877 research outputs found
KamLAND Bounds on Solar Antineutrinos and neutrino transition magnetic moments
We investigate the possibility of detecting solar electron antineutrinos with
the KamLAND experiment. These electron antineutrinos are predicted by
spin-flavor oscillations at a significant rate even if this mechanism is not
the leading solution to the SNP. KamLAND is sensitive to antineutrinos
originated from solar B neutrinos. From KamLAND negative results after
145 days of data taking, we obtain model independent limits on the total flux
of solar electron antineutrinos $\Phi({}^8 B)< 1.1-3.5\times 10^4 cm^{-2}\
s^{-1}P<0.15%\mu B< 2.3\times 10^{-21}(\Delta m^2, \tan^2\theta)\mu\lsim 3.9\times 10^{-12} \mu_BB= 50\mu\lsim 9.0\times 10^{-13} \mu_BB= 200\mu\lsim 2.0\times 10^{-13} \mu_BB= 1000$ kG at the same
statistical significance.Comment: 13 pages, 2 figure
Hamevol1.0: a C++ code for differential equations based on Runge-Kutta algorithm. An application to matter enhanced neutrino oscillation
We present a C++ implementation of a fifth order semi-implicit Runge-Kutta
algorithm for solving Ordinary Differential Equations. This algorithm can be
used for studying many different problems and in particular it can be applied
for computing the evolution of any system whose Hamiltonian is known. We
consider in particular the problem of calculating the neutrino oscillation
probabilities in presence of matter interactions. The time performance and the
accuracy of this implementation is competitive with respect to the other
analytical and numerical techniques used in literature. The algorithm design
and the salient features of the code are presented and discussed and some
explicit examples of code application are given.Comment: 18 pages, Late
The Neutrino mass matrix after Kamland and SNO salt enhanced results
An updated analysis of all available neutrino oscillation evidence in Solar
experiments including the latest SNO ES,CC and NC data (254d live time, NaCL
enhanced efficiency) is presented. We obtain, for the fraction of active
oscillating neutrinos:
sin^2alpha=(\Phi_{NC}-\Phi_{CC})/(\Phi_{SSM}-\Phi_{CC})=0.94^{+0.0.065}_{-0.060}
nearly 20\sigma from the pure sterile oscillation case. The fraction of
oscillating sterile neutrinos cos^2\alpha \lsim 0.12 (1 sigma CL). At face
value, these results might slightly favour the existence of a small sterile
oscillating sector. In the framework of two active neutrino oscillations we
determine individual neutrino mixing parameters and their errors we obtain
Delta m^2= 7.01\pm 0.08 \times 10^{-5} eV^2, tan^2 theta=0.42^{+0.12}_{-0.07}.
The main difference with previous analysis is a better resolution in parameter
space. In particular the secondary region at larger mass differences (LMAII) is
now excluded at 95% CL. The combined analysis of solar and Kamland data
concludes that maximal mixing is not favoured at 4-5 sigma. This is not
supported by the antineutrino reactor results alone. We estimate the individual
elements of the two neutrino mass matrix, writing M^2=m^2 I+M_0^2, we obtain (1
sigma errors):
M_0^2=10^{-5} eV^2\pmatrix{
2.06^{+0.29}_{-0.31} & 3.15^{+0.29}_{-0.35} \cr
3.15^{+0.29}_{-0.35} & 4.60^{+0.56}_{-0.44} }
Solar neutrino experiments and Borexino perspectives
We present an updated analysis of all the data available about solar
neutrinos, including the charged current SNO results. The best fit of the data
is obtained in the Large Mixing Angle region, but different solutions are still
possible. We also study the perspectives of Borexino and conclude that this
experiment, with a parallel analysis of total rate and day-night asymmmetry,
should be able to discriminate between the different possible solutions.Comment: 3 pages, Latex, talk given by V. Antonelli at TAUP 2001 Conferenc
The solar neutrino puzzle: present situation and future scenarios
We present a short review of the existing evidence in favor of neutrino mass
and neutrino oscillations which come from different kinds of experiments. We
focus our attention in particular on solar neutrinos, presenting a global
updated phenomenological analysis of all the available data and we comment on
different possible future scenarios.Comment: 22 pp. Expanded version of the contribution to appear in the
Proceedings of ``Les Rencontres de Physique de la Vallee d'Aoste'', February
200
Solving the solar neutrino problem with kamLAND and BOREXINO
We analyze the expected signals of two future neutrino experiments, kamLAND
and BOREXINO. We show that with just these experiments, we will hopefully be
able to determine which of the existing solutions to the solar neutrino problem
is the real solution. We also analyze existing solar neutrino data and
determine the best-fit points in the oscillation-parameter space finding that
with the inclusion of SNO-charged current, the global-rates analysis gives a
favored LMA solution with a goodness of fit (g.o.f) of just 32.63%, whereas the
g.o.f of the SMA solution is 9.83%. Nonetheless, maximal and quasi-maximal
mixing is not favored. If we include the Superkamiokande spectrum in our \chi^2
analysis, we obtain a LMA solution with a g.o.f. of 84.38%.Comment: 4 pages, 5 figures, Talk given at 37th Rencontres de Moriond on
Electroweak Interactions and Unified Theories, Les Arcs, France, 9-16 Mar
200
After Sno and Before Kamland: Present and Future of Solar and Reactor Neutrino Physics
We present a short review of the existing evidence in favor of neutrino mass
and neutrino oscillations which come from different kinds of experiments. We
focus our attention in particular on solar neutrinos, presenting a review of
some recent analysis of all available neutrino oscillation evidence in Solar
experiments including the recent and data. We present in detail
the power of the reactor experiment KamLAND for discriminating existing
solutions to the SNP and giving accurate information on neutrino masses and
mixing angles.Comment: Expanded version of the contribution to appear in the Proceedings of
''Third Tropical Workshop on Particle Physics and Cosmology: Neutrinos,
Branes and Cosmology (Puerto Rico, August 2002)'
KamLAND, solar antineutrinos and the solar magnetic field
In this work the possibility of detecting solar electron antineutrinos
produced by a solar core magnetic field from the KamLAND recent observations is
investigated. We find a scaling of the antineutrino probability with respect to
the magnetic field profile in the sense that the same probability function can
be reproduced by any profile with a suitable peak field value. In this way the
solar electron antineutrino spectrum can be unambiguosly predicted. We use this
scaling and the negative results indicated by the KamLAND experiment to obtain
upper bounds on the solar electron antineutrino flux. We get
at 95% CL. For 90% CL this becomes
, an improvement by a factor of 3-5
with respect to existing bounds. These limits are independent of the detailed
structure of the magnetic field in the solar interior. We also derive upper
bounds on the peak field value which are uniquely determined for a fixed solar
field profile. In the most efficient antineutrino producing case, we get (95%
CL) an upper limit on the product of the neutrino magnetic moment by the solar
field MeV or for
.Comment: 15 pages. References corrected. Minor changes in the tex
Global analysis of Solar neutrino oscillation evidence including SNO and implications for Borexino
An updated analysis of all available neutrino oscillation evidence in Solar
experiments including the latest data is presented. Predictions for total
rates and day-night asymmetry in Borexino are calculated. Our analysis features
the use of exhaustive computation of the neutrino oscillation probabilities and
the use of an improved statistical minimization.
In the framework of two neutrino oscillations we conclude that the best fit
to the data is obtained in the LMA region with parameters (\Delta m^2,
\tan^2\theta) = (5.2 \times 10^{-5} \eV^2, 0.47), (,
degrees of freedom). Although less favored, solutions in the LOW and VAC
regions are still possible with a reasonable statistical significance. The best
possible solution in the SMA region gets as maximum a statistical significance
as low as .
We study the implications of these results for the prospects of Borexino and
the possibility of discriminating between the different solutions. The expected
normalized Borexino signal is 0.62 at the best fit LMA solution while the DN
asymmetry is negligible (approximately ). In the LOW region the signal
is in the range at 90% confidence level while the asymmetry is
. As a consequence, the combined Borexino measurements of the
total event rate with a error below and day-night total rate
asymmetry with a precision comparable to the one of SuperKamiokande, will have
a strong chance of distinguishing or at least strongly favoring one of the
Solar neutrino solutions provided by present data.Comment: 24 pages, 9 figures, better resolution figures are available upon
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