212 research outputs found

### Nanoparticles as a possible moderator for an ultracold neutron source

Ultracold and very cold neutrons (UCN and VCN) interact strongly with
nanoparticles due to the similarity of their wavelengths and nanoparticles
sizes. We analyze the hypothesis that this interaction can provide efficient
cooling of neutrons by ultracold nanoparticles at certain experimental
conditions, thus increasing the density of UCN by many orders of magnitude. The
present analytical and numerical description of the problem is limited to the
model of independent nanoparticles at zero temperature. Constraints of
application of this model are discussed

### Comment about constraints on nanometer-range modifications to gravity from low-energy neutron experiments

A topic of present interest is the application of experimentally observed
quantum mechanical levels of ultra-cold neutrons in the earth's gravitational
field for searching short-range modifications to gravity. A constraint on new
forces in the nanometer-range published by Nesvizhevsky and Protasov follows
from inadequate modelling of the interaction potential of a neutron with a
mirror wall. Limits by many orders of magnitude better were already derived
long ago from the consistency of experiments on the neutron-electron
interaction.Comment: three page

### A New Constraint for the Coupling of Axion-like particles to Matter via Ultra-Cold Neutron Gravitational Experiments

We present a new constraint for the axion monopole-dipole coupling in the
range of 1 micrometer to a few millimeters, previously unavailable for
experimental study. The constraint was obtained using our recent results on the
observation of neutron quantum states in the Earth's gravitational field. We
exploit the ultimate sensitivity of ultra-cold neutrons (UCN) in the lowest
gravitational states above a material surface to any additional interaction
between the UCN and the matter, if the characteristic interaction range is
within the mentioned domain. In particular, we find that the upper limit for
the axion monopole-dipole coupling constant is (g_p g_s)/(\hbar c)<2 x 10^{-15}
for the axion mass in the ``promising'' axion mass region of ~1 meV.Comment: 5 pages 3 figure

### Experimental constraints for additional short-range forces from neutron experiments

We present preliminary results on sensitivity of experiments with slow
neutrons to constrain additional forces in a wide distance range: from
picometers to micrometers. In the sub-nanometer range, available data on
lengths of neutron scattering at nuclei provide the most competitive
constraint. We show that it can be improved significantly in a dedicated
measurement of asymmetry of neutron scattering at noble gases. In the
micrometer range, we present sensitivity of the future GRANIT experiment.
Further analysis will be presented in following publications.Comment: presented in "les rencontres de Moriond" 2007 conferenc

### Can we observe the gravitational quantum states of Positronium?

In this paper we consider the feasibility of observing the gravitational
quantum states of positronium. The proposed scheme employs the flow-throw
technique used for the first observation of this effect with neutrons.
Collimation and Stark deceleration of Rydberg positronium atoms allow to select
the required velocity class. If this experiment could be realized with
positronium it would lead to a determination of g for this matter-antimatter
system at the few % level. As discussed in this contribution, most of the
required techniques are currently available but important milestones have to be
demonstrated experimentally before such an experiment could become reality.
Those are: the efficient focusing of a bunched positron beam, Stark
deceleration of Rydberg positronium and its subsequent excitation into states
with large angular momentum. We provide an estimate of the efficiencies we
expect for these steps and assuming those could be confirmed we calculate the
signal rate.Comment: 12 pages, 1 figure, contribution to the GRANIT 2014 workshop: Quantum
gravitationnal spectroscopy with ultra-cold system

### 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

### Development of a high sensitivity torsional balance for the study of the Casimir force in the 1-10 micrometer range

We discuss a proposal to measure the Casimir force in the parallel plate
configuration in the $1-10\mu$m range via a high-sensitivity torsional balance.
This will allow to measure the thermal contribution to the Casimir force
therefore discriminating between the various approaches discussed so far. The
accurate control of the Casimir force in this range of distances is also
required to improve the limits to the existence of non-Newtonian forces in the
micrometer range predicted by unification models of fundamental interactions.Comment: 10 pages, 2 figure

- …