CompHEP Automatic Computations from Lagrangians to Events Ivan Melo University of Zilina Fyzika za Štandardným modelom klope na dvere Svit,

CompHEP A good tool for learning particle physics A good tool for research

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

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

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

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:

Beyond the SM with CompHEP CompHEP Collaboration

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

Published experimental analyses quoting CompHEP CompHEP Collaboration

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)

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

e + + e - μ + μ - σ CompHEP = nb σ LEP = nb

e + + e - μ + μ - TevatronLEP = CompHEP

Higgs decay, H 2*x

t H g g g t u u d u u d b b p p pp ttH +X tt bb + X Proton structure functions f i (x,q 2 )

pp ttH +X tt bb + X Signal gg ttH σ = pb uu ttH σ = pb dd ttH σ = pb Background gg ttgg σ = 400 pb gg ttbb σ = 6 pb

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

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

Future developments Loops Polarized cross-sections Grid and new algorithm