First Measurement of the Michel Parameter?0 in the t- ? μ- ?-μ?t Decay at Belle

Result code in IS VaVaI
<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F00216208%3A11320%2F23%3A10476474" target="_blank" >RIV/00216208:11320/23:10476474 - isvavai.cz</a>
Result on the web
<a href="https://verso.is.cuni.cz/pub/verso.fpl?fname=obd_publikace_handle&handle=dz016zPgmi" target="_blank" >https://verso.is.cuni.cz/pub/verso.fpl?fname=obd_publikace_handle&handle=dz016zPgmi</a>
DOI - Digital Object Identifier
<a href="http://dx.doi.org/10.1103/PhysRevLett.131.021801" target="_blank" >10.1103/PhysRevLett.131.021801</a>

Result language
angličtina
Original language name
First Measurement of the Michel Parameter?0 in the t- ? μ- ?-μ?t Decay at Belle
Original language description
We report the first measurement of the Michel parameter & xi;0 in the & tau;- & RARR; & mu;- & nu; over bar & mu;& nu;& tau; decay with a new method proposed just recently. The measurement is based on the reconstruction of the & tau;- & RARR; & mu;- & nu; over bar & mu;& nu;& tau; events with subsequent muon decay in flight in the Belle central drift chamber. The analyzed data sample of 988 fb-1 collected by the Belle detector corresponds to approximately 912 x 106 & tau;+& tau;- pairs. We measure & xi;0 = 0.22 & PLUSMN; 0.94(stat) & PLUSMN; 0.42(syst), which is in agreement with the standard model prediction of & xi;0 = 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.
Czech name
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Czech description
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Type
J<sub>imp</sub> - Article in a specialist periodical, which is included in the Web of Science database
CEP classification
—
OECD FORD branch
10300 - Physical sciences

Project
<a href="/en/project/GA22-18469S" target="_blank" >GA22-18469S: Studies of the Beyond Standard Model phenomena in the flavor sector with the Belle II Experiment</a><br>
Continuities
P - Projekt vyzkumu a vyvoje financovany z verejnych zdroju (s odkazem do CEP)

Publication year
2023
Confidentiality
S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

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