Laser-assisted muon decay

We show theoretically that the muon lifetime can be changed dramatically by embedding the decaying muon in a strong linearly polarized laser field. Evaluating the S-matrix elements taking all electronic multiphoton processes into account we find that a CO(2) laser with an electric field amplitude of 10(6) V cm(-1) results in an order of magnitude shorter lifetime of the muon. We also analyze the dependencies of the decay rate on the laser frequency and intensity.     

Unparticles and muon decay

Recently Georgi has discussed the possible existence of ‘Unparticles’ describable by operators having non-integral scaling dimensions. With the interaction of these with the Standard Model particles being constrained only by gauge and Lorentz symmetries, it affords a new source for lepton flavour violation. Current and future muon decay experiments are shown to be very sensitive to such scenarios.     

CPT-violating effects in muon decay

We consider low-energy CPT-violating modifications in charged current weak interactions and analyze possible ramifications in muon and antimuon decays. We calculate the lifetime of muon and antimuon with these modifications, and from the result, put bounds on the CPT-violating parameters. Moreover, we elaborate on the muon and antimuon decay rate differentials in electron energy and spatial angle, which entail interesting phenomenological consequences presenting new ways to constrain CPT violation in charged lepton decays.     

The neutrinos in muon decay

We review the available information on the identity of the neutrino states emitted in muon decay, and discuss the exotic decay .     

Time dilations in bound muon decay

A number of experiments show that the decay lifetimes of muons bound to atomic nuclei are longer than the decay lifetimes of free muons. The special relativistic time dilation predicts decay lifetime dilations that are substantially smaller than the observed decay lifetime dilations. In this paper it is shown that adding a recently predicted electro-magnetic time dilation (analogous to the gravitational time dilation) to the special relativistic time dilation gives a total time dilation that agrees with the observed decay lifetime dilations.     

Experimental constraints on left-right symmetric models from muon decay

The TWIST Collaboration has completed a new measurement of the energy-angle spectrum of positrons from the decay of highly polarized muons. A simultaneous measurement of the muon decay parameters ρ, δ, and P(μ)(π)ξ tests the standard model in a purely leptonic process and provides improved limits for relevant extensions to the standard model. Specifically, for the generalized left-right symmetric model |(g(R)/g(L))ζ|<0.020 and (g(L)/g(R))m(2)>578 GeV/c(2), both 90% C.L.     

Search for right-handed currents in muon decay

We report new limits on right-handed currents, based on precise measurements of the endpoint of the e⁺ spectrum from ⁺ decay. Highly polarized ⁺ from the TRIUMF surface beam were stopped in pure metal foils within either an 1.1-T spin-holding logitudinal field, or a 70-gauss spin-precessing transverse field. Decay e⁺ emitted within 200 mrad of the beam direction were momentum-analyzed to ±0.2%. For the spin-held data, decay via (V-A) currents requires the e⁺ rate to approach zero in the beam direction at the endpoint. Measurement of this rate sets the 90%-confidence limits P />0.9959 and M(W_R)>380 GeV, where W_R is the possible right-handed gauge boson. For the spin-precessed data we independently determine a 90% confidence limit P />0.9918.We are indebted to the entire TRIUMF management and staff for their splendid support of this experiment. In its early stages we benefited from discussion with J. Brewer, R. Cahn, K. Crowe, and W. Wenzel. Rapid commissioning of the polarimeter was made possible by the superb efforts of the LBL support staff. This research was supported in part by the U.S. Department of Energy, Division of Basic Energy Sciences, Office of Energy Research under contracts W-7405-ENG-48 and AC02-ER02289.     

New phenomena in laser-assisted scattering of an electron by a muon

The scattering of an electron by a muon in the presence of a linearly polarized laser field is investigated in the first Born approximation. The theoretical results reveal the following: i) At medium and large scattering angles, many multiphoton processes occur during scattering, and these nonlinear phenomena may predict the resonant state of the electron and the muon formed in the collision process. ii) The photoabsorption (inverse bremsstrahlung) dominates the photoemission (bremsstrahlung), causing the cross section to increase. iii) When the laser polarization deviates from the incident direction, the lasermodified total cross section depends considerably on the azimuthal angle of the scattered electron. The dependence of the cross section on the field strength, polarization direction, and electron-impact energy are studied.     

First-order radiative corrections to polarized muon decay spectrum

The first-order QED corrections to the polarized muon decay spectrum are considered. The exact dependence on electron and muon masses is kept. Numerical results are presented.     

Inverse muon decay in a steady external field

A standard Weinberg-Salam model has been used to calculate the cross section of +e »v _e+ in steady crossed fields (EH=E ²–H ²=0). The asymptotic behavior of the cross section has been examined as a function of the kinematic and dynamic (field) invariant parameters.M. V. Lomonosov Moscow State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 106–111, December, 1992.     

Electron (muon) decay of a heavy lepton

Expressions are derived for the differential probability for the decay e(). The possibly nonzero mass of and the polarizations of both the decaying lepton and the charged lepton which is produced are all taken into account. A quantitative analysis is carried out for various masses of the neutrino and for various energies of the lepton emitted during the decay.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 97–100, June 1981.