Delphes not recognized by MG5_aMC_v2_6_2

[Dikai Li]

Hi there,

>>>>Case1.
I install Delphes as
MG5_aMC> install Delphes

and also manually modify the input/mg5_configuration.txt as
delphes_path = ./Delphes
(actually, no matter uncomment or not this line, it won't change the following result.)

Then after I issue the following steps,
MG5_aMC>import sm-no_b_mass
MG5_aMC>define wpm = w+ w-
MG5_aMC>generate p p > z wpm
MG5_aMC>output 2ssl2j_bkg_zwpm
MG5_aMC>launch 2ssl2j_bkg_zwpm

it gives options like this:

The following switches determine which programs are run:
/=================== Description ===================|============= values ==============|======== other options ========\
| 1. Choose the shower/hadronization program | shower = Not Avail. | Please install module |
| 2. Choose the detector simulation program | detector = Not Avail. | Please install module |
| 3. Choose an analysis package (plot/convert) | analysis = Not Avail. | Please install module |
| 4. Decay onshell particles | madspin = OFF | ON|onshell |
| 5. Add weights to events for new hypp. | reweight = Not Avail. | Please install module |
\=======================================================================================================================/

which means it doesn't recognize the Delphes for detector simulation program.

>>>>Case2.
Then, one possible guess is whether is due to no proper shower program is installed. But the answer is I could have used pythia6(which is included in MG5_aMC_v2_6_2) for shower. i.e. at the very beginning when I

tar -zxf MG5_aMC_v2.6.2.tar.gz
cd MG5_aMC_v2_6_2/
./bin/mg5_aMC
MG5_aMC>import model sm-no_b_mass
MG5_aMC>define wpm = w+ w-
MG5_aMC>generate p p > z wpm [QCD]
MG5_aMC>output 2ssl2j_bkg_zwpm_QCD
(this step will automatically install necessary packages, like cuttools, iregi, ninja)

MG5_aMC>launch 2ssl2j_bkg_zwpm_QCD

then, it gives reasonable options, like

The following switches determine which programs are run:
/=============================================================================\
1. Type of perturbative computation order = NLO
2. No MC@[N]LO matching / event generation fixed_order = OFF
3. Shower the generated events shower = HERWIG6
4. Decay onshell particles madspin = OFF
5. Add weights to events for new hypp. reweight = Not Avail.
6. Run MadAnalysis5 on the events generated madanalysis = Not Avail.
\=============================================================================/

and I can also change the shower option to pythia6, i.e.

The following switches determine which programs are run:
/=============================================================================\
1. Type of perturbative computation order = NLO
2. No MC@[N]LO matching / event generation fixed_order = OFF
3. Shower the generated events shower = PYTHIA6Q
4. Decay onshell particles madspin = OFF
5. Add weights to events for new hypp. reweight = Not Avail.
6. Run MadAnalysis5 on the events generated madanalysis = Not Avail.
\=============================================================================/

So, in case2, I don't need to install any package(like pythia6 and/or Delphes) manually, then MG5_aMC_v2_6_2 could recognize PYTHIA6Q for shower properly.

In case1, even after I install Delphes manually, MG5_aMC_v2_6_2 could not recognize PYTHIA6Q for shower or Delphes for detector.

>>>>Case3.
Story goes on. my next guess is whether this is due to any interface and/or other parameters settings problem. So I try to install pythia-pgs, then guess what, such install fix the shower/detector options problem. i.e.

MG5_aMC>install pythia-pgs
MG5_aMC>launch 2ssl2j_bkg_zwpm
The following switches determine which programs are run:
/=================== Description ===================|============= values ==============|======== other options ========\
| 1. Choose the shower/hadronization program | shower = OFF | Pythia6 |
| 2. Choose the detector simulation program | detector = OFF | PGS|Delphes |
| 3. Choose an analysis package (plot/convert) | analysis = Not Avail. | Please install module |
| 4. Decay onshell particles | madspin = OFF | ON|onshell |
| 5. Add weights to events for new hypp. | reweight = Not Avail. | Please install module |
\=======================================================================================================================/

Please notice that in case3, only the package pythia-pgs is installed, without touching anything related to Delphses and/or PYTHIA6Q, but it fix the problem with providing options to previously installed Delphes.

So, my argument is if anyone don't need/want to install pythia-pgs, but just want to work with the PYTHIA6Q(already exist in MG5_aMC_v2_6_2) and Delphes(manually installed), the current settings in MG5_aMC_v2_6_2 codes don't fulfill such approach.

Although I can work without problem now, however I think it's still a bug, and could be fixed to improve the user friend.

Cheers,
Dikai

[Olivier Mattelaer (olivier-mattelaer)]

Hi,

Thanks for the suggestion.

Actually Pythia6 (and Herwig6) are completely outdated and not supported anymore by their author.
pythia-pgs package shoud be consider at the same level.

Consequently
1) the only shower really interface at LO is for the moment pythia8.
2) Even if the NLO part of the code ship (for historical reason) PY6 and HW6. I do not plan to create a way to use them within the LO part of the code.

To make it more user friendy, I have added the following warning in your case 1 situation:

Delphes program installed but no parton shower module detected.
    Please install pythia8

Also when installing Delphes, the following warning will be raised if neither pythia-pgs or pythia8 is present:

We noticed that no parton-shower module are installed/linked.
In order to use Delphes from MG5aMC please install/link pythia8.

Cheers,

Olivier