X iv : n uc l - th / 9 90 40 02 v 1 1 A pr 1 99 9 S - matrix poles near the Thresholds in the Coupled Λ N − Σ N System
نویسنده
چکیده
We search t-matrix poles for the ΛN − ΣN coupling interaction. The two soft core models of the Nijmegen group which bind the hypertriton at the correct binding energy and the hard core models which are still influential on hypernuclear physics are investigated. A useful method of calculating the off-shell t-matrix of a hard core potential is proposed. We find poles close to the ΣN threshold in the second or third quadrant of the complex plane of the ΣN relative momentum. The relation between the nearby poles and the shape of the ΛN elastic total cross section is discussed based on a socalled uniformization by which two-channel t-matrices become single-valued on a complex valuable. We find also poles near the ΛN threshold. Those are correlated to the S-wave ΛN scattering lengths the values of which have not yet been determined. 13.75.Ev, 21.45.+v, 21.30.-x, 21.80+a Typeset using REVTEX 1
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