Study of the Λp interaction close to the Σ+n and Σ0p and Thresholds

Machner, H.; Ritman, J.; Hinterberger, F.; Haidenbauer, J.; Siudak, R.; Magiera, A.; Niskanen, J. A.

doi:10.1016/j.nuclphysa.2013.01.031

Journal Article

FZJ-2013-05108

Study of the Λp interaction close to the Σ+n and Σ0p and Thresholds

Machner, H. (Corresponding author) ; Haidenbauer, J.FZJ* ; Hinterberger, F. ; Magiera, A. ; Niskanen, J. A. ; Ritman, J.FZJ* ; Siudak, R.

2013
North-Holland Publ. Co. Amsterdam

Nuclear physics <Amsterdam> / A 901, 65 - 88 (2013) [10.1016/j.nuclphysa.2013.01.031]

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Please use a persistent id in citations: http://hdl.handle.net/2128/13264 doi:10.1016/j.nuclphysa.2013.01.031

Abstract: The $\Lambda p$ interaction close to the $\Sigma N$ threshold is considered. Specifically, the pronounced structure seen in production reactions like $K^-d \to \pi^- \Lambda p$ and $pp\to K^+ \Lambda p$ around the $\Sigma N$ threshold is analyzed. Modern interaction models of the coupled $\Lambda N - \Sigma N$ systems generate such a structure either due to the presence of a (deuteron-like) unstable bound state or of an inelastic virtual state. % A determination of the position of the prominent peak as observed in various experiments for the two aforementioned reactions leads to values that agree quite well with each other. Furthermore, the deduced mean value of $2128.7\pm 0.3$ MeV for the peak position coincides practically with the threshold energy of the $\Sigma^+ n$ channel. This supports the interpretation of the structure as a genuine cusp, signaling an inelastic virtual state in the $^3S_1-^3D_1$ partial wave of the $\Sigma N$ isospin 1/2 channel. % There is also evidence for a second peak (or shoulder) in the data sets considered which appears at roughly 10-15 MeV above the $\Sigma N$ threshold. However, its concrete position varies significantly from data set to data set and, thus, a theoretical interpretation is difficult.
The @Lp interaction close to the @SN threshold is considered. Specifically, the pronounced structure seen in production reactions like K^-d->@p^-@Lp and pp->K^+@Lp around the @SN threshold is analyzed. Modern interaction models of the coupled @LN-@SN systems generate such a structure either due to the presence of a (deuteron-like) unstable bound state or of an inelastic virtual state. A determination of the position of the prominent peak as observed in various experiments for the two aforementioned reactions leads to values that agree quite well with each other. Furthermore, the deduced mean value of 2128.7+/-0.3 MeV for the peak position coincides practically with the threshold energy of the @S^+n channel. This supports the interpretation of the structure as a genuine cusp, signaling an inelastic virtual state in the S13-^3D_1 partial wave of the @SN isospin 1/2 channel. There is also evidence for a second peak (or shoulder) in the data sets considered which appears at roughly 10-15 MeV above the @SN threshold. However, its concrete position varies significantly from data set to data set and, thus, a theoretical interpretation is difficult.

Keyword(s): Sigma: threshold ; interaction: model ; isospin: 1/2 ; partial wave ; bound state ; p p: exclusive reaction ; K- deuteron: exclusive reaction ; p Lambda: interaction ; coupled channel ; mass spectrum: (Lambda p) ; mass enhancement ; interpretation of experiments ; p p --> Lambda p K+ ; K- deuteron --> Lambda p pi- ; p p --> Sigma nucleon