An event-mixing method using energy hierarchy constraint for two-pion Bose–Einstein correlations measurements in ππx system

Abstract

For the measurement of two-pion Bose–Einstein correlations (BEC) in reactions with [Formula: see text] final state particles, a new event-mixing technique is proposed. The new technique introduces a new mixing constraint, namely energy hierarchy correspondence (EHC) cut, which requires that two bosons being swapped should be equal in energy hierarchy in their original events. Numerical tests are performed to check the validity of the new mixing method. Compared to the previous proposed mixing technique (He et al., Chin. Phys. C 42 (2018) 074004), this new method has smaller systematic uncertainties, improving the accuracy of fit BEC parameters.