LNV for symmetry limit

> Also you mentioned that in each process the full spin correlation is taken into account, is that correct?

Yes both case have full spin-correlation

> I get in both cases the same cross section (4.67e+4 pb) but the Events only contain the un-decayed W boson, no muons as final states. Which looks like this:

This is because you use:
> (ww > mu+ nn ...
and not
> (ww > mu nn ...

so you do only allow the W+ to decay and not the w-
so your process definition
is equivalent to
> generate ud ud > W+, (W+> mu+ nn, (nn > mu+ ud ud))

> add process ud ud > W-

and therefore you are dominated by this second process.

if you were using
> generate ud ud > ww, (ww > mu nn, (nn > mu+ ud ud))

then events is then

> <event>
> 8 1 +1.3684000e-04 7.90879200e+01 7.81860800e-03 1.33166000e-01
> -2 -1 0 0 0 501 -0.0000000000e+00 +0.0000000000e+00 +1.1826607199e+02 1.1826607202e+02 2.5500000000e-03 0.0000e+00 1.0000e+00
> 1 -1 0 0 501 0 +0.0000000000e+00 -0.0000000000e+00 -1.3222091597e+01 1.3222092557e+01 5.0400000000e-03 0.0000e+00 -1.0000e+00
> -24 2 1 2 0 0 +0.0000000000e+00 +3.5527136788e-15 +1.0504398040e+02 1.3148816458e+02 7.9087923266e+01 0.0000e+00 0.0000e+00
> 8000018 2 3 3 0 0 -8.3051308488e+00 -1.7920398876e+01 +1.0873246226e+02 1.1139508227e+02 1.4000003925e+01 0.0000e+00 0.0000e+00
> 13 1 3 3 0 0 +8.3051308488e+00 +1.7920398876e+01 -3.6884818627e+00 2.0093082311e+01 1.0566000000e-01 0.0000e+00 -1.0000e+00
> -13 1 4 4 0 0 +3.8246047848e-01 -1.1734431506e+01 +5.5630934818e+01 5.6856444064e+01 1.0566000000e-01 0.0000e+00 1.0000e+00
> 1 1 4 4 502 0 -3.2979059315e+00 -2.2830375504e+00 +8.0039064746e+00 8.9527084307e+00 5.0400000000e-03 0.0000e+00 -1.0000e+00
> -2 1 4 4 0 502 -5.3896853957e+00 -3.9029298190e+00 +4.5097620967e+01 4.5585929772e+01 2.5500000000e-03 0.0000e+00 1.0000e+00

I did not check your second syntax but I guess this is the same.

Cheers,

Olivier

> On 7 Jun 2022, at 17:35, Johannes Rosskopp <email address hidden> wrote:
>
> New question #702100 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/702100
>
> Hi Olivier,
>
> I encountered a strange behavior of MG I cannot explain.
> It is about the model file and param card I sent to you via E-Mail.
>
> The two syntaxes I used are
> (1)generate ud ud > ww, (ww > mu nn, (nn > mu ud ud))
> (2)generate ud ud > ww, (ww > mu mu ud ud) / ve vm vt h a z
>
> where
> define ud = u u~ d d~
> define ww = w+ w-
> define mu = mu+ mu-
> define nn = n4 n5
>
> as you already mentioned to me I checked the diagrams in the HTML, and indeed in (1) there is only one process per page, whereas in (2) there are multiple processes with different heavy neutrinos as intermediate particles. As I understand it know that means that (1) neglects interference between diagrams with different heavy nu's as intermediates whereas (2) takes interference into account. Also you mentioned that in each process the full spin correlation is taken into account, is that correct?
>
> The result is that when looking at the events in case
> (1) there are LNC and LNV events. i.e. there are mu+ and mu- un all combinations as final states in the events
> (2) there are only LNC events, i.e. there are only mu+ mu- in exactly that lepton number conserving combination (no mu+ mu+ or mu- mu-)
>
> That, for me, makes totally sense so far.
>
>
> The only thing left is that when I try generating only LNV events by
> (1')generate ud ud > ww, (ww > mu+ nn, (nn > mu+ ud ud))
> (2')generate ud ud > ww, (ww > mu+ mu+ ud ud) / ve vm vt h a z
>
> I get in both cases the same cross section (4.67e+4 pb) but the Events only contain the un-decayed W boson, no muons as final states. Which looks like this:
>
> <event>
> 3 1 +4.6728000e+04 7.98243600e+01 7.81860800e-03 1.32955100e-01
> 1 -1 0 0 501 0 +0.0000000000e+00 +0.0000000000e+00 +3.9849373498e+01 3.9849373817e+01 5.0400000000e-03 0.0000e+00 -1.0000e+00
> -2 -1 0 0 0 501 -0.0000000000e+00 -0.0000000000e+00 -3.9975084836e+01 3.9975084917e+01 2.5500000000e-03 0.0000e+00 1.0000e+00
> -24 1 1 2 0 0 +0.0000000000e+00 +0.0000000000e+00 -1.2571133785e-01 7.9824458734e+01 7.9824359746e+01 0.0000e+00 -1.0000e+00
> <mgrwt>
> <rscale> 0 0.79824360E+02</rscale>
> <asrwt>0</asrwt>
> <pdfrwt beam="1"> 1 1 0.61306729E-02 0.79824360E+02</pdfrwt>
> <pdfrwt beam="2"> 1 -2 0.61500131E-02 0.79824360E+02</pdfrwt>
> <totfact> 0.12768623E+05</totfact>
> </mgrwt>
> </event>
>
> What I expected would be to get zero cross section in case (2') as there are no LNV events as also validated by (2). And also to get LNV events with muons in (1') as they also appear in (1).
>
>
>
> cheers
> Johannes
>
>
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