@misc{10481/70192,
year = {2021},
month = {7},
url = {http://hdl.handle.net/10481/70192},
abstract = {The standard model of particle physics encapsulates our best current understanding of physics at the smallest scales. A fundamental
axiom of this theory is the universality of the couplings of the different generations of leptons to the electroweak gauge
bosons. The measurement of the ratio of the decay rate of W bosons to τ leptons and muons, R(τ/μ), constitutes an important
test of this axiom. Using 139 fb−1 of proton–proton collisions recorded with the ATLAS detector at a centre-of-mass energy of
13 TeV, we report a measurement of this quantity from di-leptonic tt events where the top quarks decay into a W boson and
a bottom quark. We can distinguish muons originating from W bosons and those originating from an intermediate τ lepton
through the muon transverse impact parameter and differences in the muon transverse momentum spectra. The measured
value of R(τ/μ) is 0.992 ± 0.013 [± 0.007(stat) ± 0.011(syst)] and is in agreement with the hypothesis of universal lepton
couplings as postulated in the standard model. This is the only such measurement from the Large Hadron Collider, so far, and
obtains twice the precision of previous measurements.},
organization = {ANPCyT},
organization = {YerPhI, Armenia},
organization = {Australian Research Council},
organization = {BMWFW, Austria},
organization = {Austrian Science Fund (FWF)},
organization = {Azerbaijan National Academy of Sciences (ANAS)},
organization = {SSTC, Belarus},
organization = {Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPQ)},
organization = {Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP)},
organization = {Natural Sciences and Engineering Research Council of Canada (NSERC)},
organization = {NRC, Canada},
organization = {Canada Foundation for Innovation},
organization = {CERN},
organization = {ANID, Chile},
organization = {Chinese Academy of Sciences},
organization = {Ministry of Science and Technology, China},
organization = {National Natural Science Foundation of China (NSFC)},
organization = {Departamento Administrativo de Ciencia, Tecnologia e Innovacion Colciencias},
organization = {Ministry of Education, Youth & Sports - Czech Republic
Czech Republic Government},
organization = {DNRF, Denmark},
organization = {Danish Natural Science Research Council},
organization = {Centre National de la Recherche Scientifique (CNRS)},
organization = {CEA-DRF/IRFU, France},
organization = {SRNSFG, Georgia},
organization = {Federal Ministry of Education & Research (BMBF)},
organization = {HGF, Germany},
organization = {Max Planck Society},
organization = {Greek Ministry of Development-GSRT},
organization = {RGC, China},
organization = {Hong Kong SAR, China},
organization = {Israel Science Foundation},
organization = {Benoziyo Center, Israel},
organization = {Istituto Nazionale di Fisica Nucleare (INFN)},
organization = {Ministry of Education, Culture, Sports, Science and Technology, Japan (MEXT)},
organization = {Ministry of Education, Culture, Sports, Science and Technology, Japan (MEXT)},
organization = {Japan Society for the Promotion of Science},
organization = {CNRST, Morocco},
organization = {Netherlands Organization for Scientific Research (NWO)},
organization = {Netherlands Government},
organization = {RCN, Norway},
organization = {Ministry of Science and Higher Education, Poland},
organization = {NCN, Poland},
organization = {Portuguese Foundation for Science and Technology
x},
organization = {European Commission},
organization = {MNE/IFA, Romania},
organization = {MES of Russia, Russia Federation},
organization = {NRC KI, Russia Federation},
organization = {JINR},
organization = {Ministry of Education, Science & Technological Development, Serbia},
organization = {MSSR, Slovakia},
organization = {Slovenian Research Agency - Slovenia},
organization = {MIZS, Slovenia},
organization = {DST/NRF, South Africa},
organization = {Spanish Government},
organization = {SRC, Sweden},
organization = {Wallenberg Foundation, Sweden},
organization = {SERI, Switzerland},
organization = {Swiss National Science Foundation (SNSF)},
organization = {canton of Bern, Switzerland},
organization = {canton of Geneva, Switzerland},
organization = {Ministry of Science and Technology, Taiwan},
organization = {Ministry of Energy & Natural Resources - Turkey},
organization = {UK Research & Innovation (UKRI)},
organization = {Science & Technology Facilities Council (STFC)},
organization = {United States Department of Energy (DOE)},
organization = {National Science Foundation (NSF)},
organization = {BCKDF, Canada},
organization = {CANARIE, Canada},
organization = {Compute Canada, Canada},
organization = {CRC, Canada},
organization = {European Research Council (ERC)},
organization = {ERDF, European Union},
organization = {Horizon 2020, European Union},
organization = {Marie Sklodowska-Curie Actions, European Union},
organization = {COST, European Union},
organization = {French National Research Agency (ANR)},
organization = {German Research Foundation (DFG)},
organization = {Alexander von Humboldt Foundation},
organization = {Herakleitos programme},
organization = {Thales Group},
organization = {Aristeia programme},
organization = {EU-ESF, Greece},
organization = {Greek NSRF, Greece},
organization = {BSF-NSF, Israel},
organization = {German-Israeli Foundation for Scientific Research and Development},
organization = {La Caixa Banking Foundation, Spain},
organization = {CERCA Programme Generalitat de Catalunya, Spain},
organization = {PROMETEO Programme Generalitat Valenciana, Spain},
organization = {GenT Programme Generalitat Valenciana, Spain},
organization = {Goran Gustafssons Stiftelse, Sweden},
organization = {Royal Society of London},
organization = {Leverhulme Trust},
publisher = {Nature},
title = {Test of the universality of τ and μ lepton couplings in W-boson decays with the ATLAS detector},
doi = {10.1038/s41567-021-01236-w},
author = {Aad, G. and Aguilar Saavedra, Juan Antonio and Atlas Collaboration},
}