Effects of QCD Vacuum and Stability of H Dihyperon

Within the composite quark model taking into account the interaction of quarks in the bag with vacuum fields of QCD the masses of H (I=0,S=-2,J=0,1^C) and H* (I=0,S=-2,J=1,1^C) dihyperons are estimated: M_H=2.16 GeV, M_H*=2.34 GeV. It is shown that the leading effect giving a stable with respect to strong decays H dihyperon is the instanton interaction forming diquarks: q^2(J=0,C=3), q^2(J=0,C=6). With the approach developed the contribution of QCD hyperfine interaction is suppressed, and instanton induced three-particle forces in multiquark hadrons (q^3(J=1/2,C=8) - channel) are rather small.