Search for rare and forbidden eta(') decays

Area of Science:

• Particle Physics
• Experimental Particle Physics
• Hadron Spectroscopy

Background:

• The eta prime (η′) meson is a key player in understanding quantum chromodynamics.
• Investigating rare and forbidden decays provides crucial insights into fundamental symmetries and potential new physics.

Purpose of the Study:

• To search for and set limits on rare and forbidden decays of the eta prime (η′) meson.
• To analyze the Dalitz plot of the η′ → π⁺π⁻η decay to determine its matrix element.

Main Methods:

• Analysis of 4.80 fb⁻¹ of e⁺e⁻ collision data collected at the Cornell Electron Storage Ring using the CLEO II detector.
• Searched for specific decay channels: η′ → e⁺e⁻η, η′ → e⁺e⁻π⁰, η′ → e⁺e⁻γ, and η′ → e⁺μ⁻.
• Fitted the Dalitz plot for the η′ → π⁺π⁻η decay using a specific parametrization.

Main Results:

• No significant signals were observed for the searched rare and forbidden eta prime (η′) decays.
• Established 90% confidence level upper limits on branching fractions for these decays, with values such as B(η′ → e⁺e⁻η) < 2.4 × 10⁻³, and B(η′ → e⁺μ⁻) < 4.7 × 10⁻⁴.
• Determined the real part of the parameter α in the η′ → π⁺π⁻η decay matrix element to be Re(α) = -0.021 ± 0.025.

Conclusions:

• The absence of signals for these rare decays places stringent constraints on theoretical models.
• The measured value of Re(α) for the η′ → π⁺π⁻η decay is consistent with expectations from chiral perturbation theory.
• This study contributes to the precise characterization of eta prime (η′) meson properties and searches for new physics phenomena.