Scientists propose a hunt for never-before-seen ‘tauonium’ atoms 

Proposed new colliders could create particles composed of heavy relatives of the electron

A swirl of two particles represents the tauonium atom in an illustration. The atom has emerged from a particle detector represented by a series of concentric cylinders, centered around a beam line where electrons and positrons enter from either side.

Scientists could create atoms made of tau leptons (illustrated in upper left) using a particle collider that smashes together electrons and positrons (arrows at right and left, respectively).

J.-H. Fu et al/Science Bulletin 2024

Atoms are normally made of a nucleus and electrons. But scientists are proposing a hunt for a new variety of atom without either. Tauonium (sometimes called “ditauonium” or “true tauonium”) would consist of a negatively charged tau lepton, and its positively charged antimatter counterpart, an antitau.

Tau leptons are relatives of electrons. Each tau has about 3,500 times an electron’s mass, making it heavier than a proton. In the 1950s, scientists discovered an atom called positronium, consisting of an electron and its positively charged antiparticle, a positron. Tauonium, if discovered, would be a burlier atom. 

Scientists propose searching for tauonium by smashing electrons and positrons together at a future particle collider designed to produce tau leptons, which has been proposed in both China and Russia. Such facilities could find tauonium within a year of starting up, physicist Jing-Hang Fu of Beihang University in Beijing and colleagues report April 4 in Science Bulletin. The researchers propose looking at the ratio of the probability of two different types of particle interactions in the collisions, to reduce experimental uncertainty.

With the complexity of the atomic nucleus out of the picture, studies of tauonium could scrutinize the physics theory that describes electrically charged particles, quantum electrodynamics. Studies of positronium have already been used to test the theory (SN: 8/24/20).

Physics writer Emily Conover has a Ph.D. in physics from the University of Chicago. She is a two-time winner of the D.C. Science Writers’ Association Newsbrief award.

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