Y. Takeuchi

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.

Inelastic proton scattering exciting the γ-vibrational band in 168Er and the necessity of the hexadecapole degree of freedom in the γ-motion

Abstract Inelastic scattering exciting the 2 2 + and 4 2 + members of the γ -vibrational band in 168 Er has been investigated with 65 MeV polarized protons. A coupled-channel analysis has been performed assuming both the γ -vibrational model and the asymmetric-rotor model. A large hexadecapole term ( Y 42 + Y 4−2 ) in the γ -motion is necessary in order to reproduce the experimental data.

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.

Observation of the decay mode KL→π+π−e+e−

Abstract We report on results of an experimental search for the K L → π + π − e + e − decay mode. We found 13.5±4.0 events and determined its branching ratio to be (4.4±1.3(stat.)±0.5(syst.))×10 −7 . The result agrees well with the theoretical prediction.

A neutron polarimeter for the (p,n) reaction at Ep=50–80 MeV

A conventional type of neutron polarimeter consisting of three 12.5 × 12.5 cm cylindrical liquid scintillators and two 12.5 × 12.5 cm cylindrical plastic scintillators has been used to measure the transverse polarization transfer coefficient Kyy in the (p, n) reaction in the energy range 50 < Ep < 80 MeV. The effective analyzing powers of this polarimeter have been obtained empirically by observing neutrons from the 6Li(p, n)6Be reaction at θ = 0° and Ep = 50,65 and 80 MeV whose polarizations are deduced from the Kyy values of the 6Li(p,p′)6Be∗ (0+ reaction by utilizing the analogue relation. Observed effective analyzing powers are significantly reduced particularly at high energy, most likely due to the 12C(n,np)11B reaction process. The double scattering efficiencies are 6 × 10−4 and 3 × 10−4 with effective analyzing powers of 0.14 and 0.11 at En = 45 and 75 MeV, respectively.

Polarization transfer measurements for the (d, pX) reaction at Ed = 65 MeV and the reaction mechanism for the protons in the continuum

Abstract The double-differential cross section d 2 σ/dΩ d E , analyzing power A γ , polarization P y and polarization transfer coefficient K y y were measured for the ( d , p X ) reaction with 65 MeV deuterons for 12 C at 14.0° and for 58 Ni at 7.0°, 14.0°, 20.5° and 40.0°. The experimental data were analyzed within the framework of the post-form DWBA appropriate for the “spectator breakup”, and the preequilibrium exciton model together with the evaporation mode. The experimental angular distributions are well explained by taking account for these processes over the whole proton energy region observed.

Measurement of the depolarization parameter Kyy′ in p2H elastic scattering at Ep = 65 MeV

Abstract The depolarization parameter K y y ′ in the elastic scattering of 65 MeV polarized protons from deuterium has been measured using a newly designed spectrograph and a multi-foil polarimeter. The measured K y y ′ values are well reproduced by a Faddeev calculation using the Nue5f8N interaction in a separable representation with a tensor force which reproduces the empirical mixing parameter of the 3 S 1 ue5f8 3 D 1 partial waves.

Experimental search for the decay mode KL→π0γe+e−

Abstract We report on results of a search for the decay mode K L → π 0 γe + e − conducted by the E162 experiment at KEK. We observed no events and set a 90% confidence level upper limit of Br ( K L → π 0 γe + e − ) −7 for its branching ratio. This is the first published experimental result on this decay mode.

A useful method to monitor outputs from a pulsed light source and its application to rate effect studies in a photomultiplier tube

Abstract In order to study short-term gain stability in a photomultiplier tube at high counting rate, we constructed an LED pulsed light source and its output monitoring system. For the monitoring system, we employed a photon counting method using a photomultiplier as a monitor photon detector. It is found that the method offers a simple way to monitor outputs from a pulsed light source and that, together with an LED light source, it provides a useful method to investigate photomultipliers rate effects.