NEUTRINO PHYSICS AND (Electron-Positron) ANNIHILATION INTO NEUTRINO PAIR

Abstract

Some spin and interference phenomena in neutrino-electron interactions are investigated. The cross section of elastic neutrino (antineurino) – electron scattering with account of electromagnetic neutrino interaction is calculated. It was shown that elecromagnetic terms of the neutrino (antineurino) scattering cross section do not depend on the electron polatrization se and have the same form for neutrinos and antineutrinos. This gives a possibility to determine an upper limit on the neutrino magnetic moment or to measure it. The influence of non-zero mass neutrino on the energy dependence of elastic ve- (ϋe-) – scattering cross section is investigated in the framework of general (S, P, T, V, A) – four fermion interactions using correct description of the massive neutrino helicity states. To improve the sensitivity of the search for the neutrino magnetic moment , the using of a polarized electron target in the processes of neutrino (antineutrino)- electron scattering was suggested. It is shown that in this case , the weak interaction term in the total cross section is few times smaller compared with the unpolarized case, but the electromagnetic term does not depend on electron polarization. The standard model deals with the electroweak interaction and calculation of energy emitted from hot stars, by e+ e- - pair annihilation into neutrino is one of its application. But this model did not calculate the missing energy from hot stars and also the cross section for e+ e- - pair neutrino annihilation, in defferent cases for electron and positron spins orientations for e- e+ → vv process. Differential and integrated cross sections, as well as integral forward- backwrad asymmetries of the e- e+ → vv annihilation are studied for different e- e+ beams polrizations. Particularly it is shown that variation of the charged and neutral currents relative contributions is manifested in anomalous decreases of the cross section for e+R e-L → ve ve annihilation in the region √s < Mz. At higher energies this cross section extends to a plateau so that e- e+ → ve ve channel prevails over that of νμνμ of ντντ pairs productions. Also the cross section for the production of ultrarelativistic electron- positron pair muon neutrino and antineutrino annihilation in an external electromagnetic field is calculated. The asymptotic behavior of the cross section as a function of the kinematical and field parameters is studied. It is shown that the new channel of the reaction νμνμ → e- e+ arises at the expenses of quantum effects. For the strong magnetic field case, the cross section of the process does not depend on the masses of such kind of particles so- called charged leptons. The contribution of the weak external field to the cross section of the process is very small. It is shown that the considered process can be one of the possible sources of cosmic electrons and positrons of high energy. This study deals, too, with electromagnetic momenta effects of neutrino to calculate the missing energy from hot stars by e+ e- - pair neutrino annihilation and compares it with the standard electroweak model Glashow, Weinbarge, and Salam (GWS). It was found that the deviation from the standard electroweak model would not exceed 13% in temperature range [109 – 1010] ok. It was also found that the power of neutrino radiation which accompanies electron- neutrino pair (ve ve) production equal the double value which accompanies moun- neutrino pair (vμ vμ ) production.