S.C. Wright

New limit for the family number nonconserving decay mu+ ---> e+ gamma

The transport properties of a quasi-three-dimensional, 200 layer quantum well structure are investigated at integer filling in the quantum Hall state. We find that the transverse magnetoresistance R xx , the Hall resistance R xy , and the vertical resistance R zz all follow a similar behavior with both temperature and in-plane magnetic field. A general feature of the influence of increasing in-plane field B in is that the Hall conductance quantization first improves, but above a characteristic value B C in , the quantization is systematically removed. We consider the interplay of the chid edge state transport and the bulk (quantum Hall) transport properties. This mechanism may arise from the competition of the cyclotron energy with the superlattice band structure energies. A comparison of the resuIts with existing theories of the chiral edge state transport with in-plane field is also discussed.An experiment has been performed to search for the muon- and electron-number non-conserving decay mu+ to e+_gamma. The upper limit for the branching ratio to be GAMMA(mu+ to e+_gamma)/GAMMA(mu+ to e+_nu_nubar) < 1.2e-11 with 90% confidence.

Search for the decay micro+-->e+ gamma.

This Letter reports a new experimental search for the family-number-nonconserving decay ..mu../sup +/ ..-->.. e/sup +/..gamma... There is no evidence for the presence of this decay mode. The upper limit for the branching ratio is GAMMA(..mu.. ..-->.. e..gamma..)/GAMMA(..mu.. ..-->.. enu anti nu) < 4.9 x 10/sup -11/ (90% C.L.). 13 refs., 3 figs.

Design and performance of modularized NaI(Tl) detectors with rectangular crystal elements: An array of 49 and the crystal box

Abstract An array of 49 NaI(Tl) modules each 20 inch in depth and 2.5 inch × 2.5 inch in cross section has been constructed and its properties, especially energy resolution, explored for positrons in the range 20 MeV – 18 GeV. A subsequent much larger detector, the Crystal Box, has also been constructed from 396 modules of the same cross section, but mostly 12 inch in depth, and operated as a γ-ray and positron detector in a search for rare muon decays. The calibration procedure used for the Crystal Box and its characteristic resolutions in energy, impact point and time are described.

New Limit for the Lepton-Family-Number Nonconserving Decayμ+→e+γ

The transport properties of a quasi-three-dimensional, 200 layer quantum well structure are investigated at integer filling in the quantum Hall state. We find that the transverse magnetoresistance R xx , the Hall resistance R xy , and the vertical resistance R zz all follow a similar behavior with both temperature and in-plane magnetic field. A general feature of the influence of increasing in-plane field B in is that the Hall conductance quantization first improves, but above a characteristic value B C in , the quantization is systematically removed. We consider the interplay of the chid edge state transport and the bulk (quantum Hall) transport properties. This mechanism may arise from the competition of the cyclotron energy with the superlattice band structure energies. A comparison of the resuIts with existing theories of the chiral edge state transport with in-plane field is also discussed.An experiment has been performed to search for the muon- and electron-number non-conserving decay mu+ to e+_gamma. The upper limit for the branching ratio to be GAMMA(mu+ to e+_gamma)/GAMMA(mu+ to e+_nu_nubar) < 1.2e-11 with 90% confidence.

The Crystal Box: Rare decays of the muon

Development of the Crystal Box Spectrometer at the Clinton P. Anderson Meson Physics Facility in Los Alamos has been completed. And a search for the rare muon decays mu to e−gamma, to e−2gamma, and to 3e is ready to start taking data. (AIP)

Measurement of the Michel rho parameter in direct muon decay

We report on the status of LAMPF experiment E-1240 to measure the Michel ρ parameter in direct muon decay. This experiment ran in 1993, and the data are currently being analyzed. The expected precision on the ρ parameter is ±0.0008. This result will provide better constraints on new physics, particularly on the charged vector bosons’ mixing angle ζ in the manifestly left-right symmetric extension of the Standard Model.

Measurement of the Michel parameter ρ in normal muon decay

A new measurement of the Michel parameter ρ in normal muon decay has been performed using the MEGA positron spectrometer. Over 500 million triggers were recorded and the data are currently being analyzed. The previous result has a precision on the value of ρ±0.0026. The present experiment expects to improve the precision to ±0.0008 or better. The improved result will be a precise test of the standard model of electroweak interactions for a purely leptonic process. It also will provide a better constraint on the WR−WL mixing angle in the left‐right symmetric models.

Search for the Decayμ+→e+γ

This Letter reports a new experimental search for the family-number-nonconserving decay ..mu../sup +/ ..-->.. e/sup +/..gamma... There is no evidence for the presence of this decay mode. The upper limit for the branching ratio is GAMMA(..mu.. ..-->.. e..gamma..)/GAMMA(..mu.. ..-->.. enu anti nu) < 4.9 x 10/sup -11/ (90% C.L.). 13 refs., 3 figs.

Search for the Decay

This Letter reports a new experimental search for the family-number-nonconserving decay ..mu../sup +/ ..-->.. e/sup +/..gamma... There is no evidence for the presence of this decay mode. The upper limit for the branching ratio is GAMMA(..mu.. ..-->.. e..gamma..)/GAMMA(..mu.. ..-->.. enu anti nu) < 4.9 x 10/sup -11/ (90% C.L.). 13 refs., 3 figs.

\mu^+ \to e^+ \gamma

New experimental upper limits for the branching ratios of the lepton‐family‐number nonconserving decays μ+ → e+γ and μ+ → e+γγ are presented. A new determination of γ, the ratio of pion axial‐vector to vector form factors, from radiative pion decay is also reported. These results are from data taken with the Crystal Box detector at LAMPF.