ISSN - 15507998, Physical Review D - Particles, Fields, Gravitation and Cosmology, 2005, vol. 72, p. 1-5
Search for the b→dγ process
We report the results of a search for the flavor-changing neutral current process b→dγ using a sample of 275×106 B meson pairs accumulated by the Belle detector at KEKB. We find no significant signal for the exclusive decays B-→ρ-γ, B̄0→ρ0γ, or B̄0→ωγ. Assuming an isospin relation between the three modes, we set an upper limit for the combined branching fraction B(B→(ρ,ω)γ), of 1.4×10-6 at the 90% confidence level. This limit can be used to constrain the ratio of CKM matrix elements |Vtd/Vts|. © 2005 The American Physical Society.