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What the Atmospheric Neutrino Anomaly is Not  [PDF]
J. M. LoSecco
Physics , 1998,
Abstract: The atmospheric neutrino anomaly is the apparent reduction of the $\nu_{\mu}/\nu_{e}$ 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 of these assumptions need to be confirmed. Efforts to reduce uncertainties in the estimated atmospheric neutrino flux would also help to narrow the possibilities further.
Interpreting the Atmospheric Neutrino Anomaly  [PDF]
R. P. Thun,S. McKee
Physics , 1998, DOI: 10.1016/S0370-2693(98)01021-1
Abstract: We suggest that the atmospheric neutrino anomaly observed in the Super-Kamiokande (and other) experiments results from the combined effects of muon-neutrino to tau-neutrino oscillations with a Delta m^2 value of approximately 0.4 eV^2 and oscillations between muon neutrinos and electron neutrinos (and vice-versa) with 0.0001 < Delta m^2 < 0.001 eV^2. With an appropriate choice of a three-neutrino mixing matrix, such a hypothesis is consistent with essentially all neutrino observations.
The Atmospheric Neutrino Anomaly: Muon Neutrino Disappearance  [PDF]
John G. Learned
Physics , 2000,
Abstract: With the 1998 announcement of new evidence for muon neutrino disappearance observed by the Super-Kamiokande experiment, the more than a decade old atmospheric neutrino anomaly moved from a possible indication for neutrino oscillations to an almost inescapable implication. The evidence from all experiments is reviewed, and indications are presented that the oscillations are probably between muon and tau neutrinos with nearly maximal mixing. Implications and future directions in neutrino oscillations research are discussed.
Bounds on Dark Matter from the ``Atmospheric Neutrino Anomaly''  [PDF]
J. M. LoSecco
Physics , 1997, DOI: 10.1103/PhysRevD.56.4416
Abstract: Bounds are derived on the cross section, flux and energy density of new particles that may be responsible for the atmospheric neutrino anomaly. $4.6 \times 10^{-45} cm^2 < \sigma <2.4 \times 10^{-34} cm^2$ Decay of primordial homogeneous dark matter can be excluded.
On the Atmospheric Neutrino Anomaly and its Statistical Significance  [PDF]
G. L. Fogli,E. Lisi
Physics , 1995, DOI: 10.1103/PhysRevD.52.2775
Abstract: An analysis of the existing data on the atmospheric neutrino anomaly is presented, focused on the statistical significance that can be attributed to its experimental evidence. Our approach is alternative to the usual analyses in terms of the $\mu/e$ ratio of event rates. In fact, we perform a comparison between data and expectations, by {\em separating\/} the information on $e$-like and $\mu$-like events, with a careful estimate of the different errors and of their correlation effects. The results are shown both numerically and graphically, and disclose interesting aspects of the atmospheric neutrino anomaly, that the use of the $\mu/e$ ratio would partially hide, both in the sub-GeV and in the multi-GeV energy range.
Measuring the $ν_μ$ to $\bar{ν_μ}$ Ratio in a High Statistics Atmospheric Neutrino Experiment  [PDF]
J. M. LoSecco
Physics , 1998, DOI: 10.1103/PhysRevD.59.117302
Abstract: By exploiting differences in muon lifetimes it is possible to distinguish $\nu_{\mu}$ from $\bar{\nu_{\mu}}$ charged current interactions in underground neutrino detectors. Such observations would be a useful tool in understanding the source of the atmospheric neutrino anomaly.
Four-neutrino oscillation solutions of the atmospheric neutrino anomaly  [PDF]
G. L. Fogli,E. Lisi,A. Marrone
Physics , 2000, DOI: 10.1103/PhysRevD.63.053008
Abstract: In the context of neutrino scenarios characterized by four (three active plus one sterile) neutrino species and by mass spectra with two separated doublets, we analyze solutions to the atmospheric neutrino anomaly which smoothly interpolate between \nu_\mu-->\nu_\tau and \nu_\mu-->\nu_s oscillations. We show that, although the Super-Kamiokande data disfavor the pure \nu_\mu-->\nu_s channel, they do not exclude its occurrence, with sizable amplitude, in addition to the \nu_\mu-->\nu_\tau channel. High energy muon data appear to be crucial in assessing the relative amplitude of active and sterile neutrino oscillations. It is also qualitatively shown that such atmospheric \nu solutions are compatible with analogous solutions to the solar neutrino problem, which involve oscillations of \nu_e in both sterile and active states.
Atmospheric Neutrino Anomaly and Supersymmetric Inflation  [PDF]
G. Lazarides,N. D. Vlachos
Physics , 1998, DOI: 10.1016/S0370-2693(98)01126-5
Abstract: A detailed investigation of hybrid inflation and the subsequent reheating process is performed within a mu problem solving supersymmetric model based on a left-right symmetric gauge group. The process of baryogenesis via leptogenesis is especially studied. For mu and tau neutrino masses consistent with the small angle MSW resolution of the solar neutrino problem and the recent results of the SuperKamiokande experiment, we show that maximal mu-tau neutrino mixing can be achieved. The required value of the relevant coupling constant is, however, quite small (of the order 10^{-6}).
Is the $ν_μ--> ν_s$ oscillation solution to the atmospheric neutrino anomaly excluded by the superKamiokande data?  [PDF]
R. Foot
Physics , 2000, DOI: 10.1016/S0370-2693(00)01290-9
Abstract: Recently the SuperKamiokande collaboration have claimed that their data exclude the $\nu_\mu --> \nu_s$ solution to the atmospheric neutrino anomaly at more than 99% C.L. We critically examine this claim.
Neutrino-Oxygen interactions: role of nuclear physics in the atmospheric neutrino anomaly  [PDF]
J. Marteau,J. Delorme,M. Ericson
Physics , 1999,
Abstract: The apparent anomaly in the ratio of muon to electron atmospheric neutrinos first observed by Kamiokande and IMB has been confirmed by Super-Kamiokande and Soudan-2. The experimental analysis, including the asymmetry in the zenithal distributions of the $ \mu-\mathrm{type} $ events in Super-Kamiokande gives a strong support to the neutrino oscillation hypothesis to solve the anomaly. In this work we are interested by the role of nuclear physics in the neutrino-oxygen reactions used to detect the atmospheric neutrinos. We point out that multi-nucleon excitations of np-nh type and that nuclear correlations could modify an experimental analysis \`a la Super-Kamiokande because they lead to a substantial enhancement of the number of 1 \v{C}erenkov ring retained events.
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