In the standard model of particle physics, the Weinberg angle is an energy dependent parameter which describes the mixing of the electromagnetic and weak interactions. The modified minimal subtraction scheme predicts the scale dependence of the Weinberg angle precisely.
Measurements of the Weinberg angle at various energy scales are essentially important as a precision test of the standard model and search for new physics. The Weinberg angle can be determined via the neutral current interactions. At the low energy scale, a measurement of atomic parity violation (APV) is the most powerful method. In APV experiments, a parity-odd transition induced by the neutral current interaction between the electron and nucleus is observed. The most precise result was obtained by the experiment using cesium atom .
An APV experiment using muonic atoms provides a unique opportunity to search for physics beyond the standard model. In particular, the models predicting lepton-universality breaking are important candidates to be tested. In 1990s, several precursor experiments were carried out at Paul Scherrer Institute . However, no parity-odd transition was observed because of difficulties in the experiment. To revisit this topic, a new experiment using high-intensity pulsed muon beamnand a segmented calorimeter with fast signal-processing is proposed.
The process of interest is the 1S-2S magnetic dipole (M1) transition with single photon emission. The transition is parity-odd and the emission angle of x-rays is asymmetric like the electrons from parity-violating muon decay. The angular asymmetry of x-ray emissions is measured by the calorimeter with a large solid angle and high-rate capability. In this presentation, experimental overview and status of detector development will be discussed.
: J. Guena, M. Lintz, and M. A. Bouchiat, Phys. Rev. A 71, 042108 (2005).
: K. Kirch et al., Phys. Rev. Lett. 78, 4363 (1997).
|Working Group||WG4 : Muon Physics|