Concluding talk at NOW 2006

Abstract

This writeup summarizes the status of neutrino oscillations, including recent fluxes and experimental data, as of summer 2006. A discussion is given on the current status of absolute scale of neutrino mass from tritium, 0νββ and cosmological observations, as well as the prospects for the next generation of experiments, including lepton flavour violation searches, and their theoretical significance. IntoductionWith almost 30 plenary talks and 70 parallel session talks the task of summarizing all of them all into a single talk is an impossible mission. I will try instead simply to highlight some aspects of the talks that touched my own prejudices.The progress in the physics of neutrino oscillations in the last few years has been truly remarkable. Oscillations are now established, implying that neutrinos have masses, as first suggested by theorists in the early eighties, both on general grounds [1,2] and on the basis of various versions of the seesaw mechanism [3]. This is a profound discovery that marks the beginning of a new age in neutrino physics.A gold rush towards precision results has been initiated, whose aim is to probe θ 13 , to study leptonic CP violation and determine the nature of neutrinos. Hopefully this will shed light on the ultimate origin the universe and certainly that of neutrino mass. DataThanks to the accumulation of events over a wide range of energy, and to the measurement over neutrino energy E) distribution of the muon neutrino disappearance probability, the interpretation of the atmospheric data has finally turned into an unambiguous signal of ν µ ↔ ν τ oscillations, marking the beginning of a new era.The interpretation of solar data per se is still ambiguous, with viable alternative explanations involving spin flavour precession [4,5] or nonstandard neutrino interactions [6]. Results on (or relevant to) solar neutrinos were presented here by Broggini, Maneira, Pulido, Raghavan, Ranucci, Serenelli and Smy. Reactor neutrino data from KamLAND not only confirm the solar neutrino deficit but also observe the spectrum distortion as expected for oscillations. Reactors have played an important role in establishing the robustness of the neutrino flavor oscillation interpretation vis a vis the existence of solar density fluctuations [7] in the solar radiative zone as produced by random magnetic fields [8], and also with respect to the effect of convective zone magnetic fields, should neutrinos posses nonzero neutrino transition magnetic moments [9]. Within the oscillation picture KamLAND has also identified large mixing angle oscillation as its "unique" solution, "solving", in a sense, the solar neutrino problem. Note however that the interpretation of solar data vis a vis neutrino non-standard interactions [10] is not yet so robust.A lot more is to come from the upcoming reactor experiments starting with Double-Chooz,

Dark Energy Is the Cosmological Quantum Vacuum Energy of Light Particles—The Axion and the Lightest Neutrino

“…The axion is certainly the one that has caught more attention in the literature. Other proposed particles are the familons and the majorons [56,[84][85][86][87][88][89].…”