Determination of the quadratic slope parameter in eta-->3pi(0) decay

Area of Science:

• Particle Physics
• Hadron Spectroscopy
• Quantum Chromodynamics

Background:

• The eta meson is a key particle in understanding the strong nuclear force.
• Precise measurement of its decay properties provides critical tests for fundamental theories.
• Current chiral perturbation theory (ChPT) calculations for eta decays require experimental verification.

Purpose of the Study:

• To determine the quadratic slope parameter alpha for the eta --> 3pi(0) decay with high precision.
• To compare the experimental result with predictions from chiral perturbation theory.
• To improve the accuracy of measurements for eta meson properties.

Main Methods:

• Utilized a high-purity sample of 10^6 eta --> 3pi(0) decays.
• Collected data from the reaction pi(-)p --> n(eta) near the eta threshold.
• Employed the Crystal Ball detector at the Alternating Gradient Synchrotron (AGS) for data acquisition.

Main Results:

• Determined the quadratic slope parameter alpha for eta --> 3pi(0) to be -0.031(4).
• Achieved a precision four times greater than the current world average for this parameter.
• Observed a significant deviation (approximately four standard deviations) from established ChPT calculations.

Conclusions:

• The precise measurement of alpha provides a stringent test for ChPT.
• The discrepancy suggests potential refinements are needed in current theoretical models of meson decays.
• This finding opens new avenues for exploring the strong interaction at low energies.