ISSN - 15507998, Physical Review D - Particles, Fields, Gravitation and Cosmology, 2012, vol. 85, p. -
Measurement of B0→J/ψη(′) and constraint on the η-η′ Mixing angle
We measure the branching fractions of B0→J/ψη( ′) decays with the complete Belle data sample of 772×106 BB̄ events collected at the Υ(4S) resonance with the Belle detector at the KEKB asymmetric-energy e +e - collider. The results for the branching fractions are: B(B0→J/ψη)=(12.3±1.71. 8±0.7)×10 -6 and B(B0→J/ψη′)<7. 4×10 -6 at 90% confidence level. The η-η′ mixing angle is constrained to be less than 42.2° at 90% confidence level. © 2012 American Physical Society.