Search for right-handed currents in muon decay

Technical Report · Wed Jan 01 04:00:00 EST 1986

DOI:https://doi.org/10.2172/6006947· OSTI ID:6006947

Jodidio, A E

Limits are reported on charged right-handed currents, based on precise measurement of the endpoint e/sup +/ spectrum in ..mu../sup +/ decay. Highly polarized ..mu../sup +/ from the TRIUMF ''surface'' muon beam were stopped in high purity metal foils and liquid He targets selected to minimize depolarization effects. Decay e/sup +/ emitted within 160 mrad of the beam direction were momentum-analyzed to 0.15%. Muons were stopped within either a spin-processing transverse field (70-G or 110-G) or a spin-holding longitudinal field (0.3-T or 1.1-T). Data collected with the spin-precessing field were used for the momentum calibration of the spectrometer. The spin-held data were used to measure the relative e/sup +/ rate at the endpoint. An extrapolation was made to extract the endpoint rate opposite to the ..mu../sup +/ spin. In terms of the standard muon decay parameters this rate is given by (1-xi P/sub ..mu../delta/rho) where P/sub ..mu../ is muon polarization. The result for xi P/sub ..mu../delta was consistent with the V-A prediction of 1. It is quoted as a 90% confidence lower limit xi P/sub ..mu../delta/rho > 0.9975 since we are unable to correct for all possible sources of muon depolarization. For the model with manifest left-right symmetry and massless neutrinos the result implies 90% confidence limits m(W/sub 2/) > 432 GeV/c/sup 2/ and -0.050 < xi < 0.035, where W/sub 2/ is the predominantly right-handed boson and xi is the left-right mixing angle. With the assumption of no left-right mixing an equivalent 90% confidence upper limit of 0.025 is obtained on the absolute value of the ratio of a possible V+A amplitude to the dominant V-A amplitude in muon and pion decays. Limits are also deduced on the nu/sub ..mu..L/ mass and helicity in ..pi../sup +/ decay, non-(V-A) couplings in helicity projection form, the mass scale of composite leptons, and the branching ratio for ..-->.. e+f where f (familon) is the neutral massless Nambu-Goldstone boson associated with flavor symmetry breaking. 39 refs., 12 figs.

• Research Organization: Lawrence Berkeley Lab., CA (USA)
• DOE Contract Number: AC02-76ER02289; AC03-76SF00098
• OSTI ID: 6006947
• Report Number(s): LBL-21084; ON: DE86008399
• Country of Publication: United States
• Language: English

Related Subjects

645102* -- High Energy Physics-- Particle Interactions &amp; Properties-Experimental-- Weak Interactions &amp; Properties
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
ALGEBRAIC CURRENTS
ANTILEPTONS
ANTIMATTER
ANTIPARTICLES
BEAMS
BOSONS
CALIBRATION
CHARGED CURRENTS
CURRENTS
DATA
DECAY
ELEMENTARY PARTICLES
EXPERIMENTAL DATA
FERMIONS
GOLDSTONE BOSONS
HELICITY
INFORMATION
LEPTONS
LINEAR MOMENTUM
MASS
MASSLESS PARTICLES
MUONS
MUONS PLUS
NEUTRINOS
NUMERICAL DATA
PARTICLE DECAY
PARTICLE PROPERTIES
POLARIZATION
POLARIZED BEAMS
POSITRONS
POSTULATED PARTICLES
SPECTRA
SYMMETRY BREAKING
WEAK PARTICLE DECAY