14904389
Model independent approach as a tool of studying chiral symmetry
A simultaneous analysis (in the model-independent approach) of the $\pi\pi$ scattering (from the threshold to 1.9 GeV) and of the $\pi\pi\to K\overline{K}$ process (from the threshold to $\sim$ 1.46 GeV) is carried out in channel with $I^GJ^{PC}=0^+0^{++}$. The existence of the $f_0(665)$ state with properies of the $\sigma$-meson is proved. An indication for the glueball nature of the $f_0(1500)$ is obtained. A minimum scenario of the simultaneous description of the processes $\pi\pi\to\pi\pi,K\overline{K}$ does without the ${f_0}(1370)$ resonance. A version including this state is also considered. In this case the ${f_0}(1370)$ resonance has the dominant $s{\bar s}$ component (the ratio of its coupling constant with the $\pi\pi$ channel to the one with the $K\overline{K}$ channel is 0.12). The coupling constants of the observed states with the $\pi\pi$ and $K\overline{K}$ systems and the $\pi\pi$ and $K\overline{K}$ scattering lengths are obtained. A parameterless description of the $\pi\pi$ background is given by allowance for the left-hand branch-point in the uniformizing variable. On the basis of this and of the fact that all the adjusted parameters for the $\pi\pi$ scattering are only the positions of poles describing resonances, it is concluded that our model-independent approach is a valuable tool for studying the realization schemes of chiral symmetry. The existence of the $f_0(665)$ state and the obtained $\pi\pi$-scattering length ($a_0^0\approx 0.27 m_{\pi^+}^{-1}$) seem to suggest the linear realization of chiral symmetry.
15150236
Effective quark model with chiral U(3) x U(3) symmetry for baryon octet and decuplet
We suggest an effective quark model for low-lying baryon octet and decuplet motivated by QCD with a linearly rising confinement potential incorporating the extended Nambu--Jona-Lasinio (ENJL) model with linear realization of chiral $U(3)\ifmmode\times\else\texttimes\fi{}U(3)$ symmetry. Baryons are considered as external heavy states coupled to local three-quark currents with fixed spinorial structure and to low-lying mesons through quark-meson interactions defined in the ENJL model. In the constituent quark loop representation we have calculated the coupling constants of the $\ensuremath{\pi}NN, \ensuremath{\pi}N\ensuremath{\Delta},$ and $\ensuremath{\gamma}N\ensuremath{\Delta}$ interactions and the ${\ensuremath{\sigma}}_{\ensuremath{\pi}N}$ term. The obtained results are in reasonable agreement with experimental data and other effective field theory approaches.
121038747
EFFECTIVE CHIRAL LAGRANGIANS, THE QUARK MODEL OF SUPERCONDUCTIVITY TYPE AND THE PROBLEM OF P-A DIAGONALIZATION
The vertices appearing after the inclusion of P-A transitions and a subsequent diagonalization of the chiral Lagrangian are analyzed in the quark model of superconductivity type. These vertices can conditionally be divided into physical and nonphysical ones. It is shown that if the Pauli-Villars regularization is used, the contribution of the latter can be eliminated from the description of the physical processes. This is in full agreement with the experimental data.
122493642
On the problem of D-meson leptonic and semileptonic decays
Abstract The infinite mass effective theory, when a heavy quark mass goes to infinity, and chiral perturbation theory at the quark level, based on the extended Nambu-Jona-Lasinio model, are applied for the description of form factors of semileptonic decay D→ K e + ν e and leptonic constant FD of D-mesons. The relation is derived connecting the form factor f+(0) with the ratio F D F π , which gives the estimate F D F π =1.21±0.17 . The slope parameter of the f+ form factor is calculated in agreement with experimental data.
120703177
IS THE CRONIN’S REPRESENTATION CORRECT FOR THE PENGUIN OPERATOR?
It is shown that the Cronin’s operator, being used for a phenomenological description of non-loptonic K-meson decays within the effective chiral Lagrangian approach with non-linear realization of chiral SU(3)×SU(3) symmetry (so-called, chiral perturbation theory at the hadronic level), cannot be applied to the determination of the Penguin-operator (O5-operator) at the hadronic level. The affirmation is based on the proof of the violation of the low-energy theorem $\lim _{P + \to 0} \left\langle {\pi ^ + \left( {p_ + } \right)\pi ^ - \left( {p_ - } \right)\left| {O_5 } \right|K^0 \left( p \right)} \right\rangle = \frac{i}{{F_\pi }}\left\langle {\pi ^0 \left( p \right)\left| {O_5 } \right|K^0 \left( p \right)} \right\rangle $ which is valid within the framework of the Cronin’s representation. The violation of this low-energy theorem is obtained at the quark level and connected with the account of the low-energy interactions of pions caused by the overlap of wave functions of pions in the |π+π−> state in the...
14072015
Scalar Mesons and Glueballs in a Chiral U(3)xU(3) Quark Model with 't Hooft Interaction
In a U(3)x U(3) quark chiral model of the Nambu-Jona-Lasinio type with the 't Hooft interaction, the ground scalar isoscalar mesons and a scalar glueball are described. The glueball (dilaton) is introduced into the effective meson Lagrangian written in a chirally symmetric form on the base of scale invariance. The singlet-octet mixing of scalar isoscalar mesons and their mixing with the glueball are taken into account. Mass spectra of the scalar mesons and glueball and their strong decays are described.
118401873
New simple explicit solutions of perfect-fluid hydrodynamics and phase-space evolution
New exact solutions of relativistic perfect-fluid hydrodynamics are presented, including the first family of exact rotating solutions. The method used to search for them is a simultaneous investigation of the relativistic hydrodynamical equations and the collisionless Boltzmann equation. Possible connections to the evolution of hot and dense partonic matter in heavy-ion collisions is discussed.
119143405
Detailed description of accelerating, simple solutions of relativistic perfect fluid hydrodynamics
In this paper we describe in full details a new family of recently found exact solutions of relativistic, perfect fluid dynamics. With an ansatz that generalizes the well-known Hwa-Bjorken solution we obtain a wide class of new exact, explicit, and simple solutions, which have a remarkable advantage as compared to presently known exact and explicit solutions: they do not lack acceleration. They can be utilized for the description of the evolution of the matter created in high energy heavy ion collisions. Because these solutions are accelerating, they provide a more realistic picture than the well-known Hwa-Bjorken solution, and give more insight into the dynamics of the matter. We exploit this by giving an advanced simple estimation of the initial energy density of the produced matter in high energy collisions, which takes acceleration effects, i.e., the work done by the pressure, and the modified change of the volume elements, into account. We also give an advanced estimation of the life-time of the reaction. Our new solutions can also be used to test numerical hydrodynamical codes reliably. In the end, we also give an exact, 1+1 dimensional, relativistic hydrodynamical solution, where the initial pressure and velocity profile is arbitrary, and we showmore » that this general solution is stable for perturbations.« less