46 research outputs found
Seasonal Variations of the 7Be Solar Neutrino Flux
Measuring the 7Be solar neutrino flux is crucial towards solving the solar
neutrino puzzle. The Borexino experiment, and possibly the KamLAND experiment,
will be capable of studying the 7Be neutrinos in the near future. We discuss
(1) how the seasonal variation of the Borexino and KamLAND data can be used to
measure the 7Be solar neutrino flux in a background independent way and (2) how
anomalous seasonal variations might be used to discover vacuum neutrino
oscillations, independent of the solar model and the measurement of the
background. In particular, we find that, after three years of Borexino or
KamLAND running, vacuum neutrino oscillations can be either established or
excluded for almost all values of (sin^2 2 theta, Delta m^2) preferred by the
Homestake, GALLEX, SAGE, and Super-Kamiokande data. We also discuss how well
seasonal variations of the data can be used to measure (sin^2 2 theta, Delta
m^2) in the case of vacuum oscillations.Comment: 39 pages, 13 figures, uses psfig. Now the impact of the MSW effect on
vacuum oscillations taken into account. Conclusions unchanged. References
adde
Solar neutrinos and grand unification
We consider the Grand Unification (GU) scenario for neutrino masses which is
based on the see-saw mechanism with the mass of the heaviest right handed (RH)
neutrino at the GU-scale: , and on the quark-lepton
symmetry for fermions from the third generation. The scenario predicts for the
light neutrinos: eV and eV (in the case of a linear mass hierarchy of the RH neutrinos
or/and in presence of the Planck scale suppressed non-renormalizable
operators). It also predicts large mixing: . In this scenario the solar neutrinos
() undergo both the \nue \nutau resonance conversion in the
Sun and substantial \nue \numu vacuum oscillations on the way from the
Sun to the Earth. The interplay of both effects enlarges the range of neutrino
parameters which solve the -problem. In particular, mixing angle can be as small as the corresponding quark mixing:
. The scenario predicts
peculiar (oscillatory) distortion of the boron neutrino energy spectrum and
seasonal variations of signals. Manifestations of these effects in the
Super-Kamiokande and SNO experiments are studied.Comment: 36 pages, LaTeX, includes 14 figures, revised and expande
Quantum dynamics in strong fluctuating fields
A large number of multifaceted quantum transport processes in molecular
systems and physical nanosystems can be treated in terms of quantum relaxation
processes which couple to one or several fluctuating environments. A thermal
equilibrium environment can conveniently be modelled by a thermal bath of
harmonic oscillators. An archetype situation provides a two-state dissipative
quantum dynamics, commonly known under the label of a spin-boson dynamics. An
interesting and nontrivial physical situation emerges, however, when the
quantum dynamics evolves far away from thermal equilibrium. This occurs, for
example, when a charge transferring medium possesses nonequilibrium degrees of
freedom, or when a strong time-dependent control field is applied externally.
Accordingly, certain parameters of underlying quantum subsystem acquire
stochastic character. Herein, we review the general theoretical framework which
is based on the method of projector operators, yielding the quantum master
equations for systems that are exposed to strong external fields. This allows
one to investigate on a common basis the influence of nonequilibrium
fluctuations and periodic electrical fields on quantum transport processes.
Most importantly, such strong fluctuating fields induce a whole variety of
nonlinear and nonequilibrium phenomena. A characteristic feature of such
dynamics is the absence of thermal (quantum) detailed balance.Comment: review article, Advances in Physics (2005), in pres
Global Analysis with SNO: Toward the Solution of the Solar Neutrino Problem
We perform a global analysis of the latest solar neutrino data including the
SNO result on the CC-event rate. This result further favors the LMA solution of
the solar neutrino problem. The best fit values of parameters we find are:
\Delta m^2 = (4.8 - 5.0)10^{-5} eV^2, tan^2 \theta = 0.35 - 0.38, f_B = 1.08 -
1.12, and f_{hep} = 1 - 4. With respect to this best fit the LOW solution is
accepted at 90% C.L.. The Vacuum oscillation solution with \Delta m^2 = 1.4
10^{-10} eV^2, gives good fit of the data provided that the boron neutrino flux
is substantially smaller than the SSM flux (f_B \sim 0.5). The SMA solution is
accepted only at 3\sigma level. We find that vacuum oscillations to sterile
neutrino, VAC(sterile), with f_B \sim 0.5 also give rather good global fit of
the data. All other sterile solutions are strongly disfavored. We check the
quality of the fit by constructing the pull-off diagrams of observables.
Predictions for the day-night asymmetry, spectrum distortion and NC/CC ratio at
SNO are calculated. In the best fit points of the global solutions we find:
A_{DN}^{CC} \approx (7 - 8)% for LMA, \sim 3% for LOW, and (2 - 3)% for SMA. It
will be difficult to see the distortion of the spectrum expected for LMA as
well as LOW solutions. However, future SNO spectral data can significantly
affect the VAC and SMA solutions. We also calculate expectations for the
BOREXINO rate.Comment: 35 pages, latex, 9 figures; results of analysis slightly changed due
to different treatment of the hep neutrino flux; predictions for NC/CC ratio
and Borexino rate adde
Common Hierarchical Lepton Mass Textures for Atmospheric and Solar Neutrino Oscillations
We propose and study a common hierarchical mass texture for both charged
lepton and neutrino sectors. The texture gives rise to a large
mixing. Also it leads to the small angle MSW
effect solution for solar neutrino data. It naturally gives a small
oscillation relevant to the CHOOZ result in
certain mass limits.Comment: 11 pages, no figures, late
Global Three-Neutrino Vacuum Oscillation fits to the Solar and Atmospheric Anomalies
We determine the three-neutrino mixing and mass parameters that are allowed
by the solar and atmospheric neutrino data when vacuum oscillations are
responsible for both phenomena. The global fit does not appreciably change the
allowed regions for the parameters obtained from effective two-neutrino fits.
We discuss how measurements of the solar electron energy spectrum below 6.5 GeV
in Super-Kamiokande and seasonal variations in the Super-Kamiokande, Ga,
and BOREXINO experiments can distinguish the different solar vacuum solutions.Comment: Revtex, 31 pages, uses epsf.sty, 14 postscript figures. Version to be
published in Phys. Rev.
The Hemopoietic Stem Cell Niche Versus the Microenvironment of the Multiple Myeloma-Tumor Initiating Cell
Multiple myeloma cells are reminiscent of hemopoietic stem cells in their strict dependence upon the bone marrow microenvironment. However, from all other points of view, multiple myeloma cells differ markedly from stem cells. The cells possess a mature phenotype and secrete antibodies, and have thus made the whole journey to maturity, while maintaining a tumor phenotype. Not much credence was given to the possibility that the bulk of plasma-like multiple myeloma tumor cells is generated from tumor-initiating cells. Although interleukin-6 is a major contributor to the formation of the tumor’s microenvironment in multiple myeloma, it is not a major factor within hemopoietic stem cell niches. The bone marrow niche for myeloma cells includes the activity of inflammatory cytokines released through osteoclastogenesis. These permit maintenance of myeloma cells within the bone marrow. In contrast, osteoclastogenesis constitutes a signal that drives hemopoietic stem cells away from their bone marrow niches. The properties of the bone marrow microenvironment, which supports myeloma cell maintenance and proliferation, is therefore markedly different from the characteristics of the hemopoietic stem cell niche. Thus, multiple myeloma presents an example of a hemopoietic tumor microenvironment that does not resemble the corresponding stem cell renewal niche