2theta_atm| (the measure for the deviation of atmospheric mixing from maximal) and |U_e3| are of order sqrt(Delta m^2_sol/Delta m^…
In this Letter we show that the evidence for neutrino oscillations from the Super-Kamiokande atmospheric neutrino data fully determines the 3x3 neutrino-oscillations mixing matrix and predicts an energy independent solar neutrino deficit at the level of 45%. This corresponds to a ratio of measured to predicted neutrino flux of R_e^{Solar} = 0.55, in good agreement with the experimental results. We achieve this result within the framework of a minimal, three-generations neutrino mixing, with mass squared differences of dM^2 = 0.45 eV^2 and dm^2 = O(10^-3) eV^2. The mixing matrix derived here is…
