English to Italian Tech/Engineering Mathematics & Statistics

Nella frase seguente, non riesco a capire a che cosa si riferisce "after which" (all'intervallo o alle intersezioni)

Determining the first peak-valley cycle

Where the profile data is, in the beginning, below the mean line. After exceeding the dead zone, the data drops below the dead zone at least once, and now is above the dead zone. In the above series of events, the interval between the intersections of the profile and mean
line, immediately after which each piece of profile data exceeds the dead zone, is defined as the first one cycle.