The rate for Z0→J/ψ+l+l- is surprisingly large with about one event for every million Z0 decays. The reason for this is that there is a fragmentation contribution that is not suppressed by a factor of Mψ2/MZ2. In the fragmentation limit MZ→ with Eψ/MZ fixed, the differential decay rate for Z0→J/ψ+l+l- factors into electromagnetic decay rates and universal fragmentation functions. The fragmentation functions for lepton fragmentation and photon fragmentation into J/ψ are calculated to the lowest order in α. The fragmentation approximation to the rate is shown to match the full calculation for Eψ greater than about 3Mψ.
ASJC Scopus subject areas
- Physics and Astronomy (miscellaneous)