The Neutrio World中微子的世界.pptVIP

The Neutrino Revolution(1998 – …) The Physics of Neutrino Oscillation  Neutrinos Come in at Least Three Flavors The known neutrino flavors: ?e , ?? , ?? The Meaning of this Association Let Us Assume Neutrino Masses and Leptonic Mixing Neutrino mass — There is some spectrum of 3 or more neutrino mass eigenstates ?i: How Does the Large Mixing Angle MSW Effect Work? The solar matter effect is important for the high-energy 8B neutrinos, not the low-energy pp neutrinos. Since ν3 couples at most feebly to electrons (to be discussed), and solar neutrinos are born νe, the solar neutrinos are mixtures of just ν1 and ν2. (Convention: ν2 heavier than ν1). This is a 2-neutrino system. Solar neutrino flavor change is νe ? νx, where νx is some combination of νμ and ν?. In the sun, At the center of the sun, √2GFNe ≈ 0.75 × 10-5 eV2 / MeV . For Δm2sol ≈ 8 × 10-5 eV2 and typical 8B neutrino energy of ~ 8 MeV, Δm2sol / 4E ≈ 0.25 × 10-5 eV2 / MeV . The interaction term in H dominates, and νe is approximately an eigenstate of H.* * * * Neutrino Phenomenology Boris Kayser Scottish Summer School August 9, 2006 + Neutrinos have nonzero masses! Leptons mix! These discoveries come from the observation of neutrino oscillation. Each of these is associated with the corresponding charged-lepton flavor: e , ? , ? ?e Detector ?e e W boson Short Journey e ?? ?? ? ? W ?? ?? ? ? W Over short distances, neutrinos do not change flavor. ??? ?? ? ? W Short Journey Does Not Occur But if neutrinos have masses, and leptons mix, neutrino flavor changes do occur during long journeys. (Mass)2 ?1 ?2 ?3 ?4 Mass (?i) ?? mi Leptonic mixing — When W+ ? l?+ + ?? , the produced neutrino state |?? is |?? = ? U*?i |?i . Neutrino of flavor ? Neutrino of definite mass mi Leptonic Mixing Matrix le ? e, l? ? ?, l? ? ? e, ?, or ? i Another way to look at W decay: A given l?+ can be accompanied by any ?i. Amp(W+ ? l?+ + ?i) = U*?i is |?? = ? U*