Measurement of γγ→pp¯ production at Belle

A high precision study of the process γγ→pp¯ has been performed using a data sample of 89 fb−1 collected with the Belle detector at the KEKB e+e− collider. The cross section of pp¯ production has been measured at two-photon center-of-mass (c.m.) energies between 2.025 and 4.0 GeV and in the c.m. angular range of |cosθ∗|<0.6. Production of γγ→ηc→pp¯ is observed and the product of the two-photon width of the ηc and its branching ratio to pp¯ is determined.