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The General Parton Distributions (GPDs) are applied to study the hard Pseudoscalar Meson Production (PMP) at high energies. The PMP amplitudes are be obtained within the GPDs factorization. They are expressed in terms of GPDs' convolution functions, which are most essential in PMP reactions. We show that these convolution functions can be extracted from the PMP data in future EIC of China (EicC). Predictions of and production at typical EicC energies are performed. [ABSTRACT FROM AUTHOR]

The work is devoted to the transverse polarization () of -hyperons and corresponding antihyperons produced in meson–proton and meson–nuclear interactions in inclusive reactions. The currently available experimental data are compared with calculations based on the chromomagnetic polarization of quark (CPQ) model. The main features of the CPQ model are the prediction of hyperon polarization oscillations depending on the Feynman variable in the case of a sufficiently strong chomomagnetic field and resonant dependence of the polarization on the c.m. energy () for some reactions. Calculations based on the CPQ model were performed for still unexplored kinematic regions and various targets and can be tested in the SPASCHARM experiment at the NRC "Kurchatov Institute"—IHEP. [ABSTRACT FROM AUTHOR]

The paper highlights recent results from the PHENIX experiment. Measurements of identified charged hadron, -meson production in and collisions as well as measurements of identified charged hadron, , , , meson production in small collision systems are presented. Latest results on collectivity effects in small systems and nonprompt photon production in collisions will also be discussed. [ABSTRACT FROM AUTHOR]

In light of the contribution of the states with isospin in the difference of the amplitudes of the processes and being very small, the dispersion sum rules for the difference between the dipole polarizabilities of the charged and neutral pions are analyzed as a function of the meson's parameters. Using the value of the chiral theory of perturbations for , is found for the meson parameter within the region MeV, MeV, keV. Estimated optimum value of decay width yields keV. [ABSTRACT FROM AUTHOR]

Relativistic corrections to the pair production of mesons and baryons consisting of heavy quarks and in the Higgs boson decay are calculated. Relativistic amplitudes and decay rates are constructed within perturbative Standart Model and relativistic quark model. The numerical values of the relativistic effects turn out to be significant and must be taken into account in order to achieve good calculation accuracy. [ABSTRACT FROM AUTHOR]

In heavy-ion reactions, statistical models predict a rapid change in the baryon-to-meson ratio as a function of the collision energy. This change occurs when the hadronic medium transits from a baryon- to a meson-dominated gas. The transition is expected to take place at a temperature around 140 MeV and a baryon chemical potential around 420 MeV, corresponding to a center-of-mass collision energy of GeV. The energy range of the MPD experiment will be suitable for the exploration of this transition region. We present preliminary results of feasibility studies for the measurement of the transverse momentum spectra for mesons and baryons, using Monte Carlo data samples, in order to study the crossing point between these transverse momenta, as a function of the centrality and collision energy. [ABSTRACT FROM AUTHOR]

At present, production, properties, and decays of heavy baryons are vigorously studied both experimentally and theoretically. The flavor symmetry allows an existence of a large number of hidden charm pentaquark states which differ by their light quark content. Here, ratios of weak decay widths of bottom baryons into a pentaquark and light meson are presented. The most interesting for experimental observation decays of bottom baryons are specified. [ABSTRACT FROM AUTHOR]

New NICA accelerator complex at JINR (Dubna), based on the existing upgraded Nuclotron accelerator, will allow conducting all types of research in the field of high-energy physics. The main tasks of this project are study of the properties of the deconfinement phase transition, experimental investigation on medium modification of vector mesons, and search for the QCD critical end point. Thus, two interaction points are foreseen in the NICA collider: one for studying the collision of heavy ions on the Multipurpose detector MPD, the other for polarized beams for the experiment on the SPD installation. The ambitious physical goals of MPD require excellent particle identification at the maximum possible range of phase space. Identification of charged hadrons is achieved by combining time-of-flight measurements and energy loss measurements from the time-projection camera TPC. The Time-of-Flight system is based on multigap resistive plate chambers (MRPC), which are successfully used to identify particles in similar experiments around the world. A production site has been organized at the Laboratory of High Energy Physics of JINR for serial production of TOF MPD modules including 10 MRPCs. This site includes the entire cycle of work from preparing materials for the assembly of detectors to testing the assembled modules on cosmic radiation. This report presents the structure of the TOF system, its main parameters, the current state and the results of decoding and processing data obtained at the module testing facility. [ABSTRACT FROM AUTHOR]

The deconfined state of strongly interacting quarks and gluons, quark–gluon plasma, may be formed in relativistic ion collisions at sufficient temperature and energy density. The signatures of quark–gluon plasma formation were observed in heavy-ion collisions by studying meson production. In small-collision systems, such as , , , and , the volume and lifetime of the produced medium might be insufficient for observation of quark–gluon plasma effects. However various physics mechanisms reflecting initial state of the collision, cold nuclear matter effects, may lead to a collective-like behavior in small-collision systems without quark–gluon plasma formation. The nuclear modified parton distribution functions are considered to be an underlying physics mechanism of cold nuclear matter effects. This paper presents the comparison of meson production in , , , and collisions at GeV at midrapidity ( , measured by PHENIX, to PYTHIA calculations with nuclear modified parton distribution functions EPPS16 and CTEQ15. The meson production in collisions at GeV might be driven by mechanisms additional to nuclear modification of parton distribution functions. [ABSTRACT FROM AUTHOR]

The invariant differential cross sections of inclusive and mesons were measured at midrapidity in pp collisions at TeV and in p–Pb collisions at TeV in a wide transverse momentum () range with the ALICE experiment. The unprecedented large range up to 200 GeV/ for mesons was achieved by combining various analysis techniques as well as triggers involving the Electromagnetic Calorimeter (EMCal) and the Photon Spectrometer (PHOS). A method to reconstruct properly merged clusters of high neutral pions, originally developed for EMCal, was implemented in PHOS and its results are discussed for the first time in this paper. The obtained cross sections provide strong constraints on parton distributions and fragmentation functions for light mesons, and can be used to further improve the theoretical descriptions of hadron production. The first multiplicity study of light-neutral meson production in pp collisions at TeV shows modification of light-neutral meson yields. The nuclear modification factors, recently measured in p–Pb collisions at TeV for high , are consistent with unity, providing no evidences of parton energy loss in small colliding systems. [ABSTRACT FROM AUTHOR]

The new relativistic semiclassical leptonic decay widths of vector mesons as the relativistic systems of two quarks with arbitrary masses interacting by means of the funnel-type potentials with Coulomb interaction are obtained. The behavior of the relativistic leptonic decay widths of vector mesons is investigated. Comparison of the behavior for new expression with its relativistic spinless analog is given. Consideration is conducted within the framework of completely covariant quasipotential approach in the Hamiltonian formulation of quantum field theory via a transition to the relativistic configurational representation in the case of two relativistic spin particles of arbitrary masses. [ABSTRACT FROM AUTHOR]

Using the Wilson confinement criterion a holographic model for finding a string-like spectrum of meson excitations is proposed. The model is applied to the vector and scalar mesons and a good agreement is obtained both with the existing experimental data and with some other known phenomenological approaches. The constructed model provides a novel realization of spontaneous chiral symmetry breaking between parity partners. [ABSTRACT FROM AUTHOR]

The confinement potential of the Cornell type between two static color sources is derived and analyzed within the framework of a generalized Soft-Wall holographic approach to strong interactions. This approach was originally developed for describing the phenomenology of linear Regge spectrum of light mesons in the most general form. The "linear plus Coulomb" confinement potential is obtained both in the vector and in scalar channels. It is shown that the quantitative agreement with the phenomenology and lattice simulations is better in the scalar channel. [ABSTRACT FROM AUTHOR]

The energy and centrality dependence of -meson spectra measured by the STAR Collaboration at RHIC in collisions over a wide range of GeV was studied in the -scaling approach. The scaling function was constructed and the self-similarity of -meson production was confirmed. This observation is consistent with an abrupt decrease of the model parameter from the value of 0.16 at and 11.5 GeV to about 0.09 at the top RHIC energy. The scaling parameter is interpreted as a specific heat of the produced medium. The non-trivial dependence of on the collision energy shows that meson is much more sensitive to properties of nuclear medium than a non-identified negative hadron. The irregularities in the behavior of the specific heat parameter are considered as a possible indication of phase transition in nuclear matter. [ABSTRACT FROM AUTHOR]

A new relativistic semiclassical expression is derived for leptonic decay widths of vector mesons as a composite system of two quarks having equal masses and interacting via a funnel-like potential. This new expression is compared with its nonrelativistic spinless and relativistic spin and spinless analogs. The effect of the spins of equal-mass quarks forming vector mesons on the behavior of the leptonic decay widths of these mesons is analyzed. This analysis is performed within the relativistic quasipotential approach based on the covariant Hamiltonian formulation of quantum field theory by means of a transition from the momentum representation in Lobachevsky space to the three-dimensional relativistic configuration representation for the case of a composite system of two relativistic spin equal-mass particles. [ABSTRACT FROM AUTHOR]

The transparency of the carbon nucleus with respect to eta mesons of energy 25 to 95 MeV was measured. Mesons of this energy originated from the photoproduction on quasifree protons of the carbon nucleus () under the effect of photons with energies between 720 and 770 MeV. The inelastic cross sections for interaction in nuclear matter are determined from the measured transparency of the nucleus. The absence of nucleon resonances in the measured cross section—in particular, the resonance, which is usually associated with the assumption of the existence of eta-meson nuclei—is discussed. [ABSTRACT FROM AUTHOR]

Heavy mesons and doubly heavy baryons with the dynamic properties governed by the light quark motion relative to the fixed center of forces are studied within the Heavy Quark Effective Theory. The distribution amplitudes of the hadrons in question are compared, model functions of these amplitudes for the doubly heavy baryons are introduced, and their scale dependence is investigated. [ABSTRACT FROM AUTHOR]

A statistical method for extracting the η → γγ signal upon rejecting those γ clusters that form pairs with invariant masses close to that of the π0 meson is proposed. The η selection efficiency (the ratio between the numbers of selected and produced η mesons) and the signal-to-background ratio as a function of the η transverse momentum are obtained using a template of proton–proton collisions at = 13 TeV simulated with PYTHIA 8.2 (with Monash-2013 tuning). The proposed method provides for an η → γγ selection efficiency of ~80% and for a 20–50% increase in the signal-to-background ratio compared to currently implemented techniques. [ABSTRACT FROM AUTHOR]

According to modern theories, the parameters of neutral mesons such as their mass and width are closely connected with the medium in which the mesons are present. Experimental data on the study of mesons in a nuclear medium are in demand for development of theoretical models describing processes in the field of nonperturbative quantum chromodynamics (QCD). Masses and widths of neutral mesons produced in meson-nucleus interactions on various nuclei are measured in the Hyperon-M experiment at the U70 accelerator. The paper describes a method for precision measurement of the parameters of neutral mesons, presents the results on measurement of the mass and width of the meson and preliminary results on the measurement of the mass and width of the meson. The measurements indicate the absence of dependence of the quantities under study on the nuclear environment. [ABSTRACT FROM AUTHOR]

In the FRAGM experiment at the heavy-ion accelerator accumulator complex ITEP TWA, yields of cumulative charged mesons have been measured in a fragmentation of carbon ions with the energy of 3.2 GeV/nucleon on a beryllium target. The momentum spectra of mesons cover four orders of the invariant cross section magnitude. They demonstrate the exponential fall with increasing energy. The measured inverse slope parameter is compared with similar measurements in nucleon–nucleus interactions and ion–ion collisions at lower energies. The energy dependence of the ratio of the yields of negative to positive mesons is presented. This dependence is discussed in a connection with Coulomb and isotopic effects. The obtained data are compared with predictions of several ion–ion interaction models. [ABSTRACT FROM AUTHOR]

The masses of excited charmed mesons are shown to decrease by (50–150) MeV due to a flattening of the confining potential at large distances, which effectively takes into account open decay channels. The scale of the mass shifts is similar to that in charmonium for (4660) and (4700). The following masses of the first excitations: MeV, MeV, MeV, and MeV, and second excitations: MeV, MeV, MeV, and MeV, are predicted. The other states with , 1, 2 and have their masses in the region GeV. [ABSTRACT FROM AUTHOR]

Exact solutions of relativistic quasipotential equations in the configuration representation are found for the -state wave function for a composite system of two arbitrary-mass relativistic spinor quarks interacting via a Coulomb-like chromodynamic potential. Composite systems whose spinor structure corresponds to the pseudoscalar, pseudovector, and vector cases are considered. Quantization conditions for the energy levels of the meson -wave state are determined in the pseudoscalar, pseudovector, and vector cases. Expressions for the relativistic threshold resummation factor corresponding to a Coulomb-like chromodynamic potential are obtained for these spinor meson structures, and the properties of this factor are studied. New regularities in the behavior of the threshold factor are revealed. The present analysis is performed within the relativistic quasipotential approach based on the covariant Hamiltonian formulation of quantum field theory by means of the transition from the momentum representation in Lobachevsky space to the three-dimensional relativistic configuration representation for the case of a composite system of two arbitrary-mass relativistic spinor particles. [ABSTRACT FROM AUTHOR]

Hadron form factors are calculated using the Lorentz-contracted wave functions, determined in the arbitrary dynamical scheme with the instantaneous interaction. It is shown that the large asymptotics of the form factors is defined by the contraction coefficient , where is the meson mass, and weakly depends on the interaction used. The resulting form factors and are obtained in good agreement with the lattice and experimental data. Important consequences for the dynamics of hadron decays and scattering are shortly discussed. [ABSTRACT FROM AUTHOR]

Parameterizations of the electromagnetic form factors of meson are considered. Using these parameterizations theoretical predictions for the total cross section of the direct meson production in annihilation, , are obtained. [ABSTRACT FROM AUTHOR]

A preliminary result of an analysis of the process whose cross section was measured in the range of center-of-mass collision energies between 1.2 and 2 GeV is presented. The analysis is based on the data sample corresponding to an integrated luminosity of about 120 pb accumulated with the CMD-3 detector at the VEPP-2000 electron–positron collider. A procedure for separating signal events is developed, and the dominance of the neutral mode is confirmed. The cross section for the process is measured to a precision higher than that in earlier experiments. This permits improving the accuracy in measuring the mass and width of the (1680) meson, testing the accuracy of the isotopic relations, and more accurately calculating the hadronic contribution to the muon anomalous magnetic moment (). [ABSTRACT FROM AUTHOR]

The first observation of two excited states of the is presented together with the measurements of the mass and the mass difference . Additionally, we present a study of -baryon excited states, namely, , , , and , decaying into . The two analyses are carried out using the data collected in proton-proton collisions at a centre-of-mass energy of 13 TeV by the CMS experiment and corresponding to an integrated luminosity of about 140 fb . [ABSTRACT FROM AUTHOR]

Spectrum, radial wave functions at origin, decay constants, weak decay widths, life-time, and branching ratios for radially excited conventional and hybrid mesons are derived within non-relativistic quark model framework employing Schrödinger equation by shooting method. Calculated results are compared with available theoretical results and experimental observations. This work may help in identifying the new discovered meson states at CDF, LHCb, and ATLAS. [ABSTRACT FROM AUTHOR]

The coherent photoproduction of and on nuclei in the mass-number region of is studied systematically over the range between the threshold and the laboratory photon energy of GeV. The amplitude for photoproduction on nuclei is constructed on the basis of the impulse approximation with allowance for a number of processes responsible for meson–nucleus final-state interaction. The pion-rescattering processes and occurring on spectator nucleons, and production followed by absorption by spectator nucleons, and three-body –NN and –NN interactions are described for the first time within a unified microscopic approach. [ABSTRACT FROM AUTHOR]

New experimental data on the multifragmentation of carbon nuclei that is initiated by the photoproduction of neutral pions and eta mesons are discussed. The novelty is associated with the exclusive character of the processes being studied, in which case a determination of partial meson-photoproduction reactions is followed by an analysis of complementary particles for coincidence. The experiment being discussed was performed by the GRAAL (GRenoble Accelerateur Anneau Laser) Collaboration in a beam of 500- to 1500-MeV Compton photons. The possibility of performing new experiments within the BGO-OD Collaboration (Bonn, Germany) is considered. A new method for studying the interaction of short-lived mesons with nuclei on the basis of detecting cascade recoil nucleons is proposed. [ABSTRACT FROM AUTHOR]

Spectrum, radii, radial wave functions at origin, decay constants, and momentum widths for radial and orbital excited mesons are derived within non-relativistic quark model framework through finding numerical solution of the Schrödinger equation by shooting method. Masses of orbitally excited states are derived with a much simpler method that is developed by combining the uncertainty and variational principles. Masses of mesons are also calculated by using Momentum widths. Besides calculations, theoretical results are compared with the experimental observations which have implications for scalar form factors and leptonic decays of mesons. [ABSTRACT FROM AUTHOR]

The expressions for the transition form factors (TFFs) of pseudoscalar mesons are derived in the context of the anomaly sum rule approach based on the dispersion representation of the axial anomaly and hypothesis of the global quark-hadron duality. The obtained solutions take into account the π0-η-η′ mixing and the contribution of the gluon anomaly. It is shown that this method allows one to describe the TFFs for spacelike and timelike photon virtualities. The contribution of the gluon anomaly is estimated. [ABSTRACT FROM AUTHOR]

A simple, physically validated, model of charge-independence and charge-symmetry breaking is proposed for the pion-nucleon coupling constant. Within this model, the pion-nucleon coupling constants are assumed to be in direct proportion to the masses of nucleons and pions involved in the interaction. The charge dependence of the pion-nucleon coupling constants and low-energy parameters of nucleon-nucleon scattering in the 1S0 spin-singlet state is studied on the basis of Yukawa's meson theory. By using the value of f p p π 0 2 = 0.0749 (7) established reliably for the pseudovector pion-nucleon coupling constant, which characterizes the strength of the nuclear proton-proton interaction, the values of f c 2 = 0.0802 (7) and f 0 2 = 0.0750 (7) were calculated for, respectively, the charged and neutral pion-nucleon coupling constants, along with the value of f n n π 0 2 = 0.0751 (7) , which characterizes the strength of the nuclear neutron-neutron interaction. The values calculated for the low-energy parameters of neutron-proton and neutron-neutron scattering with the aid of the above constants agree well with experimental data. [ABSTRACT FROM AUTHOR]

The neutrino/antineutrino flux ratios ( ν e / ν ¯ e and ν μ / ν ¯ μ ) and the flavor ratio (ν μ + ν ¯ μ) / (ν e + ν ¯ e) clearly demonstrate the distinctions between the predictions of hadronic-interaction models for the production spectra of pions and kaons, which are the main sources of atmospheric neutrinos in the region of Eν ≲ 500 TeV. The values of the ν / ν ¯ ratio are sensitive to variations in the π+/π−, π/K, and K+/K− meson ratios, which are determined by the cross sections for inclusive meson-production processes in hadron-nucleus (hA) collisions; the elemental composition of cosmic rays also exerts influence, through the p/n ratio, on the development of hadronic cascades and on the neutrino ratios. The difference in ν / ν ¯ and in the flavor ratio for a number of hadronic-interaction models is shown on the basis of calculating neutrino fluxes at energies in the range between 102 and 108 GeV. A comparison of the calculated results with new experimental data shows the reliability of this calculation, which, on the whole, reflects correctly the mechanism of atmospheric-neutrino production. The spectra of atmospheric muon neutrinos from calculations based on the Kimel-Mokhov, SIBYLL 2. 1, and EPOS LHC models describe fairly well experimental results. At energies in the range of 1–500 TeV, the curves calculated within these models combined with the Hillas-Gaisser spectrum are close to the best fit to data from measurements in the IceCube experiment. [ABSTRACT FROM AUTHOR]

The differential cross sections for the elastic scattering of π± and K+ mesons on 13,15C and 15N nuclei at intermediate energies were calculated within Glauber diffraction theory. The sensitivity of the calculated features to variations in the target wave functions and in the multiple-scattering contribution were analyzed. The contribution of double scattering were estimated. [ABSTRACT FROM AUTHOR]

We present an analytic calculation of Branching Ratio (BR) and Charge—Parity (CP) violating asymmetries of the B s 0 meson decays to light vector mesons (K * 0 K ¯ * 0 ) within the framework of Naive Factorization (NF) and QCD Factorization (QCDF). We find the BR (B s 0 → K * 0 K ¯ * 0 ) = 1.87 × 10 − 5 and 1.40 × 10−5 for NF and QCDF, respectively. We also find that within QCDF the direct CP violation (A C P dir ) = − 0.01 , CP violation in mixing (A C P mix ) = 0.31 and CP violation due to interference (A C P ΔΓ ) = 0.95 . [ABSTRACT FROM AUTHOR]

Double differential yield of π±, K±, protons, and antiprotons as a function of laboratory momentum is presented using hadron production models. This study is done in several polar angle intervals from 0 < θ < 420 mrad for π± mesons and 0 < θ < 360 mrad for K± mesons, protons, and antiprotons. The study is carried out for p + C interactions at 120 GeV/c. For simulation, three hadron-production models: EPOS-LHC, EPOS 1.99, and QGSJETII-04 are used. Since no experimental data at 120 GeV/c is available yet, therefore, the models' predictions are compared with the measurements of NA61/SHINE experiments at 31 GeV/c. It is found that the QGSJETII-04 model gives high peak value, for π± mesons, in the polar angle interval of 20–40 mrad, while in the range of 40–240 mrad, EPOS-LHC shows higher yield than EPOS 1.99 and QGSJETII-04 models, whereas all show higher yield than the experimental data. For π± mesons, in all angular intervals, at high momentum values, all the three models are consistent and surprisingly give the same yield as that of the experimental data. For K± mesons, QGSJETII-04 shows higher peak values at all polar angles ranging from 0 to 360 mrad as compared to that of EPOS 1.99 and EPOS-LHC models, whereas all models give higher yield at low angular intervals than the experimental data and the same yield at high angular intervals. The models demonstrate similar yields for protons at all angles but underestimate the experimental data at low angular intervals and provide the same yield at high angular intervals. The QGSJETII-04 model presents higher yields of antiprotons in comparison to the EPOS 1.99 and EPOS-LHC models, for almost all angular intervals. Generally, at higher angular range, i.e., from 240 to 420 mrad, particularly at high momentum, all the three models show similar results. [ABSTRACT FROM AUTHOR]

It is shown that, upon the stopping of a negatively charged kaon and its absorption by a nucleus, there arise particles whose appearance does not comply with thermodynamic evaporation theory. An identification of these particles by various methods makes it possible to evaluate the nearly identical yields of 3H and 3He nuclei. This result may serve as an indication that direct reactions induced by interaction with 4He are observed in K−-meson absorption in nuclei. [ABSTRACT FROM AUTHOR]

Reliable cross sections for kaon-nucleon scattering are required for quantitatively estimating the effect of secondary interactions of cumulative K+ and K− mesons on their yields from various nuclei in proton-nucleus (pA) interactions at proton energies between 9 and 10 GeV and between 15 and 70 GeV. The preparation of these cross sections for a simulation code was a priority task that was solved for the kaon-momentum range between 0.35 and 2.75 GeV/c. [ABSTRACT FROM AUTHOR]

The photoproduction of J/ψ mesons off nuclei at the energies of 8 and 11 GeV, which are close to the threshold for their production on a free nucleon, is considered on the basis of the first-collisionmodel relying on the nuclear spectral function and including incoherent processes of charmonium production in photon-nucleon collisions. The model takes into account the absorption of final J/ψ mesons, the binding of target nucleons, and their Fermi motion, as well as the effect of the scalar J/ψ-nucleus potential (or the inmedium shift of the J/ψ-meson mass) on these processes. Under various assumptions on the magnitude of this shift, the momentum dependences of various observables, such as the relative transparency of carbon and gold nuclei and the J/ψ-meson yields, are calculated for meson production on these nuclei. The observables in question include the relative transparencies of these nuclei to J/ψ mesons and the absolute and relativemeson yields from them. It is shown that, at the energy of 11 GeV, which is above the threshold, the first observable is virtually independent of the in-medium change in the J/ψ-meson mass. At the same time, it is moderately sensitive to this change at the subthreshold energy of 8 GeV. On the other hand, it is shown that, at these photon energies, the absolute and relative values of the differential cross sections, especially for the the heavy nucleus of 197 Au, in the momentum range of 4-6 GeV/с are highly sensitive to the in-medium change in the J/ψ-meson mass. Therefore, the present calculations can be used to determine the unknown shift of the J/ψ-meson mass in nuclei by means of comparing their results with data expected from experiments in Hall C at the Continuous Electron Beam Accelerator Facility (CEBAF, USA) upgraded to the energy of 12 GeV. [ABSTRACT FROM AUTHOR]

The branching ratios and differential distributions for the four-leptonic decays B−→μ+μ−v¯ee−, B−→e+e−v¯μμ−, and B−→μ+v¯μμ−μ− are calculated within the Standard Model. The branching ratios for the rare decays Bd,s → e+e−μ+μ− and Bd,s → μ+μ−μ+μ− are estimated. Methods for testing the lepton universality in rare multileptonic decays of charged and neutral B mesons are proposed. [ABSTRACT FROM AUTHOR]

The relativistic mean field (RMF) model with a small number of adjusted parameters has been used successfully in the last thirty years for predictions of various ground-state nuclear properties of nuclei. In this model, Dirac and Klein-Gordon like equations obtained from application of variation principle on phenomenological Lagrangian density are solved iteratively for calculations of nuclear properties of nuclei. For this purpose, parameters such as masses of considered mesons, nucleon-meson coupling constants, and self-couplings of mesons are needed and they are fitted from experimental data. Some parameter sets for RMF model introduced to correct predictions of nuclear properties of nuclei cover nuclidic chart. Besides Artificial Neural Network (ANN) method is used successfully in many field of science as in nuclear physics. ANN is known as a very powerful tool that are used when standard techniques fail to estimate the correlation between the variables. In the present study, ANN method has been employed to check its understanding capability of relations between RMF model parameters and their predictions on the ground-state binding energies of some spherical nuclei. Understanding capability of ANN method for these relations of considered nuclei has been found well. Based on this success, new non-linear parameter set for RMF model called DEFNE by us have been produced by using ANN method. Furthermore, predictions of RMF model with DEFNE parameter set for ground-state binding energies and charge radii of nuclei cover nuclidic chart have been found as in agreement with the available experimental data. [ABSTRACT FROM AUTHOR]

The cross sections for elastic and inelastic η-meson scattering on 7Li nuclei are obtained on the basis of the αt-cluster representation of the target nucleus. The experimentally known values of the parameters of elastic ηα and αt scattering are used in exactly solving three-body Faddeev equations with separable two-body potentials. The η7Li elastic-scattering scattering length found from respective calculations is aη7Li = −0.310 − i0.198 fm. [ABSTRACT FROM AUTHOR]

The isobaric model, which describes well the experimental cross sections for η'-meson photoproduction at photon energies between 1500 and 2300 MeV, is refined with allowance for new experimental data on the beam asymmetry for this reaction. [ABSTRACT FROM AUTHOR]

New relativistic semiclassical conditions and leptonic decay widths are obtained within quantum chromodynamics for nonsingular confining quasipotentials and funnel-type potentials (instantoninteraction approximation). The respective analysis is performed within a fully covariant quasipotential approach in quantum field theory. This approach is formulated in the relativistic configuration representation for the case of interaction between two relativistic spinless particles of arbitrary mass. [ABSTRACT FROM AUTHOR]

Abstract?A review of works performed at the Institute for Nuclear Research of the Russian Academy of Sciences and at the International Laser Center of the Moscow State University in the context of the new research area called "nuclear photonics" is presented. Nuclear photonics is based on creation of the new-generation gamma-ray sources which make it possible to solve a number of fundamental and applied problems, including research of low-energy photonuclear reactions, namely, investigation of collective excitations of nuclei near the threshold (pygmy resonances); nuclear safety assurance; production of low-energy positron beams; and phase-contrast X-ray imaging. [ABSTRACT FROM AUTHOR]

On the basis of the first-collision model that relies on the nuclear spectral function and which includes incoherent processes involving charmonium production in proton-nucleon collisions, the photoproduction of J/ ψ mesons on nuclei is considered at energies close to the threshold for their production on a nucleon. The absorption of final J/ ψ mesons, their formation length, and the binding and Fermi motion of target nucleons are taken into account in this model along with the effect of the nuclear potential on these processes. The A dependences of the absolute and relative charmonium yields are calculated together with absolute and relative excitation functions under various assumptions on the magnitude of the cross section for J/ ψN absorption, the J/ ψ-meson formation length, and their inmedium modification. It is shown that, at energies above the threshold, these features are virtually independent of the formation length and the change in the J/ ψ-meson mass in nuclear matter but are rather highly sensitive to the cross section for J/ ψN interaction. The calculations performed in the present study can be used to determine the unknown cross section for J/ ψ-meson absorption in nuclei from a comparison of their results with data expected from experiments in the Hall C of the CEBAF (USA) facility upgraded to the energy of 12 GeV. It is also shown that the absolute and relative excitation functions for J/ ψ mesons in photon-nucleus reactions at subthreshold energies are sensitive to the change in the meson mass and, hence, carry information about the properties of charmonium in nuclear matter. [ABSTRACT FROM AUTHOR]

The Lorentz contracted form of the static wave functions is used to calculate the valence parton distributions for mesons and baryons, boosting the rest frame solutions of the path integral Hamiltonian. It is argued that nonperturbative parton densities are due to excitedmultigluon baryon states. A simplemodel is proposed for these states ensuring realistic behavior of valence and sea quarks and gluon parton densities at Q = 10 (GeV/ c). Applying the same model to the proton spin problem one obtains Σ = 0.18 for the same Q. [ABSTRACT FROM AUTHOR]

A theory of lepton decay constants based on the path-integral formalism is given for chiral and vector mesons. Decay constants of the pseudoscalar and vector mesons are calculated and compared to other existing results. [ABSTRACT FROM AUTHOR]

Use of the effective Lagrangian incorporating both the scalar and pseudoscalar mesons gives a possibility to calculate the ππ-scattering lengths without attraction of the ChPT theory. [ABSTRACT FROM AUTHOR]

The isobarmodel, which reproduced fairly well experimental data on η′-meson photoproduction at photon energies between 1500 and 3700 MeV, is refined with allowance for new experimental data in the vicinity of the reaction threshold. [ABSTRACT FROM AUTHOR]