88 research outputs found
Effects of non-standard neutrino interactions on MSW-LMA solution to the solar neutrino problem
We show that the non-standard neutrino interactions can play a role as
sub-leading effect on the solar neutrino oscillations. We observe that very
small flavor universality violations of order of 0.1-0.2 G_F is sufficient to
induce two phenomena: suppression of the eletronic neutrino earth regeneration
and a shift of the resonance layer in the sun. We obtain these phenomena even
in the absence of any flavor changing interactions. We discuss their
consequences and confront with a global analysis of solar+KamLAND results. We
conclude that a new compatibility region in the Delta m^2 x tan^2\theta, which
we call very low Large Mixing Angle region, is found for Delta m^2 ~ 1e-5 eV^2
and tan^2\theta= 0.45.Comment: references added, small changes in text, some changes in predictions
of KamLAND future sensitivity to NSNI parameter
Toward precision measurements in solar neutrinos
Solar neutrino physics enters a stage of precision measurements. In this
connection we present a precise analytic description of the neutrino conversion
in the context of LMA MSW solution of the solar neutrino problem. Using the
adiabatic perturbation theory we derive an analytic formula for the
survival probability which takes into account the non-adiabatic corrections and
the regeneration effect inside the Earth. The probability is averaged over the
neutrino production region. We find that the non-adiabatic corrections are of
the order . Using the formula for the Earth regeneration
effect we discuss features of the zenith angle dependence of the flux.
In particular, we show that effects of small structures at the surface of the
Earth can be important.Comment: 26 pages, 6 figures. Version to appear in Nucl. Phys.
Solving Solar Neutrino Puzzle via LMA MSW Conversion
We analyze the existing solar neutrino experiment data and show the allowed
regions. The result from SNO's salt phase itself restricts quite a lot the
allowed region's area. Reactor neutrinos play an important role in determining
oscillation parameters. KamLAND gives decisive conclusion on the solution to
the solar neutrino puzzle, in particular, the spectral distortion in the 766.3
Ty KamLAND data gives another new improvement in the constraint of solar
MSW-LMA solutions. We confirm that at 99.73% C.L. the high-LMA solution is
excluded.Comment: 6 eps figure
Solar Neutrinos Before and After KamLAND
We use the recently reported KamLAND measurements on oscillations of reactor
anti-neutrinos, together with the data of previously reported solar neutrino
experiments, to show that: (1) the total 8B neutrino flux emitted by the Sun is
1.00(1.0 \pm 0.06) of the standard solar model (BP00) predicted flux, (2) the
KamLAND measurements reduce the area of the globally allowed oscillation
regions that must be explored in model fitting by six orders of magnitude in
the Delta m^2-tan^2 theta plane, (3) LMA is now the unique oscillation solution
to a CL of 4.7sigma, (4) maximal mixing is disfavored at 3.1 sigma, (5)
active-sterile admixtures are constrained to sin^2 eta<0.13 at 1 sigma, (6) the
observed ^8B flux that is in the form of sterile neutrinos is
0.00^{+0.09}_{-0.00} (1 sigma), of the standard solar model (BP00) predicted
flux, and (7) non-standard solar models that were invented to completely avoid
solar neutrino oscillations are excluded by KamLAND plus solar at 7.9 sigma .
We also refine quantitative predictions for future 7Be and p-p solar neutrino
experiments.Comment: Published version, includes editorial improvement
Minimal archi-texture for neutrino mass matrices
The origin of the observed masses and mixing angles of quarks and leptons is
one of imperative subjects in and beyond the standard model. Toward a deeper
understanding of flavor structure, we investigate in this paper the minimality
of fermion mass (Yukawa) matrices in unified theory. That is, the simplest
matrix form is explored in light of the current experimental data for quarks
and leptons, including the recent measurements of quark CP violation and
neutrino oscillations. Two types of neutrino mass schemes are particularly
analyzed; (i) Majorana masses of left-handed neutrinos with unspecified
mechanism and (ii) Dirac and Majorana masses introducing three right-handed
neutrinos. As a result, new classes of neutrino mass matrices are found to be
consistent to the low-energy experimental data and high-energy unification
hypothesis. For distinctive phenomenological implications of the minimal
fermion mass textures, we discuss flavor-violating decay of charged leptons,
the baryon asymmetry of the universe via thermal leptogenesis, neutrino-less
double beta decay, and low-energy leptonic CP violation.Comment: 37 pages, 6 figure
Constraining neutrino oscillation parameters with current solar and atmospheric data
We analyze the impact of recent solar, atmospheric and reactor data in the
determination of the neutrino oscillation parameters, taking into account that
both the solar nu_e and the atmospheric nu_mu may convert to a mixture of
active and sterile neutrinos. We use the most recent global solar neutrino
data, including the 1496-day Super-K neutrino data sample, and we investigate
in detail the impact of the SNO neutral current, spectral and day/night data by
performing also an analysis using only the charged current rate from SNO. The
implications of the first 145.1 days of KamLAND data on the determination of
the solar neutrino parameters are also discussed in detail. We confirm the
clear preference of solar+reactor data for the pure active LMA-MSW solution of
the solar neutrino problem, and obtain that the LOW, VAC, SMA and Just-So^2
solutions are disfavored with a Delta_chi^2 = 22, 22, 36, 44, respectively.
Furthermore, we find that the global solar data constrains the admixture of a
sterile neutrino to be less than 43% at 99% CL. By performing an improved fit
of the atmospheric data, we also update the corresponding regions of
oscillation parameters. We find that the recent atmospheric Super-K (1489-day)
and MACRO data have a strong impact on constraining a sterile component in
atmospheric oscillations: if the nu_mu is restricted to the atmospheric mass
states only a sterile admixture of 16% is allowed at 99% CL, while a bound of
35% is obtained in the unconstrained case. Pure sterile oscillations are
disfavored with a Delta_chi^2 = 34.6 compared to the pure active case.Comment: 28 pages, LaTeX file using RevTEX4, 12 figures and 3 tables included.
Improved version including the new KamLAND dat
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