Number of event in delphes root files after matching

Asked by Daniele Barducci on 2013-12-19

Hi,
I am generating 10k events for the following process
generate p p > e- ve~ @1
add process p p > e- ve~ j @2
with matching procedure performed with pythia and going also at delphes level.

After pythia I correctly have a certain number of rejected events (9780 remaining events after matching).
However in the root file generate by delphes I still have 10k events and if I try to make plots from the root file these looks slightly different from the one provided by MadGraph. Why delphes doesn't have the 9780 events but the initial 10k?

Moreover under the plots at Delphes level provided by MG there is written the parton level cross section instead that the matched cross section, and I can't understand why.

Thanks in advance for the help,

Daniele

Question information

Language:
English Edit question
Status:
Solved
For:
MadGraph5_aMC@NLO Edit question
Assignee:
No assignee Edit question
Solved by:
Daniele Barducci
Solved:
2014-01-21
Last query:
2014-01-21
Last reply:
2013-12-19

Hi Daniele,

I forward you bug to Delphes author:
https://cp3.irmp.ucl.ac.be/projects/delphes/ticket/241

Cheers,

Olivier

Daniele Barducci (db3e11) said : #2

Thanks

Pavel Demin (pavel-demin) said : #3

Hi Daniele,

Could you, please provide a link to a file that shows this problem and that you are using as input fro Delphes?

Thanks,

Pavel

Daniele Barducci (db3e11) said : #4

Hi Pavel,
I have e-mailed you a tar ball with the files since I didn't manage to attach it here

Best

Daniele

Pavel Demin (pavel-demin) said : #5

Hi Daniele,

I did not receive the tar file. If it's too big may be it was rejected by my web server.

I did not realize that you were running Delphes 2.

In case of Delphes2, it inserts empty events in place of the events rejected by Pythia.

If it's so, your root files should contain exactly 10000-9780=220 events with 0 particles.

Anyway, Delphes 2 is not supported and I suggest you to switch to Delphes 3.

Regards,

Pavel

Daniele Barducci (db3e11) said : #6

Dear Pavel,
Yes, maybe it was rejected but no problem, I have analyzed again the file and founded exactly the number of events with no particles inside as you suggested.
Ok, I will switch to Delphes3; just as an info, also Delphes3 add empty events or it was just Delphes2?
Thanks for your help, this solve the problem!

Pavel Demin (pavel-demin) said : #7

Dear Daniele,

Delphes3 does not add empty events.

The empty events are useful when you need to compare the events at the Matrix Element level with the events at the Detector level.

But apparently, this feature created more confusion than we expected. So, we removed it from Delphes 3.

Regards,

Pavel

Daniele Barducci (db3e11) said : #8

Thanks!