H. Togawa

(K−, K+) reaction on nuclear targets at PK = 1.65 G

Abstract The forward-angle cross sections of the (K − , K + ) reaction on nuclear targets of C, Al, Cu, Ag and Pb have been measured at the K − incident momentum of 1.65 GeV/ c in a side range K + momentum. The obtained K + momentum spectrum for each target nucleus is characterized by a peak in the high-momentum region ( p K + > 0.95 GeV/ c ) and a broad bump in the low-momentum region ( p K + c ). A comparison of the measured spectrum with a DWIA calculation indicates that the quasifree process, K − (p) → K + Ξ − , is dominant in the high-momentum region. The target mass-number dependence of the cross section is well fitted with A α , where α is 0.38 ± 0.03 for the high-momentum region and 0.56 ± 0.02 for the low-momentum region. The result indicates that the quasifree process takes place at the peripheral of the target nucleus, whereas the two-step processes are dominant in the low-momentum region.

Production of a twin single hypernuclei and the Ξ−-nuclear interaction

Abstract An event accompanied by two single hyperfragments emitted from a Ξ− nuclear capture at rest was found in a nuclear emulsion. It is interpreted as a Ξ−-12C bound system decaying into either a) Λ4H + Λ9Be, b) Λ 4 H + Λ 9 Be ∗ or c) Λ 4 H ∗ + Λ 9 Be . The binding energy of the Ξ-12C system is obtained as a) 3.70−0.19+0.18 MeV, b) 0.62−0.19+0.18 MeV and c) 2.66−0.19+0.18 MeV, respectively. The system is considered as a Ξ− hypernucleus in the cases a) and c). In case b), this event and another event of the same type (Yokohama event) can both be interpreted as a decay from the Ξ-12C system in 2P state when a shallow Ξ−-nuclear potential is assumed.

Mass number dependence of hexadecapole (Y42) excitation of the γ-vibrational band in proton inelastic scattering for 152⩽A⩽192

Abstract Inelastic scattering exciting the 2+ and 4+ members of the Kπ=2+ γ-vibrational band in 152, 154Sm, 160Gd, 164Dy, 166, 168Er, 176Yb, 182, 184W and 192Os has been measured with 65 MeV polarized protons. The quadrupole (Y22) and hexadecapole (Y42) transition strengths to the γ-vibrational band have been extracted systematically for the first time. They show strong mass number dependences, which are explained qualitatively by a simple geometrical picture.

A multifoil carbon polarimeter for protons between 20 and 84 MeV

A new type of polarimeter has been built for protons between 20 and 84 MeV. It is a ray trace type with a multifoil of carbon, multiwire proportional chambers and plastic scintillators. The polarimeter distinguishes between elastic and inelastic scattering from carbon foil and has a large solid angle acceptance (∼ 470 msr) from the carbon foil. The effective analyzing power and the effective efficiency for practical use are estimated at 0.84 and 1.7 × 10−4 in the vicinity of 60 MeV, respectively. To evaluate these values, cross sections and analyzing powers for p—C elastic scattering have been measured for laboratory scattering angles between 15° and 80° at 19 energies from 21.1 to 83.8 MeV.

Depolarization in p-15N elastic scattering and large tensor spin-spin interaction

Abstract We have measured the angular distribution of the depolarization parameter Kyy′ in p-15N elastic scattering at 65 MeV. The deviation of Kyy′ from unity is large and indicates the existence of a nucleon-nucleus spin-spin interaction. The DWBA analysis shows that the measured Kyy′ data imply a large contribution from the tensor part of the spin-spin potential.