[en] A possible way of setting up a direct experiment to measure the neutron-neutron scattering length is discussed. The experiment consists of the detection of neutrons scattering by each other in a collimated beam of thermal neutrons from a reactor. Some results of a Monte Carlo simulation of the experiment are given, and the characteristics of this method are discussed and compared with an earlier proposal. 4 refs., 5 figs

[en] An experimental situation with the experimental test of the weak equivalence principle for a neutron is considered. A method that substantially (up to ∼ 10^-6) improves the test precision is suggested. This method uses the thin-film Fabry-Perot interferometer and the precise time-of-flight spectrometry for ultracold neutrons. 28 refs., 3 figs

[en] The hypothesis of possible production, with probability 10%, in the decay of ²¹⁴Bi, of a new (e⁺ e^- e^-) particle, with mass approx-gt 1.5 MeV/c² and lifetime ∼ 10^-10 sec, decaying into an electron and a γray, has been tested experimentally. An upper limit on the probability of production of such a particle in the decay of ²¹⁴Bi was found (with confidence level 90%) to be 10^-3 by measuring (in coincidence with γrays) the spectrum of electrons from the possible decay of these particles in flight. 13 refs., 3 figs., 1 tab

[en] The present status of the observations made in experiments at the GSI, Darmstadt of narrow positron lines and electron-positron pairs in the range of effective masses 1.6-1.8 MeV/c ² in collisions of very heavy ions at energies below the Coulomb barrier is reviewed. The results of experiments at low and high energies looking for a similar phenomenon in other processes are presented. Theoretical attempts to explain the open-quotes Darmstadt effectclose quotes are considered

[en] Small ultracold neutron cooling and heating during long storage in traps has ben observed in recent experiments. It is shown that neutron quasielastic due to the diffusive motion of hydrogen at the surface of adsorbed hydrogenous contaminations may be a possible reason for the spread in the energy of ultracold neutrons during long storage in traps

[en] The results are presented of the search for the anomalous transmission of ultracold neutrons (UCN) through beryllium (thickness ∼ 0.14 mm), stainless steel (0.05 and 0.015 mm) and copper (0.01 and 0.018 mm) foils. This anomalous transmission is considered as one of the possible reasons for UCN disappearance from beryllium bottles. No transmission was found in measurements at the level 10^-7 except for the case of copper foils which we attribute to the admixture in the UCN flux of neutrons with the energies higher than the boundary energy for copper