Jun 22 – 27, 2023
Auditorium Maximum
Europe/Warsaw timezone

A coupled-channel system with anomalous thresholds and unitarity

Jun 23, 2023, 4:45 PM
Medium lecture hall (A) (Auditorium Maximum)

Medium lecture hall (A)

Auditorium Maximum

Invited parallel Parallel session A4


Matthias F.M. Lutz (GSI Darmstadt)


A first non-perturbative and unitary treatment of multichannel systems with anomalous thresholds based on realistic potentials is presented. We consider the isospin one-half example system, with $D \,\pi , D\,\eta, D_s \bar K, D^* \pi , D^*\eta, D^*\bar K$ coupled channels in the $J^P = 1^-$ partial wave, chosen such that various phenomena that come with the opening of an anomalous threshold can be illustrated in a step-wise procedure by a suitable variation of up, down and strange quark masses. We use a set of low-energy constants in the chiral Lagrangian that were adjusted to a large set of lattice QCD results. At the physical point the $D^*$ meson decays into the $D \,\pi$ channel and an anomalous threshold develops in the $D^* \pi \leftrightarrow D^* \eta $ reaction. The six phase shifts and inelasticity parameters are presented for various choices of the pion mass. For a pion mass of 150 MeV there are no anomalous thresholds encountered. The small change from 150 MeV to 145 MeV pion mass causes a dramatic impact of the anomalous threshold on the phase shifts showing that our results are highly relevant for the extrapolation of lattice QCD calculations towards the physical pion mass.

Primary author

Matthias F.M. Lutz (GSI Darmstadt)


Csaba L. Korpa Xiao-Yu Guo Yonggoo Heo (GSI Darmstadt)

Presentation materials