Jets faking hadronic taus get a new background estimate: multidimensional reweighting cuts the systematic uncertainty by up to 70%
CMS learns per-object multidimensional reweighting factors directly from observed data with boosted decision trees, replacing low-dimensional fake-factor parametrisations and reducing the systematic uncertainty from jets misidentified as hadronic tau decays by up to 70% on 62.4 inverse femtobarns of proton-proton collisions.