ИСТИНА

A low-lying resonance in the system of four neutrons (tetraneutron) was recently first observed by Kisamori et a. To the best of our knowledge, a theoretical description of this resonance was presented only in our paper A. M. Shirokovet al., Phys. Rev. Lett. 117, 182502 (2016) where we used the JISP16 NN interaction and a recently proposed Single-State HORSE formalism extended to the case of democratic decays which is able to extract resonance energies and widths from the results of the No-Core Shell Model (NCSM) calculations. A further development of the Single-State HORSE formalism together with new results obtained with various models of inter-nucleon interactions in extended NCSM model spaces will be presented.