The two-body D0->hh exclusive lines by Charm https://gitlab.cern.ch/lhcb/Allen/-/blob/master/device/selections/lines/charm/include/D2KKLine.cuh require a cut on IP instead of IPchi2, in order to avoid possible bias on time dependent measurements. For this reason tracks with IPchi2>4 and IP>60mum should be both accepted by the prefilter.