Left panel: Dip events in the X-ray and optical light curves of MAXI J1820+070. For convenient reference to the period of the occurrence of optical superhump discussed in Thomas et al. (2022) and the X-ray/optical dips, we adopted the start date as used by them (i.e. day 0 is MJD 58188.0). The vertical solid black line (day 87) marks the onset of large-amplitude optical modulation at the superhump period. The interval between the two vertical dashed red lines is the IMS. Right panel: Cross-correlation analysis between the optical (V band) and 2−10 keV X-ray (Insight-HXMT) light curves. The red line shows the cross-correlation function (left axis). The dashed and dotted blue histograms represent the cross-correlation centroid lag distribution and the peak lag distribution, respectively (right axis).