Search for the Exclusive W Boson Hadronic Decays W+- -> π+-gamma, W+- -> K+-gamma and W+- -> rho+-gamma with the ATLAS Detector

A search for the exclusive hadronic decays W±→pi±⁢gamma, W± -> K±⁢gamma, and W±->rho±⁢gamma is performed using up to 140  fb−1 of proton-proton collisions recorded with the ATLAS detector at a center-of-mass energy of sqrt(s) =13  TeV. If observed, these rare processes would provide a unique test bench for the quantum chromodynamics factorization formalism used to calculate cross sections at colliders. Additionally, at future colliders, these decays could offer a new way to measure the W boson mass through fully reconstructed decay products. The search results in the most stringent upper limits to date on the branching fractions B⁡(W±->pi±gamma)<1.9*10−6, B⁡(W±->K±⁢gamma)<1.7*10−6, B⁡(W±->rho±⁢gamma)<5.2×10−6 at 95% confidence level.