Matrix Element Generators
CalcHEP is a package for automatic calculations of elementary particle decay and collision properties in the lowest order of perturbation theory (the tree approximation). The main idea prescribed into CalcHEP is to make available passing on from the Lagrangian to the final distributions effectively with a high level of automation. CalcHEP is a next development of the CompHEP package which was created by the author together with his colleagues in Skobeltsyn Institute of Nuclear Physics. Other packages created to solve a similar problem are FeynArts/FeynCalc, GRACE, HELAS, MADGRAPH, PHELAS, OMEGA.
MadGraph / MadEvent is a software that allows you to generate amplitudes and events for any process (with up to 9 external particles) in any model. Implemented models are the Standard Model, Higgs effective couplings, MSSM, the general Two Higgs doublet model, and several minor models, and there is an easy-to-use interface for implementing model extensions. In connection with MG/ME there is also a range of tools, including a Pythia and PGS (detector simulation) package, a Root event analysis package, plotting packages, interfaces to other generators and file converters. On these TWiki pages you can read about the packages, find documentation, see what we are working on and submit questions.
WHIZARD is a program system designed for the efficient calculation of multi-particle scattering cross sections and simulated event samples. Tree-level matrix elements are generated automatically for arbitrary partonic processes by using the Optimized Matrix Element Generator O'Mega. Matrix elements obtained by alternative methods (e.g., including loop corrections) may be interfaced as well. The program is able to calculate numerically stable signal and background cross sections and generate unweighted event samples with reasonable efficiency for processes with up to eight final-state particles; more particles are possible. For more particles, there is the option to generate processes as decay cascades including complete spin correlations. Currently, WHIZARD supports the Standard Model (optionally, with anomalous couplings), the MSSM, the NMSSM, Little Higgs models, Z' models, UED, and supports gravitinos and gravitons. Model extensions or completely different models can be added. There is also an interface to FeynRules.
Sherpa Not Installed
Simulation programs – also dubbed event generators – like Sherpa are indispensable work horses for current particle physics phenomenology and are (at) the interface between theory and experiment. Precision tests of the Standard Model and the quest for new physics in many cases relies on the confrontation of theoretical calculations with experimental findings. But such a procedure is far from being trivial because
many signals under investigation rely on non-trivial final states involving many particles;
experimentally, these final states have to fulfill some (detector) cuts, leading to considerable difficulties when integrating over the appropriate phase space;
the objects in the calculations are often quarks and gluons, whereas experimentally only hadrons, i.e. their bound states, are detected, which necessitates to model the quantitatively poorly understood (phase-)transition from the perturbative to the non-perturbative regime of QCD, the theory of strong interactions;
apart from the already mentioned hadronization also detector effects wash out signals.
CompHEP Not Installed
CompHEP is a package for automatic calculations of elementary particle decays and collision processes in the lowest order of perturbation theory (the tree level approximation). The main idea behind the program is to make calculations and data manipulations from Lagrangians to final distributions with a high level of automation. There are several packages created to solve the problem in a similar way: FeynArts/FeynCalc, GRACE, HELAS, MadGraph. CompHEP is a GUI computer system with context help. A user makes all manupulations by means of graphical menus.
Herwig++ Not Installed
Herwig++ is a completely new event generator, written in C++. It is built on the experience gained with the well-known event generator HERWIG. The aim is to provide a multi purpose event generator with similar or improved capabilities (like angular ordered parton evolution and the cluster hadronization model). At some point the ongoing development of the Fortran version will terminate and Herwig++ will take over.
Feynman Rule Generators
The LanHEP program for Feynman rules generation in momentum representation is presented. It reads the Lagrangian written in the compact form close to one used in publications. It means that Lagrangian terms can be written with summation over indices of broken symmetries and using special symbols for complicated expressions, such as covariant derivative and strength tensor for gauge fields. The output is Feynman rules in terms of physical fields and independent parameters. This output can be written in LaTeX format and in the form of CompHEP model files, which allows one to start calculations of processes in the new physical model. Although this job is rather straightforward and can be done manually, it requires careful calculations and in the modern theories with many particles and vertices can lead to errors and misprints. The program allows one to introduce into CompHEP new gauge theories as well as various anomalous terms.
FeynRules is a Mathematica® package that allows the calculation of Feynman rules in momentum space for any QFT physics model. The user needs to provide FeynRules with the minimal information required to describe the new model, contained in the so-called model-file. This information is then used to calculate the set of Feynman rules associated with the Lagrangian. The Feynman rules calculated by the code can then be used to implement the new physics model into other existing tools, such as MC generators. This is done via a set of interfaces which are developed together and maintained by the corresponding MC authors.
SARAH is a Mathematica package for building and analyzing supersymmetric models. SARAH just needs the gauge structure, particle content and superpotential to produce all information about the gauge eigenstates of a model. Breaking of gauge symmetries and mixings of particles can easily be added. Also the gauge fixing terms can be specified, and the corresponding ghost interactions are calculated automatically. SARAH can write all information about the model in LaTeX, or create a model file for FeynArts and CalcHep/CompHep, which can also be used for dark matter studies using MicrOmegas. In addition, also analytical results for the one and two loop renormalization group equations for for the parameters of the superpotential, the gauge couplings and the soft breaking parameters can be calculated. Also functions for an automatic calculation for the one loop corrections to self energies and the tadpoles are included. The intention by the development of SARAH was to make it very flexible: there is a big freedom for the matter and gauge sector you can handle. The work with SARAH should be easy: every information SARAH needs are specified in an easy to modify model file. Nevertheless, SARAH is also fast: a existing model can be changed within minutes, and the needed time for doing all necessary calculations and writing a model file is normally less than 10 minutes.