A.K. Mann

Atmospheric muon-neutrino / electron-neutrino ratio in the multiGeV energy range

Abstract Data from the Kamiokande detector were used to study the atmospheric (v μ + v μ ) (v e + v e ) ratio in the multi-GeV energy range. The observed ratio of μ-like to e-like events relative to the calculated ratio, ( μ /e) data /( μ /e) MC = 0.57 -0.07 +0.08 ± 0.07, suggests that the atmospheric (v μ + v μ ) (v e + v e ) ratio is smaller than expected for these neutrino energies. Also studied was the zenith-angle dependence of the above ratio. Results of an analysis of neutrino oscillations are presented.

Observation of a small atmospheric vμ/ve ratio in Kamiokande

Abstract Results are presented of the observation of atmospheric neutrino interactions in the Kamiokande detector in an exposure of 4.92 kt yr. The observed ratio of single ring μ-events to e-events ( μ e ) data ( μ e ) MC = 0.60 +007 −0.06 ( stat. ) ± 0.05 ( syst. ) suggests that the atmospheric v μ /v e ratio is smaller than expected. The implications of these results for neutrino oscillations are discussed.

Experimental Study of the Atmospheric Neutrino Flux

Abstract We have observed 277 fully contained events in the KAMIOKANDE detector. The number of electron-like single-prong events is in good agreement with the predictions of a Monte Carlo calculation based on atmospheric neutrino interactions in the detector. On the other hand, the number of muon-like single-prong events is 59±7% (statistical error) of the predicted number of the Monte Carlo calculation. We are unable to explain the data as the result of systematic detector effects or uncertainties in the atmospheric neutrino fluxes.

A study of the axial-vector form factor and second-class currents in antineutrino quasielastic scattering

Abstract The antineutrino quasielastic reaction ν μm p →μ + n has been studied in the Q 2 range up to 1.0 (GeV/ c ) 2 at the Brookhaven AGS. The value of the axial vector mass M A in the dipole parametrization of the from factor was determined from the shape of the Q 2 distribution to be 1.09±0.03±0.02 GeV/ c 2 . A search for second-class currents was also conducted. No significant effect was found.

Search for neutralino dark matter in Kamiokande

Abstract A search has been made for upward-going muons in the Kamiokande detector as a possible signal from neutralino dark matter captured in the earth. We found the upward-going muon flux from the earth is consistent with that produced by the atmospheric neutrinos. Assuming the galactic halo contains neutralino dark matter, this result provides limits on the neutralino mass in the region 30–80 GeV and gives stringent constraints on the allowed regions of the parameter space in the framework of the minimal supersymmetric standard model.

Experimental limits on nucleon lifetime for lepton+meson decay modes

Abstract We have searched for nucleon decay signals using data from the KAMIOKANDE-II detector. No evidence for nucleon decay has been found. Limits on the nucleon partial lifetime for various decay modes are obtained combining KAMIOKANDE-I and -II data (3.76 kt yr in total). The background subtracted limits at 90% CL range from 0.1×1032yr to 2.6×1032yr depending on the decay modes. For the decay modes p→e+π0, p→ v K+ and n→ v K0, the limits are 2.6×1032yr, 1.0×1032yr and 0.9×1032yr, respectively.

Possible methods of searching for a weak neutral current in e+ + e− → μ+ + μ−

Abstract The possibility of observing interference between a weak interaction amplitude and an electromagnetic amplitude in the reaction e + e − → μ + μ − is enhanced by the expectation that the circulating e + and e − beams in a storage ring are polarized. We discuss the salient features of a possible experiment, utilizing that polarization, which allows a search for a primitive weak neutral current to be made at high center of mass energy in that purely leptonic system.

A Neutron Detection System for Use with Pulsed Accelerators

Description is given of a neutron detection system which utilizes the time necessary for slow neutrons to diffuse in a moderating medium for turning on a counter between pulses of an accelerator. The apparatus has a detection efficiency of 0.5 percent over a wide range of neutron energies. The arrangement of apparatus, circuitry details, and performance characteristics are described.

A limit on massive neutrino dark matter from Kamiokande

Abstract We have searched for possible high-energy neutrino signals expected from massive neutrino dark matter captured by the earth and the sun, by making use of upward-going muon samples collected in the seven years of operation of the Kamiokande detector. No excess of events was found from the earth or the sun, thus giving an excluded mass range of Dirac-(Majorana-) type neutrinos, 6 (24) ⩽ m ν ⩽ several hundred GeV, as the dark matter which consitutes the halo of the galaxy. The upper bounds extend to a mass range never before analyzed in previous indirect searches.

Survey of atmospheric neutrino data and implications for neutrino mass and mixing

Abstract A detailed comparison is made of the atmospheric neutrino results obtained by the Frejus, IMB-3, and Kamiokande detectors. The implications of these results for vacuum neutrino oscillations are presented, and juxtaposed with the results for matter neutrino oscillations from the solar neutrino data.