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HK: Hadronen und Kerne

HK 43: Nuclear Forces III, Reactions, Resonances

HK 43.6: Vortrag

Dienstag, 17. März 1998, 18:45–19:00, J

Disappearing resonances in coupled two-channel model — •W Vanroose, F Arickx, J Broeckhove, and P Van Leuven — Universiteit Antwerpen, Groenenborgerlaan 171, B-2020 Antwerpen, Belgium.

Broad resonances in coupled channels play an important role in few-body physics. They are present in the study of continuum effects of monopole and quadropole degrees of freedom in collective motion [1]. We see them also in hypernuclear physics and mesonscattering. A study of simple modelproblems can give insight in such broad resonances.

In a two channel model, which consists of square wells as potentials in the channels and a square well as coupling between them, particular resonances are invisible in the phaseshift for special depths of the wells.

If we look at the complex poles of the S-matrix in such a model we get a different view on this disappearence. There are two poles: a Feshbach pole and a potential pole. The trajectories these poles make when the depth of the well are changed, show a critical behaviour [2]. This critical behaviour forces the resonance to “disappear” (Γ > E) for certain model parameters.

Analogue critical behaviour is present in models with separable potentials.

[1] Vasilevsky V et al. Phys G: nuclear physics, 18 (1992) 1227-1242

[2] Vanroose W et al J. Phys A: Math. Gen. 30 (1997) 5543-5549