Parity non-conservation effects in neutron elastic scattering reactions

Energy dependence of parity non-conservation effects is derived for neutron elastic scattering on nuclei: emission asymmetry and the rotation of the polarization plane for the polarized neutron beam and longitudinal polarization for unpolarized neutrons. Both potential scattering and scattering through the compound-nucleus resonances (multi-level approximation) are taken into account. The expressions obtained are compared with experimental data on thermal neutron scattering.     

Spin effects in proton-proton elastic scattering near the forward direction

We have analysed the several sets of experimental data on pp elastic scattering in the Coulomb interference region in the range p_lab between 9 and 500 GeV/c, in order to estimate the size of the spin dependent part of the strong amplitude. Calling β the ratio of this spin-dependent part to the spin-dependent amplitude in the forward direction, we find all the data strongly suggest but do not conclusively prove a non-negligible β whose value is around 10% and approximately constant with energy. This result cannot be explained theoretically in terms of exchange of any simple factorising Regge pole. We suggest important pomeron cut contributions. Implications of our analysis for some experiments at ISR energies which appear to give rising total cross sections are discussed.     

Parity violation in electron-deuteron scattering I. Methodology and elastic scattering

In this paper, we present methodology for investigating theoretically parity violation in both the elastic and break-up channels of electron-deuteron scattering, restricting ourselves to energies in which non-relativistic expansions are allowed for nucleons. The deficiency in the standard impulse approximation related to gauge invariance is remedied by relating it to the “elementary-particle” treatment. Results for parity violation in elastic electrondeuteron scattering are presented and discussed.     

Parity non-conservation in low energy scattering of nucleons by light nuclei: (II). Results

The analysis developed in the preceding paper is applied to the low energy scattering of longitudinally polarized nucleons by ²H, ³He and ⁴He and of deuterons by ¹H. The sensitivity of the parity non-conserving asymmetry of the total cross section to the weak interaction is probed. The asymmetry is computed for various parity non-conserving nucleon-nucleon potentials in a distorted wave approximation. The asymmetries generally are found to depend sensitively on the parameters of the potential, but are smaller than those predicted for nucleon-nucleon scattering at the same energy.     

Further results on small-angle elastic proton-proton scattering at very high energies

This work extends our previous investigations at the CERN Intersecting Storage Rings, with improved statistics at three different energies, wider angular range and a better control over systematic errors. Values for the (diffraction) shape parameter b are given.     

Parity non-conservation in low energy scattering of nucleons by light nuclei: (I). Theoretical framework

The low energy scattering of nucleons by ²H, ³He and ⁴He are analyzed for parity non-conserving effects. The asymmetry in the total cross section of longitudinally polarized projectiles is formulated in terms of the optical theorem and a distorted wave Born approximation. For two nucleons at low energies it is only necessary to consider l = 0 to l = 1 matrix elements of the weak nucleon-nucleon potential. The asymmetries in the scattering from nuclear targets are related to the parameters of an effective weak nucleon-nucleon potential, so that they may be used to help differentiate between various proposed theoretical potentials.     

The use of fixed t analyticity in elastic proton-proton scattering

Several methods of exploiting fixed-t analyticity are described and compared with each other. For the forward amplitude the predictions of the real parts from the total cross section data — including the new NAL data — and dispersion relations are found to be in good agreement with the Coulomb interference data. It is also discussed how the results depend on the assumptions on the asymptotic behaviour of the cross section. Furthermore, the conventional dispersion relation approach is compared with the method of analytic parametrization and with the differential operator method. For the non-forward directions, information on the amplitude is extracted from a dispersion relation for the slopes and from a relation between the phase and the modulus of the amplitude.     

Low-energy proton-proton scattering

The discrepancies which have been reported in experimental data for low-energy proton-proton scattering can be partly explained by various relativistic, radiative and finite proton size effects.     

Polarization in proton-proton elastic scattering at 10, 14 and 17.5 GeV/c

Data on the polarization parameter in pp elastic scattering in the |t|-range from ∼0.1 to ∼ 2.9 (GeV/c)² and at 10, 14 and 17.5 GeV/c are presented.     

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.)     

Measurements of small angle proton-proton elastic scattering at the CERN intersecting storage rings

Proton-proton elastic scattering has been measured over the angular range 7 to 16 mrad at centre-of-mass energies of 31, 45 and 53 GeV using the CERN Intersecting Storage Rings. The results indicate that the diffraction peak has continued to shrink with increasing energy, but not as fast as suggested by the results at lower energies.     

Excitation functions of the analyzing power in elastic proton-proton scattering from 0.45 to 2.5 GeV

Excitation functions A_N(p_lab,_c.m.) of the analyzing power in elastic proton-proton scattering have been measured in an internal target experiment at the Cooler Synchrotron COSY with an unpolarized proton beam and a polarized atomic hydrogen target. Data were taken continuously during the acceleration and deceleration for proton kinetic energies T_lab (momenta p_lab) between 0.45 and 2.5 GeV (1.0 and 3.3 GeV/c) and scattering angles 30 ^° _c.m. 90^°. The results provide excitation functions and angular distributions of high precision and internal consistency. The data can be used as calibration standard between 0.45 and 2.5 GeV. They have significant impact on phase shift solutions, in particular on the spin triplet phase shifts between 1.0 and 1.8 GeV.     

Parity violation in elastic electron-proton scattering and the Proton's strange magnetic form factor

We report a new measurement of the parity-violating asymmetry in elastic electron scattering from the proton at backward scattering angles. This asymmetry is sensitive to the strange magnetic form factor of the proton as well as electroweak axial radiative corrections. The new measurement of A = -4.92+/-0.61+/-0.73 ppm provides a significant constraint on these quantities. The implications for the strange magnetic form factor are discussed in the context of theoretical estimates for the axial corrections.     

Measurement of the polarization parameter in small angle proton-proton elastic scattering at 6 GeV/c

The polarization parameter in pp elastic scattering was measured at 6 GeV/c with fine t resolution for 0.02 < ?t < 0.5 GeV² using a polarized proton beam with Effective Mass Spectrometer at the Zero Gradient Synchrotron. The polarization rises like √?t in the interval 0.02 < ?t < 0.1 GeV², No statistical significant structure was found in this region of momentum transfer.     

Further measurements of parity non-conservation in inelastic electron scattering

We have extended our earlier measurements of parity violating asymmetries in the inelastic scattering of longitudinally polarized electrons from deuterium to cover the range 0.15≤y≤0.36. The observed asymmetry shows only slight y dependence over this range. Our results are consistent with the expectations of the Weinberg-Salam model for a value of sin²θ_w= 0.224±0.020.