1,815 research outputs found
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
Model Independent Information On Solar Neutrino Oscillations
We present the results of a Bayesian analysis of solar neutrino data in terms
of nu_e->nu_{mu,tau} oscillations, independent from the Standard Solar Model
predictions for the solar neutrino fluxes. We show that such a model
independent analysis allows to constraint the values of the neutrino mixing
parameters in limited regions around the usual SMA, LMA, LOW and VO regions.
Furthermore, there is a strong indication in favor of large neutrino mixing and
large values of Delta m^2 (LMA region). We calculate also the allowed ranges of
the neutrino fluxes and we show that they are in good agreement with the
Standard Solar Model prediction. In particular, the ratio of the 8B flux with
its Standard Solar Model prediction is constrained in the interval [0.45,1.42]
with 99.73% probability. Finally, we show that the hypothesis of no neutrino
oscillations is strongly disfavored in a model independent way with respect to
the hypothesis of neutrino oscillations.Comment: 40 pages, 20 figures. Added references and improved figure
Habitat fragmentation causes rapid genetic differentiation and homogenization in natural plant populations – A case study in Leymus chinensis
The effects of habitat fragmentations on the forage grass Leymus thinness (Trin.) Tzvel, which has high genetic diversity in northeast China were investigated. Four natural populations of the same ecotype (Grey-green leaf, GGL), namely, BT, ZL, CL and CC (named after location) were collected from different abiotic growing conditions. The CC population has become isolated in a park inside a city by tall buildings though geologically close to CL. Amplified fragment length polymorphism (AFLP) selected primer combinations were highly efficient in revealing the inter-clonal and inter-populational genetic variation in this species. The genetic diversity indices were higher in BT (H = 0.2305) and ZL (0.2467) populations and the lowest in CC (0.1674) population. Cluster analysis showed that the CC population was becoming isolated from the rest with the least gene flow from BT (1.51) as compared from BT to ZL (2.24). Lowest polymorphism was observed in CC (52.31%) as compared to CL (57.69%), BT (70.00%) and ZL (70.38%); this showed a tendency towards homogenization probably due to increased selfing, and due to reduced gene flow apparently caused by city buildings. These results were supported by multiple statistical analyses including Mantel’s test, PCOORDA and AMOVA. Genetic enrichment and epigenetic variation studies can be included in habitat fragmentation analysis and its implications in inducing homogenization and susceptibility in natural plant populations
The sign of the day-night asymmetry for solar neutrinos
A qualitative understanding of the day-night asymmetry for solar neutrinos is
provided. The greater night flux in nu_e is seen to be a consequence of the
fact that the matter effect in the sun and that in the earth have the same
sign. It is shown in the adiabatic approximation for the sun that for all
values of the mixing angle theta_V between 0 and pi/2, the night flux of
neutrinos is greater than the day flux. Only for small values of theta_V where
the adiabatic approximation badly fails does the sign of the day-night
asymmetry reverse.Comment: 3 pages, 3 figures, typos corrected and references adde
Chiral corrections to the axial charges of the octet baryons from quenched QCD
We calculate one-loop correction to the axial charges of the octet baryons
using quenched chiral perturbation theory, in order to understand chiral
behavior of the axial charges in quenched approximation to quantum
chromodynamics (QCD). In contrast to regular behavior of the full QCD chiral
perturbation theory result, , we find
that the quenched chiral perturbation theory result,
, is
singular in the chiral limit.Comment: standard LaTeX, 16 pages, 4 epsf figure
Modeling realistic Earth matter density for CP violation in neutrino oscillation
We examine the effect of a more realistic Earth matter density model which
takes into account of the local density variations along the baseline of a
possi ble 2100 km very long baseline neutrino oscillation experiment. Its
influence to the measurement of CP violation is investigated and a comparison
with the commonly used global density models made. Significant differences are
found in the comparison of the results of the different density models.Comment: 16 pages, 8 figure
Long-Baseline Study of the Leading Neutrino Oscillation at a Neutrino Factory
Within the framework of three-flavor neutrino oscillations, we consider the
physics potential of \nu_e --> \nu_\mu appearance and \nu_\mu --> \nu_\mu
survival measurements at a neutrino factory for a leading oscillation scale
\delta m^2 ~ 3.5 \times 10^{-3} eV^2. Event rates are evaluated versus baseline
and stored muon energy, and optimal values discussed. Over a sizeable region of
oscillation parameter space, matter effects would enable the sign of \delta m^2
to be determined from a comparison of \nu_e --> \nu_\mu with \bar\nu_e -->
\bar\nu_\mu event rates and energy distributions. It is important, therefore,
that both positive and negative muons can be stored in the ring. Measurements
of the \nu_\mu --> \nu_\mu survival spectrum could determine the magnitude of
\delta m^2 and the leading oscillation amplitude with a precision of O(1%--2%).Comment: 33 pages, single-spaced Revtex, uses epsf.sty, 14 postscript figures.
Added references, expanded conclusions, improved figs. 13 and 14. Version to
be published in Phys. Rev.
Nanofriction mechanisms derived from the dependence of friction on load and sliding velocity from air to UHV on hydrophilic silicon
This paper examines friction as a function of the sliding velocity and
applied normal load from air to UHV in a scanning force microscope (SFM)
experiment in which a sharp silicon tip slides against a flat Si(100) sample.
Under ambient conditions, both surfaces are covered by a native oxide, which is
hydrophilic. During pump-down in the vacuum chamber housing the SFM, the
behavior of friction as a function of the applied normal load and the sliding
velocity undergoes a change. By analyzing these changes it is possible to
identify three distinct friction regimes with corresponding contact properties:
(a) friction dominated by the additional normal forces induced by capillarity
due to the presence of thick water films, (b) higher drag force from ordering
effects present in thin water layers and (c) low friction due to direct
solid-solid contact for the sample with the counterbody. Depending on
environmental conditions and the applied normal load, all three mechanisms may
be present at one time. Their individual contributions can be identified by
investigating the dependence of friction on the applied normal load as well as
on the sliding velocity in different pressure regimes, thus providing
information about nanoscale friction mechanisms
Neutrino masses: From fantasy to facts
Theory suggests the existence of neutrino masses, but little more. Facts are
coming close to reveal our fantasy: solar and atmospheric neutrino data
strongly indicate the need for neutrino conversions, while LSND provides an
intriguing hint. The simplest ways to reconcile these data in terms of neutrino
oscillations invoke a light sterile neutrino in addition to the three active
ones. Out of the four neutrinos, two are maximally-mixed and lie at the LSND
scale, while the others are at the solar mass scale. These schemes can be
distinguished at neutral-current-sensitive solar & atmospheric neutrino
experiments. I discuss the simplest theoretical scenarios, where the lightness
of the sterile neutrino, the nearly maximal atmospheric neutrino mixing, and
the generation of & all follow
naturally from the assumed lepton-number symmetry and its breaking. Although
the most likely interpretation of the present data is in terms of
neutrino-mass-induced oscillations, one still has room for alternative
explanations, such as flavour changing neutrino interactions, with no need for
neutrino mass or mixing. Such flavour violating transitions arise in theories
with strictly massless neutrinos, and may lead to other sizeable flavour
non-conservation effects, such as , conversion in
nuclei, unaccompanied by neutrino-less double beta decay.Comment: 33 pages, latex, 16 figures. Invited Talk at Ioannina Conference,
Symmetries in Intermediate High Energy Physics and its Applications, Oct.
1998, to be published by Springer Tracts in Modern Physics. Festschrift in
Honour of John Vergados' 60th Birthda
Wavy stripes and squares in zero P number convection
A simple model to explain numerically observed behaviour of chaotically
varying stripes and square patterns in zero Prandtl number convection in
Boussinesq fluid is presented. The nonlinear interaction of mutually
perpendicular sets of wavy rolls, via higher mode, may lead to a competition
between the two sets of wavy rolls. The appearance of square patterns is due to
the secondary forward Hopf bifurcation of a set of wavy rolls.Comment: 8 pages and 3 figures, late
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