Physics of Particles and Nuclei最新文献

The 60-ton cylindrical electromagnetic calorimeter of the MPD facility of the NICA project with a diameter of 3.45 m and a length of 6 m under construction is assembled from 50 half-sectors, each containing 768 “Shashlik” towers of different sizes and different spatial orientations. The paper proposes methods for calibrating half-sector towers using cosmic muons passing both along and across the axes of the towers. The results of testing these methods on the first manufactured half-sector are presented.

The paper presents a technique for calculating the decay form factors of a pseudoscalar pion, ({{pi }^{ pm }} to {{ell }^{ pm }}{{nu }_{{{{ell }^{ pm }}}}}gamma ), in an approach based on the composite quark model and the point form of Poincare-invariant quantum mechanics (PiQM in what follows). It is shown that consideration of the electromagnetic structure of constituent (u) and (d) quarks using the virtuality parameter leads to values of the axial ({{F}_{{text{A}}}}) and vector ({{F}_{{text{V}}}}) form factors that are consistent with current experimental data. Based on the calculation results, a self-consistent model is proposed describing the electroweak decays ({{pi }^{ pm }} to {{ell }^{ pm }}{{nu }_{{{{ell }^{ pm }}}}}) and ({{pi }^{ pm }} to {{ell }^{ pm }}{{nu }_{{{{ell }^{ pm }}}}}gamma ) of a light pseudoscalar pion.

This paper discusses the matrix method, which is an approach to the estimation of the background induced by the misidentification of a hadronic jet as a photon. To obtain the number of such background events the method uses the efficiencies of real/fake photons to pass the identification criteria. Selected events are categorized based on the photon isolation. The number of ({text{jet}} to gamma ) background events in the region of interest can be estimated using the auxiliary region. The proposed method does not require any optimization procedure in order for its correct application, which is an advantage over other commonly used approaches.

We present a brief overview of fractional analytic QCD.

Abstract

A heavy-ion collision experiment has a wide range of physical observables that are dependent on the initial geometry. Centrality is used to describe the initial geometry of collisions in experiments. Spectator fragments, or pieces of the colliding nuclei that were not involved in the collision, can be used to determine centrality. In this work, we discuss how processes of spectator fragmentation may impact the centrality determination procedure. These effects are demonstrated using the DCM-QGSM-SMM model, which realistically reproduces fragmentation processes, and the published results of the NA61/SHINE experiment.

Abstract

Fractals, random, and AMPT AuAu events are analyzed using the (SePaC) method. Transverse momenta ({{p}_{{text{t}}}}) of negatively charged particles are examined in five centrality classes. Fractal AuAu events with independent partition are shown to feature several narrow peaks in the spectrum of fractal dimensions ({{D}_{{text{F}}}}) and a separated group of leading particles in transverse momentum ({{p}_{{text{t}}}}) for all events and to satisfy the criteria that describe statistical properties. Remaining events exhibit exponential behavior of the ({{p}_{{text{t}}}}) spectrum. Fractal AuAu events with dependent partition have a broad peak in the ({{D}_{{text{F}}}}) spectrum and are suppressed by selection criteria.

We report on newest results in ({{k}_{{text{T}}}})-factorization approach for (ep)-processes. We describe HERA data on longitudinal structure function measurements as well as on associated prompt photon and jet photoproduction. The calculations include first application of the new LLM-2022 transverse momentum dependent gluon distribution developed by the authors. The study includes also the first implementation of parton showers for photoproduction processes in ({{k}_{{text{T}}}})-factorization. The data are described well with the simulations. The (ep)-processes are included to the new version of Monte-Carlo generator pegasus.

Abstract

We investigate the quasiclassical and quantum radiation accompanying creation of the electron-hole plasma (EHP) in the graphene under action of the strong electromagnetic field (Sauter–Schwinger effect). The quasiclassical radiation of the plasma currents by virtue of massless of the theory with a high degree of precision reproduces the spectrum of the external field whereas the spectrum of the quantum radiation is sufficiently wide. It allows to carry out experimental verification of the theory.

Abstract

The development and production of relevant products in the microelectronics industry in Russia have been crucially dependent on foreign technologies for several decades. In the current scenario, the need to find a way to gain sanction-free access to cutting-edge electronic components from modern technological processes required for the experiments in the NICA complex seems obvious. The MPD-ITS project aims to achieve this goal by organizing a consortium of interested institutes in Russia and China coordinated by the VBLHEP JINR (Dubna) in Russia and the CCNU (Wuhan) in the People’s Republic of China representing several Chinese institutions for the joint development and production of state-of-the-art Monolithic Active Pixel Sensors (MAPS) for fundamental and applied science experiments, including ASICs-based front-end electronics from the GBTx family which is the standard in modern High Energy Physics experiments for its fast duplex data flow between the high radiation level experimental area and the remote on-line servers, thus making these technologies freely accessible to China and Russia. These chips will be the focus of collaborative research and development for the construction of the NICA setups to be used in fundamental and applied science projects i.e. the MPD Inner Tracking System, and a prototype of a clinical tomograph for the particle Computer Tomography (pCT) for the ARIADNA project. Here we present our current achievements and future developments.

Abstract

Gell-Mann–Low functions can be calculated by means of perturbation theory and expressed as truncated series in powers of asymptotically small coupling parameters. However, it is necessary to know there behavior at finite values of the parameter and, moreover, their behavior at asymptotically large coupling parameters is also important. The problem of extrapolation of weak-coupling expansions to the region of finite and even infinite coupling parameters is considered. A method is suggested allowing for such an extrapolation. The basics of the method are described and illustrations of its applications are given for the examples where its accuracy and convergence can be checked. It is shown that in some cases the method allows for the exact reconstruction of the whole functions from their weak-coupling asymptotic expansions. Gell-Mann–Low functions in multicomponent field theory, quantum electrodynamics, and quantum chromodynamics are extrapolated to their strong-coupling limits.