Search

The polarization transfer κ0 and the tensor analyzing power T20 for the 1 H d p)d reaction have been measured up to an internal momentum of k = 0.58 GeV/c. Comparison of the same observables obtained in recent studies for 1 H d p)d reaction, as a function of k, show different behavior. However the data from these two reactions are almost identical when compared in T20 versus κ0 correlation plots. We discuss similarities and differences observed in the two reactions.

The polarization of the proton from the inclusive breakup reaction 1 H( d , p )X at 2.1 GeV was measured at 0°. The results are expressed as the ratio of the proton polarization, P p , to the deuteron beam polarization, P d , κ 0 = P p / P d . The measured values of κ 0 range from +0.983 to -0.305 and are in general agreement with the expected behavior arising from the D state in the deuteron wave function.

We have searched for an enhancement in the ratio of yields of 40 MeV π ± to 100 MeV π ± in he reaction Cu(p, π ± )X. For bombarding energies of 346–358 MeV, for resonances of widths of 2–8 MeV, we set upper limits of 2.7% enhancement for π + , and 9.1% for π − .

An intermediate energy proton scattering experiment has been performed to probe spin excitation in the deformed rare earth nuclei 154 Sm, 158 Gd and 168 Er for energies up to 12 MeV. A concentration of spin M1 strength is observed between 6 and 10MeV with a total strength of about 11 μ N 2 independent of the nucleus. The strength function shows two distinct structures separated by about 2.5 MeV and each having a width of about 2 MeV.

Measurements of the spin-flip probability S nn for inclusive inelastic proton scattering around 300 MeV from nuclei between 12 C and 90 Zr show that an enhanced spin response near 40 MeV excitation at q ∼ 100 MeV/ c is a general feature of nuclear structure. Data for 40 Ca at 800 MeV confirm that the enhancement is not a peculiarity of 300 MeV scattering. In addition, measurements in 44 Ca up to 75 MeV show that the enhancement cannot be attributed solely to a relatively narrow resonance. Continuum RPA calculations suggest that the enhancement is due to the exhaustion of most S = 0 strength at lower energy and a shift of S = 1 strength to higher energy.

The 90 Zr(n,p) 90 Y reaction has been studied at a bombarding energy of 198 MeV in a search of GT + strength. Up to 10 MeV excitation in 90 Y, we obtain a firm upper limit of S β + ⩽ 3.6. The majority of the strength at low excitations is identified as spin dipole.

High momentum transfer measurements from TRIUMF are presented for proton elastic scattering from 40Ca, 90Zr and 208Pb. Differential cross sections and analyzing powers are given for proton kinetic energies of 200, 362 and 400 MeV out to a maximum momentum transfer of q≈4.8 fm−. The data are analyzed with a non-relativistic microscopic optical model to investigate its limits and to compare it with recent relativistic models.

The cross section at 0° for the reaction 14 C(p, n) 14 N has been measured at energies of 200, 300, 400 and 450 MeV using a nucleon charge-exchange facility recently commissioned at TRIUMF. Energy resolution of 1 MeV or better was obtained at each energy, permitting a reliable measurement of the cross section ratio for the Gamow-Teller transition to the 1 + state at 3.95 MeV and the Fermi transition to the 0 + state at 2.31 MeV. The deried values of ‖ J στ / J τ ‖ 2 are in clear disagreement with impulse approximation calculations using a free NN t -matrix.

The208Pb(n, p)208Tl reaction was studied at 198 and 458 MeV in a search for isovector spin giant resonances. Peaks at 5.1 MeV and 13.6 MeV excitation in208Tl are observed and discussed as candidates for the T> spin giant dipole resonance (SGDR), the spin isovector monopole resonance (SIVM), and the spin isovector quadrupole resonance (SIVQ).

Differences of the polarization ( P ) and analyzing power ( A y ) have been measured between 5° and 14° for the lowest isoscalar 1 + and isovector 1 + and 2 + states in 12 C excited by 400 MeV protons. This is the first measurement of P - A y in an energy regime where the impulse approximation is most valid. Values of P - A y for all states are compared to both nonrelativistic and relativistic model calculations, which only qualitatively describe the data.

A newly constructed focal-plane polarimeter for the medium resolution spectrometer at TRIUMF has been used to measure polarizations and polarization transfer coefficients for protons elastically scattered from 208Pb at 290 MeV. These results combined with existing cross section data at 300 MeV completely determine the elastic scattering amplitudes for momentum transfers q

Energy distributions of A y at backward angles are found to be identical for inclusive proton scattering from Be and C at 303 MeV. While the cross sections scale in the y -variable of West in the same way as electron and pion scattering, the A y values are on the average small and energy dependent, at variance with those expected for a single scattering mechanism.

We have measured the cross sections for the radiative capture reacrtion pd → 3 He γ at a range of proton energies from 200 to 500 MeV. The results are presented in the form of excitation functions at center-of-mass angles 60° and 90°. These results are compared with other radiative capture cross sections and with equivalent photodisintegration experiments using detailed balance.

For the 24 Mg ( →p . →p ′) reaction at Ep=250 MeV and small momentum transfers we have measured cross sections, analysing powers and spin-transfer probabilities up to 40 MeV of excitation in 24Mg. Because of the strong suppression of the S=0 excitations in the spin-flip cross sections, the analogs of Gamow-Teller transitions could be cleanly observed. Up to Eexc=15 MeV about 80% of the L=0 strength predicted by large-scale shell model calculations has been found.

Differential cross sections and analyzing powers for elastic scattering of 200 MeV protons from 208 Pb are reported. The measurements range from 43° to 90° where differences between the microscopic relativistic impulse approximation (MRIA) and microscopic Schrodinger calculations (MSC) for the analyzing power were predicted to be large. Results agree surprisingly well with the MSC and reveal, for the first time, a serious deficiency in the MRIA. This suggests that exchange and medium effects, both of which are included in the MSC, may be important at large angles. In fact, inclusion of these effects in a new relativistic calculation shows a much smaller difference between the Dirac and Schrodinger approaches.

The ground state differential cross sections for the (n, p) reaction at 0° on 6Li, 12C and 13C have been measured for 198 MeV neutrons with a precision of about 4% relative to the corresponding value for the H(n, p) reaction. These data, together with the accurately known ft values for the β- decay of 6He, 12B and 13B provide three calibrations of the (n, p) reaction as a probe of Gamow-Teller strength for isospin raising transitions.

The 3He(p,2p)d reaction has been measured at 300 MeV at the angle pair 70°-33° and at 450 MeV at the angle pairs 70°-30° and 46°-46° for recoil momenta larger than 350 MeV/c. For the 3He(p,pd)p reaction energy sharing loci have been measured at 450 MeV for the angle pairs 25°–68°, and 50°–68°, yielding a recoil momentum range from 0 to 480 MeV/c. The proton-deutern relative motion momentum distributions were deduced in the framework of the PWIA and are compared to existing 3He(e,e′o)d results and to the momentum distribution calculated from the ovelap integral between a Hulthen deuteron wave function and an Irving-Gunn 3He wave function. Comparisons are also made with spectral function ccalculated using the Faddeev equations and variational techniques.

Intermediate energy proton scattering has been used to probe the spin part of the recently discovered low-lying isovector magnetic dipole transitions in the rotational rare earth nuclei 156 Gd and 164 Dy. A large spin response is found in 164 Dy, whereas in 156 Gd the results are consistent with the picture of a predominantly convective excitation. The results are discussed in the context of the IBA-2 model and recent RPA calculations.

Angular distributions of the cross section at 470 and 500 MeV and the analyzing power at 500 MeV incident proton energy are presented for the reaction 2 H ( p ,π + ) 3 H . The cross section and analyzing power measurements cover the respective angular ranges 10°

Analyzing powers and cross sections for the reaction p d → ttπ + have been measured at large pion center-of-mass angles at 425, 450, 475 and 500 MeV incident proton energies. The cross section and analzing power angular distributions cover the range 110° ⩽ θCM(π+) ⩽ 160°. The results are compared with theoretical calculations which include one- and two-nucleon exchange and meson exchange involving two or three nucleon vertices.

Using a polarized neutron beam and liquid hydrogen target, we have measured the analyzing power for the reaction np → d γ at neutron beam energies of 180 and 270 MeV. Our results are compared with recent calculations.

The analyzing power angular distributions have been measured for the p d → tπ + reaction at 900, 1000 and 1100 MeV. At backward angles the analyzing power varies rapidly with energy, an effect which can be traced back to a simple variation of the amplitudes with energy.