@Article{ATLASCollaborationAad_etal2021, author="ATLAS Collaboration (Aad, G. et al and Aparisi Pozo, J. A. and Bailey, A. J. and Cabrera Urban, S. and Cardillo, F. and Castillo, F. L. and Castillo Gimenez, V. and Costa, M. J. and Escobar, C. and Estrada Pastor, O. and Ferrer, A. and Fiorini, L. and Fullana Torregrosa, E. and Fuster, J. and Garcia, C. and Garcia Navarro, J. E. and Gonzalez de la Hoz, S. and Gonzalvo Rodriguez, G. R. and Guerrero Rojas, J. G. R. and Higon-Rodriguez, E. and Lacasta, C. and Lozano Bahilo, J. J. and Mamuzic, J. and Marti-Garcia, S. and Martinez Agullo, P. and Mitsou, V. A. and Moreno Llacer, M. and Poveda, J. and Prades Iba{\~{n}}ez, A. and Rodriguez Bosca, S. and Ruiz-Martinez, A. and Sabatini, P. and Salt, J. and Santra, A. and Sayago Galvan, I. and Soldevila, U. and Sanchez, J. and Torro Pastor, E. and Valero, A. and Valls Ferrer, J. A. and Villaplana Perez, M. and Vos, M.", title="Search for charged-lepton-flavour violation in Z-boson decays with the ATLAS detector", journal="Nature Physics", year="2021", publisher="Nature Research", volume="17", pages="819--825", abstract="Leptons with essentially the same properties apart from their mass are grouped into three families (or flavours). The number of leptons of each flavour is conserved in interactions, but this is not imposed by fundamental principles. Since the formulation of the standard model of particle physics, the observation of flavour oscillations among neutrinos has shown that lepton flavour is not conserved in neutrino weak interactions. So far, there has been no experimental evidence that this also occurs in interactions between charged leptons. Such an observation would be a sign of undiscovered particles or a yet unknown type of interaction. Here the ATLAS experiment at the Large Hadron Collider at CERN reports a constraint on lepton-flavour-violating effects in weak interactions, searching for Z-boson decays into a tau lepton and another lepton of different flavour with opposite electric charge. The branching fractions for these decays are measured to be less than 8.1 x 10(-6) (e tau) and 9.5 x 10(-6) (mu tau) at the 95{\%} confidence level using 139 fb(-1) of proton-proton collision data at a centre-of-mass energy of root s = 13 TeV and 20.3 fb(-1) at root s = 8 TeV. These results supersede the limits from the Large Electron-Positron Collider experiments conducted more than two decades ago.", optnote="WOS:000668820400003", optnote="exported from refbase (https://references.ific.uv.es/refbase/show.php?record=4892), last updated on Wed, 11 Aug 2021 11:56:46 +0000", issn="1745-2473", doi="10.1038/s41567-021-01225-z", opturl="https://arxiv.org/abs/2105.12491", opturl="https://doi.org/10.1038/s41567-021-01225-z", language="English" }