G. A. Petrov

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.

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

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).

Rotation of the compound nucleus 236U∗ in the fission reaction 235U( n , f ) induced by cold polarised neutrons

A model for ternary fission is discussed in which a third particle (α-particle) is emitted due to non-adiabatic change of the nuclear potential at neck rapture. An expression for energy and angular distribution of α-particles is proposed. It is shown that an interaction between spin of fissioning system and orbital momentum of α-particle (spin-orbit interaction in the final state) results in recently observed asymmetry of α-particle emission, which can be formally related to T-odd correlation. No strong dependence of the asymmetry on the angle of α-particle emission with respect to the fission axis is predicted by the model in accordance with the experimental data.

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

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.

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

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.

Angular correlations in ternary fission induced by polarized neutrons

Ternary fission induced by cold polarized neutrons was studied for the two isotopes 233U and 235U at the Institut Laue-Langevin in Grenoble, France. In particular two types of angular correlations between the spin of the incoming neutrons and the emission directions of both, the fission fragments (FF) and the ternary particles (TP), were investigated. For FF and TP detectors facing the target at right angles to the neutron beam, first, for longitudinally polarized neutrons a triple correlation between spin and the emission of outgoing particles was explored and, second, for transversally polarized neutrons parity violating asymmetries in the emission of FFs and TPs were analyzed. Nonzero expectation values for the triple correlation were oberserved in the present experiments for the first time.

Left-right asymmetry of the angular distribution of long-range alpha particles from ternary 235U fission induced by cold polarized neutrons

Left–Right Asymmetry of the Angular Distribution of Long-Range Alpha Particles from Ternary 235U Fission Induced by Cold Polarized Neutrons* G. V. Danilyan1), A. M. Fedorov1), A. M. Gagarski2), F. Goennenwein3), P. Jesinger3), J. von Kalben4), A. Koetzle3), Ye. I. Korobkina5), I. T. Krasnoshchekova2), M. Mutterer4), V. V. Nesvizhevsky6), S. R. Neumaier4), Yu. B. Novozhilov1), V. S. Pavlov1), G. A. Petrov2),

The comparison of binary- and ternary-fission configurations close to the instant of scission

A new way to bring into comparison the binary- and ternary-fission configurations is proposed. The method is founded on recently discovered ROT effect. The angle of fission axis deflection from its initial orientation at the moment of scission comes into existence as a result of dividing system rotation and carries information about fissioning nucleus deformation. The comparison of proper angles for binary and ternary fission can be used to estimate the difference in the rupture configurations.

Can Time Reversal be tested in ternary fission

Ternary fission of 233U and 235U induced by cold polarized neutrons has been investigated. Several correlations between neutron spin and the momenta of fission fragments and ternary particles were analyzed. These correlations are probing time reversal invariance, parity non-conservation and left-right asymmetries. Results for all three correlations from the reaction 233U(n,f) are presented. Especially the outcome in the searches for time reversal correlations and left-right asymmetries is unexpected. A huge effect observed formally as a violation of time reversal is most probably simulated by specific properties of the emission mechanism for ternary particles.