2,116 research outputs found
The second Book of Aristotle's Politics
The second Book of the Politics has been object of multiple considerations, but it has called the attention of the scholars mainly because of its detailed criticism of Plato's political projects, especially the Republic. In fact Aristotle devotes 6 of the 12 chapters of Book II to examine Plato's proposals. Most of the scholarly contributions are focused on the criticism of Plato trying either to demonstrate the justice of Aristotle's reproaches or to invalidate his chapters on the basis of a supposed inexactness of his words
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 \nu_\mu-->\nu_\tau and \nu_\mu-->\nu_s oscillations. We
show that, although the Super-Kamiokande data disfavor the pure \nu_\mu-->\nu_s
channel, they do not exclude its occurrence, with sizable amplitude, in
addition to the \nu_\mu-->\nu_\tau channel. 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 \nu
solutions are compatible with analogous solutions to the solar neutrino
problem, which involve oscillations of \nu_e in both sterile and active states.Comment: Added references. Accepted for publication in Phys. Rev.
The Higgs Boson Mass from Precision Electroweak Data
We present a new global fit to precision electroweak data, including new low-
and high-energy data and analyzing the radiative corrections arising from the
minimal symmetry breaking sectors of the Standard Model (SM) and its
supersymmetric extension (MSSM). It is shown that present data favor a Higgs
mass of O(M_Z): M_H = 76+152-50 GeV. We confront our analysis with
(meta)stability and perturbative bounds on the SM Higgs mass, and the
theoretical upper bound on the MSSM Higgs mass. Present data do not
discriminate significantly between the SM and MSSM Higgs mass ranges. We
comment in passing on the sensitivity of the Higgs mass determination to the
values of alpha(M_Z) and alpha_s(M_Z).Comment: 10 pages, latex, 8 figures as uu-encoded postscript fil
Analysis of energy- and time-dependence of supernova shock effects on neutrino crossing probabilities
It has recently been realized that supernova neutrino signals may be affected
by shock propagation over a time interval of a few seconds after bounce. In the
standard three-neutrino oscillation scenario, such effects crucially depend on
the neutrino level crossing probability P_H in the 1-3 sector. By using a
simplified parametrization of the time-dependent supernova radial density
profile, we explicitly show that simple analytical expressions for P_H
accurately reproduce the phase-averaged results of numerical calculations in
the relevant parameter space. Such expressions are then used to study the
structure of P_H as a function of energy and time, with particular attention to
cases involving multiple crossing along the shock profile. Illustrative
applications are given in terms of positron spectra generated by supernova
electron antineutrinos through inverse beta decay.Comment: Major changes both in the text and in the figures in order to include
the effect of a step-like shock front density profile; final version to
appear in Physical Review
Addendum to: Model-dependent and -independent implications of the first Sudbury Neutrino Observatory results
In the light of recent experimental and theoretical improvements, we review
our previous model-independent comparison [hep-ph/0106247] of the
Super-Kamiokande (SK) and Sudbury Neutrino Observatory (SNO) solar neutrino
event rates, including updated values for the ``equalized'' SK datum and for
the reference Standard Solar Model (SSM) B neutrino flux. We find that the
joint SK+SNO evidence for active neutrino flavor transitions is confirmed at
the level of 3.3 standard deviations, independently of possible transitions to
sterile states. Barring sterile neutrinos, we estimate the 3-sigma range for
the B neutrino flux (normalized to SSM) as f_B=0.96 +0.54-0.55.
Accordingly, the 3-sigma range for the energy-averaged nu_e survival
probability is found to be = 0.31 +0.55-0.16, independently of the
functional form of P_ee. An increase of the reference nu_e + d --> p + p + e
cross section by ~3%, as suggested by recent theoretical calculations, would
slightly shift the central values of f_B and of to ~1.00 and ~0.29,
respectively, and would strengthen the model-independent evidence for nu_e
transitions into active states at the level of ~3.6 sigma.Comment: 6 pages + 2 figures. Addendum to hep-ph/010624
Global analysis of three-flavor neutrino masses and mixings
We present a comprehensive phenomenological analysis of a vast amount of data
from neutrino flavor oscillation and non-oscillation searches, performed within
the standard scenario with three massive and mixed neutrinos, and with
particular attention to subleading effects. The detailed results discussed in
this review represent a state-of-the-art, accurate and up-to-date (as of August
2005) estimate of the three-neutrino mass-mixing parameters.Comment: Final version (including a new Appendix), to be published in
"Progress in Particle and Nuclear Physics". Higher-resolution pdf file and
eps figures can be download from http://www.ba.infn.it/~now2004/PPNP_review
Zenith distribution of atmospheric neutrino events and electron neutrino mixing
Assuming atmospheric neutrino oscillations with dominant nu_munu_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_munu_tau transitions) do not vanish
in the limit of energy-averaged oscillations.Comment: 6 pages, RevTeX, no figure
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