CompHEP Automatic Computations from Lagrangians to Events Urýchľovačová fyzika 3 CompHEP Automatic Computations from Lagrangians to Events Ivan Melo

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

Cross section calculation 3 4 5 1 2 7 6 8 amplitúda počet možných stavov, fázový priestor zachovanie energie a hybnosti

+ ... + e- e+  e- e+ Dynamika procesu je skrytá v amplitúde M g e- e+ + + ... M = M1(α) + M2(α2) + ... ak  < 1 potom M1(α) > M2(α2) > ... v prípade elektrónov a fotónov:  = 1/137 Urýchľovačová fyzika 5 M.Gintner

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

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: http://comphep.sinp.msu.ru

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

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

Higgs decay, H 2*x decay width lifetime

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

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

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