Search for $B^0 \to X(3872) \gamma$

We report the results of a search for the decay $B^0 → X(3872)(→ J/ψ π^+ π^−)γ$. The analysis is performed on a data sample corresponding to an integrated luminosity of 711fb$^{−1}$ and containing $772 \times 10^6 B\bar{B}$ pairs, collected with the Belle detector at the KEKB asymmetric-energy $e^+ e^−$ collider running at the $Υ(4S)$ resonance energy. We find no evidence for a signal and place an upper limit of $\mathcal{B}(B^0 → X(3872)γ) \times \mathcal{B}(X(3872) → J/ψ π^+ π^−) < 5.1 \times 10^{−7}$ at 90% confidence level.