Problem in hGG/AA

Asked by Taeyoung Kim

Hello

I installed CalcHEP last week for checking cross sections on

the results of <Handbook of LHC Higgs cross sections: 3.Higgs Properties>.

Then I tried the process G,G -> le,le,n,n in 8TeV with multiparticle states

le = e,E,m,M
n = ne,Ne,nm,Nm

and

Exclude diagrams with Z,m,M

and

Mh=200

in SM(CKM=1 with hGG/AA) model.

My problem is that it gave me strange results.

It's near 5pb in the paper, but I got only 160fb by using CalcHEP.

I'm just a beginner so I could not find my mistake.

Do you have any advice for this situation?

Thank you for reading this.

Taeyoung

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Alexander Belyaev
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Alexander Belyaev (alexander.belyaev) said :
#1

Dear Taeyoung,

the
<Handbook of LHC Higgs cross sections: 3.Higgs Properties>
quotes gg->H production about 5pb for 7 TeV
(you did not specify energy etc though !)
(Table B.69: SM Higgs-boson production cross sections at √s = 7 TeV: light Higgs boson.
page 360)

while CalcHEP gives you
G,G -> le,le,n,n

cross section
which takes into account branching ratios of Higgs decay to WW and ZZ
times Br of WW and ZZ decay to le,le,n,n

that is why numbers are different.

Looks like you are comparing apples and oranges

Regards,
   Alexander

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Taeyoung Kim (gcnb87) said :
#2

Dear Alexander,

Sorry, my question was not accurate.

I'm running about 8TeV,

and as you said I calculated Br of h -> WW times WW->le,le,n,n that

B(h->WW) = 0.7
B(W->le,n) = 0.255

with ggF 7.081 pb.

but the result is stiil too big (1250fb) comparing my result 160fb.

Did I do something wrong?

thank you for your quick response.

Taeyoung

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Alexander Belyaev (alexander.belyaev) said :
#3

Dear Taeyoung,

to check your result, I need your batch file.
You can send it to me at <email address hidden>

Regards,
      Alexander

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Alexander Belyaev (alexander.belyaev) said :
#4

Hi again,

my batch

Model: SM(CKM=1 with hGG/AA)
Process: p,p->h
Decay: h->le,n,le,n
Composite: p=u,U,d,D,G
Composite: le=e,E,m,M
Composite: n=ne,Ne,nm,Nm

pdf1: cteq6l (proton)
pdf2: cteq6l (proton)

p1: 8000
p2: 8000
Parameter: Mh=200

Number of Events: 10
Max number of cpus: 8

gives ~ 670 fb which is reasonable number for the tree-level result,
since NLO+NNLO adds up another about 100% for the Higgs production

Regards,
       Alexander

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Taeyoung Kim (gcnb87) said :
#5

I've tried now. but doesn't 8TeV mean each protons have 4 TeV energy?

By using your batch code with

p1:4000
p2:4000

gave me the same result. (160fb)

am I missing something?

always thank you !

Taeyoung

Revision history for this message
Alexander Pukhov (pukhov) said :
#6

hGG vertex in CalcHEP is written with NNNLO precision to describe Higgs decay. Definitely it should not work nice for production. As usual factor 2 difference is expected. In the same time I have to note that adding processes with jet emission one can get a reasonable result even with hGG implemented in CalcHEP.

According to 1503.06056 we have for sqrt(s)=8000 and 14000 GeV cross sections for Higgs production
18pb and 49 pb correspondingly. CaclHEP result for GG->h are 10pb and 30pb.

I add to GG->h processes processes with jet radiation
   p*,p* -> h,p*
and set pt limit for jets Mh/4. Qren=Mh/4 Qfact=M12.
These processes give me addition 5.7 and 19.4 pb. In this way I get results close to NNNLO calculations(1503.06056)
15.7 and 49.

I guess this trick should work for Mh=200. Let me know if I am wrong.

Of course, there is an ambiguity in choice of Tmin. But this value looks more or less reasonable. But we need something like that to reproduce NNNLO result for Higgs production.

A think subsequent Higgs decay is treated by CalcHEP correctly.

Best
    Alexander Pukhov

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Best Alexander Belyaev (alexander.belyaev) said :
#7

Yes,
I made a typo:
indeed the input should be

p1: 4000
p2: 4000

which gives
G,G->h 4pb from CalcHEP
and
GG->h->le,n,le,n

is equal to 4000fb*0.7*(2/9)^2 ~ 140 fb

-- your estimation of Br was not correct
since BOTH W's decay letponically

So, you results are OK

Alexander

Revision history for this message
Taeyoung Kim (gcnb87) said :
#8

Thanks Alexander Belyaev, that solved my question.

Revision history for this message
Taeyoung Kim (gcnb87) said :
#9

Thank you both for answering my question.

I understand my faults now and got a lot of CalcHEP.

Let me try jet radiation.

thank you.

Taeyoung