Madspin error: KeyError : -4

[Sébastien Brochet]

Dear experts,

I'm facing an issue while trying to run Madspin on a simple process. Basically, I'm trying to convert the Madgraph4 syntax:

pp>(s1>tt~)jj (s1 is a particle defined in a custom model, topBSM)

to Madgraph5. First, I came up with ' p p > s1 > t t~ j j ' but it does not do what I want, ie forcing the decay of s1 to t t~. Next, I tried ' p p > s1 j j, s1 > t t~ '. This time, it's seems to be ok, but I have an error when trying to run MadSpin.

I use the following MadSpin configuration:

decay s1 > t t~, (t > w+ b, w+ > all all), (t~ > w- b~, w- > all all)

MadSpin crash with the following error (debug log attached, run 03):

    INFO: detect independant decays
    Command "launch" interrupted with error:
    KeyError : -4

If I try with the default MadSpin configuration (top, W and Z decays), the error is different (log attached, run 04):

    INFO: generating the production square matrix element
    INFO: generate p p > s1 j j, s1 > t t~ --no_warning=duplicate;
    INFO: Done 8.089
    INFO: keeping dummy decay for passthrough mode
    INFO: generating the full square matrix element (with decay)
    INFO: generate p p > s1 j j, (t > b w+ , w+ > all all QCD=99), ( s1 > t t~, (t > b w+ , w+ > all all QCD=99)) --no_warning=duplicate;
    Command "launch" interrupted with error:
    KeyError : 6000047 (this is the PDG ID of s1)

I've also tried to generate only 'p p > s1 j j' in MadGraph, and using MadSpin for the decay, but it fails with the same error.

Am I doing something wrong or is this a bug in MadSpin?

I attached two LHE files:
unweighted_events_pp_s1.lhe.gz : process p p > s1 j j
unweighted_events_pp_s1_tt_s1_tt.lhe.gz : process p p > s1 j j, s1 > t t~

Thanks a lot!!

[Sébastien Brochet (blinkseb)]

I forgot to add the UFO model in case you need it to launch MadSpin. You can find it here:
https://www.dropbox.com/s/b27wbftflih2flz/topBSM_UFO.zip?dl=!

Thanks!

[Olivier Mattelaer (olivier-mattelaer)]

Hi,

The correct way to use MadSpin is to ask for
> p p > s1 j j
at the production level (i.e. generate p p > s1 j j)

and then ask the full decay in madspin
> decay s1 > t t~, (t > w+ b, w+ > all all), (t~ > w- b~, w- > all all)

in the madspin_card.dat

Cheers,

Olivier

On 24 Mar 2015, at 22:49, Sébastien Brochet <email address hidden> wrote:

> I forgot to add the UFO model in case you need it to launch MadSpin. You can find it here:
> https://www.dropbox.com/s/b27wbftflih2flz/topBSM_UFO.zip?dl=!
>
> Thanks!
>
> --
> You received this bug notification because you are subscribed to
> MadGraph5_aMC@NLO.
> https://bugs.launchpad.net/bugs/1435527
>
> Title:
> Madspin error: KeyError : -4
>
> Status in MadGraph5_aMC@NLO Generator:
> New
>
> Bug description:
> Dear experts,
>
> I'm facing an issue while trying to run Madspin on a simple process.
> Basically, I'm trying to convert the Madgraph4 syntax:
>
> pp>(s1>tt~)jj (s1 is a particle defined in a custom model, topBSM)
>
> to Madgraph5. First, I came up with ' p p > s1 > t t~ j j ' but it
> does not do what I want, ie forcing the decay of s1 to t t~. Next, I
> tried ' p p > s1 j j, s1 > t t~ '. This time, it's seems to be ok, but
> I have an error when trying to run MadSpin.
>
> I use the following MadSpin configuration:
>
> decay s1 > t t~, (t > w+ b, w+ > all all), (t~ > w- b~, w- > all all)
>
> MadSpin crash with the following error (debug log attached, run 03):
>
> INFO: detect independant decays
> Command "launch" interrupted with error:
> KeyError : -4
>
> If I try with the default MadSpin configuration (top, W and Z decays),
> the error is different (log attached, run 04):
>
> INFO: generating the production square matrix element
> INFO: generate p p > s1 j j, s1 > t t~ --no_warning=duplicate;
> INFO: Done 8.089
> INFO: keeping dummy decay for passthrough mode
> INFO: generating the full square matrix element (with decay)
> INFO: generate p p > s1 j j, (t > b w+ , w+ > all all QCD=99), ( s1 > t t~, (t > b w+ , w+ > all all QCD=99)) --no_warning=duplicate;
> Command "launch" interrupted with error:
> KeyError : 6000047 (this is the PDG ID of s1)
>
> I've also tried to generate only 'p p > s1 j j' in MadGraph, and using
> MadSpin for the decay, but it fails with the same error.
>
> Am I doing something wrong or is this a bug in MadSpin?
>
> I attached two LHE files:
> unweighted_events_pp_s1.lhe.gz : process p p > s1 j j
> unweighted_events_pp_s1_tt_s1_tt.lhe.gz : process p p > s1 j j, s1 > t t~
>
> Thanks a lot!!
>
> To manage notifications about this bug go to:
> https://bugs.launchpad.net/mg5amcnlo/+bug/1435527/+subscriptions

[Sébastien Brochet (blinkseb)]

Hi Olivier,

Thanks for your answer. I already tried to do that, and it fails with
the exact same error (keyerror)

2015-03-24 15:45 GMT+01:00 Olivier Mattelaer <email address hidden>:
> Hi,
>
>
> The correct way to use MadSpin is to ask for
>> p p > s1 j j
> at the production level (i.e. generate p p > s1 j j)
>
> and then ask the full decay in madspin
>> decay s1 > t t~, (t > w+ b, w+ > all all), (t~ > w- b~, w- > all all)
>
> in the madspin_card.dat
>
> Cheers,
>
> Olivier
>
> On 24 Mar 2015, at 22:49, Sébastien Brochet <email address hidden>
> wrote:
>
>> I forgot to add the UFO model in case you need it to launch MadSpin. You can find it here:
>> https://www.dropbox.com/s/b27wbftflih2flz/topBSM_UFO.zip?dl=!
>>
>> Thanks!
>>
>> --
>> You received this bug notification because you are subscribed to
>> MadGraph5_aMC@NLO.
>> https://bugs.launchpad.net/bugs/1435527
>>
>> Title:
>> Madspin error: KeyError : -4
>>
>> Status in MadGraph5_aMC@NLO Generator:
>> New
>>
>> Bug description:
>> Dear experts,
>>
>> I'm facing an issue while trying to run Madspin on a simple process.
>> Basically, I'm trying to convert the Madgraph4 syntax:
>>
>> pp>(s1>tt~)jj (s1 is a particle defined in a custom model, topBSM)
>>
>> to Madgraph5. First, I came up with ' p p > s1 > t t~ j j ' but it
>> does not do what I want, ie forcing the decay of s1 to t t~. Next, I
>> tried ' p p > s1 j j, s1 > t t~ '. This time, it's seems to be ok, but
>> I have an error when trying to run MadSpin.
>>
>> I use the following MadSpin configuration:
>>
>> decay s1 > t t~, (t > w+ b, w+ > all all), (t~ > w- b~, w- > all all)
>>
>> MadSpin crash with the following error (debug log attached, run 03):
>>
>> INFO: detect independant decays
>> Command "launch" interrupted with error:
>> KeyError : -4
>>
>> If I try with the default MadSpin configuration (top, W and Z decays),
>> the error is different (log attached, run 04):
>>
>> INFO: generating the production square matrix element
>> INFO: generate p p > s1 j j, s1 > t t~ --no_warning=duplicate;
>> INFO: Done 8.089
>> INFO: keeping dummy decay for passthrough mode
>> INFO: generating the full square matrix element (with decay)
>> INFO: generate p p > s1 j j, (t > b w+ , w+ > all all QCD=99), ( s1 > t t~, (t > b w+ , w+ > all all QCD=99)) --no_warning=duplicate;
>> Command "launch" interrupted with error:
>> KeyError : 6000047 (this is the PDG ID of s1)
>>
>> I've also tried to generate only 'p p > s1 j j' in MadGraph, and using
>> MadSpin for the decay, but it fails with the same error.
>>
>> Am I doing something wrong or is this a bug in MadSpin?
>>
>> I attached two LHE files:
>> unweighted_events_pp_s1.lhe.gz : process p p > s1 j j
>> unweighted_events_pp_s1_tt_s1_tt.lhe.gz : process p p > s1 j j, s1 > t t~
>>
>> Thanks a lot!!
>>
>> To manage notifications about this bug go to:
>> https://bugs.launchpad.net/mg5amcnlo/+bug/1435527/+subscriptions
>
> --
> You received this bug notification because you are subscribed to the bug
> report.
> https://bugs.launchpad.net/bugs/1435527
>
> Title:
> Madspin error: KeyError : -4
>
> Status in Mad...

[Sébastien Brochet (blinkseb)]

Dear experts, I had some time to investigate the issue and found the root cause. I attach a patch for the fix.

I have the following decay chain :

s1 > t t~
t~ > w- b~
w- > all all
t > w+ b
w+ > all all

There should be five decays. If you look at the code, where the decays chain is built (decay,py, lines 431 - 457), there's some recursion going on, where propa_id is decreased by one each time. Now, for the first decay, I have two particles in my case, so 3 iterations of the for loop line 444 (first is s1, next t and finally t~). But, add_decay is each time called with the same propa_id (-2 in this case), which means that the t decay chain will have ids -2, -3, and will then be overwritted by the t~ decay chain, with the same ids.

As a result, self.nb_decays (5 in this case) is correct, but the dict is missing one decay leg, resulting in a crash later on when some code tries to access the -4 id.

The attached patched, against the 2.3 branch, fix this issue.

Thanks

[Sébastien Brochet (blinkseb)]

The previous patch broke madspin for all others processes. I attach a new patch which should hopefully work for all processes.

[Pierre Artoisenet (partois)]

Hi Sebastien,

Many thanks for the fix, I imported your patch into a separated branch and asked the modification to be imported into 2.3