Microscopic calculation of the spin-dependent neutron scattering lengths on 3He

We report on the spin.dependent neutron scattering length on 3He from a microscopic calculation of p-3H, n-3He, and d-2H scattering employing the Argonne v18 nucleon-nucleon potential with and without additional three-nucleon force. The results and that of a comprehensive R-matrix analysis are compared to a recent measurement. The overall agreement for the scattering lengths is quite good. The imaginary parts of the scattering lengths are very sensitive to the inclusion of three-nucleon forces, whereas the real parts are almost insensitive.Comment: 9 pages, 1 figur

Theory of parity violation in compound nuclear states; one particle aspects

In this work we formulate the reaction theory of parity violation in compound nuclear states using Feshbach's projection operator formalism. We derive in this framework a complete set of terms that contribute to the longitudinal asymmetry measured in experiments with polarized epithermal neutrons. We also discuss the parity violating spreading width resulting from this formalism. We then use the above formalism to derive expressions which hold in the case when the doorway state approximation is introduced. In applying the theory we limit ourselves in this work to the case when the parity violating potential and the strong interaction are one-body. In this approximation, using as the doorway the giant spin-dipole resonance and employing well known optical potentials and a time-reversal even, parity odd one-body interaction we calculate or estimate the terms we derived. In our calculations we explicitly orthogonalize the continuum and bound wave functions. We find the effects of orthogonalization to be very important. Our conclusion is that the present one-body theory cannot explain the average longitudinal asymmetry found in the recent polarized neutron experiments. We also confirm the discrepancy, first pointed out by Auerbach and Bowman, that emerges, between the calculated average asymmetry and the parity violating spreading width, when distant doorways are used in the theory.Comment: 37 pages, REVTEX, 5 figures not included (Postscript, available from the authors