Macroscopic parity violation and supernova asymmetries

Core collapse supernovae are dominated by weakly interacting neutrinos. This provides a unique opportunity for macroscopic parity violation. We speculate that parity violation in a strong magnetic field can lead to an asymmetry in the explosion and a recoil of the newly formed neutron star. We estimate the size of this asymmetry from neutrino polarized-neutron elastic scattering, polarized electron capture and neutrino-nucleus elastic scattering in a (partially) polarized electron gas.     

Parity-violating effects in elastic electron deuteron scattering

The general expressions for parity violation observables in elastic scattering of polarized and/or unpolarized electrons from unpolarized deuterons are given and are numerically evaluated for the kinematics of SAMPLE, PVA4 and G0 experiments. The dominant contribution from the interference of and Z exchange as well as the smaller contributions from strangeness (s components of the nucleon, parity odd admixtures in the deuteron wave function, anapole moments and radiative corrections are included and discussed in the context of parity-violating electron scattering experiments of present interest.     

Parity Violation in Proton—Deuteron Scattering

JETP Letters - Effects of parity violation in the interaction of relativistic polarized protons and deuterons are discussed. P-odd asymmetries in the total and elastic scattering cross sections, in...     

Elastic and inelastic scattering of nucleons from 16O

Measurements of differential elastic and inelastic cross sections for neutron scattering from ¹⁶O at incident energies 18 to 26 MeV are presented. In addition to cross sections for neutron scattering differential cross sections for proton scattering up to 66 MeV are described in terms of phenomenological optical model potentials. At 24.5 MeV incident energy inelastic scattering up to 11.5 MeV excitation was measured. The elastic and inelastic compound nucleus contributions were examined. Direct inelastic scattering from the normal parity states was calculated using the DWBA and coupled-channel formalisms. The inelastic scattering cross section from non-normal parity state 2⁻ was calculated using the coupled-channel formalism via multi-step processes. Cross sections due to inelastic scattering from some of the states, which are thought to be members of an excited state rotational band were calculated using both vibrational and rotational approaches and were compared.     

Fine structure discussion of parity-nonconserving neutron scattering at epithermal energies

The large magnitude and the sign correlation effect in the parity non-conserving resonant scattering of epithermal neutrons from²³²Th is discussed in terms of a non-collective 2p 1h local doorway model. General conclusions are drawn as to the probability of finding large parity violation effects in other regions of the periodic table.     

Polarised electron-hadron scattering and weak interaction theory

It is shown that the naive valence quark parton model assumptions used to calculate the parity violation in polarisede-d scattering are not needed in order to extract informations from the experimental data about the neutral current couplings. Much more general assumptions which can be justified within the QCD approach are sufficient in order to arrive at essentially the same conclusions for the neutral current coupling parameters     

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.     

Parity-Violating in <Emphasis Type="Italic">e</Emphasis><Superscript>−</Superscript><Emphasis Type="Italic">e</Emphasis><Superscript>+</Superscript> Scattering at Finite Temperature

Parity violation implies that physics laws are not invariant under spatial coordinate reversal. Electron-positron scattering is a process that displays parity violation. Using the Thermo Field Dynamics formalism this scattering at finite temperature is analyzed. The transition amplitude is calculated as a function of temperature. The parity violation at very high temperatures tend to go to zero.     

Parity violation in polarised electron deuteron scattering

Preliminary calculations show that the parity violating asymmetry in polarised electron deuteron elastic scattering can be as large as observed in the SLAC experiment even in the intermediate energy region. We propose that experiments should be done to search for these asymmetries.     

Pion electroproduction in parity violating elastic ep scattering experiment

This study has been developed for electron-proton scattering experiments when only the scattered electrons are detected. Pion electroproduction on the proton including the cascade π⁰→ 2γ decay and the QED radiative corrections to elastic ep scattering are investigated. Our results are shown in the kinematical configuration of the parity violating electron scattering experiment planned at the Mainz Microtron (MAMI). Received: 20 April 1999 / Revised version: 4 June 1999     

Electromagnetic wave scattering by an external field

The quantum electrodynamics of bilocal fields is used to calculate the triangular Feynman diagrams describing the elastic scattering of a classical electromagnetic wave by an external Coulomb field. The total contribution of the diagrams is nonzero because of the violation of both the Furry theorem (CP or T symmetries) and the Ward identities. The cross section for this scattering process is found for low and high energies. A comparison with Compton scattering and Euler—Heisenberg scattering is given.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 38–47, August 1995.     

Time-reversal invariance-like relations for spin-effects in elastic and inelastic reactions; vector-meson photoproduction versus compton scattering from nucleons

For elastic scattering, relations between spin-effects (for example, the well-known asymmetry-polarization equality) follow from time-reversal invariance. We show that if certain amplitude combinations vanish, there are strikingly similar relations between spin-effects for elastic and also inelastic reactions. This vanishing of amplitude combinations (denoted M-purity) corresponds asymptotically to purely natural or purely unnatural parity in the crossed channel. The M-purity relations hold for spin-configurations much more general than do the corresponding time-reversal invariance relations.The experimental evidence for purely natural parity exchanges in high energy vector meson photoproduction from nucleons is shown to be good for all amplitudes involving nonzero meson helicity, but less conclusive for the zero helicity ones. Using time-reversal invariance and a vector meson-dominance argument, this implies no unnatural parity contributions in high energy Compton scattering from nucleons.Because of this empirical evidence for M-purity in these two processes, a detailed application to spin-effects in Compton scattering and in vector meson photoproduction is made. Some time-reversal invariance relations in Compton scattering resemble the corresponding M-purity relations though the applicability of the two is different, and there are examples where only one of the two exists. Out of our illustrations, the only M-purity relations which change in form due to the extra amplitudes present in the inelastic reaction are the M-purity analogue and extensions of the asymmetry-polarization equality (of Compton scattering) referring to the photon; the change is the appearance of the elements ?⁰⁰ of the vector meson density-matrix ?. Our other examples of M-purity relations do not change in form in going over from the elastic reaction (Compton scattering) to the inelastic reaction (vector meson photoproduction).     

Elastic and inelastic scattering of 178 MeV protons from 58Ni and 60Ni

The elastic and inelastic scattering of 178 MeV protons from ⁵⁸Ni and ⁶⁰Ni has been studied. Angular distributions were measured for the differential cross sections for elastic scattering as well as inelastic scattering from excited states below about 5 MeV, all with natural parity. For the elastic and for the inelastic scattering from the first excited state (2⁺ in both nuclei, the angular distributions for the polarization were also measured. The measurements extend out to c.m. angles of about 60°, corresponding to a momentum transfer of about 600 MeV/c.The elastic and inelastic scattering data were compared to the results of coupled-channel calculations in the vibrational model using a deformed spin-orbit interaction of the full Thomas form. Good agreement was found in general showing that the main features of the experimental results are well described in this model.     

Parity-violating electron scattering at the MAMI facility in Mainz

We report here on a new measurement of the parity-violating (PV) asymmetry in the scattering of polarized electrons on unpolarized protons performed at the MAMI accelerator facility in Mainz. This experiment is the first to use counting techniques in a parity violation experiment. The kinematics of the experiment is complementary to the earlier measurements of the SAMPLE Collaboration at the MIT-Bates accelerator and the HAPPEX Collaboration at Jefferson Lab. After discussing the experimental context of the experiments, the setup at MAMI and preliminary results are presented.Received: 1 November 2002, Published online: 15 July 2003PACS: 12.15.-y Electroweak interactions - 25.30.Bf Elastic electron scatteringF.E. Maas: For the A4 Collaboration     

An intuitive approach to a generalized parton picture for high-energy lepton-hadron scattering

A generalized parton picture is developed, based on the impulse approximation. A parton is allowed to have non-point-like elastic form factors; inelastic current-parton scattering is taken into account explicitly. The amplitude of any exclusive channel of lepton-induced reactions is written down, with the parts containing the long-distance and the short-distance behavior of interaction dynamics clearly separated. Scaling violation is a natural feature of this picture. The inelastic structure functions, W₁ and νW₂, are studied in this scheme using various different theories; perturbative QCD, the scale-invariant parton model, the hadron bootstrap picture, and a phenomenological stripped-down hadron-parton model. The application of this picture to elastic lepton-hadron scattering and the problem of the selection of an infinite momentum frame are also discussed.     

Weak interactions in polarized electron-nucleus scattering

Scattering of longitudinally polarized electrons from nuclei is analysed in view of information on weak interactions. Emphasis is given to the competition of contributions due to Z-boson and photon exchange. In some kinematical domains parity mixing of nuclear states and similar processes become predominant. The asymmetry of elastic deuteron scattering is well suited for studying the polar isoscalar current, even independently of the nuclear structure. At deuteron disintegration in principle all parts of the neutral weak currents may be observed. Both cases allow for clean tests of weak interaction theories.     

Neutron scattering from Au,Hg, and Tl

The elastic and the inelastic scattering of fast neutrons from Au, Hg, and Tl was studied at incident neutron energy intervals of ~50 keV from 0.3 to 1.5 MeV. The differential elastic scattering cross sections were determined approximately every fifteen degrees from 20 to 145 degrees. The cross sections for the inelastic excitation of states in Au at 77, 270, 409, 520, 540, 740, 830, 940, 1120, and 1220 keV; in Hg at 160, 208, 440, 610, 980, and 1120 keV; and in Tl at 205, 279, 615, 680, 930, and 1080 keV were determined. The measured elastic scattering cross sections were compared with the results of optical model calculations and evidence for a decrease in the imaginary part of the potential near the doubly closed shell atA=208 was observed. The results of Hauser-Feshbach calculations, utilizing known spin and parity assignments together with those estimated from nuclear systematics, were in qualitative agreement with the measured inelastic excitation functions. The effect of resonance width fluctuations was considered in the context of the experimental results.     

Parity violation in electron-deuteron scattering. II. Break-up channels

Parity violation in electron-deuteron inelastic scattering is decribed. An impulse approximation, modified to incorporate gauge invariance, is employed. Additional meson-exchange currents are included. Normal-parity and abnormal-parity wave function components are generated numerically with a Reid soft-core potential for the former and a general parity-violating weak potential with adjustable coupling constants for the latter. Numerical results for parity-conserving differential cross sections are in good agreement with existing data. For low n?p excitation energies and medium-energy electrons, we find that parity-violating asymmetries are dominated by contributions from neutral weak currents so that the Weinberg-Salam theory can be tested. For low-energy electrons, 5 MeV ? E_e ? 50 MeV, our results indicate that the asymmetry caused by nuclear parity violation is roughly as important as that due to neutral weak currents. The pion-nucleon parity-violating coupling, f_π, as well as the rho- and omega-nucleon parity-violating couplings, may be determinable from such experiments. Further, it is possible to check the experiment of Lobashov et al., which detects circular polarization in the thermal-neutron capture reaction.     

Low-lying excitations in the odd-odd nucleus154Eu

The analysis of experiments on parity mixing in compound nuclear resonances is described, with the nuclear spectroscopic aspects of the parity violation experiments emphasized. Expressions are derived for polarized neutron scattering and polarized neutron capture on unpolarized targets, and the resonance interference is treated explicitly. Examples are presented to illustrate the effects of entrance channel mixing for the case of target spin 1/2 and resonance spin 1. Results are also presented for targets with spins 0 and 3/2.