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Search Results: 1 - 10 of 297545 matches for " J.;Nunokawa "
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Supernova Bounds on Supersymmetric $R$-parity Violating Interactions
H. Nunokawa,A. Rossi,J. W. F. Valle
Physics , 1996, DOI: 10.1016/S0550-3213(96)00541-X
Abstract: We re-examine resonant massless-neutrino conversions in a dense medium induced by flavour changing neutral current (FCNC) interactions. We show how the observed $\bar\nu_e$ energy spectra from SN1987a and the supernova $r$-process nucleosynthesis provide constraints on supersymmetric models with $R$ parity violation, which are much more stringent than those obtained from the laboratory. We also suggest that resonant massless-neutrino conversions may play a positive role in supernova shock reheating. Finally, we examine the constraints on explicit $R$-parity-violating FCNCs in the presence of non-zero neutrino masses in the eV range, as indicated by present hot dark matter observations.
Discriminating among Earth composition models using geo-antineutrinos
H. Nunokawa,W. J. C. Teves,R. Zukanovich Funchal
Physics , 2003, DOI: 10.1088/1126-6708/2003/11/020
Abstract: It has been estimated that the entire Earth generates heat corresponding to about 40 TW (equivalent to 10,000 nuclear power plants) which is considered to originate mainly from the radioactive decay of elements like U, Th and K, deposited in the crust and mantle of the Earth. Radioactivity of these elements produce not only heat but also antineutrinos (called geo-antineutrinos) which can be observed by terrestrial detectors. We investigate the possibility of discriminating among Earth composition models predicting different total radiogenic heat generation, by observing such geo-antineutrinos at Kamioka and Gran Sasso, assuming KamLAND and Borexino (type) detectors, respectively, at these places. By simulating the future geo-antineutrino data as well as reactor antineutrino background contributions, we try to establish to which extent we can discriminate among Earth composition models for given exposures (in units of kt$\cdot$ yr) at these two sites on our planet. We use also information on neutrino mixing parameters coming from solar neutrino data as well as KamLAND reactor antineutrino data, in order to estimate the number of geo-antineutrino induced events.
Pulsar Velocities without Neutrino Mass
D. Grasso,H. Nunokawa,J. W. F. Valle
Physics , 1998, DOI: 10.1103/PhysRevLett.81.2412
Abstract: We show that pulsar velocities may arise from anisotropic neutrino emission induced by resonant conversions of massless neutrinos in the presence of a strong magnetic field. The main ingredient is a small violation of weak universality and neither neutrino masses nor magnetic moments are required.
Borexino as a test of solar matter density fluctuations
H. Nunokawa,A. Rossi,V. Semikoz,J. W. F. Valle
Physics , 1997, DOI: 10.1016/S0920-5632(98)00447-2
Abstract: This talk summarizes some results of our recent work focusing on the possibility to test solar matter density fluctuations by the future Borexino experiment.
Type-II Supernovae and Neutrino Magnetic Moment
H. Nunokawa,R. Tomas,J. W. F. Valle
Physics , 1998, DOI: 10.1016/S0927-6505(98)00072-3
Abstract: The present solar and atmospheric neutrino data together with the LSND results and the presence of hot dark matter (HDM) suggest the existence of a sterile neutrino at the eV scale. We have reanalysed the effect of resonant {\sl sterile} neutrino conversions induced by neutrino magnetic moments in a type-II supernova. We analyse the implications of $\nu_e-\nu_s$ and $\bar{\nu}_e-\bar{\nu}_s$ ($\nu_s$ denotes sterile neutrino) conversions for the supernova shock re-heating, the detected $\bar\nu_e$ signal from SN1987A and the $r$-process nucleosynthesis hypothesis. Using reasonable magnetic field profiles we determine the sensitivity of these three arguments to the relevant neutrino parameters, i.e. the value of the transition magnetic moment and the $\nu_e-\nu_s$ mass difference $\Delta m^2 \equiv \Delta m^2_{LSND/HDM}$
Probing supernova physics with neutrino oscillations
H. Minakata,H. Nunokawa,R. Tomas,J. W. F. Valle
Physics , 2001, DOI: 10.1016/S0370-2693(02)02376-6
Abstract: 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.
Neutrino mass, mixing and oscillations
Nunokawa, Hiroshi;
Brazilian Journal of Physics , 2000, DOI: 10.1590/S0103-97332000000200015
Abstract: present data from various neutrino experiments are strongly suggesting the existence of neutrino mass and flavor mixing. we review the present status of neutrino oscillation search and various neutrino anomalies and their possible interpretations in terms of oscillation induced by neutrino mass and flavor mixing.
Neutrino mass, mixing and oscillations
Nunokawa Hiroshi
Brazilian Journal of Physics , 2000,
Abstract: Present data from various neutrino experiments are strongly suggesting the existence of neutrino mass and flavor mixing. We review the present status of neutrino oscillation search and various neutrino anomalies and their possible interpretations in terms of oscillation induced by neutrino mass and flavor mixing.
Exotic Solutions to the Solar Neutrino Problem and Some Implications for Low Energy Solar Neutrino Experiments
H. Nunokawa
Physics , 2001,
Abstract: 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.
Status of the solutions to neutrino anomalies based on non-standard neutrino interactions
Hiroshi Nunokawa
Physics , 2000, DOI: 10.1016/S0168-9002(01)01289-X
Abstract: We review the status of the solutions to neutrino anomalies by flavor-changing as well as flavor-diagonal neutrino interactions. While it is difficult to explain the atmospheric neutrino data the solar neutrino data can be well accounted for by the massless neutrino oscillation induced by such non-standard neutrino interactions. We also discuss the possibility to test such kind of interactions by the future neutrino oscillation experiments at neutrino factories.
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