Test of light-lepton universality in <em>τ</em> decays with the Belle II experiment

We present a measurement of the ratio R<sub>µ</sub> = $\mathcal{B}$($τ^- → µ^-\overline{ν}_µν_τ$)/$\mathcal{B}(τ^- → e^-\overline{ν}_eν_τ$) of branching fractions B of the τ lepton decaying to muons or electrons using data collected with the Belle II detector at the SuperKEKB e<sup>+</sup>e<sup>-</sup> collider. The sample has an integrated luminosity of 362 ± 2 fb<sup>-1</sup> at a centre-of-mass energy of 10.58 GeV. Using an optimised event selection, a binned maximum likelihood ft is performed using the momentum spectra of the electron and muon candidates. The result, R<sub>µ</sub> = 0.9675 ± 0.0007 ± 0.0036, where the first uncertainty is statistical and the second is systematic, is the most precise to date. It provides a stringent test of the light-lepton universality, translating to a ratio of the couplings of the muon and electron to the W boson in τ decays of 0.9974 ± 0.0019, in agreement with the standard model expectation of unity.

Authors

Institutions

Publication Details

Journal
OSTI OAI (U.S. Department of Energy Office of Scientific and Technical Information)
Published
2024-12-02
DOI
https://doi.org/10.1007/jhep08%282024%29205
Primary Topic
Particle physics theoretical and experimental studies
Type
article

Funders

Controls
|||
ALL TIME
JAN
FEB
MAR
APR
MAY
JUN
JUL
AUG
SEP
OCT
article

Test of light-lepton universality in τ decays with the Belle II experiment

I. Adachi
OSTI OAI (U.S. Department of Energy Office of Scientific and Technical Information)
Particle physics theoretical and experimental studies
article

Test of light-lepton universality in τ decays with the Belle II experiment

I. Adachi
article en

Abstract

We present a measurement of the ratio R<sub>µ</sub> = $\mathcal{B}$($τ^- → µ^-\overline{ν}_µν_τ$)/$\mathcal{B}(τ^- → e^-\overline{ν}_eν_τ$) of branching fractions B of the τ lepton decaying to muons or electrons using data collected with the Belle II detector at the SuperKEKB e<sup>+</sup>e<sup>-</sup> collider. The sample has an integrated luminosity of 362 ± 2 fb<sup>-1</sup> at a centre-of-mass energy of 10.58 GeV. Using an optimised event selection, a binned maximum likelihood ft is performed using the momentum spectra of the electron and muon candidates. The result, R<sub>µ</sub> = 0.9675 ± 0.0007 ± 0.0036, where the first uncertainty is statistical and the second is systematic, is the most precise to date. It provides a stringent test of the light-lepton universality, translating to a ratio of the couplings of the muon and electron to the W boson in τ decays of 0.9974 ± 0.0019, in agreement with the standard model expectation of unity.

OSTI OAI (U.S. Department of Energy Office of Scientific and Technical Information)
Campbell Collaboration (NO)
National Science Foundation, U.S. Department of Energy, Alexander von Humboldt-Stiftung, Univerzita Karlova v Praze, Grantová Agentura, Univerzita Karlova, Canarie, University of Tabuk, Vietnam Academy of Science and Technology, Thailand Center of Excellence in Physics, Compute Canada, National Research Foundation of Ukraine, National Research Foundation, Deutsche Forschungsgemeinschaft, Agence Nationale de la Recherche, Ministry of Education, Culture, Sports, Science and Technology, National Natural Science Foundation of China, Grantová Agentura České Republiky, Bundesministerium für Bildung und Forschung, Austrian Science Fund, Generalitat Valenciana, Korea Institute of Science and Technology, Korea Institute of Science and Technology Information, Max-Planck-Gesellschaft, Javna Agencija za Raziskovalno Dejavnost RS, Türkiye Bilimsel ve Teknolojik Araştırma Kurumu, Centre National de la Recherche Scientifique, Natural Science Foundation of Shandong Province, National Research University Higher School of Economics, Ministry of Education and Science of Ukraine, Ministry of Science and Higher Education of the Russian Federation, Istituto Nazionale di Fisica Nucleare, Bundesministerium für Bildung, Wissenschaft und Forschung, National Science and Technology Council, Natural Sciences and Engineering Research Council of Canada, Deutsches Elektronen-Synchrotron, Japan Society for the Promotion of Science, Akademi Sains Malaysia, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Institut National de Physique Nucléaire et de Physique des Particules
Particle physics theoretical and experimental studies
DOIOpen Access PDFOpenAlex
AI Navigator

Ask Laika to Summarize, Analyze, and Connect papers live on the map.

Summarize Papers & Methodologies

Extract key findings, datasets, and comparative methods across publications.

Benchmark Rankings & Visual Analytics

Rank top research institutions, authors, funders, topics, and journals by Field-Weighted Citation Impact (FWCI) and paper volume with instant charts.

Connect Distant Disciplines

Bridge topological clusters on the map to find hidden collaborative intersections.