Parity violation scattering

Parity violating electron scattering. Recently it has been proposed to use the (parity violating) weak interaction to probe the neutron distribution. This is probably the least model dependent approach [31]. The weak potential between electron and a nucleus... 

The potentials (94) and (95) are already quite similar to the leading effective Hamiltonians that have been used so far in one- and four-component calculations of molecular parity violating eflFects. We have assumed above that the fermions are elementary particles. The effective potentials may, however, also be applied for the description of low energy weak neutral scattering events, in which heavy non-elementary fermions like the proton and the neutron or even entire atomic nuclei are involved, provided that properly adjusted vector and axial coupling coefficients py and for non-elementary fermions are used. 

Compared to the electron-nucleus contribution, the parity violating effects due to electron-electron scattering with Z° exchange are in general assumed to be of minor importance and have so far been neglected in all... 

C. Chardonnet, C. Daussy, T. Marrel, A. Amy-Klein, C. Nguyen, C. Borde, Parity violation test in chiral molecules by laser spectroscopy, in B. Frois, M. Bouchiat (Eds.), Parity violation in atoms and polarized electron scattering. World Scientific, Singapore, 1999, pp. 325-355. 

Again, in an effort to be forward looking, experiments on parity-violating electron scattering on Pb (a project called PREX) will be done in the next few years. If snccessful, this experiment will produce data directly sensitive to the linear term in the dependence of the asymmetry energy on density (Horowitz and Piekarewicz 2002). 

The predicted neutral current weak interaction was initially seen in neutrino-nucleon scattering in 1973. There remained the question of the validity of the theory as regards parity violation in the electron-nucleon interaction. This question has been largely answered in high-energy electronscattering experiments and in the atomic parity violation experiments, the subject of this review. 

P4 is again a Stokes parameter for unpolarised electrons. P5 and Pe must be zero if Px = 0. This can be seen by taking a mirror reflection in the scattering plane. Nonzero values of P5 and Pe would violate parity conservation if Px = 0, since the electron beam geometry would remain unchanged unless there is an x-component of Pe. Similarly the tilt (e) in the charge-cloud distribution out of the scattering plane indicated in fig. 9.7 must vanish unless Px 0. 

---