Parity-violating interaction effects in the np system
- Jefferson Lab, Newport News, Virginia 23606, USA and Department of Physics, Old Dominion University, Norfolk, Virginia 23529 (United States)
We investigate parity-violating observables in the np system, including the longitudinal asymmetry and neutron-spin rotation in n-vectorp elastic scattering, the photon asymmetry in n-vectorp radiative capture, and the asymmetries in deuteron photodisintegration d({gamma}-vector,n)p in the threshold region and electrodisintegration d(e-vector,e{sup '})np in quasielastic kinematics. To have an estimate of the model dependence for the various predictions, a number of different, latest-generation strong-interaction potentials - Argonne v{sub 18}, Bonn 2000, and Nijmegen I - are used in combination with a weak-interaction potential consisting of {pi}-, {rho}-, and {omega}-meson exchanges - the Desplanques-Donoghue-Holstein (DDH) model. The complete bound and scattering problems in the presence of parity-conserving, including electromagnetic, and parity-violating potentials are solved in both configuration and momentum space. The issue of electromagnetic current conservation is examined carefully. We find large cancellations between the asymmetries induced by the parity-violating interactions and those arising from the associated pion-exchange currents. In the n-vectorp capture, the model dependence is nevertheless quite small, because of constraints arising through the Siegert evaluation of the relevant E{sub 1} matrix elements. In quasielastic electron scattering these processes are found to be insignificant compared to the asymmetry produced by {gamma}-Z interference on individual nucleons. These two experiments, then, provide clean probes of different aspects of weak-interaction physics associated with parity violation in the np system. Finally, we find that the neutron-spin rotation in n-vectorp elastic scattering and asymmetry in deuteron disintegration by circularly polarized photons exhibit significant sensitivity both to the values used for the weak vector-meson couplings in the DDH model and to the input strong-interaction potential adopted in the calculation. This reinforces the conclusion that these short-ranged meson couplings are not in themselves physical observables; rather, the parity-violating mixings are the physically relevant parameters.
- OSTI ID:
- 20695639
- Journal Information:
- Physical Review. C, Nuclear Physics, Vol. 70, Issue 4; Other Information: DOI: 10.1103/PhysRevC.70.044007; (c) 2004 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 0556-2813
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ASYMMETRY
BOSON-EXCHANGE MODELS
DEUTERONS
ELASTIC SCATTERING
ELECTRON-NEUTRON INTERACTIONS
ELECTRON-PROTON INTERACTIONS
ELECTRONS
MATRIX ELEMENTS
NEUTRONS
NUCLEAR FORCES
OMEGA-782 MESONS
P INVARIANCE
PARITY
PHOTONS
PHOTONUCLEAR REACTIONS
PIONS
POLARIZATION
POTENTIALS
PROTON-NEUTRON INTERACTIONS
QUASI-ELASTIC SCATTERING
RHO-770 MESONS
SPIN
STRONG INTERACTIONS
WEAK INTERACTIONS