Evolution of the mass bias and the distance between the centres of the host and infalling halos during the major merger. The red curve shows the hydrostatic mass bias (red line and right axis) evolution during the major merger event for the galaxy cluster CL1. The colour of the markers over the bias curve indicates the dynamical state according to the colour code detailed in the legend. The connected dots with error bars show the radial distance (orange line) between the CM and the density peak (purple line) of the merging halo with respect to the host (left axis). The star-shaped scatter point is the parabolic interpolation of the pericentre for the infalling orbit.