Analysis of the ψ(3770) resonance in line with unitarity and analyticity constraints

• Published in: The European physical journal. C, Particles and fields Particles and fields, 2024-05, Vol.84 (5), p.483-12
• Main Authors: Hanhart, Christoph, Kürten, Stephan, Reboud, Méril, van Dyk, Danny
• Format: Article
• Language: English
• Subjects: Astronomy; Astrophysics and Cosmology; Couplings; Elementary Particles; Hadrons; Heavy Ions; Line shape; Measurement Science and Instrumentation; Nuclear Energy; Nuclear Physics; Particle physics; Physics; Physics and Astronomy; Quantum Field Theories; Quantum Field Theory; Regular Article - Theoretical Physics; Resonance; Statistical analysis; Statistical models; String Theory; Theoretical physics; Upper bounds
• ISSN: 1434-6044; 1434-6052
• DOI: 10.1140/epjc/s10052-024-12785-8

We study the inclusive and exclusive cross sections of e + e - → hadrons for center-of-mass energies between 3.70 and 3.83 GeV to infer the mass, width, and couplings of the ψ ( 3770 ) resonance. By using a coupled-channel K -matrix approach, we setup our analysis to respect unitarity and the analyticity properties of the underlying scattering amplitudes. We fit several models to the full dataset and identify our nominal results through a statistical model comparison. We find that, accounting for the interplay between the ψ ( 2 S ) and the ψ ( 3770 ) , no further pole is required to describe the ψ ( 3770 ) line shape. In particular we derive from the pole location M ψ ( 3770 ) = 3778.8 ± 0.3 MeV and Γ ψ ( 3770 ) = 25.0 ± 0.5 MeV . Moreover, we find the decay to D + D - and D 0 D ¯ 0 to be consistent with isospin symmetry and derive an upper bound on the branching ratio B ( ψ ( 3770 ) → non- D D ¯ ) < 6 % at 90 % probability.