Electron-neutrino scattering

The synthesis of the light elements is sensitive to physical conditions in the early radiation-dominated era at temperatures T < 1 MeV, corresponding to an age r > 1 s. At these and higher temperatures, weak interactions rates Tweak > H were rapid compared to the expansion rate, and thus the weak interactions were in thermal equilibrium. In particular, the processes which interconvert neutrons and protons through scatterings with electrons (e ), positrons (e ), electron neutrinos (ve) and electron anti-neutrinos (v ), namely... 

Neutrinos of all types, Vg, v, and Vr, can scatter elastically from an electron. This process is a result of the weak-interaction coupling between the neutrino and the charged lepton, a coupling that may have a charged and a neutral current component. The cross section for scattering from electrons depends on the neutrino type, Vg, and whether it is a neutrino or an antineutrino. Only the electron neutrino is coupled to the electron by both the charged and the neutral currents, whereas other neutrino types are coupled by neutral currents. These reactions may be represented schematically as follows ... 

In conclusion, we mention the following statistically weak observational oddities the 7 sec time gap in Kamiokande data, the lack of late time events in IM8, the occurrence of two possible electron scattering events very early in time, and the discrepancy of the Kamiokande and IMB average neutrino energies. The work on particle models is being pursued with G. Fuller, R. Mayle, K. Olive, D. Schramm. 

The Sudbury Neutrino Observatory (SNO) detector, located at Sudbury, Ontario, Canada, consists of 1000 tons of heavy water (D20) mounted 2 km below the surface in the Sudbury Nickel Mine. In addition to neutrino-electron scattering, this detector can also utilize nuclear reactions involving deuterium ... 

Electron scattering by photons may alternatively result in pair neutrino production, with a nett energy loss as shown ... 

In this reaction, the e is a positron and the Ve is an electron-type neutrino. Significantly, this reaction depends on the weak force since it requires one of the two reacting protons to convert into a neutron in the brief moment the two protons are in close contact. This is rare, so the vast majority of proton-proton scatterings in a star do not result in deuterium production. The deuterium, that is, the H, produced by the pp reaction quickly captures a proton to become He ... 

Turning to the other process, the scattering cross section of neutrinos by electrons, for which Nahmias investigation was imdertaJcen, there is no reason to modify his and Bethe s conclusions (ibid, p. 108). The cross section in this case is less than 10 " cm. ... 

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. 

In Figure 10 we make a two-dimensional plot of a and y, and show the area allowed by Eq. (43) and all atomic results from Table 3. Also shown in Figure 10 is the area allowed by the polarized electron scattering results [Eq. (42)], plus further restrictions imposed on a, y by neutrino experiments if the factorization hypothesis is included. One can see that the atomic PNC results significantly exclude values of the parameters that would otherwise be allowed. It is noteworthy, of course, that the Weinberg-Salam theory falls within all allowed regions. 

Figure 10. Restrictions placed on y and a (see text) by the heavy atom atomic experiments, polarized electron scattering, and neutrino experiments. The Weinberg-Salam theory falls well within the intersection of all experiments.

Fig. 5.1. Lowest order Feynman diagrams for neutrino-electron scattering, and...

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