Lawrence Sulak

Limits on the flux of energetic neutrinos from the sun

Abstract A number of authors have proposed mechanisms by which the sun could be a strong source of energetic neutrinos. We search for an excess signal of penetrating neutral particles from the direction of the sun. We employ two data samples. One sample studies energies from 400 MeV to 2 GeV. The other studies v μ interactions above 2 GeV where the atmospheric background is lower. Our results are compared with the general background of atmospheric neutrinos from other directions. No significant excess has been found. These results can be used to set limits on possible dark matter candidates.

A waveshifter light collector for a water Cherenkov detector

Abstract A device has been developed which is capable of doubling the light collection capability of a 5 inch hemispherical photomultiplier tube. Known as a “waveshifter plate”, its geometry is adaptable to various applications. Its marginal cost is small with respect to that of a phototube, it is readily removable, and it has minimum effect upon dark noise and timing resolution.

The performance of photomultipliers exposed to helium

Abstract We report results of a study to determine how the performance of photomultipliers is affected by exposure to He. In our tests we monitor two 5 in. diameter EMI hemispherical photomultipliers while they are operated in He environments. Initially we observed He + afterpulses, at an approximately constant delay relative to the primary anode pulse. As the He gas pressure in the tubes increases however, strings of pulses typical of Townsend discharges occur. For the glass composition and geometry of the photomultipliers used in our tests, the internal gas concentration as a function of exposure to He is calculated using Ficks law for the permeation of solids by gases. The He permeation constant for the photomultiplier glass is obtained from a semiempirical formula developed by Altemose. We calculate the internal He concentration resulting from the He exposure which is observed to cause the regular occurrence of discharges and find that it is consistent with that required for production of discharges in the Townsend model. Guidelines are presented for using our results to estimate lifetimes of photomultipliers of different geometries and glass types when operated in He environments.

Investigation of Matter Enhanced Neutrino Oscillations Relevant to the Solar Neutrino Problem

Abstract We study the effect of matter enhanced neutrino oscillations on atmospheric neutrinos. A recently proposed solution to the solar neutrino problem with Δm 2 = 1.1×10 −4 eV 2 suggests enhanced effects in the range 200 MeV-500MeV. We find no evidence of this effect for v μ ↔ v e mixing. Limits are set on the magnitude of the mixing angle. Our limit is sin θ v

Design of an enhanced 1 GeV electron neutrino beam

Abstract An enhanced νe beam would be useful for experiments that have been proposed to investigate the time evolution of a νe beam or to test the universality of νe and νμ interactions. We have performed detailed calculations to maximize the flux of electron neutrinos through a detector while minimizing the more copious muon neutrinos produced at 30 GeV proton accelerators. The νe beam is formed from the semi-leptonic decay modes of the neutral kaon. Muon neutrinos generated by decays of charged pions and kaons are suppressed by a dipole sweeping magnet. The νe/νμ ratio is enhanced from its usual value of ∼ 1 1000 to a value of ∼ 1 2 , albeit at a low flux. We find with this design a typical flux of 1.5 × 107νe/m2s. We find that a high magnetic field (≥ 40 kG) is essential to achieve this νe/νμ enhancement. Although the use of collimators and/or plugs inside the magnet reduces the νμ flux, the νe flux is also diminished so that there is little beneficial effect on the νe/νμ ratio. Magnetic focusing horns and quadrupole beams do not enhance the νe/νμ ratio. The accuracy of the energy dependence of the calculation, as well as the absolute normalization of the fluxes, is determined by a subsidiary calculation of the νμ yield from the magnetic horn focused beam at Brookhaven National Laboratory. This calculation is the first to our knowledge to agree well with the νμ yield as measured in the BNL seven foot bubble chamber.

LIMITS ON THE PRODUCTION OF NEUTRAL PENETRATING STATES IN A BEAM DUMP

Abstract We present limits on the production of neutral penetrating states produced in 28 GeV proton nucleus collisions. We obtain limits for light, heavy and unstable neutral states. For light stable states our limit σ I σ P −69 cm 4 /nucleon 2 is more than a factor of 5.5 better than previous limits. Time of flight techniques are used to study heavy states. We have poor sensitivity to short-lived states.

Waiting for the proton to decay: 1983 results from the new dedicated experiments

Three new dedicated experiments searching for proton decay came on the air during the last year or so. Orders of magnitude more neutrino events, as well as possible nucleon decay candidates, have been recorded. Significant new limitss have been placed on many modes of nucleon decay. Representative lower limits at 90% C.L. for the lifetime/branching ratio for p→e+π0 of 2.0×1032 years, p→e+K0 of 3.1×1031 years, p→μ+K0 of 2.6×1031 years, and n→νK0 of 0.8×1031 years have been set by the IMB group. Many other limits have also been set by the HPW, IMB, Kamioka, Kolar, and Mont Blanc experiments. Contained interactions have been observed in four detectors at rates expected from atmospheric neutrino induction, within the 30‐50% errors on the calculations. The status1 of the operational experiments is discussed, and typical restrictive results are reviewed. Detectors under construction are also mentioned.

Status of the BNL muon (g-2) experiment

The muon (g-2) experiment at Brookhaven has completed a first run. The main components of the experiment, which include the superconducting inflector, the superferric storage ring, the electrostatic quadrupoles and the lead-scintillating fiber electron calorimeters, have been commissioned satisfactorily. The analysis of data taken in June and July 1997 is in progress.

Neutrino astrophysics with IMB: past, present, and future

A burst of eight neutrino interactions occurring over a six second interval has been observed with the IMB detector. The closeness in time of the burst to the optical discovery of Supernova 1987a suggests that the neutrinos originated from stellar collapse. The characteristics of the burst are reviewed together with a recently completed reevaluation of many aspects of the detectors response. Efforts underway to discover past and future supernovae are also briefly discussed.

A Search for Proton Decay into e+π° Irvine-Michigan-Brookhaven Collaboration

Observations were made 1570 mwe underground with an 8000 metric ton water Cherenkov detector. During a live-time of 80 days no events consistent with the decay p → e+π° were found in a fiducial mass of 3300 metric tons. We conclude that the limit on the lifetime for bound plus free protons divided by the e+π° branching ratio is τ/B > 1.9 × 1031 yr. (90% confidence). Observed cosmic ray muons and neutrinos are compatible with expectations.