An embedding technique to determine genuine $\tau\tau$ backgrounds from CMS data

The embedding technique allows an estimation of the genuine $\tau\tau$ standard model backgrounds from data, with minimal simulation input. In the data, the muons are removed from reconstructed $\mu\mu$ events and replaced with simulated tau leptons with the same kinematic properties. In that way a set of hybrid events is obtained that relies on simulation only for the decay of the tau leptons. Challenges in describing the underlying event or the production of associated jets in the simulation are avoided. In this note the technique developed for the CMS experiment is described, and its validation and relevant uncertainties are discussed. The description is based on the experimental setup of the year 2017. The data sample of proton-proton collisions at $\sqrt{s}=13~\mathrm{TeV}$ collected by the CMS experiment is used to demonstrate the performance of the method. It corresponds to an integrated luminosity of $41.5~\mathrm{fb}^{-1}$.