Bulletin of the Russian Academy of Sciences: Physics最新文献

The modern vertex detectors based on silicon sensors (tracking systems of leading experiments at the Large Hadron Collider and vertex detectors of the MPD and SPD experiments at the NICA accelerator complex) are discussed. The development of concepts for new detector systems using thin silicon pixel detectors for the precision identification of charmed hadrons decay vertices is considered. Results from developing cooling systems for large-area ultrathin silicon detector modules and studies of the properties and characteristics of silicon pixel sensors based on CMOS technology are presented in the context of detecting rare decays of hadrons containing heavy quarks.

Total cross sections of ¹⁹F(d, xt)¹⁸F (β⁺, T_1/2 =109.7 min) reaction are evaluated in the range of deuteron energies E_d = 5–16 МeV in our electronic SaBa (Sarov Base) library using mathematic tools (spline approximation) of this library. The reasons for the research were the following. The reaction ¹⁹F(d, xt)¹⁸F where tritium and ¹⁸F nuclei are produced in the same amount has been used for calibration of the tritium detection efficiency in the measurements of cross sections of tritium-producing reactions by the method of tritium accumulation into metal collectors. There was a significant contradiction in experimental data. Our new data for ¹⁹F(d, xt)¹⁸F reaction at E_d = 6.65 and 6.69 MeV and ¹⁹F(d, t₀) reaction cross section at E_d = 6.99 and 7.99 MeV appeared. We presented the refinement of the published cross sections of tritium production in reactions on lithium isotopes due to acquisition of evaluated ¹⁹F(d, xt)¹⁸F reaction cross sections.

The distributions of intermediate and slow neutrons from the outlet collimated channel of a photoneutron source are measured. A significant difference is observed between the shapes of the distributions of two groups of neutrons with energies above and below the cadmium cutoff. Whereas the distribution of intermediate neutrons has a symmetrical Gaussian shape, the distribution of slow neutrons has a complex shape. The possible causes of the difference between these shapes are discussed.

An experiment was proposed to determine the low-energy parameters of the np interaction in the nd breakup reaction at a neutron energy of 5 MeV in the RADEX neutron channel, Institute for Nuclear Research, Russian Academy of Sciences, Moscow, Russia. The energy of the virtual ¹S₀ state and the np scattering length can be obtained from the experimental dependence of the reaction yield on the relative energy of motion of the breakup neutron and proton in the kinematic region, where the np interaction in the final state is most pronounced. The reaction events were simulated, based on which the optimal conditions for the future experiment were selected.

The formation of highly excited states (E_x > 8 MeV) of neutron-rich isotopes of helium and lithium is studied in reactions of the absorption of stopped pions by ⁹Be, ^{10, 11}B, and ^{12, 14}C nuclei. Results for most nuclei are obtained in several reaction channels at once. Candidates for cluster resonances and isobaric analogue states are observed.

To study the E1 giant resonance in atomic nuclei, it is important to study the energy and emission angle distributions of fast neutrons from (γ, n)-reactions. The paper considers some features of such studies on beams of γ-quanta produced by inverse Compton scattering with small spreads of their energy, angles, transverse dimensions, duration, and polarization in these beams. It is proposed to use fast neutron spectrometers using both amplitude and time-of-flight data.

The interaction of solar neutrinos with the ¹²⁸Te and ¹³⁰Te isotopes was studied taking into account the resonance structure of charge-exchange strength functions S(E). An analysis was made of both experimental data on the strength functions S(E) obtained in the reactions (³He, t) and the strength functions S(E) calculated in the microscopic theory of finite Fermi systems. The resonance structure of the S(E) strength function was investigated, and the Gamow–Teller, analog, and pygmy resonances were identified. The capture cross sections σ(E) of solar neutrinos by the two isotopes were calculated with consideration of the resonance structure of the strength function S(E), and the influence of the resonances on the energy dependence σ(E) was analyzed. It was shown that, when calculating the cross section σ(E), the resonance structure of the strength function S(E) should be taken into account.

Equations of quantum hydrodynamics were obtained from the Schrödinger equation considering dissipation, which in the semiclassical limit are reduced to the conventional equations of hydrodynamics of an ideal fluid. An analytical solution to the hydrodynamic equations was found in the quantum shock wave approximation in one- and two-dimensional cases. The dissipative function can be found using a nonequilibrium approach. A comparison was made with experimental data to describe the emission of protons in collisions of medium-sized atomic nuclei of intermediate energies.

The possibility of searching for the effects of local spatial parity violation in strong interactions in the decay of a charged a₀ meson into a charged pion and photon was investigated. Using the Pythia Monte Carlo generator, the spectrum of invariant masses of π^±γ pairs was studied, taking into account the decay channel (a_{0}^{ pm }) → π^± + γ. An estimate was made of the minimum number of pp and Pb–Pb collision events at a significant level of the P-violating decay signal.

Spontaneous self-sustained currents on the cathodes of multiwire proportional chambers pose a problem for detectors in experiments at the Large Hadron Collider with prolonged exposure to radiation. The nature of spontaneous currents is studied using samples of a chamber cathode on which such currents occurred. A set of atomic force microscopy procedures for detecting and studying point emission centers is developed.