A phenomenological model for the $ \overline{{K}}$
 N
 $ \rightarrow$
 K
 $ \Xi$
 reaction is suggested. The model includes s and u channel exchanges by $ \Lambda$
 , $ \Sigma$
 , $ \Sigma$
 (1385) , and $ \Lambda$
 (1520) and s channel exchanges by above-threshold hyperonic resonances. The explicit expression for the propagator for a particle with spin 7/2 is presented. High-mass and high-spin resonances play a significant role in the process. We deal with the whole set of existing experimental data on the cross-sections and polarizations in the energy range from the threshold to 2.8GeV in the center-of-mass system and reach a good agreement with experiments. Applications of the model to other elementary reactions of $ \Xi$
 production and to $ \Xi$
 hypernuclear spectroscopy are briefly discussed.

Phenomenological model for the $ \overline{{K}}$ N $ \rightarrow$ K $ \Xi$ reaction

K - p reactions from 0.960 to 1.355 GeV/ c involving two-body final states

The $\overline{K}+N\ensuremath{\rightarrow}K+\mathrm{\ensuremath{\Xi}}$ reaction is studied for center-of-momentum energies ranging from threshold to 3 GeV in an effective Lagrangian approach that includes the hyperon $s$- and $u$-channel contributions as well as a phenomenological contact amplitude. The latter accounts for the rescattering term in the scattering equation and possible short-range dynamics not included explicitly in the model. Existing data are well reproduced and three above-the-threshold resonances were found to be required to describe the data, namely, the $\mathrm{\ensuremath{\Lambda}}(1890), \mathrm{\ensuremath{\Sigma}}(2030)$, and $\mathrm{\ensuremath{\Sigma}}(2250)$. For the latter resonance we have assumed the spin-parity of ${J}^{P}=5/{2}^{\ensuremath{-}}$ and a mass of 2265 MeV. The $\mathrm{\ensuremath{\Sigma}}(2030)$ resonance is crucial in achieving a good reproduction of not only the measured total and differential cross sections but also the recoil polarization asymmetry. More precise data are required before a more definitive statement can be made about the other two resonances, in particular, about the $\mathrm{\ensuremath{\Sigma}}(2250)$ resonance that is introduced to describe a small bump structure observed in the total cross section of ${K}^{\ensuremath{-}}+p\ensuremath{\rightarrow}{K}^{+}+{\mathrm{\ensuremath{\Xi}}}^{\ensuremath{-}}$. The present analysis also reveals a peculiar behavior of the total cross-section data in the threshold energy region in ${K}^{\ensuremath{-}}+p\ensuremath{\rightarrow}{K}^{+}+{\mathrm{\ensuremath{\Xi}}}^{\ensuremath{-}}$, where the $P$ and $D$ waves dominate instead of the usual $S$ wave. Predictions for the target-recoil asymmetries of the $\overline{K}+N\ensuremath{\rightarrow}K+\mathrm{\ensuremath{\Xi}}$ reaction are also presented.

K ¯ + N → K + Ξ reaction and S = − 1 hyperon resonances

In the light baryon sector resonances can be broad and overlapping and are in most cases not directly visible in the cross section data. Automatized model selection techniques that introduce penalties for resonances can be used to determine the minimally needed set of resonances to describe the data. Several possible penalization schemes are compared. As an application we perform a blindfold identification of hyperon resonances in the $\bar{K} N \to K \Xi$ reaction based on the Least Absolute Shrinkage and Selection Operator (LASSO) in combination with the Bayesian Information Criterion (BIC). We find ten resonances --- out of the 21 above-threshold hyperon resonances with spin $J\le 7/2$ listed by the Particle Data Group. In traditional analyses, it is practically impossible to test the relevance of all resonances and their combinations that may potentially contribute to the reaction. By contrast, the present method proves capable of determining the relevant resonances among a large pool of candidates.

Towards the minimal spectrum of excited baryons

We give the cross-sections of quasi-two-body reactions produced in K−-proton interactions at 13 different energies in the centreof-mass energy range 1.915 to 2.168 GeV.

Cross-sections for quasi-two-body reactions in K−p interactions between 1263 and 1843 MeV/c

We present the results on total channel cross-sections obtained in the Saclay 180 l HBC exposed to a separated K− beam at Nimrod. The cross-sections for each channel are given at 13 incident K− momenta between 1.26 and 1.84 GeV/c.

L.K. Rangan

Papers

Channel cross-sections of K−p reactions from 1.26 to 1.84 GeV/c

Study of the decay mode η→π+π−γ