Evidence for $X(3872)\to \psi (2S)\gamma$ in $B^{\pm }\to X(3872)K^{\pm }$ Decays and a Study of $B\to c\overline{c}\gamma K$

In a search for $B\to c\overline{c}\gamma K$ decays with the BABAR detector, where $c\overline{c}$ includes $J/\psi$ and $\psi (2S)$, and $K$ includes $K^{\pm }$, $K_S^0$, and $K^{*}(892)$, we find evidence for $X(3872)\to J/\psi \gamma$ and $X(3872)\to \psi (2S)\gamma$ with $3.6\sigma$ and $3.5\sigma$ significance, respectively. We measure the product of branching fractions $\mathcal{B}\mathbf{(}{B}^{\pm }\to X(3872)K^{\pm }\mathbf{)}\times \mathcal{B}\mathbf{(}X(3872)\to J/\psi \gamma \mathbf{)}=[2.8\pm 0.8(\mathrm{stat})\pm 0.1(\mathrm{syst})]\times {10}^{-6}$ and $\mathcal{B}\mathbf{(}{B}^{\pm }\to X(3872)K^{\pm }\mathbf{)}\times \mathcal{B}\mathbf{(}X(3872)\to \psi (2S)\gamma \mathbf{)}=[9.5\pm 2.7(\mathrm{stat})\pm 0.6(\mathrm{syst})]\times {10}^{-6}$.

Figure 1

${}_s\mathrm{Plot}$ of the number of signal events versus $m_X$ for (a) $B^{\pm }\to {\chi }_{c1,2}{K}^{\pm }$, (b) $B^0\to {\chi }_{c1,2}{K}_S^0$, (c) $B^{\pm }\to {\chi }_{c1,2}{K}^{*\pm }$, and (d) $B^0\to {\chi }_{c1,2}{K}^{*0}$. The solid curve is the fit to the data.

Figure 2

${}_s\mathrm{Plot}$ of the number of extracted signal events versus $m_X$ for (a) $B^{\pm }\to X(3872)K^{\pm }$, (b) $B^0\to X(3872)K_S^0$, (c) $B^{\pm }\to X(3872)K^{*\pm }$, and (d) $B^0\to X(3872)K^{*0}$, where $X(3872)\to J/\psi \gamma$. The solid curve is the fit to the data.

Figure 3

${}_s\mathrm{Plot}$ of the number of extracted signal events versus $m_X$ for (a) $B^{\pm }\to X(3872)K^{\pm }$, (b) $B^0\to X(3872)K_S^0$, (c) $B^{\pm }\to X(3872)K^{*\pm }$, and (d) $B^0\to X(3872)K^{*0}$, where $X(3872)\to \psi (2S)\gamma$. The solid curve is the fit to the data.