The sensitivity of the atmospheric neutrino experiments to the non-standard flavor-dependent interaction in neutrino propagation is studied under the assumption that the only nonvanishing components of the non-standard matter effect are the electron and tau neutrino components $ε_{ee}$, $ε_{eτ}$, $ε_{ττ}$ and that the tau-tau component satisfies the constraint $ε_{ττ}=|ε_{eτ}|^2/(1+ε_{ee})$ which is suggested from the high energy behavior for atmospheric neutrino data. It is shown that the Superkamiokande (SK) data for 4438 days constrains $|\tanβ|\equiv|ε_{eτ}/(1+ε_{ee})|\lesssim 0.8$ at 2.5$σ$ (98.8\%) CL whereas the future Hyperkamiokande experiment for the same period of time as SK will constrain as $|\tanβ|\lesssim 0.3$ at 2.5$σ$CL from the energy rate analysis and the energy spectrum analysis will give even tighter bounds on $ε_{ee}$ and $|ε_{eτ}|$.
The precise knowledge of the atmospheric neutrino fluxes is a key ingredient in the interpretation of the results from any atmospheric neutrino experiment. In the standard atmospheric neutrino data analysis, these fluxes are theoretical inputs obtained from sophisticated numerical calculations based on the convolution of the primary cosmic ray spectrum with the expected yield of neutrinos per incident cosmic ray. In this work we present an alternative approach to the determination of the atmospheric neutrino fluxes based on the direct extraction from the experimental data on neutrino event rat…
Recent Super-Kamiokande data on the atmospheric neutrino anomaly are used to test various mechanisms for neutrino oscillations. It is found that the current atmospheric neutrino data alone cannot rule out any particular mechanism. Future long-baseline experiments should play an important role in identifying the underlying neutrino oscillation mechanism.
I review the history on neutrino magnetic moments and apply the neurino magnetic moment idea to constrain its bound from Super-Kamiokande neutrino oscillation data.
The main goal of the IceCube Deep Core Array is to search for neutrinos of astrophysical origins. Atmospheric neutrinos are commonly considered as a background for these searches. We show here that cascade measurements in the Ice Cube Deep Core Array can provide strong evidence for tau neutrino appearance in atmospheric neutrino oscillations. A careful study of these tau neutrinos is crucial, since they constitute an irreducible background for astrophysical neutrino detection.
We propose an effective mass matrix for light neutrinos which is consistent with the mixing pattern indicated by solar and atmospheric neutrino experiments. Two scenarios for the mass eigenvalues are discussed and the connection with double beta decay is noted.
In the TeV energy region and above, the uncertainty in the level of prompt atmospheric neutrinos would limit the search for diffuse astrophysical neutrinos. We suggest that neutrino telescopes may provide an empirical determination of the flux of prompt atmospheric electron and muon neutrinos by measuring the flux of prompt down-going muons. Our suggestion is based on the consideration that prompt neutrino and prompt muon fluxes at sea level are almost identical.
Atmospheric neutrino-fluxes are calculated over the wide energy range from 30 MeV to 3,000 GeV for the study of neutrino-physics using the data from underground neutrino-detectors. The atmospheric muon-flux at high altitude and at sea level is studied to calibrate the neutrino-fluxes at low energies and high energies respectively. The agreement of our calculation with observations is satisfactory. The uncertainty of atmospheric neutrino-fluxes is also studied.
After some generalities on neutrino oscillations and on neutrinos, the recent experimental results presented by Soudan 2, MACRO and SuperKamiokande at the Neutrino'98 conference are summarized and discussed.
In this talk we will discuss the physics reach of the atmospheric neutrino data collected by a future megaton-class neutrino detector. After a general discussion of the potentialities of atmospheric neutrinos on general basis, we will consider concrete experimental setups and show that synergic effects exist between atmospheric and long-baseline neutrino data. Finally, we will show that present Super-Kamiokande data already have the capability to allow for a direct and unbiased measurement of the energy spectrum of the atmospheric neutrino fluxes.
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.
Analyis of the Superkamiokande atmospheric neutrino data is presented in the framework of four neutrinos without imposing constraints of Big Bang Nucleosynthesis. Implications to long baseline experiments are briefly discussed.
We consider flavor changing effective neutrino interactions in the context of massive neutrinos in the issue of atmospheric neutrinos. Assuming as usual that this is an indication of the oscillation of muon neutrinos into tau neutrinos we show that there is a set of parameters which is consistent with the MSW resonance condition for the typical Earth density and atmospheric neutrino energies. In particular we show that even if the vacuum mixing angle vanishes it is still possible to have a resonance which is compatible with the atmospheric neutrino data. We also briefly consider the case of th…
The potential of future high statistics atmospheric neutrino experiments is considered, having in mind currently discussed huge detectors of various technologies (water Cerekov, magnetized iron, liquid Argon). I focus on the possibility to use atmospheric data to determine the octant of $θ_{23}$ and the neutrino mass hierarchy. The sensitivity to the $θ_{23}$-octant of atmospheric neutrinos is competitive (or even superior) to long-baseline experiments. I discuss the ideal properties of a fictitious atmospheric neutrino detector to determine the neutrino mass hierarchy.
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.
The atmospheric neutrino-flux is calculated over the wide energy range from 1 GeV to 3,000 GeV for the study of neutrino-physics using the data from underground neutrino-detectors. The uncertainty of atmospheric neutrino-flux is also discussed. A brief comment is made to interpret the anomaly in terms of neutrino oscillations.
We show that for long-baseline experiments using a Mt water Cerenkov detector atmospheric neutrino data provide a powerful method to resolve parameter degeneracies. In particular, the combination of long-baseline and atmospheric data increases significantly the sensitivity to the neutrino mass hierarchy and the octant of $θ_{23}$. Furthermore, we discuss the possibility to use $μ$-like atmospheric neutrino data from a big magnetized iron calorimeter to determine the neutrino mass hierarchy.
We show that the SuperKamiokande atmospheric neutrino results explain electric charge quantisation, provided that the oscillation mode is $ν_μ \to ν_τ$ and that the neutrino mass is of Majorana type.
The neutral current effects of the future high statistics atmospheric neutrino data can be used to distinguish the mechanisms between a $ν_μ$ oscillation to a tau neutrino or to a sterile neutrino. However, if neutrinos possess large diagonal and/or transition magnetic moments, the neutrino magnetic moments can contribute to the neutral current effects which can be studied by the single $π^0$ production events in the Super-K data. This effect should be included in the future analyses of atmospheric data in the determination of $ν_μ$ to tau or sterile neutrino oscillation.
Recent results of atmospheric neutrino experiments are reviewed and their possible interpretations are discussed, main emphasis being put on the neutrino oscillation hypothesis.
Interpretation and understanding of the evidence for neutrino oscillations depends on knowledge of the atmospheric neutrino beam. In this talk I assess how well various features are known. The goal is to determine to what extent uncertainties in the neutrino beam may limit the conclusions about neutrino properties and which features of the evidence for neutrino oscillations are most robust.
We present an overview of the current status of neutrino oscillation studies at atmospheric neutrino experiments. While the current data gives some tentalising hints regarding the neutrino mass hierarchy, octant of $θ_{23}$ and $δ_{CP}$, the hints are not statistically significant. We summarise the sensitivity to these sub-dominant three-generation effects from the next-generation proposed atmospheric neutrino experiments. We next present the prospects of new physics searches such as non-standard interactions, sterile neutrinos and CPT violation studies at these experiments.
The uncertainty in the calculation of atmospheric neutrino fluxes is studied. The absolute value of atmospheric neutrino fluxes is sensitive to variation of the primary cosmic ray flux model and/or the interaction model. However, the ratios between different kind of neutrinos stay almost unchanged with these variations. It is unlikely that the anomalous ratio $(ν_μ/ν_e)_{obs}/(ν_μ/ν_e)_{MC}$ reported by Kamiokande and Super Kamiokande is caused by the uncertainty of predicted atmospheric neutrino fluxes.
We evaluate the flux of tau neutrinos produced from the decay of pair produced taus from incident muons using a cascade equation analysis. To solve the cascade equations, our numerical result for the tau production $Z$ moment is given. Our results for the flux of tau neutrinos produced from incident muons are compared to the flux of tau neutrinos produced via oscillations and the direct prompt atmospheric tau neutrino flux. Results are given for both downward and upward going neutrinos fluxes and higher zenith angles are discussed. We conclude that the direct prompt atmospheric tau neutrino fl…
Motivated by the Exact Parity Model and other theories, the hypothesis that each of the known neutrinos oscillates maximally with a sterile partner has been put forward as an explanation of the atmospheric and solar neutrino anomalies. We provide detailed predictions for muon and electron flux ratios induced in the Kamiokande and SuperKamiokande detectors by sub-GeV atmospheric neutrinos. Several different, carefully chosen cuts on momentum and zenith angle are proposed, emphasizing the role of up-down flux asymmetries.
A combined analysis of the terrestrial neutrino experiments and the Kamiokande observation of atmospheric neutrino anomaly is performed under the assumption of the existence of dark-matter-mass neutrinos, as suggested by the recent Los Alamos experiment. In the three-flavor mixing scheme of neutrinos it is shown that the constraints from these experiments are so strong that the patterns of mass hierarchy and flavor mixing of neutrinos are determined almost uniquely depending upon the interpretation of the atmospheric neutrino anomaly.
The precise knowledge of the atmospheric neutrino fluxes is a key ingredient in the interpretation of the results from any atmospheric neutrino experiment. In the standard atmospheric neutrino data analysis, these fluxes are theoretical inputs obtained from sophisticated numerical calculations. In this contribution we present an alternative approach to the determination of the atmospheric neutrino fluxes based on the direct extraction from the experimental data on neutrino event rates. The extraction is achieved by means of a combination of artificial neural networks as interpolants and Monte …
Atmospheric neutrinos produced by cosmic-ray interactions in the atmosphere are of interest for several reasons. As a beam for studies of neutrino oscillations they cover a range of parameter space hitherto unexplored by accelerator neutrino beams. The atmospheric neutrinos also constitute an important background and calibration beam for neutrino astronomy and for the search for proton decay and other rare processes. Here we review the literature on calculations of atmospheric neutrinos over the full range of energy, but with particular attention to the aspects important for neutrino oscillati…
We demonstrate that atmospheric neutrino data accumulated with the AMANDA and the partially deployed IceCube experiments constrain the allowed parameter space for a hypothesized fourth sterile neutrino beyond the reach of a combined analysis of all other experiments. We also illustrate the sensitivity of the completed IceCube detector, that is now taking data, to the parameter space of 3+1 model.
The atmospheric neutrinos produce isolated neutral pions ($π^0$-events) mainly in the neutral current interactions. We propose to study the ratios involving $π^0$-events and the events induced mainly by the charged currents. This minimizes uncertainties related to the original neutrino fluxes, and in certain cases, also to the cross-sections. Experimental study of these ratios will allow one to check the oscillation solution of the atmospheric neutrino problem and to identify the channel of oscillations. Illustrative analysis of existing data is presented.
Measurements of atmospheric neutrinos by Super-Kamiokande an other detectors have given evidence for the existence of neutrino oscillations with large mixing and $Δm^2$ in the range 10^{-3}-10^{-2} eV^2. In this work we discuss critically some of the possible experimental strategies to confirm this result and determine more accurately the neutrino oscillation parameters. A possible method is the development of long-baseline accelerator neutrino beams. The accelerator beams can have higher intensity and higher average energy than the atmospheric flux, and if (ν_μ\leftrightarrow ν_τ) oscillation…
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 ($0.1\lsim |U_{s1}|^2+|U_{s2}|^2\le 1$).
The formalism for neutrino flavor change induced by lepton family number violating interactions is developed for the three-neutrino case, and used to derive the corresponding flavor change probabilities in matter. Applied to the solar and atmospheric neutrino fluxes, it is argued that the observed anomalies, including the zenith dependence for the atmospheric case, could be due to such interactions.
We compute up-down asymmetries for atmospheric neutrino induced electron and muon events in the SuperKamiokande detector for the following neutrino oscillation models: (A) maximally mixed $ν_μ - ν_τ$ or $ν_μ - ν_s$, (B) maximally mixed $ν_μ - ν_e$, (C) threefold maximal mixing between $ν_e, ν_μ$ and $ν_τ$, and (D) neutrino oscillations via Equivalence Principle or Lorentz invariance violation. We emphasise the role of different momentum cuts.
Neutrinoless double beta ($\znbb$) decay is considered within bilinear R-parity breaking supersymmetry, including the full one-loop corrections to the neutrino-neutralino mass matrix. Expected rates for $\znbb$ decay in this model are discussed in light of recent atmospheric and solar neutrino data. We conclude that (a) tree-level calculations for $\znbb$ decay within the bilinear model are not reliable in the range of parameters preferred by current solar and atmospheric neutrino problems. And (b) if the solar and atmospheric neutrino problems are to be solved within bilinear R-parity violati…
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.
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.
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 …
We analyzed the atmospheric neutrino experiments of SuperKamiokande including zenith angle dependence's using the three-flavor neutrino framework with the hierarchy m^2_1 \approx m^2_2<<m^2_3. Taking into account the terrestrial, solar neutrino experimental data and the atmospheric neutrino experiments including the sub-GeV and multi-GeV data in SuperKamiokande, large angle solution in the solar neutrino experiments is favored and the range of the mass parameter Deltam^2_{23} is restricted between 0.08eV^2 - 2eV^2. Allowed regions of mixing parameters are (theta_{13}<4degree, 27degree<theta_{2…
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.
The results on the fluxes of charged particles and neutrinos from a 3-dimensional (3D) simulation of atmospheric showers are presented. An agreement of calculated fluxes with data on charged particles from the AMS and CAPRICE detectors is demonstrated. Predictions on neutrino fluxes at different experimental sites are compared with results from other calculations.
We present an evaluation of the atmospheric tau neutrino flux in the energy range between $10^2$ and $10^6$ GeV. The main source of tau neutrinos is from charmed particle production and decay. The $ν_τN\to τX$ event rate for a detector with a water equivalent volume of 1 km$^3$ is on the order of 60-100 events per year for $E_τ>100$ GeV, reducing to 18 events above 1 TeV. Event rates for atmospheric muon neutrino oscillations to tau neutrinos are also evaluated.
Superkamiokande atmospheric neutrino data for 535 days are analyzed in the framework of three flavor oscillations with mass hierarchy. It is shown that the best fit point is very close to the pure maximal $ν_μ\leftrightarrowν_τ$ case and $Δm^2 \simeq 7\times10^{-3}$ eV$^2$. The allowed region at 90 %CL is given and the implications to the long baseline experiments are briefly discussed.
I describe an attempt to understand the significance of the atmospheric neutrino deficit observed by the Kamiokande neutrino detector. In particular, I am concerned with the statistical significance quoted for the zenith-angle dependence of the deficit, which has been cited as evidence for neutrino flavor oscillations free of systematic uncertainties.
Measurements of the intensity of primary cosmic-ray protons reported in the last two years suggest a lower normalization than some earlier measurements. Here we comment on the measurements, compare them to assumptions made in two independent calculations of atmospheric neutrinos and discuss the possible consequences for interpretation of measurements of atmospheric neutrinos.
The atmospheric neutrino anomaly is the apparent reduction of the $ν_μ/ν_{e}$ ratio observed in underground detectors. It represents either a reduction in the muon neutrino interaction rate or an excess of the electron neutrino interaction rate, or both. Unable to answer the question of ``What else could it be?'' this paper explores a number of alternatives which do not seem to be viable. Various methods to reduce the apparent muon rate or to increase the apparent electron rate are discussed. Perhaps our bias that the interactions are due to neutrinos of atmospheric origin is incorrect. Both o…
Earth medium effects in the three-neutrino oscillations of atmospheric neutrinos are observable under appropriate conditions. This paper generalizes the study of the medium effects and the possibility of their observation in the atmospheric neutrino oscillations from the case of neutrinos traversing only the Earth mantle, where the density is essentially constant, to the case of atmospheric neutrinos crossing also the Earth core. In the latter case new resonance-like effects become apparent. We calculate the CPT-odd asymmetry for the survival probability of muon neutrinos and the observable mu…
Quantum-mechanical calculations of transitions dynamics between the left- and right-handed helicity states of the atmospheric muon Dirac neutrino,which has a gravitoelectrical dipole moment (GEDM) interacting with the gravitational field of the Earth have been carried out. It is shown that the asymmetry of the zenith-angle distribution of an atmospheric muon neutrino can be explained by the interference of two mutually perpendicular plain-wave neutrino states having different velocites inside the Earth in the presence of its gravitation field. The deficit of the solar neutrino can also be expl…
The importance of non-zero neutrino mass as a probe of particle physics, astrophysics, and cosmology is emphasized. The present status and future prospects for the solar and atmospheric neutrinos are reviewed, and the implications for neutrino mass and mixing in 2, 3, and 4-neutrino schemes are discussed. The possibilities for significant mixing between ordinary and light sterile neutrinos are described.
Neutrino decay has been proposed as a possible solution to the atmospheric neutrino anomaly, in the light of the recent data from the Super-Kamiokande experiment. We investigate this hypothesis by means of a quantitative analysis of the zenith angle distributions of neutrino events in Super-Kamiokande, including the latest (45 kTy) data. We find that the neutrino decay hypothesis fails to reproduce the observed distributions of muons.
This paper reviews the history of the atmospheric neutrino anomaly. The historical record does not support more recent claims that the anomaly constitutes evidence for a neutrino mass. Most experiments have reported an apparent muon deficiency which is independent of energy and distance. Time dependent variations in the Super Kamioka results are noted.
The zenith angle distributions of atmospheric neutrinos are determined by the possible presence of neutrino oscillations and the combination of three most important contributions: (1) geomagnetic effects on the primary cosmic rays, that suppress the primary flux in the Earth's magnetic equatorial region, (2) the zenith angle dependence of the neutrino yields, due to the fact that inclined showers produce more neutrinos, and (3) geometrical effects due to the spherical shell geometry of the neutrino production volume. The last effect has been recognized only recently and results in an important…
Observations of atmospheric neutrinos by the SuperKamiokande collaboration have demonstrated large mixing of the muon-neutrino. However the present atmospheric neutrino data does not significantly constrain the associated mixing of the electron-neutrino, or the sign of the mass-squared difference. Here we identify the diagnostics for these quantities and they also test the theory of how matter affects neutrino oscillations. These diagnostics are a dip in the sub-GeV muon flux at a zenith angle of 110 degrees, a bump in the electron up-down asymmetry at multi-GeV energies and a bump in the muon…
We discuss recent searches for new physics using high-energy atmospheric neutrino data from IceCube, namely sterile neutrinos with masses in the range $Δm^2 = 0.01$ eV$^2$ - 10 eV$^2$, and non-standard interactions (NSI) in the $ν_μ- ν_τ$ sector. We also present a brief review of the current status of NSI theory and phenomenology.
The FLUKA calculation of the atmospheric neutrino fluxes have been cross-checked by comparing predictions on lepton fluxes in atmosphere to experimental data. The dependence of predicted neutrino fluxes on the shape and normalization of primary spectrum is also investigated
With the measurement of the small parameter $\sin^{2}θ_{13}$ experiments on the study of neutrino oscillations enter into a high precision era. I discuss here the problem of the definition of the atmospheric mass-squared difference which will be important for analysis of data of future experiments.
Bounds are derived on the cross section, flux and energy density of new particles that may be responsible for the atmospheric neutrino anomaly. $4.6 \times 10^{-45} cm^2 < σ<2.4 \times 10^{-34} cm^2$ Decay of primordial homogeneous dark matter can be excluded.
Sensitivity of the magnetised Iron CALorimeter (ICAL) detector at the proposed India-based Neutrino Observatory (INO) to invisible decay of the mass eigenstate $ν_3$ using atmospheric neutrinos is explored. A full three-generation analysis including earth matter effects is performed in a framework with both decay and oscillations. The wide energy range and baselines offered by atmospheric neutrinos are shown to be excellent for constraining the $ν_3$ lifetime. We find that with an exposure of 500 kton-yr the ICAL atmospheric experiment could constrain the $ν_3$ lifetime to $τ_3/m_3>1.51\times1…
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.
