An Event Mixing Method with Invariant-mass/energy Hierarchy Correspondence cut for Bose--Einstein Correlations in $\pi \pi X$ System

Abstract

A new event mixing constraint, namely invariant-mass/energy hierarchy correspondence (IMEHC) cut, is introduced for the low-multiplicity event mixing technique for the purpose of measuring Bose-Einstein correlations (BEC) in exclusive reactions with ππX final state particles. The mixing cut is relevant to the hierarchy of the invariant mass of πX system and two bosons energy hierarchy. Numerical tests are performed to check the validity of the new mixing method. As long as the measurements of BEC parameters r 0 and λ 2 are considered, this new mixing method is effective to observe BEC effects and the systematic bias of r 0 and λ 2 are smaller than the previously proposed mixing cut.