This paper presents a theoretical analysis of rare Z-boson decays into pseudoscalar quarkonium states (ηc, ηb) accompanied by a lepton pair. The study uses NRQCD to calculate branching fractions and differential distributions, predicting branching fractions several orders of magnitude below current sensitivities but potentially accessible at future Z-factories.
Key findings
Predicted branching fractions for Z→ηcℓ+ℓ− and Z→ηbℓ+ℓ− are 10−9 and 10−10 respectively.
The angular distributions could discriminate between Standard Model predictions and new physics scenarios.
The study establishes a theoretical foundation for experimental searches in rare decay channels.
Limitations & open questions
Current experimental sensitivities are not sufficient to detect the predicted branching fractions.