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First measurement of the Michel parameter $\xi^\prime$ in the $\tau^-\to\mu^-\bar{\nu}_\mu\nu_\tau$ decay at Belle
- Source :
- Phys. Rev. Lett. 131 (2023) 021801
- Publication Year :
- 2023
-
Abstract
- We report the first measurement of the Michel parameter $\xi^\prime$ in the $\tau^-\to\mu^-\bar{\nu}_\mu\nu_\tau$ decay with a new method proposed just recently. The measurement is based on the reconstruction of the $\tau^-\to\mu^-\bar{\nu}_\mu\nu_\tau$ events with subsequent muon decay-in-flight in the Belle central drift chamber. The analyzed data sample of $988\,\text{fb}^{-1}$ collected by the Belle detector corresponds to approximately $912\times10^6$ $\tau^+ \tau^-$ pairs. We measure $\xi^\prime=0.22\pm0.94(\text{stat})\pm0.42(\text{syst})$, which is in agreement with the standard model prediction of $\xi^\prime=1$. Statistical uncertainty dominates in this study, being a limiting factor, while systematic uncertainty is well under control. Our analysis proved the practicability of this promising method and its prospects for further precise measurement in future experiments.<br />Comment: 6 pages, 4 figures, published in Phys. Rev. Lett
- Subjects :
- High Energy Physics - Experiment
Subjects
Details
- Database :
- arXiv
- Journal :
- Phys. Rev. Lett. 131 (2023) 021801
- Publication Type :
- Report
- Accession number :
- edsarx.2303.10570
- Document Type :
- Working Paper
- Full Text :
- https://doi.org/10.1103/PhysRevLett.131.021801