• Physics 16, s91
New information from observations of B-meson decay once more vindicate the usual mannequin of particle physics.
Newly launched information taken utilizing the Belle II experiment at KEK in Japan and the LHCb experiment at CERN in Switzerland present no signal of a potential anomaly that researchers suppose may present a path to overturning the usual mannequin of particle physics [1–3].
In keeping with the usual mannequin, electrons, muons, and tau leptons ought to all behave identically when subjected to any of the elemental forces of nature. Over a decade in the past, researchers started questioning the validity of this assumption—referred to as lepton universality—once they noticed high-energy particle decays that deviated from standard-model predictions. Particularly, the observations involved the decay of B mesons into numerous leptons, with the experiments hinting that just a few extra tau leptons have been being produced than anticipated. Pleasure constructed amongst particle physicists, who hoped they have been on the cusp of discovering the long-sought standard-model violation that will uncover new bodily phenomena. Hopes rose additional as different experiments discovered hints of lepton-universality violations within the decay of B mesons into electrons and muons, however the indicators remained too small to rule out experimental artifacts.
Then on the finish of final 12 months, hopes started to fade when the LHCb Collaboration launched information for B-meson decays involving electrons and muons that precisely matched standard-model predictions [2, 3]. Now information from the Belle II Collaboration for a unique B-meson decay involving electrons and muons dim these hopes additional . The examine gives probably the most exact lepton-universality take a look at but in such decays. However researchers haven’t but given up on leptons unlocking a door to new physics, says Belle II Collaboration member Henrik Junkerkalefeld of the College of Bonn, Germany. He notes that, though the outcomes present new constraints on the choices for undiscovered physics, they don’t utterly rule all of them out.
Katherine Wright is the Deputy Editor of Physics Journal.
- L. Aggarwal et al. (Belle II Collaboration), “Check of light-lepton universality within the charges of inclusive semileptonic B-meson decays at Belle II,” Phys. Rev. Lett. 131, 051804 (2023).
- R. Aaij et al. (LHCb Collaboration), “Check of lepton universality in decays,” Phys. Rev. Lett. 131, 051803 (2023).
- R. Aaij et al. (LHCb Collaboration), “Measurement of lepton universality parameters in and decays,” Phys. Rev. D 108, 032002 (2023).