Treatment of top-quark backgrounds in extreme phase spaces: the "top $p_T$ reweighting" and novel data-driven estimations in ATLAS and CMS

The top quark plays an important role in searches for physics beyond the SM, both as a dominant background and as a key signature for the signal. The most notable feature found in the top physics analyses in both ATLAS and CMS Collaborations: the disagreement between simulation and data of the top quark $p_T$ spectrum - is highlighted. A reweighting procedure which significantly improves the agreement between simulation and data, also known as the “top $p_T$ reweighting”, is summarised. Commonly raised points concerning the reweighting to fixed-order predictions are discussed, and several refined approaches are mentioned. An overview of several data-driven methods developed and used to estimate the $t\bar{t}$ background in regions with large jet and b-jet multiplicities and/or high top quark $p_T$ is presented.