369 research outputs found
A Theory of Pattern Recognition for the Discrimination between Muon and Electron in the Super-Kamiokande
The standard Super-Kamiokande analysis uses an estimator for particle
identification by which it discriminates electrons (electron nutrinos) from
muons (muon nutrinos). Use of this estimator has led to the claim of a
significant deficiency of muons (muon nutrinos), suggesting the existence of
neutrino oscillations. We investigate three areas of concern for the
Super-Kamiokande estimator: the separation of the spatial part from the angular
part in the probability functions, the neglect of fluctuations in the Cherenkov
light in different physical processes due to the charged particles concerned,
and the point-like approximation for the emission of Cherenkov light. We show
that the first two factors are important for the consideration of stochastic
processes in the generation of the Cherenkov light, and that the point-like
assumption oversimplifies the estimation of the Cherenkov light quantities. We
develop a new discrimination procedure for separating electron neutrinos from
muon neutrinos, based on detailed simulations carried out with GEANT~3.21 and
with newly derived mean angular distribution functions for the charged
particles concerned (muons and electrons/positrons), as well as the
corresponding functions for the relative fluctuations. These angular
distribution functions are constructed introducing a ``moving point''
approximation. The application of our procedure between the discrimination
between electron and muon to the analysis of the experimental data in SK will
be made in a subsequent paper.Comment: 16 pages,26 figures, late
A Discrimination Procedure between Muon and Electron in Superkamiokande Experiment Based on the Angular Distribution Function Method
In the previous paper, we construct the angular distribution functions for
muon and electron as well as their relative fluctuation functions to find
suitable discrimination procedure between muon and electron in Superkamiokande
experiment. In the present paper, we are able to discriminate muons from
electrons in Fully Contained Events with a probability of error of less than
several %. At the same time, our geometrical reconstruction procedure,
considering only the ring-like structure of the Cherenkov image, gives an
unsatisfactory resolution for 1GeV electron and muon, with a mean vertex
position error, delta r, of 5-10 m and a mean directional error, delta theta,
of about 6-20 degrees. In contrast, a geometrical reconstruction procedure
utilizing the full image and using a detailed approximation of the event
angular distribution works much better: for a 1 GeV electron, delta r is about
2 m and delta theta is about 3 degrees; for a 1GeV muon, delta r is about 3 m
and delta theta is about 5 degrees. At 5 GeV, the corresponding values are
about 1.4 m and about 2 degree for electron and are about 2.9m and about 4.3
degrees for muon. The numerical values depend on a single PMT contribution
threshold. The values quoted above are the minima with respect to this
threshold.
Even the methodologically correct approach we have adopted, based on detailed
simulations using closer approximations than those adopted in the SK analysis,
cannot reproduce the accuracies for particle discrimination, momentum
resolution, interaction vertex location, and angular resolution obtained by the
SK simulations, suggesting the assumptions in these may be inadequate.Comment: comments: 141pages, 23 figures,late
Have Superkamiokande Really Measured the Direction of the Atmospheric Neutrinos which Produce Fully Contained Events and Partially Contained Events ?
Quasi Elastic Scattering (QEL) is the dominant source for producing both
Fully Contained Events and Partially Contained Events in the
Superkamiokande(SK) detector for the atmospheric neutrinos, in the range 0.1
GeV to 10 GeV. In the analysis of SK events, it is assumed that the direction
of the incident neutrino is the same as that of the detected charged lepton. In
the present letter, we derive the distribution function for the scattering
angle of the charged leptons, their averaged scattering angle and their
standard deviation due to QEL. Then, it is shown that the SK assumption for the
scattering angle of the charged leptons in the QEL is not valid. Further, we
examine the influence of the azimuthal angle of the charged leptons over their
zenith angle. As the result, we conclude that the zenith angle distribution of
the neutrino under the SK assumption does not reflect the real zenith angle
distribution of the atmospheric neutrino which produces Fully Contained Events
and Partially Contained Events. This result has clear implication for attempts
to detect neutrino oscillations from the analyses of Fully Contained Events and
Partially Contained Events in Superkamiokande.Comment: Latex, 5 pages, 11 figures, 1 table. Submitted to Physical Review D,
Rapid Communicatio
The numerical computer experiment for the neutrino events with the SK neutrino oscillation parameters occurring outside the Superkamiokande detector
Adopting neutrino oscillation parameters obtained by Super-Kamiokande, a
numerical computer experiment for neutrino events occurring outside the
detector, is carried out in the same SK live days, 1645.9 live days,
constructing the virtual Super-Kamiokande detector in the computer. The
numerical results by the computer experiment could be directly compared with
the real SK experimental data. The comparison shows that it is difficult to
obtain convincing conclusion on the existence of the neutrino oscillation with
specified neutrino oscillation parameters claimed by SK through analysis for
neutrino events occurring outside the detector.Comment: 21 pages, 31 figure
On the Sensitivity of L/E Analysis of Super-Kamiokande Atmospheric Neutrino Data to Neutrino Oscillation Part~2 --- Four Possible L/E Analyses for the Maximum Oscillation by the Numerical Computer Experiment ---
In the previous paper (Part~1), we have verified that the SK assumption on
the direction does not hold in the analysis of neutrino events occurred inside
the SK detector. We have made four possible L/E analyses, L_nu/E_nu, L_nu/E_mu,
L_mu/E_nu and L_mu/E_mu. Among four kinds of L/E analyses, we have shown that
only L_nu/E_nu analysis can give the signature of maximum oscillations clearly,
while the L_mu/E_mu analysis which are really done by Super-Kamiokande
Collaboration cannot give the maximum oscillation at all. It is thus concluded
that Super-Kamiokande type experiment cannot find the maximum oscillation from
L/E analysis. Therefore, we would suggest Super-Kamiokande Collaboration to
re-analyze the zenith angle distribution of the neutrino events which occur
inside the detector carefully.Comment: 13 pages with 41 figures, Late
Examination on SK atmospheric neutrino experiment by the computer experiment
We examine neutrino events occurring inside the SuperKamiokande (SK) detector
and those occurring outside the same detector using computer simulations. We
analyze the zenith angle distribution of Fully Contained Events and show the
method for the determination of the incident neutrino by the SK group is
unreliable. The analysis of the neutrino events occurring outside the detector
shows these events agree with the Monte Carlo simulation without oscillation.Comment: 3 pages, 5 figures, conference of TAUP200
On the Sensitivity of L/E Analysis of Super-Kamiokande Atmospheric Neutrino Data to Neutrino Oscillation Part~1
It is said that the finding of the maximum oscillation in neutrino
oscillation by Super-Kamiokande is one of the major achievements of the SK. In
present paper, we examine the assumption made by Super-Kamiokande Collaboration
that the direction of the incident neutrino is approximately the same as that
of the produced lepton, which is the cornerstone in their L/E analysis and we
find this approximation does not hold even approximately. In the Part 2 of the
subsequent paper, we apply the results from Figures 12, 13 and 14 to L/E
analysis and conclude that one cannot obtain the maximum oscillation in L/E
analysis which shows strongly the oscillation pattern from the neutrino
oscillation.Comment: 12 pages with figures and tables, Late
Comprehensive Analysis of Neutrinos in SK part 3 -- L/E Analysis for Single Ring Muon Events II --
Following the L_nu/E_nu analysis in the preceding paper of the Fully
Contained Muon Events resulting from the quasi-elastic scattering obtained from
our numerical computer experiment. In the present paper, we carry out the
analyses of L_nu/E_mu, L_mu/E_nu and L_mu/E_mu among four possible combinations
of L and E. As the result of it, we show that we can not find the
characteristis of maximum oscillation for neutrino oscillation among two of
three, L_mu/E_mu and L_mu/E_nu. Only the L_nu/E_mu distribution can show
something like maximum oscillation, however it cannot be detected owing to the
neutral character of L_nu. It is concluded that the Super-Kamiokande Experiment
could not have found the existence of the maximum oscillation for neutrino
oscillation.Comment: 12 pages with 17 figures, Late
On the Relation between the True Directions of Neutrinos and the Reconstructed Directions of Neutrinos in L/E Analysis Performed by Super-Kamiokande Collaboration Part2
In the previous paper (Part1), we have verified that the SK assumption on the
direction does not hold in the analysis of neutrino events occurred inside the
SK detector, which is the cornerstone for their analysis of zenith angle
distributions of neutrino events. Based on the correlation between L_nu and
L_mu (Figures~16 to 18 in Part1) and the correlation between E_nu and E_mu
(Figure19 in Part1), we have made four possible L/E analyses, namely L_nu/E_nu,
L_nu/E_mu, L_mu/E_mu and L_mu/E_nu. Among four kinds of L/E analyses, we have
shown that only L_nu/E_nu analysis can give the signature of maximum
oscillations clearly, not only the first maximum oscillation but also the
second and third maximum oscillation and etc., as they should be, while the
L_mu/E_mu analysis which are really done by Super-Kamiokande Collaboration
cannot give any maximum oscillation at all. It is thus concluded from those
results that the experiments with the use of the cosmic-ray beam for neutrino
oscillation, such as Super-Kamiokande type experiment, are unable to lead the
maximum oscillation from their L/E analysis, because the incident neutrino
cannot be observed due to its neutrality. Therefore, we would suggest
Super-Kamiokande Collaboration to re-analyze the zenith angle distribution of
the neutrino events which occur inside the detector carefully, since L_nu and
L_mu are alternative expressions of the cosine of the zenith angle for the
incident neutrino and that for the emitted muon, respectively.Comment: 17 pages with 47 figures, Latex. arXiv admin note: substantial text
overlap with arXiv:1007.492
A Critical Examination on L/E Analysis in the Underground Detectors with a Computer Numerical Experiment Part 1
In the present paper we consider neutrino events due to quasi-elastic
scattering (QEL) as the most reliable events among various candidate events to
be analyzed, and have carried out the first step of an L/E analysis which aims
to confirm the survival probability with a Numerical Computer Experiment. The
most important factor in the survival probability is Lnu and Enu, but this
cannot be measured for such neutral particles. Instead, Lmu and Emu is utilized
in the L/E analysis, where Lnu, Lmu, Enu and Emu denote the flight path lengths
of the incident neutrinos, those of the emitted leptons, the energies of the
incident neutrinos and those of the emitted leptons, respectively. According to
our Computer Numerical Experiment, the relation of Lnu/Enu is nearly equal to
Lmu/Emu doesn't hold. In subsequent papers, we show the results on an L/E
analysis with the Computer Numerical Experiment based on our results obtained
in the present paper.Comment: 20 pages with figures and tables, Latex. arXiv admin note:
substantial text overlap with arXiv:1108.1064, arXiv:1007.381
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