A study of the ground-state properties of charmonium via radiative transitions in ψ ' → γηc and J/ψ → γηc
|PhD ceremony:||Ms Z. (Zahra) Haddadi|
|When:||December 08, 2017|
|Supervisor:||prof. dr. N. (Nasser) Kalantar-Nayestanaki|
|Co-supervisors:||dr. J.G. (Johan) Messchendorp, dr. M. (Myroslav) Kavatsyuk|
|Where:||Academy building RUG|
This thesis is devoted to a systematic analysis of the radiative M1 transitions of the two lowest lying vector-meson states, J/ψ and ψ', to the ground state, ηc. Data were taken with BESIII using the world's highest statistics in electron-positron annihilations. For both studies, we analysed data collected at a center-of-mass energy corresponding to the nominal mass of the ψ' resonance. An inclusive analysis was carried out with the aim to provide a measurement of the M1 transition rate of ψ'→ γηc . In addition, the M1 transition rate of J/ψ → γηc has been obtained via the exclusive process, ψ'→ππJ/ψ, J/ψ → γηc , ηc → KsKπ. The latter reaction gave access to a complementary measurement of the mass and the natural width of the ηc. In all cases, the distortion of the line shape of the ηc has been accounted for by considering an interference effect between the decay of the ηc resonance with other processes that have the same final-state.