Improved description of the di-tau final state in events with associated production of a $W$ boson and jets in the ATLAS detector using the tau-promotion method

The production of $W$ bosons and jets in the ATLAS detector is the main irreducible contribution in many analyses that select events with two reconstructed hadronically decaying tau leptons. The number of simulated events that are used to model this background is limited by the CPU resources available for the Monte Carlo simulation. In searches for new physics with two tau leptons in the final state, this limitation may have a deleterious effect on the estimation of the background and ultimately on the sensitivity of the analysis to new physics. This note presents a method to reduce the statistical uncertainties from Monte Carlo simulation of the associated production of a $W$ boson together with jets for searches that contain two hadronically decaying tau leptons in the final state. The results of the method are presented in an example case, with a comparison to the nominal predictions from simulation.