The cross section of e+e-→ΛΣ¯0+c.c. as a litmus test of isospin violation in the decays of vector charmonia into ΛΣ¯0+c.c

• Published in: The European physical journal. C, Particles and fields Particles and fields, 2020-09, Vol.80 (9)
• Main Authors: Ferroli, Rinaldo Baldini, Mangoni, Alessio, Pacetti, Simone
• Format: Article
• Language: English
• Subjects: Amplitudes; Astronomy; Astrophysics and Cosmology; Born approximation; Cross-sections; Decay; Electromagnetic coupling; Elementary Particles; Hadrons; Heavy Ions; Measurement Science and Instrumentation; Nuclear Energy; Nuclear Physics; Physics; Physics and Astronomy; Quantum Field Theories; Quantum Field Theory; Regular Article – Theoretical Physics; String Theory
• ISSN: 1434-6044; 1434-6052
• DOI: 10.1140/epjc/s10052-020-08474-x

Under the aegis of isospin conservation, the amplitudes in Born approximation, i.e., considering the only one-photon-exchange mechanism, of the decay ψ → Λ Σ ¯ 0 + c.c. , where ψ is a vector charmonium, and of the reaction e + e - → Λ Σ ¯ 0 + c.c. at the ψ mass, are parametrized by the same electromagnetic coupling. It follows that, the modulus of such a coupling can be extracted from the data on the two observables: the decay branching fraction and the annihilation cross section. By considering the first two vector charmonia, J / ψ and ψ ( 2 S ) , it is found that, especially in the case of ψ ( 2 S ) , there is a substantial discrepancy between the values of the modulus of the same electromagnetic coupling extracted from the branching ratio and the cross section. We propose, as a possible explanation for such a disagreement, the presence in the decay amplitude of isospin-violating contributions driven by two different mechanisms, that, however, appear to be more favored in the ψ ( 2 S ) than in the J / ψ decays.