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Yu. A. Simonov

Publications and source records attributed to Yu. A. Simonov.

At least 73 records · Page 4Linked to original sources
arXiv2013

The quark-hadron thermodynamics in magnetic field

Nonperturbative treatment of quark-hadron transition at nonzero temperature T and chemical potential mu in the framework of Field Correlator Method is generalized to the case of nonzero magnetic field B. A compact form of the quark pressure for arbitrary B, mu, T is derived. As a result the transition temperature is found as a function of B and mu, which depends on only parameters: vacuum gluonic condensate G_2 and the field correlator D_1^E(x), which defines the Polyakov loops and it is known both analytically and on the lattice. A moderate (25%) decrease of T_c(mu=0) for eB changing from zero to 1 GeV^2 is found. A sequence of transition curves in the (mu, T) plane is obtained for B in the same interval, monotonically decreasing in scale for growing B.

hep-ph↗
arXiv2013

Magnetic test of chiral dynamics in QCD

Strong magnetic fields in the range $ eB\gg m^2_π$ effectively probe internal quark structure of chiral mesons and test basic parameters of chiral theory, such as $\lan\bar q q\ran, f_π$. We argue on general grounds that $\lan\bar q q\ran$ should grow linearly with $eB$ when charged quark degrees of freedom come into play. To make explicit estimates we extend previously formulated chiral theory, including quark degrees of freedom, to the case of strong magnetic fields and show that the quark condensate $|\lan \bar q q\ran|_{u,d}$ grows quadratically with $eB$ for $eB\la 0.2$ GeV$^2$ and linearly for higher field values. These results agree quantitatively with recent lattice data and differ from $χPT$ predictions.

hep-ph↗
arXiv2013

Magnetic focusing in atomic, nuclear and hadronic processes

Processes with oppositely charged spinor particles in initial and/or final states in homogeneous magnetic field B are subject to focusing effects in their relative motion, which yield the amplifying factors in probabilities growing as $eB$. In addition the increasing energy of some Landau levels influences the phase space. As a result some processes in the proper spin states can be enlarged as $\sim \frac{eB}{κ^2}$, where $κ^2$ is the characteristic 2d phase space factor available without magnetic field. Several examples, including neutron $β$ decay, positronium decay and $e^+e^-$ pair production, are quantitatively considered.

hep-ph↗
arXiv2013

Magnetic Field Focusing of Hyperfine Interaction in Hydrogen

We find a new correction to the hydrogen atom ground state hyperfine energy levels splitting in magnetic field. It can be interpreted as magnetic focusing of the wave function at the origin. The effect might be within the reach of experiment.

hep-ph↗
arXiv2013

Nambu-Goldstone mesons in strong magnetic field

We study the q \bar q structure embedded in chiral mesons in response to external magnetic fields, using the chiral Lagrangian with q \bar q degrees of freedom derived earlier. We show that GMOR relations hold true for neutral chiral mesons, while they are violated for the charged ones for eB>sigma=0.2 GeV^2. The standard chiral perturbation theory also fails in this region. Masses of pi^+ and pi^0 mesons are calculated and compared to lattice data.

hep-ph↗
arXiv2013

Spin interactions in mesons in strong magnetic field

Spin interactions in relativistic quark-antiquark system in magnetic field is considered in the framework of the relativistic Hamiltonian, derived from the QCD path integral. The formalism allows to separate spin-dependent terms from the basic spin-independent interaction, contained in the Wilson loop, and producing confining and gluon exchange interaction. As a result one obtains relativistic spin-spin interaction $V_{ss}$, generalizing its nonrelativistic analog. It is shown, that in large magnetic field $eB, V_{ss}$ modifies and produces hyperfine shifts which grow linearly with $eB$ and preclude the use of perturbation theory. We also show, that tensor forces for $eB \neq 0$ are active in all meson states, but do not grow with $eB$

hep-ph↗
arXiv2013

Meson Spectrum in Strong Magnetic Fields

We study the relativistic quark-antiquark system embedded in magnetic field. The Hamiltonian containing confinement, one gluon exchange and spin-spin interaction is derived. We analytically follow the evolution of the lowest meson states as a functions of MF strength. Calculating the one gluon exchange interaction energy and spin-spin contribution we have observed, that these corrections remain finite at large magnetic fields, preventing the vanishing of the total rho-meson mass at some B_crit, as previously thought. We display the rho masses as functions of magnetic field in comparison with recent lattice data.

hep-ph↗
arXiv2013

Magnetic moments of mesons

Magnetic moments of charged and neutral mesons are calculated with the use of the relativistic Hamiltonian derived from the path integral form of the $q_1\bar q_2$ Green's function. The magnetic moments are shown to be expressed via the average quark energies which are defined by the fundamental quantities: the string tension $σ$, the current quark masses, and the strong coupling constant $α_s$. Resulting values for vector, axial, and tensor light and $K$ mesons agree well with all available lattice data.

hep-ph↗
arXiv2013

Relativistic path integral and relativistic Hamiltonians in QCD and QED

The proper-time 4d path integral is used as a starting point to derive the new explicit parametric form of the quark-antiquark Green's function in gluonic and QED fields, entering as a common Wilson loop. The subsequent vacuum averaging of the latter allows to derive the instantaneous Hamiltonian. The explicit form and solutions are given in the case of the $q\bar q$ mesons in magnetic field.

hep-ph↗
arXiv2012

Microscopic study of the string breaking in QCD

Theory of strong decays defines in addition to decay widths, also the channel coupling and the mass shifts of the levels above the decay thresholds. In the standard decay models of the 3P0 type the decay vertex is taken to be a phenomenological constant "gamma" and such a choice leads to large mass shifts of all meson levels due to real and virtual decays, the latter giving a divergent contribution. Here we show that taking the microscopic details of decay vertex into account, one obtains new string width coefficient, which strongly suppresses virtual decay contribution. In addition for a realistic space structure of the decay vertex of highly excited states, the decay matrix elements appear to be strongly different from those, where the constant "gamma" is used. From our analysis also follows that so-called flattening potential can imitate the effects of intermediate decay channels.

hep-ph↗
arXiv2012

Asymptotic freedom in strong magnetic field

Perturbative gluon exchange interaction between quark and antiquark, or in a 3q system, is enhanced in magnetic field and may cause vanishing of the total q\bar q or 3q mass, and even unlimited decrease of it - recently called the magnetic collapse of QCD. The analysis of the one-loop correction below shows a considerable softening of this phenomenon due to q\bar q loop contribution, similarly to the Coulomb case of QED, leading to approximately logarithmic dumping of gluon exchange interaction at large magnetic field.

hep-ph↗
arXiv2012

Quark-Antiquark System in Ultra-Intense Magnetic Field

We study the relativistic quark-antiquark system embedded in magnetic field (MF). The Hamiltonian containing confinement, color Coulomb and spin-spin interaction is derived. We analytically follow the evolution of the lowest neutral meson state as a function of MF strength. Calculating the color Coulomb energy $V_{Coul}$ we have observed the unbounded negative (at least in the limit of large $N_c$) contribution at large MF which makes the mass negative for $eB> eB^{QCD}_{crit}$. We display the $π^0$ and $ρ^0$ masses as functions of MF in comparison with recent lattice data.

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arXiv2012

Analysis of the QCD spectrum and chiral symmetry breaking with varying quark masses

The meson spectrum of QCD is studied in the framework of nonperturbative QCD as a function of varying quark masses $m_q$. It is shown, that the total spectrum consists of two branches: 1) the standard one, which may be called the flux-tube spectrum, depending approximately linearly on $m_q$ and 2) the chiral symmetry breaking (CSB) spectrum for pseudoscalar flavor nonsinglet (PS) mesons, with mass dependence $\sqrt{m_q}$. The formalism for PS mesons is derived from the QCD Lagrangian with $m_q$ corrections, and a unified form of the PS propagator was derived. It is shown, that the CSB branch of PS mesons joins to the flux-tube branch at around $m_q=200$ MeV. All these results are in close correspondence with recent numerical data on large lattices.

hep-ph↗
arXiv2012

The ratio of decay widths of X(3872) to $ ψ^{\prime}γ$ and $ J/ψγ$ as a test of the X(3872) dynamical structure

Radiative decays of X(3872) with $J^{PC}=1^{++}$ are studied in the coupled-channel approach, where the $c\bar c$ states are described by relativistic string Hamiltonian, while for the decay channels $DD^*$ a string breaking mechanism is used. Within this method a sharp peak and correct mass shift of the $2 {}^3P_1$ charmonium state just to the $D^0D^{*0}$ threshold was already obtained for a prescribed channel coupling to the $DD^*$ decay channels. For the same value of coupling the normalized wave function (w.f.) of X(3872) acquires admixture of the $1 {}^3P_1$ component with the w.f. fraction $c_1=0.153 (θ=8.8^\circ$), which increases the transition rate $Γ(X(3872)\rightarrow J/ψγ)$ up to 50-70 keV, making the ratio $R=\frac{\mathcal{B}(X(3872)\rightarrow ψ^{\prime}γ)}{\mathcal{B}(X(3872)\rightarrow J/ψγ)}=0.8\pm 0.20 (th)$ significantly smaller, as compared to $R\simeq 5$ for X(3872) as a purely $2 {}^3P_1$ state.

hep-ph↗
arXiv2012

Mass generation with adjoint fermions

The QCD-like gauge theory with adjoint fermions is considered in the field correlator formalism and the total spectrum of mesons and glueballs is obtained in agreement with available lattice data. A new state of a white fermion appears, as a bound state of the adjoint fermion and gluon with the mass close to that of glueball. It is shown, that the main features of spectra and thermodynamics of adjoint fermions can be explained by this new bound state.

hep-ph↗
arXiv2012

Theory of hadron decay into baryon-antibaryon final state

The nonperturbative mechanism of baryon-antibaryon production due to double quark pair $(q\bar q)$($q\bar q)$ generation inside a hadron is considered and the amplitude is calculated as matrix element of the vertex operator between initial and final hadron wave functions. The vertex operator is expressed solely in terms of first principle input: current quark masses, string tension $σ$ and $α_s$. In contrast to meson-meson production via single pair generation, in baryon case a new entity appears in the vertex: the vacuum correlation length $λ$, which was computed before through string tension $σ$. As an application electroproduction of $Λ_c \barΛ_c$ was calculated and an enhancement near 4.61 GeV was found in agreement with recent experimental data.

hep-ph↗
arXiv2011

Theory of time-like baryon form factors near thresholds

A new mechanism of baryon-antibaryon production via nonperturbative double pair creation in intermediate mesons is proposed and the theory contains no fitting parameters. It is shown, that near-threshold resonances are responsible for enhancements in electroproduction cross sections: $ψ(4S)$ for $Λ^+_c Λ^-_c, Υ(6S)$ for $Λ_b \bar Λ_b$. An admixture of intermediate $D$- wave resonances produces angular dependence in differential cross section and can explain unusual behavior of the ratio $G_E/G_M$ for the proton.

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