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N. N. Achasov

Publications and source records attributed to N. N. Achasov.

At least 109 records · Page 6Linked to original sources
arXiv2001

Effective Lagrangians Induced by the Anomalous Wess-Zumino Action and $I^G(J^{PC})=1^-(1^{-+})$ Exotic States

A simple dynamical model for the exotic waves with $I^G(J^{PC})=1^-(1^{-+})$ in the reactions $ρπ\toρπ$, $ρπ\toηπ$, $ρπ\toη'π$, $ ρπ\to(K^*\bar K+\bar K^*K)$, and in the related ones, is constructed beyond the scope of the quark-gluon approach. The model satisfies unitarity and analyticity and uses as a "priming" the anomalous non-diagonal $VPPP$ interaction which couples together the four channels $ρπ$, $ηπ$, $ η'π$, and $K^*\bar K+\bar K^*K$. The possibility of the resonance-like behavior of the $I^G(J^{PC})=1^-(1^{-+})$ amplitudes belonging to the $\{10\}- \{\bar{10}\}$ and $\{8\}$ representations of SU(3) as well as their mixing is demonstrated explicitly in the 1.3--1.6 GeV mass range which, according to the current experiments, is really rich in exotics.

hep-ph↗
arXiv2001

Analysis of nature of phi -> gamma pi0 eta and phi -> gamma pi0 pi0 decays

We study interference patterns in the phi -> gamma a0 + pi0 rho -> gamma pi eta and phi -> gamma f0 + pi0 rho -> gamma pi0 pi0 reactions. Taking into account the interference, we fit the experimental data and show that the background reaction does not distort the pi0eta spectrum in the decay phi -> gamma pi eta everywhere over the energy region and does not distort the pi0 pi0 spectrum in the decay phi -> gamma pi0 pi0 when the invariant mass m_{pi0 pi0} > 670 MeV. We discuss the details of the scalar meson production in the radiative decays and note that there are conclusive arguments in favor of the one-loop mechanism phi -> K+K- -> gamma a0 (or gamma f0). We discuss also distinctions between the four-quark, molecular, and two-quark models and argue that the establishment of the scalar meson production mechanism in the phi radiative decays gives new strong evidence in favor of the four-quark nature of the scalar a0(980) and f0(980) mesons.

hep-ph↗
arXiv2001

Mechanisms of the $f_0(980)$ production in the reaction $π^-p\toπ^0 π^0n$

The model of the pure one-pion exchange mechanism, which gives a good description of the GAMS results on the alteration of the $S$-wave $π^0π^0$ mass spectrum in the $f_0(980)$ region in the reaction $π^-p\toπ^0π^0n$ with increasing $-t$, is compared with the recent detailed data on the $m$ and $t$ distributions of the $π^-p\toπ^0π^0n$ events obtained by the BNL-E852 Collaboration. It is shown that the predictions of this model are not confirmed by the BNL data. Therefore the observed phenomenon should be explained by the different exchange mechanism. It is most likely to be the $a_1$ exchange mechanism.

hep-ph↗
arXiv2001

Analysis of the nature of the $ϕ\toγπη$ and $ϕ\toγπ^0π^0$ decays

We study interference patterns in the $ϕ\to(γa_0+π^0ρ)\toγπη$ and $ϕ\to(γf_0+π^0ρ)\toγπ^0π^0$ reactions. Taking into account the interference, we fit the experimental data and show that the background reaction does not distort the $π^0η$ spectrum in the decay $ϕ\toγπη$ everywhere over the energy region and does not distort the $π^0π^0$ spectrum in the decay $ϕ\toγπ^0π^0$ in the wide region of the $π^0π^0$ system invariant mass, $m_{ππ}>670$ MeV, or when the photon energy is less than 300 MeV. We discuss the details of the scalar meson production in the radiative decays and note that there are reasonable arguments in favor of the one-loop mechanism $ϕ\to K^+K^-\toγa_0$ and $ϕ\to K^+K^-\toγf_0$. We discuss also distinctions between the four-quark, molecular, and two-quark models and argue that the Novosibirsk data give evidence in favor of the four-quark nature of the scalar $a_0(980)$ and $f_0(980)$ mesons.

hep-ph↗
arXiv2001

Measuring the finite width and unitarity corrections to the phi-omega mixing amplitude

It is shown that the phase of phi-omega interference in the reaction e^+e^- -->pi^+ pi^- pi^0 at energies close to the phi(1020) peak can be calculated in a way that is practically independent of the model of phi-omega mixing. The magnitude of the presently measured interference phase, still of poor accuracy, is in agreement with the predictions based on extending the omega(782) resonance tail from the peak position to the phi mass upon assuming the omega -->rho pi -->3pi model. The calculated omega width at the phi mass is about 200 MeV.

hep-ph↗
arXiv2001

Effective Lagrangian induced by the anomalous Wess-Zumino action and the exotic resonance state with $I^G(J^{PC})=1^-(1^{-+})$ in the $ρπ$, $ηπ$, $η'π$, and $K^*\bar K+\bar K^*K$ channels

A simple model for the exotic waves with $I^G(J^{PC})=1^-(1^{-+})$ in the reactions $VP\to VP$, $VP\to PP$, and $PP\to PP$ is constructed beyond the scope of the quark-gluon approach. The model satisfies unitarity and analyticity and uses as a "priming" the "anomalous" nondiagonal $VPPP$ interaction which couples together the four channels $ρπ$, $ηπ$, $η'π$, and $K^*\bar K+\bar K^*K$. The possibility of the resonancelike behavior of the $I^G(J^{PC})=1^-(1^{-+})$ amplitudes belonging to the $\{10\}- \{\bar{10}\}$ and $\{8\}$ representations of SU(3) as well as their mixing is demonstrated explicitly in the $1.3-1.6$ GeV mass range which, according to the current experimental evidence, is really rich in exotics.

hep-ph↗
arXiv2000

Many pion decays of rho(770) and omega(782) mesons in chiral theory

The decays rho(770) to 4 pi and omega(782) to 5pi are considered in detail in the approach based on the Weinberg Lagrangian obtained upon the nonlinear realization of chiral symmetry, added with the term induced by the anomalous Lagrangian of Wess and Zumino. The partial widths and excitation curves of the decays rho^0 to 2 pi^+ 2 pi^-, pi^+ pi^- 2 pi^0, rho^{+-} to 2 pi^{+-} pi^{-+} pi^0, rho^(+-} to pi^(+-} 3 pi^0 are evaluated for e^+e^- annihilation, photoproduction and tau lepton decays. The results of calculations are compared with the recent CMD-2 data on the decay rho^0 to 2 pi^+ 2 pi^- observed in e^+e^- annihilation. The omega to 5 pi decay widths and excitation curves in e^+e^- annihilation are obtained. The angular distributions for various combinations of the final pions in the decays rho to 4 pi and omega to 5 pi are written. The perspectives of the experimental study of the above decays in e^+e^- annihilation, tau lepton decays and photoproduction are discussed.

hep-ph↗
arXiv2000

On the masses, branching ratios, and full widths of heavy rho', rho'' and omega', omega'' resonances

Based on the previous and recent fits of multiple data on the reactions of e^+e^- annihilation, tau lepton decay, and the reaction K^-p -> pi^+pi^- Lambda, the magnitude of the branching ratios and total widths of the isovector rho', rho'', and the isoscalar omega', omega'' resonances are calculated. Some topics on the spectroscopy of the rho(1450) and omega(1420) states are discussed.

hep-ph↗
arXiv2000

The decay omega(782) -> 5 pi in chiral theory

The arguments are put forward that the many pion decays omega ->2 pi^+ 2 pi^- pi^0 and pi^+ pi^- 3 pi^0 provide an ideal test site for testing the predictions of chiral models of the vector meson decays into many pions. Using the approach based on the Weinberg Lagrangian or, in a new language, the Lagrangian of hidden local symmetry added with the term induced by the anomalous Lagrangian of Wess and Zumino, the partial widths of these decays are evaluated, and their excitation curves in e^+e^- annihilation are obtained. The discussed are the perspectives of the experimental study of the decays omega -> 5 pi in e^+e^- annihilation and photoproduction.

hep-ph↗
arXiv1999

Chiral dynamics of many pion systems: the rho to 4 pi and omega to 5 pi decays

Based on the Weinberg lagrangian or, in a new language, the lagrangian of hidden local symmetry added with the term induced by the anomalous lagrangian of Wess and Zumino, the dynamics of the decays rho to 4 pi and omega to 5 pi is considered. The excitation curves of rho resonance in its decay to 4 pi are obtained for the first time. The comparison with recent CMD-2 data is given. The partial widths of the decays omega to 2 pi^+ 2 pi^- pi^0 and omega to pi^+ pi^-3 pi^0 which can be measured on colliders with luminosity 10^{33}{cm }^{-2}{s}^{-1} are evaluated for the first time.

hep-ph↗
arXiv1999

Chiral dynamics of many-pion systems

Based on the Weinberg lagrangian or, in a new language, the lagrangian of hidden local symmetry added with the term induced by the anomalous lagrangian of Wess and Zumino, the dynamics of the decays rho to 4 pi and omega to 5 pi is considered. The excitation curves of rho resonance in its decay to 4 pi are obtained for the first time. The comparison with recent CMD-2 data is given. The partial widths of the decays omega to 2 pi^+ 2 pi^- pi^0 and omega to pi^+ pi^- 3 pi^0 which can be measured on colliders with luminosity 10^{33}{cm }^{-2}{s}^{-1} are evaluated for the first time.

hep-ph↗
arXiv1999

On nature of scalar a_0(980) and f_0(980)-mesons

It is presented a critical consideration of all unusual properties of the scalar a_0(980) and f_0(980)-mesons in the four-quark, two-quark and molecular models. The arguments are adduced that the four-quark model is more preferable. It is discussed the complex of experiments that could finally resolve this issue.

hep-ph↗
arXiv1999

Exotic $ρ^\pmρ^0$ state photoproduction

It is shown that the list of unusual mesons planned for a careful study in photoproduction can be extended by the exotic states $X^\pm(1600)$ with $I^G(J ^{PC})=2^+(2^{++})$ which should be looked for in the $ρ^\pmρ^0$ decay channels in the reactions $γN\toρ^\pmρ^0N$ and $γN\toρ^\pm ρ^0Δ$. The full classification of the $ρ^\pmρ^0$ states by their quantum numbers is presented. A simple model for the spin structure of the $ γp\to f_2(1270)p$, $γp\to a^0_2(1320)p$, and $γN\to X^\pm (N, Δ)$ reaction amplitudes is formulated and the tentative estimates of the corresponding cross sections at the incident photon energy $E_γ\approx 6$ GeV are obtained: $σ(γp\to f_2(1270)p)\approx0.12$ $μ$b, $ σ(γp\to a^0_2(1320)p)\approx0.25$ $μ$b, $σ(γN\to X^\pm N\toρ^\pmρ^0N)\approx0.018$ $μ$b, and $σ(γp\to X^-Δ^{++ }\toρ^-ρ^0Δ^{++})\approx0.031$ $μ$b. The problem of the $X^\pm$ signal extraction from the natural background due to the other $π^\pmπ^0 π^+π^-$ production channels is discussed. In particular the estimates are presented for the $γp\to h_1(1170)π^+n$, $γp\toρ'^{+}n\to π^+π^0π^+π^-n$, and $γp\toωρ^0p$ reaction cross sections. Our main conclusion is that the search for the exotic $X^\pm(2^+(2^{++}))$ states is quite feasible at JEFLAB facility. The expected yield of the $γN\to X^\pm N\toρ^\pmρ^0N$ events in a 30-day run at the 100% detection efficiency approximates $2.8\times10^6$ events.

hep-ph↗