# transverse mass in Madanalysis

Dear MadAnalysis team:

I generated a process p p > w+ w- by Madgraph. And then I used MadAnalysis to produce MT(w+ w-). Why does the diagram show that all MT(w+ w-) are zero?

If I use this definition:

MT_{w+ w-}^2 = (ET_{w+} + ET{w-})^2 - (PT_{w+}+PT_{w-})^2

, where ET_{w+} = Sqrt(m^

In my situation, PT_(w+) + PT_(w-) = 0. MT_{w+ w-}^2 should be (ET_{w+} + ET{w-})^2 and it is must greater than zero. This result disagree with MadAnalysis' result.

So, how does MadAnalysis deal with the MT? Am I misunderstand the definition about MT(w+ w-)

Best Regrads

Guojin Tseng

## Question information

- Language:
- English Edit question

- Status:
- Answered

- Assignee:
- No assignee Edit question

- Last query:
- 2019-07-18

- Last reply:
- 2019-07-18

Benjamin Fuks (fuks) said : | #1 |

Hi,

In your syntax, you ask madanalysis 5 to first sum the four momenta of the two w-bosons (so that the summed vector has only a non-vanishing energy and pz componet), and then compute the transverse mass of the resulting four-vector. In this case, the transverse mass equals the transverse energy (since the combined pt vanishes). There are several definitions of the transverse energy and the one we use is

Et = E pt^2/(pt^2+pz^2)

i.e. this corresponds to the fraction of the energy in the transverse direction which is thus 0.

Regards,

Benjamin

> On 18 Jul 2019, at 05:02 , GuojinTseng <email address hidden> wrote:

>

> New question #682128 on MadAnalysis 5:

> https:/

>

> Dear MadAnalysis team:

>

> I generated a process p p > w+ w- by Madgraph. And then I used MadAnalysis to produce MT(w+ w-). Why does the diagram show that all MT(w+ w-) are zero?

>

> If I use this definition:

> MT_{w+ w-}^2 = (ET_{w+} + ET{w-})^2 - (PT_{w+}+PT_{w-})^2

> , where ET_{w+} = Sqrt(m^

>

> In my situation, PT_(w+) + PT_(w-) = 0. MT_{w+ w-}^2 should be (ET_{w+} + ET{w-})^2 and it is must greater than zero. This result disagree with MadAnalysis' result.

>

> So, how does MadAnalysis deal with the MT? Am I misunderstand the definition about MT(w+ w-)

>

> Best Regrads

>

> Guojin Tseng

>

> --

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> contact for MadAnalysis 5.

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