Formation of Dineutron in the Reaction of Stopped Pion Absorption 9Be(π−, t 4He)2n

The formation of dineutron (2n) was studied in the reaction of stopped pion absorption 9Be(π−, t 4He)2n. The measurements were performed using a two-arm multilayer semiconductor spectrometer. In the spectrum of the missing masses of the reaction under study, a peak near the threshold was observed due to the formation of the s-wave virtual state of the dineutron. No indications of the formation of highly excited states in the two-neutron system were found.