cut on invariant mass of e+ e- is not working as predicted

Asked by Prudhvi Nikhil Bhattiprolu on 2018-05-24

Dear MadAnalysis 5 team,

I am trying to do a cut on the invariant mass of e+ (mu+) and e- (mu-) where I do "select 71.2 < M(e+ e-) < 111.2 or 71.2 < M(mu+ mu-) < 111.2 " on an lhco file (which has only one event, for debugging purposes). I calculated the invariant masses (using Mathematica) of e+ e- pairs in the event based on the information in .lhco file and found that one of the pairs give an invariant mass of 70.3185 GeV, which I also read off of the M(e+ e-) plot (in mad analysis report). For this particular pair, I expect it not to satisfy the condition "71.2 < M(e+ e-) < 111.2. But, for some reason, mad analysis does not reject this pair. Could this possibly be a bug?

I am attaching the following files

1.) the lhco file
2.) mad analysis html report (.pdf)
3.) event info file (.text) which lists all the objects along with their four momenta and other details (calculated from .lhco file) &
4.) event_invariant masses.pdf file which shows my calculations of invariant masses (using Mathematica) )

https://www.dropbox.com/sh/43mzbo8wc1otrcu/AAAWdZPfk184q1OtPs5-jH5Ua?dl=0

It would be great if more light can be thrown on this. Please let me know, if anything is required to be done from my side.

Thank you very much! Your help will be much appreciated!

Sincerely,
Prudhvi Bhattiprolu

Question information

Language:
English Edit question
Status:
Solved
For:
MadAnalysis 5 Edit question
Assignee:
No assignee Edit question
Solved by:
Benjamin Fuks
Solved:
2018-05-24
Last query:
2018-05-24
Last reply:
2018-05-24
Benjamin Fuks (fuks) said : #2

Hi Prudhvi,

This is not a bug but a feature of how joint cut conditions are treated in ma5. When you typed this:
  select 71.2 < M(e+ e-) < 111.2
you acually asked for selected event to contain:
 - at least one e+ e- pair with M > 71 GeV
 - at least one e+e- pair with M < 111 GeV
In the provided event, you have two possible pairs, one with an invariant mass of 70 GeV (satisfying thus the second condition) and one with a mass of 515 GeV (satisfying thus the first condtion). Both conditions are hence realized and the event passes the cut.

Regards,

Benjamin

> On 24 May 2018, at 05:32 , Prudhvi Nikhil Bhattiprolu <email address hidden> wrote:
>
> Question #669574 on MadAnalysis 5 changed:
> https://answers.launchpad.net/madanalysis5/+question/669574
>
> Description changed to:
> Dear MadAnalysis 5 team,
>
> I am trying to do a cut on the invariant mass of e+ (mu+) and e- (mu-)
> where I do "select 71.2 < M(e+ e-) < 111.2 or 71.2 < M(mu+ mu-) < 111.2
> " on an lhco file (which has only one event, for debugging purposes). I
> calculated the invariant masses (using Mathematica) of e+ e- pairs in
> the event based on the information in .lhco file and found that one of
> the pairs give an invariant mass of 70.3185 GeV, which I also read off
> of the M(e+ e-) plot (in mad analysis report). For this particular pair,
> I expect it not to satisfy the condition "71.2 < M(e+ e-) < 111.2. But,
> for some reason, mad analysis does not reject this pair. Could this
> possibly be a bug?
>
> I am attaching the following files
>
> 1.) the lhco file
> 2.) mad analysis html report (.pdf)
> 3.) event info file (.text) which lists all the objects along with their four momenta and other details (calculated from .lhco file) &
> 4.) event_invariant masses.pdf file which shows my calculations of invariant masses (using Mathematica) )
>
> https://www.dropbox.com/sh/43mzbo8wc1otrcu/AAAWdZPfk184q1OtPs5-jH5Ua?dl=0 <https://www.dropbox.com/sh/43mzbo8wc1otrcu/AAAWdZPfk184q1OtPs5-jH5Ua?dl=0>
>
> It would be great if more light can be thrown on this. Please let me
> know, if anything is required to be done from my side.
>
> Thank you very much! Your help will be much appreciated!
>
> Sincerely,
> Prudhvi Bhattiprolu
>
> --
> You received this question notification because you are an answer
> contact for MadAnalysis 5.

Hello Benjamin,

Thank you very much for clarifying. I am wondering if there is any way to select the invariant mass of e+ e-(of atleast one pair) to be strictly in between 71.2 and 111.2 ?

Best Regards,

Prudhvi

Best Benjamin Fuks (fuks) said : #4

Hi,

You can enforce the code to use the leading and next-to-leading leptons, like casting M(e+[1] e-[1]). Otherwise, the expert mode must be used.

Regards,

Benjamin

> On 24 May 2018, at 17:07 , Prudhvi Nikhil Bhattiprolu <email address hidden> wrote:
>
> Question #669574 on MadAnalysis 5 changed:
> https://answers.launchpad.net/madanalysis5/+question/669574
>
> Status: Answered => Open
>
> Prudhvi Nikhil Bhattiprolu is still having a problem:
> Hello Benjamin,
>
> Thank you very much for clarifying. I am wondering if there is any way
> to select the invariant mass of e+ e-(of atleast one pair) to be
> strictly in between 71.2 and 111.2 ?
>
> Best Regards,
>
> Prudhvi
>
> --
> You received this question notification because you are an answer
> contact for MadAnalysis 5.
>

Thanks Benjamin Fuks, that solved my question.