# Making an invariant mass cut

Hi Madgraph Team,

How do I make an invariant mass cut (of say 2GeV) in MG5 for a simple drell-yan process such as p p > mm+ mm-? mm is a custom defined particle with custom couplings to the photon and Z boson.

I notice the options in the run card as follows:

#******

# Minimum and maximum invariant mass for pairs *

# WARNING: for four lepton final state mmll cut require to have *

# different lepton masses for each flavor! *

#******

0.0 = mmjj ! min invariant mass of a jet pair

0.0 = mmbb ! min invariant mass of a b pair

0.0 = mmaa ! min invariant mass of gamma gamma pair

0.0 = mmll ! min invariant mass of l+l- (same flavour) lepton pair

-1.0 = mmjjmax ! max invariant mass of a jet pair

-1.0 = mmbbmax ! max invariant mass of a b pair

-1.0 = mmaamax ! max invariant mass of gamma gamma pair

-1.0 = mmllmax ! max invariant mass of l+l- (same flavour) lepton pair

{} = mxx_min_pdg ! min invariant mass of a pair of particles X/X~ (e.g. {6:250})

{'default': False} = mxx_only_

#******

# Minimum and maximum invariant mass for all letpons *

#******

0.0 = mmnl ! min invariant mass for all letpons (l+- and vl)

-1.0 = mmnlmax ! max invariant mass for all letpons (l+- and vl)

#******

Which of these would I have to edit to produce the desired invariant mass cut?

Many thanks,

Ameir

## Question information

- Language:
- English Edit question

- Status:
- Solved

- Assignee:
- No assignee Edit question

- Solved by:
- Olivier Mattelaer

- Solved:
- 2018-01-23

- Last query:
- 2018-01-23

- Last reply:
- 2018-01-21

Hi,

One think that you need to be careful about is the implicit cut associate to the factorisation scale.

If that scale is below 4GeV^2 you have an automatic cut of the phase-space point.

Then concerning your question, the use of mxx_min_pdg is the appropriate cut in your case.

What is the PDG code of your particle? Assuming that it is 123456

then you should put

{123456: 2} = mxx_min_pdg

For your process, the value of mxx_only_

Cheers,

Olivier

> On 21 Jan 2018, at 13:17, Ameir Shaa <email address hidden> wrote:

>

> New question #663363 on MadGraph5_aMC@NLO:

> https:/

>

> Hi Madgraph Team,

>

> How do I make an invariant mass cut (of say 2GeV) in MG5 for a simple drell-yan process such as p p > mm+ mm-? mm is a custom defined particle with custom couplings to the photon and Z boson.

>

> I notice the options in the run card as follows:

>

> #******

> # Minimum and maximum invariant mass for pairs *

> # WARNING: for four lepton final state mmll cut require to have *

> # different lepton masses for each flavor! *

> #******

> 0.0 = mmjj ! min invariant mass of a jet pair

> 0.0 = mmbb ! min invariant mass of a b pair

> 0.0 = mmaa ! min invariant mass of gamma gamma pair

> 0.0 = mmll ! min invariant mass of l+l- (same flavour) lepton pair

> -1.0 = mmjjmax ! max invariant mass of a jet pair

> -1.0 = mmbbmax ! max invariant mass of a b pair

> -1.0 = mmaamax ! max invariant mass of gamma gamma pair

> -1.0 = mmllmax ! max invariant mass of l+l- (same flavour) lepton pair

> {} = mxx_min_pdg ! min invariant mass of a pair of particles X/X~ (e.g. {6:250})

> {'default': False} = mxx_only_

> ! to pairs of particle/

> #******

> # Minimum and maximum invariant mass for all letpons *

> #******

> 0.0 = mmnl ! min invariant mass for all letpons (l+- and vl)

> -1.0 = mmnlmax ! max invariant mass for all letpons (l+- and vl)

> #******

>

> Which of these would I have to edit to produce the desired invariant mass cut?

>

>

> Many thanks,

>

> Ameir

>

> --

> You received this question notification because you are an answer

> contact for MadGraph5_aMC@NLO.

Ameir Shaa (ameirshaa) said : | #2 |

Hi Olivier,

Many thanks for your answer.

I just need a clarification. Why do you say that the value of mxx_only_

Many thanks,

Ameir

Your have a particle-

so setting mxx_only_

This switch is more for case where you have two particle and two anti-particle. If you put it on True then you do not constaint the invariant mass between the two particle (same between the two anti-particle).

But you do so if you put it on False.

To be complete, this entry is a dictionary so you have the choice to put it on True/False for each pdg independently.

Cheers,

Olivier

> On 21 Jan 2018, at 18:22, Ameir Shaa <email address hidden> wrote:

>

> Question #663363 on MadGraph5_aMC@NLO changed:

> https:/

>

> Status: Answered => Open

>

> Ameir Shaa is still having a problem:

> Hi Olivier,

>

> Many thanks for your answer.

>

> I just need a clarification. Why do you say that the value of

> mxx_only_

>

> Many thanks,

>

> Ameir

>

> --

> You received this question notification because you are an answer

> contact for MadGraph5_aMC@NLO.

Ameir Shaa (ameirshaa) said : | #4 |

Thanks Olivier Mattelaer, that solved my question.