Erlangen 2026 – wissenschaftliches Programm
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HK: Fachverband Physik der Hadronen und Kerne
HK 29: Hadron Structure and Spectroscopy V
HK 29.4: Vortrag
Donnerstag, 19. März 2026, 14:45–15:00, PHIL C 301
Search for Y state in e+e− → γ ηc at BESIII — •Yu Gang1,2, Klaus Götzen1, Frank Nerling1,2, and Klaus Peters1, 2 — 1GSI, Darmstadt — 2Goethe Universität Frankfurt
The BESIII experiment is operating since 2008 and it is well suited for charmonium spectroscopy. Since 2003, dozens of charmonium-like states have been discovered in experiment, however, their properties do not match the prediction of the charmonium quark model and the nature of these so-called XYZ states is still unknown. The most famous vector charmonium-like state Y(4260) has been discussed to be a hybrid or a tetra-quark state. In a hybrid meson, the extra gluonic degree of freedom allows for an M1 transition without spin-flip, the partial decay width Γ(Yhyb→γηc) is considerably larger than conventional vector-to-pseudoscalar transition. In phenomenology, the cross sections of exclusive γ ηc production up to NNLO in electron-positron collision with center-of-mass energy (√s) from 4.0 to 5.5 GeV has been predicted. The NNLO result prefers the enhancement in e+e− → γ ηc for center-of-mass energies between √s = 4.23 GeV and 4.36 GeV, originating from decays of the exotic particle candidate Y(4260).
Preliminary results of the energy dependent cross section measurement of e+e− → γ ηc to search for Y → γ ηc decays is presented.
Keywords: Charmonium-like state; Cross section