Modelling of Track Reconstruction Inside Jets with the 2016 ATLAS $\sqrt{s}= 13$ TeV pp dataset

Inside the core of high transverse momentum jets, the particle density is so high that the tracks of charged particles begin to overlap, and due to the different charged particles, pixel clusters in the ATLAS inner detector begin to merge. This high density environment results in a degradation of track reconstruction. Recent innovations to the ambiguity solving in the charged particle pattern recognition partially mitigate the loss in performance. However, it is critical for all physics results using tracks inside jets that the algorithms be well modeled by simulation. This note presents new measurements of the charged particle reconstruction inefficiency and fake rate inside jets with the $\sqrt{s}=13$ TeV $pp$ dataset collected by the ATLAS experiment at the LHC in 2016.