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arXiv 2021年

作者： Lyubovitskij, Valery E. Wunder, Fabian Zhevlakov, Alexey S. Institut für Theoretische Physik Universität Tübingen Kepler Center for Astro and Particle Physics Auf der Morgenstelle 14 TübingenD-72076 Germany Departamento de Física Centro Científico Tecnológico de Valparaíso-CCTVal Universidad Técnica Federico Santa María Casilla 110-V Valparaíso Chile Department of Physics Tomsk State University Tomsk634050 Russia Bogoliubov Laboratory of Theoretical Physics Joint Institute for Nuclear Research Dubna141980 Russia Matrosov Institute for System Dynamics and Control Theory SB RAS Lermontov str. 134 Irkutsk664033 Russia

We discuss new ideas for consideration of loop diagrams and angular integrals in D-dimensions in QCD. In case of loop diagrams, we propose the covariant formalism of expansion of tensorial loop integrals into the orthogonal basis of linear combinations of external momenta. It gives a very simple representation for the final results and is more convenient for calculations on computer algebra systems. In case of angular integrals we demonstrate how to simplify the integration of differential cross sections over polar angles. Also we derive the recursion relations, which allow to reduce all occurring angular integrals to a short set of basic scalar integrals. All order Ε-expansion is given for all angular integrals with up to two denominators based on the expansion of the basic integrals and using recursion relations. A geometric picture for partial fractioning is developed which provides a new rotational invariant algorithm to reduce the number of denominators. © 2021, CC BY.

关键词： Expansion

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Constraints on CP-odd ALP couplings from EDM limits of fermions.

arXiv

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arXiv 2020年

作者： Kirpichnikov, D.V. Lyubovitskij, Valery E. Zhevlakov, Alexey S. Institute for Nuclear Research of the Russian Academy of Sciences Moscow117312 Russia Institut für Theoretische Physik Universität Tübingen Kepler Center for Astro and Particle Physics Auf der Morgenstelle 14 TübingenD-72076 Germany Departamento de Física y Centro Científico Tecnológico de Valparaíso-CCTVal Universidad Técnica Federico Santa María Casilla 110-V Valparaíso Chile Department of Physics Tomsk State University Tomsk634050 Russia Matrosov Institute for System Dynamics and Control Theory SB RAS Lermontov str. 134 Irkutsk664033 Russia

We discuss constraints on soft CP-violating couplings of axion-like particles (ALPs) with photon and fermions by using data on electric dipole moments (EDMs) of Standard Model (SM) particles. In particular, we derive bounds on CP-odd ALP-photon-photon coupling from data of the ACME Collaboration on electron EDM. We also discuss prospects of the Storage Ring experiment to constrain the ALP-photon-photon coupling from data on proton EDM. The regarding constraints from experimental bounds on the muon and neutron EDMs are weak. We set constraint on the CP-odd ALP coupling with electron and derive bounds on combinations of coupling constants, which involve soft CP-violating terms. Finally, we discuss a scenario of inducing of Yukawa-like interaction of SM fermions with ALP through the electro-weak symmetry breaking mechanism. Copyright © 2020, The Authors. All rights reserved.

关键词： Photons

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Deep inelastic e - τ and μ - τ conversion in the NA64 experiment at the CERN SPS

arXiv

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arXiv 2018年

作者： Gninenko, Sergei Kovalenko, Sergey Kuleshov, Serguei Lyubovitskij, Valery E. Zhevlakov, Alexey S. Institute for Nuclear Research Moscow117312 Russia Departamento de Fisica y Centro Científico Tecnológico de Valparaíso-CCTVal Universidad Técnica Federico Santa María Casilla110-V Chile Institut für Theoretische Physik Universität Tübingen Kepler Center for Astro and Particle Physics Auf der Morgenstelle 14 TübingenD-72076 Germany Department of Physics Tomsk State University Tomsk634050 Russia Tomsk State Pedagogical University Tomsk634061 Russia Matrosov Institute for System Dynamics and Control Theory SB RAS Lermontov str. 134 Irkutsk664033 Russia

We study the Lepton Flavor Violating (LFV) e(μ) - τ conversion in Deep Inelastic Scattering (DIS) of electrons (muons) on fixed-target nuclei. Our model-independent analysis is based on the set of low-energy effective four-fermion LFV operators composed of leptons and quarks with the corresponding mass scales Λkfor each operator. Using the estimated sensitivity of the search for this LFV process in events with large missing energy in the NA64 experiment at the CERN SPS, we derive lower limits for Λkand compared them with the corresponding limits existing in the literature. We show that the DIS e(μ) - τ conversion is able to provide a plenty of new limits as yet nonexisting in the literature. We also analyzed the energy spectrum of the final-state τ and discussed the viability of the observation of this process in the NA64 experiment and ones akin to it. The case of polarized beams and targets is also discussed. Copyright © 2018, The Authors. All rights reserved.

关键词： Distribution functions

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Lepton flavor violating dark photon

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Physical Review D 2024年第1期109卷 015015-015015页

作者： Alexey S. Zhevlakov Dmitry V. Kirpichnikov Valery E. Lyubovitskij Bogoliubov Laboratory of Theoretical Physics JINR 141980 Dubna Russia Matrosov Institute for System Dynamics and Control Theory SB RAS Lermontov str. 134 664033 Irkutsk Russia Institute for Nuclear Research of the Russian Academy of Sciences 117312 Moscow Russia Institut für Theoretische Physik Universität Tübingen Kepler Center for Astro and Particle Physics Auf der Morgenstelle 14 D-72076 Tübingen Germany Departamento de Física y Centro Científico Tecnológico de Valparaíso-CCTVal Universidad Técnica Federico Santa María Casilla 110-V Valparaíso Chile Millennium Institute for Subatomic Physics at the High-Energy Frontier (SAPHIR) of ANID Fernández Concha 700 Santiago Chile

We study the possible impact of dark photons on lepton flavor phenomenology. We derive the constraints on nondiagonal dark photon couplings with leptons by analyzing corresponding contributions to lepton anomalous magnetic moments, rare lepton decays, and the prospects of fixed-target experiments aimed at searching for light dark matter based on missing energy/momentum techniques.

关键词： Extensions of gauge sector Phenomenology Weakly interacting massive particles Hypothetical gauge bosons

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Test of vector portal with dark fermions in the charge-exchange reactions in the NA64 experiment at CERN SPS

arXiv

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arXiv 2023年

作者： Gninenko, Sergei N. Kirpichnikov, Dmitry V. Kuleshov, Sergey Lyubovitskij, Valery E. Zhevlakov, Alexey S. Institute for Nuclear Research The Russian Academy of Sciences Moscow117312 Russia of ANID Fernández Concha 700 Santiago Chile Center for Theoretical and Experimental Particle Physics Facultad de Ciencias Exactas Universidad Andres Bello Fernandez Concha 700 Santiago Chile Departamento de Física y Centro Científico Tecnológico de Valparaíso-CCTVal Universidad Técnica Federico Santa María Casilla 110-V Valparaíso Chile Bogoliubov Laboratory of Theoretical Physics JINR Dubna141980 Russia Matrosov Institute for System Dynamics and Control Theory SB RAS Lermontov str. 134 Irkutsk664033 Russia

We consider an experiment to search for dark sector particles in dark photon kinetic mixing model by analyze invisible and semi-invisible decays of neutral mesons M0 = π0, η, η′, ω, f2(1270), produced in the NA64 experiment at the CERN SPS. The approach proposed in Ref. [1] is to use the charge-exchange reactions π− + (A, Z) → M0 + (A, Z − 1);M0 → invisible or semi-invisible of high-energy pions (or kaons) at a nuclei target as a source of M0s, which subsequently decay invisibly into dark sector. This reaction chain would lead to a striking signature of the signal event - the complete disappearance of the beam energy in the setup. Using data obtained from the study of charge-exchange reactions at IHEP (Protvino) and Fermilab (Batavia) we show that the integral cross sections σ for production of the neutral mesons M0 are slightly deviate from phenomenological formula σ ∼ Z2/3, where Z is the nuclei charge. In particular, we present the formulas for the differential and integral sections that explicitly depend on the Mandelstam and Z variables. Derived formulas are used to predict the cross sections as a function of beam energy for several target nuclei, and to estimate the projection sensitivity for the proposed search for the M0 → semi-invisible and M0 → invisible decays through the vector portal to dark sector. Sensitivity to different semi-invisible decay modes of neutral pseudoscalar mesons is studied. © 2023, CC0.

关键词： Hadrons

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On the analytic solvability of a special boundary value problem for the nonlinear heat equation

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AIP Conference Proceedings 2017年第1期1915卷

作者： A. L. Kazakov A. A. Lempert P. A. Kuznetsov 1Institute of Engineering Science Ural Branch of the Russian Academy of Sciences 34 Komsomolskaya St. Ekaterinburg 620049 Russia 2Matrosov Institute for System Dynamics and Control Theory Siberian Branch of the Russian Academy of Sciences 134 Lermontova St. 664033 Irkutsk Russia

In the article we develop an approach to the study of nonlinear problems of mathematical physics, proposed in A. F. Sidorov’s school of thought, and apply it to solving boundary value problems with degeneracy for the nonlinear heat (porous medium) equation. The essence of the approach is that the solution of problems is constructed in the form of multiple power series. The convergence of the constructed series is proved by the majorant method. It allows us to propose the existence and uniqueness theorem, which is analogous to the Cauchy-Kovalevskaya theorem for the considered problem. A constructive scheme for finding the coefficients of the series is proposed. A special feature of the study is that the boundary condition is given on a moving closed manifold.

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A heat wave problem for a degenerate nonlinear parabolic equation with a specified source function

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AIP Conference Proceedings 2018年第1期2053卷

作者： A. L. Kazakov P. A. Kuznetsov L. F. Spevak 1Matrosov Institute for System Dynamics and Control Theory Siberian Branch of the Russian Academy of Sciences 134 Lermontova St. 664033 Irkutsk Russia 2Institute of Engineering Science Ural Branch of the Russian Academy of Sciences 34 Komsomolskaya St. 620049 Ekaterinburg Russia

A nonlinear parabolic heat conduction equation with a source is discussed, for which solutions of the heat wave propagating against a cold background at a finite velocity are studied. A new theorem of the existence and uniqueness of heat waves is proved. A particular case is studied in detail, when the heat wave is invariant and its construction reduces to solving an ordinary differential equation. For the numerical construction of invariant heat waves, an algorithm based on the boundary element method is proposed. Test examples are solved.

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A numerical solution to the two-dimensional nonlinear degenerate heat conduction equation with a source

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AIP Conference Proceedings 2020年第1期2315卷

作者： A. L. Kazakov L. F. Spevak O. A. Nefedova 1Institute of Engineering Science Ural Branch of the Russian Academy of Sciences 34 Komsomolskaya St. Ekaterinburg 620049 Russia 2Matrosov Institute for System Dynamics and Control Theory Siberian Branch of the Russian Academy of Sciences 134 lermontov St. Irkutsk 664033 Russia

The paper develops an algorithm for solving the two-dimensional nonlinear degenerate parabolic heat conduction equation with a source depending on required function, with a specified law of heat wave front motion. The algorithm based on the boundary element method is implemented in the form of a program. To verify it, we use exact solutions the construction of which is reducible to solving a Cauchy problem for ordinary differential equations with a singularity before the highest derivative. The solutions to the Cauchy problem are constructed in the form of power series with recurrently computed coefficients (with a proof of the statement providing its convergence) and by the boundary element method.

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Numerical study of travelling wave type solutions for the nonlinear heat equation

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AIP Conference Proceedings 2019年第1期2176卷

作者： A. L. Kazakov L. F. Spevak 1Institute of Engineering Science Ural Branch of the Russian Academy of Sciences 34 Komsomolskaya St. Ekaterinburg 620034 Russia 2Matrosov Institute for System Dynamics and Control Theory Siberian Branch of the Russian Academy of Sciences 134 Lermontov St. Irkutsk 664033 Russia

The problem of constructing solutions to the nonlinear heat equation with power nonlinearity is considered. The solutions have the form of a traveling wave and simulate the propagation of disturbances over a cold background with a finite velocity. It is shown that the construction can be reduced to the Cauchy problem for an ordinary second- order differential equation with a singularity multiplying the highest derivative. Its solutions are constructed using the boundary element method based on the dual reciprocity method. A computational experiment is carried out. The results are compared with the solutions of the same problems by the power series method. The calculations have shown the correctness of the developed boundary element algorithm and its advantage compared to the power series segments and the step-by-step method previously proposed by the authors.

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Solving a degenerate nonlinear parabolic equation with a specified source function by the boundary element method

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AIP Conference Proceedings 2017年第1期1915卷

作者： L. F. Spevak A. L. Kazakov 1Institute of Engineering Science Ural Branch of the Russian Academy of Sciences 34 Komsomolskaya str. 620049 Ekaterinburg Russia 2Matrosov Institute for System Dynamics and Control Theory Siberian Branch of the Russian Academy of Sciences 134 Lermontov str. 664033 Irkutsk Russia

A degenerate nonlinear parabolic-type equation with a specified source function is solved. Boundary value problems for various kinds of boundary conditions are considered. Solution algorithms based on the boundary element method are constructed. Some examples are discussed. The comparison of the obtained BEM solutions with known exact solutions gives good results.

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