a question about the particle branch in Delphes3.0.6

[liuda]

Hi,

I am confused about the particle branch in Delphes3 root output. When I want to select the generated b

partons(from the ttbar+events where top is decayed in pythia), I get more b partons than expected in some
events? My selection condition is "particle->Status ==2&&abs(particle->PID)==5", but there is an event like this:

mass Charge E pT Eta
4.68 0 90.8796 65.6091 -0.84969
4.68 0 90.8796 65.6091 -0.84969
4.68 0 45.0283 21.6554 1.35506
number of bparton: 3
How to understand this, or do I miss something?
Actually, I want to use these information for b-jet tagging. In Delphes3, is the value of DeltaR in the module BTagging controlling the distance between the jet and b-parton to decide if it is a b-jet? If so, what is
the suggested value for anti-kt with R=0.4 ?

Thank you very much.

Best regards,

Da Liu

[Michele Selvaggi]

Hi,

I get more b partons than expected in some
events? My selection condition is "particle->Status ==2&&abs(particle->PID)==5"

your selection looks fine. In general I guess it is expected to have more b's than what you expect from the hard scattering, since you may extra b's originating from radiation.

mass Charge E pT Eta
4.68 0 90.8796 65.6091 -0.84969
4.68 0 90.8796 65.6091 -0.84969
4.68 0 45.0283 21.6554 1.35506
number of bparton: 3
How to understand this, or do I miss something?

for this I wouldn't know exactly what's going on. It seems Pythia for reason is rewriting the b in the list for some reason.
Anyway this does not have any impact for the b-tagging. If the b parton is matched with a jet, that jet will be tagged as b. You will not have any double counting of b-jets.

In Delphes3, is the value of DeltaR in the module BTagging controlling the distance between the jet and b-parton to decide if it is a b-jet?

yes.

If so, what is the suggested value for anti-kt with R=0.4 ?

According to our experience the matching efficiency is pretty stable as a function of size cone used for the matching. Nevertheless, I would typically chose a value close to the jet cone radius.

Michele

Replying to liuda:

Hi,

I am confused about the particle branch in Delphes3 root output. When I want to select the generated b

partons(from the ttbar+events where top is decayed in pythia), I get more b partons than expected in some
events? My selection condition is "particle->Status ==2&&abs(particle->PID)==5", but there is an event like this:

mass Charge E pT Eta
4.68 0 90.8796 65.6091 -0.84969
4.68 0 90.8796 65.6091 -0.84969
4.68 0 45.0283 21.6554 1.35506
number of bparton: 3
How to understand this, or do I miss something?
Actually, I want to use these information for b-jet tagging. In Delphes3, is the value of DeltaR in the module BTagging controlling the distance between the jet and b-parton to decide if it is a b-jet? If so, what is
the suggested value for anti-kt with R=0.4 ?

Thank you very much.

Best regards,

Da Liu

[liuda]

Hi,

Thank you very much for your help.

Best regards,
Da Liu

Replying to mselvaggi:

Hi,

I get more b partons than expected in some
events? My selection condition is "particle->Status ==2&&abs(particle->PID)==5"

your selection looks fine. In general I guess it is expected to have more b's than what you expect from the hard scattering, since you may extra b's originating from radiation.

mass Charge E pT Eta
4.68 0 90.8796 65.6091 -0.84969
4.68 0 90.8796 65.6091 -0.84969
4.68 0 45.0283 21.6554 1.35506
number of bparton: 3
How to understand this, or do I miss something?

for this I wouldn't know exactly what's going on. It seems Pythia for reason is rewriting the b in the list for some reason.
Anyway this does not have any impact for the b-tagging. If the b parton is matched with a jet, that jet will be tagged as b. You will not have any double counting of b-jets.

In Delphes3, is the value of DeltaR in the module BTagging controlling the distance between the jet and b-parton to decide if it is a b-jet?

yes.

If so, what is the suggested value for anti-kt with R=0.4 ?

According to our experience the matching efficiency is pretty stable as a function of size cone used for the matching. Nevertheless, I would typically chose a value close to the jet cone radius.

Michele

Replying to liuda:

Hi,

I am confused about the particle branch in Delphes3 root output. When I want to select the generated b

partons(from the ttbar+events where top is decayed in pythia), I get more b partons than expected in some
events? My selection condition is "particle->Status ==2&&abs(particle->PID)==5", but there is an event like this:

mass Charge E pT Eta
4.68 0 90.8796 65.6091 -0.84969
4.68 0 90.8796 65.6091 -0.84969
4.68 0 45.0283 21.6554 1.35506
number of bparton: 3
How to understand this, or do I miss something?
Actually, I want to use these information for b-jet tagging. In Delphes3, is the value of DeltaR in the module BTagging controlling the distance between the jet and b-parton to decide if it is a b-jet? If so, what is
the suggested value for anti-kt with R=0.4 ?

Thank you very much.

Best regards,

Da Liu