No negative weights in NLO process

Hi,

If you want to convert to something human readable, I would suggest to convert those to hepmc.
This will be much better.
The problem with the converter that you use is that
1) It is designed for LO and was never tested on NLO events.
2) It use a non infra-red safe cluster algorithm which does not make fully sense @NLO

Cheers,

Olivier

On 12 Oct 2015, at 21:26, Josef Stanton <email address hidden> wrote:

> New question #272345 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/272345
>
> I'm generating the process u u~ > x0 > z l+ l- [QCD] with a shower using PYTHIA6Q decaying the z to more leptons. The output of this is a .hep file. I want to have access to the individual events so I can make histograms myself. Obviously these .hep files aren't human readable, so I figured I can convert the .hep file to a .lhe file using the executable hep2lhe included with pythia-pgs. Now, this requires a Pythia card, so I used a card from another LO process I was doing, but I changed the PDF set to be an NLO set. Here is the card:
>
>
> !...Parton showering on or off
> MSTP(61)=1
> MSTP(71)=1
>
> !...Fragmentation/hadronization on or off
> MSTJ(1)=1
>
> !...Multiple interactions on or off
> MSTP(81)=20
>
> !...Don't stop execution after 10 errors
> MSTU(21)=1
>
> !...PDFset if MG set not supported by pythia-pgs package (set in lhapdf5 or higher)
> LHAID= 244600
>
>
> LHAPATH=/home/josef/Documents/MG5_aMC_v2_2_3/pythia-pgs/src/PDFsets
>
>
> So far so good, I run hep2lhe on the .hep file using this card and I get a .lhe file. However, the .lhe file has no negative weights. According to everything I've read about this (see, for example, this question: https://answers.launchpad.net/mg5amcnlo/+question/221995) there should be some events with negative weights that I have to deal with manually. Here is a sample event from the .lhe file:
>
> <event>
> 13 100 0.10000000E+01 0.00000000E+00 0.00000000E+00 0.00000000E+00
> 2 -1 0 0 0 0 0.19197478E+01 0.14321819E+01 0.35787820E+04 0.35787828E+04 0.00000000E+00 0. 0.
> -2 -1 0 0 0 0 -0.98619084E+01 -0.75080876E+01 0.34234461E+02 0.36409161E+02 0.00000000E+00 0. 0.
> 25 2 1 1 0 0 -0.79420831E+01 -0.60758468E+01 0.36130163E+04 0.36151918E+04 0.12499991E+03 0. 0.
> 23 2 3 3 0 0 0.32682458E+01 -0.18126471E+01 0.27343541E+04 0.27358767E+04 0.91188000E+02 0. 0.
> -13 2 3 3 0 0 -0.17012360E+02 0.91103248E+01 0.50502031E+03 0.50538889E+03 0.00000000E+00 0. 0.
> 13 2 3 3 0 0 0.58020819E+01 -0.13373486E+02 0.37364167E+03 0.37392595E+03 0.00000000E+00 0. 0.
> 13 2 4 4 0 0 -0.14385665E+02 0.81555609E+01 0.25952767E+04 0.25953294E+04 0.10565800E+00 0. 0.
> -13 2 4 4 0 0 0.17653911E+02 -0.99682080E+01 0.13907740E+03 0.14054736E+03 0.10565800E+00 0. 0.
> -13 1 0 0 0 0 -0.17012360E+02 0.91103248E+01 0.50502031E+03 0.50538889E+03 0.00000000E+00 0. 0.
> 13 1 0 0 0 0 0.58020819E+01 -0.13373486E+02 0.37364167E+03 0.37392595E+03 0.00000000E+00 0. 0.
> 13 1 0 0 0 0 -0.14385665E+02 0.81555609E+01 0.25952767E+04 0.25953294E+04 0.10565800E+00 0. 0.
> -13 1 0 0 0 0 0.17653911E+02 -0.99682080E+01 0.13907740E+03 0.14054736E+03 0.10565800E+00 0. 0.
> 21 1 0 0 0 0 0.90701808E+01 0.64176680E+01 0.58962114E+02 0.60107776E+02 0.35998779E+01 0. 0.
> </event>
>
> The events seem to make sense; I have some up quarks going to a Higgs and a Z, which then go to some leptons and gluons. The weight is exactly 1 though, and every other event also has weight 1. I'm just wondering whether or not what I did is valid and whether or not this makes sense.
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Hi Olivier,

Thanks for the response. I was was just wondering if you know how to actually do that conversion? It seems like in the past, there was a program called convertStdHep which does the required conversion, but I can't find it. I'm mainly looking at question (https://bugs.launchpad.net/pythia-pgs-for-mg/+bug/1334366) but the file they're discussing (http://cepa.fnal.gov/psm/stdhep/dist/convertStdHep-0.02.00.tar.gz) doesn't seems to exist anymore.

no idea.

one solution is to use madanalysis5 which can read those file

cheers,

olivier
On 13 Oct 2015, at 23:42, Josef Stanton <email address hidden> wrote:

> Question #272345 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/272345
>
> Status: Answered => Open
>
> Josef Stanton is still having a problem:
> Hi Olivier,
>
> Thanks for the response. I was was just wondering if you know how to
> actually do that conversion? It seems like in the past, there was a
> program called convertStdHep which does the required conversion, but I
> can't find it. I'm mainly looking at question
> (https://bugs.launchpad.net/pythia-pgs-for-mg/+bug/1334366) but the file
> they're discussing
> (http://cepa.fnal.gov/psm/stdhep/dist/convertStdHep-0.02.00.tar.gz)
> doesn't seems to exist anymore.
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.