Search for B+→X(3872)K+, X(3872)→J/ψγ

In a study of B+→J/ψγK+ decays, we find evidence for the radiative decay X(3872)→J/ψγ with a statistical significance of 3.4σ. We measure the product of branching fractions B(B+→X(3872)K+)·B(X(3872)→J/ψγ)=(3.3±1.0±0.3)×10-6, where the uncertainties are statistical and systematic, respectively. We also measure the branching fraction B(B+→χc1K+)=(4.9±0.2±0.4)×10-4. These results are obtained from (287±3) million BB̅ decays collected at the Υ(4S) resonance with the BABAR detector at the PEP-II B Factory at SLAC.