cross-correlation peak at position 0 when calculating ChIp-Seq

Question

[Assa Yeroslaviz]

Not sure how to interpret my results of the fragment length. I'm using the phantompeakqualtools to calculate the fragment length of my data. When calculating the so-called phantom peaks, I get the hoghest peak at 0.

What does the blue line in the plot mean? 100-110 might make sense in the data, but why does the highest peak ist at 0?

thanks

Assa