Propagating Weight ID's from LHEF to HepMC
Dear MG developers,
I have a question about weight ID's in HepMC files.
First, the setup and what happens.
When reweighting and naming various parameter points it would be great to have these names/ids written in the HepMC file.
For example, let's say I have an event in an LHEF file (along with the header):
<initrwgt>
<weightgroup name='mg_
<weight id='point1'>set param_card mass 34 1000.0 # orig: 3000.0
set param_card ssmcoup 1 0.9 # orig: 1.0
</weight>
<weight id='point2'>set param_card mass 34 2000.0 # orig: 3000.0
set param_card ssmcoup 1 0.5 # orig: 1.0
</weight>
</weightgroup>
</initrwgt>
<MGGenerationInfo>
# Number of Events : 5
# Integrated weight (pb) : 0.010046
</MGGenerationInfo>
</header>
<init>
2212 2212 6.500000e+03 6.500000e+03 0 0 230000 230000 -4 1
1.004600e-02 1.268800e-04 1.016000e-02 0
<generator name='MadGraph5
</init>
<event>
5 0 +1.0160000e-02 2.99912800e+03 7.81616400e-03 8.00755700e-02
-2 -1 0 0 0 501 -0.0000000000e+00 +0.0000000000e+00 +9.8323714599e+02 9.8323714599e+02 0.0000000000e+00 0.0000e+00 1.0000e+00
1 -1 0 0 501 0 +0.0000000000e+00 -0.0000000000e+00 -2.2870299871e+03 2.2870299871e+03 0.0000000000e+00 0.0000e+00 -1.0000e+00
-34 2 1 2 0 0 +0.0000000000e+00 +0.0000000000e+00 -1.3037928411e+03 3.2702671331e+03 2.9991284316e+03 0.0000e+00 0.0000e+00
13 1 3 3 0 0 -4.3939456193e+02 +3.0684611657e+02 -2.1790372204e+03 2.2439753404e+03 0.0000000000e+00 0.0000e+00 -1.0000e+00
-14 1 3 3 0 0 +4.3939456193e+02 -3.0684611657e+02 +8.7524437929e+02 1.0262917927e+03 0.0000000000e+00 0.0000e+00 1.0000e+00
<rwgt>
<wgt id='point1'> +9.6275264e-06 </wgt>
<wgt id='point2'> +2.3461820e-06 </wgt>
</rwgt>
</event>
If I shower this event with Pythia8 and use the default pythia8_card.dat, the HepMC file starts like this:
HepMC::Version 2.06.09
HepMC::
E 0 -1 -1.000000000000
N 3 "1000.0_
SET_PARAM_
SET_PARAM_
U GEV MM
C 2.0034000000000
The important lines are these:
N 3 "1000.0_
SET_PARAM_
SET_PARAM_
In these lines the weight "names" are encoded and it is rather difficult to decode them back into human-readable form.
After some hacking of MG5aMC_
HepMC::Version 2.06.09
HepMC::
E 0 -1 -1.000000000000
N 3 "Weight_
U GEV MM
Again, the important line is
N 3 "Weight_
which now contains easily readable weight ids in a single line.
So, finally, my question is whether there is an "official" way to do this without hacking the MG5aMC_
Also, is there some deeper reason for the current weight naming in HepMC files?
Thanks,
Simonas
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