Fundamental Interactions of Fields and Particles

Participating Countries and International organizations:
Argentina, Armenia, Azerbaijan, Belarus, Bulgaria, Canada, CERN, Chile, China, Croatia, Czech Republic, Finland, France, Georgia, Germany, Greece, Hungary, ICTP, India, Italy, Japan, Kazakhstan, Mexico, Mongolia, New Zealand, Norway, Portugal, Poland, Republic of Korea, Russia, Serbia, Slovakia, Spain, Sweden, Switzerland, Ukraine, United Kingdom, USA, Uzbekistan, Vietnam.

Issues addressed and main goals of research:
    The main aim of the research within the theme is the construction of theoretical models and their application to the description of properties of elementary particles and their interactions. This research includes the following directions of activity.
The development of quantum field theory formalism in gauge and supersymmetric theories. Construction and investigation of the models of particle physics beyond the Standard Model.
Theoretical support of experiments at the Large Hadron Collider on the search of new physics and the study of the properties of the Higgs boson.
Calculation of radiative corrections to the processes of particle creation within the Standard Model and its extensions. Investigation of neutrino properties and neutrino oscillations. Investigation of the hadron properties within quantum chromodynamics and phenomenological quark models. Study of the hadron spin structure with the help of generalized and transverse momentum dependent parton distributions and theoretical support of NICA/SPD program.
Study of heavy quark properties and exotic hadrons. Lattice simulations for obtaining nonperturbative results in gauge theories. Investigation of dense hadronic matter and theoretical support of the MPD/NICA program.
Theoretical support of a wide range of current and future experiments at JINR, IHEP, CERN, GSI, JLab and other physics centers.

Expected results in the current year:

1. Verification of the completeness of basis functions for elliptic polylogarithms by explicit calculations of the two-loop Feynman diagrams in the nonrelativistic QCD.
   
   Development of algorithm for the epsilon expansion of generalized hypergeometric functions at integer and half-integer index values via reduction of the corresponding differential system to the epsilon form.
   
   Derivation of systematic solution of quantum spectral curve equations for the case of maximally supersymmetric Yang-Mills theory in 4 dimensions by expansion in the double limit of weak coupling and large spins of sl(2) operators.
   
   Perturbative calculation of anomalous dimensions of large-charge operators in different QFT models and comparison of results with predictions obtained via semi-classical methods.
   
   Comprehensive analysis of the prospects for experimental discovery of different signatures in a number of Standard Model extensions with additional abelian gauge symmetries. Investigation of the possibility of resonant leptogenesis in the so-called superweak extensions of the SM.
   
   Calculation of effective potentials in modified gravity models taking into account quantum effects. Determination of the range of parameters of these models allowing realistic solutions for the inflationary epoch of the early universe.
   
   Detailed cosmological and astrophysical analysis of the properties of Primordial Black Holes as candidates for Dark Matter and connections with the current Supermassive Black Holes.
   
   Analytical evaluation of 2-loop radiative corrections to the parapositronium lifetime.
   
   Investigations of the multiplicities of quark and gluon jets with the account of resummation of large logarithms arising in the high-energy limit.
   
   Derivation of convenient parameterization for the transverse-momentum-dependent parton densities in nucleons and nuclei in the first two orders of perturbation theory.
   
   Fit of the strong coupling constant from the deep inelastic scattering data in the first four orders of perturbation theory taking into account the resummation of large threshold logarithms
   
   Study of the relations for the spacelike and timelike kernel functions for the hadronic contribution to the muon anomalous magnetic moment.
    
2. Analytic evaluation of 3-loop 2-point Feynman master-integrals with composite external vertices for arbitrary indices of propagators as a hypergeometric series.
   
   Derivation and analysis of a full differential equation system for Feynman integral with maximal powers of masses and momenta using the Mellin-Barnes integral representation.
   
   Calculation of the a_s²(a_sβ₀)^n-1 and a_s³β₁(a_sβ₀)^n-2 contributions to the nonsinglet Efremov-Radyushkin-Brodsky-Lepage evolution kernel and the correlator of two vector composite quark currents in QCD that will allow to clarify numeric hierarchy among different parts of the beta-expansion for the correlator and kernel in the orders a_s² and a_s³ (a_s and β_n are the strong coupling and (n+1)-loop coefficient of the beta-function expansion in QCD, respectively).
   
   Calculation of pion electromagnetic form factors in framework of the light-cone sum rules in the low and (or) moderate energy regime. The domain of the framework applicability will be expanded by using analytic perturbation theory in order O(α_s) and compared with high precision Jlab experimental data.
   
   Revision of the distribution amplitudes (leading twist) of (pseudo)scalar and (longitudinal and transverse) vector mesons within the QCD SRs taking into account new QCD corrections O(α²_s) obtained for all of their components.
   
   Analytical and numerical optimization of perturbation series for observables using beta-expansion and renormalization group in QCD for improvement of estimates of: R[e^-e⁺→hadrons], width of tau-decay, Bjorken polarized SR that are known in multiloop calculation and comparison of our results with experimental data.
   
   Evaluation of the QCD analytic coupling constant in high orders of perturbation theory and its use for studying processes at small values of the square of the momentum transfer.
   
   Study of the sum rules for hadron fragmentation functions in QCD making use of the generalized truncated Mellin moments approach.
   
   Study of the new-found types of transverse momentum dependent parton distributions within the original framework. The new approach involves the new-found additional contribution in the inverse Radon transforms.
   
   Extraction of transverse generalized parton distributions from pseudoscalar meson leptoproduction at electron-ion colliders.
   
   Study of the hadronic structure function of the Drell-Yan processes in the framework of perturbative QCD in α_s² order in the coupling constant. Сheck of the Lam-Tung relation in α_s² order in the strong coupling constant.
   
   Establishing of a computational framework to analyze CMS Open Data.
   
   Examination of the methods of extraction of the total cross sections to understand a tension between the data obtained by different collaborations based on the analysis of experimental data on the elastic differential cross sections in the energy range 7-13 TeV. Determination of the structure of the elastic scattering amplitude in the framework of the High Energy Genarelized Structure model taking into account the hadron structure at NICA energies.
   
   Study of the dark axion portal and implementation to fixed target experiments to obtain bounds for a model. Bounds are needed for analysis of New physics and NA64 experiment, in particular. The visible mode of the axion and dark photon will be studied.
   
   Study the phase diagram of SU(2)-Higgs electroweak theory. Study of Z(N) symmetry and thermodynamic properties of meta-stable states at very high temperature in the context of QCD and electroweak theory.
   
   
3. Сalculation of the branchings of both leading electromagnetic decays and suppressed weak nonleptonic two-particle decays of vector B-mesons.
   
   Search for possible theoretical explanation of the observed anomalies in B-physics.
   
   Contribution to the research program for future electron-positron colliders. High-precision theoretical predictions for the processes of particle interaction at these colliders and the effects associated with the polarization of the initial beams and produced tau leptons.
   
   Investigation of the spectral structure of the pionic/kaonic helium using the NRQED formalism with account of mα⁶ and partially mα⁷ order corrections. Calculation of the dependence of the spectral lines on the masses of pions (kaons).
   
   Derivation and calculation of the relativistic and radiative corrections for the forbidden dipole (E1) transitions in the H₂⁺ hydrogen molecular ion. It is expected that precision spectroscopy of H₂⁺ ions will provide the most accurate data for the proton-to-electron mass ratio with the relative precision better than 10⁻¹².
    
4. Study of propagation of nonlinear waves inside the nonextensive quark-gluon plasma medium under the influence of a magnetic field.
   
   Study of the thermodynamics of the quark-gluon and the hadronic medium using anisotropic quasi-power-law distributions.
   
   Study of the violations of the Okubo-Zweig-Iizuka rule in the lattice gauge theory for the scalar, pseudoscalar, vector, and axial vector channels and estimation of the effects of monopoles, instantons, and strong magnetic fields.
   
   Analysis and interpretation of the data from the Large Hadron Collider on the charge balance function from Pb+Pb collisions at the center-of-mass energy 2.76 TeV per nucleon pair in the framework of the HYDJET++ model.
   
   Analysis of velocity, vorticity, and helicity and estimation of global polarization of hyperons in heavy-ion collisions at NICA energies using the Parton-Hadron-String Dynamics model.
   
   Study of recently predicted thermal-shear and spin-Hall contributions to the particle polarization in heavy-ion collisions and their impact on the Λ polarization in the NICA-FAIR-HADES energy range.
   
   Study of a collective flow of light nuclei produced in heavy-ion collisions in the SPS-RHIC energy range within the thermodynamic approach based on the three-fluid dynamics.
   
   Description of the Delta resonance–nucleon system at finite temperature and a small baryon chemical potential.
   
   Description of the formation of the quasi-periodic and periodic structures at phase transitions in nuclear matter.
   
   Investigation of the properties of phase transitions and anisotropy of interquark interaction in a fast rotating (quark-)gluon plasma in lattice QCD. Study of the possibility for the existence of inhomogeneous phases in rotating QCD.
   
   Сalculation of nonlocal observables for a strongly coupled plasma within the holographic approach. Phase transition analysis and investigation of rotation effects.
   
   Study of the Equation of State of QCD at nonzero baryon density in the external magnetic field using lattice simulation with physical quark masses.
   
   Calculation of the thermodynamic potential in the 3-flavour chiral quark models with the inclusion of the full momentum dependence of the in-medium meson polarization loops and the corresponding meson Landau damping in the quark medium for the zero and finite baryon chemical potential.
   
   Study of the equation of state of the cold quark matter using a new chiral density functional including diquark degrees of freedom and its effect on the neutron star structure.
   
   Investigation of an algorithm for solving the Israel-Stewart hydrodynamic equations using an implicit method for numerical solving the relaxation equations.
   
   Investigation of hadronic vacuum polarization contributions to the anomalous magnetic moment of muon in the framework of the Domain Model of QCD vacuum taking into account radially excited mesons.
   
   Study of critical phenomena in hadronic matter due to the condensation of gluon tachyonic modes in chromomagnetic fields in the deconfined phase.
   
   Study of the photon production in heavy ion collisions via the conversion of gluons to photon in the presence of the background gauge fields taking into account the contribution of all Landau levels in the quark propagator, including the contribution of quarks with mass squared of the order of the strength of the background field.
   
   Study of anomalous transport phenomena in a relativistic quantum medium related to its stability with respect to the space-time curvature effects related to the fundamental question of the relationship between gravity, quantum physics and thermodynamics.
    
5. Investigation of tau lepton decays and processes of electron-positron annihilation into mesons including processes with three pseudoscalar mesons in the final state.
   
   Calculation of the contributions of the leading and following the leading logarithmic corrections to the processes of electron-positron annihilation, Bhabha scattering and muon-electron scattering studied in experiments at modern and future colliders, including the Super Charm-Tau Factory, FCC-ee, CEPC, etc.
   
   Obtaining an effective action of QCD at low energies, the constants of which are expressed in terms of parameters characterizing the explicit and spontaneous breaking of chiral symmetry.
   
   Calculation of masses, electromagnetic form factors, decay widths and other experimentally observed characteristics of mesons based on the new effective action of QCD at low energies. Finding the contributions describing the effects of a clear violation of aromatic symmetry which are not taken into account by the standard Nambu-Jona-Lasinio model.
   
   Calculation of the cross sections for the electron-positron annihilation into a proton-antiproton pair for a number of charmoniums (J/Ψ, Ψ(2S), χc (3556)) in the intermediate state for the conditions of the BES-III and PANDA experiments. Determination of the relative phases between the individual contributions of intermediate vector mesons and the electrodynamic channel.
   
   Determination of the contributions of the channels with charmoniums in the intermediate state to Drell-Yan-like processes with protons and nuclei in the initial state in the context of their study at the NICA collider.
   
   Study of neutrino-nucleus interactions within the models with running axial nucleon mass, superscaling and light meson production; application of the results to event simulation in the current neutrino experiments (NOvA, DUNE, and others).
   
   Global statistical analysis of electron scattering data on hydrogen and deuterium in order to refine the parameterizations of the electromagnetic form factors of the nucleon. Application of the results to neutrino oscillation experiments.
   
   Development of a model that implements the idea of loop generation of the hierarchical fermion spectrum of the Standard Model based on the corresponding flavor symmetry.
   
   Study of the behavior of the dressed neutrino propagator at short macroscopic baselines within the covariant quantum-field formalism with wave packets.
   
   Investigations of gravitational lensing and shadow formation for the Ruffini–Arguelles–Rueda model of dark matter.
   
   Finding constraints on the models of the Galactic Center and the center of the galaxy M87 from observations of their shadows and trajectories of bright stars.
   
   Development of a software package for selecting data from the TAIGA experiment to search for events co-located with ultra-high energy neutrinos registered by the IceCube and Baikal-GVD facilities and with gravitational-wave events registered by the LIGO and Virgo detectors.

Collaboration