Small-angle proton - proton scattering cross-sections at 144 MeV

The differential cross-section in proton-proton scattering at 144 ± 1.5 MeV has been measured over the Coulomb-nuclear interference region. When the present data are included in a phase-shift analysis the resultant phas-shifts are only slightly changed from their previous values.     

Inelastic proton scattering from Ba and Sm at 30 MeV

Measurements of the inelastic scattering of 30 MeV protons from ¹³⁸Ba and ¹⁴⁴Sm have been carried out with 7–10 keV energy resolution. Differential cross sections were measured for levels up through 3.4 MeV excitation energy. For most of these states J^π assignments are suggested on the basis of angular distributions distinctly characteristic of angular momentum transfer L = 2, 3, 4,or 6.     

Cross-sections and spin observables in proton-proton elastic scattering: Results from EDDA at COSY

At the Cooler-Synchrotron COSY/Jülich polarized and unpolarized elastic proton-proton scattering has been investigated with the EDDA-Experiment in the energy range ( -2.5 GeV). By taking scattering data during the acceleration of the beam with a large-acceptance ( - ) detector, precise excitation functions for differential cross-section and analyzing power have been measured in small energy steps with consistent normalization with respect to luminosity and polarization. These data have helped to improve the determination of phase-shifts at higher energies and impose tight quantitative upper bounds on possible resonant contributions to pp elastic scattering, as they might arise from exotic 6-quark configurations. Recently, with polarized beam and target, the spin-correlation parameters , , and have been determined at 10 energies between 0.8 and 2.5 GeV. The observable has been measured the first time above 800 MeV and our results are in sharp contrast to phase-shift predictions at higher energies.Received: 30 September 2002, Published online: 22 October 2003PACS: 24.70. + s Polarization phenomena in reactions - 25.40.Cm Elastic proton scattering - 11.80.Et Partial-wave analysis - 13.75.Cs Nucleon-nucleon interactions (including antinucleons, deuterons, etc.)     

Polarized proton inelastic scattering from 40Ca and 48Ca at 500 MeV

Differential cross sections and analyzing powers for inelastic scattering of 500 MeV polarized protons to several low-lying states in ⁴⁰Ca and ⁴⁸Ca are presented. Phenomenological optical potentials (including density squared terms) have been determined and the data have been analyzed to obtain mass deformation parameters. It is expected that these data will be useful in further testing the recently developed relativistic impulse approximation formalisms and in studying the need for medium modification of the interaction.     

Measurement of spin observables in neutron-proton elastic scattering

The spin correlation parameters and the analyzing power have been measured in free np elastic scattering at kinetic energies of 260, 315, 380, 460 and 535 MeV in the c.m. angle range from 60° to 164°. The experiment was performed at the Paul-Scherrer-Institut (PSI) using a polarized neutron beam with continuous energy incident on a polarized proton target. These data will contribute significantly to the determination of the isospin I=0 nucleon-nucleon amplitudes. Received: 24 May 2000 / Published online: 31 August 2000     

A complete measurement of spin-observables for intermediate-energy inclusive quasielastic polarized proton scattering from C

The complete set of Wolfenstein parameters, the polarization, the asymmetry of scattering and the unpolarized double-differential cross section are presented for inclusive quasielastic proton scattering from ¹²C at a central momentum transfer of q = 1.9 fm⁻¹ and incident energies of 290 and 420 MeV. The spin observables D₀, D_x, D_y and D_z as well as the longitudinal-to-transverse ratio of spin-flip probabilities are extracted from the data. Across the quasielastic continuum, the experimental data is compared to the variations expected from a single-scattering Fermi-gas approximation using the free NN amplitudes. Medium effects are evident in the pronounced quenching of the polarization parameter relative to the free value.     

Analysis of 185 MeV proton scattering from6Li

The internal bremsstrahlung ofα-particles emmited byα-decaying nuclei is not responsible for the internal pair production inα-decay. The probability of this process is of the order of 10^?20, in strong disagreement with previous resuls. It is suggested that the internal pair production inα-decay is due to excited states in nuclei. For the probability of this process a value of the order of 10^?12 has been obtained.     

Transverse beam spin asymmetries at backward angles in elastic electron-proton and quasielastic electron-deuteron scattering

We have measured the beam-normal single-spin asymmetries in elastic scattering of transversely polarized electrons from the proton, and performed the first measurement in quasielastic scattering on the deuteron, at backward angles (lab scattering angle of 108°) for Q2 = 0.22 GeV2/c2 and 0.63 GeV2/c2 at beam energies of 362 and 687 MeV, respectively. The asymmetry arises due to the imaginary part of the interference of the two-photon exchange amplitude with that of single-photon exchange. Results for the proton are consistent with a model calculation which includes inelastic intermediate hadronic (πN) states. An estimate of the beam-normal single-spin asymmetry for the scattering from the neutron is made using a quasistatic deuterium approximation, and is also in agreement with theory.     

GoldL-shell ionization probability by 1 MeV proton at large scattering angles

The impact parameter dependence of the ionization of GoldL-subshells has been measured and compared to theoretical values calculated in the SCA framework by Aashamar et al. [17]. Special attention has been paid to large scattering angle measurements and results are obtained for0 _lab=30°, 45°, 65°, 90°, 110°, 130°, 153° and 166°. Taking into account the sum ofL _α ,L _β ,L _γ ,L _α ,L _l lines we conclude firstly that the experimental ionization probabilityP(b) is in good agreement with the theoretical values. Secondly, comparing experimental and theoretical intensity of (L _α +L _l ) and (L _γ +L _β ) X-ray lines, we show that ionization ofL _II andL _III subshells is also fairly well described by the SCA model.     

Photonuclear reaction yields from59Co at 35 MeV and 54 MeV

In energy loss measurements with 50 keV electrons the damping of the 15 eV volume plasma loss in Al was investigated by means of its energy half widthΔ E as function of the scattering angle?. For angles smaller than 1.5 · 10^?3 rad a damping is observed, which cannot be explained by former theories. It comes into play when the wavelength of the plasmons is larger than the mean crystal sized. — For large crystal size (d ≧250 Å) the half width of the plasma loss obtained at ?=0 was 0.53 eV.     

Dilepton and double-photon production in proton—Proton scattering at 190 MeV

The first high-statistics measurement of dilepton and double-photon yields in proton—proton scattering below the pion threshold has been performed. The data obtained allow a detailed study of off-shell effects in the proton—proton interaction.     

Proton polarization observables for the elastic and inelastic scattering of 500 MeV protons from Ca and Pb

Measurements for the elastic and inelastic scattering of 500 MeV protons from ⁴⁰Ca and ²⁰⁸Pb at small momentum transfers are reported. The induced proton polarization P and the spin rotation parameter Q were measured for the elastic scattering. The spin rotation parameters D_SS′, D_SL′, D_LL′, d_LS′ and the induced polarization P were measured for transitions to the 3⁻(3.37 MeV) and 5⁻(4.48 MeV) states in ⁴⁰Ca and the 3⁻(2.61 MeV) state in ²⁰⁸Pb. Comparisons of the data with the theoretical calculations were carried out in the framework of nonrelativistic and relativistic approaches. We extracted the spin-up and spin-down channels for the elastic scattering cross sections and found that predictions of the relativistic and nonrelativistic approaches agree well with the spin-up channel data and differ considerably in the spin-down channel.     

Elastic proton scattering from He in the forward direction at 200, 350 and 500 MeV

The differential cross section for the elastic scattering of protons from ⁴He has been measured at 200, 350, and 500 MeV over an angular range from 3.5° to 15° in the lab system. In addition, the analyzing power was measured in the same angular range at 350 and 500 MeV. The experiment makes use of a tenuous gas target in which the recoil -energy is measured with solid-state detectors. The proton scattering angle is measured outside the target by a system of multi-wire proportional counters. The differential cross sections have a nearly exponential dependence on momentum transfer in this kinematic range and grow with increasing energy. The analyzing power shows strong positive asymmetry.     

Optical-model analysis of elastic scattering of 53.4 MeV helions from Fe

Elastic helion scattering from ⁵⁶Fe at 53.4 MeV was measured over the angular range 12° to 150°. Using the regular optical model, real-potential ambiguities, the shape of the imaginary term and the need for a spin-orbit term were explored. Coupled-channels (SCA) calculations based on the ground state and principal 2⁺ and 3⁻ states indicate that such coupling effects are not as dominant as the inclusion of a spin-orbit potential in the regular optical model. Previously reported helion scattering from ⁵⁹Co and ⁶⁰Ni at 50.1 MeV has been included in an average parameter analysis to generalise the improvements in the helion optical-model parameterization in this energy region.     

Measurement of proton proton elastic scattering in pure initial spin states at 11.75 GeV/c

The elastic cross section for proton proton scattering at 11.75 GeV/c was measured at the Argonne ZGS using a 50% polarized target. In the range p_⊥²=0.6 → 2.2 (GeV/c)² we obtained precise measurements of $\text{d}\text{σ}\text{d}\text{t(ij)}$ for the ? ?, and ? initial spin states perpendicular to the scattering plane. We confirmed that the asymmetry parameter, A, decreases with energy in the diffraction peak, but is approximately energy-independent at large p_⊥². We found that the spin correlation parameter c_nn acquires rather dramatic structure, and at large p_⊥² seems to grow with energy.     

Spin observables in small-angle elastic → d scattering with an L-type deuteron target at 800 MeV

We have measured spin correlation parameters that describe the elastic scattering of 800 MeV polarized protons from an L-type polarized deuteron target at laboratory angles below 20°. The measured parameters include the correlated analyzing powers A_SL, A_LL and A_NLL and the proton spin-transfer coefficients C_0L,S, C_0L,L, C_SL,N, C_NL,S, C_NL,L and C_LL,N. The results are compared with single-scattering predictions based on different phase-shift solutions for the nucleon-nucleon scattering matrix.