Search for the rare decay $W\rightarrow D_s \gamma$ at CMS

A search for the rare decay $W\rightarrow D_s \gamma$ is performed using proton-proton collision data collected by the CMS experiment at a centre-of-mass energy of 13 Tev in year 2018. With simulation sample generated by PYTHIA8, an investigation into the characteristics of the decay mode of the $D_s$ meson, specifically limited to the final state involving $KK\pi$, has been undertaken at both the generate and reconstruction levels. Ultimately, using approximately 10 fb$^{-1}$ of the collision data, the expected upper limit for the signal branching fraction that can currently be provided is \begin{equation*} BR(W^{\pm} \rightarrow D_{s}^{\pm}\gamma ) < 8.48 \times 10^{-4} \end{equation*} at a 95% confidence level. This is a first and prospective search for the $W\rightarrow D_s \gamma$ decay in CMS experiment, while the upper limit on branching fraction holds the potential to improves upon the previous best limit.