Batch_file pp->h XS * BR

Asked by Nurhan Karahan on 2020-05-03

Dear Calchep Team,

we try to obtain the figure in https://twiki.cern.ch/twiki/pub/LHCPhysics/LHCHXSWGCrossSectionsFigures/XSBR_8TeV_SM_LM.eps via Calchep. First we focus on pp->h->ZZ-> 4 l. For this process, we use the batch file below;

Model : SM(+hgg)
Model changed: False
Gauge : Feynman
Process : p,p->h
Decay : h->le,Le,le,Le
Composite : p=u,d,s,c,b,U,D,S,C,B,G
Composite : le=e,m
Composite : Le=E,M
Remove : W+,W-,A
pdf1 : PDT:cteq6l1(proton)
pdf2 : PDT:cteq6l1(proton)
p1 : 4000
p2 : 4000

Run parameter: Mh
Run begin : 90
Run step size: 10
Run n steps : 18

Number of events (per run step): 10000
Filename: visible6
NTuple: False
Cleanup: False
Parallelization method: local
Max number of nodes: 8
Max number of processes per node: 1
sleep time : 3
nice level : 19
nSess_1 : 5
nCalls_1 : 10000
nSess_2 : 5
nCalls_2 : 10000

We have some problems and questions;
1) Remove command can be used for Decays? if not, how we can define pp->h->ZZ->4l at batch file
2) With the above batch file we got some errors (empty y range [0:0], adjusting to [-1:1]), and the calculation was not complete.
What is the problem?

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Alexander Belyaev (alexander.belyaev) said :
#2

Dear Nurhan,

1. Please note that
"Warning: empty y range [0:0], adjusting to [-1:1]"
is the WARNING which is not the ERROR
this warning comes from gnuplotter and has nothing to do with your problem

2. You do not need to spend your time on generation of 10000 events
if you want to find cross section
it is enough to request just 1 event (do not put zero since connection of the production + decay will work only if you request non-zero number of events)
So, use

Number of events (per run step): 1

line, for example

3. Remove statement was used for production but not decay and this was your problem
You need to use

Remove decay : W+,W-,A,h

statement.
What happened is that you did not remove intermediate particles for 4-body decay,
the accuracy of the integration was bad (you need to watch and control it)
and as a consequence, events were not generated and I could quess that the process was caught in the infinite loop, so it did not finish

4. Finally, for 4-body decay I advice you do you more points for the integration and more iterations to have convergence faster and to make the error of the integration lower, so you can use these line, for example

Sess_1 : 10
nCalls_1 : 100000
nSess_2 : 10
nCalls_2 : 100000

Best,
Sasha

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Nurhan Karahan (ckarahan) said :
#3

thanks, it works now. However, there is still some problem about the \sigma*BR plot for the processes given in https://twiki.cern.ch/twiki/pub/LHCPhysics/LHCHXSWGCrossSectionsFigures/XSBR_8TeV_SM_LM.eps .

For instance, we use the batch file below for pp->h->ZZ->4l. Our figure is different for Mh<185 GeV. We do not understand the reason. Is it related to the decay width h->ZZ in Calchep ?

Model : SM(+hgg)
Model changed: False
Gauge : Feynman
Process : p,p->h
Decay : h->le,Le,le,Le
Remove decay : W+,W-,A,h
Composite : p=u,d,s,c,b,U,D,S,C,B,G
Composite : le=e,m
Composite : Le=E,M

pdf1 : PDT:cteq6l1(proton)
pdf2 : PDT:cteq6l1(proton)
p1 : 4000
p2 : 4000

Run parameter: Mh
Run begin : 90
Run step size: 10
Run n steps : 18
Number of events (per run step): 1
Filename: visible6
NTuple: False
Cleanup: False
Parallelization method: local
Max number of nodes: 8
Max number of processes per node: 1
sleep time : 3
nice level : 19
nSess_1 : 10
nCalls_1 : 100000
nSess_2 : 10
nCalls_2 : 100000

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Alexander Belyaev (alexander.belyaev) said :
#4

Can you specify, please
details of the difference you are talking about?
Please send details to <email address hidden>
-- plots etc
Thanks
Sasha

Revision history for this message
Nurhan Karahan (ckarahan) said :
#5

Thank you. I sent them to your e-mail adress.

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Launchpad Janitor (janitor) said :
#6

This question was expired because it remained in the 'Open' state without activity for the last 15 days.

Revision history for this message
Alexander Belyaev (alexander.belyaev) said :
#7

Hello,
we have corrected CalcHEP, the new version 3.8.4 will appear on CalcHEP web page in few hours
The problem was in large error for bb->H process, the cross section for which was not quite stable.
You should get results you are expecting now.
In the previous version you could have neglected b-quarks in the initial state to get identical results since
contribution from b-quarks for SM Higgs production is negligible.
Regards,
Sasha

Revision history for this message
Nurhan Karahan (ckarahan) said :
#8

Thank you for your help. We will go on our studies with this new version.

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