Example with CIRCE1 from manual gives zero xsec

[Juergen Reuter]

Reported by Jan Strube on Oct. 26, apparently at that time it was on p. 96 of the manual. It is the following example:

process proc1 = A, A => Wp, Wm
sqrts = 500 GeV
beams = e1, E1 => circe1
?circe1_photon1 = true
?circe1_photon2 = true

I don't put that on CIRCE1, because it is the setup of the new structure functions changed from WHIZARD 2.1 to 2.2 that triggered that issue.

[kilian]

Investigating ... (suspicious)

[kilian]

OK, very simple. Nothing is wrong with the program.

For this particular process, the generator mode of CIRCE1 is unusable. At 500 GeV, the CIRCE1 generator will produce essentially zero gamma-gamma events above the W-pair threshold. Some time ago, we agreed on making the generator mode the default. Here is the counterexample.

Setting

?circe1_generate = false

solves the problem.

The issue itself may be closed as invalid, but do we keep the example, should we modify it, or just delete it?

[Juergen Reuter]

Yes, we should keep it in the manual with the additional ?circe1_generate = false. I think, that was the original intention. When WK refactored the structure functions, the generator mode became the default.

[kilian]

I added the line in the example in the manual, and wrote a paragraph explaining this.

[Juergen Reuter]

Milestone renamed