Data on the production of antiprotons at an angle of 40° in the laboratory system in collisions of 50-GeV protons with C, Al, Cu, and W nuclear targets have been obtained in the SPIN experiment (IHEP, Protvino, Russia). Invariant cross sections have been measured at transverse momenta up to pT ≈ 2.6 GeV/c. The an-alysis of the momentum spectra has shown that multinucleon (multiquark) configurations inside a nucleus are involved in the production of antiprotons.

Abstract—The SPIN experiment is carried out with the aim of studying inclusive production of charged particles with high transverse momenta in hard proton−nucleus and nucleus−nucleus interactions. A single-arm narrow-aperture spectrometer is used in the study. The uniqueness of the experiment is in the high intensity of the proton (1012−1013 protons/s) and ion (of the order of 5 × 109 ions/s) beams ejected from the U-70 accelerator, which makes it possible to measure inclusive cross sections varying by seven orders of magnitude. The SPIN setup is able to detect particles with momenta in a kinematic domain of nucleon−nucleon interactions as well as beyond its limits. The spectrometer equipment and the features of the measurement procedure are described.

This paper presents the results of the development and implementation of fast wire scanners based on servomotors with a resolver and standard control electronics at a speed of 16 m/s at the U-70 IHEP accelerator. Profilometers are designed to measure the density distribution of proton and carbon beams in the horizontal and vertical planes. The motors of scanners are controlled by servocontrollers through the Copley Motion Explorer CME2 software shell. The beam profile is recorded using scintillation detectors. The beam profile and dimensions were processed using a program developed in the LabVIEW environment. To determine the beam revolution frequency, the fast Fourier transform and the integration of the measured input signal over a given number of beam revolutions are used. The beam parameters are given for a wide range of particle intensities and energies.

An Erratum to this paper has been published: https://doi.org/10.1134/S0020441223010293

The first data on production of cumulative K+, K– mesons and antiprotons with high transverse momenta outgoing at the lab angle of 40 degrees in proton–nucleus interactions are presented. Inclusive cross sections are studied for the C, Al, Cu, and W targets at the proton beam momentum of 50 GeV/c. The investigated range of transverse momenta from 0.6 to 2.7 GeV/c is partially beyond the proton–nucleon kinematics. The $$\bar {p}$$ /π– and K+/K– ratios are identical for all investigated targets within the experimental errors. The data indicate a noticeable contribution of multiparton processes to production of cumulative mesons and antiprotons. The investigations have been performed in the SPIN experiment at the U-70 accelerator.

Data on the production of positively charged particles emitted at an angle of 40 $${}^{\circ}$$ (in the laboratory frame) with transverse momenta of up to 2.7 GeV $$/c$$ in the interaction of 50-GeV $$/c$$ protons with carbon, aluminum, copper, and tungsten nuclear targets are presented. Particular attention is given to studying the production of light nuclear fragments, such as deuterons ( $$d$$ ) and tritons ( $$t$$ ). An analysis of data on $$d$$ and $$t$$ particles gives grounds to state that these fragments arise via a local mechanism of their direct knockout from nuclei. The results were obtained in the SPIN experiment at the Institute for High Energy Physics (IHEP, Protvino).

The results of numerical simulation of a turbulent flow in a flat channel with periodic inclined ribs by the RANS method are presented. The Reynolds number, calculated from the rib height and the superficial velocity, is Re = 12600. The obtained data are analyzed in order to determine the influence of the inclination angle on heat transfer. It is shown that the optimal angle of inclination, at which the average heat transfer in the channel is maximum, is 60°.

In view of the successful experience in the generation of pion and kaon secondary beams using a focusing crystal, it has been proposed to build at the U-70 accelerator a new-type channel of secondary particles that does not consume electric power. It has been shown experimentally that an extraction septum magnet can be protected from radiation by applying a multistrip crystal device through current septum shadowing by the crystal that involves the bulk reflection regime for the deflection of particles. The listed applications of crystals are novel in the world practice with accelerators.

The result of numerical simulation of a turbulent flow in a flat channel with a periodic transverse rib by the RANS and LES methods is presented. The Reynolds number, calculated from the rib height and the superficial velocity, is Re = 12600. The data obtained as a result of the study demonstrate the influence of the modeling method and the turbulence model on the quality of heat transfer prediction. The optimal model for this type of problems is presented.

Abstractthe paper considers aerodynamic and thermal interference of separated flows between two square prisms arranged at a short distance from each other. It is shown how relative positions of the square prisms affect the specific phenomena caused by the airflow interactions. This work is the experimental study of aerodynamic and thermal interference effects on two square prisms or building models depending on their relative positions. A strong difference is shown between aerodynamic and thermal interferences observed in the airflow behind two tandem models. The thermal interference effect turns to be rather conservative as compared to the aerodynamic. Using the interference parameters one can easily analyze the extreme values of the pressure and thermal flows interfering with the building models depending on many factors, including relative model positions.

The paper presents the research results of the distribution of the local and integral pressure coefficients over the sides of the square prisms arranged in tandem and experiencing the airflow. The correlation is shown between the obtained airflow patterns and the pressure coefficient distribution; the dependences are obtained between the building arrangement and the distribution of the pressure coefficients; the phenomena caused by the airflow interaction are described in this paper.

The process of interaction of two separated flows of various scales in a tube with a sudden expansion is investigated. It has been determined that an additional turbulizing element in the form of a small diaphragm leads to dramatic changes in the structure of the recirculation zone in the channel behind a step, shift in the flow attachment point, and, accordingly, redistribution of heat and mass transfer coefficients. The approach of a mini-turbulizer to the separation point increases the size of recirculation zone and heat transfer intensity. An increase in the height of a mini-turbulizer affects similarly the characteristics of a separated flow.

The first data on the yield of the lightest nuclear fragments (protons p, deuterons d, and tritons t) with high transverse momenta pT at an angle of 40° in the laboratory reference frame from nuclear targets bombarded by 50-GeV/c protons and 20A-GeV/c carbon nuclei obtained in the SPIN experiment (IHEP, Protvino, Russia) have been reported. It has been shown that the pA and CA data can be described within a common scaling approach, which possibly indicates that the mechanism of formation of high-pT nuclear fragments is common for these reactions.

The results of numerical calculation by the RANS and LES methods of turbulent separated flow in a flat channel with a back-facing step are presented. The calculation was carried out for Reynolds number Re = 5000, determined by the average mass velocity and the step height. The effect of vortex generators in the form of a transverse rib on the heat transfer intensity has been studied, and the data obtained are compared with experiment.

The paper considers the dynamic and thermal interference effects on two neighbouring building models in the form of square prisms arranged at a short distance from each other. It is shown how relative positions of the models affect the specific phenomena caused by the airflow interactions.