Development of Techniques for Measuring the Branching Ratio of Neutral B-mesons to K-short plus two Muons in the ATLAS detector at √s=13 TeV*

The rare decay of a b quark to an s quark and two leptons is not allowed at tree level in the Standard Model. Therefore, rare tree level processes beyond the Standard Model could contribute significantly to a signal. Many measurements of b→sll observables have shown tension with the Standard Model, and b→sll branching ratio measurements have shown values below predictions in many cases. Following Run 2 of the LHC, ATLAS has continued to contribute to b→sll measurements. A measurement of the branching ratio for neutral B mesons to K-short and two muons at is underway. The progress towards this measurement, which uses ATLAS's full Run 2 dataset from pp collisions at √s=13 TeV, will be discussed.