Jul 4 – 11, 2018
Asia/Seoul timezone

Study of K^0_S pair production and eta_c(1S), eta_c(2S) and non-resonant eta' pi+ pi- in two-photon collisions at Belle

Jul 7, 2018, 5:15 PM
101 (COEX, Seoul)


COEX, Seoul

Parallel Strong Interactions and Hadron Physics Strong Interactions and Hadron Physics


Qingnian Xu (University of Chinese Academy of Sciences (CN))


We report the measurements of gamma gamma ―> eta_c(1S), eta_c(2S)―>eta' pi+ pi- with eta' decay to gamma rho and eta pi+ pi- First observation of eta_c(2S)―>eta' pi+ pi- with a significance 5.5 \sigma including systematic error is obtained. The products of the two-photon decay width and branching fraction of decays to eta' pi+ pi- are determined for the eta_c(1S) and eta_c(2S), respectively. A new decay mode for the eta_c(1S)―>eta' f0(2080) with f0(2080)―>pi+ pi- is observed with a statistical significance of 20 \sigma. The cross section for gamma gamma ―> eta' pi+ pi- and eta’ f2(1270) are measured for the first time. We also report a measurement of the cross section for K^0_S pair production in single-tag two-photon collisions, gamma gamma → K^0_S K^0_S for Q^2 up to 30 GeV^2, where Q^2 is the negative of the invariant mass squared of the tagged photon. The measurement covers the kinematic range 1.0 GeV < W < 2.6 GeV and |cos theta|<1.0 for the total energy and kaon scattering angle, respectively, in the gamma* gamma center-of-mass system. For the first time, the transition form factor of the f'2(1525) meson is measured separately for the helicity-0, -1, and -2 components and also compared with theoretical calculations. Finally, the partial decay widths of the chi_c0 and chi_c2 mesons are measured as a function of Q^2. The results are based on a data sample collected with the Belle detector at the KEKB asymmetric-energy e+ e- collider.

Primary authors

Shohei Nishida (KEK) Qingnian Xu (University of Chinese Academy of Sciences (CN))

Presentation materials