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.

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 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 yields of cumulative protons and π ± mesons emitted at a laboratory angle of 40° from carbon and heavier nuclear targets irradiated by a proton beam from the U70 accelerator (Institute for High Energy Physics, Protvino) have been studied in the SPIN experiment. It has been found that the effect of the target nucleus on the yield of particles with large transverse momenta is weakened.

A two-arm spectrometer FLUKTON for investigations in the field of relativistic nuclear physics at U70 energies is proposed to be constructed on base of the existing detector SPIN (IHEP, Protvino). The main objective is to obtain new data on clusters of cold superdense nuclear matter. Interaction of a high intensity proton beam with nuclear targets and an ion beam with liquid hydrogen and nuclear targets will be studied.

Formation of the d and t cumulative light nuclear fragments emitted from the nucleus with large transverse momenta at an angle of 35° in the laboratory frame is investigated. The data on collisions of 50-GeV protons with the C, Al, Cu, and W nuclei are collected using the extracted proton beam of the IHEP accelerator and the SPIN detector. The results indicate that the dominant contribution to formation of nuclear fragments comes from the local process of direct knockout from the nucleus.

The first data on the production of cumulative π+, p, and light nuclear fragments d and t emitted from a nucleus with a high transverse momentum at an angle of 35° in the laboratory system have been reported. The data have been obtained at the SPIN setup at the interaction of a 50-GeV proton beam extracted from the U-70 accelerator (IHEP, Protvino) with C, Al, Cu, and W nuclei.

The transverse polarization of $\Lambda$ hyperons was measured in inclusive quasireal photoproduction for various target nuclei ranging from hydrogen to xenon. The data were obtained by the HERMES experiment at HERA using the 27.6 GeV lepton beam and nuclear gas targets internal to the lepton storage ring. The polarization observed is positive for light target nuclei and is compatible with zero for krypton and xenon.

The data on production of cumulative particles in the high transverse momenta domain (up to ~ 3.5 GeV/c) in proton-nucleus interactions are presented for the first time. An indication on the local character of particle production in the cumulative domain is obtained. The observed strong dependence of the particle production cross section on the atomic mass of the target does not fit the A - dependence obtained in the pre-cumulative and cumulative domains for low transverse momenta at constant part of the exponent. The experiment was performed at U70 (IHEP) with the extracted 50 GeV/c proton beam.

Momentum spectra of cumulative particles in the region of high transverse momenta (P T ) in pA → h + + X reactions were obtained for the first time. The experiment in which this was done was performed at the SPIN setup (Institute for High Energy Physics, Protvino) in a beam of 50-GeV protons interacting with C, Al, Cu, and W nuclei. Positively charged particles were detected at a laboratory angle of 35° and in the transverse-momentum range between 0.6 and 3.7 GeV/c. A strong dependence of the particle-production cross section on the atomic number was observed. A comparison with the results of calculations based on the HIJING and UrQMD models was performed in the subcumulative region.

Впервые получены импульсные спектры кумулятивных частиц в области больших в реакции . Эксперимент выполнен на установке СПИН (ИФВЭ, Протвино) на пучке протонов с энергией 50 ГэВ, взаимодействующих с ядрами C, Al, Cu и W. Положительно заряженные частицы регистрировались под углом 35 в л.с. и в диапазоне поперечных импульсов от 0.6 до 3.7 ГэВ/ . Наблюдена сильная зависимость сечения рождения частиц от атомного числа. В предкумулятивной области проведено сравнение с расчетами по моделям HIJING и UrQMD.