545 research outputs found
Effect of Coulomb collisions on time variations of the solar neutrino flux
We consider the possibility of time variations of the solar neutrino flux due
to the radial motion of the Earth and neutrino interference effects. We
calculate the time variations of the detected neutrino flux and the extent to
which they are suppressed by Coulomb collisions of the neutrino emitting
nuclei. To properly treat the collisions, it is necessary to simultaneously
include in our analysis all other significant physical decoherence effects: the
energy averaging and the averaging over the position of neutrino emission.
A simple and clear physical picture of the time dependent solar neutrino
problem is presented and qualitative coherence criteria are discussed. Exact
results for the detected neutrino flux and its time variations are obtained for
both the case of a solar neutrino line, and the case of the continuous neutrino
spectrum with a Gaussian shape of the energy response function of the neutrino
detector. We give accurate constraints on the vacuum mixing angle and the
neutrino masses required for flux time variations to not be suppressed.
Pac(s): 26.65.+t, 14.60.Pq, 96.60.JwComment: 43 pages, 8 figures, 4 appendices; changed title, MSW jump
probability formula and figure
The influence of position in overlap joints of Mg and Al alloys on microstructure and hardness of laser welds
Structure and properties of laser beam welding zone of dissimilar materials, AZ31 magnesium alloy and A5754 Aluminum alloy, are investigated. The microstructure and quality of the Mg/Al weld were studied by metallography, microhardness and optical microscopy. Differences in physical and mechanical properties of both materials, magnesium and aluminum, affect weldability and resistance of this combination, and lead to the formation of intermetallic compounds in the welded metal
A Textured Silicon Calorimetric Light Detector
We apply the standard photovoltaic technique of texturing to reduce the
reflectivity of silicon cryogenic calorimetric light detectors. In the case of
photons with random incidence angles, absorption is compatible with the
increase in surface area. For the geometrically thin detectors studied, energy
resolution from athermal phonons, dominated by position dependence, is
proportional to the surface-to-volume ratio. With the CaWO4 scintillating
crystal used as light source, the time constants of the calorimeter should be
adapted to the relatively slow light-emission times.Comment: Submitted to Journal of Applied Physic
Event-by-event fluctuations in collective quantities
We discuss an event-by-event fluctuation analysis of particle production in
heavy ion collisions. We compare different approaches to the evaluation of the
event-by-event dynamical fluctuations in quantities defined on groups of
particles, such quantities as mean transverse momentum, transverse momentum
spectra slope, strength of anisotropic flow, etc.. The direct computation of
the dynamical fluctuations and the sub-event method are discussed in more
detail. We also show how the fluctuation in different variables can be related
to each other.Comment: LaTex, 14 pages and 5 figures. 2 references adde
A novel probe of the vacuum of the lattice gluodynamics
We introduce a notion of minimal number of negative links on the lattice for
a given original configuration of SU(2) fields. Negative links correspond to a
large potential, not necessarily large action. The idea is that the minimal
number of negative links is a gauge invariant notion. To check this hypothesis
we measure correlator of two negative links, averaged over all the directions,
as function of the distance between the links. The inverse correlation length
coincides within the error bars with the lightest glueball mass.Comment: 6 pages, 2 figure
DAMA detection claim is still compatible with all other DM searches
We show that the annual modulation signal observed by DAMA can be reconciled
with all other negative results from dark matter searches with a conventional
halo model for particle masses around 5 to 9 GeV. We also show which particular
dark matter stream could produce the DAMA signal.Comment: Talk given at TAUP2005, Sept. 10-14 2005, Zaragoza (Spain). 3 pages,
4 figure
Neutrino oscillations in the early universe: How large lepton asymmetry can be generated?
The lepton asymmetry that could be generated in the early universe through
oscillations of active to sterile neutrinos is calculated (almost) analytically
for small mixing angles, sin 2\theta < 10^{-2}. It is shown that for a mass
squared difference, \delta m^2=-1 eV^2 it may rise at most by 6 orders of
magnitude from the initial ``normal'' value of 10^{-10}, since the
back-reaction from the refraction index terminates this rise while the
asymmetry is still small. Only for very large mass differences, \delta m^2
about 10^9 eV^2, the lepton asymmetry could reach a significant magnitude
exceeding 0.1.Comment: 25 pages, LaTeX (5 graphs
The -cleus experiment: A gram-scale fiducial-volume cryogenic detector for the first detection of coherent neutrino-nucleus scattering
We discuss a small-scale experiment, called -cleus, for the first
detection of coherent neutrino-nucleus scattering by probing nuclear-recoil
energies down to the 10 eV-regime. The detector consists of low-threshold
CaWO and AlO calorimeter arrays with a total mass of about 10 g and
several cryogenic veto detectors operated at millikelvin temperatures.
Realizing a fiducial volume and a multi-element target, the detector enables
active discrimination of , neutron and surface backgrounds. A first
prototype AlO device, operated above ground in a setup without
shielding, has achieved an energy threshold of eV and further
improvements are in reach. A sensitivity study for the detection of coherent
neutrino scattering at nuclear power plants shows a unique discovery potential
(5) within a measuring time of weeks. Furthermore, a site
at a thermal research reactor and the use of a radioactive neutrino source are
investigated. With this technology, real-time monitoring of nuclear power
plants is feasible.Comment: 14 pages, 19 figure
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