1,111 research outputs found
Phenomenology of Neutrino Oscillations
We review the status of several phenomenological topics of current interest
in neutrino oscillations: (i) Solar neutrino oscillations after the first
Sudbury Neutrino Observatory measurements, including both model-independent and
model-dependent results; (ii) Dominant nu_mu-->nu_tau oscillations of
atmospheric and K2K neutrinos, and possible subdominant oscillations induced by
either extra states or extra interactions; and (iii) Four-neutrino scenarios
embedding the controversial LSND evidence for oscillations.Comment: 9 pages, including 12 figures. Presented at TAUP 2001: Topics in
Astroparticle and Underground Physics, Assergi, Italy, 8-12 Sep. 200
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 \nu_\mu-->\nu_\tau channel provides an excellent 2\nu fit to
the data, one cannot exclude, at present, the occurrence of additional
subleading \nu_\mu-->\nu_e oscillations (3\nu schemes) or of sizable
\nu_\mu-->\nu_s oscillations (4\nu schemes). 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.Comment: Talk at the 19th International Conference on Neutrino Physics and
Astrophysics - Neutrino 2000 (Sudbury, Ontario, Canada, 16-21 June 2000
Super-Kamiokande atmospheric neutrinos: Status of subdominant oscillations
In the context of the recent (79.5 kTy) Super-Kamiokande atmospheric neutrino
data, we concisely review the status of muonic-tauonic flavor oscillations and
of the subdominant electron or sterile neutrino mixing, in schemes with three
or four families and one dominant mass scale. In the three-family case, where
we include the full CHOOZ spectral data, we also show, through a specific
example, that ``maximal'' violations of the one-dominant mass scale
approximation are not ruled out yet.Comment: 8 pages + 10 figure
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
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.
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
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
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
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