Bose-Einstein Correlations of Three Charged Pions in Hadronic Z^0 Decays

TL;DR

This study investigates three-pion Bose-Einstein correlations in Z^0 decays, revealing a significant enhancement near threshold and providing precise measurements of the source radius and correlation strength, with implications for understanding particle emission sources.

Contribution

The paper introduces a new subtraction procedure to isolate genuine three-pion Bose-Einstein correlations, improving accuracy in measuring source parameters in high-energy particle decays.

Findings

Observed a significant three-pion BEC enhancement near threshold.

Measured source radius r_3 = 0.580 +/- 0.004 (stat.) +/- 0.029 (syst.) fm.

Determined correlation strength lambda_3 = 0.504 +/- 0.010 (stat.) +/- 0.041 (syst.).

Abstract

Bose-Einstein Correlations (BEC) of three identical charged pions were studied in 4 x 10^6 hadronic Z^0 decays recorded with the OPAL detector at LEP. The genuine three-pion correlations, corrected for the Coulomb effect, were separated from the known two-pion correlations by a new subtraction procedure. A significant genuine three-pion BEC enhancement near threshold was observed having an emitter source radius of r_3 = 0.580 +/- 0.004 (stat.) +/- 0.029 (syst.) fm and a strength of \lambda_3 = 0.504 +/- 0.010 (stat.) +/- 0.041 (syst.). The Coulomb correction was found to increase the \lambda_3 value by \~9% and to reduce r_3 by ~6%. The measured \lambda_3 corresponds to a value of 0.707 +/- 0.014 (stat.) +/- 0.078 (syst.) when one takes into account the three-pion sample purity. A relation between the two-pion and the three-pion source parameters is discussed.