Physics of Particles and Nuclei Letters最新文献

Scalar diquark model of proton improved by parton intrinsic transverse momentum in hadrons is able to describe the strong scaling violation in proton production large transverse momentum ({{p}_{ bot }}) within perturbative QCD in a wide energy range: (sqrt s = 11.5,,{text{GeV}}) at U70 (NRC KI—IHEP, Protvino), (sqrt s = 23.4,,{text{GeV}}) at Tevatron (FNAL, Chicago), and (sqrt s = 62,,{text{GeV}}) at ISR (CERN, Geneva) is presented. Estimates for the production of tetraquark exotic states formed by scalar diquarks in the SPD experiment at the forthcoming NICA collider (JINR, Dubna) have been obtained.

The entropy of microscopic configurations accompanied hadron production in nucleus-nucleus collisions is discussed. It is expressed, in the z-scaling approach, via the momentum fractions of colliding particles and scattered constituents fragmented to produced particles, the structural and fragmentation fractal dimensions, the multiplicity density of negative particles and model parameter interpreted as a specific heat of nuclear medium. Principle of the maximal entropy with taking into account momentum conservation law for constituent sub-process is used to determine the momentum fractions and model parameters by requiring self-similarity of the function ψ in dependence on dimensionless variable z. Statistical interpretation of the entropy in terms ensemble of fractal configurations of internal structures of colliding hadrons and fractal configurations corresponding to a fragmentation process in the final state is given. A conservation law of a quantum cumulativity and quantization of fractal dimensions are formulated.

As is known from the classical theory of complex angular momenta, along with the Regge poles in the complex j-plane should be cuts that are generated by the poles. In QCD, the cuts are generated by exchanges of the Reggeized gluons, whose properties are strikingly different from the properties of Reggeons in classical theory, which leads to peculiarities of the formation of the cuts. The talk is devoted to the discussion of these peculiarities.

In particle physics data analysis the so-called Lagrange Multiplier Method has been used for many years. It has been implemented in the 1960s by the famous Alvarez group for processing experimental data. Since then it is widely used in physical community. It is named after Lagrange who proposed the method for finding the minimum of functions of many variables under the requirement that they satisfy to some additional conditions (equalities, inequalities). The method uses some artificial variables called Lagrange multipliers having no physical meaning. Another approach is described here, to find the minimum of a function (in our case it is either ({{chi }^{2}}) or logarithm of Likelihood Function) with the constraints. The proposed method is based on the linearization of the constraints during a suitable iteration procedure for the search for the minimum. We propose a new method for selecting submatrices of partial derivatives Jacobi matrix in this paper.

The Multi-Purpose Detector (MPD) is the main experiment of the NICA complex, which is currently under construction at JINR, Dubna. With collisions of heavy-ions in the collider and the fixed-target modes, the MPD detector will cover the energy range (sqrt {{{s}_{{NN}}}} = 2.4- 11) GeV to scan the high baryon-density region of the QCD phase diagram. The main physics objectives of the MPD experiment are to look for the Critical End-Point and the first order phase transition predicted to occur in that region. The commissioning of the MPD detector with cosmic rays and beams is expected to start in 2025. A rich physics program, that includes study of light hadron and (hyper)nuclei production, measurements of flow, correlations and fluctuations will be studied with the first collected data sets. In this paper, we review status of the MPD experiment and discuss its operation details with the first beams.

Simple example of the light front construction of valent quark model of hadrons is presented which allows to classify the hadron states in orbital momentum and spin via introducing the spectral wave functions that depend on spatial coordinates of quarks. These wave functions correspond to the mass squared spectrum of hadrons and can be related to the spectrum of 3-dimensional quantum harmonic oscillator.

In the article, we study the processes of single isolated photon production at the LHC energies in the framework of the parton reggeization approach taking into account LO (mathcal{O}({{alpha }^{1}}alpha _{S}^{0})) and NLO* (mathcal{O}({{alpha }^{1}}alpha _{S}^{0})) contributions, the last one includes only tree–level corrections. Reggeized amplitudes are constructed according to the effective field theory formalism for multi–Regge kinematics processes suggested by L.N. Lipatov. To avoid the double counting between tree–level corrections and unintegrated parton distribution functions, a subtraction scheme is introduced. The results of calculations are compared with experimental data.

A classification of credit institutions using trees and decision forests to identify high-risk objects is considered. The CART decision tree models and Random Forest, Adaboost, and Xgboost decision forests have been developed enabling identification of high-risk credit institutions. Two computing systems, the Google Colaboratory cloud service (Google Colab) and the HybriLIT heterogeneous platform, were used for the calculations.

The analysis of the latest most accurate experimental data on neutron decay for the possibility of the existence of the right-handed vector boson ({{W}_{{text{R}}}}) is carried out. As a result of the analysis, it is found that there is an indication of the existence of the right-handed vector boson ({{W}_{{text{R}}}}) with a mass of ({{M}_{{{{W}_{{text{R}}}}}}} approx 319_{{ - 20}}^{{ + 26}}) GeV and a mixing angle with ({{W}_{{text{L}}}}): ζ = –0.034 ± 0.013. This result should be considered, on the one hand, as a challenge to experimental physics at colliders, where the upper limit on the mass of the right-handed vector boson ({{W}_{{text{R}}}}) is significantly higher and, on the other hand, as evidence that even more accurate measurements of neutron decay and its theoretical analysis are needed.

Trimaximal mixing pattern (TM₁) of the neutrino mixing matrix is consistent with current neutrino oscillation data. In this work, we have investigated the phenomenology of inverse neutrino mass matrix ((m_{nu }^{{ - 1}})) with one-zero textures considering neutrino mixing matrix to be of TM₁ type. There are six possible patterns of (m_{nu }^{{ - 1}}) with one-zero. We have obtained the predictions for the least known neutrino sector parameters such as octant of atmospheric mixing angle, ({{theta }_{{23}}}), Dirac-type CP violating phase, δ, and effective Majorana neutrino mass, ({{m}_{{ee}}}). One of the generic feature of this class of model is the existence of necessary CP violation, i.e., Dirac CP phase δ is non-zero. For maximal value of ({{theta }_{{23}}} = 45^circ ), the model predicts maximal CP violation. The (0nu beta beta ) decay experiments have imperative consequences for viability of one-zero texture in (m_{nu }^{{ - 1}}). It will either refute a model completely or have distinguishing implications for neutrino mass ordering in a model. We have also proposed two possible scenarios in which such phenomenological conjecture may be realized using non-Abelian discrete flavor symmetry group ({{A}_{4}}) and cyclic group ({{Z}_{3}}).