Speaker
Dr
Hideyuki Nakazawa
(National Central University)
Description
The invariant mass spectrum of the $\eta' \pi^+ \pi^-$ final state produced in two-photon collisions is obtained using 673 fb$^{-1}$ of data on and off the $\Upsilon(4S)$ collected with the Belle detector at the KEKB asymmetric-energy $e^+ e^-$ collider. The $\eta_c$ mass, width and the product of the two-photon width and the branching fraction of the decay into $\eta' \pi^+ \pi^-$ are measured. We also report the first evidence for the $\eta(1760)$ decays to $\eta' \pi^+\pi^-$. From a fit of the mass spectrum with the coherent $X(1835)$ and $\eta(1760)$ resonances, we set a 90% confidence level upper limit on the product $\Gamma_{\gamma\gamma} {\cal B}$ for the $X(1835)$.
Author
Dr
Hideyuki Nakazawa
(National Central University)
