Exotic Solutions to the Solar Neutrino Problem and Some Implications for Low Energy Solar Neutrino Experiments

In this talk, I review, from the phenomenological point of view, solutions to the solar neutrino problem, which are not provided by the conventional neutrino oscillation induced by mass and flavor mixing, and show that they can provide a good fit to the observed data. I also consider some simple implications for low energy solar neutrino experiments.Comment: Talk presented at International Workshop on Low Energy Solar Neutrinos (LowNu2), 4-5, December, 2000, Tokyo, Japan, to be published in Proceedings (World Scientific

Probing supernova physics with neutrino oscillations

We point out that solar neutrino oscillations with large mixing angle as evidenced in current solar neutrino data have a strong impact on strategies for diagnosing collapse-driven supernova (SN) through neutrino observations. Such oscillations induce a significant deformation of the energy spectra of neutrinos, thereby allowing us to obtain otherwise inaccessible features of SN neutrino spectra. We demonstrate that one can determine temperatures and luminosities of non-electron flavor neutrinos by observing bar{nu}_{e} from galactic SN in massive water Cherenkov detectors by the charged current reactions on protons.Comment: 6 pages. Typos corrected and references added. Version to be published in Physics Letters

CERN to Gran Sasso: An ideal distance for superbeam?

We use the CP trajectory diagram as a tool for pictorial representation of the genuine CP and the matter effects to explore the possibility of an in situ simultaneous measurement of \delta and the sign of \Delta m^2_{13}. We end up with a low-energy conventional superbeam experiment with a megaton-class water Cherenkov detector and baseline length of about 700 km. A picturesque description of the combined ambiguity which may arise in simultaneous determination of \theta_{13} and the above two quantities is given in terms of CP trajectory diagram

What can we learn about the lepton CP phase in the next 10 years?

We discuss how the lepton CP phase can be constrained by accelerator and reactor measurements in an era without dedicated experiments for CP violation search. To characterize globally the sensitivity to the CP phase \delta_{CP}, we introduce a new measure, the CP exclusion fraction, which quantifies what fraction of the \delta_{CP} space can be excluded at a given input values of \theta_{23} and \delta_{CP}. Using the measure we study the CP sensitivity which may be possessed by the accelerator experiments T2K and NOvA. We show that, if the mass hierarchy is known, T2K and NOvA alone may exclude, respectively, about 50%-60% and 40%-50% of the \delta_{CP} space at 90% CL by 10 years running, provided that a considerable fraction of beam time is devoted to the antineutrino run. The synergy between T2K and NOvA is remarkable, leading to the determination of the mass hierarchy through CP sensitivity at the same CL.Comment: Analyses and plots improved, conclusions unchanged, 23 pages, 8 figures, 1 tabl

Constraining the absolute neutrino mass scale and Majorana CP violating phases by future neutrinoless double beta decay experiments

Assuming that neutrinos are Majorana particles, in a three generation framework, current and future neutrino oscillation experiments can determine six out of the nine parameters which fully describe the structure of the neutrino mass matrix. We try to clarify the interplay among the remaining parameters, the absolute neutrino mass scale and two CP violating Majorana phases, and how they can be accessed by future neutrinoless double beta ($0\nu\beta\beta$) decay experiments, for the normal as well as for the inverted order of the neutrino mass spectrum. Assuming the oscillation parameters to be in the range presently allowed by atmospheric, solar, reactor and accelerator neutrino experiments, we quantitatively estimate the bounds on $m_0$, the lightest neutrino mass, that can be infered if the next generation $0\nu\beta\beta$ decay experiments can probe the effective Majorana mass ($m_{ee}$) down to $\sim$ 1 meV. In this context we conclude that in the case neutrinos are Majorana particles: (a) if m_0 \gsim 300 meV, {\em i.e.}, within the range directly attainable by future laboratory experiments as well as astrophysical observations, then m_{ee} \gsim 30 meV must be observed; (b) if $m_0 < 300$ meV, results from future $0\nu\beta\beta$ decay experiments combined with stringent bounds on the neutrino oscillation parameters, specially the solar ones, will place much stronger limits on the allowed values of $m_0$ than these direct experiments.Comment: 26 pages, 11 encapsulated postscript figures. A new figure and minor changes are included. To be published in Phys. Rev.