Group theory for unified model building

Model of 'Calculable' Majorana Neutrino Masses

This article reviews the current theoretical and experimental status of the field of muon decay and its potential to search for new physics beyond the standard model. The importance of rare muon processes with lepton flavor violation is highly stressed, together with precision measurements of normal muon decay. Recent up-to-date motivations of lepton flavor violation based on supersymmetric models, in particular supersymmetric grand unified theories, are described along with other theoretical models. Future prospects of experiments and muon sources of high intensity for further progress in this field are also discussed.

Muon decay and physics beyond the standard model

A Call for New Physics : The Muon Anomalous Magnetic Moment and Lepton Flavor Violation

Massless neutrinos in left-hand symmetric models

An examination of 3.6\ifmmode\times\else\texttimes\fi{}${10}^{10}$ ${\ensuremath{\mu}}^{+}$ decays yields an improved upper limit for the branching ratio $\frac{\ensuremath{\Gamma}({\ensuremath{\mu}}^{+}\ensuremath{\rightarrow}{e}^{+}\ensuremath{\gamma})}{\ensuremath{\Gamma}({\ensuremath{\mu}}^{+}\ensuremath{\rightarrow}{e}^{+}{\ensuremath{\nu}}_{e}{\overline{\ensuremath{\nu}}}_{\ensuremath{\mu}})}l1.9\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}10}$ with 90% confidence.

Upper limit for the decay. mu. /sup +/. -->. e/sup +/. gamma

This paper describes a kinematically complete search for the muon decay ..mu../sup +/..-->..e/sup +/..gamma... The experiment used a magnetic spectrometer outfitted with proportional chambers to measure the positron momentum vector and a large segmented NaI(Tl) array to determine the ..gamma..-ray energy and impact point. The positrons were mostly from normal muon decay while the ..gamma.. rays were mostly from internal and external bremsstrahlung. Approximately 3 x 10/sup 12/ muons were stopped in a 50-mg/cm/sup 2/ polyethylene target. The relative timing between the positron and the ..gamma.. ray was measured with a resolution of 1.9 ns full width at half maximum (FWHM) by the use of a plastic-scintillator hodoscope for the positron and by NaI(Tl) constant-fraction timing for the ..gamma.. ray. The positron energy resolution averaged over all data was 8.8% FWHM, and the ..gamma..-ray energy resolution was 8% FWHM, both at 52.8 MeV. When the ..gamma.. ray is assumed to originate at the same place in the target as the positron, the rms error in the measurement of the angle between the positron and ..gamma..-ray momentum vectors was 37 mrad. The acceptance of the apparatus for ..mu../sup +/..-->..e/sup +/..gamma.. events was (1.75 +- 0.04)%. A maximum-likelihood analysis established a 90%-confidencemore » upper limit for the branching ratio GAMMA(..mu../sup +/..-->..e/sup +/..gamma..)/GAMMA(..mu../sup +/..-->..e..nu nu..) of 1.7 x 10/sup -10/.« less

M.E. Hamm

Papers

Upper limit for the decay. mu. /sup +/. -->. e/sup +/. gamma

Search for. mu. /sup +/. -->. e/sup +/. gamma

On the detection of 50 MeV γ-rays with a large modularized NaI(Tl) detector