Fundamental Interactions of Fields and Particles

Participating Countries and International organizations:
Argentina, Armenia, Azerbaijan, Belarus, Bulgaria, Canada, CERN, Chile, China, Czech Republic, Finland, France, Georgia, Germany, 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 main results in the current year:

• Calculation of two-point two-loop Feynman diagrams containing an elliptic structure in the form of combinations of Goncharov and elliptic polylogarithms.
   
  Derivation of hypergeometric functions of one and several variables in terms of iterated integrals in the frames of the fractional derivation technique. Search for an iterated integral representation of a class of special functions for Feynman diagrams.
   
  Evaluation of the renormalon contributions to two-point correlators of composite quark currents in QCD.
   
  Study of the α_s² contribution to the hadronic structure function of Drell-Yan processes in the framework of perturbative QCD.
   
  Study of the critical behavior of 3-dimensional QCD and its supersymmetric generalization in the first two orders of the 1/N_f  expansion. Study of the critical behavior of 3-dimensional QED in the first three orders of the 1/N_f expansion through the anomalous dimension of the fermion mass.
   
  Study of the role of axion-like particles in experiments of electron-nucleon scattering. The role of New physics in anomalous magnetic moments of leptons and electric dipole moments of nucleons.
   
  Development of a semi-analytical approach for the evolution of transverse-momentum-dependent parton densities to the next-to-leading order.
   
  Construction of a semi-analytical approach for double parton distributions.
   
  Establishment of the relation between effective cross sections of double parton scattering
  in photon-hadron and hadron-hadron collisions.
   
• Calculation of pion electromagnetic form factors in the low and (or) moderate energy regime, extending the domain of applicability of LCSR, in the order O(α_s) for comparison with precision Jlab experiments.
   
  Revision of distribution amplitudes (leading twist) of (pseudo)scalar and (longitudinal and transverse) vector mesons within QCD SRstaking into account new QCD corrections obtained for all of its components.
   
  Theoretical analysis and a development of propositions for setting up an experiment for  measurement of tensor electric and magnetic polarizabilities of the deuteron.
   
  Investigation of the properties and energy dependence ofnew effects, which were determined in the experimental data by the TOTEM Collaboration at an energy of 13 TeV.Determination of the properties of the long-range hadron potential,which lead to peculiar properties of the differential crosssections of  hadron-hadron elastic scattering.
   
  Study of the generalized transverse momentum dependent distributions by restoring the Sivers function in an alternative way, involving thenew-found additional contribution in the inverse Radon transforms.
   
  Investigation of the role of the gluon poles in the two-photon process producing transverse polarized hadrons with  different fragmentation functions.
   
  Investigation of the role of the twist-3 quark-gluon-quark correlation function in studying the hadron structure.
   
  Study of the sum rules for hadron structure functions and fragmentation functions in quantum chromodynamics (QCD) with the use of the generalized truncated Mellin moments approach (TMM).
   
  Study of the fragmentation functions in the inclusive pion and kaon production in proton-proton collisions in the NICA project.
   
  Numerical optimization of perturbative series for observables using the renormalization group in QCD. Applications of the DIS sum rules and comparison with  experimental data.
   
  Study of Generalized Parton Distribution (GPDs) properties and GPDs effects in meson leptoproduction at modern colliders.
   
  Study of the effects of magnetic monopoles and instantons in QCD on the hadron properties by simulations of lattice gauge theory. In particular, precise estimation of the number of instantons and anti-instantons, masses of the charm quark, eta prime and baryons, and the decay constants of mesons and baryons. Determination of the quantitative relations between the density of the number of instantons and anti-instantons and these observables. Investigation of possible detection of the monopole and instanton effects in experiments.
  
  
• Motivated by the first search for the rare charged-current B-meson decay into four-leptons, B →l⁺l^–l'ν_l', it is planned to calculate the decay amplitude, the double differential distribution and branching fraction.
   
  Еlaboration of semianalytical methods for computation of bound statesspectral functions in effective meson and quark-meson models by means of the nonperturbative renormalization group approach and their furtherimplementation for calculation of decay widths and study of massgeneration mechanisms for light mesons.
  
  Study the role of leptoquarks in explanation of the flavor anomalies observed in precision experiments.
  
  Derivation of the effective Lagrangian of the Nonrelativistic Quantum Electrodynamics (NRQED) that takes into account all interactions necessary for calculationof the bound states of Coulomb systems with a precision up to and included the order of mα⁷. Calculation of the hyperfine splitting of spectral lines in rho-vibrational transitions of molecular hydrogen ions with a relative accuracy of 10⁻⁷, which is necessary for the analysis of new precision experiments. Improvement ofthe values ​​of the fundamental constants of atomic physics (Rydberg constant, the proton-to-electron mass ratio) by imposing more stringent restrictions on the interaction potentials of the "fifth" force.
   
  Analysis of possibilities for a search for dark matter axions in spin experiments in storagerings.
   
• Calculation of the dependence of the critical temperaturesof confinement/deconfinement and chiral symmetry breaking/restoration transitions on theangular velocity in rotating QCD within lattice simulation.
   
  Study of the anisotropy of the static quark-antiquark potential in the presence of rotation. Calculation of the moment of inertia of rotating gluon plasma in rotating lattice QCD.
   
  Investigation of the effect of quantum anomalies on transport phenomena in a vortical relativistic fluid containing also elementary particles with higher spins in external fields. Investigation of anomaly induced quantized vortices in mesonic superfluids and their effect on baryon polarization.
   
  Improvement of the prediction of the global Λ polarization in the NICA-FAIR-HADES energy range, including its centrality and rapidity dependence. Calculation of splitting of the Λ-antiΛ polarization within the thermodynamic approach including splitting induced by the meson field and the recently proposed thermal shear contribution.
   
  Modeling of light-nuclei production in heavy-ion collisions in the SPS-RHIC energy range within the thermodynamic approach based on the three-fluid dynamical model and a comparison of the results with experimental data.
   
  Study of a response of neutral and charged Fermi-systemswith condensates of the vector fields, such as the triplet pairing, on the rotation. Special attention will be paid to the consideration of the possibility of self-rotation in nuclear systems.
   
  Study of the influence of the effects of polarization of the dense nuclear matter on the properties of excitations with quantum numbers of the pion and on their s-p condensation in the framework of the quasiparticle approximation and beyond it. The results will be applied to describe proto-neutron stars and nucleus-nucleus collisions.
   
  Calculation of the thermodynamic potential and investigation of the superfluid / superconducting phase transition andscaling in SU(N) symmetric equilibrium systems of ultracold fermions in the framework of the nonperturbative renormalization group.
   
  Demonstration that the origin of the correlations between low and high-p_t flow components in peripheral lead-lead collisions is traced to correlations of particles injets.
   
  Demonstration that the third eccentricity has a pure fluctuation originand is substantially dependent on the size of the overlap area only, whilethe second eccentricityis mainly related to the average collisiongeometry.
   
  Study of the propagation of nonlinear waves in the hot, viscous, nonextensive quark-gluon plasma.
   
  Analytical calculation of quantum Tsallis thermodynamic variables. Derivation of the Tsallis-like quantum single particle distributions (to be used in high-energy collision physics) from nonextensive Green's functions. Comparison of them with the results obtained using the Tsallis statistical mechanics.
   
  Preliminary magneto hydrodynamic simulation at nonzero conductivity in the context of heavy ion collisions. 

• Preparation of a research program for future electron-positron colliders, including projects of the super charm-tau factory and the FCC-ee. High-precision theoretical predictions for the processes of particle interaction at these colliders and analysis of the effects associated with the polarization of the initial beams and produced tau leptons.
   
  Calculation of the widths of tau lepton decays into hadrons and cross-sections of the electron-positron annihilation into hadrons in the framework of the Nambu-Jona-Lasinio model including rectification of the results for the tau lepton decays into hadrons obtained earlier with taking into account meson interaction in the final states.
   
  Development of a simulation package for production of pions generated in interactions of neutrinos and charged leptons with nucleons within the framework of the GENIE neutrino generator. Implementation of a new model (the so-called MK model) of resonant production of pions and improvement of the earlier models based on the SU(6) relativistic quark model. Adjustment of the parameters of the models with inclusion of modern acceleration data.
  
  Exploiting of the quasidirac neutrino scheme for conclusions on the potential of neutrino oscillations and double-beta decay experiments to determine absolute scale of neutrino masses.
   
  Investigation of the corrections to the reactor antineutrino flux by considering the impact of new atomic and nuclear effects on the corresponding differential characteristics.

Collaboration