Performance of the reconstruction of large impact parameter tracks in the ATLAS inner detector

The standard ATLAS track reconstruction is designed for primary charged particles, which are promptly produced from $pp$ collisions. Strict requirements on the transverse and the longitudinal impact parameters are applied to increase the purity of primary charged particle reconstruction while keeping the reconstruction efficiency high and the computation time affordable. A side effect of these criteria is a low efficiency for reconstructing secondary particles originating a significant distance from the interaction point. The addition of a second pass of track reconstruction using left-over hits, and re-optimized requirements on the transverse and longitudinal impact parameters, significantly improves the reconstruction efficiency of tracks emerging from secondary vertices which are significantly displaced from the $pp$ collision position. This dedicated setup has empowered searches for long-lived particles in models beyond the Standard Model, extending their sensitivity to a larger lifetime range, and its performance is documented in this note.