MadGraph5_aMC@NLO

matching multiparticle processes

Asked by Juhi Dutta

Hi,

I have a naive question regarding matching.for processes involving multiparticles does mg5 automatically take care of matching for the individual processes correctly ?

say I have

import model mssm
define sp = ul dl
define m = sp go
generate p p > sp sp @0
add process p p > sp sp j $ m @1

or should i do the following and add them up ?
:

import model mssm
define m = ul go
generate p p > ul ul @0
add process p p > ul ul j $ m @1

import model mssm
define m = dl go
generate p p > dl dl @0
add process p p > dl dl j $ m @1

import model mssm
define m = ul dl go
generate p p > uldl @0
add process p p > ul dl j $ m @

Regards ,

Juhi

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Solved by:
Olivier Mattelaer
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Revision history for this message
Olivier Mattelaer (olivier-mattelaer) said : 		#1

Dear Juhi,

I do not think that forbidding the final state to be onshell (with the $ syntax) is a good idea, since this will prevent some of the QCD radiation comming from this particles. Due to this, I do not think that any of your syntax are valid.

Concerning your question about multi-particles, I would not encourage to use them like that for matched/merged production.
They are technically speaking no problem of doing so but the correct matching scale is likely to be different for the go and squarks (and if ul and dl do not have the same mass, you also expect different matching scale). therefore it does not really make sense to run them simultaneously since in a single run you are not allowed to specified a different matching scale for each of the process.

Cheers,

Olivier

Revision history for this message
Juhi Dutta (dutta-juhi91) said : 		#2

Hi,

Thank you for the quick response!

Regarding the $ sign, I was using it to remove intermediate resonant
squark/gluon propagators if present in spectrum since they might lead to
overcounting . Am i wrong in thinking of it this way?

For the multiparticles case,my matched djr for both cases are smooth for
same xqcut value which is why i took them as a multiparticle. I guess they
were nearly equal in mass thats why .Thus in general if we consider the
processes, then I must consider all possible pairs like ulul ,uldl,dldl
separately right ?

Regards,

Juhi

On Mon, Aug 3, 2015 at 3:16 PM, Olivier Mattelaer <
<email address hidden>> wrote:

> Your question #269940 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/269940
>
> Status: Open => Answered
>
> Olivier Mattelaer proposed the following answer:
> Dear Juhi,
>
> I do not think that forbidding the final state to be onshell (with the $
> syntax) is a good idea, since this will prevent some of the QCD
> radiation comming from this particles. Due to this, I do not think that
> any of your syntax are valid.
>
> Concerning your question about multi-particles, I would not encourage to
> use them like that for matched/merged production.
> They are technically speaking no problem of doing so but the correct
> matching scale is likely to be different for the go and squarks (and if ul
> and dl do not have the same mass, you also expect different matching
> scale). therefore it does not really make sense to run them simultaneously
> since in a single run you are not allowed to specified a different matching
> scale for each of the process.
>
> Cheers,
>
> Olivier
>
> --
> If this answers your question, please go to the following page to let us
> know that it is solved:
>
> https://answers.launchpad.net/mg5amcnlo/+question/269940/+confirm?answer_id=0
>
> If you still need help, you can reply to this email or go to the
> following page to enter your feedback:
> https://answers.launchpad.net/mg5amcnlo/+question/269940
>
> You received this question notification because you asked the question.
>

Revision history for this message
Olivier Mattelaer (olivier-mattelaer) said : 		#3

Hi,

> Regarding the $ sign, I was using it to remove intermediate resonant
> squark/gluon propagators if present in spectrum since they might lead to
> overcounting . Am i wrong in thinking of it this way?

This is correct.

my problem is that you do
p p > ul ul j $ ul
so you remove the particle itself, which I do not think it make sense.
Indeed this will remove the ul > ul g radiation when the g is relatively soft.
Depending of the value of your width/xqcut, this might be ok, but I’m worry that this can lead to hole in the phase-space.

On the other hand, you indeed need to forbid the other type of particle to go on shell. In particular the gluino.
so p p > ul ul j $ go ur dl ur
is perfectly correct.

> For the multiparticles case,my matched djr for both cases are smooth for
> same xqcut value which is why i took them as a multiparticle. I guess they
> were nearly equal in mass thats why .

yes

> Thus in general if we consider the
> processes, then I must consider all possible pairs like ulul ,uldl,dldl
> separately right ?

That’s correct.

Cheers,

Olivier

On 03 Aug 2015, at 11:01, Juhi Dutta <email address hidden> wrote:

> Question #269940 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/269940
>
> Status: Answered => Open
>
> Juhi Dutta is still having a problem:
> Hi,
>
> Thank you for the quick response!
>
> Regarding the $ sign, I was using it to remove intermediate resonant
> squark/gluon propagators if present in spectrum since they might lead to
> overcounting . Am i wrong in thinking of it this way?
>
> For the multiparticles case,my matched djr for both cases are smooth for
> same xqcut value which is why i took them as a multiparticle. I guess they
> were nearly equal in mass thats why .Thus in general if we consider the
> processes, then I must consider all possible pairs like ulul ,uldl,dldl
> separately right ?
>
> Regards,
>
> Juhi
>
> On Mon, Aug 3, 2015 at 3:16 PM, Olivier Mattelaer <
> <email address hidden>> wrote:
>
>> Your question #269940 on MadGraph5_aMC@NLO changed:
>> https://answers.launchpad.net/mg5amcnlo/+question/269940
>>
>> Status: Open => Answered
>>
>> Olivier Mattelaer proposed the following answer:
>> Dear Juhi,
>>
>> I do not think that forbidding the final state to be onshell (with the $
>> syntax) is a good idea, since this will prevent some of the QCD
>> radiation comming from this particles. Due to this, I do not think that
>> any of your syntax are valid.
>>
>> Concerning your question about multi-particles, I would not encourage to
>> use them like that for matched/merged production.
>> They are technically speaking no problem of doing so but the correct
>> matching scale is likely to be different for the go and squarks (and if ul
>> and dl do not have the same mass, you also expect different matching
>> scale). therefore it does not really make sense to run them simultaneously
>> since in a single run you are not allowed to specified a different matching
>> scale for each of the process.
>>
>> Cheers,
>>
>> Olivier
>>
>> --
>> If this answers your question, please go to the following page to let us
>> know that it is solved:
>>
>> https://answers.launchpad.net/mg5amcnlo/+question/269940/+confirm?answer_id=0
>>
>> If you still need help, you can reply to this email or go to the
>> following page to enter your feedback:
>> https://answers.launchpad.net/mg5amcnlo/+question/269940
>>
>> You received this question notification because you asked the question.
>>
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Revision history for this message
Juhi Dutta (dutta-juhi91) said : 		#4

Hi,

Thanks for the detailed response.I now understand the problem of excluding
the particle itself.

>On the other hand, you indeed need to forbid the other type of particle to
go on shell. In particular the gluino.
so p p > ul ul j $ go ur dl dr
is perfectly correct.

here all other particles refer to the ones which couple directly to ul thus
ur,dl,dr . the cl sl etc which might arise from gluino decays are anyway
discarded as resonant gluino gets rejected.
also in the pythia card i should add all the ids of the other particles in
EXCRES . I hope I understood correctly.

Also I had earlier generated matched multijets processes p p > j j , add p
p > j j j .here I was able to use the collective form of j = u u~ d d~ c~
c s s~ as all of them are massless hence the matching scale was same thus i
didnot have to do all processes separately.

Regards,
Juhi

On Mon, Aug 3, 2015 at 4:01 PM, Olivier Mattelaer <
<email address hidden>> wrote:

> Your question #269940 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/269940
>
> Status: Open => Answered
>
> Olivier Mattelaer proposed the following answer:
> Hi,
>
> > Regarding the $ sign, I was using it to remove intermediate resonant
> > squark/gluon propagators if present in spectrum since they might lead to
> > overcounting . Am i wrong in thinking of it this way?
>
> This is correct.
>
> my problem is that you do
> p p > ul ul j $ ul
> so you remove the particle itself, which I do not think it make sense.
> Indeed this will remove the ul > ul g radiation when the g is relatively
> soft.
> Depending of the value of your width/xqcut, this might be ok, but I’m
> worry that this can lead to hole in the phase-space.
>
> On the other hand, you indeed need to forbid the other type of particle to
> go on shell. In particular the gluino.
> so p p > ul ul j $ go ur dl ur
> is perfectly correct.
>
>
> > For the multiparticles case,my matched djr for both cases are smooth for
> > same xqcut value which is why i took them as a multiparticle. I guess
> they
> > were nearly equal in mass thats why .
>
>
> yes
>
> > Thus in general if we consider the
> > processes, then I must consider all possible pairs like ulul ,uldl,dldl
> > separately right ?
>
> That’s correct.
>
> Cheers,
>
> Olivier
>
> On 03 Aug 2015, at 11:01, Juhi Dutta
> <email address hidden> wrote:
>
> > Question #269940 on MadGraph5_aMC@NLO changed:
> > https://answers.launchpad.net/mg5amcnlo/+question/269940
> >
> > Status: Answered => Open
> >
> > Juhi Dutta is still having a problem:
> > Hi,
> >
> > Thank you for the quick response!
> >
> > Regarding the $ sign, I was using it to remove intermediate resonant
> > squark/gluon propagators if present in spectrum since they might lead to
> > overcounting . Am i wrong in thinking of it this way?
> >
> > For the multiparticles case,my matched djr for both cases are smooth for
> > same xqcut value which is why i took them as a multiparticle. I guess
> they
> > were nearly equal in mass thats why .Thus in general if we consider the
> > processes, then I must consider all possible pairs like ulul ,uldl,dldl
> > separately right ?
> >
> > Regards,
> >
> > Juhi
> >
> > On Mon, Aug 3, 2015 at 3:16 PM, Olivier Mattelaer <
> > <email address hidden>> wrote:
> >
> >> Your question #269940 on MadGraph5_aMC@NLO changed:
> >> https://answers.launchpad.net/mg5amcnlo/+question/269940
> >>
> >> Status: Open => Answered
> >>
> >> Olivier Mattelaer proposed the following answer:
> >> Dear Juhi,
> >>
> >> I do not think that forbidding the final state to be onshell (with the $
> >> syntax) is a good idea, since this will prevent some of the QCD
> >> radiation comming from this particles. Due to this, I do not think that
> >> any of your syntax are valid.
> >>
> >> Concerning your question about multi-particles, I would not encourage to
> >> use them like that for matched/merged production.
> >> They are technically speaking no problem of doing so but the correct
> >> matching scale is likely to be different for the go and squarks (and
> if ul
> >> and dl do not have the same mass, you also expect different matching
> >> scale). therefore it does not really make sense to run them
> simultaneously
> >> since in a single run you are not allowed to specified a different
> matching
> >> scale for each of the process.
> >>
> >> Cheers,
> >>
> >> Olivier
> >>
> >> --
> >> If this answers your question, please go to the following page to let us
> >> know that it is solved:
> >>
> >>
> https://answers.launchpad.net/mg5amcnlo/+question/269940/+confirm?answer_id=0
> >>
> >> If you still need help, you can reply to this email or go to the
> >> following page to enter your feedback:
> >> https://answers.launchpad.net/mg5amcnlo/+question/269940
> >>
> >> You received this question notification because you asked the question.
> >>
> >
> > --
> > You received this question notification because you are an answer
> > contact for MadGraph5_aMC@NLO.
>
> --
> If this answers your question, please go to the following page to let us
> know that it is solved:
>
> https://answers.launchpad.net/mg5amcnlo/+question/269940/+confirm?answer_id=2
>
> If you still need help, you can reply to this email or go to the
> following page to enter your feedback:
> https://answers.launchpad.net/mg5amcnlo/+question/269940
>
> You received this question notification because you asked the question.
>

Revision history for this message
Best Olivier Mattelaer (olivier-mattelaer) said : 		#5

Hi,

> also in the pythia card i should add all the ids of the other particles in
> EXCRES . I hope I understood correctly.

I do not know for sure here. Since I do not know the details of that function (and when it acts).
For go go production, you want to keep the decay into squark (since you do not include it in squark sample)
and therefore you do not want to put EXCRES on the squark in that case.
So it really depends on how you split your sample to avoid double counting.

> Also I had earlier generated matched multijets processes p p > j j , add p
> p > j j j .here I was able to use the collective form of j = u u~ d d~ c~
> c s s~ as all of them are massless hence the matching scale was same thus i
> did not have to do all processes separately.

Exactly.

Cheers,

Olivier

On 03 Aug 2015, at 12:26, Juhi Dutta <email address hidden> wrote:

> Question #269940 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/269940
>
> Status: Answered => Open
>
> Juhi Dutta is still having a problem:
> Hi,
>
> Thanks for the detailed response.I now understand the problem of excluding
> the particle itself.
>
>
>> On the other hand, you indeed need to forbid the other type of particle to
> go on shell. In particular the gluino.
> so p p > ul ul j $ go ur dl dr
> is perfectly correct.
>
> here all other particles refer to the ones which couple directly to ul thus
> ur,dl,dr . the cl sl etc which might arise from gluino decays are anyway
> discarded as resonant gluino gets rejected.
> also in the pythia card i should add all the ids of the other particles in
> EXCRES . I hope I understood correctly.
>
> Also I had earlier generated matched multijets processes p p > j j , add p
> p > j j j .here I was able to use the collective form of j = u u~ d d~ c~
> c s s~ as all of them are massless hence the matching scale was same thus i
> didnot have to do all processes separately.
>
> Regards,
> Juhi
>
> On Mon, Aug 3, 2015 at 4:01 PM, Olivier Mattelaer <
> <email address hidden>> wrote:
>
>> Your question #269940 on MadGraph5_aMC@NLO changed:
>> https://answers.launchpad.net/mg5amcnlo/+question/269940
>>
>> Status: Open => Answered
>>
>> Olivier Mattelaer proposed the following answer:
>> Hi,
>>
>>> Regarding the $ sign, I was using it to remove intermediate resonant
>>> squark/gluon propagators if present in spectrum since they might lead to
>>> overcounting . Am i wrong in thinking of it this way?
>>
>> This is correct.
>>
>> my problem is that you do
>> p p > ul ul j $ ul
>> so you remove the particle itself, which I do not think it make sense.
>> Indeed this will remove the ul > ul g radiation when the g is relatively
>> soft.
>> Depending of the value of your width/xqcut, this might be ok, but I’m
>> worry that this can lead to hole in the phase-space.
>>
>> On the other hand, you indeed need to forbid the other type of particle to
>> go on shell. In particular the gluino.
>> so p p > ul ul j $ go ur dl ur
>> is perfectly correct.
>>
>>
>>> For the multiparticles case,my matched djr for both cases are smooth for
>>> same xqcut value which is why i took them as a multiparticle. I guess
>> they
>>> were nearly equal in mass thats why .
>>
>>
>> yes
>>
>>> Thus in general if we consider the
>>> processes, then I must consider all possible pairs like ulul ,uldl,dldl
>>> separately right ?
>>
>> That’s correct.
>>
>> Cheers,
>>
>> Olivier
>>
>> On 03 Aug 2015, at 11:01, Juhi Dutta
>> <email address hidden> wrote:
>>
>>> Question #269940 on MadGraph5_aMC@NLO changed:
>>> https://answers.launchpad.net/mg5amcnlo/+question/269940
>>>
>>> Status: Answered => Open
>>>
>>> Juhi Dutta is still having a problem:
>>> Hi,
>>>
>>> Thank you for the quick response!
>>>
>>> Regarding the $ sign, I was using it to remove intermediate resonant
>>> squark/gluon propagators if present in spectrum since they might lead to
>>> overcounting . Am i wrong in thinking of it this way?
>>>
>>> For the multiparticles case,my matched djr for both cases are smooth for
>>> same xqcut value which is why i took them as a multiparticle. I guess
>> they
>>> were nearly equal in mass thats why .Thus in general if we consider the
>>> processes, then I must consider all possible pairs like ulul ,uldl,dldl
>>> separately right ?
>>>
>>> Regards,
>>>
>>> Juhi
>>>
>>> On Mon, Aug 3, 2015 at 3:16 PM, Olivier Mattelaer <
>>> <email address hidden>> wrote:
>>>
>>>> Your question #269940 on MadGraph5_aMC@NLO changed:
>>>> https://answers.launchpad.net/mg5amcnlo/+question/269940
>>>>
>>>> Status: Open => Answered
>>>>
>>>> Olivier Mattelaer proposed the following answer:
>>>> Dear Juhi,
>>>>
>>>> I do not think that forbidding the final state to be onshell (with the $
>>>> syntax) is a good idea, since this will prevent some of the QCD
>>>> radiation comming from this particles. Due to this, I do not think that
>>>> any of your syntax are valid.
>>>>
>>>> Concerning your question about multi-particles, I would not encourage to
>>>> use them like that for matched/merged production.
>>>> They are technically speaking no problem of doing so but the correct
>>>> matching scale is likely to be different for the go and squarks (and
>> if ul
>>>> and dl do not have the same mass, you also expect different matching
>>>> scale). therefore it does not really make sense to run them
>> simultaneously
>>>> since in a single run you are not allowed to specified a different
>> matching
>>>> scale for each of the process.
>>>>
>>>> Cheers,
>>>>
>>>> Olivier
>>>>
>>>> --
>>>> If this answers your question, please go to the following page to let us
>>>> know that it is solved:
>>>>
>>>>
>> https://answers.launchpad.net/mg5amcnlo/+question/269940/+confirm?answer_id=0
>>>>
>>>> If you still need help, you can reply to this email or go to the
>>>> following page to enter your feedback:
>>>> https://answers.launchpad.net/mg5amcnlo/+question/269940
>>>>
>>>> You received this question notification because you asked the question.
>>>>
>>>
>>> --
>>> You received this question notification because you are an answer
>>> contact for MadGraph5_aMC@NLO.
>>
>> --
>> If this answers your question, please go to the following page to let us
>> know that it is solved:
>>
>> https://answers.launchpad.net/mg5amcnlo/+question/269940/+confirm?answer_id=2
>>
>> If you still need help, you can reply to this email or go to the
>> following page to enter your feedback:
>> https://answers.launchpad.net/mg5amcnlo/+question/269940
>>
>> You received this question notification because you asked the question.
>>
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Revision history for this message
Juhi Dutta (dutta-juhi91) said : 		#6

Thanks Olivier Mattelaer, that solved my question.