V. V. Nesvizhevsky

Study of the neutron quantum states in the gravity field

We have studied neutron quantum states in the potential well formed by the earths 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.

Neutron scattering and extra-short-range interactions

The available data on neutron scattering were reviewed to constrain a hypothetical new short-range interaction. We show that these constraints are several orders of magnitude better than those usually cited in the range between 1 pm and 5 nm. This distance range occupies an intermediate space between collider searches for strongly coupled heavy bosons and searches for new weak macroscopic forces. We emphasize the reliability of the neutron constraints insofar as they provide several independent strategies. We have identified a promising way to improve them.

Constraint on the coupling of axionlike particles to matter via an ultracold neutron gravitational experiment

We present a new constraint for the axion monopole-dipole coupling in the range of

Observation of a triple correlation in ternary fission: is time reversal invariance violated?

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Quantum motion of a neutron in a waveguide in the gravitational field

\char21{}a few mm, previously unavailable for experimental study. The constraint was obtained using our recent results on the observation of neutron quantum states in the Earths gravitational field. We exploit the ultimate sensitivity of ultracold 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.

Search for quantum states of the neutron in a gravitational field: gravitational levels

Abstract In ternary fission, besides the two main fission fragments, a third (usually light) charged particle is emitted. A triple correlation has been studied involving the momenta for a specific fission fragment p f , the momenta of the ternary particle p t and the spin of the polarized cold neutron inducing fission σ . The correlation observable B= σ ·[ p f × p t ] reverses sign upon time reversal and thus a non-vanishing value for the expectation value 〈 B 〉 could possibly be due to TRI being violated. However, final-state interactions or specific properties of the emission mechanism for ternary particles could equally well lead to a non-zero 〈 B 〉 with TRI being perfectly conserved. The reaction chosen was 233 U(n,f). An unexpectedly large correlation was observed. From the raw data the value for 〈 B 〉 is 〈 B 〉=−(0.78±0.02)×10 −3 with the sign corresponding to light fragments. Corrections for neutron polarization, geometric efficiency, resolution of detectors and background increase this figure by a factor of (1.5±0.3).

A quantum mechanical description of the experiment on the observation of gravitationally bound states

We study theoretically the quantum motion of a neutron in a horizontal waveguide in the gravitational field of the Earth. The waveguide in question is equipped with a mirror below and a rough surface 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 determined mainly by the potential well formed by the gravitational field of the Earth and the mirror. The formalism developed for quantum motion in an absorbing waveguide is applied to the description of the recent experiment on the observation of the quantum states of neutrons in the Earths gravitational field.

A method to measure the resonance transitions between the gravitationally bound quantum states of neutrons in the GRANIT spectrometer

Abstract The neutron could occupy quantum stationary states if it is trapped between the Earths gravitational field on one side and the Fermi quasi-potential of a mirror on the other side. The quantum states cause a strong variation in neutron density, both for separate energy levels and for a mixture of low-energy states. The use of a position sensitive UCN (ultracold neutron) detector allows simultaneous measurement of the position probability density distribution in the total range of interest and increases significantly the statistics, making possible such an experiment. In this article we describe a specially developed neutron spectrometer and a method of measurement of such quantum states.

The reflection of very cold neutrons from diamond powder nanoparticles

Quantum states in the earth’s gravitational field have been observed, with ultra-cold neutrons falling under gravity. The experimental results can be described by the quantum mechanical scattering model presented here. We also discuss other geometries of the experimental setup, which correspond to the absence or the reversion of gravity. Since our quantum mechanical model quantitatively describes, particularly, the experimentally realized situation of reversed gravity, we can practically rule out alternative explanations of the quantum states, in terms of pure confinement effects.

Mechanism of small variations in energy of ultracold neutrons interacting with a surface

We present a method to measure the resonance transitions between the gravitationally bound quantum states of neutrons in the GRANIT spectrometer. The purpose of GRANIT is to improve the accuracy of measurement of the quantum states parameters by several orders of magnitude, taking advantage of long storage of ultracold neutrons at specular trajectories. The transitions could be excited using a periodic spatial variation of a magnetic field gradient. If the frequency of such a perturbation (in the frame of a moving neutron) coincides with a resonance frequency defined by the energy difference of two quantum states, the transition probability will sharply increase. The GRANIT experiment is motivated by searches for short-range interactions (in particular spin-dependent interactions), by studying the interaction of a quantum system with a gravitational field, by searches for extensions of the Standard model, by the unique possibility to check the equivalence principle for an object in a quantum state and by studying various quantum optics phenomena.