Physicists Tighten Constraints on Hypothetical Particles Beyond Known Physics
Researchers using China's BESIII detector have completed the first search for an invisible particle in a specific type of particle decay, finding no evidence but setting strict limits on where such particles could hide. The result narrows the search space for physics beyond the Standard Model, informing where future experiments should focus resources and attention.
Originaltitel: Search for a massless particle beyond the Standard Model in the Ξ0 → Λ + invisible decay
A bstract A search for a massless beyond-standard-model particle is performed in the decay Ξ 0 → Λ + invisible using (1.0087 ± 0.0044) × 10 10 J / ψ events collected with the BESIII detector at the BEPCII collider. No significant signal is observed and the upper limit on the branching fraction ℬ(Ξ 0 → Λ + invisible) is set to be 2.3 × 10 − 4 at the 90% confidence level. This is the first search for a flavor-changing neutral current process with missing energy in Ξ 0 decays. Throughout this paper, charge-conjugate processes are always implied.