101 research outputs found
A proposal of a UCN experiment to check an earthquake waves model
Elastic waves with transverse polarization inside incidence plane can create
longitudinal surface wave (LSW) after reflection from a free surface. At a
critical incidence angle this LSW accumulates energy density, which can be
orders of magnitude higher than energy density of the incident transverse wave.
A specially arranged vessel for storage of ultracold neutrons (UCN) can be used
to verify this effect.Comment: 8 pages 3 figures added a paragraph on vibrations along surface at
critical angl
Analytical Calculation of the Neutrons Spectrum for Direct Measurement of N-N Scattering at Pulsed Reactor Yaguar
Analytical calculation of a single neutron detector counts per YAGUAR reactor
pulse is presented and comparison with coincidence scheme is given.Comment: 10 pages, 3 figure
Entanglement production with multimode Bose-Einstein condensates in optical lattices
Deep optical lattices are considered, in each site of which there are many
Bose-condensed atoms. By the resonant modulation of trapping potentials it is
possible to transfer a macroscopic portion of atoms to the collective nonlinear
states corresponding to topological coherent modes. Entanglement can be
generated between these modes. By varying the resonant modulating field it is
possible to effectively regulate entanglement production in this multimode
multitrap system of Bose condensates.Comment: Latex file, 16 pages, 7 figure
Neutron-antineutron Oscillations in the Trapping Box
We have reexamined the problem of oscillations for ultra-cold
neutrons (UCN) confined within a trap. We have shown that the growth of the
component with time is to a decent accuracy given by where is the mixing parameter,
sec in the neutron propagation time between subsequent collisions
with the trap walls. Possible corrections to this law and open questions are
discussed.Comment: 11 pages, LaTeX2
Coherent Schwinger Interaction from Darboux Transformation
The exactly solvable scalar-tensor potential of the four-component Dirac
equation has been obtained by the Darboux transformation method. The
constructed potential has been interpreted in terms of nucleon-nucleon and
Schwinger interactions of neutral particles with lattice sites during their
channeling Hamiltonians of a Schwinger type is obtained by means of the Darboux
transformation chain. The analitic structure of the Lyapunov function of
periodic continuation for each of the Hamiltonians of the family is considered.Comment: 12 pages, Latex, six figures; six sections, one figure adde
Neutron lifetime measurements using gravitationally trapped ultracold neutrons
Our experiment using gravitationally trapped ultracold neutrons (UCN) to
measure the neutron lifetime is reviewed. Ultracold neutrons were trapped in a
material bottle covered with perfluoropolyether. The neutron lifetime was
deduced from comparison of UCN losses in the traps with different
surface-to-volume ratios. The precise value of the neutron lifetime is of
fundamental importance to particle physics and cosmology. In this experiment,
the UCN storage time is brought closer to the neutron lifetime than in any
experiments before:the probability of UCN losses from the trap was only 1% of
that for neutron beta decay. The neutron lifetime
obtained,878.5+/-0.7stat+/-0.3sys s, is the most accurate experimental
measurement to date.Comment: 38 pages, 19 figures,changed conten
Surface roughness effect on ultracold neutron interaction with a wall and implications for computer simulations
We review the diffuse scattering and the loss coefficient in ultracold
neutron reflection from slightly rough surfaces, report a surprising reduction
in loss coefficient due to roughness, and discuss the possibility of transition
from quantum treatment to ray optics. The results are used in a computer
simulation of neutron storage in a recent neutron lifetime experiment that
re-ported a large discrepancy of neutron lifetime with the current particle
data value. Our partial re-analysis suggests the possibility of systematic
effects that were not included in this publication.Comment: 39 pages, 9 figures; additional calculations include
UCN anomalous losses and the UCN capture cross-section on material defects
Experimental data shows anomalously large Ultra Cold Neutrons (UCN)
reflection losses and that the process of UCN reflection is not completely
coherent. UCN anomalous losses under reflection cannot be explained in the
context of neutron optics calculations. UCN losses by means of incoherent
scattering on material defects are considered and cross-section values
calculated. The UCN capture cross-section on material defects is enhanced by a
factor of 10^4 due to localization of UCN around defects. This phenomenon can
explain anomalous losses of UCN.Comment: 13 pages, 4 figure
Study of levitating nanoparticles using ultracold neutrons
Physical adsorption of atoms, molecules and clusters on surface is known. It
is linked to many phenomena in physics, chemistry, and biology. Usually the
studies of adsorption are limited to the particle sizes of up to ~10^2-10^3
atoms. Following a general formalism, we apply it to even larger objects and
discover qualitatively new phenomena. A large particle is bound to surface in a
deep and broad potential well formed by van der Waals/ Casimir-Polder forces.
The well depth is significantly larger than the characteristic thermal energy.
Nanoparticles in high-excited bound states form two-dimensional gas of objects
quasi-freely traveling along surface. A particularly interesting prediction is
small-energy-transfer scattering of UCN on solid/ liquid surfaces covered by
such levitating nanoparticles/ nano-droplets. The change in UCN energy is due
to the Doppler shift induced by UCN collisions with nanoparticles; the energy
change is about as small as the UCN initial energy. We compare theoretical
estimations of our model to all relevant existing data and state that they
agree quite well. As our theoretical formalism provides robust predictions and
the experimental data are rather precise, we conclude that the recently
discovered intriguing phenomenon of small heating of UCN in traps is due to
their collisions with such levitating nanoparticles. Moreover, this new
phenomenon might be relevant to the striking contradiction between results of
the neutron lifetime measurements with smallest reported uncertainties as it
might cause major false effects in these experiments; thus it affects
fundamental conclusions concerning precision checks of unitarity of the
Cabibbo-Kobayashi-Maskawa matrix, cosmology, astrophysics. Dedicated
measurements of UCN up-scattering on specially prepared surfaces and
nanoparticles levitating above them might provide a unique method to study
surface potentials.Comment: 20 pages, 12 figure
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