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History and personal contributions

The CompHEP project was founded in 1989 by the group of physicists and programmers of D.V. Skobeltsyn Institute of Nuclear Physics of Moscow State University. The project was initiated by Edward Boos, Viacheslav Ilyin and Victor Savrin. The primary formulation of physical problems for the project was done by E. Boos, Mikhail Dubinin, and Dmitri Slavnov. The first software working group was organized and managed by V. Ilyin.

The main author of the CompHEP software is Alexander Pukhov. He has developed almost all algorithms and data-representation structures of the package. Namely, the structure of physical model database, the algorithm for generation of Feynman diagrams, the algorithm for evaluation of squared matrix elements, the structure of output codes for different programming languages, the algorithm for optimization of numerical codes, the algorithm for phase-space integration with smoothing of propagator peaks. He also has created the specialized symbolic manipulation package for CompHEP.

The first version of the package appeared in 1989 [8,9]. It was written in the Turbo Pascal programming language for the MS-DOS operation system. The program produced a code for calculation of squared diagrams, written in the Reduce symbolic manipulation language. Routines for evaluation of the color factors were written by Alexander Kryukov. The Reduce code-generation routines were written by Alexander Taranov and A. Pukhov.

The authors of CompHEP were being lead by an idea to create a user friendly software. So they paid a special attention to the interface and data-representation facilities. The general part of graphical interface was designed by A. Pukhov. The routines for graphic representation of diagrams were written by Victor Edneral. The context-sensitive help facility was designed by Sergey Shichanin. The program for the CompHEP database table manipulation was done by A. Kryukov. Later on the plot drawing and L^ATEX output were designed by V. Edneral, A. Pukhov and S. Shichanin.

The CompHEP symbolic answers were compared by Mikhail Dubinin with a large number of known symbolic expressions for differential and integral cross sections [20]. Starting from this point the physicists of CompHEP group E. Boos, M. Dubinin, and V. Ilyin applied CompHEP for studying new physics signals and relevant backgrounds.

In 1991 CompHEP got the built-in symbolic manipulation package created by A. Pukhov and the Fortran code output written by A. Pukhov and S. Shichanin [10].

In 1992 Andrei Davydychev proposed to use the t'Hooft-Feynman gauge for evaluation of squared diagrams. This idea was realized by A. Pukhov. It has opened the real possibility to calculate any 2 -> 4 process with the help of the CompHEP package. In the same year V. Ilyin and S. Shichanin designed a Fortran program of phase-space integration for 2 -> 3 processes and A. Pukhov developed the numerical interpreter for 2 -> 2 processes. These achievements were announced in [10].

The numerical results by CompHEP for a large set of processes were compared with the GRACE package [21]. E. Boos, M .Dubinin, V .Ilyin and S .Shichanin performed some other cross-checks of the CompHEP package. Later on A. Belyaev, E. Boos and L. Dudko compared CompHEP with the FNAL program VECBOS [22] and extensive cross-checks of numerical results for $e^+,e^- \to 4\quad fermions$ set of processes have been performed by M. Dubinin [23].

In 1993 the symbolic part of CompHEP was rewritten in the C programming language by V. Edneral [14]. The realization of the Turbo Pascal graphic routines by means of X11 tools was done by Andrey Semenov [15]. It has opened the way to create the version for UNIX workstations [14,11,7].

The main problem remaining in this version was the phase-space integration. CompHEP created the Fortran code for squared matrix elements with a high level of automation. Generally the matrix elements have a lot of singularities caused by the propagators of virtual particles. In order to succeed in the Monte Carlo phase-space integration of singular matrix elements the user was forced every time to modify the program of phase-space parameterization.

For automation of this operation step A. Pukhov proposed a general approach to the generation of multi-particle kinematics and to the regularization of matrix elements. In 1995-96 this scheme was realized by A. Pukhov, Dmitri Kovalenko and V. Ilyin [12,13,19]. At the same time V. Ilyin wrote new Fortran interface programs like menus and together with A. Kryukov embedded the parton structure functions in CompHEP. Later on the structure-function package was improved by A. Pukhov to include the regularization of integration over Feynman parameters. As a result we get a version which provides the user with a possibility of automatic evaluation starting from the input of Lagrangian and finishing with distributions in physical parameters. The corresponding service for a histogram filling also was done by A. Pukhov. The list of needed distributions was compiled by E. Boos.

During this work it was realized that the Fortran programming language is not convenient for the future development of the numerical part of CompHEP. In 1997 the C code output for the numerical calculation was designed and the Fortran program for the numerical evaluation was rewritten in C as well. This work was done by A. Pukhov. In the same year A. Kryukov imported CompHEP onto the MS-Windows95/NT platform.

The development of CompHEP was being under a continuous pressure of physicists' requests. The works of E. Boos, M. Dubinin, V. Ilyin, V. Savrin and S. Shichanin, who first used CompHEP for physical calculations, at the same time were defining a direction of the package development. They also contribute to and are responsible for debugging the package.

It must be especially noted the role of E. Boos and V. Ilyin in the popularization of CompHEP for the scientific community.

The manual was written by A. Pukhov, V. Savrin, and S. Shichanin.

There is a possibility of automatic conversion of the Lagrangian written in the compact form in the coordinate space into the CompHEP table format. It can be performed by means of the LanHEP program written by A. Semenov [16]. The input is expressed in terms of complex objects, such as a covariant derivative and a gauge field tensor.

The LanHEP program was used [17] to generate CompHEP model files for the Minimal Supersymmetric Model. Another result produced by LanHEP is the realization the general two-Higgs-doublet model [18] The CompHEP WWW page contains references to the LanHEP code and to the MSSM Lagrangian model files.