We discuss effective range expansion in a two-channel system and establishing the nature of a near-threshold hadronic resonance with the help of parameters obtained from a fit to experimental data. In particular, the situation of two strong thresholds located close to each other and a hadronic resonance residing at the lower of them is considered. For the case of a bound state, simple expressions are derived that allow one to estimate the probability of finding the given resonance in each hadronic channel and as a compact quark state if the resonance wave function contains such a component.

Keywords: exotic hadrons, near-threshold resonance, effective range expansion PACS: 11.55.Bq, 14.40.Pq, 14.40.Rt (all) DOI: 10.3367/UFNe.2022.07.039225 URL: https://ufn.ru/en/articles/2024/1/f/ 2-s2.0-85186562233 2024PhyU...67...71N Citation: Nefediev A V "On effective range expansion in a multichannel system and compositeness of near-threshold resonance" Phys. Usp. 67 71–79 (2024) BibTexBibNote ® (generic)BibNote ® (RIS)MedlineRefWorks Received: 30th, March 2022, revised: 27th, June 2022, accepted: 28th, July 2022 Оригинал: Нефедьев А В «О разложении эффективного радиуса в многоканальной системе и молекулярности околопорогового резонанса» УФН 194 77–85 (2024); DOI: 10.3367/UFNr.2022.07.039225