Study of the muon decay-in-flight in the τ- → μ-(ν)over-barμνt decay to measure the Michel parameter ξ'

Result code in IS VaVaI
<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F00216208%3A11320%2F23%3A10476457" target="_blank" >RIV/00216208:11320/23:10476457 - isvavai.cz</a>
Result on the web
<a href="https://verso.is.cuni.cz/pub/verso.fpl?fname=obd_publikace_handle&handle=F_OVdB1egS" target="_blank" >https://verso.is.cuni.cz/pub/verso.fpl?fname=obd_publikace_handle&handle=F_OVdB1egS</a>
DOI - Digital Object Identifier
<a href="http://dx.doi.org/10.1103/PhysRevD.108.012003" target="_blank" >10.1103/PhysRevD.108.012003</a>

Result language
angličtina
Original language name
Study of the muon decay-in-flight in the τ- → μ-(ν)over-barμνt decay to measure the Michel parameter ξ'
Original language description
We present the first measurement of the Michel parameter.0 in the tau(-) -> mu(-)(nu) over bar (mu)nu t decay using the full data sample of 988 fb(-1) collected by the Belle detector operating at the KEKB asymmetric energy ethornecollider. The method is based on the reconstruction of the mu(-) -> e(-)(nu) over bar (e)nu(mu) decay-in-flight in the Belle central drift chamber and relies on the correlation between muon spin and its daughter electron momentum. We study the main sources of the background that can imitate the signal decay, such as kaon and pion decays-in-flight and charged particle scattering on the detector material. Highly efficient methods of their suppression are developed and applied to select 165 signal-candidate events. We obtain xi' = 0.22 +/- 0.94 +/- 0.42 where the first uncertainty is statistical, and the second one is systematic. The result is in agreement with the Standard Model prediction of xi' = 1.
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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