Syntax conflict between mg5amc and madspin in 3.1.x and 3.2.x

[Richard Ruiz]

Hi Folks,

I am not entirely sure this is a bug but guidance is appreciated either way. In short, it seems like the new "recommended" syntax for mg5amc in 3.1.x and 3.2.x is not yet compatible with MadSpin. (Though maybe it is and I am just doing something silly.)

Using the following script (a simple charged current Drell-Yan production of a sterile neutrino), I can generate events with mg5amc but MadSpin fails to compile or understand the process banner. I have tried different variations of "generate" with different responses from MadSpin (see below).

Let me know if more details are needed.

cheers,
richard

Script:
-----------------------------
define ee = e+ e-
generate p p > n1 ee QED=2 QCD=0 [QCD] #option 1 <~~~ see below
#generate p p > n1 ee QED^2=4 QCD^2=0 [QCD] #option 2 <~~~ see below
#generate p p > n1 ee EW^2=4 QCD^2=0 [QCD] #option 3 <~~~ see below
#generate p p > n1 ee EW=2 aS=0 [QCD] #option 4 <~~~ see below
output HeavyN_CCDY_Test
launch HeavyN_CCDY_Test
order=lo
shower=py8
madspin=onshell
set LHC 13
set pdlabel lhapdf
set nevents 100
set no_parton_cut
set VeN1 1
set mn1 40
decay n1 > ee j j
done

----------------------------------------------------
#option 1

Everything works with this syntax when using version 3.1.0(bzr) but not when using 3.2.x

----------------------------------------------------
#option 2

mg5amc works but madspin fails to acknowledge syntax for 3.1.x and 3.2.x. The terminal output is:

...
...
...
INFO: generating the production square matrix element for onshell
INFO: generating the full matrix element squared (with decay)
INFO: generate matrix element for decay only (1 - > N).
Command "launch auto " interrupted with error:
InvalidCmd : model order 2 not valid for this model (valid one are: QCD, QED, EW, EW^2, aEW, aS). Please correct
Please report this bug on https://bugs.launchpad.net/mg5amcnlo

----------------------------------------------------
#option 3

mg5amc works but madspin fails to acknowledge syntax for 3.1.x and 3.2.x. The terminal output is:

...
...
...
INFO: generating the production square matrix element for onshell
INFO: generating the full matrix element squared (with decay)
INFO: generate matrix element for decay only (1 - > N).
Command "launch auto " interrupted with error:
InvalidCmd : model order 2 not valid for this model (valid one are: QCD, QED, EW, EW^2, aEW, aS). Please correct
Please report this bug on https://bugs.launchpad.net/mg5amcnlo

----------------------------------------------------
#option 4

mg5amc works but madspin fails to generate a matrix element for 3.1.x and 3.2.x. The terminal output is:

...
...
...
INFO: generating the production square matrix element for onshell
INFO: generating the full matrix element squared (with decay)
INFO: generate matrix element for decay only (1 - > N).
Command "launch auto " interrupted with error:
NoDiagramException : No amplitudes generated from process Process: g/u/c/d/s/b/u~/c~/d~/s~/b~ g/u/c/d/s/b/u~/c~/d~/s~/b~ > n1 e-/e+ g/d/u/s/c/b/b~/c~/s~/u~/d~ EW=2 QED=99 QCD^2<=0 @2. Please enter a valid process
Please report this bug on https://bugs.launchpad.net/mg5amcnlo

[Olivier Mattelaer (olivier-mattelaer)]

Hi,

To my point of view only syntax #1 should work with MadSpin, the rest is indeed not supported syntax.
(Obviously a better error message would be nicer).

Will look at fixing #1 and having better crash for the other option

Cheers,

Olivier

> On 5 Oct 2021, at 20:31, Richard Ruiz <email address hidden> wrote:
>
> Public bug reported:
>
> Hi Folks,
>
> I am not entirely sure this is a bug but guidance is appreciated either
> way. In short, it seems like the new "recommended" syntax for mg5amc in
> 3.1.x and 3.2.x is not yet compatible with MadSpin. (Though maybe it is
> and I am just doing something silly.)
>
> Using the following script (a simple charged current Drell-Yan
> production of a sterile neutrino), I can generate events with mg5amc but
> MadSpin fails to compile or understand the process banner. I have tried
> different variations of "generate" with different responses from MadSpin
> (see below).
>
> Let me know if more details are needed.
>
> cheers,
> richard
>
>
> Script:
> -----------------------------
> define ee = e+ e-
> generate p p > n1 ee QED=2 QCD=0 [QCD] #option 1 <~~~ see below
> #generate p p > n1 ee QED^2=4 QCD^2=0 [QCD] #option 2 <~~~ see below
> #generate p p > n1 ee EW^2=4 QCD^2=0 [QCD] #option 3 <~~~ see below
> #generate p p > n1 ee EW=2 aS=0 [QCD] #option 4 <~~~ see below
> output HeavyN_CCDY_Test
> launch HeavyN_CCDY_Test
> order=lo
> shower=py8
> madspin=onshell
> set LHC 13
> set pdlabel lhapdf
> set nevents 100
> set no_parton_cut
> set VeN1 1
> set mn1 40
> decay n1 > ee j j
> done
>
> ----------------------------------------------------
> #option 1
>
> Everything works with this syntax when using version 3.1.0(bzr) but not
> when using 3.2.x
>
> ----------------------------------------------------
> #option 2
>
> mg5amc works but madspin fails to acknowledge syntax for 3.1.x and
> 3.2.x. The terminal output is:
>
> ...
> ...
> ...
> INFO: generating the production square matrix element for onshell
> INFO: generating the full matrix element squared (with decay)
> INFO: generate matrix element for decay only (1 - > N).
> Command "launch auto " interrupted with error:
> InvalidCmd : model order 2 not valid for this model (valid one are: QCD, QED, EW, EW^2, aEW, aS). Please correct
> Please report this bug on https://bugs.launchpad.net/mg5amcnlo
>
>
> ----------------------------------------------------
> #option 3
>
>
> mg5amc works but madspin fails to acknowledge syntax for 3.1.x and 3.2.x. The terminal output is:
>
> ...
> ...
> ...
> INFO: generating the production square matrix element for onshell
> INFO: generating the full matrix element squared (with decay)
> INFO: generate matrix element for decay only (1 - > N).
> Command "launch auto " interrupted with error:
> InvalidCmd : model order 2 not valid for this model (valid one are: QCD, QED, EW, EW^2, aEW, aS). Please correct
> Please report this bug on https://bugs.launchpad.net/mg5amcnlo
>
>
> ----------------------------------------------------
> #option 4
>
> mg5amc works but madspin fails to generate a matrix element for 3.1.x
> and 3.2.x. The terminal output is:
>
> ...
> ...
> ...
> INFO: generating the pr...