Neutral current interaction

The Hamiltonian considered above, which connmites with E, involves the electromagnetic forces between the nuclei and electrons. However, there is another force between particles, the weak interaction force, that is not invariant to inversion. The weak charged current mteraction force is responsible for the beta decay of nuclei, and the related weak neutral current interaction force has an effect in atomic and molecular systems. If we include this force between the nuclei and electrons in the molecular Hamiltonian (as we should because of electroweak unification) then the Hamiltonian will not conuuiite with , and states of opposite parity will be mixed. However, the effect of the weak neutral current interaction force is mcredibly small (and it is a very short range force), although its effect has been detected in extremely precise experiments on atoms (see, for... 

S. L. Glashow (Harvard), A. Salam (Imperial College, London) and S- Weinberg (Harvard) contributions to the theory of the unified weak and electromagnetic interaction between elementary particles, including, inter alia, the prediction of the weak neutral current. 

Garay, A. S. Hrasko, P. Neutral currents un weak interactions and molecular asymmetry in International symposium on the generation and amplification of asymmetry in chemical systems Thiemann, W Ed. Juelich, Germany, 1974, pp 449-469. 

Ahlen, S. P, Avignone, F. T., Brodzinski, R. L., Drukier, A. K., Gelmini, G. Spergel, D. N. 1987. Limits On Cold Dark Matter Candidates From An Ultralow Background Germanium Spectrometer, Phys. Lett. B195, 603 Ahmad, Q. R., et al. [SNO Collaboration] 2002. Direct evidence for neutrino flavor transformation from neutral-current interactions in the Sudbury Neutrino Observatory, Phys. Rev. Lett.89, 011301 Ahrens, J., et al. [AMANDA Collaboration] 2002. Limits to the muon flux from WIMP annihilation in the center of the earth with the AMANDA detector, Phys. Rev. D66, 032006... 

In the "nonrigid symmetric-top rotors" (such as NH ), the second-order Stark effect is observed under normal circumstances. Indeed, field strengths of the order of 1 600 000 [V/m] are required to bring the interaction into the first-order regime in this case [18]. In contrast, very weak interactions suffice to make the mixed-parity states and appropriate for the description of optically active systems. Parity-violating neutral currents have been proposed as the interaction missing from the molecular Hamiltonian [Eq.(1)] that is responsible for the existence of enantiomers [14,19]. At present, this hypothesis is still awaiting experimental verification. 

The principal error of 1.34 kHz arises from the uncertainty of p/pp. The second uncertainty arises from that in a based on the electron g-2 experiment(26), and the third is the estimate of the theoretical error in the latest QED calculation(24). Weak neutral current effects associated with Z exchange in the e - p interaction contribute -0.065 kHz or 15 ppb and are included in Av. The experimental and theoretical values for Av j ee well ... 

Ahmad, Q. R. et al. (The Sudbury Neutrino Observatory Collaboration) Direct Evidence for Neutrino Flavor Transformation from Neutral-Current Interactions in the Sudbury Neutrino Observatory. Physical Review Letters 2002,59,011301-1. 

C. Bouchiat, C. Piketty, Nuclear spin dependent parity violating electron-nucleus interaction in heavy atoms. The anapole moment and the perturbation of the hadronic vector neutral current by the hyperfine interaction, Phys. Lett. B 269 (1991) 195-200. 

A far-reaching communication has concluded that there is an intrinsic energy difference between enantiomeric chemical species. The results, from an initio calculation, depend on "parity-violating weak interactions" due primarily to the electron-neutron potential component of the weak neutral current present in atomic nuclei. Application to the model sugar, hydrated glyceraldehyde, indicated that the D-enantiomer is of lower energy, which, if taken as a energy difference, corresponds to an enantiomeric excess... 

Korobov VI (1996) Phys Rev A 54 R1749 Korobov VI (1999) Hyperfine Interact 119 185 Korobov VI, Bakalov DD (1997) Phys Rev Lett 79 3379 Kostdecky VA (1997) In Flavor-changing neutral currents, Proceedings of the international symposium, Santa Monica, 1997, p 334... 

LL The Weak Interaction—Charged Currents and Neutral Currents... 

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. 

Parity violation is the important key to observing the weak interaction in atoms. Since all the other forces in nature, so far as known, conserve parity, their effect is to put the atom in a state of definite parity. Any mixing of parity states would then be due to the weak interaction. Furthermore, as discussed above, these weak interactions must involve only the previously unseen neutral current form. 

We now present a rather complete treatment of the neutral current weak interaction in atoms. We will start with the relativistic neutral current interaction between electrons and nucleons and use it with suitable approximations to discuss the amplitudes of parity mixing in atoms. Time reversal symmetry is assumed throughout. The PNC neutral current interaction between electrons makes only a small relative contribution in heavy atoms and therefore will not be considered here. 

If one adopts a model-independent approach to the weak neutral current interaction, the atomic experiments supply certain information about the coupling constants not provided by high-energy experiments. Atomic experiments are necessary, as we will now show, in order to set stringent limits on the neutral current parameters and test theories (including, but not restricted to Weinberg-Salam) that predict values of these parameters. 

It is interesting to note that whereas there are neutral currents amongst the Jj (e.g. J3 and Jg a,re both neutral) they play no role in the weak interactions in the Cabibbo theory. It will be seen later that there is now explicit evidence for neutral currents in weak interactions. 

Finally we examine the new weak neutral current interaction which arises as a consequence of the existence of the Z boson. 

Certain limited tests can be made without any model of the strong interactions (Paschos and Wolfenstein, 1973). What is tested is the relationship between cross-sections that depend on the electromagnetic current the charged cinrrent and neutral current which is coupled to the... 

---