https://doi.org/10.1140/epja/s10050-022-00767-x
Regular Article - Theoretical Physics
The 
resonance as a genuine three-quark or molecular state
1
Faculty of Education, University of Ljubljana and J. Stefan Institute, 1000, Ljubljana, Slovenia
2
Faculty of Natural Sciences and Mathematics, University of Tuzla, 75000, Tuzla, Bosnia and Herzegovina
3
Faculty of Mathematics and Physics, University of Ljubljana and J. Stefan Institute, 1000, Ljubljana, Slovenia
Received:
6
April
2022
Accepted:
12
June
2022
Published online:
1
July
2022
The mechanism for the formation of the resonance is studied in a chiral quark model that includes quark-meson as well as contact (four point) interactions. The negative-parity S-wave scattering amplitudes for strangeness 
and 1 are calculated within a unified coupled-channel framework that includes the KN, 
, 
, 
, 
, 
, and 
channels and possible genuine three-quark bare singlet and octet states corresponding to 
resonances. It is found that in order to reproduce the scattering amplitudes in the 
partial wave it is important to include the pertinent three-quark octet states as well as the singlet state, while the inclusion of the contact term is not mandatory. The Laurent-Pietarinen expansion is used to determine the S-matrix poles. Following their evolution as a function of increasing interaction strength, the mass of the singlet state is strongly reduced due to the attractive self-energy in the and channels; when it drops below the KN threshold, the state acquires a dominant component which can be identified with a molecular state. The attraction between the kaon and the nucleon is generated through the 
interaction rather than by meson-nucleon forces.
© The Author(s), under exclusive licence to Società Italiana di Fisica and Springer-Verlag GmbH Germany, part of Springer Nature 2022
