High Energy Physics - Experiment
[Submitted on 19 Mar 2023 (v1), last revised 12 Jul 2023 (this version, v3)]
Title:First measurement of the Michel parameter $ξ^\prime$ in the $τ^-\toμ^-\barν_μν_τ$ decay at Belle
View PDFAbstract: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.
Submission history
From: Denis Bodrov [view email][v1] Sun, 19 Mar 2023 05:19:08 UTC (205 KB)
[v2] Mon, 29 May 2023 15:39:40 UTC (232 KB)
[v3] Wed, 12 Jul 2023 06:06:31 UTC (232 KB)
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