Quantum electrodynamics (QED) atoms are composed of unstructured and point-like lepton pairs bound together by the electromagnetic force.
An artist’s impression of true tauonium. Image credit: Fu et al., doi: 10.1016/j.scib.2024.04.003.
“QED atoms are formed of lepton pairs by electromagnetic interactions, similar to hydrogen formed of a proton and an electron,” said Beihang University physicist Jing-Hang Fu and colleagues.
“Their properties have been studied to test QED theory, fundamental symmetries, gravity, and search for physics beyond the Standard Model, and so on.”
“The first QED atom was discovered in 1951, which is the bound state and named positronium.”
“The second one was discovered in 1960, which is the bound state and named muonium.”
“No other QED atom was found in the past 64 years.”
“New colliders are proposed to discover the true muonium, which decays into final states with electrons and photons,” they said.
“The heaviest and smallest QED atom is named tauonium, ditauonium, or true tauonium.”
In a new paper in the journal Science Bulletin, the physicists introduce a novel method for identifying true tauonium.
“Tauonium, composed of a tauon and its antiparticle, has a Bohr radius of only 30.4 femtometers — approximately 1/1741 of the Bohr radius of a hydrogen atom,” they said.
“This implies that tauonium can test the fundamental principles of quantum mechanics and QED at smaller scales, providing a powerful tool for exploring the mysteries of the micro material world.”
“We demonstrate that by collecting data of 1.5 ab-1 near the threshold of tauon pair production at an electron and positron collider, and selecting signal events containing charged particles accompanied by the undetected neutrinos carrying away energy, the significance of observing tauonium will exceed 5
“This indicates a strong experimental evidence for the existence of tauonium.”
“We also found that using the same data, the precision of measuring the tau lepton mass can be improved to an unprecedented level of 1 keV, two orders of magnitude higher than the highest precision achieved by current experiments.”
“This achievement will not only contribute to the precise testing of the electroweak theory in the Standard Model, but also have profound implications for fundamental physics questions such as lepton flavor universality.”
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Jing-Hang Fu et al. Novel method for identifying the heaviest QED atom. Science Bulletin, published online April 4, 2024; doi: 10.1016/j.scib.2024.04.003
