A.D. Hancock

The time-of-flight system for CLAS

The time-of-flight system for the CEBAF Large Acceptance Spectrometer (CLAS) at the Thomas Jefferson National Accelerator Facility is described. The system, covering an area of 206-square-meters, is composed of scintillation counters 5.08 cm thick, 15 and 22 cm wide, and lengths which vary from 32 cm at the most forward angle to 450 cm at larger angles. All of the components of the system have been designed to optimize the time resolution. Event timing, achieved by leading-edge discrimination with time-walk correction, has been measured with cosmic rays, a laser pulser, and known particle interactions. The intrinsic time resolution varies from about 80 ps for the short counters to 160 ps for the longer counters. Reconstruction of interacting particles during the first period of operation yields an average time resolution for electrons of 163 ps.

Search for the weak decay of an H dibaryon.

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.}

A compact beam stop for a rare kaon decay experiment

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.

Search for the presence of H particles in a neutral beam

Abstract A search was made to detect the presence of long-lived H particles in a neutral beam by diffractive dissociation into two lambda particles. Preliminary results are presented.

A straw drift chamber spectrometer for studies of rare kaon decays

We describe the design, construction, readout, tests, and performance of planar drift chambers, based on 5-mm-diameter copperized Mylar and Kapton straws, used in an experimental search for rare kaon decays. The experiment took place in the high-intensity neutral beam at the Alternating Gradient Synchrotron of Brookhaven National Laboratory, using a neutral beam stop, two analyzing dipoles, and redundant particle identification to remove backgrounds.

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

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

DIFFUSION OF MUONIC DEUTERIUM AND HYDROGEN ATOMS

K^0_L \to \mu^\pm e^\mp

Search for the weak decay of an H dibaryon

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

Search for diffractive dissociation of a long-lived H dibaryon.

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

Addendum to “Search for the weak decay of anHdibaryon”

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