Precision Measurement of the Decay Σ^{+}→pγ in the Process J/ψ→Σ^{+}Σ[over ¯]^{-}.

Area of Science:

• Particle Physics
• Hadron Spectroscopy
• Quantum Chromodynamics

Background:

• Hyperon decays provide crucial insights into the fundamental forces governing particle interactions.
• Previous measurements of the radiative hyperon decay Sigma+ -> p gamma have shown discrepancies.
• The BESIII experiment offers a unique opportunity to study rare particle decays with high precision.

Purpose of the Study:

• To precisely measure the absolute branching fraction of the radiative hyperon decay Sigma+ -> p gamma.
• To determine the decay asymmetry parameter for Sigma+ -> p gamma.
• To compare these measurements with existing theoretical predictions and experimental world averages.

Main Methods:

• Analysis of (10,087±44)×10^6 J/ψ events collected by the BESIII detector.
• Application of advanced statistical methods to isolate the signal from background processes.
• Rigorous systematic uncertainty evaluation to ensure the reliability of the results.

Main Results:

• The absolute branching fraction was measured to be (0.996±0.021_stat±0.018_syst)×10^-3, significantly lower than the world average.
• The decay asymmetry parameter was determined to be -0.652±0.056_stat±0.020_syst.
• The precision of the branching fraction and asymmetry parameter measurements were improved by 78% and 34%, respectively.

Conclusions:

• The precise measurement of the radiative hyperon decay Sigma+ -> p gamma challenges current theoretical models.
• This study provides the most accurate data to date for this decay, paving the way for refined theoretical calculations.
• The findings highlight the importance of high-statistics experiments like BESIII in advancing our understanding of particle physics.