39 research outputs found
Centrifugal quantum states of neutrons
We propose a method for observation of the quasi-stationary states of
neutrons, localized near the curved mirror surface. The bounding effective well
is formed by the centrifugal potential and the mirror Fermi-potential. This
phenomenon is an example of an exactly solvable "quantum bouncer" problem that
could be studied experimentally. It could provide a promising tool for studying
fundamental neutron-matter interactions, as well as quantum neutron optics and
surface physics effects. We develop formalism, which describes quantitatively
the neutron motion near the mirror surface. The effects of mirror roughness are
taken into account.Comment: 13 pages, 10 figure
Quantum motion of a neutron in a wave-guide in the gravitational field
We study theoretically the quantum motion of a neutron in a horizontal
wave-guide in the gravitational field of the Earth. The wave-guide in question
is equipped with a mirror below and a rough absorber above. We show that such a
system acts as a quantum filter, i.e. it effectively absorbs quantum states
with sufficiently high transversal energy but transmits low-energy states. The
states transmitted are mainly determined by the potential well formed by the
gravitational field of the Earth and the mirror. The formalism developed for
quantum motion in an absorbing wave-guide is applied to the description of the
recent experiment on the observation of the quantum states of neutrons in the
Earth's gravitational field
Ramsey's Method of Separated Oscillating Fields and its Application to Gravitationally Induced Quantum Phaseshifts
We propose to apply Ramsey's method of separated oscillating fields to the
spectroscopy of the quantum states in the gravity potential above a vertical
mirror. This method allows a precise measurement of quantum mechanical
phaseshifts of a Schr\"odinger wave packet bouncing off a hard surface in the
gravitational field of the earth. Measurements with ultra-cold neutrons will
offer a sensitivity to Newton's law or hypothetical short-ranged interactions,
which is about 21 orders of magnitude below the energy scale of
electromagnetism.Comment: 7 pages, 6 figure
Post-Newtonian equation for the energy levels of a Dirac particle in a static metric
We study first the Hamiltonian operator H corresponding to the Fock-Weyl
extension of the Dirac equation to gravitation. When searching for stationary
solutions to this equation, in a static metric, we show that just one invariant
Hermitian product appears natural. In the case of a space-isotropic metric, H
is Hermitian for that product. Then we investigate the asymptotic
post-Newtonian approximation of the stationary Schroedinger equation associated
with H, for a slow particle in a weak-field static metric. We rewrite the
expanded equations as one equation for a two-component spinor field. This
equation contains just the non-relativistic Schroedinger equation in the
gravity potential, plus correction terms. Those "correction" terms are of the
same order in the small parameter as the "main" terms, but are numerically
negligible in the case of ultra-cold neutrons in the Earth's gravity.Comment: 12pt LaTeX, 17 pages. v2: version accepted for publication in
Phys.Rev.D: comments on scalar product changed, using a recent paper;
discussion of PN expansions simplified (no change of units any more);
numerical estimates for ultra-cold neutrons in the Earth's gravit
Large-scale Samples Irradiation Facility at the IBR-2 Reactor in Dubna
The irradiation facility at the beam line no.3 of the IBR-2 reactor of the Frank Laboratory for Neutron Physics is described. The facility is aimed at irradiation studies of various objects with area up to 800 cm both at cryogenic and ambient temperatures. The energy spectra of neutrons are reconstructed by the method of threshold detector activation. The neutron fluence and dose rates are measured by means of alanine and thermoluminescent dosimeters. The boron carbide and lead filters or converter provide beams of different ratio of doses induced by neutrons and photons. For the lead filter, the flux of fast neutrons with energy more than 0.1 MeV is \fln and the neutron dose is about 96\% of the total radiation dose. For the converter, the dose rate is 500 Gy h which is about 85\% of the total dose. The radiation hardness tests of GaAs electronics and materials for the ATLAS detector to be put into operation at the Large Hadron Collider (LHC) have been performed successfully at this facility
Study of the neutron quantum states in the gravity field
We have studied neutron quantum states in the potential well formed by the
earth's gravitational field and a horizontal mirror. The estimated
characteristic sizes of the neutron wave functions in the two lowest quantum
states correspond to expectations with an experimental accuracy. A
position-sensitive neutron detector with an extra-high spatial resolution of ~2
microns was developed and tested for this particular experiment, to be used to
measure the spatial density distribution in a standing neutron wave above a
mirror for a set of some of the lowest quantum states. The present experiment
can be used to set an upper limit for an additional short-range fundamental
force. We studied methodological uncertainties as well as the feasibility of
improving further the accuracy of this experiment
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
Ultracold neutrons, quantum effects of gravity and the Weak Equivalence Principle
We consider an extension of the recent experiment with ultracold neutrons and
the quantization of its vertical motion in order to test the Weak Equivalence
Principle. We show that an improvement on the energy resolution of the
experiment may allow to establish a modest limit to the Weak Equivalence
Principle and on the gravitational screening constant. We also discuss the
influence of a possible new interaction of Nature.Comment: Revtex4, 4 pages. Discussion on the equivalence principle altered.
Bound is improve
The neutron and its role in cosmology and particle physics
Experiments with cold and ultracold neutrons have reached a level of
precision such that problems far beyond the scale of the present Standard Model
of particle physics become accessible to experimental investigation. Due to the
close links between particle physics and cosmology, these studies also permit a
deep look into the very first instances of our universe. First addressed in
this article, both in theory and experiment, is the problem of baryogenesis ...
The question how baryogenesis could have happened is open to experimental
tests, and it turns out that this problem can be curbed by the very stringent
limits on an electric dipole moment of the neutron, a quantity that also has
deep implications for particle physics. Then we discuss the recent spectacular
observation of neutron quantization in the earth's gravitational field and of
resonance transitions between such gravitational energy states. These
measurements, together with new evaluations of neutron scattering data, set new
constraints on deviations from Newton's gravitational law at the picometer
scale. Such deviations are predicted in modern theories with extra-dimensions
that propose unification of the Planck scale with the scale of the Standard
Model ... Another main topic is the weak-interaction parameters in various
fields of physics and astrophysics that must all be derived from measured
neutron decay data. Up to now, about 10 different neutron decay observables
have been measured, much more than needed in the electroweak Standard Model.
This allows various precise tests for new physics beyond the Standard Model,
competing with or surpassing similar tests at high-energy. The review ends with
a discussion of neutron and nuclear data required in the synthesis of the
elements during the "first three minutes" and later on in stellar
nucleosynthesis.Comment: 91 pages, 30 figures, accepted by Reviews of Modern Physic