The $\eta_{c}(2980)$ formation in two-photon collisions at LEP energies

Abstract.

$\eta_{c}(2980)$ production in $\gamma\gamma$ interactions has been detected via its decays into $K^{0}_{s}K^{\pm}\pi^{\mp}$,K ⁺ K ^- K ⁺ K ^- and ${K^ + }{K^-}{\pi^ + }{\pi^-}$ in the data taken with the DELPHI detector at LEP1 and LEP2 energies. The two-photon radiative width averaged over all observed decay channels is $\Gamma_{\gamma\gamma}$ = 13.9 $\pm$ 2.0 (stat.) $\pm$ 1.4(syst.) $\pm$ 2.7 (BR) keV. No direct decay channel $\eta_c\rightarrow \pi^ + \pi^-\pi^ + \pi^-$ has been observed. An upper limit $\Gamma_{\gamma\gamma}$ < 5.5 keV at 95% confidence level has been evaluated for this decay mode.