K. Lang

Performance of Hamamatsu 64-anode photomultipliers for use with wavelength—shifting optical fibres

Hamamatsu R5900-00-M64 and R7600-00-M64 photomultiplier tubes will be used with wavelength-shifting optical fibres to read out scintillator strips in the MINOS near detector. We report on measurements of the gain, efficiency, linearity, crosstalk, and dark noise of 232 of these PMTs, of which 219 met MINOS requirements.

New limit on muon and electron lepton number violation from K0(L) ---> mu+- e-+ decay

The most sensitive experiment to date to search for the muon and electron lepton number violating decay

Search for the weak decay of an H dibaryon.

K^0_L to mu^pm e^mp

First observation of the rare decay mode K0(L) ---> e+ e-

has detected no events consistent with this process. Based on this result, the 90% confidence level upper limit on the branching fraction is

A comprehensive characterization of Hamamatsu 16- and 64-anode PMTs

B(K^0_L to mu^pm e^mp) < 4.7times10^{-12}

A compact beam stop for a rare kaon decay experiment

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A technique of direct tension measurement of a strung fine wire

We have searched for a neutral {ital H} dibaryon decaying via {ital H}{r_arrow}{Lambda}{ital n} and {ital H}{r_arrow}{Sigma}{sup 0}{ital n}. Our search has yielded two candidate events from which we set an upper limit on the {ital H} production cross section. Normalizing to the inclusive {Lambda} production cross section, we find ({ital d}{sigma}{sub {ital H}}/{ital d}{Omega})/({ital d}{sigma}{sub {Lambda}}/{ital d}{Omega}){lt}6.3{times}10{sup {minus}6} at 90{percent} C.L., for an {ital H} of mass {approx_equal}2.15 GeV/{ital c}{sup 2}. {copyright} {ital 1996 The American Physical Society.}

Search for the presence of H particles in a neutral beam

In an experiment designed to search for and study very rare two-body decay modes of the K-long, we have observed four examples of the decay K-long -> e+ e-, where the expected background is 0.17+-0.10 events. This observation translates into a branching fraction of 8.7^{+5.7}_{-4.1} X 10^{-12}, consistent with recent theoretical predictions. This result represents by far the smallest branching fraction yet measured in particle physics.

A straw drift chamber spectrometer for studies of rare kaon decays

We are reporting preliminary results of studies of R59000-00-M16 and M64 tubes, manufactured by Hamamatsu Photonics, to be employed by the MINOS neutrino experiment. Our tests focused on anode response uniformity, gain, cross-talk, and linearity for light illuminating PMTs through a 1.2 mm diameter fiber.

New Limit on Muon and Electron Lepton Number Violation from K{sup 0}{sub L} {r_arrow} {mu}{sup {plus_minus} }e{sup {minus_plus}} Decay

Abstract We describe the development and testing of a novel beam stop for use in a rare kaon decay experiment at the Brookhaven Alternating Gradient Synchrotron. The beam stop is located inside a dipole spectrometer magnet in close proximity to straw drift chambers and intercepts a high-intensity neutral hadron beam. The design process, involving both Monte Carlo simulations and beam tests of alternative beam-stop shielding arrangements, had the goal of minimizing the leakage of particles from the beam stop and the resulting hit rates in detectors, while preserving maximum acceptance for events of interest. The beam tests consisted of measurements of rates in drift chambers, scintillation counter hodoscopes, a gas threshold Cherenkov counter, and a lead glass array. Measurements were also made with a set of specialized detectors which were sensitive to low-energy neutrons, photons, and charged particles. Comparisons are made between these measurements and a detailed Monte Carlo simulation.