arXiv subjects

Yu. A. Simonov

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

At least 19 recordsLinked to original sources

arXiv2024

Colour-electric and colour-magnetic confinement

The basic properties of the confinement mechanism in QCD -- the temperature dependence of the spatial and temporal string tensions ($σ_s(T)$ and $σ_E(T)$) -- are studied in the framework of the Field Correlator Method (FCM). It is shown that both functions are connected respectively to the spatial and temporal parts of the vacuum gluon energy $ε_s$ and $ε_E$ which define their equal values at $T=0$. However at $T>0$ the spatial part is growing with $T$ while the temporal part is destroyed by the hadronic pressure at $T=T_c$ (the deconfinement). Both properties are derived within the same method and are in a good agreement with the corresponding lattice data.

hep-ph↗

arXiv2024

New ideas in nonperturbative QCD -- I

The recent development of the Field Correlator Method (FCM) is discussed, with applications to the most interesting areas of QCD physics obtained in the lattice data and experiment. These areas include: a) the connection of colorelectric confinement with the basic quark and gluon condensates; b) the explicit form of the colorelectric deconfinement at a growing temperature $T$; c) the theory of the colormagnetic confinement at all temperatures; d) the theory of strong decays, the theory of pdf and jets in the instantaneous formalism with confinement. We demonstrate that the FCM with instantaneous formalism and confinement (instead of the light cone formalism and pure perturbation theory) can provide the way to the theory of QCD, which helps to describe world data without phenomenological parameters.

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arXiv2023

The spatial string tension from the Field Correlator Method

The phenomenon of the almost linear growth of the square root of spatial string tension $\sqrt{σ_s(T)}= c_σ g^2 T$ was found both in lattice and in theory, based on the Field Correlator Method (FCM). In the latter the string tension (both spatial and colorelectric) is expressed as an integral of the two gluon Green's function calculated with the same string tension: $σ= \int G^{(2g)}_σ$. This relation allows to check the selfconsistency of the theory. However at nonzero temperature $T$ in the two-gluon Green's function in the space-like region appear terms which create in $σ_s$ quadratic in T behavior. We calculate below in the paper the $σ_s$ numerically in the whole temperature region $T_c< T < 5 T_c$ using the FCM method and compare the results with lattice data finding a good agreement. This justifies the use of the FCM in the space-like region and in high T thermodynamics without extra parameters.

hep-lat↗

arXiv2023

Theory of the deconfinement process in QCD

The phenomenon of the deconfinement -- the spectacular drop of the colorelectric string tension at the critical temperature $T_c$ -- is studied within the method of field correlators (FCM) taking into account directly the contribution of the gluon condensate into the hadronic free energy. Using the resulting expressions for the free energy as a sum of the gluon condensate (the vacuum energy) and the hadronic pressure one obtains the possibility to calculate the deconfinement temperature $T_c$ and the temperature behavior of the string tension $σ_E(T)$ and the gluonic condensate $G_2(T)$ below $T_c$. The connection between the string tension and the quark condensate found in the framework of FCM allows the predict also the latter as a function of $T$ . These results are compared to the known lattice data of $T_c$, $σ_E(T)$, $\langle \bar{q}q \rangle(T)$ for hadronic media with different $n_f$ and $m_q$ and in the external magnetic field $eB$. The good agreement of the results of this approach with lattice data is demonstrated.

hep-ph↗

arXiv2023

The scalar exotic resonances X(3915), X(3960), X(4140)

The scalar resonances $X(3915), X(3960), X(4140)$ are considered as exotic four-quark states: $cq\bar c \bar q, cs\bar c \bar s, cs\bar c\bar s$, while the $X(3863)$ is proved to be the $c\bar c, 2\,^3P_0$ state. The masses and the widths of these resonances are calculated in the framework of the Extended Recoupling Model, where a four-quark system is formed inside the bag and has relatively small size ($\la 1.0$~fm). Then the resonance $X(3915)$ appears due to the transitions: $J/ψω$ into $D^{*+}D^{*-}$ (or $D^{*0}\bar D^{*0})$ and back, while the $X(3960)$ is created due to the transitions $D_s^+D_s^-$ into $J/ψϕ$ and back, and the $X(4140)$ is formed in the transitions $J/ψϕ$ into $D_s^{*+}D_s^{*-}$ and back. The characteristic feature of the recoupling mechanism is that this type of resonances can be predominantly in the $S$-wave decay channels and has $J^P=0^+$. In two-channel case the resonance occurs to be just near the lower threshold, while due to coupling to third channel (like the $c\bar c$ channel) it is shifted up and lies by (20--30)~MeV above the lower threshold. The following masses and widths are calculated: $M(X(3915))=3920$~MeV, $Γ(X(3915))=20$~MeV; $M(X(3960))=3970$~MeV, $Γ(X(3960)=45(5)$~MeV, $M(X(4140))= 4120(20)$~MeV, $Γ(X(4140))=100$~MeV, which are in good agreement with experiment.

hep-ph↗

arXiv2022

The two-channel exotic charmonium-like resonances in the mass region $(3900-4700)$ MeV

The resonances, containing $c\bar c$ plus $s\bar s$ (or light $q\bar q$) quarks in the mass region $(3900-4700)$ MeV, are analyzed in the relativistic strong coupling theory, with and without channel coupling phenomena. The conventional charmonium spectrum is presented, being calculated with the relativistic string Hamiltonian, which does not contain fitting parameters, while for high excitations the universal flattened confining potential is used. It is shown that $X(4274),X(4500),X(4700)$ can be identified as $3\,^3P_1, 4\,^3P_0, 5\,^3P_0$ states. The exotic states are considered using the coupled-channel (recoupling) theory, when two mesons $m_1,m_2$ transfer into another two mesons $m_3, m_4$ and back (infinite number of times), creating the four-quark systems. The resonances $X(3875), X(3915), Z_{cs}(3985), X(4140)$ can be explained in this way as the exotic four-quark states in the $S$-wave decay channels.

hep-ph↗

arXiv2022

Analysis of the exotic resonances in the systems $QQ\bar q\bar q$ and $Qq\bar Q\bar q$ with the extended recoupling model

The phenomenon of a narrow peak X(3875), discovered recently by the LHCb in the $D^*D$ system, and the absence of resonances in the $D_sD_s$ and $D_s^*D_s^*$ systems is discussed within the new extended version of the Recoupling Model, where the resonance is the result of infinite recoupling transitions of confining strings between quarks and antiquarks. We show that existence of the resonance in the $D^*D$ and its absence in $D_sD_s$ and $D_s^*D_s^*$ systems are the natural results of the Recoupling Mechanism. The application of this mechanism to the $D\bar D^*$ system allows to obtain the resonance $Z_c(3900)$ with larger width in agreement with experimental data.

hep-ph↗

arXiv2022

The spatial string tension and the nonperturbative Debye mass from the Field Correlator Method

The phenomenon of the almost linear growth of the square root of spatial string tension $\sqrt{σ_s(T)}= c_σ g^2 T$ and of the Debye mass $m_D(T)$ was found both in lattice and in theory, based on the Field Correlator Method (FCM). In the latter the string tension (both spatial and colorelectric) is expressed as an integral of the two gluon Green's function calculated with the same string tension: $σ= \int G^{(2g)}_σ$. This relation allows to check the selfconsistency of the theory and at high T it allows also to calculate $c_σ$ and hence $σ_s$. We calculate below in the paper the corresponding coefficients $c_σ$ and $c_D$ numerically in the FCM method and compare the results with lattice data finding a good agreement. This justifies the use of the FCM in the space-like region and in high T thermodynamics without extra parameters.

hep-ph↗

arXiv2022

The colormagnetic confinement in QCD

Colormagnetic confinement as a natural component of the QCD confinement is explained and treated in the framework of the Field Correlator Method. For quarks and gluons in hadrons the effects of the colormagnetic confinement are discussed at zero temperature, where it contributes to the spectrum properties and can create its own bound states, while at nonzero temperature in the EoS of the quark gluon plasma the colormagnetic confinement plays a dominating role. Its properties in the QCD thermodynamics are discussed in detail.

hep-ph↗

arXiv2022

Quark condensate in QCD at nonzero magnetic field and temperature

The basic form of the quark condensate for arbitrary values of external magnetic field and temperature, is derived using the field equations with account of confinement. The resulting expression of the chiral condensate is shown to be proportional to square of the singlet $q\bar q$ ground state wave function at origin, $|ϕ_0(0)|^2$. For light quarks without magnetic field the condensates are proportional to $σ^{3/2}$ ($σ$ is the string tension). Numerical results are presented in 5 Tables and shown to be in good agreement with the lattice data, both for nonzero magnetic field $eB$ and temperature $T$ in the range $0 <T < 120$~MeV,~ $0 <eB <4$~GeV$^2$.

hep-ph↗

arXiv2021

Chiral dynamics with confinement versus the standard chiral theory

Chiral dynamics is investigated using the chiral confining Lagrangian (CCL), previously derived from QCD with confinement interaction. Based on the calculations of the quark condensate, which is defined entirely by confinement in the zero quark mass limit, one can assert that chiral symmetry breaking occurs not spontaneously but is predetermined by confinement. The expansion of the CCL provides the GMOR relations and the effective chiral Lagrangian, which is used to provide the masses and decay constants of all chiral mesons, including $η,η'$. For the latter one needs to define a non-chiral component due to confinement, while the orthogonality condition defines the wave functions and the eigenvalues. The resulting masses and decay constants of all chiral mesons are obtained in good agreement with experimental and lattice data.

hep-ph↗

arXiv2021

Hadron wave functions in high-energy scattering, form factors and strong decays: the effects of the Lorentz contracted form

We study the class of processes where the dynamics depends essentially on the properties of the hadron wave functions involved in the reactions. In this case the momentum dependence of the form of wave functions imposed by Lorentz invariance and in particular by the Lorentz contraction can be tested in the experiment and may strongly influence the resulting cross sections. One example of such observables is given by the hadron form factors, where it was shown that the large Q behavior is mostly frozen, when the Lorentz contraction of the hadron wave functions is taken into account. Another example considered previously is the strong hadron decay with high energy emission. In this paper we study the role of the Lorentz contraction in the high-energy hadron-hadron scattering process at large momentum transfer. For the $pp$ and $p\bar p$ scattering at large $s$ it is shown that at small $-t << s$ the picture of two exponential slopes in the differential cross section explained previously by the author is stable while the backward scattering cross section is strongly increased by the Lorentz contraction.

hep-ph↗

arXiv2021

Quark condensate from confinement in QCD

The scalar confinement in QCD is shown to produce the nonzero quark condensate for any current quark mass. Mechanisms for the Chiral Symmetry breaking and for the nonzero quark condensates are revealed. For the light and strange flavors the condensates are essentially chiral (proportional to (string tension)$^{3/2}$). The expressions for the quark condensates are obtained as a sum over non-chiral meson states, and, using the operator product expansion, as an explicit expression that involves the confining string tension and the current quark mass. The numerical results are fairly close to the lattice data.

hep-ph↗

arXiv2021

Proton and neutron form factors with quark orbital excitations

Nucleon form factors play an especially important role in studying the dynamics of nucleons and explicit structure of the wave functions at arbitrary nucleon velocity. The purpose of the paper is to explain theoretically all four nucleon form factors measured experimentally in the cross section measurements (by the Rosenbluth method), yielding almost equal normalized form factors $G^p_E,G^p_M,G^n_M$, as well as in the polarization transfer experiments, where a strongly decreasing proton electric form factor has been discovered. It is shown, using relativistic hyperspherical formalism, that the nucleon wave functions in the lowest approximation provide almost equal normalized form factors as seen in the Rosenbluth cross sections, but in the higher components they contain a large admixture of the quark orbital momenta, which strongly decreases $G^p_E$ and this effect is possibly detected in the polarization transfer method (not seen in the classical cross section experiments). Moreover, the same admixture of the higher components explains the small positive form factor $G^n_E$. The resulting form factors, $G^p_M(Q),G^p_E(Q),G^n_M(Q)$ are calculated up to $Q^2\approx 10$ GeV$^2$, using the standard and the Lorentz contracted wave functions and shown to be in reasonable agreement with experimental data.

hep-ph↗

arXiv2021

The fundamental scale of QCD

There are several scales in the QCD as the theory of strong interaction: the vacuum gluonic condensate (as the divergence of the dilatation current), the nucleon mass as the basic mass scale in our universe, which is connected to the string tension $σ$, and the perturbative QCD scale $Λ_{\rm QCD}$, which defines the scale of the renormalized perturbative expansions. In this paper we connect all these scales to the vacuum condensate, using the field correlator method, where the string tension is expressed in terms of nonlocal field correlators, which are connected to the local condensates, while the perturbative $Λ_V$ is connected to $σ$ in the framework of the Background Perturbation Theory (BPT). We also demonstrate how the IR singularities and IR renormalons disappear in BPT making the resulting theory internally consistent.

hep-ph↗

arXiv2021

Strong decays with the boost-corrected wave functions

Strong decay probabilities are calculated using the Lorentz contracted wave functions of decay products, determined in the arbitrary dynamical scheme with the instantaneous interaction. It is shown that the decay width obtains an additional factor defined by the contraction coefficient $C_m(s)$, which for two-body equal mass decays is $C^2_m(s)= 4m^2/s$ , $s= E^2$. The resulting decay widths are compared to the experimental data, where in particular the $ρ(770),ρ(1450) $ decay data require an additional $1/s$ dependence of the width to fit the data. Important consequences for the dynamics of hadron decays and scattering are shortly discussed.

hep-ph↗

arXiv2021

Recoupling Mechanism for exotic mesons and baryons

The infinite chain of transitions of one pair of mesons (channel I) into another pair of mesons (channel II) can produce bound states and resonances in both channels even if no interactions inside channels exist. These resonances which can occur also in meson-baryon channels are called channel-coupling (CC) resonances. A new mechanism of CC resonances is proposed where transitions occur due to a rearrangement of confining strings inside each channel -- the recoupling mechanism. The amplitude of this recoupling mechanism is expressed via overlap integrals of the wave functions of participating mesons (baryons). The explicit calculation with the known wave functions yields the peak at $E= 4.12$ GeV for the transitions $J/ψ+ ϕ\leftrightarrow D^*_s + \bar D^*_s $, which can be associated with $χ_{c1}(4140)$, and a narrow peak at $3.98$ GeV with the width $10$ MeV for the transitions $D^{-}_s + D^*_0 \leftrightarrow J/ψ+ K^{*-},$ which can be associated with the recently discovered $Z_{cs}(3985)$.

hep-ph↗

arXiv2020

Understanding two slopes in the pp (p\bar p) differential cross sections

Recent experiments have discovered two exponents in the $pp$ elastic differential cross sections with two different slope parameters, of the order $(16-20)$~GeV$^{-2}$ and $(4-4.8)$~GeV$^{-2}$ in the regions $ -t \la 0.5 $~GeV$^2$ and $ -t \ga 1$~GeV$^2$, respectively. We suggest a simple model of the $pp$ elastic scattering with two types of particle exchanges: 1) when the exchanged particle transfers the momentum $\veQ$ from a quark of the proton $p_1$ to one quark in another proton $p_2$, producing the slope $B_1$; 2) when the transfer occurs from two quarks in the $p_1$ to two quarks in the $p_2$, giving the exponent with the slope $B_2$. The resulting amplitude is proportional to the product of the form factors of two protons, depending on $\veQ$, but with different coefficients in the cases 1) and 2). Using the only parameter - the proton charge radius $r^2_{ch}= 0.93$~fm$^2$, one obtains $B_1 = 16$~GeV$^{-2}$,~$ B_2 = 4$~GeV$^{-2}$ with the strict value of the ratio, $\frac{B_1}{B_2} = 4.0$, independent of $r_{ch}$. These predictions are surprisingly close to the data both in the $pp$ and in the $\bar p p$ differential cross sections. Comparison to experimental data and theoretical approaches is discussed, together with possible implications for the future development of the theory.

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