Search for the Decay \(B^0\rightarrow \gamma \gamma \) at  \(\Upsilon \) (4S) Resonance

We search for the decay of \(B^0\rightarrow \gamma \gamma \) using 711 \(fb^{-1}\) of data collected at \(\Upsilon \) (4S) resonance by the Belle detector at the KEKB asymmetric energy \(e^+e^-\) collider located at KEK, Japan. It is a Flavor Changing Neutral Current (FCNC) process which can be described by a penguin loop diagram in the leading order. The decay process is yet to be observed with an expected branching ratio of \(3\times 10^{-8}\) in the Standard Model (SM). The decay is sensitive to New Physics (NP) beyond the SM, since a new particle, such as a charged Higgs, may enter the penguin loop and can change its branching ratio. The best previous experimental upper limit ( \(\texttt {UL}\) ) on the branching ratio for this decay is \(3.3\times 10^{-7}\) at \(90\%\) confidence level ( \(\texttt {CL}\) ) set by the BaBar experiment using 426 \(fb^{-1}\) data. The Belle collaboration has also put an \(\texttt {UL}\) on its branching ratio at \(6.2\times 10^{-7}\) at \(90\%\) \(\texttt {CL}\) using 104 \(fb^{-1}\) of data. Using the final dataset from the Belle experiment, we expect to reach the SM sensitivity for this decay.