877 research outputs found
Low-temperature electrical discharge through solid xenon
The uniform self-sustained electrical discharge through solid xenon has been realized and studied. The
multiplication of electrons proceeds in the noble gas above the xenon crystal interface whereas a positive
feedback is realized at the account of multiple exciton formation by excess electrons drifted through the
crystal: molecular excitons emit VUV photons which knocked out secondary electrons from photosensitive
cathode. The discharge was stimulated by short electrical spark along the sample axes. The discharge electrical
properties as well as the spectra of solid xenon electroluminescence in UV and visible have been studied.
Electric discharge in solid xenon was proved to be an effective source of UV radiation and a convenient tool
to study the processes involving excitons and electrons in solid xenon at high pressures
High-frequency hopping conductivity in the quantum Hall effect regime: Acoustical studies
The high-frequency conductivity of Si delta-doped GaAs/AlGaAs
heterostructures is studied in the integer quantum Hall effect (QHE) regime,
using acoustic methods. Both the real and the imaginary parts of the complex
conductivity are determined from the experimentally observed magnetic field and
temperature dependences of the velocity and the attenuation of a surface
acoustic wave. It is demonstrated that in the structures studied the mechanism
of low-temperature conductance near the QHE plateau centers is hopping. It is
also shown that at magnetic fields corresponding to filling factors 2 and 4,
the doped Si delta- layer efficiently shunts the conductance in the
two-dimensional electron gas (2DEG) channel. A method to separate the two
contributions to the real part of the conductivity is developed, and the
localization length in the 2DEG channel is estimated.Comment: 8pages, 9 figure
Constraints On Radiative Neutrino Mass Models From Oscillation Data
The three neutrino Zee model and its extension including three active and one
sterile species are studied in the light of new neutrino oscillation data. We
obtain analytical relations for the mixing angle in solar oscillations in terms
of neutrino mass squared differences. For the four neutrino case, we obtain the
result , which can accommodate both the large
and small mixing scenarios. We show that within this framework, while both the
SMA-MSW and the LMA-MSW solutions can easily be accommodated, it would be
difficult to reconcile the LOW-QVO solutions. We also comment on the
active-sterile admixture within phenomenologically viable textures.Comment: The paper has been substantially rewritten, especially in Section IV,
though the basic results are unchanged. Some new references and an appendix
have been adde
SN1987A and the Status of Oscillation Solutions to the Solar Neutrino Problem (including an appendix discussing the NC and day/night data from SNO)
We study neutrino oscillations and the level-crossing probability PLZ in
power-law potential profiles A(r)\propto r^n. We give local and global
adiabaticity conditions valid for all mixing angles theta and discuss different
representations for PLZ. For the 1/r^3 profile typical of supernova envelopes
we compare our analytical to numerical results and to earlier approximations
used in the literature. We then perform a combined likelihood analysis of the
observed SN1987A neutrino signal and of the latest solar neutrino data,
including the recent SNO CC measurement. We find that, unless all relevant
supernova parameters (released binding energy, \bar\nu_e and \bar\nu_{\mu,\tau}
temperatures) are near their lowest values found in simulations, the status of
large mixing type solutions deteriorates considerably compared to fits using
only solar data. This is sufficient to rule out the vacuum-type solutions for
most reasonable choices of astrophysics parameters. The LOW solution may still
be acceptable, but becomes worse than the SMA-MSW solution which may, in some
cases, be the best combined solution. On the other hand the LMA-MSW solution
can easily survive as the best overall solution, although its size is generally
reduced when compared to fits to the solar data only.Comment: 31 pages, 32 eps figures; 5 pages, 5 eps figures addendum in v2,
discussing the recent SNO NC data and changes in SN paramete
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