Results 1 - 10 of 6487
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[en] A parametrization is proposed for the line shapes of near-threshold resonances, which is based on the model of coupled channels and can include an arbitrary number of elastic and inelastic channels and bare poles. The proposed parametrization satisfies the requirements imposed by unitarity and analyticity, and is convenient for the data analysis embracing all available experimental information. The model parameters are physically meaningful, and their values can be found using different theoretical schemes.
[en] An article by Levin and Li does not distinguish the fulfillment of boundary conditions the convergent expansion of expressions that satisfy the boundary conditions, therefore their criticism of the article about truncated CCA is misleading. (orig./HSI)
[en] Using an interaction extracted from the local hidden gauge Lagrangians and the coupled channels ρN (s-wave), πN (d-wave), πΔ (s-wave) and πΔ (d-wave), we look in the region of √s = 1400 ‒ 1850 MeV and we find two resonances dynamically generated which are naturally associated to the N*(1520)(3/2-) and N*(1700)(3/2-). The N*(1700)(3/2-) appears neatly as a pole in the complex plane. The free parameters of the theory are chosen to fit the πN (d-wave) data. The unitary coupled channel approach followed here, in connection with the experimental data, leads automatically to a pole in the 1700 MeV region and makes this second 3/2- resonance unavoidable. (author)
[en] We discuss on very general grounds possible lineshapes of composite particles with one unstable constituent. Expressions are derived in a coupled-channel formalism for constituents interacting in an S-wave with no assumption made on the width of one of them. We show how easy-to-use formulas, already existing in the literature, emerge for narrow constituents and identify the parameter that controls the regime of their applicability.
[en] We present a coupled channel formalism which is applied to charmonium and bottonium spectroscopy. In this model we combine the quark pair creation model and the unitarized quark model. With only one new coupling parameter, γsub(QPC), fixed by hadronic widths we find considerable improvement to the mass spectra and leptonic widths (GAMMAsub(e+e-)). The problem of the large experimental value of [m(psi') - m(eta'sub(c))]/ [m(psi) - m(etasub(c))] remains difficult to understand