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CompHEP Automatic Computations from Lagrangians to Events

Fyzika za Štandardným modelom klope na dvere Svit, 9.-16.9. 2007. CompHEP Automatic Computations from Lagrangians to Events. Ivan Melo University of Zilina. CompHEP. A good tool for learning particle physics A good tool for research.

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CompHEP Automatic Computations from Lagrangians to Events

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  1. Fyzika za Štandardným modelom klope na dvere Svit, 9.-16.9. 2007 CompHEPAutomatic Computations from Lagrangians to Events Ivan Melo University of Zilina

  2. CompHEP • A good tool for learning particle physics • A good tool for research

  3. CompHEP, GRACE, MadGraph,AlpGen, O’Mega, WHIZARD, Amegic, … PYTHIA, HERWIG Theory Experiment ATLFAST Root ATLAS

  4. Useful features of CompHEP • Tool for calculating cross-sections and widths at tree-level starting from Lagrangian • Event generation plus CompHEP – PYTHIA and CompHEP – HERWIG interface • Up to 7 particles in final state • Built-in models: QED, effective 4-fermion, SM, MSSM, SUGRA, GMSB • With LanHEP one can add his/her own model • Simplicity LEP1 2 particles LEP2 4 LHC, ILC 5,6,8

  5. CompHEP limitations • No loop diagrams • Computation of squared amplitudes time-consuming for large number of FD • No polarized (helicity) cross-sections • No hadronization of quarks and gluons

  6. CompHEP Collaboration E. Boos, V. Bunichev, M. Dubinin, L. Dudko, V. Edneral, V. Ilyin, A. Kryuokov, V. Savrin, A. Semenov, A. Sherstnev Lomonosov Moscow State University CompHEP home page: http://comphep.sinp.msu.ru

  7. Beyond the SM with CompHEP CompHEP Collaboration

  8. Beyond the SM with CompHEPthe list of topics based on ~ 1000 theory papers quoting CompHEP CompHEP Collaboration

  9. Published experimental analyses quoting CompHEP CompHEP Collaboration

  10. Learning particle physics with CompHEP • γ + e-γ + e- (QED) • e+ + e- μ+μ- (SM scattering, e+e- collider) • H 2 * x (SM decay) • pp ttH +X tt bb + X (pp collider)

  11. γ + e-γ + e- (Compton scattering) (α=1/137) Thomson Klein-Nishina limit x << 1 (nonrelat.) Thomson scattering x >> 1 (relat.) Klein-Nishina limit

  12. e+ + e- μ+μ- σCompHEP= 2.0899 nb σLEP=1.9993+- 0.0026 nb

  13. e+ + e- μ+μ- CompHEP Tevatron LEP = 0.01627

  14. Higgs decay, H 2*x

  15. pp ttH +X tt bb + X Proton structure functions fi(x,q2) u u p d t g b H g g b t u u p d

  16. pp ttH +X tt bb + X Signal gg ttH σ = 0.729 pb uu ttH σ = 0.075 pb dd ttH σ = 0.045 pb Background gg ttgg σ = 400 pb gg ttbb σ = 6 pb

  17. gg -> ttbb (regularization and gauge invariant set) • 131 diagrams: choose diagrams without A,Z, W+,W- • 59 left : keep just 8 with H->bb • Run without regularization • Run with regularization

  18. Research with CompHEP • Add your own model with OneHEP • Send events to PYTHIA or HERWIG

  19. Future developments • Loops • Polarized cross-sections • Grid and new algorithm

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