932 research outputs found
Large mixing angle solution to the solar neutrino problem and random matter density perturbations
There are reasons to believe that mechanisms exist in the solar interior
which lead to random density perturbations in the resonant region of the Large
Mixing Angle solution to the solar neutrino problem. We find that, in the
presence of these density perturbations, the best fit point in the
(sin^2(2\theta), Delta_m^2) parameter space moves to smaller values, compared
with the values obtained for the standard LMA solution. Combining solar data
with KamLAND results, we find a new compatibility region, which we call
VERY-LOW LMA, where sin^2(2\theta) ~ 0.6 and Delta_m^2~2e-5 eV^2, for random
density fluctuations of order 5% < \xi< 8%. We argue that such values of
density fluctuations are still allowed by helioseismological observations at
small scales of order 10 - 1000 km deep inside the solar core.Comment: References and discussion added, with some small numerical
corrections implemente
Recovery and radiation corrections and time constants of several sizes of shielded and unshielded thermocouple probes for measuring gas temperature
Performance characteristics were experimentally determined for several sizes of a shielded and unshielded thermocouple probe design. The probes are of swaged construction and were made of type K wire with a stainless steel sheath and shield and MgO insulation. The wire sizes ranged from 0.03- to 1.02-mm diameter for the unshielded design and from 0.16- to 0.81-mm diameter for the shielded design. The probes were tested through a Mach number range of 0.2 to 0.9, through a temperature range of room ambient to 1420 K, and through a total-pressure range of 0.03 to 0.2.2 MPa (0.3 to 22 atm). Tables and graphs are presented to aid in selecting a particular type and size. Recovery corrections, radiation corrections, and time constants were determined
Quantum Dissipation in a Neutrino System Propagating in Vacuum and in Matter
Considering the neutrino state like an open quantum system, we analyze its
propagation in vacuum or in matter. After defining what can be called
decoherence and relaxation effects, we show that in general the probabilities
in vacuum and in constant matter can be written in a similar way, which is not
an obvious result in this approach. From this result, we analyze the situation
where neutrinos evolution satisfies the adiabatic limit and use this formalim
to study solar neutrinos. We show that the decoherence effect may not be
bounded by the solar neutrino data and review some results in the literature.
We discuss the current results where solar neutrinos were used to put bounds on
decoherence effects through a model-dependent approach. We conclude explaining
how and why this models are not general and we reinterpret these constraints.Comment: new version: title was changend and was added a table. To appear at
Nucl. Physic.
Effects of magnetohydrodynamics matter density fluctuations on the solar neutrino resonant spin-flavor precession
Taking into account the stringent limits from helioseismology observations on
possible matter density fluctuations described by magnetohydrodynamics theory,
we find the corresponding time variations of solar neutrino survival
probability due to the resonant spin-flavor precession phenomenon with
amplitude of order O(10%). We discuss the physics potential of high statistics
real time experiments, like as Superkamiokande, to observe the effects of such
magnetohydrodynamics fluctuations on their data. We conclude that these
observations could be thought as a test of the resonant spin-flavor precession
solution to the solar neutrino anomaly.Comment: 16 pages, 3 figure
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