Search for the decay $B^0\to \varphi \gamma$

We have searched for the decay $B^0\to \varphi \gamma$ using the full Belle data set of $772\times {10}^6$ $B\overline{B}$ pairs collected at the $\mathrm{\Upsilon }(4\text{S})$ resonance with the Belle detector at the KEKB $e^{+}{e}^{-}$ collider. No signal is observed, and we set an upper limit on the branching fraction of $\mathcal{B}(B^0\to \varphi \gamma )<1.0\times {10}^{-7}$ at the 90% confidence level. This is the most stringent limit on this decay mode to date.

Figure 1

Electroweak penguin (top) and gluonic penguin (bottom) contributions to $B^0\to \varphi \gamma$.

Figure 2

Projections of the four-dimensional fit: (a) $M_{\mathrm{bc}}$ in the $\mathrm{\Delta }E$ signal region; (b) $\mathrm{\Delta }E$ in the $M_{\mathrm{bc}}$ signal region; (c) $C_{\mathrm{NN}}^{\prime }$ in the $M_{\mathrm{bc}}$ and $\mathrm{\Delta }E$ signal regions; and (d) $\cos {\theta }_{\varphi }$ in the $M_{\mathrm{bc}}$ and $\mathrm{\Delta }E$ signal regions. Plots (a), (b), and (d) also require $C_{\mathrm{NN}}^{\prime }>1$. The points with error bars show the data; the dotted (red) curves represent the signal; the dashed-dotted (magenta) curves represent continuum events; the dashed (green) curves represent the charmless background; and the solid (blue) curves represent the total.