Search for dibaryon production in 4Hep interactions at medium energies

The 4Hep interactions at 2.7 GeV/c and 5 GeV/c initial momenta of alpha-particles are investigated using the 2m liquid hydrogen bubble chamber (the kinetic energies of the initial protons in the nuclear rest frame were Tp = 220 MeV and 620 MeV). The effective mass spectrum of two nucleons from the reactions 4Hep -> dppn and 4Hep -> pppnn was analysed. The narrow structure in the 2p mass spectrum from the quasi-elastic reaction p4He ->nF(pp)d at Tp = 620 MeV (where nF is the fast neutron in the nuclear rest frame) was found which is the evidence of the existence of dibaryon with a mass M2p = 2008 +- 13 MeV and a width Gamma = 20 +- 5 MeV.