  Prior proposed observing approaches using event mixing technique for
Bose-Einstein correlations (BEC) measurements in exclusive reactions with very
low multiplicities are still unsatisfactory due to the problems of sample
reduction and introducing extra and unnecessary fitting parameters. We here
propose an event mixing method with a new mixing cut, named energy sum range
(ESR) cut, to investigate two-pion Bose-Einstein correlations (BEC) in
reactions with only two identical pions among three final state particles. This
mixing method employs two-pion energy sum characteristic to control the mixing
procedures, with no requirement on eliminating any original events. Numerical
simulations are performed to show the viability of this new BEC observing
method.
