13ΛC hypernucleus studied with the 13C(K-,π-γ) reaction -: art. no. 034607

The C-13(Lambda) hypernucleus was studied by measuring g rays in coincidence with the C-13(K-, pi(-)) reaction. g rays from the 1/2(-) and 3/2(-) states, which are the partners of the spin-orbit doublet states with a predominant configuration of [C-12(g.s.) (0(+))circle timesp(Lambda)], to the ground state were measured. The splitting of the states was found to be DeltaE(1/2(-) -3/2(-)) = 1152 +/- 54(stat) +/- 36(syst) keV. This value is 20-30 times smaller than that of single particle states in nuclei around this mass region. The j(Lambda) = l(Lambda) - 1/2[(p(1/2))(Lambda)] state appeared higher in energy, as in normal nuclei. The value gives new insight into the YN interaction. The excitation energies of the 1/2(-) and 3/2(-) states were obtained as 10.982 +/- 0.031(stat) +/- 0.056(syst) and 10.830 +/- 0.031(stat) +/- 0.056(syst) MeV, respectively. We also observed gamma rays from the 3/2(+) state, which has a [C-12(2(+))circle timess(Lambda)] configuration, to the ground state in C-13(Lambda). The excitation energy of the 3/2(+) state was obtained as 4.880 +/- 0.010(stat) +/-0.017(syst) MeV. Nuclear gamma rays with energies of 4.438 and 15.100 MeV had similar yields, which suggests that a quasifree knockout of a Lambda particle is dominant in highly excited regions.