Abstract
We search for the decay \$B\_s^0\rightarrow\gamma\gamma\$ and measure the
branching fraction for \$B\_s^0\rightarrow\phi\gamma\$ using
121.4\~\$fb^-1\$ of data collected at the \$\Upsilon(5S)\$
resonance with the Belle detector at the KEKB asymmetric-energy \$e^+e^-\$
collider. The \$B\_s^0\rightarrow\phi\gamma\$ branching fraction is measured
to be \$(3.6 0.5 (stat.) 0.3 (syst.) 0.6 (f\_s))
10^-5\$, where \$f\_s\$ is the fraction of
\$B\_s^(*)B\_s^(*)\$ in \$bb\$ events. Our result is in good
agreement with the theoretical predictions as well as with a recent measurement
from LHCb. We observe no statistically significant signal for the decay
\$B\_s^0\rightarrow\gamma\gamma\$ and set a \$90\%\$ confidence-level upper
limit on its branching fraction at \$ 3.1 10^-6\$. This constitutes a
significant improvement over the previous result.
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