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OALib Journal期刊

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Test of non-standard neutrino properties with the BOREXINO source experiments
A. Ianni,D. Montanino,G. Scioscia
Physics , 1999, DOI: 10.1007/s100529900031
Abstract: We calculate the event rates induced by high-intensity radioactive sources of nu_e (51Cr) and of anti-nu_e (90Sr), to be located near the BOREXINO detector. Calculations are performed both in the standard case and assuming non-standard properties of neutrinos, including flavor oscillations, neutrino electromagnetic interactions, and deviations from the standard vector and axial couplings in the nu_e-e interaction. It is shown that, in some cases, the current limits on non-standard neutrino properties can be significantly improved.
Accelerator and Reactor Neutrino Oscillation Experiments in a Simple Three-Generation Framework
G. L. Fogli,E. Lisi,G. Scioscia
Physics , 1995, DOI: 10.1103/PhysRevD.52.5334
Abstract: We present a new approach to the analysis of neutrino oscillation experiments, in the one mass-scale limit of the three-generation scheme. In this framework we reanalyze and recombine the most constraining accelerator and reactor data, in order to draw precise bounds in the new parameter space. We consider our graphical representations as particularly suited to show the interplay among the different oscillation channels. Within the same framework, the discovery potential of future short and long baseline experiments is also investigated, in the light of both the recent signal from the LSND experiment and the atmospheric neutrino anomaly.
Muon-anti-neutrino <---> electron-anti-neutrino mixing: analysis of recent indications and implications for neutrino oscillation phenomenology
G. L. Fogli,E. Lisi,G. Scioscia
Physics , 1997, DOI: 10.1103/PhysRevD.56.3081
Abstract: We reanalyze the recent data from the Liquid Scintillator Neutrino Detector (LSND) experiment, that might indicate anti-nu_mu<--->anti-nu_e mixing. This indication is not completely excluded by the negative results of established accelerator and reactor neutrino oscillation searches. We quantify the region of compatibility by means of a thorough statistical analysis of all the available data, assuming both two-flavor and three-flavor neutrino oscillations. The implications for various theoretical scenarios and for future oscillation searches are studied. The relaxation of the LSND constraints under different assumptions in the statistical analysis is also investigated.
Factores que afectan el éxito reproductivo y la calidad de la nidada del pingüino patagónico (Spheniscus Magellanicus) en el Canal Beagle, Tierra del Fuego, Argentina
Scioscia,Gabriela; Raya Rey,Andrea; Favero,Marco; Schiavini,Adrián;
El hornero , 2010,
Abstract: the aim of this work was to study foraging trip duration and body size of male and female magellanic penguins during the breeding season and to determine the association of these parameters with both reproductive success and clutch quality in a colony located in the beagle channel, tierra del fuego. trip duration differed significantly between sexes and between breeding stages. females performed longer trips than males during incubation. we suggest that this could be due to differences in body reserves and foraging capabilities related with their body condition. in both sexes, foraging trips during incubation were longer than in the other stages, while the shortest trips were observed during early chick rearing. trips were shorter when chicks were smaller and required greater parental care. a high value of reproductive success (1.51 chicks per nest) was recorded in comparison to that observed in colonies from the malvinas islands and punta tombo. these results could be related to differences in food availability in nearby waters. body size of parents was not associated with reproductive success. notwithstanding, larger females produced larger chicks at early moult and clutches of higher quality. the correlation between female body size and chick size at early moult suggests an important contribution of females on chick's development.
A phenomenological outlook on three-flavor atmospheric neutrino oscillations
G. L. Fogli,E. Lisi,A. Marrone,G. Scioscia
Physics , 1999,
Abstract: The recent observations of atmospheric nu events from the Super-Kamiokande experiment are compatible with three-flavor neutrino oscillations, occurring dominantly in the nu_mu<--->nu_tau channel and subdominantly in the nu_mu<--->nu_e channel. We present an updated analysis of the three-flavor mass-mixing parameters consistent with the present phenomenology, including the latest 45 kTy data sample from Super-Kamiokande. A comparison with our previous results, based on 33 kTy data, shows that the oscillation evidence is strengthened, and that the neutrino mass-mixing parameters are constrained in smaller ranges.
Testing violations of special and general relativity through the energy dependence of nu_mu<--->nu_tau oscillations in the Super-Kamiokande atmospheric neutrino experiment
G. L. Fogli,E. Lisi,A. Marrone,G. Scioscia
Physics , 1999, DOI: 10.1103/PhysRevD.60.053006
Abstract: The atmospheric neutrino data collected by the Super-Kamiokande experiment span about four decades in neutrino energy E, and are thus appropriate to probe the energy dependence of the oscillation wavelength \lambda associated to nu_mu<--->nu_tau flavor transitions, when these are assumed to explain the data. Such dependence takes the form \lambda^{-1}\propto E^n in a wide class of theoretical models, including ``standard'' oscillations due to neutrino mass and mixing (n=-1), energy-independent oscillations (n=0), and violations of the equivalence principle or of Lorentz invariance (n=1). We study first how the theoretical zenith distributions of sub-GeV, multi-GeV, and upward-going muon events change for different integer values of n. Then we perform a detailed analysis of the Super-Kamiokande data by treating the energy exponent n as a free parameter, with unconstrained scale factors for both the amplitude and the phase of nu_mu<--->nu_tau oscillations. We find a best-fit range n=-0.9 \pm 0.4 at 90% C.L., which confirms the standard scenario (n=-1) as the dominant oscillation mechanism, and strongly constrains possible concurrent exotic processes (n \neq -1). In particular, we work out the interesting case of leading standard oscillations plus subleading terms induced by violations of special or general relativity principles, and obtain extremely stringent upper bounds on the amplitude of such violations in the (nu_mu,nu_tau) sector.
Three-flavor atmospheric neutrino anomaly
G. L. Fogli,E. Lisi,D. Montanino,G. Scioscia
Physics , 1996, DOI: 10.1103/PhysRevD.55.4385
Abstract: We investigate the indications of flavor oscillations that come from the anomalous flavor composition of the atmospheric neutrino flux observed in some underground experiments. We study the information coming from the neutrino-induced $\mu$-like and $e$-like events both in the sub-GeV energy range (Kamiokande, IMB, Fr{\'e}jus, and NUSEX experiments) and in the multi-GeV energy range (Kamiokande experiment). First we analyze all the data in the limits of pure $\nu_\mu\leftrightarrow\nu_\tau$ and $\nu_\mu\leftrightarrow\nu_e$ oscillations. We obtain that $\nu_\mu\leftrightarrow\nu_e$ oscillations provide a better fit, in particular to the multi-GeV data. Then we perform a three-flavor analysis in the hypothesis of dominance of one neutrino square mass difference, $m^2$, implying that the neutrino mixing is parametrized by two angles, $(\psi,\,\phi)\in[0,\,\pi/2]$. We explore the space $(m^2,\,\psi,\,\phi)$ exhaustively, and find the regions favored by the oscillation hypothesis. The results are displayed in a form suited to the comparison with other flavor oscillation searches at accelerator, reactor, and solar $\nu$ experiments. In the analysis, we pay particular attention to the earth matter effects, to the correlation of the uncertainties, and to the symmetry properties of the oscillation probability.
Super-Kamiokande atmospheric neutrino data, zenith distributions, and three-flavor oscillations
G. L. Fogli,E. Lisi,A. Marrone,G. Scioscia
Physics , 1998, DOI: 10.1103/PhysRevD.59.033001
Abstract: We present a detailed analysis of the zenith angle distributions of atmospheric neutrino events observed in the Super-Kamiokande (SK) underground experiment, assuming two-flavor and three-flavor oscillations (with one dominant mass scale) among active neutrinos. In particular, we calculate the five angular distributions associated to sub-GeV and multi-GeV \mu-like and e-like events and to upward through-going muons, for a total of 30 accurately computed observables (zenith bins). First we study how such observables vary with the oscillation parameters, and then we perform a fit to the experimental data as measured in SK for an exposure of 33 kTy (535 days). In the two-flavor mixing case, we confirm the results of the SK Collaboration analysis, namely, that \nu_\mu<--->\nu_\tau oscillations are preferred over \nu_\mu<--->\nu_e, and that the no oscillation case is excluded with high confidence. In the three-flavor mixing case, we perform our analysis with and without the additional constraints imposed by the CHOOZ reactor experiment. In both cases, the analysis favors a dominance of the \nu_\mu<--->\nu_\tau channel. Without the CHOOZ constraints, the amplitudes of the subdominant \nu_\mu<--->nu_e and \nu_e<--->\nu_\tau transitions can also be relatively large, indicating that, at present, current SK data do not exclude sizable \nu_e mixing by themselves. After combining the CHOOZ and SK data, the amplitudes of the subdominant transitions are constrained to be smaller, but they can still play a nonnegligible role both in atmospheric and other neutrino oscillation searches. In particular, we find that the \nu_e appearance probability expected in long baseline experiments can reach the testable level of ~15%.
Reconciling solar and terrestrial neutrino oscillation evidences with minimum sacrifice
G. L. Fogli,E. Lisi,D. Montanino,G. Scioscia
Physics , 1997, DOI: 10.1103/PhysRevD.56.4365
Abstract: The present possible evidences in favor of neutrino masses and mixings from solar, atmospheric, and accelerator experiments cannot be all reconciled in a three-family framework, unless some data are excluded. We grade all possible three-family scenarios according to their compatibility with the available data. A recently proposed scenario appears to emerge naturally as the most likely solution to all oscillation evidences, with the only exception of the angular dependence of multi-GeV atmospheric data in the Kamiokande experiment. We describe in detail the status and the phenomenological implications of this ``minimum sacrifice'' solution.
Super-Kamiokande data and atmospheric neutrino decay
G. L. Fogli,E. Lisi,A. Marrone,G. Scioscia
Physics , 1999, DOI: 10.1103/PhysRevD.59.117303
Abstract: Neutrino decay has been proposed as a possible solution to the atmospheric neutrino anomaly, in the light of the recent data from the Super-Kamiokande experiment. We investigate this hypothesis by means of a quantitative analysis of the zenith angle distributions of neutrino events in Super-Kamiokande, including the latest (45 kTy) data. We find that the neutrino decay hypothesis fails to reproduce the observed distributions of muons.
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