# complex mass scheme

Hi

If I use

mg5> set complex_mass True

then

Q1:the introduction of the width of W and Z is: A.complex mass scheme; B.fixed width scheme.

Q2:the introduction of the width of top is: A.complex mass scheme; B.fixed width scheme

if I don't use

mg5> set complex_mass True

then

Q3:the introduction of the width of W and Z is: A.complex mass scheme; B.fixed width scheme.

Q4:the introduction of the width of top is: A.complex mass scheme; B.fixed width scheme.

I think the answer for Q1 is A and the answer for Q3 is B. but i am not sure the answer for Q2 Q4.

Q5: if i want fixed width scheme for WZ and complex mass scheme for top. what should i do.

Best regards

Huanyu

## Question information

- Language:
- English Edit question

- Status:
- Solved

- Assignee:
- No assignee Edit question

- Solved by:
- Olivier Mattelaer

- Solved:
- 2020-10-19

- Last query:
- 2020-10-19

- Last reply:
- 2020-10-16

If you use the complex mass-scheme.

This applies to ALL masses.

So answer to

Q1 is A

Q2 is A

Q3 is B

Q4 is B

For Q5, we do not support such mix mode.

One solution is to create your own UFO model where all propagator (and the rest) are within that scheme.

Cheers,

Olivier

> On 16 Oct 2020, at 21:20, HuanyuBi <email address hidden> wrote:

>

> New question #693492 on MadGraph5_aMC@NLO:

> https:/

>

> Hi

>

> If I use

> mg5> set complex_mass True

> then

> Q1:the introduction of the width of W and Z is: A.complex mass scheme; B.fixed width scheme.

> Q2:the introduction of the width of top is: A.complex mass scheme; B.fixed width scheme

>

> if I don't use

> mg5> set complex_mass True

> then

> Q3:the introduction of the width of W and Z is: A.complex mass scheme; B.fixed width scheme.

> Q4:the introduction of the width of top is: A.complex mass scheme; B.fixed width scheme.

>

> I think the answer for Q1 is A and the answer for Q3 is B. but i am not sure the answer for Q2 Q4.

>

> Q5: if i want fixed width scheme for WZ and complex mass scheme for top. what should i do.

>

> Best regards

> Huanyu

>

> --

> You received this question notification because you are an answer

> contact for MadGraph5_aMC@NLO.

HuanyuBi (bihuanyu) said : | #2 |

Hi Olivier,

Thank you for your answer. This solved my problem.

Best regards

Huanyu