Observation of e + e - → γχ c1 and search for e + e - → γχ c0 , γχ c2 , and γη c at √s near 10.6 GeV at Belle

Abstract

Using data samples of 89.5 fb-1, 711.0 fb-1, and 121.4 fb-1 collected with the Belle detector at the KEKB asymmetric-energy e+e- collider at center-of-mass energies 10.52, 10.58, and 10.867 GeV, respectively, we study the exclusive reactions e+e-→γχcJ (J=0, 1, 2) and e+e-→γηc. A significant γχc1 signal is observed for the first time at s=10.58 GeV with a significance of 5.1σ including systematic uncertainties. No significant excesses for γχc0, γχc2, and γηc final states are found, and we set 90% credibility level upper limits on the Born cross sections (σB) at 10.52 GeV, 10.58 GeV, and 10.867 GeV. Together with cross sections measured by BESIII at lower center-of-mass energies, the energy dependency of σB(e+e-→γχc1) is obtained.