# Events in interference processes

Asked by daniel camargo on 2018-07-30

Hey guys,

I´m generating p p > l- l+ QED=2 where there is an extra Z´ (I want to see interference effects...). I expect the invariant mass mll contain 2 approximate resonances at the Z and Z´ masses, but it just generate the one of Z, and no events left for Z´. What I am missing here in order to see both resonances?

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Olivier Mattelaer
Solved:
2018-08-01
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2018-08-01
2018-07-31
 Olivier Mattelaer (olivier-mattelaer) said on 2018-07-31: #1

Hi,

> What I am missing here in order to see both resonances?

Well to give us the full information about what you try such that we can do something more than just speculate.
So here is wild guess
1) what is the mass of the Z'
2) what is the cross-section for the Z (alone)
3) what is the cross-section for the Z' (alone)
4) what is the cross-section for the sum of the two (with interference)

Cheers,

Olivier

> On 30 Jul 2018, at 22:07, daniel camargo <email address hidden> wrote:
>
> New question #671236 on MadGraph5_aMC@NLO:
>
> Hey guys,
>
> I´m generating p p > l- l+ QED=2 where there is an extra Z´ (I want to see interference effects...). I expect the invariant mass mll contain 2 approximate resonances at the Z and Z´ masses, but it just generate the one of Z, and no events left for Z´. What I am missing here in order to see both resonances?
>
>
> --

 daniel camargo (dacamargov) said on 2018-07-31: #2

hey Oliver,

1) what is the mass of the Z'
> ~TeV scale (1-3 TeV).

2) what is the cross-section for the Z (alone)
> 1201 (pb)

3) what is the cross-section for the Z' (alone)
>for mz´ = 1 TeV, sigma = 0.008833 (pb)

4) what is the cross-section for the sum of the two (with interference)
>for mz´ = 1 TeV , sigma=1660 (pb)

Thanks

 Olivier Mattelaer (olivier-mattelaer) said on 2018-07-31: #3

Ok so how many events did you generate? You will need a huge amount of event in order to see a z prime due to the ratio of cross section

Cheers

Olivier

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________________________________
Sent: Tuesday, July 31, 2018 6:22:28 PM
To: Olivier Mattelaer
Subject: Re: [Question #671236]: Events in interference processes

daniel camargo posted a new comment:
hey Oliver,

1) what is the mass of the Z'
> ~TeV scale (1-3 TeV).

2) what is the cross-section for the Z (alone)
> 1201 (pb)

3) what is the cross-section for the Z' (alone)
>for mz´ = 1 TeV, sigma = 0.008833 (pb)

4) what is the cross-section for the sum of the two (with interference)
>for mz´ = 1 TeV , sigma=1660 (pb)

Thanks

--

 daniel camargo (dacamargov) said on 2018-07-31: #4

100k events, I guess more than that is not recommendable per-run right?

Cheers,

 Olivier Mattelaer (olivier-mattelaer) said on 2018-07-31: #5

Ok in a sample of 100k events, you expect in average ~ 1 events to be from the Z prime peak.
So if you do not see any of those, this should not be a problem in itself. Now if you do not see any of those in 25 different samples, then this is a sign of a bug.

This being said, you can actually generate larger sample without any problem.

Cheers,

Olivier

 daniel camargo (dacamargov) said on 2018-08-01: #6

Thanks Olivier Mattelaer, that solved my question.