missing electrons in 4 electrons finale state signal

[emran ali]

hi delphes team
i used calchep to produce 4 electrons finale stat signal "2 e- and 2e+" , i linked it with pythia stand alone .. when i run delphes ,i found that, only 2 electrons found in delphes tree !!!!!!!!!!
Also i tried to run the .lhe file from calchep directly to delphes " with out pythia "
i gives me the same result .
Best
emran

[Pavel Demin]

Dear Emran,

Is it possible, that some of the electrons have transverse momenta less than 10 GeV? By default, Delphes rejects electrons with pT < 10 GeV.

It would be also very helpful if you could provide a small (~10 events) sub-sample of your events.

Regards,

Pavel

[emran ali]

hi Pavel
i have attached the hepmc file but is there any way to fix this ????
Best
emran

[Pavel Demin]

Hi Emran,

Thanks for the hepmc file.

Looks like the electrons are rejected by the isolation criteria.

I've looked at some of the events using event display and found that there are always 2 electrons/positrons that are very close to each other.

Here are the electrons/positrons from the first event:

P 607 11 -1.5058580625894925e+04 6.9246571676718202e+04 -6.1031001918057031e+04 9.3523428801775110e+04 5.1099999999999990e-01 1 0 0 0 0

P 609 11 3.1333631066264282e+05 -9.4029348818282233e+04 -1.1425374063108706e+04 3.2734034458232252e+05 5.1099999999999990e-01 1 0 0 0 0

P 610 -11 -2.9696830790558219e+04 1.2253455884022835e+04 -3.3211970467438905e+03 3.2296738073506680e+04 5.1099999999999990e-01 1 0 0 0 0

P 612 -11 9.9769099634468905e+04 -5.0120315795352661e+04 1.6751886865299657e+04 1.1290059792169066e+05 5.1099999999999990e-01 23 0 0 -465 0

and here is an event display for this event with electrons/positrons tracks in red:

[Michele Selvaggi]

Hi Emran,

you could try to relax the isolation criteria in your card, and see how the average number of electrons increases.
For instance, you could increase the value of the parameter PTRatioMax for the electron isolation:

module Isolation ElectronIsolation {
...
set PTRatioMax 0.5

If you set PTRatioMax to a very high value (say 1000), all your electrons should pass.

I would however suggest you go and check how CMS/ATLAS perform this type of analysis with very boosted collimated electrons and which kind of isolation criteria they use.

Cheers,

Michele

[emran ali]

Hi dr Michele
i set PTRatioMax = 1000 , but still three electrons finale state could pass.
what if i reduce th deltaR to be say 0.1 ????
Cheers
emran

[Michele Selvaggi]

Hi Emran,

setting deltaR->0 or PTRatioMax->inf should give you the same result. It is possible you lose some of your electrons because of finite detector acceptance/efficiency.
What do you believe this is a problem? You will always have some events with less than four electrons.

Michele

[emran ali]

Thanks Dr Michele & Dr Pavel
i did what you mentioned above but still not all electrons pass . Also i made DY process from SM
,it gives the same error , while the outgoing 2 electrons shouldnt be collimated or close together.
i attached file with DY process with 10 events " there is only 13 electrons in electron branch" !!!
thanks alot for your interset
Emran

[Michele Selvaggi]

Hi Emran,

by "all your electrons should pass", I meant, "all electrons that pass the other selection criteria (geometrical acceptance, efficiency ..) should pass". It is perfectly normal that some electrons do not pass these criteria.

Michele

[ahmed hammad]

Hi Dr Michele
iam srry for my leak information , iam just a new user.
i understood what you mentioned above , and , ican calculate the acceptance of the detector by comparing eta of the gen level to that from delphes .
by means of 4 electrons + missing ET , it was the decay of Zp .
i tried Zp->2e , it works good and the plot of Zp mass achieved at exactly at MZp=1500. but , i wonder when i try to examine Zp->4e+missing Et , it gives me wrong results .
i tried to reconstruct MZp as M=sqrt(2*energy(4e)*energy(missing ET)*(1-cos(phi"4e"-phi"Et"))).
Finally i want to thank you for your help .
Emran