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We present a new version of the CompHEP program package, version 4.5. We describe new options and techniques implemented in the version: interfaces to ROOT and HERWIG, parallel calculations, generation of the XML-based header in event files (HepML), full implementation of the Les Houches agreements (LHA I, SUSY LHA, LHA PDF, Les Houches Event format), cascade matching for intermediate scalar resonances, etc.

TESLA Technical Design Report, Part VI, Chapter 1: The Photon Collider at TESLA, Comment: 102 pages, 41 figures, editor: V. Telnov

This Report documents the results obtained by the Working Group on Quantum ChromoDynamics and the Standard Model for the Workshop ``Physics at TeV Colliders'', Les Houches, France, 21 May - 1 June 2001. The account of uncertainties in Parton Distribution Functions is reviewed. Progresses in the description of multiparton final states at Next-to-Leading Order and the extension of calculations for precision QCD observables beyond this order are summarized. Various issues concerning the relevance of resummation for observables at TeV colliders is examined. Improvements to algorithms of jet reconstruction are discussed and predictions for diphoton and photon pi-zero production at the LHC are made for kinematic variables of interest regarding searches for a Higgs boson decaying into two photons. Finally, several improvements implemented in Monte-Carlo event generators are documented. This Report documents the results obtained by the Working Group on Quantum ChromoDynamics and the Standard Model for the Workshop ``Physics at TeV Colliders'', Les Houches, France, 21 May - 1 June 2001. The account of uncertainties in Parton Distribution Functions is reviewed. Progresses in the description of multiparton final states at Next-to-Leading Order and the extension of calculations for precision QCD observables beyond this order are summarized. Various issues concerning the relevance of resummation for observables at TeV colliders is examined. Improvements to algorithms of jet reconstruction are discussed and predictions for diphoton and photon pi-zero production at the LHC are made for kinematic variables of interest regarding searches for a Higgs boson decaying into two photons. Finally, several improvements implemented in Monte-Carlo event generators are documented. This Report documents the results obtained by the Working Group on Quantum ChromoDynamics and the Standard Model for the Workshop ``Physics at TeV Colliders'', Les Houches, France, 21 May - 1 June 2001. The account of uncertainties in Parton Distribution Functions is reviewed. Progresses in the description of multiparton final states at Next-to-Leading Order and the extension of calculations for precision QCD observables beyond this order are summarized. Various issues concerning the relevance of resummation for observables at TeV colliders is examined. Improvements to algorithms of jet reconstruction are discussed and predictions for diphoton and photon pi-zero production at the LHC are made for kinematic variables of interest regarding searches for a Higgs boson decaying into two photons. Finally, several improvements implemented in Monte-Carlo event generators are documented.

The TESLA Technical Design Report Part III: Physics at an e+e- Linear Collider, Comment: 192 pages, 131 figures. Some figures have reduced quality. Full quality figures can be obtained from http://tesla.desy.de/tdr. Editors - R.-D. Heuer, D.J. Miller, F. Richard, P.M. Zerwas

The existence of extra chiral generations with all fermions heavier than $M_Z$ is strongly disfavored by the precision electroweak data. The exclusion of one additional generation of heavy fermions in SUSY extension of Standard Model is less forbidden if chargino and neutralino have low degenerate masses with $\Delta m \simeq 1$ GeV. However the data are fitted nicely even by a few extra generations, if one allows neutral leptons to have masses close to 50 GeV. Such heavy neutrino can be searched in the reaction $e^+ e^- \to N\bar{N}\gamma$ at LEP-200 with total final luminosity of $2600 pb^{-1}$., Comment: 5 pages, 6 figures, Proceedings ICHEP2000 Osaka conference

The results obtained by the Working Group on Supersymmetry at the 1999 Les Houches Workshop on Collider Physics are summarized. Separate chapters treat "general" supersymmetry, R-parity violation, gauge mediated supersymmetry breaking, and anomaly mediated supersymmetry breaking., Comment: LaTeX, 110 pages with numerous .ps and .eps files. proc.tex is main tex file

The Les Houches Workshop on Physics at TeV Colliders took place from June 8-18, 1999. One of the three working groups at Les Houches concentrated on QCD issues, both at the Tevatron Collider and at the LHC. Besides the interest in QCD in its own right, QCD dynamics plays an important role in the production mechanisms for any new physics process that might be observed at either collider, as well as any processes that may form backgrounds to the new physics. This writeup serves both as a pedagogical overview of QCD as well as an update on the current status of the field., Comment: 179 pages, 65 figures

In some supersymmetric extensions of the Standard Model fairly light superpartner of t-quark is predicted, which may form bound states - stoponiums. We estimate potentials of TESLA linear collider in search for stoponium, considering the basic e+e- option and the gamma-gamma option (Photon Linear Collider - PLC). It is found that PLC could be the best machine for discovery of these new narrow strong resonances. It can produce thousands stoponiums per 100 fb$^-1$ integrated luminosity in the high energy peak. In the case of scenarios when stoponium decays mainly into gluons the signal/background ratio is about 1/4. The channel S->hh into two lightest Higgs bosons could be also seen with high significance. Thus, several weeks run is sufficient for the stoponium discovery, if its mass is approximately known (e.g. from observation of direct stops production at LHC). Then, in MSSM scenarios with dominant S->hh decay PLC shows excellent possibilities to discover bound state of stops, practically immediately after beginning of operating. The e+e- option also has some prospects to observe stoponium but only in the case of scenarios with dominant decay into two lightest Higgs bosons, with tens of events per 100 $fb^{-1}$. Interesting possibility appears in the case when the resonance is seated on 0.1% width luminosity peak - one could resolve the stoponium exited states., Standard LaTeX, 15 pages, 2 figures, uses elsart.cls. Talk at the International Workshop on High Energy Photon Colliders (GG2000, DESY, Hamburg, June 14-17, 2000), to be published in Nucl. Instr. and Meth. A. Numbers for e+e- production are changed

CompHEP 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 the CompHEP is to make available passing on from the Lagrangian to the final distributions effectively with a high level of automation., 126 pages (standard LaTeX code), 14 figures, misprints improved

Report of the Higgs working group for the Workshop "Physics at TeV Colliders", Les Houches, France 8-18 June 1999. It contains 6 separate sections: 1. Measuring Higgs boson couplings at the LHC. 2. Higgs boson production at hadron colliders at NLO. 3. Signatures of Heavy Charged Higgs Bosons at the LHC. 4. Light stop effects and Higgs boson searches at the LHC. 5. Double Higgs production at TeV Colliders in the MSSM. 6. Programs and Tools for Higgs Bosons., Latex, 100 pages, style files included, also available at http://www.lpm.univ-montp2.fr:7082/~djouadi/houches/houches99.html

The bounds on the anomalous contributions to the ggh and zgh vertices that can be obtained via the process eg->eh are discussed through a model independent analysis based on SU(2) X U(1) invariant operators of dim=6. A light Higgs boson with m_H ~ 120 GeV and center-of-mass energies of \sqrt{S}=500 GeV and \sqrt{S}=1500 GeV are assumed. The process eg->eh is shown to provide an excellent way to strongly constraint both the CP-even and CP-odd anomalous contributions in the ggH and ZgH couplings., 8 pages. To appear in the DESY report on "Physics Studies for a Future Linear Collider", DESY 123F

We discuss the SM Higgs discovery potential of LHC in the reaction $pp\to H+ jet\to����+jet$ when the jet is observed at sufficiently high $E_t$ to be reliably identified. We conclude that this channel gives promising discovery possibilities for the Higgs boson mass range 100-140 GeV, during LHC operation at a low luminosity. With 30 fb$^{-1}$ of accumulated data and for $M_H=120$ GeV about 100 signal events could be observed with the number of background events larger by a factor of 2 only, showing a signal significance $S/\sqrt{B}\sim 7$. We use the difference of distributions in the partonic subprocess energy $\sqrt{\hat s}$ for the signal and background for a better separation of the signal., 15 pages including 6 figures, LaTeX, use epsfig.sty. To appear in Phys.Lett.B. In this replacement minor LaTeX improvements are made

The report summarizes the results of the activities of the Working Group on Event Generators for WW Physics at CERN during 1995., Comment: 99 Latex, including 30 figures, 24 tables. The report is part of: G.Altarelli,T.Sjostrand and F.Zwirner (eds), Physics at LEP2 CERN 96-01

We describe the physics potential of $e^+e^-$ linear colliders in this report. These machines are planned to operate in the first phase at a center-of --mass energy of 500 GeV, before being scaled up to about 1 TeV. In the second phase of the operation, a final energy of about 2 TeV is expected. The machines will allow us to perform precision tests of the heavy particles in the Standard Model, the top quark and the electroweak bosons. They are ideal facilities for exploring the properties of Higgs particles, in particular in the intermediate mass range. New vector bosons and novel matter particles in extended gauge theories can be searched for and studied thoroughly. The machines provide unique opportunities for the discovery of particles in supersymmetric extensions of the Standard Model, the spectrum of Higgs particles, the supersymmetric partners of the electroweak gauge and Higgs bosons, and of the matter particles. High precision analyses of their properties and interactions will allow for extrapolations to energy scales close to the Planck scale where gravity becomes significant. In alternative scenarios, like compositeness models, novel matter particles and interactions can be discovered and investigated in the energy range above the existing colliders up to the TeV scale. Whatever scenario is realized in Nature, the discovery potential of $e^+e^-$ linear colliders and the high-precision with which the properties of particles and their interactions can be analysed, define an exciting physics programme complementary to hadron machines., 103 pages, Latex

One-loop production of a Higgs boson in electro-photon collisions at future accelerators is studied via the process (e gamma -> e H), for intermediate Higgs masses. Exact cross sections, including the possibility of longitudinally polarized initial beams, are presented. Confirming previous estimates made in the Weizs��cker-Williams approximation, they are found to be more than two orders of magnitude larger than the cross sections for the crossed process (e e-> gamma H), in the energy range $\sqrt{s}=(0.5-2)$ TeV. We show that, not only (e gamma -> e H) has a similar potential as the (gamma gamma -> H) process for testing the one-loop gamma-gamma-H vertex, but, by requiring a final electron tagged at large angle in (e gamma -> e H), the (H e) production provides an excellent way of testing the Z-gamma-H vertex, too. Kinematical distributions for the (e gamma -> e H -> e bb) process with a tagged final electron are analyzed, and strategies for controlling the main irreducible background are found. Initial-state-radiation effects are checked to be within a few percent., 36 pages, 14 figures. Small differences with the published paper corrected

The CompHEP package was developed for calculations of decay and high energy collision processes with, correspondingly, up to 5 and 4 final particles in the lowest order (tree) approximation. The main idea put into CompHEP was to make available passing from the Lagrangian to final distributions efficiently with high level automation what is extremely needed in collider physics. The present talk describes a general structure of the CompHEP facilities and reports some physical results obtained with its help. The main purpose of the talk is to attract the attention of high energy physicists to this user-friendly package which is completely aimed at making easier their routine and tedious calculations in the TeV region., Comment: 18 pages, standard LaTeX code, uses epsf macros; 13 figures (uses 11 files in PS and EPS formats). Talk presented at the Xth Workshop on High Energy Physics and Quantum Field Theory (20-26 September 1995, Zvenigorod, Russia). The code of CompHEP package is available at http://theory.npi.msu.su/~pukhov/comphep.html

Higgs production in $e��$ collisions, through the one-loop reaction $e��\to eH$ at large $p_T$, can provide a precise determination of the $Z��H$ vertex., 2 pages (standard LaTeX code); Contribution to the Proceedings of the Int. Europhysics Conference on High Energy Physics (Jerusalem, 19-26 August 1997)

We discuss the SM Higgs discovery potential of the LHC in the channel pp->H+jet->gamma+gamma+jet when the jet is observed at sufficiently high Pt and a small rapidity to be reliably identified. We calculate all the signal subprocesses and the irreducible background with realistic kinematical cuts. The reducible QCD background is also estimated. We conclude that the channel gamma+gamma+jet can give about 120-200 signal events for Higgs mass MH=100-140 GeV at the integrated luminosity of 30 inverse fb. This signal rate should be compared with only 330-600 events for the irreducible background per two-photon invariant mass interval of 2 GeV. We estimate the QCD reducible background at the level of 20% of the irreducible one. Thus, one may hope that the Higgs boson can be discovered already during the LHC operation at a low luminosity. At a high luminosity the observation of several hundreds of high Pt Higgs bosons in this channel will be possible with significance higher than 15 for L=100 inverse fb., 21 pages (LaTeX code, epsf.sty), 2 tables, 9 figures; to appear in the Proceedings of XIIth International Workshop on High Energy Physics and Quantum Field Theory (QFTHEP-97), Samara, Russia, September 4-10, 1997

The one-loop process e,gamma->e,h for intermediate Higgs masses is considered. Exact cross sections for unpolarized and longitudinally polarized beams are computed and found to be more than two orders of magnitude larger than the rates for the crossed process e,e->gamma,h, in the energy range \sqrt{s}=(0.5-2) TeV. We show that, apart from being competitive with the gamma,gamma->H process for testing the one-loop gamma-gamma-H vertex, by requiring a final electron tagged at large angle the channel e,gamma->e,h provides an excellent way of testing the Z-gamma-H vertex., 11 pages, 8 figures. A gzipped complete postscript file is available at ftp://hpteo.roma1.infn.it/pub/preprints/mele/Rome1-1178.ps.gz To appear in the Report DESY 97-123E

We show that the Higgs production in $e��$ collisions, through the one-loop reaction $e��\to eH$ at large transverse momentum, can provide a precise determination of the $Z��H$ vertex. We concentrate on the analysis of signal rates vs background looking for strategies to improve the ratio $S/B$. Possible bounds on anomalous contributions to the $Z��H$ vertex are derived., 5 pages (standard LaTeX code); Talk given at "Beyond the Standard Model V" Conference, April 29 - May 4 1997, Balholm (Norway); to be published in the Proceedings

We study a possibility to measure the anomalous magnetic moment of vector leptoquarks in reactions with single leptoquark production associated with hard photon emission in ep collisions. For this purpose we propose to use the radiative amplitude zero effect. We find that an exact radiative zero in the angular distribution of the emitted photon is present only for pure Yang-Mills coupling of photons to leptoquarks. As a result the cross section is sensitive to the anomalous magnetic moment kappa of the leptoquark. This effect offers a possibility to measure kappa with rather high accuracy. For LEP+LHC we establish upper bounds in the plane leptoquark mass--anomalous magnetic moment., 7 pages of text (including one table and figure captions) in standard LATEX. Four figures in one PS file prepared by the script 'uufiles' (see comments at the head of the received file)

We have studied double Higgs production at future linear colliders while paying special attention to the option of high-energy and high-luminosity photon beams. The main purpose was to examine the feasibility of e+e-, e-gamma and gamma-gamma colliders in order to probe the anomalous triple Higgs coupling, which is crucial for understanding the Standard Model. We considered mainly the cases of light and intermediate Higgs bosons. Double Higgs production is almost background free, except in the MH=MZ mass range, which is discussed separately. It is shown that for a light Higgs boson the HHH coupling can be measured even at e+e- collider at 500 GeV. For a intermediate Higgs boson a collider in the TeV region is suitable for such an investigation. We have estimated the bounds on the anomalous HHH coupling, which can be experimentally established using future linear colliders., 14 pages of text (including Table and Figures captions and 1 Table) in standard LATEX code; 9 figures in one PS file, prepared by the script `uufiles' (see comment at the head of the received file)

Generic Fortran common blocks are presented for use by High Energy Physics event generators for the transfer of event configurations from parton level generators to showering and hadronization event generators., Comment: Physics at TeV Colliders II Workshop, Les Houches, France, May 2001 14 pages, 6 figures

At present time when a new generation of TeV colliders are beginning to operate one needs to calculate cross-sections for a great number of various reactions. Such calculations are united in the framework of the collider physical program, providing definite predictions how to detect the signatures of the new physics and separate them from the background. The CompHEP package was created for calculation of decay and high energy collision processes of elementary particles in the lowest order (tree) approximation. The main idea put into the CompHEP was to make available passing from the lagrangian to the final distributions effectively with the high level of automatization what is extremely needed in collider physics.