Speaker
Hideyuki Nakazawa
(National Central University)
Description
* Experimental study of eta eta production in two-photon collisions
The differential cross section for the process gamma gamma -> eta eta has been measured in the kinematic range above the eta eta threshold, 1.096 GeV < W < 3.8 GeV, in almost the whole solid angle, |cos theta*| < 0.9 or < 1.0 depending on W, where W and theta* are the energy and eta scattering angle, respectively, in the gamma gamma center-of-mass system. This is the first measurement of the cross section for this process. The results are based on a 393~fb^-1 data sample collected with the Belle detector at the KEKB e+e- collider. In the W range 1.1-2.0 GeV/c2 we perform an analysis of resonance amplitudes for various partial waves; at higher energy we extract the contributions of chi_cJ charmonia and compare the energy and angular dependence of the cross section with the predictions of theoretical models.
* Observation of eta_c(2S) in six-prong final states produced in two-photon collisions
We report the observation of eta_c(2S), produced in two-photon collisions, and decaying to the six-prong final states 3(pi+pi-), K+ K- 2(pi+ pi-), and K0_S K+ pi- pi+ pi- (including the charge-conjugate state). This analysis is based on a large data sample accumulated by the Belle experiment at the KEKB asymmetric-energy electron-positron collider. This is the first observation of decay modes of the eta_c(2S) other than K0_S K+ pi-.
