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In case of chiral U A(1) symmetry restoration the mass of the boson (the ninth, would-be Goldstone boson) is decreased, thus its production cross-section is heavily enhanced. The decays (through one of its decay channels) into five low-momentum pions. These pions will not contribute to measured Bose-Einstein correlations, thus the production enhancement changes the strength of two-pion correlation functions at low momentum. Preliminary results on Bose-Einstein correlation functions support the mass decrease of the boson. In this paper we propose a method to select pions originating from decays. We investigate the efficiency of the proposed kinematical cut in several collision systems and energies with several simulators. We prove that our method can be used in all investigated collision systems.