Kirill Tuchin
Electromagnetic field of a fast electric charge in nuclear matter with spatially uniform but random topological charge density is derived. A useful approximation is developed for the relativistic heavy-ion collisions.
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We estimate the electromagnetic effect of the spectator charge on the momentum spectra of $π^+$ and $π^-$ produced in peripheral Pb+Pb collisions at SPS energies. We find that the effect is large and results in strongly varying structures in the $x_F$ dependence of the $π^+/π^-$ ratio, especially at low transverse momenta where a deep valley in the above ratio is predicted at $x_F \sim$ 0.15 -- 0.20. It appears that the effect depends on initial conditions. Thus, it provides new information on the space and time evolution of the non-perturbative pion creation process.
We compute electromagnetic fields created by a relativistic charged spin-half particle in empty space at distances comparable to the particle Compton wavelength. The particle is described as a wave packet evolving according to the Dirac equation. It produces the electromagnetic field that is essentially different from the Coulomb field due to the quantum diffusion effect.
The generation of narrow beams of high-energy positrons (electrons) in the process of resonant photogeneration of ultrarelativistic electron-positron pairs by high-energy gamma quanta in the field of the nucleus and a strong electromagnetic wave is theoretically predicted. It is shown that if the energy of the initial gamma quanta significantly exceeds the characteristic energy of the process, then ultrarelativistic positrons (for channel A) or electrons (for channel B) are emitted with energies very close to the energy of gamma quanta. Moreover, the resonant differential cross-section of such…
Heavy quarks are valuable probes of the electromagnetic field and the initial condition of the quark-gluon plasma (QGP) matter produced in high-energy nuclear collisions. Within an improved Langevin model that is coupled to a (3+1)-dimensional viscous hydrodynamic model, we explore the origin of the directed flow coefficient ($v_1$) of heavy mesons and their decay leptons, and its splitting ($Δv_{1}$) between opposite charges. We find that while the rapidity dependence of the heavy flavor $v_1$ is mainly driven by the titled energy density profile of the QGP with respect to the longitudinal di…
Generation of narrow beams of ultrarelativistic positrons (electrons) in the resonant strong electromagnetic field-assisted Breit-Wheeler process
本文理论上研究了低于临界Schwinger场强下的共振外场辅助Breit-Wheeler过程，通过分析共振运动学与微分截面，预测了高能gamma量子产生超相对论正负电子窄束，其概率显著高于非共振过程。
Electromagnetic measurement of the temperature of quark-gluon plasma produced in central ultrarelativistic nuclear collisions
本文针对中心超相对论核碰撞产生的夸克胶子等离子体温度测量问题，通过最小程度建模其膨胀，结合光子能量谱斜率实现温度映射，同时指出需应对非热源污染的挑战。
An extraordinary strong magnetic field, $eB_0 \approx 10^{18}$ Gauss, is expected to be generated in non-central ultrarelativistic heavy ion collisions and it is envisaged to induce several effects on hot QCD matter including the possibility of local parity and local parity and charge conjugation symmetry violations. A direct signature of such e.m. fields and a first quantitative measurement of its strength and lifetime are still missing. We point out that both the mean value of leptonic invariant mass of $Z^0$ boson, reconstructed by its decaying lepton pairs, and the relative width are modif…
We present a new approach for calculating electromagnetic excitation of nuclei as well as probabilities of emission and distributions of neutrons from decays of excited nuclear systems for ultrarelativistic, ultraperipheral heavy ion collisions. Excitation functions for $γ$ + Pb $\to$ Pb$^*$ are parametrized using physics-motivated components: excitation of giant resonances, quasi-deuteron absorption mechanism, excitation of nucleon resonances as well as high-energy dissociation of protons and neutrons. Neutron emission (up to 10 neutrons) from low-energy excitations of $^{208}$Pb is modelled …
The feasibility of obtaining exact analytical results in the realm of QED in the presence of a background electromagnetic field is almost exclusively limited to a few tractable cases, where the Dirac equation in the corresponding background field can be solved analytically. This circumstance has restricted, in particular, the theoretical analysis of QED processes in intense laser fields to within the plane-wave approximation even at those high intensities, achievable experimentally only by tightly focusing the laser energy in space. Here, within the Wentzel-Kramers-Brillouin (WKB) or eikonal a…
We estimate the electromagnetic effect of the spectator charge on the momentum spectra of charged pions produced in peripheral Pb+Pb collisions at SPS energies. We find a large effect which results in strongly varying structures in the $x_F$ dependence of the $π^+/π^-$ ratio, especially at low transverse momenta where a deep valley in the above ratio is predicted at $x_F \sim$ 0.15 -- 0.20. The effect depends on initial conditions. Thus, it provides new information on the space and time evolution of the non-perturbative pion creation process.
We construct analytic (3+1)-dimensional inhomogeneous and topologically non-trivial pion systems using chiral perturbation theory. We discuss the effect of isospin asymmetry with vanishing electromagnetic interactions as well as some particular configurations with non-vanishing electromagnetic interactions. The inhomogeneous configurations of the pion fields are characterized by a non-vanishing topological charge that can be identified with baryons surrounded by a cloud of pions. This system supports a topologically protected persistent superflow. When the electromagnetic field is turned on th…
HIJING generator simulation of nucleus-nucleus collisions at ultrarelativistic energies are presented. Is shown, that the global characteristics of nucleus-nucleus collisions, such as of distribution of a charge multiplicity, total and electromagnetic transverse energy over pseudorapidity are rather sensitive to some predictions of formation models of high-exited nuclear medium, namely parton energy losses in dense nuclear matter. This losses results to appearance of a broad maximum in global variable distributions over pseudorapidity. The most profound of this effect occurs at central heavy i…
The actual theoretical research investigates the resonant spontaneous bremsstrahlung (RSB) of ultrarelativistic electrons under the condition of scattering on a nucleus in the field of a weak electromagnetic wave. The progression of the functional mechanism indicates the transformation of the intermediate virtual electron into the real particle state. As a result, the initial second order process with accordance to the fine structure constant in the light field productively splits into two consequent first order formations: the laser-stimulated Compton effect and the laser-assisted scattering …
We compute the electromagnetic field created by an ultrarelativistic charged particle in vacuum at distances comparable to the particle Compton wavelength. The wave function of the particle is governed by the Klein-Gordon equation, for a scalar particle, or the Dirac equation, for a spin-half particle. The produced electromagnetic field is essentially different in magnitude and direction from the Coulomb field, induced by a classical point charge, due to the quantum diffusion effect. Thus, a realistic computation of the electromagnetic field produced in heavy-ion collisions must be based upon …
We propose the experiments on the collision of laser light and high intensity electromagnetic pulses generated by relativistic flying mirrors, with electron bunches produced by a conventional accelerator and with laser wake field accelerated electrons for studying extreme field limits in the nonlinear interaction of electromagnetic waves. The regimes of dominant radiation reaction, which completely changes the electromagnetic wave-matter interaction, will be revealed in the laser plasma experiments. This will result in a new powerful source of ultra short high brightness gamma-ray pulses. A po…
The radiative decay of the massive neutrino $ν_i \rightarrow ν_j γ$ is investigated in the framework of the Standard Model in external electromagnetic fields of various configurations: constant crossed field, constant uniform magnetic field, plane monochromatic wave's field. The effect of significant enhancement of the neutrino decay probability by the external field (electromagnetic catalysis) is discussed. An especially strong enhancement occurs in the case of the ultrarelativistic neutrino decay, since in this case the decay probability does not contain suppression caused by the smallness o…
Quantum entanglement of final particle states in the resonant trident pair production in a strong electromagnetic wave
本文研究强电磁波中共振三叉戟对产生，揭示其分裂为Compton与Breit-Wheeler过程，并分析末态粒子能量、出射角的两类量子纠缠及概率增强。
The possibility of radiation of high-energy gamma quanta with energies of the order of 100 GeV by ultrarelativistic electrons on nuclei in strong X-ray fields with intensities up to $\sim 10^{27}\ \text{Wcm}^{-2}$ has been theoretically studied. It is shown that this effect can be realized under special experimental conditions in the process of resonant spontaneous bremsstrahlung radiation of ultrarelativistic electrons on nuclei in an external electromagnetic field. These special experimental conditions determine the characteristic energy of the electrons. This characteristic energy should be…
The solution of the plasmon problem and the subsequent development of an effective field theory approach to ultrarelativistic plasmas are reviewed. The effective lagrangians that summarize collective effects in ultrarelativistic quark-gluon and electron-photon plasmas are presented. A generalization that describes an electromagnetic plasma at all temperatures and densities is proposed.
A status report of utilizing soft electromagnetic radiation (aka thermal photons and dileptons) in the diagnosis of strongly interacting matter in ultrarelativistic heavy-ion collisions is given. After briefly elaborating on relations of the electromagnetic spectral function to chiral symmetry restoration and the transition from hadron to quark degrees of freedom, various calculations of electromagnetic emission rates in the hadronic and quark-gluon plasma phases of QCD matter are discussed. This, in particular, includes insights from recent thermal lattice QCD computations. Applications to di…
Thermal pressure on ultrarelativistic bubbles from a semiclassical formalism
该研究采用半经典电流辐射（SCR）形式，研究早期宇宙一阶电弱相变中超相对论运动泡壁的热压等问题，分析了突变/渐变减速模型下辐射谱与壁厚的关联及热压标度规律。
We present recent results on bulk observables and electromagnetic probes obtained using a hybrid approach based on the Ultrarelativistic Quantum Molecular Dynamics transport model with an intermediate hydrodynamic stage for the description of heavy-ion collisions at AGS, SPS and RHIC energies. After briefly reviewing the main results for particle multiplicities, elliptic flow, transverse momentum and rapidity spectra, we focus on photon and dilepton emission from hot and dense hadronic matter.
The radiative decay of ultrarelativistic massive neutrino $ν_i \rightarrow ν_j γ$ is investigated in electromagnetic fields in the framework of the Standard Model with lepton mixing. Estimates of the decay probability and ``decay cross-section'' for accelerator neutrinos of high energies in the electric field of nucleus permit one to discuss the general possibility of carrying out the neutrino experiment. Such an experiment could give unique information on mixing angles in the lepton sector of the Standard Model which would be almost independent of the specific neutrino masses.
The radiative decay of the massive neutrino $ν_i \rightarrow ν_j γ( m_i > m_j )$ in the external electromagnetic field is analyzed in detail in the framework of the standard model with lepton mixing. It is shown, that a sort of a catalysis of the neutrino radiative decay takes place. The effect of catalysis is significant in the strong electromagnetic fields ($F \gg B_e = m^2_e / e \simeq 4.41 \cdot 10^{13}$ G) ; it is more pronounced in the case of the decay of the ultrarelativistic neutrino $(E_ν \gg m_ν)$, even in a relatively weak electromagnetic field ($F \ll m^2_e/e$).
The resonant photoproduction of ultrarelativistic electron-positron pairs (PPP) in a nuclear field and a weak laser field is theoretically studied. Under resonance conditions, the intermediate virtual electron (positron) in the laser field becomes a real particle. As a result, the initial process of the second order in the fine structure constant in the laser field effectively reduces into two successive processes of the first order: single-photon production of electron-positron pair in a laser field (laser-stimulated Breit-Wheeler process) and laser-assisted process of electron (positron) sca…
Neutrino Electromagnetic Properties
本文系统回顾了中微子电磁性质的理论框架、实验限制及其在天体物理和惰性中微子磁矩门户中的现象学意义。
Charged particles accelerated by electromagnetic fields emit radiation, which must, by the conservation of momentum, exert a recoil on the emitting particle. The force of this recoil, known as radiation reaction, strongly affects the dynamics of ultrarelativistic electrons in intense electromagnetic fields. Such environments are found astrophysically, e.g. in neutron star magnetospheres, and will be created in laser-matter experiments in the next generation of high-intensity laser facilities. In many of these scenarios, the energy of an individual photon of the radiation can be comparable to t…
Exact solution of the DeWitt-Brehme-Hobbs equation in copropagating electromagnetic and gravitational waves
本文研究了带电质量在共传播的电磁和引力波中的运动，推导了德威特-布雷姆-霍布斯方程的第一个精确解析解，并探讨了引力波对电磁辐射反应效应的影响。
Partonic matter produced in the early stage of ultrarelativistic nucleus-nucleus collisions is assumed to be composed mainly of gluons, and quarks and antiquarks are produced at later times. To study the implications of such a scenario, the dynamical evolution of a chemically nonequilibrated system is described by the ideal (2+1)-dimensional hydrodynamics with a time dependent (anti)quark fugacity. The equation of state interpolates linearly between the lattice data for the pure gluonic matter and the lattice data for the chemically equilibrated quark-gluon plasma. The spectra and elliptic flo…
The behaviour of electromagnetic waves propagating through an electroweak homilia string network is examined. This string network is topologically stable as a cosmic texture, and is characterized by the spatial variation of the isospin rotation of the Higgs field. As a consequence the photon field couples to the intermediate vector bosons, producing a finite range electromagnetic field. It is found that the propagation speed of the photon depends on its polarization vector, whence an homilia string network acts as a birefringent medium. We estimate the birefringent scale for this texture and s…
The existence of topological solutions and axial anomaly open a possibility of P and CP violation in QCD. For a reason that has not yet been established conclusively, this possibility is not realized in strong interactions - the experimental data indicate that a global P and CP violation in QCD is absent. Nevertheless, the fluctuations of topological charge in QCD vacuum, although not observable directly, are expected to play an important role in the breaking of $U_A(1)$ symmetry and in the mass spectrum and other properties of hadrons. Moreover, in the presence of very intense external electr…
Radiation reaction is the influence of the electromagnetic field emitted by a charged particle on the dynamics of the particle itself. Here we report experimental radiation emission spectra from ultrarelativistic positrons in silicon in a regime where both quantum and radiation-reaction effects dominate the dynamics of the positrons. We found that each positron emits multiple photons with energy comparable to its own energy, revealing the importance of quantum photon recoil. Moreover, the shape of the emission spectra indicates that photon emissions occur in a nonlinear regime where positrons …
A general technique to analyze the classical interaction between ideal topological insulators, and electromagnetic sources and fields, has been previously elaborated. Nevertheless it is not immediately applicable in the laboratory as it fails to describe real ponderable media. In this work we provide a description of real topologically insulating materials taking into account their dielectric and magnetic properties. For inhomogeneous permittivity and permeability, the problem of finding the Green's function must be solved in an ad hoc manner. Nevertheless, the physically feasible cases of pie…
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