Related papers: TWIST: Precision Measurement of the Muon Decay Par…
The TWIST Collaboration has completed its measurement of the three muon decay parameters \rho, \delta, and P_\mu\xi. This paper describes our determination of \rho, which governs the shape of the overall momentum spectrum, and \delta, which…
The TWIST collaboration has performed new measurements of two of the parameters that describe muon decay: $\rho$, which governs the shape of the overall momentum spectrum, and $\delta$, which governs the momentum dependence of the…
The TRIUMF Weak Interaction Symmetry Test (TWIST) experiment was designed to test the standard model at high precision in the purely leptonic decay of polarized muons. A general four-fermion interaction model is used to describe the muon…
The muon decay parameter delta characterizes momentum dependence of the parity-violating muon decay asymmetry. A new measurement of delta has been performed using the first physics data recorded by the TWIST experiment at TRIUMF. The…
The muon decay parameter delta has been measured by the TWIST collaboration. We find delta = 0.74964 +- 0.00066(stat.) +- 0.00112(syst.), consistent with the Standard Model value of 3/4. This result implies that the product Pmuxi of the…
To measure the muon decay parameters with high accuracy, we require an array of precision drift detector layers whose relative position is known with very high accuracy. This article describes the design, construction and performance of…
The TWIST Collaboration has measured the Michel parameter $\rho$ in normal muon decay, $\mu^+ \to e^+ \nu_e \bar{\nu}_{\mu}$. In the Standard Model, $\rho$ = 3/4. Deviations from this value require mixing of left- and right-handed muon and…
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 {\rho}, {\delta}, and (P_{\mu}){\xi} tests…
We present a new high precision measurement of parity violation in the weak interaction, using polarized muon decay. The TWIST collaboration has measured $P_\mu^\pi \xi$, where $P_\mu^\pi$ is the polarization of the muon in pion decay and…
We compute the spin asymmetry of the muon decay through O(alpha^2) in perturbative QED. These two-loop corrections are about a factor five (twenty) smaller than the current statistical (systematic) uncertainty of the most precise…
We have studied the muon decay energy spectrum from a sample of stopping muon events acquired during the test run of the ICARUS T600 prototype. This detector allows the spatial reconstruction of the events with fine granularity, hence the…
A low mass time expansion chamber (TEC) has been developed to measure distributions of position and angle of the TRIUMF low energy surface muon beam used for the TWIST experiment. The experiment is a high precision measurement of muon decay…
We compute the dominant, logarithmically enhanced radiative corrections to the electron spectrum in the bound muon decay in the whole experimentally interesting range. The corrected spectrum fits well the TWIST results. The remaining…
We compute the complete O(alpha^2) QED corrections to the electron energy spectrum in unpolarized muon decay, including the full dependence on the electron mass. Our calculation reduces the theoretical uncertainty on the electron energy…
Examples are given which prove the ICARUS detector quality through relevant physics measurements. We study the muon decay energy spectrum from a sample of stopping muon events acquired during the test run of the ICARUS T600 detector. This…
The quantity P_{mu}^{pi}xi, where xi is one of the muon decay parameters and $P_{\mu}^{\pi}$ is the degree of muon polarization in pion decay, has been measured. The value P_{mu}^{pi}xi = 1.0003 +- 0.0006 stat. +- 0.0038 syst. was obtained.…
O(\alpha^2 \ln(m_\mu/m_e)) corrections to electron energy spectrum in muon decay are computed using perturbative fragmentation function approach. The magnitude of these corrections is comparable to anticipated precision of the TWIST…
The electroweak corrections at the order of $O(\alpha_{ew}m_{t(b)}^2/m_W^2)$ to the partial widths of the $\tilde{t}_2 \to \tilde{g} + t$ and $\tilde{g} \to \tilde{t}_1 + \bar{t} $ decays (depending on the masses of the particles involved)…
We review the current status of precision measurements in allowed nuclear beta decay, including neutron decay, with emphasis on their potential to look for new physics beyond the standard electroweak model. The experimental results are…
A search for T-violating muon polarization in the $K^+ \to \pi^0 \mu^+\nu$ decay has been performed at KEK using stopped kaons. A new improved limit was obtained, $P_T= -0.0017 \pm 0.0023 (stat) \pm 0.0011 (syst)$, corresponding to a 90 %…