Comment 2 for bug 1560075

Hi,

Something realy funny seems to appear here.
Some of the helicity are sometimes extremelly suppressed while contributing for 50% of the cross-sections.
Such behavior make the helicity selector to sometimes discard those helicities and this creates some fake determination of the cross-sections.

The solution is to be more conservative on that selection of helicity.
This can be done by modifying Template/LO/Source/genps.inc

you can modify the lines:
c Parameters for helicity sums in matrixN.f
c*************************************************************************
      REAL*8 LIMHEL
      PARAMETER(LIMHEL=1e-6)
      INTEGER MAXTRIES
      PARAMETER(MAXTRIES=10)

I have set LIMHEL to 1e-9 and then I do not observe such behavior anymore (in 65 different consecutive run).
increasing MAXTRIES should help as well.

I will do a combination of both for the next release.

Cheers and thanks for the information,

Olivier

PS: I still have 35 run schedule, I will keep you posted if any or those have the buggy behavior.