and $\abs{\eta} < 2.5$ or $<$2.4 for electrons and muons, respectively, and reject any events with a -tagged jet to suppress top quark backgrounds. A requirement of $\abs{\Delta\phi(\tauh^{(1)},\tauh^{(2)})} > 1.5$ helps to suppress the DY+jets background, while retaining high signal efficiency. Finally, we require $\ptmiss>50\GeV$ to suppress the QCD multijet background.

=900 The removal of low-jets in the forward ECAL region from the calculation in 2017 (see Section \[sec:evtreco\]) causes the background originating from DY+jets and other sources to increase in the SRs, since events with low-jet activity in that region are assigned larger values of reconstructed . We recover some of the corresponding loss in sensitivity in the 2017 analysis by placing an upper bound of 50on the scalar sum of low-jets excluded from the calculation ($\HT^{\text{low}}$). This restriction reduces the impact of background events with significant low-jet activity in the forward region, for which the would be overestimated. To ensure that the efficiency of this requirement is correctly estimated in simulation, a [$\PZ\to\PGm^{+}\PGm^{-}$]{}CR is used to extract correction factors for the $\HT^{\text{low}}$ distribution in simulation that account for discrepancies with the distribution observed in data. The correction factors range from 0.8 for $\HT^{\text{low}}<10\GeV$ to 1.4 for $\HT^{\text{low}}>60\GeV$. In 