MadGraph5_aMC@NLO

Difference in cross section

Asked by Shubhani Jain

Hi

We are trying to generate samples for (gg > h2 > h1 h1 > bb~bb~), (pp> tt~ , (t> W+ b, W+ > jj), (t~ > W- b~ , W- > all all)), (pp > Zbb~, Z>bb~) , (pp>bb~bb~) processes. Our process involves:
1. for signal (gg > h2 > h1 h1 > bb~bb~) with m_h=125gev, m_H =700gev:
    generate gg>h2>h1h1 [QCD] as we use 2HDMII_nlo model
    decay h1 > bb~ in madspin
    parton level cut on pt_h1 of 350 gev
      cross section after MG5 and pythia8 run: 5.851571e-10 pb
 2. for (pp> tt~ , (t> W+ b, W+ > jj), (t~ > W- b~ , W- > all all)):
     generate pp>tt~
     decay t and t~ as described above in madspin
    parton level cut on pt_t of 300 gev
     cross section after MG5 and pythia8 run: 9.765800e+00 pb
3. for pp >Zbb~, Z>bb~:
    generate pp > Zbb~
    decay Z>bb~ in madspin
    parton level cut on Z of 300gev and on b of 250gev
     cross section after MG5 and pythia8 run: 1.057395e-03 pb
4. for pp>bb~bb~:
    generate pp>bb~bb~
    parton level cut on b of 150 gev
    cross section after MG5 and pythia8 run: 1.742935e-01 pb

This seems to give us lower cross-sections than expected. Is it due to our generation level cuts or madspin acting up?

Any help regarding this will be helpful.

Regards
Shubhani

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Olivier Mattelaer (olivier-mattelaer) said : 		#1

hi,

I can not comment on such question since I do not know what you expect.
But yes, MadSpin decreases the cross-section (due to the Branching ratio) and the cut are also reducing the cross-section by definition.

You can lower the cut to see the impact of the cut obviously.

Cheers,

Olivier

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