Events with virt=QED

Hi Oliver,

Thanks very much for your quick and informative response.
Do you have a rough timescale for the readiness of this feature?

Thanks again,
Jim

Since I'm not working on that, I can not answer that questions.

Marco should be able to provide a timescale.

Cheers,

Olivier

Hi James,
we are currently working on the automation of EW corrections... An indicative timescale for having this feature available in the public version is at least 6 months...

Cheers,

Marco

Hi Marco and Oliver,

OK, thanks very much for your help.

Cheers,
Jim

Thanks Olivier Mattelaer, that solved my question.

Hi Olivier, Marco --

I was wondering if there was any update on VBF with EWK and QCD at NLO. If this just isn't possible, then much of what I've written below is probably a misfire.

What I want is basically VBF W or Z production at NLO -- the following but at NLO: generate p p > W j j QED=4 QCD=4, W > mu v

Is this possible?

In 2.3.3, I tried: "generate p p > mu v j j QED=4 QCD=4 [virt=QED QCD]"

and I just go that: "When running ML5 standalone, multiparticle labels cannot be employed."

This syntax failed, looking with "No particle qed=4": "generate p p > W j j QED=4 QCD=4 [virt=QED QCD], W > mu v"

So I tried: "generate u u > mu+ vm d u QED=4 QCD=4 [virt=QED QCD]"

This seemed to work, in the sense that it didn't fail and it outputted 187 pages of magnificent loops. But I'm left with three questions:

 a) Is this even broadly the correct way of doing this?
 b) I would not trust myself to get all of the possible permutations without using multiparticles, so I'm a bit at a loss of how to do this in practice (it also takes more than a minute for each possibility I've tried). Any suggestions?
 c) Even in principle for (b) -- I don't know how to get the merging right. I looked at the diagrams and always saw exactly 6 external legs (2 in, 4 out though I think they're moved around to avoid crossings in the display). I would have expected that [QCD] would give some extra jets (extra QCD emission). What have I misunderstood?

Thanks a lot --

Jamie

Dear Jamie.

The status is that we can compute EW loop but that we can not handle EW corrections.
The syntax virt= ask to have only the loop and that syntax do not allow for multi particles indeed.

Cheers,

Olivier

> On Dec 1, 2015, at 03:36, James Saxon <email address hidden> wrote:
>
> Question #262183 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/262183
>
> James Saxon posted a new comment:
> Hi Olivier, Marco --
>
> I was wondering if there was any update on VBF with EWK and QCD at NLO.
> If this just isn't possible, then much of what I've written below is
> probably a misfire.
>
> What I want is basically VBF W or Z production at NLO -- the following
> but at NLO: generate p p > W j j QED=4 QCD=4, W > mu v
>
> Is this possible?
>
> In 2.3.3, I tried: "generate p p > mu v j j QED=4 QCD=4 [virt=QED QCD]"
>
> and I just go that: "When running ML5 standalone, multiparticle labels
> cannot be employed."
>
> This syntax failed, looking with "No particle qed=4": "generate p p > W
> j j QED=4 QCD=4 [virt=QED QCD], W > mu v"
>
> So I tried: "generate u u > mu+ vm d u QED=4 QCD=4 [virt=QED QCD]"
>
> This seemed to work, in the sense that it didn't fail and it outputted
> 187 pages of magnificent loops. But I'm left with three questions:
>
> a) Is this even broadly the correct way of doing this?
> b) I would not trust myself to get all of the possible permutations without using multiparticles, so I'm a bit at a loss of how to do this in practice (it also takes more than a minute for each possibility I've tried). Any suggestions?
> c) Even in principle for (b) -- I don't know how to get the merging right. I looked at the diagrams and always saw exactly 6 external legs (2 in, 4 out though I think they're moved around to avoid crossings in the display). I would have expected that [QCD] would give some extra jets (extra QCD emission). What have I misunderstood?
>
> Thanks a lot --
>
> Jamie
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Hi Olivier --

Thanks a lot for this. My impression is that there actually aren't that many codes that do all the EW corrections.

Is there any way to cleanly get the permutations of particles? For instance, I could do

define W = W+ W-
define mu = mu+ mu-
define v = ve vm vt ve~ vm~ vt~
generate p p > W j j QED=4 QCD=4, W > mu v

and just "add process" for all of the "Trying process" lines? And should I add all the crossed and mirrored processes line by line?

Or is this forcing the code to do something it's not yet ready for? (I just don't trust myself to get all the multiparticles by hand.)

Is [virt=QED QCD] virtual QED and QCD, i.e., explaining the lack of extra jets? or is it all QCD? [virt=QED all=QCD] failed for me but [all=QCD] ran OK.

Is it possible to run all QCD with virtual QED?

Thanks --

Jamie

Hi Jamie,

> Is [virt=QED QCD] virtual QED and QCD, i.e., explaining the lack of
> extra jets?

This is all the loop which are tagged QED or QCD.
Since this is only the loop you will not have any extra particles (since this is not the virtual corrections but the real one).

> [virt=QED all=QCD]

This do not make sense, the only output that we have for virt= is a standalone code returning the matrix element value for one phase-space point.
(this returns the finite piece as well as the coefficient of the 1/epsilon expansion)
For all=QCD, the output is a valid code for the phase-space integration, mixing both do not make any sense.

> [all=QCD] ran OK.

Sure this is the default mode (event generation at NLO with MC@NLO method of avoiding double counting with the parton shower)

> Is it possible to run all QCD with virtual QED?

No. if you include only the virtual electroweak without the real contribution, then your result is infinite. You need to include both to have a finite result for infra-red safe observables (KLN theorem).

> Or is this forcing the code to do something it's not yet ready for? (I
> just don’t trust myself to get all the multiparticles by hand.)

I do not understand this question, but clearly the official code is not ready for electroweak correction. (and even in private code, we do not have event generation for EW)

Cheers,

Olivier

> On Dec 1, 2015, at 17:02, James Saxon <email address hidden> wrote:
>
> Question #262183 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/262183
>
> James Saxon posted a new comment:
> Hi Olivier --
>
> Thanks a lot for this. My impression is that there actually aren't that
> many codes that do all the EW corrections.
>
> Is there any way to cleanly get the permutations of particles? For
> instance, I could do
>
> define W = W+ W-
> define mu = mu+ mu-
> define v = ve vm vt ve~ vm~ vt~
> generate p p > W j j QED=4 QCD=4, W > mu v
>
> and just "add process" for all of the "Trying process" lines? And
> should I add all the crossed and mirrored processes line by line?
>
> Or is this forcing the code to do something it's not yet ready for? (I
> just don't trust myself to get all the multiparticles by hand.)
>
> Is [virt=QED QCD] virtual QED and QCD, i.e., explaining the lack of
> extra jets? or is it all QCD? [virt=QED all=QCD] failed for me but
> [all=QCD] ran OK.
>
> Is it possible to run all QCD with virtual QED?
>
> Thanks --
>
> Jamie
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Thanks a lot Olivier, and sorry for my slow questions.

>> Or is this forcing the code to do something it's not yet ready for? (I just don’t trust myself to get all the multiparticles by hand.)
>I do not understand this question, but clearly the official code is not ready for electroweak correction. (and even in private code, we do not have event generation for EW)

What I meant was: since multiparticles don't work, is it advisable to "add process" over and over, to get all the permutations? Or is the code just not really ready to combine all the p p > W j j processes.

>> Is it possible to run all QCD with virtual QED?
> No. if you include only the virtual electroweak without the real contribution, then your result is infinite. You need to include both to have a finite result for infra-red safe observables (KLN theorem).

I understand this also to mean that the result with [virt=QED QCD] that ran OK is not meaningful. Is that correct?

So if I've understood all of this correctly: the best I can do now is just to tack on [QCD], since both real and virtual pieces are included? And the electroweak will come later?

Thanks again --

Jamie

Hi Olivier --

Yet another follow-up: if I can't run with the QED part (i.e., only the virtual corrections are available), can I at least use QCD NLO?

I tried like:

   generate p p > mu+ vm j j QED=4 QCD=4 [QCD]

or

   generate p p > mu+ vm j j QED=4 [QCD]

but I get a lot of this:

WARNING: All Born diagrams do not factorize the same sum of power(s) of the the perturbed order(s) QCD.
This is potentially dangerous as the real-emission diagrams from aMC@NLO will not be consistent with these virtual contributions.
WARNING: Some loop diagrams contributing to this process are discarded because they are not pure (QCD)-perturbation.
Make sure you did not want to include them.

I'm not sure if I should abort, or if I can actually get some level of NLO prediction (even if only QCD).

Thanks again for your direction --

Jamie

Hi Jamie,
this is, because loop diagrams featuring vector bosons in the loop are not included.
These diagrams should typically be either vanishing because of color or color suppressed.
I would suggest to go on with the generation, you will possibly need to turn off the check for the IR poles in order to be able to run the code.
To turn off the checks, please set
#IRPoleCheckThreshold
and
#PrecisionVirtualAtRunTime
to -1d0
inside Cards/FKS_params.dat

Cheers,

Marco

On 04 Dec 2015, at 16:57, James Saxon <email address hidden> wrote:

> Question #262183 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/262183
>
> James Saxon posted a new comment:
> Hi Olivier --
>
> Yet another follow-up: if I can't run with the QED part (i.e., only the
> virtual corrections are available), can I at least use QCD NLO?
>
> I tried like:
>
> generate p p > mu+ vm j j QED=4 QCD=4 [QCD]
>
> or
>
> generate p p > mu+ vm j j QED=4 [QCD]
>
> but I get a lot of this:
>
> WARNING: All Born diagrams do not factorize the same sum of power(s) of the the perturbed order(s) QCD.
> This is potentially dangerous as the real-emission diagrams from aMC@NLO will not be consistent with these virtual contributions.
> WARNING: Some loop diagrams contributing to this process are discarded because they are not pure (QCD)-perturbation.
> Make sure you did not want to include them.
>
> I'm not sure if I should abort, or if I can actually get some level of
> NLO prediction (even if only QCD).
>
> Thanks again for your direction --
>
> Jamie
>
> --
> You received this question notification because you are subscribed to
> the question.

Thanks a lot Marco, this is good to hear. I'll give it a whirl.

Hi Marco --

I tried running with this:

grep -A1 "IRPoleCheckThreshold\|PrecisionVirtualAtRunTime" Cards/FKS_params.dat
#IRPoleCheckThreshold
-1d0
--
#PrecisionVirtualAtRunTime
-1d0

But I got a lot of the errors (ultimately fatal) below. Any other suggestions?

Thanks --

Jamie

 =================================================

 NEW FKS CONFIGURATION:
 FKS configuration number is 18
 FKS partons are: i= 6 j= 2
 with PDGs: i= 3 j= 3

 Enter graph number (iconfig), '0' loops over all graphs

 Soft tests done for (Born) config 1
 Failures: 0
     Soft test 18 PASSED. Fraction of failures: 0.00

 Collinear tests done for (Born) config 1
 Failures: 55
Collinear test 18 FAILED. Fraction of failures: 0.55

 =================================================

 NEW FKS CONFIGURATION:
 FKS configuration number is 19
 FKS partons are: i= 7 j= 2
 with PDGs: i= -4 j= -4

 Enter graph number (iconfig), '0' loops over all graphs

 Soft tests done for (Born) config 1
 Failures: 0
     Soft test 19 PASSED. Fraction of failures: 0.00

 Collinear tests done for (Born) config 1
 Failures: 89
Collinear test 19 FAILED. Fraction of failures: 0.89

 =================================================

 NEW FKS CONFIGURATION:
 FKS configuration number is 20
 FKS partons are: i= 6 j= 2
 with PDGs: i= 4 j= 4

 Enter graph number (iconfig), '0' loops over all graphs

 Soft tests done for (Born) config 1
 Failures: 0
     Soft test 20 PASSED. Fraction of failures: 0.00

 Collinear tests done for (Born) config 1
 Failures: 88
Collinear test 20 FAILED. Fraction of failures: 0.88
Error detected in "launch"
write debug file /afs/cern.ch/work/j/jsaxon/mg5/MG5_aMC_v2_3_3/bob/run_04_tag_1_debug.log
If you need help with this issue please contact us on https://answers.launchpad.net/madgraph5
aMCatNLOError : Some tests failed, run cannot continue.
 Please check that widths of final state particles (e.g. top) have been set to 0 in the param_card.dat.

Hi Jamie,
Did you change any parameter in the run/parameters card?
Cheers
Marco
On Dec 7, 2015 8:08 PM, "James Saxon" <email address hidden>
wrote:

> Question #262183 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/262183
>
> James Saxon posted a new comment:
> Hi Marco --
>
> I tried running with this:
>
> grep -A1 "IRPoleCheckThreshold\|PrecisionVirtualAtRunTime"
> Cards/FKS_params.dat
> #IRPoleCheckThreshold
> -1d0
> --
> #PrecisionVirtualAtRunTime
> -1d0
>
> But I got a lot of the errors (ultimately fatal) below. Any other
> suggestions?
>
> Thanks --
>
> Jamie
>
>
>
> =================================================
>
> NEW FKS CONFIGURATION:
> FKS configuration number is 18
> FKS partons are: i= 6 j= 2
> with PDGs: i= 3 j= 3
>
>
> Enter graph number (iconfig), '0' loops over all graphs
>
>
>
> Soft tests done for (Born) config 1
> Failures: 0
> Soft test 18 PASSED. Fraction of failures: 0.00
>
>
>
> Collinear tests done for (Born) config 1
> Failures: 55
> Collinear test 18 FAILED. Fraction of failures: 0.55
>
> =================================================
>
> NEW FKS CONFIGURATION:
> FKS configuration number is 19
> FKS partons are: i= 7 j= 2
> with PDGs: i= -4 j= -4
>
>
> Enter graph number (iconfig), '0' loops over all graphs
>
>
>
> Soft tests done for (Born) config 1
> Failures: 0
> Soft test 19 PASSED. Fraction of failures: 0.00
>
>
>
> Collinear tests done for (Born) config 1
> Failures: 89
> Collinear test 19 FAILED. Fraction of failures: 0.89
>
> =================================================
>
> NEW FKS CONFIGURATION:
> FKS configuration number is 20
> FKS partons are: i= 6 j= 2
> with PDGs: i= 4 j= 4
>
>
> Enter graph number (iconfig), '0' loops over all graphs
>
>
>
> Soft tests done for (Born) config 1
> Failures: 0
> Soft test 20 PASSED. Fraction of failures: 0.00
>
>
>
> Collinear tests done for (Born) config 1
> Failures: 88
> Collinear test 20 FAILED. Fraction of failures: 0.88
> Error detected in "launch"
> write debug file /afs/
> cern.ch/work/j/jsaxon/mg5/MG5_aMC_v2_3_3/bob/run_04_tag_1_debug.log
> If you need help with this issue please contact us on
> https://answers.launchpad.net/madgraph5
> aMCatNLOError : Some tests failed, run cannot continue.
> Please check that widths of final state particles (e.g. top) have
> been set to 0 in the param_card.dat.
>
> --
> You received this question notification because you are subscribed to
> the question.
>

Wait wait....
Are you setting the orders QED 4,qcd 4?
The EW production should be qcd=0, right?
In the current version all diagrams must factorize the same powers of QCD
Cheers
M
On Dec 7, 2015 8:23 PM, "Marco Zaro" <email address hidden> wrote:

> Hi Jamie,
> Did you change any parameter in the run/parameters card?
> Cheers
> Marco
> On Dec 7, 2015 8:08 PM, "James Saxon" <
> <email address hidden>> wrote:
>
>> Question #262183 on MadGraph5_aMC@NLO changed:
>> https://answers.launchpad.net/mg5amcnlo/+question/262183
>>
>> James Saxon posted a new comment:
>> Hi Marco --
>>
>> I tried running with this:
>>
>> grep -A1 "IRPoleCheckThreshold\|PrecisionVirtualAtRunTime"
>> Cards/FKS_params.dat
>> #IRPoleCheckThreshold
>> -1d0
>> --
>> #PrecisionVirtualAtRunTime
>> -1d0
>>
>> But I got a lot of the errors (ultimately fatal) below. Any other
>> suggestions?
>>
>> Thanks --
>>
>> Jamie
>>
>>
>>
>> =================================================
>>
>> NEW FKS CONFIGURATION:
>> FKS configuration number is 18
>> FKS partons are: i= 6 j= 2
>> with PDGs: i= 3 j= 3
>>
>>
>> Enter graph number (iconfig), '0' loops over all graphs
>>
>>
>>
>> Soft tests done for (Born) config 1
>> Failures: 0
>> Soft test 18 PASSED. Fraction of failures: 0.00
>>
>>
>>
>> Collinear tests done for (Born) config 1
>> Failures: 55
>> Collinear test 18 FAILED. Fraction of failures: 0.55
>>
>> =================================================
>>
>> NEW FKS CONFIGURATION:
>> FKS configuration number is 19
>> FKS partons are: i= 7 j= 2
>> with PDGs: i= -4 j= -4
>>
>>
>> Enter graph number (iconfig), '0' loops over all graphs
>>
>>
>>
>> Soft tests done for (Born) config 1
>> Failures: 0
>> Soft test 19 PASSED. Fraction of failures: 0.00
>>
>>
>>
>> Collinear tests done for (Born) config 1
>> Failures: 89
>> Collinear test 19 FAILED. Fraction of failures: 0.89
>>
>> =================================================
>>
>> NEW FKS CONFIGURATION:
>> FKS configuration number is 20
>> FKS partons are: i= 6 j= 2
>> with PDGs: i= 4 j= 4
>>
>>
>> Enter graph number (iconfig), '0' loops over all graphs
>>
>>
>>
>> Soft tests done for (Born) config 1
>> Failures: 0
>> Soft test 20 PASSED. Fraction of failures: 0.00
>>
>>
>>
>> Collinear tests done for (Born) config 1
>> Failures: 88
>> Collinear test 20 FAILED. Fraction of failures: 0.88
>> Error detected in "launch"
>> write debug file /afs/
>> cern.ch/work/j/jsaxon/mg5/MG5_aMC_v2_3_3/bob/run_04_tag_1_debug.log
>> If you need help with this issue please contact us on
>> https://answers.launchpad.net/madgraph5
>> aMCatNLOError : Some tests failed, run cannot continue.
>> Please check that widths of final state particles (e.g. top) have
>> been set to 0 in the param_card.dat.
>>
>> --
>> You received this question notification because you are subscribed to
>> the question.
>>
>

Hi Marco --

Right, I had set QED=4 QCD=4, since I wanted both the electroweak and VBF diagrams (including, even, interference). Is that not possible?

Should I instead do "QED=4 [QCD]" and then separately "QCD=4 [QCD]"?

Thanks --

Jamie

Yes, you should do the two separately
Note that you need to specify both orders (also the one set to 0)each time
On Dec 8, 2015 6:32 AM, "James Saxon" <email address hidden>
wrote:

> Question #262183 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/262183
>
> James Saxon posted a new comment:
> Hi Marco --
>
> Right, I had set QED=4 QCD=4, since I wanted both the electroweak and
> VBF diagrams (including, even, interference). Is that not possible?
>
> Should I instead do "QED=4 [QCD]" and then separately "QCD=4 [QCD]"?
>
> Thanks --
>
> Jamie
>
> --
> You received this question notification because you are subscribed to
> the question.
>