Physics of Particles and Nuclei最新文献

Abstract

At present, new compact highly granular neutron detector is being developed for the BM@N experiment. This detector will be used to identify neutrons, to measure their energies using time-of-flight method, neutron yields and azimuthal flow of neutrons in heavy-ion collisions at beam energies up to 4 A GeV. Application of machine learning techniques and preliminary results of neutron identification and energy reconstruction are discussed. First predictions of the anisotropic flow of neutrons using the DCM-QGSM-SMM model of heavy-ion collisions are shown.

Abstract

Particles produced in noncentral heavy-ion collisions are mostly twisted (vortex). They are created in electromagnetic and strong interactions. Particles emitted in strong interactions are twisted if initial interacting partons are in twisted states and are untwisted in the opposite case. A vorticity of nuclear matter plays an important role for the production of twisted particles.

Abstract

In this paper we study the cumulative proton production in (p + C) interactions at (4.2) and 10 ({text{GeV/}}c). Cumulative protons in comparison with the noncumulative ones are produced at large values of the variable ({{n}_{{text{c}}}} > 1) and in this region the energy of cumulative protons also increases. The experimentally obtained values of the cumulative proton energies are compared with the estimations got by the formula of the uncertainty principle. It has been shown that the energy of cumulative protons obtained by using the formula of the uncertainty principle is in agreement with the experimental results.

Abstract

Two particles correlations are a useful tool to study the event structures of particle production in multiparticle events of particle interactions. Structures of events are caused by various mechanisms of particle production and could be separated with some global observables of the events. Examining event structures with these methods can give new insight into the nature of these interactions.

The (np to np{{pi }^{ + }}{{pi }^{ - }}) reaction is investigated at the incident neutron momenta ({{P}_{0}}) = 3.83 and 5.20 GeV/c. Contributions of different diagrams to the reaction cross section are calculated at the momenta from the threshold to 12 GeV/c. It is shown that the main contributions to the (np to np{{pi }^{ + }}{{pi }^{ - }}) reaction at momenta above ({{P}_{0}}) > 3 GeV/c come from diagrams of the reggeized (pi )-meson exchange model (OPER).To study spin effects, the reaction (np to np{{Delta }^{{ + + }}}{{Delta }^{ - }}) was separated. It is shown that description of the spin density matrix [({{rho }_{{ij}}})] requires taking into account the ρ-meson exchange diagram. The reaction (np to np{{rho }^{0}}) is separated by background subtraction method. The investigation has shown that ({{rho }^{0}})-meson production is described by suspended diagrams of the OPER model.

Arrays of minibeams of protons and ¹²C in tissue-like media were modeled with Geant4 toolkit. A set of beam energies was used in simulations to provide a Spead-out Bragg peak (SOBP) extended by 6 cm in depth for protons as well as for ¹²C. In both cases, beams of 0.3 or 0.5 mm FWHM were arranged at the entrance to a water phantom either on a rectangular or an hexagonal grid to compare two kinds of projectiles and different minibeam patterns. Differential and cumulative dose-volume histograms (DVH) were calculated and compared for protons and ¹²C as dose uniformity metrics. A uniform dose distribution was easily achieved with protons due to an enhanced lateral scattering of these projectiles in comparison to ¹²C. The cumulative DVHs calculated for 0.3 or 0.5 mm minibeams almost coincide in the target volume, but diverge for different grid patterns. In contrast, cumulative entry DVHs were found similar for both grid patterns, but different for 0.3 and 0.5 mm minibeams.

In this research, we analyze transverse momentum cumulants of different orders (({{K}_{n}})) for charged inclusive hadrons produced in ({text{Bi}} + {text{Bi}}) collisions using the UrQMD-3.4 model events. The analysis is carried out in two ways: with the standard method, in which the study is carried out over the entire rapidity interval, and also with the sub-event method, which suppresses the influence of short-range correlations. Dependencies of second-, third-, and fourth-order cumulants on collision energy were obtained. The paper also provides a comparison of (p + p) and ({text{Bi}} + {text{Bi}}) collisions that indicated the simultaneous saturation for both systems at (sqrt {{{s}_{{NN}}}} approx 5) GeV.

The hadron light-by-light scattering contribution to the superfine splitting of the muonium ground state is calculated. The quasi-potential of muon and electron interaction is expressed in terms of the form factor of transition of two virtual photons to a meson. The contributions of pseudoscalar, pseudovector, scalar, and tensor mesons are considered.

Abstract

To measure the characteristics of quark and gluon jets in hadron–hadron collisions, two samples of jets are used. Given the large statistics of jets at the LHC, the two-sample method requires taking into account the following corrections: (1) use of measured fractions of quark and gluon jets instead of the model ones, (2) amendment for the contribution of jets with an unidentified type, (3) taking into account the dependence of the distributions of quark and gluon jets on the conditions for jet sample selections. The paper presents an improved two-sample method that takes into account these corrections.

Abstract

Measuring the spectra of light hadrons is one of the priority tasks of the MPD experiment at NICA. The assessment of the efficiency of recording differential transverse momentum spectra of production of identified hadrons in the MPD detector, which are produced in collisions of bismuth nuclei at an energy of (sqrt {{{s}_{{NN}}}} = 9.2) GeV, is presented.