Boris Kayser at Fermilab put on arXiv as nice summary of the state of the art in Neutrino Physics yesterday. It is here: http://es.arxiv.org/PS_cache/hep-ph/pdf/0506/0506165.pdf [Broken] The presentation is more lucid than most. The paper definitely find that neutrions can change flavor which implies that they have nonzero masses and that leptons mix. The exact equations and experimental basis for this is spelled out. Considerable attention is devoted to the complications associated with the fact that most experimentally detected neutrinos travel through not a vacuum, but the Earth, before reaching a detector, and the results hinge among other things, on the assumption that quark-neutrino interactions do not change neutrino flavor (which seems to be reasonable). The open questions identified: How many neutrino species are there? Are there sterile neutrinos? The Liquid Scintillator Neutrion Detector (LSND) says more than three flavors and that some of those flavors are "sterile". Other experiments thus far have detected only three flavors (electron, muon and tau). Sterile neutrions are those which do not couple to the W or Z, only to gravity [making them plausible WIMPs among other things]. The MiniBooNE experiments are pegged as key to resolving this issue. [This is quite important theoretically, since if previous patterns hold, more than three flavors of neutrinos would imply more than three flavors of every other kind of fermion.] What are the masses of the neutrion mass eigenstates? The heaviest is thought to be between 0.4 eV and 0.4 eV. All are thought to be non-zero. How large is omega sub 13? This is a constant which establishes whether higher order neutrinos are lighter or heavier than lower order neutrinos and also whether there are neutrino CP violations. Are neutrinos their own antiparticles? If neutrinoless double beta decay is observed, then they are. Do neutrio interactions violate CP? Is neutrino CP violation the reason we exist? The first question is a straightforward yes or no. The latter question is a reference to the continuing puzzle of the abundance of matter relative to antimatter in the universe.