[Rivet] ALEPH -log(xp)

[Holger Schulz]

I found a small deviation of the numbers given
in the paper and the numbers in HEPDATA.

The first bin has a yvalue of 0.0447 according to
the paper (Table 22)
and a yvalue of 0.0477 according to hepdata.

But this is presumably not enough to explain
the difference we see.

Holger