Measurement of the η and η′ transition form factors at q2 = 112 GeV2

Abstract

We report a study of the processes e + e − → η γ and e + e − → η ′ γ at a center-of-mass energy of 10.58 GeV, using a 232 fb − 1 data sample collected with the BABAR detector at the PEP-II collider at SLAC. We observe 20 + 6 − 5 η γ and 50 + 8 − 7 η ′ γ events over small backgrounds, and measure the cross sections σ ( e + e − → η γ ) = 4.5 + 1.2 − 1.1 ± 0.3 fb and σ ( e + e − → η ′ γ ) = 5.4 ± 0.8 ± 0.3 fb . The corresponding transition form factors at q 2 = 112 GeV 2 are q 2 | F η ( q 2 ) | = 0.229 ± 0.030 ± 0.008 GeV , and q 2 | F η ′ ( q 2 ) | = 0.251 ± 0.019 ± 0.008 GeV , respectively.