Neutrino - Abdul Ghani Memon CHEM 135-02 October 8, 2010...

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Abdul Ghani Memon CHEM 135-02 October 8, 2010 Neutrino Neutrinos are one of the fundamental particles which make up the universe. They are also one of the least understood. Neutrinos are similar to the more familiar electron, with one crucial difference: neutrinos do not carry electric charge. Because neutrinos are electrically neutral, they are not affected by the electromagnetic forces which act on electrons. Neutrinos are affected only by a "weak" sub-atomic force of much shorter range than electromagnetism, and are therefore able to pass through great distances in matter without being affected by it. Neutrinos interact only by the weak force: hence the reaction cross sections are much smaller than those of other particle species. For electron neutrinos the elastic scattering with electrons can be mediated by charged and neutral weak bosons, whereas the scattering of muon and tau neutrinos from electrons is mediated only by the neutral boson. Hence the differences of the total cross sections. The inelastic scattering processes are caused only by the charged currents. The cross section formulae for tau neutrinos are the same as for muon neutrinos. Atmospheric neutrinos are produced as decay products in hadronic showers resulting from collisions of cosmic rays with nuclei in the upper atmosphere. Solar neutrinos originate from the nuclear fusion powering the Sun and other stars. The details of the operation of the Sun are explained by the Standard Solar Model. In short: when four protons fuse to become one helium nucleus, two of them have to convert into neutrons, and each such conversion releases one electron neutrino. The Sun sends enormous numbers of neutrinos in all directions. Every second, about 65 billion (6.5×10 10 ) solar neutrinos pass through every square centimeter on the part of the Earth that faces the Sun. Since neutrinos are insignificantly absorbed by the mass of the Earth, the surface area on the side of the Earth
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Neutrino - Abdul Ghani Memon CHEM 135-02 October 8, 2010...

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