Search for the scalar a_0 and f_0 mesons in the \phi radiative decays

The potentialities of the production of the $a_0$ and $f_0$ mesons in the $\phi$ radiative decays are considered based on a new two-channel analysis of the $\pi\pi$ scattering in a energy region near 1 GeV. We predict $BR(\phi\to\gamma f_0(980))\sim10^{-5}-10^{-4}$ that is a great value for the decay forbidden by the Okubo-Zweig-Iizuka rule. We discuss the four-quark, $K\bar K$-molecule and two-quark scenarios for the $a_0$ and $f_0$ mesons. It is presented arguments that the $e^+e^-$-colliders and especially the $\phi$ factories give the possibility to choose a single one out of them.Comment: Talk given at HADRON-9

Entangled plasmon generation in nonlinear spaser system under action of external magnetic field

The present paper theoretically investigates features of quantum dynamics for localized plasmons in three-particle or four-particle spaser systems consisting of metal nanoparticles and semiconductor quantum dots. In the framework of the mean field approximation, the conditions for the observation of stable stationary regimes for single-particle plasmons in spaser systems are revealed, and realization of these regimes is discussed. The strong dipole-dipole interaction between adjacent nanoparticles for the four-particle spaser system is investigated. We show that this interaction can lead to the decreasing of the autocorrelation function values for plasmons. The generation of entangled plasmons in a three-particle spaser system with nonlinear plasmon-exciton interaction is predicted. For the first time the use of an external magnetic field is proposed for control of the cross-correlation between plasmons in the three-particle spaser system.Comment: 16 pages, 10 figure

Analysis of preliminary data on e+e−→ϕ→γf0(980)→γπ0π0e^+e^-\to\phi\to\gamma f_0(980)\to\gamma\pi^0\pi^0 reaction

We perform the analysis of the preliminary data on $e^+e^-\to\phi\to\gamma f_0(980)\to\gamma\pi^0\pi^0$ reaction simultaneously with the data on $\pi\pi$ scattering and reactions $J/\psi\to\phi\pi^+\pi^-$ and $K^-p\to\pi^+\pi^-(\Lambda,\Sigma)$. It is found that the $f_0(980)$ meson mass $m_{f_0}=950$ MeV and $B(\phi\to\gamma f_0\to\gamma\pi^0\pi^0)\simeq1\cdot10^{-4}$.Comment: 8 pages, revtex, 3 ps files of figures, minor change

Anomalous microwave conductivity coherence peak in c-axis MgB2 thin film

The temperature dependence of the real part of the microwave complex conductivity at 17.9 GHz obtained from surface impedance measurements of two c-axis oriented MgB2 thin films reveals a pronounced maximum at a temperature around 0.6 times the critical temperature. Calculations in the frame of a two-band model based on Bardeen-Cooper-Schrieffer (BCS) theory suggest that this maximum corresponds to an anomalous coherence peak resembling the two-gap nature of MgB2. Our model assumes there is no interband impurity scattering and a weak interband pairing interaction, as suggested by bandstructure calculations. In addition, the observation of a coherence peak indicates that the pi-band is in the dirty limit and dominates the total conductivity of our filmsComment: 10 pages, 4 figures, to be published in Phys. Rev. Let

Final-state interaction phase difference in J/ψ→ρηJ/\psi\to\rho\eta and ωη\omega\eta decays

It is shown that the study of the $\omega-\rho^0$ interference pattern in the $J/\psi\to (\rho^0+\omega)\eta\to\pi^+\pi^-\eta$ decay provides the evidence for the large (nearly $90^\circ$) relative phase between the one-photon and the three-gluon decay amplitudes.Comment: 5 pages, revtex, \tightenlines, a version published in Phys. Rev. D 61, 117504 (2000

Production of scalar KKˉK\bar K molecules in ϕ\phi radiative decays

The potentialities of the production of the scalar $K\bar K$ molecules in the $\phi$ radiative decays are considered beyond the narrow resonance width approximation. It is shown that $BR(\phi\rightarrow\gamma f_0(a_0)\rightarrow\gamma\pi\pi(\pi\eta))\approx (1\div 2)\times 10^{-5}\ ,\BR(\phi\rightarrow\gamma (f_0+a_0)\rightarrow\gamma K^+K^-)\alt 10^{-6}$and$BR(\phi\rightarrow\gamma (f_0+a_0) \to \gamma K^0\bar K^0)\alt 10^{-8}$. The mass spectra in the$\pi\pi\ ,\ \pi\eta\ ,\ K^+K^-\ ,\ K^0\bar K^0$channels are calculated. The imaginary part of the amplitude$\phi\rightarrow\gamma f_0(a_0)$is calculated analytically. It is obtained the phase of the scalar resonance production amplitude that causes the interference patterns in the reaction$e^+e^-\rightarrow\gamma \pi^+\pi^-$in the$\phi$ meson mass region.Comment: 19 pages, revtex, 4 eps files of figure