Search for exclusive hadronic decays of the W boson with ATLAS

The properties of the W boson have been studied extensively since its discovery, mostly through its leptonic decays. Many exclusive hadronic decays are also predicted by the standard model, but are yet to be observed, due to their rarity and the large associated QCD backgrounds produced in hadron colliders. These decays have been proposed as clean probes of the QCD factorisation framework, providing a context in which precise calculations can be performed. Furthermore, these largely unexplored decays could offer a new way to measure the W boson mass, through fully reconstructed, high resolution final states.
A review of past searches for the aforementioned decays is presented. The latest searches for $W^{\pm}\to \pi^{\pm} \gamma$, $W^{\pm}\to \rho^{\pm} \gamma$ and $W^{\pm} \to K^{\pm} \gamma$ at the LHC are detailed. These were performed using a dataset corresponding to 140 fb$^{-1}$, collected by the ATLAS experiment. The best upper limit on B($W^{\pm}\to \pi^{\pm} \gamma$) is reported, as well as the first experimental constraints set on B($W^{\pm}\to \rho^{\pm} \gamma$) and B($W^{\pm} \to K^{\pm} \gamma$). 

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