New parameterization of the resonant production amplitudes near an inelastic threshold

New formulae for the resonant scattering and the production amplitudes near an inelastic threshold are derived. It is shown that the Flatte formula, frequently used in experimental analyses, is not sufficiently accurate. Its application to data analysis can lead to a substantial distortion of the effective mass spectra and of the resonance pole positions. A unitary parameterization, satisfying a generalized Watson theorem for the production amplitudes, is proposed. It can be easily applied to study production processes, multichannel meson-meson interactions and the resonance properties, including among others the scalar resonances a0(980) and f_0(980).Comment: 4 pages, 1 figure, contribution to MESON 2008, Tenth International Workshop on Meson Production, Properties and Interaction, 6-10 June, Krakow, Poland, to be published in International Journal of Modern Physics

Coupled channel study of a0 resonances

The coupled channel model of the a0(980) and a0(1450) resonances has been constructed using the separable pion-eta and K-anti K interactions. We have shown that two S-matrix poles corresponding to the a0(980) meson have significantly different widths in the complex energy plane. The K-anti K to pion-eta branching ratio, predicted in our model near the a0(1450) mass, is in agreement with the result of the Crystal Barrel Collaboration. The K-anti K interaction in the S-wave isovector state is not sufficiently attractive to create a bound a0(980) meson.Comment: 15 pages, latex, 4 eps figures, 2 tables, minor corrections, version to appear in Phys. Lett.

Extracting the

We present a phenomenological analysis of the π+π- photoproduction data obtained by the CLAS collaboration at the Thomas Jefferson Laboratory. A special emphasis is put on the interference pattern observed in the moments of angular distribution for the π+π- efective masses around 1 GeV. This pattern is attributed to the photoproduction of the scalar-isoscalar resonance f0(980). By fitting the model parameters to the data we obtain the strengths of the resonant and nonresonant parts of the S-wave photoproduction amplitude. We calculate the f0(980) photoproduction cross section which is smaller than previous estimations by a factor of about 5. A new estimation of the product of the σ meson couplings to nucleon and to the γρ system |gNNσgγρσ| is given

Latest studies on the reaction e+e−→K+K−γe^{+}e^{-}\rightarrow K^{+}K^{-}\gamma

Recent theoretical studies of the e+e- → K+K-γ process are described. Three main reaction mechanisms are considered: the initial state radiation, the final state radiation and the strong interaction between the outgoing K+K- mesons. The K+K- effective mass distributions are derived for three different models which in past have been used for a description of the e+e- → π+π-η data. Also the numerical results for the angular photon and kaon distributions are presented. A new model of the e+e- → M1M2γ reactions is outlined which can serve for multichannel analyses of the radiative processes with a production of two pseudoscalar mesons M1 and M2

Theoretical studies of the reaction e+e−→K+K−γe^{+}e^{-}\rightarrow K^{+}K^{-}\gamma

We present studies of the e+e− → K+K−γ reaction for the e+e− center-of-mass energies close to the ϕ(1020) meson mass. Different mechanisms leading to the final state are considered. The strong interaction amplitudes of the K+K− pairs in the S - wave are taken into account. In addition, the photon emission in the initial state, the final state radiation effects and all the possible interference terms are included in the transition matrix elements. The K+K− effective mass distributions and the angular dependence of the reaction cross-section are calculated

Dalitz plot studies of D0 → KS0π+π− decays in a factorization approach

A quasi two-body QCD factorization is used to study the D0 → KS0π+π− decays. The presently available high-statistics Dalitz plot data of this process measured by the Belle and BABAR Collaborations are analyzed together with the τ− → KS0π−ντ decay data. The total experimental branching fraction is also included in the fits which show a very good overall agreement with the experimental Dalitz plot density distributions. The branching fractions of the dominant channels compare well with those of the isobar Belle or BABAR models. We show that the branching fractions corresponding to the annihilation amplitudes are significant