e+e- events with ISR and pythia showering
Affects | Status | Importance | Assigned to | Milestone | |
---|---|---|---|---|---|
MadGraph5_aMC@NLO |
New
|
Undecided
|
Unassigned |
Bug Description
Dear MG team,
I came across an issue when Pythia8 is showering LHE events produced in MG for e+e- collisions with ISR.
I generated e+e->ZH samples with Madgraph v3.5.4 with ebeam1=ebeam2=120 and with ISR turned on (set lpp1 -3, set lpp2 +3, set pdlabel isronlyll), then run Pythia8 which stops showering events after a certain point.
Pythia complains for LHE events with the energy of one of the beams larger than 120 GeV, which is instead what is set to be the energy in the <init> part of the LHE file. According to a Pythia developer, this could be a round-off error or a boost error, but the error is coming from the LHE file (Madgraph).
For more information on the Pythia error please refer to this git issue opened by the Py8 developer: https:/
An LHE file produced with Madgraph with 22 events to reproduce the error can be downloaded from this link: https:/
Do you have any idea of what is happening and if it's possible to run py8 for showering MG events with ISR?
Thank you in advance!
Cheers,
Matteo
Yeah given that that the error is that
1.2000071365e+02 > 120
So indeed the mismatch is small so it makes sense to investigate boost issue.
And clearly this is a mistake on our side and not pythia8 side. I will take a deeper look.
Cheers,
Olivier