Study of the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>B</mml:mi><mml:mo>→</mml:mo><mml:mi>X</mml:mi><mml:mo stretchy="false">(</mml:mo><mml:mn>3872</mml:mn><mml:mo stretchy="false">)</mml:mo><mml:mo stretchy="false">(</mml:mo><mml:mo>→</mml:mo><mml:msup><mml:mi>D</mml:mi><mml:mrow><mml:mo>*</mml:mo><mml:mn>0</mml:mn></mml:mrow></mml:msup><mml:msup><mml:mover accent="true"><mml:mi>D</mml:mi><mml:mo>¯</mml:mo></mml:mover><mml:mn>0</mml:mn></mml:msup><mml:mo stretchy="false">)</mml:mo><mml:mi>K</mml:mi></mml:math>decay

We present a study of $B\ensuremath{\rightarrow}X(3872)K$ with $X(3872)$ decaying to ${D}^{*0}{\overline{D}}^{0}$ using a sample of $657\ifmmode\times\else\texttimes\fi{}{10}^{6}$ $B\overline{B}$ pairs recorded at the $\ensuremath{\Upsilon}(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy ${e}^{+}{e}^{\ensuremath{-}}$ collider. Both ${D}^{*0}\ensuremath{\rightarrow}{D}^{0}\ensuremath{\gamma}$ and ${D}^{*0}\ensuremath{\rightarrow}{D}^{0}{\ensuremath{\pi}}^{0}$ decay modes are used. We find a peak of ${50.1}_{\ensuremath{-}11.1}^{+14.8}$ events with a mass of $({3872.9}_{\ensuremath{-}0.4\ensuremath{-}0.5}^{+0.6+0.4})\text{ }\text{ }\mathrm{MeV}/{c}^{2}$, a width of $({3.9}_{\ensuremath{-}1.4\ensuremath{-}1.1}^{+2.8+0.2})\text{ }\text{ }\mathrm{MeV}/{c}^{2}$ and a product branching fraction $\mathcal{B}(B\ensuremath{\rightarrow}X(3872)K)\ifmmode\times\else\texttimes\fi{}\mathcal{B}(X(3872)\ensuremath{\rightarrow}{D}^{*0}{\overline{D}}^{0})=(0.80\ifmmode\pm\else\textpm\fi{}0.20\ifmmode\pm\else\textpm\fi{}0.10)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$, where the first errors are statistical and the second ones are systematic. The significance of the signal is $6.4\ensuremath{\sigma}$. The difference between the fitted mass and the ${D}^{*0}{\overline{D}}^{0}$ threshold is calculated to be $({1.1}_{\ensuremath{-}0.4\ensuremath{-}0.3}^{+0.6+0.1})\text{ }\text{ }\mathrm{MeV}/{c}^{2}$. We also obtain an upper limit on the product of branching fractions $\mathcal{B}(B\ensuremath{\rightarrow}Y(3940)K)\ifmmode\times\else\texttimes\fi{}\mathcal{B}(Y(3940)\ensuremath{\rightarrow}{D}^{*0}{\overline{D}}^{0})$ of $0.67\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$ at 90% CL.