Test of charge conjugation invariance

Area of Science:

• Particle Physics
• Quantum Chromodynamics
• Electromagnetic Interactions

Background:

• The eta meson is a key probe for testing fundamental symmetries in particle physics.
• Charge conjugation (C) invariance is a fundamental symmetry that dictates particle-antiparticle equivalence.
• Certain rare decays of the eta meson are forbidden by C invariance, making their observation a test of this symmetry.

Purpose of the Study:

• To experimentally determine upper limits for the branching ratios of two C-violating eta decay modes.
• To provide evidence supporting the C invariance of electromagnetic interactions involving light quarks.
• To constrain theoretical models of particle interactions.

Main Methods:

• Utilized the Crystal Ball multiphoton detector for high-precision measurements.
• Analyzed data to identify and quantify specific eta decay channels.
• Calculated branching ratio upper limits at a 90% confidence level.

Main Results:

• Established an upper limit for the branching ratio of eta to pi0pi0gamma as <5 x 10^-4.
• Established an upper limit for the branching ratio of eta to pi0pi0pi0gamma as <6 x 10^-5.
• Both measured upper limits are consistent with C invariance.

Conclusions:

• The experimental results support the C invariance of isoscalar electromagnetic interactions.
• The findings also support the C invariance of isovector electromagnetic interactions.
• This study contributes to the ongoing verification of fundamental symmetries in the Standard Model.