Code review comment for lp:~maddevelopers/mg5amcnlo/NLO_decay_process

HI Rik,

It is really cool that decay process works at NLO. I quickly tested one process in order to compare with SMWidth. If one wants to calculate the total width for Z (which can be used by MadWidth for CMS@NLO for example), I

define f = j l+ l- vl vl~ ta+ ta-
generate z > f f [QCD]

It is apparent that there is no QCD corrections to some subprocesses like z > l+ l-. The program crashes since no virtual and real diagrams will be generated.

Is it possible to automatically realize if there is no QCD corrections and only calculates tree-level? Or you think it is better to do it in MadWidth to decide which subprocesses have QCD corrections.

A tiny thing: in summary.txt and also the output, it is

      Final results and run summary:
      Process z > j j [QCD]
      Run at l-l collider (6500.0 + 6500.0 GeV)
      (Partial) decay width: 1.761e+00 +- 2.0e-03 GeV
      Ren. and fac. scale uncertainty: +0.4% -0.3%

Can you remove "Run at l-l collider (6500.0 + 6500.0 GeV)". Moreover, if one wants to change the scale, how can one set in decay process?

@Marco: do you think how easy/difficult to implement Rik's implementation in EW branches ? It might be quite useful and have some complicated comparison between MG5 and SMWidth.

I will give a serious report later and compare the numbers with SMWidth.

Great work and awesome !

Cheers,

Hua-Sheng

On Oct 9, 2015, at 11:33 AM, Olivier Mattelaer <email address hidden> wrote:

> Hi Rik,
>
> I put to “no cut” all the run_card parameter flagged as “cut” in the python object. (The same will apply to all future cut)
> This is done at the default run_card level, so all the cut are still allowed to be modified but are not present by default.
> This is the exact behaviour that we have @LO.
>
> When trying to test, I face this error:
> aMCatNLOError : Decay processes can only be run at fixed order.
>
> So I have also change the default question to:
>
> The following switches determine which operations are executed:
> 1 Perturbative order of the calculation: order=NLO
> 2 Fixed order (no event generation and no MC@[N]LO matching): fixed_order=ON
> 3 Shower the generated events: shower=Not available for decay
> 4 Decay particles with the MadSpin module: madspin=Not available for decay
> 5 Add weights to the events based on changing model parameters: reweight=Not available for decay
> Either type the switch number (1 to 5) to change its default setting,
> or set any switch explicitly (e.g. type 'order=LO' at the prompt)
> Type '0', 'auto', 'done' or just press enter when you are done.
> [0, 1, auto, done, order=LO, order=NLO, fixed_order=ON, LO, NLO][60s to answer]
>
> Such that this is automatically a good setup which is used and all unsupported case are forbidden.
>
> For both of them, I had to change the way aMC@NLO supports the proc_characteristic object/file.
> So Marco please take a look.
>
> Cheers,
>
> Olivier
>
>
> On 08 Oct 2015, at 19:42, Rikkert Frederix <email address hidden> wrote:
>
>> Hi Olivier,
>>
>> That would be great. It's just the 'ptj', 'mll_sf' and 'ptgmin' that should be set to zero.
>>
>> Thanks,
>> Rikkert
>>
>> --
>> https://code.launchpad.net/~maddevelopers/mg5amcnlo/NLO_decay_process/+merge/273880
>> Your team MadDevelopers is subscribed to branch lp:~maddevelopers/mg5amcnlo/2.3.3.
>
>
> --
> https://code.launchpad.net/~maddevelopers/mg5amcnlo/NLO_decay_process/+merge/273880
> You are requested to review the proposed merge of lp:~maddevelopers/mg5amcnlo/NLO_decay_process into lp:~maddevelopers/mg5amcnlo/2.3.3.