Journal Article

Test of lepton universality in beauty-quark decays

Olivares, M. E., Vorobyev, V., Benito, C. Marin, Chefdeville, M., De Paula, B. Souza, Alexander, M., Jones, C. R., Durante, P., Malczewski, J. J., Gao, Y., Eschle, J., Yang, Z., Petric, M., Cardinale, R., Meinert, N., Mead, J. V., Barlow, R. J., Schmelling, M., Bruch, D. Vom, Cai, H., Bedeschi, F., Swientek, K., Yang, Y., Stefko, P., Millard, E., Pugatch, V., Ketel, T., Bobulska, D., Ferro-Luzzi, M., Lefèvre, R., Zhang, S., Martin, L. M. Garcia, Solovev, A., Golubkov, D., Passalacqua, B., Lampis, A., Dalseno, J., Jawahery, A., Lai, A., Schneider, O., Rama, M., Bozzi, C., Carniti, P., Tran, M. T., Fontana, M., Straticiuc, M., Diaz, M. Vieites, Ene, A., Smith, E., Zhou, X., Gibson, V., Mulder, M., Jiang, F., Hollitt, S. E., Bezshyiko, Ia, Ribatti, R., Bertella, C., Tuning, N., Cobbledick, J. L., Kvaratskheliya, T., Cazon, B. R. Gruberg, Morris, A. B., Carboni, G., Downes, A. G., Zenaiev, O., Didenko, S., McNulty, R., Baldini, W., Ponce, S., Karacson, M., Nguyen-Mau, C., Marshall, A. M., Bian, L., Pomery, G. J., Decamp, D., Hancock, T. H., Skidmore, N., Chulikov, V., Romanovskiy, V., Malecki, B., Cadeddu, S., Pappagallo, M., Nanut, T., Materok, M., Merl

2022

Overview

The standard model of particle physics currently provides our best description of fundamental particles and their interactions. The theory predicts that the different charged leptons, the electron, muon and tau, have identical electroweak interaction strengths. Previous measurements have shown that a wide range of particle decays are consistent with this principle of lepton universality. This article presents evidence for the breaking of lepton universality in beauty-quark decays, with a significance of 3.1 standard deviations, based on proton–proton collision data collected with the LHCb detector at CERN’s Large Hadron Collider. The measurements are of processes in which a beauty meson transforms into a strange meson with the emission of either an electron and a positron, or a muon and an antimuon. If confirmed by future measurements, this violation of lepton universality would imply physics beyond the standard model, such as a new fundamental interaction between quarks and leptons. The Large Hadron Collider beauty collaboration reports a test of lepton flavour universality in decays of bottom mesons into strange mesons and a charged lepton pair, finding evidence of a violation of this principle postulated in the standard model.

• Publisher: Nature Publishing Group UK,Nature Publishing Group,Nature Publishing Group (NPG)
• Subject: 639/766/419/1131 / Atomic / Classical and Continuum Physics / Complex Systems / Condensed Matter Physics / Electroweak interactions (field theory) / Elementary particles / experimental particle physics / Flavor (particle physics) / Large Hadron Collider / Leptons / Mathematical and Computational Physics / Matter & antimatter / Mesons / Molecular / Muons / Optical and Plasma Physics / Particle collisions / Particle decay / Particle physics / Physics / Physics and Astronomy / Protons / Quarks / Standard model (particle physics) / Theoretical