科研之友
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摘要
Neutrinos are produced copiously in the early universe. Neutrinos and antineutrinos ceased to be in equilibrium with radiation when the weak interaction rate becomes slower than the rate expansion of the universe. The ratio of the temperature of the photon to the temperature of the neutrino at this stage is T(gamma)/T(nu) = (11/4)(1/3). We investigate the neutrino energy loss due to the oscillation of the electron neutrino into a different flavor in the charged-current interaction of nu(e)-e(-) based on the work of Sulaksono and Simanjuntak. The energy loss from the neutrinos Delta E(nu) during the decoupling of the neutrinos with the rest of the matter would be again in the energy of the electrons and can be obtained from the integration of stopping power equation Delta E(nu) = (dE(nu)/dT(-1))dT(-1) where E(nu) and T are the energy of the neutrinos and the temperature respectively. When the universe expands and matter-radiation decouples, an extra energy will be transferred to the photons via the annihilation of the electron-positron pairs, e( ) e(-) -> gamma gamma. This consequently will increase the temperature of the photons. The net effect to the lowest order is an increase in the ratio of the photon temperature to the neutrino temperature. The magnitude of energy loss of the neutrino is similar to 10(-4) - 10(-5) MeV for the probability of conversion of nu(e) -> nu(i) (i = mu, tau) between 0 to 1.0.
- 出版日期2009-4-30
