# Error in computation of bpower

Dear experts,

I am using the SMEFT@NLO model available here: http://

In version 2.7.3, I first import the model with a restriction card

> import model SMEFTatNLO-NLO

then try to generate a simple ttbar process

> generate p p > t t~ QCD=2 QED=0 NP=2 [QCD]

(note that this example is given in the wiki above)

Computation is interrupted due to multiple occurrences of

"Error in computation of bpower:

not an integer 1.9999975547352327"

Is this a known issue?

Cheers,

Baptiste

## Question information

- Language:
- English Edit question

- Status:
- Solved

- Assignee:
- Eleni Vryonidou Edit question

- Solved by:
- Baptiste Ravina

- Solved:
- 2020-09-12

- Last query:
- 2020-09-12

- Last reply:
- 2020-09-12

Did you see this comment in the link that you point:

> The 3.0.3-neworders development branch (tarball <https:/

Cheers,

Olivier

> On 11 Sep 2020, at 18:15, Baptiste Ravina <email address hidden> wrote:

>

> New question #692868 on MadGraph5_aMC@NLO:

> https:/

>

> Dear experts,

>

> I am using the SMEFT@NLO model available here: http://

>

> In version 2.7.3, I first import the model with a restriction card

>> import model SMEFTatNLO-NLO

>

> then try to generate a simple ttbar process

>> generate p p > t t~ QCD=2 QED=0 NP=2 [QCD]

> (note that this example is given in the wiki above)

>

> Computation is interrupted due to multiple occurrences of

> "Error in computation of bpower:

> not an integer 1.9999975547352327"

>

> Is this a known issue?

> Cheers,

> Baptiste

>

> --

> You received this question notification because you are an answer

> contact for MadGraph5_aMC@NLO.

Baptiste Ravina (bravina) said : | #2 |

Hi Olivier,

Yes I did see that. According to that last sentence, I would expect 2.7.3 to work if I my only non-zero operator is ctG? Maybe there's something else I should be doing with the restriction card? Should I comment out the four-fermion operators rather than setting them to zero/epsilon?

Cheers,

Baptiste

I'm not an author of that model, so I can not comment on that.

I have assign the question to one author of the model, but they are no assurance that they will answer to the question asked here.

Cheers,

Olivier

Baptiste Ravina (bravina) said : | #4 |

Hi Olivier,

I followed up with one of the authors and it seems I do need to set those four-fermion operators to exactly zero (rather than small values as per the twiki recommendation, or commented out). I'll mark this question as answered then :)

Thanks,

Baptiste