arXiv subjects

A. Marrone

Publications and source records attributed to A. Marrone.

51 records · Page 3Linked to original sources

arXiv2001

Atmospheric, Solar, and CHOOZ neutrinos: a global three generation analysis

We perform a global three generation analysis of the current solar and atmospheric evidence in favor of neutrino oscillations. We also include the negative results coming from CHOOZ to constrain the nu_e mixing. We study the zones of mass-mixing oscillations parameters compatible with all the data. It is shown that almost pure nu_mu <--> nu_tau oscillations are required to explain the atmospheric neutrino anomaly and almost pure nu_1 <--> nu_2 oscillations to account for the solar neutrino deficit.

hep-ph↗

arXiv2001

Four-neutrino mixing solutions of the atmospheric neutrino anomaly

Solutions to the atmospheric neutrino anomaly which smoothly interpolate between nu_mu -> nu_tau and nu_mu -> nu_s oscillations are studied. It is shown that, although the Super-Kamiokande data disfavor the pure nu_mu -> nu_s channel, one cannot exclude sizable amplitude for the nu_mu -> nu_s channel in addition to nu_mu -> nu_tau oscillations.

hep-ph↗

arXiv2000

Four-neutrino oscillation solutions of the atmospheric neutrino anomaly

In the context of neutrino scenarios characterized by four (three active plus one sterile) neutrino species and by mass spectra with two separated doublets, we analyze solutions to the atmospheric neutrino anomaly which smoothly interpolate between ν_μ-->ν_τand ν_μ-->ν_s oscillations. We show that, although the Super-Kamiokande data disfavor the pure ν_μ-->ν_s channel, they do not exclude its occurrence, with sizable amplitude, in addition to the ν_μ-->ν_τchannel. High energy muon data appear to be crucial in assessing the relative amplitude of active and sterile neutrino oscillations. It is also qualitatively shown that such atmospheric νsolutions are compatible with analogous solutions to the solar neutrino problem, which involve oscillations of ν_e in both sterile and active states.

hep-ph↗

arXiv2000

Analytical description of quasivacuum oscillations of solar neutrinos

We propose a simple prescription to calculate the solar neutrino survival probability P_{ee} in the quasivacuum oscillation (QVO) regime. Such prescription is obtained by matching perturbative and exact analytical results, which effectively take into account the density distribution in the Sun as provided by the standard solar model. The resulting analytical recipe for the calculation of P_{ee} is shown to reach its highest accuracy |ΔP_{ee}| < 2.6 x 10^{-2} in the whole QVO range) when the familiar prescription of choosing the solar density scale parameter r_0 at the Mikheyev-Smirnov-Wolfenstein (MSW) resonance point is replaced by a new one, namely, when r_0 is chosen at the point of ``maximal violation of adiabaticity'' (MVA) along the neutrino trajectory in the Sun. The MVA prescription admits a smooth transition from the QVO regime to the MSW transition one. We discuss in detail the phase acquired by neutrinos in the Sun, and show that it might be of relevance for the studies of relatively short timescale variations of the fluxes of the solar νlines in the future real-time solar neutrino experiments. Finally, we elucidate the role of matter effects in the convective zone of the Sun.

hep-ph↗

arXiv2000

Analysis of oscillations of atmospheric neutrinos

We briefly review the current status of standard oscillations of atmospheric neutrinos in schemes with two, three, and four flavor mixing. It is shown that, although the pure ν_μ-->ν_τchannel provides an excellent 2νfit to the data, one cannot exclude, at present, the occurrence of additional subleading ν_μ-->ν_e oscillations (3νschemes) or of sizable ν_μ-->ν_s oscillations (4νschemes). It is also shown that the wide dynamical range of energy and pathlength probed by the Super-Kamiokande experiment puts severe constraints on nonstandard explanations of the atmospheric neutrino data, with a few notable exceptions.

hep-ph↗

arXiv2000

Probing possible decoherence effects in atmospheric neutrino oscillations

It is shown that the results of the Super-Kamiokande atmospheric neutrino experiment, interpreted in terms of nu_mu<--->nu_tau flavor transitions, can probe possible decoherence effects induced by new physics (e.g., by quantum gravity) with high sensitivity, supplementing current laboratory tests based on kaon oscillations and on neutron interferometry. By varying the (unknown) energy dependence of such effects, one can either obtain strong limits on their amplitude, or use them to find an unconventional solution to the atmospheric nu anomaly based solely on decoherence.

hep-ph↗

arXiv1999

Comments on atmospheric neutrino oscillation scenarios with large nu_mu <-> nu_e transitions

The evidence for $ν_μ$ disappearance in the Super-Kamiokande atmospheric neutrino experiment and the negative searches for $ν_e$ disappearance in the CHOOZ reactor experiment can be easily reconciled by assuming oscillations with large amplitude in the $ν_μ\leftrightarrowν_τ$ channel and small (or null) amplitude in the $ν_μ\leftrightarrowν_e$ channel. It has been claimed, however, that some oscillation scenarios with large $ν_μ\leftrightarrowν_e$ mixing can also be constructed in agreement with the present data. We investigate quantitatively two such scenarios: (a) threefold maximal mixing; and (b) attempts to fit all sources of evidence for oscillations (solar, atmospheric, and accelerator) with three neutrinos. By using mainly Super-Kamiokande data, we show that the case (a) is disfavored, and that the case (b) is definitely ruled out.

hep-ph↗

arXiv1999

Multiscale analysis of blood pressure signals

We describe the multiresolution wavelet analysis of blood pressure waves in vasovagal syncope-affected patients compared with those in healthy people, using Haar and Gaussian bases. A comparison between scale-dependent and scale-independent measures discriminating the two classes of subjects is made. What emerges is a sort of equivalence between these two methodological approaches, that is, both methods reach the same statistical significance of separation between the two classes.

cond-mat.dis-nn↗

arXiv1999

A phenomenological outlook on three-flavor atmospheric neutrino oscillations

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.

hep-ph↗

arXiv1999

Testing violations of special and general relativity through the energy dependence of nu_mu<--->nu_tau oscillations in the Super-Kamiokande atmospheric neutrino experiment

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 λassociated to nu_mu<--->nu_tau flavor transitions, when these are assumed to explain the data. Such dependence takes the form λ^{-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.

hep-ph↗

arXiv1999

Super-Kamiokande data and atmospheric neutrino decay

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.

hep-ph↗

arXiv1998

Wavelet Analysis of Blood Pressure Waves in Vasovagal Syncope

We describe the multiresolution wavelet analysis of blood pressure waves in vasovagal syncope affected patients compared with healthy people. We argue that there exist discriminating criteria which allow us to isolate particular features, common to the syncope-affected patients sample, indicating an alternative diagnosis methodology for this syndrome. We perform a throughout analysis both in the Haar basis and in a Gaussian one, with an attempt to grasp the underlying dynamics.

physics.bio-ph↗

arXiv1998

Super-Kamiokande atmospheric neutrino data, zenith distributions, and three-flavor oscillations

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 μ-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 ν_μ<--->ν_τoscillations are preferred over ν_μ<--->ν_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 ν_μ<--->ν_τchannel. Without the CHOOZ constraints, the amplitudes of the subdominant ν_μ<--->nu_e and ν_e<--->ν_τtransitions can also be relatively large, indicating that, at present, current SK data do not exclude sizable ν_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 ν_e appearance probability expected in long baseline experiments can reach the testable level of ~15%.

hep-ph↗

arXiv1997

Zenith distribution of atmospheric neutrino events and electron neutrino mixing

Assuming atmospheric neutrino oscillations with dominant nu_mu<--->nu_tau transitions, we discuss how subdominant nu_e mixing (within the Chooz reactor bounds) can alter the zenith distributions of neutrino-induced electrons and muons. We isolate two peculiar distortion effects, one mainly related to nu_e mixing in vacuum and the other to matter oscillations, that may be sufficiently large to be detected by the SuperKamiokande atmospheric nu experiment. These effects (absent for pure two-flavor nu_mu<--->nu_tau transitions) do not vanish in the limit of energy-averaged oscillations.

hep-ph↗

arXiv1997

Upward-going muons and neutrino oscillations

The available upward-going muon data from the Kamiokande, Baksan, MACRO, IMB, and SuperKamiokande experiments are reviewed and combined. Bounds on the neutrino mass and mixing parameters are derived for oscillations in two and three flavors. These bounds are not in significant conflict with the oscillation solution to the atmospheric neutrino flavor anomaly observed in the sub-GeV and multi-GeV energy range. The combination of all the available atmospheric data tends to favor the nu_mu <---> nu_e channel with respect to the nu_mu <---> nu_tau channel, and to disfavor the threefold maximal mixing scenario.

hep-ph↗