Strong enhancement of varepsilon(')/varepsilon through final state interactions

Area of Science:

• Particle Physics
• Quantum Chromodynamics
• Hadron Spectroscopy

Background:

• The weak K-->2pi decay is a key process for testing the Standard Model of particle physics.
• Theoretical predictions for the CP-violating parameter epsilon prime/epsilon have historically shown discrepancies with experimental measurements.
• The role of final state interactions in these amplitudes has been a subject of theoretical investigation.

Purpose of the Study:

• To quantify the impact of strong final state interactions on weak K-->2pi decay amplitudes.
• To investigate the contribution of these interactions to the DeltaI = 1/2 amplitude.
• To improve the theoretical prediction of epsilon prime/epsilon by incorporating these effects.

Main Methods:

• Utilizing measured pi-pi phase shifts for J = 0 and I = 0,2.
• Quantifying the rescattering effects of the two-pion final state.
• Calculating the enhancement of the DeltaI = 1/2 amplitude.

Main Results:

• Strong final state interactions provide a significant enhancement to the DeltaI = 1/2 amplitude.
• This enhancement was previously neglected in theoretical calculations of epsilon prime/epsilon.
• The inclusion of this correction brings the Standard Model prediction of epsilon prime/epsilon into good agreement with experimental values.

Conclusions:

• Final state interactions are crucial for accurately describing weak K-->2pi decays.
• The enhanced DeltaI = 1/2 amplitude reconciles theoretical predictions with experimental observations of epsilon prime/epsilon.
• This work highlights the importance of non-perturbative effects in Standard Model tests.