Publications (32)48.61 Total impact
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ABSTRACT: In the paper the existence of new quasistationary levels in the relativistic Coulomb problem is predicted and their positions are calculated on the basis of the numerical solution of the quasipotential equation. The results obtained are used for interpretation of the narrow electronpositron resonances revealed in heavy ions collisions and of the diproton resonances observed in neutronproton interactions. The close relationship of the observed states with the von NeumannWigner levels embedded in the continuum, is indicated.  [Show abstract] [Hide abstract]
ABSTRACT: CompHEP, as a partonic event generator, and PYTHIA, as a generator of final states of detectable objects, are interfaced. Thus, integrated tool is proposed for simulation of (almost) arbitrary collision processes at the level of detectable particles. Exact (multiparticle) matrix elements, convolution with structure functions, decays, partons hadronization and (optionally) parton shower evolution are basic stages of calculations. The PEVLIB library of event generators for LHC processes is described. Comment: Standard LaTeX, 4 pages. To appear in the proceedings of the Seventh International Workshop on Advanced Computing and Analysis Technics in Physics Research (ACAT2000, Fermilab, October 1620, 2000) 
Article: Event Generators For WW Physics
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ABSTRACT: this report we shall deal with the practical implementation of the theoretical results described in the WW study group report. There, many important results and formulae have been given which have to find their way into the analysis of the LEP2 data, in particular those dealing with the measurement of the W mass and couplings. It is our aim to describe the current state of the art of this implementation. The simplest detectable final states of relevance are those consisting of four fermions (when we disregard the complications arising from photon bremsstrahlung, gluon bremsstrahlung and hadronization effects), and consequently the phase space has seven dimensions (eight, if we also include the overall azimuthal distribution of events around the beam axis  this distribution, however, is trivial as long as no transversely polarized beams are considered). Obviously, the sets of diagrams that contribute to a given final state is also quite complicated. Below, we shall present a classification of the various sets of diagrams that we have found useful in discussing and comparing results. When we also take into account the complicated peaking structures resulting from the many different Feynman diagrams, it becomes clear that the only way in which we can arrive at experimentally meaningful results in which all cuts can be accommodated is that of Monte Carlo simulation of the full event. This feature is even more pronounced than at LEP1, where the important events have a twofermion final state, with only one relevant angular variable, and little peaking structure at given energy. There are, of course, processes such as e  [Show abstract] [Hide abstract]
ABSTRACT: 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. Comment: 126 pages (standard LaTeX code), 14 figures, misprints improved 
Article: Physics with e+ e linear colliders
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ABSTRACT: The physics potential of e(+) e() linear colliders is summarized in this report. These machines are planned to operate in the first phase at a centerofmass 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, i.e. compositeness models, novel matter particles and interactions can be discovered and investigated in the energy range above the existing colliders lip 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 analyzed, define an exciting physics program complementary to hadron machines. 
Article: Event Generators for WW Physics
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ABSTRACT: The report summarizes the results of the activities of the Working Group on Event Generators for WW Physics at CERN during 1995. 
Article: The Standard Model Higgs : Discovery Potentials and Branching Fraction Measurements at the NLC
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ABSTRACT: We discuss discovery potentials for a 140 GeV Standard Model Higgs boson produced in e+e collisions at 360 GeV, including all potential irreducible and reducible background contributions. In the second part of the study, we estimate the uncertainties expected for the branching fractions of the Higgs into bbbar, tau+tau, WW* and into ccbar+gg including a realistic error estimation of the inclusive bremsstrahlung Higgs production cross section. 
Article: Physical results by means of CompHEP
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ABSTRACT: 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 userfriendly package which is completely aimed at making easier their routine and tedious calculations in the TeV region.  [Show abstract] [Hide abstract]
ABSTRACT: The complete treelevel cross sections for the re action e+e ! etb are computed for top masses of 160 to 200 GeV at centerofmass energies between 0.2 and 2.0 TeV using the packages CompHEP and GRACE. It is demon strated that t ¯ t pair production dominates around p s = 0.5 TeV, whereas soft photon tchannel exchange contributions grow with increasing energy such that above 1.5 TeV it dom inates. Detailed cross section considerations close to the t ¯ t threshold reveals some peculiar properties. It is shown that a precise top quark mass determination is not significantly hampered by the existence of nont ¯ t diagrams. With de sirable assumptions on linear collider luminosities the CKM matrix element jVtbj might be measured best at or close to p s =2T eV. 
Conference Paper: Higgs Physics at LEP2
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ABSTRACT: In this report we review the prospects for Higgs physics at LEP2. The theoretical aspects and the phenomenology of Higgs particles are discussed within the Standard Model (SM) and the Minimal Supersymmetric Standard Model (MSSM). The experimental search techniques are described and the discovery limits for Higgs bosons in the LEP2 energy range are summarized. In addition, opportunities of detecting Higgs particles in nonminimal extensions of the SM and the MSSM are investigated.  [Show abstract] [Hide abstract]
ABSTRACT: Review of Monte Carlo event generators for signals of new particles at LEP2. The areas covered include SUSY, HIGGS and Leptoquarks. 
Article: Top quark production in the reaction$e^+e^ \longrightarrow e\nu tb$ at linear collider energies
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ABSTRACT: The complete treelevel cross sections for the reaction e +e− →e?tb are computed for top masses of 160 to 200 GeV at centerofmass energies between 0.2 and 2.0 TeV using the packages CompHEP and GRACE. It is demonstrated that tt̅ pair production dominates around $sqrt s=0.5$ TeV, whereas soft photon tchannel exchange contributions grow with increasing energy such that above 1.5 TeV it dominates. Detailed cross section considerations close to the tt̅ threshold reveals some peculiar properties. It is shown that a precise top quark mass determination is not significantly hampered by the existence of nontt̅ diagrams. With desirable assumptions on linear collider luminosities the CKM matrix element  V tb  might be measured best at or close to $sqrt s=2$ TeV.  [Show abstract] [Hide abstract]
ABSTRACT: A complete treelevel Standard Model calculation of the reaction\(e^ + e^  \to b\bar b + 2\) jets in the energy range of LEPII and the Nexte +e− Linear Collider is presented. The 2jet system represents either aq \(\bar q\) pair or two gluons. The matrix elements were calculated by means of the package CompHEP, and phase space integration and event generation were carried out with the computer programs BASES/SPRING. Cross sections of the Higgs boson, the total background and important subsets of background are studied as functions of the c.m.s. energy and the Higgs mass, taking into account possible interferences. Various event distributions calculated for realistic integrated luminosities indicate encouraging prospects regarding the extraction of the Higgs signal.  [Show abstract] [Hide abstract]
ABSTRACT: A complete treelevel calculation of the reaction e+ e > ν bar {ν }bbar {b} in the electroweak standard theory for the energy range of LEP200 and the Next Linear Collider is presented. The matrix elements were calculated by means of the package CompHEP, and phase space integration and event generation were carried out with the computer programs BASES/SPRING. Cross sections for the ν bar {ν }bbar {b} final state, the rate for Higgs production and for different background contributions are studied as a function of the cms energy and the Higgs mass in the range from 80 to 140 GeV. At LEP200 energies, the Higgs bremsstrahlung reaction and the twobody process e+e→ZZ are dominant while near 500 GeV the Higgs fusion and twotothree body background processes govern the ν bar {ν }bbar {b} final state. Interference patterns were searched for and found to be negligible except for √ {s} < MH + MZ, where interferences are found to be of comparable strength with the Higgs signal diagrams. Some cancellations between different background diagrams are observed which are expected within the Standard Model. Missing transverse momentum and visible energy distributions for the ν bar {ν }bbar {b} final state indicate some further possibilities of removing background for Higgs searches. A suggestion for an approximate treatment of the reaction e+ e > ν bar {ν }b bar {b} is presented so that much computer time can be saved in Monte Carlo simulations. 

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ABSTRACT: A complete treelevel calculation of the reactione^ + e^  to mu ^ + mu ^  bbar b in the electroweak standard theory for the energy range of LEP200 and the next linear collider is presented. The matrix elements have been calculated by employing the computer program CompHEP, the phase space integrals by the Monte Carlo integrator and event generator BASES/SPRING. The dependence of the 4fermion cross section on energy and the Higgs boson mass is studied in detail. Interference contributions between the various diagrams are found not to alter significantly the production and decay properties of the Higgs boson. It is shown that already the counting rate of the reactione^ + e^  to mu ^ + mu ^  bbar b at LEP200 can provide evidence for the existence of the Higgs boson.  [Show abstract] [Hide abstract]
ABSTRACT: Results of calculations of all treelevel Standard Model diagrams for the reaction $e^ + e^  \to e^ + e^  b\bar b$ in the energy range of LEPII and the Nexte +e − Linear Collider are presented. The complete matrix element was calculated by means of the software package CompHEP; phase space integration and event generation were carried out with the computer programs BASES/SPRING with additional regularizations necessary in order to handle singularities. The contributions of the dominating subsets of diagrams, the possible interference terms and their with results of previous calculations as well as with those derived from simple analytical approximations is demonstrated. Encouraging results are obtained regarding the extraction of the Higgs signal from the overwhelming background.  [Show abstract] [Hide abstract]
ABSTRACT: Ten threebody processes in e+e collisions for heavy particle productions such as Higgs, tquark, W± and Z0 are calculated by two independent computer codes for automatic calculation of Feynman amplitude. The results are in excellent agreement within statistical error of numerical integration (about 0.5%). This demonstrates that these systems are quite powerful for theoretical study for future e+e, e±gamma and gammagamma colliders. Numerical values of cross sections are summarized in tables and a figure. 
Publication Stats
588  Citations  
48.61  Total Impact Points  
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Institutions

19922011

Институт физики высоких энергий
Protvino, Moskovskaya, Russia


1995

Moscow State Forest University
Mytishi, Moskovskaya, Russia
