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

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

Figure 1

A Feynman diagram of $B^0\to c\overline{c}\gamma$.

Figure 2

Two dimensional ($M_{\mathrm{bc}}$, $\mathrm{\Delta }E$) distributions of the selected $B^0\to X(3872)\gamma$ candidates in the dielectron (left) and dimuon (right) channels. The signal regions are shown as rectangles.

Figure 3

$M_{\mathrm{bc}}$ (left) and $\mathrm{\Delta }E$ (right) distributions of the selected $B^0\to X(3872)\gamma$ candidates (data points with error bars), with the estimated background represented as stacked histograms. The components are, from bottom to top: the $q\overline{q}$ continuum background (purple), the $B\overline{B}$ background without $J/\psi$ (blue), and the inclusive $B\to J/\psi X$ background (green). The signal distribution (hatched brown with thick boundary) is shown corresponding to 90% C.L. upper limit.