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High Energy Physics - Phenomenology (27)
Physics - Accelerator Physics (14)
Physics - Instrumentation and Detectors (4)
High Energy Physics - Experiment (4)

Publications Authored By S. Riemann

The use of polarized beams enhance the possibility of the precision measurements at the International Linear Collider (ILC). In order to preserve the degree of polarization during beam transport spin rotators are included in the current TDR ILC Lattice. In this report some advantages of using a combined spin rotator/spin flipper are discussed. Read More

High energy e+e- linear colliders are the next large scale project in particle physics. They need intense sources to achieve the required luminosity. In particular, the positron source must provide about 10E+14 positrons per second. Read More

Authors: Halina Abramowicz, Angel Abusleme, Konstatin Afanaciev, Gideon Alexander, Niloufar Alipour Tehrani, Oscar Alonso, Kristoffer K. Andersen, Samir Arfaoui, Csaba Balazs, Tim Barklow, Marco Battaglia, Mathieu Benoit, Burak Bilki, Jean-Jacques Blaising, Mark Boland, Marça Boronat, Ivanka Božović Jelisavčić, Philip Burrows, Maximilien Chefdeville, Roberto Contino, Dominik Dannheim, Marcel Demarteau, Marco Aurelio Diaz Gutierrez, Angel Diéguez, Jorge Duarte Campderros, Gerald Eigen, Konrad Elsener, Dan Feldman, Uli Felzmann, Mirosław Firlej, Elena Firu, Tomasz Fiutowski, Kurt Francis, Frank Gaede, Ignacio García García, Veta Ghenescu, Gian Giudice, Norman Graf, Christian Grefe, Christophe Grojean, Rick S. Gupta, Michael Hauschild, Helga Holmestad, Marek Idzik, Christian Joram, Sergey Kananov, Yannis Karyotakis, Martin Killenberg, Wolfgang Klempt, Sabine Kraml, Beata Krupa, Szymon Kulis, Tomáš Laštovička, Greg LeBlanc, Aharon Levy, Itamar Levy, Lucie Linssen, Angela Lucaci Timoce, Strahinja Lukić, Vladimir Makarenko, John Marshall, Victoria Martin, Rune E. Mikkelsen, Gordana Milutinović-Dumbelović, Akiya Miyamoto, Klaus Mönig, Gudrid Moortgat-Pick, Jakub Moroń, Astrid Münnich, Alina Neagu, Mila Pandurović, Duccio Pappadopulo, Bogdan Pawlik, Werner Porod, Stéphane Poss, Titi Preda, Roger Rassool, Ricardo Rattazzi, Sophie Redford, Jose Repond, Sabine Riemann, Aidan Robson, Philipp Roloff, Eduardo Ros, Jonatan Rosten, Alberto Ruiz-Jimeno, Heidi Rzehak, André Sailer, Dieter Schlatter, Daniel Schulte, Felix Sefkow, Katja Seidel, Nikolai Shumeiko, Eva Sicking, Frank Simon, Jacob Smith, Christian Soldner, Steinar Stapnes, Jan Strube, Taikan Suehara, Krzysztof Świentek, Marco Szalay, Tomohiko Tanabe, Michal Tesař, Andrea Thamm, Mark Thomson, Juan Trenado Garcia, Ulrik I. Uggerhøj, Erik van der Kraaij, Iván Vila, Eva Vilella, Miguel Angel Villarejo, Marcelo Alonso Vogel Gonzalez, Marcel Vos, Nigel Watson, Harry Weerts, James D. Wells, Lars Weuste, Tobias N. Wistisen, Kent Wootton, Lei Xia, Leszek Zawiejski, Ion-Sorin Zgura

This paper summarizes the physics potential of the CLIC high-energy e+e- linear collider. It provides input to the Snowmass 2013 process for the energy-frontier working groups on The Higgs Boson (HE1), Precision Study of Electroweak Interactions (HE2), Fully Understanding the Top Quark (HE3), as well as The Path Beyond the Standard Model -- New Particles, Forces, and Dimensions (HE4). It is accompanied by a paper describing the CLIC accelerator study, submitted to the Frontier Capabilities group of the Snowmass process. Read More

Affiliations: 1University of Oklahoma, Department of Physics and Astronomy, 2SLAC, 3KEK, 4TUHEP, 5Universität Wien, Theoretische Physik, 6University of Toyama, Department of Physics, 7DESY, 8Carleton University, Department of Physics, 9University of Oxford, Particle Physics Department, 10Cornell University, Laboratory for Elementary-Particle Physics, 11SLAC, 12LAL, 13DESY, 14DESY, 15APC, CNRS/IN2P3, 16CERN, 17University of California, Department of Physics and Astronomy, 18University of Texas, Center for Accelerator Science and Technology

The International Linear Collider Technical Design Report (TDR) describes in four volumes the physics case and the design of a 500 GeV centre-of-mass energy linear electron-positron collider based on superconducting radio-frequency technology using Niobium cavities as the accelerating structures. The accelerator can be extended to 1 TeV and also run as a Higgs factory at around 250 GeV and on the Z0 pole. A comprehensive value estimate of the accelerator is give, together with associated uncertainties. Read More

The ZFITTER project is aimed at the computation of high-precision theoretical predictions for various observables in high-energy electron-positron annihilation and other processes. The stages of the project development are described. Accent is made on applications to the analysis of LEP data. Read More

The generation and capture of polarized positrons at a source with a superconducting helical undulator having 4.3 cm period and 500 GeV electron drive beam have been simulated. The positron polarization has been calculated for the different undulator K values (up to K = 2. Read More

Affiliations: 1DESY, Zeuthen, Germany, 2II.Insitut für Theor. Physik, University of Hamburg, Hamburg, Germany, 3II.Insitut für Theor. Physik, University of Hamburg, Hamburg, Germany, 4II.Insitut für Theor. Physik, University of Hamburg, Hamburg, Germany, 5II.Insitut für Theor. Physik, University of Hamburg, Hamburg, Germany, 6DESY, Zeuthen, Germany, 7II.Insitut für Theor. Physik, University of Hamburg, Hamburg, Germany

The ILC baseline design for the positron source is based on radiation from a helical undulator to produce positrons in a thin target. Since the photon beam created in the helical undulator is circularly polarized, the generated positron beam is longitudinally polarized. Using a photon collimator upstream the positron target the positron polarization can be enhanced. Read More

Affiliations: 1II Institute for Theoretical Physics, University of Hamburg, Germany, 2II Institute for Theoretical Physics, University of Hamburg, Germany, 3Deutsches Elektronen-Synchrotron - DESY, Germany, 4II Institute for Theoretical Physics, University of Hamburg, Germany, 5II Institute for Theoretical Physics, University of Hamburg, Germany, 6Deutsches Elektronen-Synchrotron - DESY, Germany, 7Deutsches Elektronen-Synchrotron - DESY, Germany, 8II Institute for Theoretical Physics, University of Hamburg, Germany

In order to achieve the physics goals of future Linear Colliders, it is important that electron and positron beams are polarized. The baseline design at the International Linear Collider (ILC) foresees an e+ source based on helical undulator. Such a source provides high luminosity and polarizations. Read More

Affiliations: 1II. Institute for Theoretical Physics, University of Hamburg, Germany, 2II. Institute for Theoretical Physics, University of Hamburg, Germany, 3II. Institute for Theoretical Physics, University of Hamburg, Germany, 4DESY Standort Zeuthen, Germany, 5DESY Standort Zeuthen, Germany

To achieve the extremely high luminosity for colliding electron-positron beams at the future International Linear Collider (ILC) an undulator-based source with about 230 meters helical undulator and a thin titanium-alloy target rim rotated with tangential velocity of about 100 meters per second are foreseen. The very high density of heat deposited in the target has to be analyzed carefully. The energy deposited by the photon beam in the target has been calculated in FLUKA. Read More

Affiliations: 1II Institute for Theoretical Physics, University of Hamburg, Germany, 2II Institute for Theoretical Physics, University of Hamburg, Germany, 3Deutsches Elektronen-Synchrotron - DESY, Germany, 4II Institute for Theoretical Physics, University of Hamburg, Germany

To achieve the physics goals of future Linear Colliders, it is important that electron and positron beams are polarized. The positron source planned for the International Linear Collider (ILC) is based on a helical undulator system and can deliver a polarised beam with positron polarization of 60%. To ensure that no significant polarization is lost during the transport of the electron and positron beams from the source to the interaction region, spin tracking has to be included in all transport elements which can contribute to a loss of polarization. Read More

A possible solution to realize a conventional positron source driven by a several-GeV electron beam for the International Linear Collider is proposed. A 300 Hz electron linac is employed to create positrons with stretching pulse length in order to cure target thermal load. ILC requires about 2600 bunches in a train which pulse length is 1 ms. Read More

Discoveries at the LHC will soon set the physics agenda for future colliders. This report of a CERN Theory Institute includes the summaries of Working Groups that reviewed the physics goals and prospects of LHC running with 10 to 300/fb of integrated luminosity, of the proposed sLHC luminosity upgrade, of the ILC, of CLIC, of the LHeC and of a muon collider. The four Working Groups considered possible scenarios for the first 10/fb of data at the LHC in which (i) a state with properties that are compatible with a Higgs boson is discovered, (ii) no such state is discovered either because the Higgs properties are such that it is difficult to detect or because no Higgs boson exists, (iii) a missing-energy signal beyond the Standard Model is discovered as in some supersymmetric models, and (iv) some other exotic signature of new physics is discovered. Read More

Full exploitation of the physics potential of a future International Linear Collider will require the use of polarized electron and positron beams. Experiment E166 at the Stanford Linear Accelerator Center (SLAC) has demonstrated a scheme in which an electron beam passes through a helical undulator to generate photons (whose first-harmonic spectrum extended to 7.9MeV) with circular polarization, which are then converted in a thin target to generate longitudinally polarized positrons and electrons. Read More

Any future high energy e+e- linear collider aims at precision measurements of Standard Model quantities as well as of new, not yet discovered phenomena. In order to pursue this physics programme, excellent detectors at the interaction region have to be complemented by beam diagnostics of unprecedented precision. This article gives an overview of current plans and issues for polarimeters and energy spectrometers at the International Linear Collider, which have been designed to fulfill the precision goals at a large range of beam energies from 45. Read More

In this contribution accelerator solutions for polarized beams and their impact on physics measurements are discussed. Focus are physics requirements for precision polarimetry near the interaction point and their realization with polarized sources. Based on the ILC baseline programme as described in the Reference Design Report (RDR), recent developments are discussed and evaluated taking into account physics runs at beam energies between 100 GeV and 250 GeV, as well as calibration runs on the Z-pole and options as the 1TeV upgrade and GigaZ. Read More

The ILC baseline design for the positron source is based on a helical undulator and will deliver a positron beam with a polarization of 30% or more. In this contribution the need for fast reversal of the positron helicity is discussed. Read More

This note summarizes the results of the "Workshop on Polarisation and Beam Energy Measurements at the ILC", held at DESY (Zeuthen) April 9-11 2008. The topics for the workshop included (i) physics requirements, (ii) polarised sources and low energy polarimetry, (iii) BDS polarimeters, (iv) BDS energy spectrometers, and (v) physics-based measurements of beam polarisation and beam energy from collider data. Discussions focused on the current ILC baseline programme as described in the Reference Design Report (RDR), which includes physics runs at beam energies between 100 and 250 GeV, as well as calibration runs on the Z-pole. Read More

A short overview about the potential of polarized beams at future colliders is given. In particular the baseline design for polarized beams at the ILC is presented and the physics case for polarized $e^-$ and $e^+$ is discussed. In order to fulfil the precision requirements spin tracking from the source to the interaction point is needed. Read More

The radiation damage of the positron source target for the International Linear Collider (ILC) has been studied. The displacement damage in target material due to multi-MeV photons has been calculated by combining FLUKA simulations for secondary particle production, SPECTER data for neutron displacement cross-sections and the Lindhard model for estimations of displacement damage by ions. The radiation damage of a stationary Ti6Al4V target in units of displacements per atom (dpa) has been estimated for photons from an undulator with strength 0. Read More

Authors: S. Kraml, E. Accomando, A. G. Akeroyd, E. Akhmetzyanova, J. Albert, A. Alves, N. Amapane, M. Aoki, G. Azuelos, S. Baffioni, A. Ballestrero, V. Barger, A. Bartl, P. Bechtle, G. Belanger, A. Belhouari, R. Bellan, A. Belyaev, P. Benes, K. Benslama, W. Bernreuther, M. Besancon, G. Bevilacqua, M. Beyer, M. Bluj, S. Bolognesi, M. Boonekamp, F. Borzumati, F. Boudjema, A. Brandenburg, T. Brauner, C. P. Buszello, J. M. Butterworth, M. Carena, D. Cavalli, G. Cerminara, S. Y. Choi, B. Clerbaux, C. Collard, J. A. Conley, A. Deandrea, S. De Curtis, R. Dermisek, A. De Roeck, G. Dewhirst, M. A. Diaz, J. L. Diaz-Cruz, D. D. Dietrich, M. Dolgopolov, D. Dominici, M. Dubinin, O. Eboli, J. Ellis, N. Evans, L. Fano, J. Ferland, S. Ferrag, S. P. Fitzgerald, H. Fraas, F. Franke, S. Gennai, I. F. Ginzburg, R. M. Godbole, T. Gregoire, G. Grenier, C. Grojean, S. B. Gudnason, J. F. Gunion, H. E. Haber, T. Hahn, T. Han, V. Hankele, C. Hays, S. Heinemeyer, S. Hesselbach, J. L. Hewett, K. Hidaka, M. Hirsch, W. Hollik, D. Hooper, J. Hosek, J. Hubisz, C. Hugonie, J. Kalinowski, S. Kanemura, V. Kashkan, T. Kernreiter, W. Khater, V. A. Khoze, W. Kilian, S. F. King, O. Kittel, G. Klamke, J. L. Kneur, C. Kouvaris, M. Krawczyk, P. Krstonosic, A. Kyriakis, P. Langacker, M. P. Le, H. -S. Lee, J. S. Lee, M. C. Lemaire, Y. Liao, B. Lillie, V. Litvin, H. E. Logan, B. McElrath, T. Mahmoud, E. Maina, C. Mariotti, P. Marquard, A. D. Martin, K. Mazumdar, D. J. Miller, P. Mine, K. Moenig, G. Moortgat-Pick, S. Moretti, M. M. Muhlleitner, S. Munir, R. Nevzorov, H. Newman, P. Niezurawski, A. Nikitenko, R. Noriega-Papaqui, Y. Okada, P. Osland, A. Pilaftsis, W. Porod, H. Przysiezniak, A. Pukhov, D. Rainwater, A. Raspereza, J. Reuter, S. Riemann, S. Rindani, T. G. Rizzo, E. Ros, A. Rosado, D. Rousseau, D. P. Roy, M. G. Ryskin, H. Rzehak, F. Sannino, E. Schmidt, H. Schroder, M. Schumacher, A. Semenov, E. Senaha, G. Shaughnessy, R. K. Singh, J. Terning, L. Vacavant, M. Velasco, A. Villanova del Moral, F. von der Pahlen, G. Weiglein, J. Williams, K. Williams, A. F. Zarnecki, D. Zeppenfeld, D. Zerwas, P. M. Zerwas, A. R. Zerwekh, J. Ziethe

There are many possibilities for new physics beyond the Standard Model that feature non-standard Higgs sectors. These may introduce new sources of CP violation, and there may be mixing between multiple Higgs bosons or other new scalar bosons. Alternatively, the Higgs may be a composite state, or there may even be no Higgs at all. Read More

In a minimal model of universal extra dimensions the lightest Kalzua-Klein particle is neutral and stable because of Kaluza-Klein parity conservation and it is a dark matter candidate. The corresponding level 2 mode of the lightest Kaluza-Klein particle can be detected via KK number violating decays to Standard Model particles. The expected sensitivity to second level Kaluza-Klein modes of neutral gauge bosons at the ILC is studied. Read More

Affiliations: 1JINR, Dubna, 2DESY, Zeuthen and INP, Cracow, 3Univ. Wuerzburg and Univ. Silesia, Katowice, 4Fermilab, Batavia, 5University College Dublin, 6DESY, Zeuthen, 7DESY, Zeuthen, 8DESY, Zeuthen

ZFITTER is a Fortran program for the calculation of fermion pair production and radiative corrections at high energy e+e- colliders; it is also suitable for other applications where electroweak radiative corrections appear. ZFITTER is based on a semi-analytical approach to the calculation of radiative corrections in the Standard Model. We present a summary of new features of the ZFITTER program version 6. Read More

The proposed International Linear Collider (ILC) is well-suited for discovering physics beyond the Standard Model and for precisely unraveling the structure of the underlying physics. The physics return can be maximized by the use of polarized beams. This report shows the paramount role of polarized beams and summarizes the benefits obtained from polarizing the positron beam, as well as the electron beam. Read More

Authors: LHC/LC Study Group, :, G. Weiglein, T. Barklow, E. Boos, A. De Roeck, K. Desch, F. Gianotti, R. Godbole, J. F. Gunion, H. E. Haber, S. Heinemeyer, J. L. Hewett, K. Kawagoe, K. Monig, M. M. Nojiri, G. Polesello, F. Richard, S. Riemann, W. J. Stirling, A. G. Akeroyd, B. C. Allanach, D. Asner, S. Asztalos, H. Baer, M. Battaglia, U. Baur, P. Bechtle, G. Belanger, A. Belyaev, E. L. Berger, T. Binoth, G. A. Blair, S. Boogert, F. Boudjema, D. Bourilkov, W. Buchmuller, V. Bunichev, G. Cerminara, M. Chiorboli, H. Davoudiasl, S. Dawson, S. De Curtis, F. Deppisch, M. A. Diaz, M. Dittmar, A. Djouadi, D. Dominici, U. Ellwanger, J. L. Feng, I. F. Ginzburg, A. Giolo-Nicollerat, B. K. Gjelsten, S. Godfrey, D. Grellscheid, J. Gronberg, E. Gross, J. Guasch, K. Hamaguchi, T. Han, J. Hisano, W. Hollik, C. Hugonie, T. Hurth, J. Jiang, A. Juste, J. Kalinowski, W. Kilian, R. Kinnunen, S. Kraml, M. Krawczyk, A. Krokhotine, T. Krupovnickas, R. Lafaye, S. Lehti, H. E. Logan, E. Lytken, V. Martin, H. -U. Martyn, D. J. Miller, S. Moretti, F. Moortgat, G. Moortgat-Pick, M. Muhlleitner, P. Niezurawski, A. Nikitenko, L. H. Orr, P. Osland, A. F. Osorio, H. Pas, T. Plehn, W. Porod, A. Pukhov, F. Quevedo, D. Rainwater, M. Ratz, A. Redelbach, L. Reina, T. Rizzo, R. Ruckl, H. J. Schreiber, M. Schumacher, A. Sherstnev, S. Slabospitsky, J. Sola, A. Sopczak, M. Spira, M. Spiropulu, Z. Sullivan, M. Szleper, T. M. P. Tait, X. Tata, D. R. Tovey, A. Tricomi, M. Velasco, D. Wackeroth, C. E. M. Wagner, S. Weinzierl, P. Wienemann, T. Yanagida, A. F. Zarnecki, D. Zerwas, P. M. Zerwas, L. Zivkovic

Physics at the Large Hadron Collider (LHC) and the International e+e- Linear Collider (ILC) will be complementary in many respects, as has been demonstrated at previous generations of hadron and lepton colliders. This report addresses the possible interplay between the LHC and ILC in testing the Standard Model and in discovering and determining the origin of new physics. Mutual benefits for the physics programme at both machines can occur both at the level of a combined interpretation of Hadron Collider and Linear Collider data and at the level of combined analyses of the data, where results obtained at one machine can directly influence the way analyses are carried out at the other machine. Read More

Extending the sensitivity to New Physics beyond the anticipated reach of the LHC is a prime aim of future colliders. This paper summarises the potential of an e+e- linear collider, at and beyond 1 TeV, using a realistic simulation of the detector response and the accelerator induced background. The possible LC energy-luminosity trade-offs offered in probing multi-TeV scales for new phenomena with electro-weak observables are also discussed. Read More

Authors: R. -D. Heuer, D. J. Miller, F. Richard, P. M. Zerwas, J. A. Aguilar-Saavedra, J. Alcaraz, A. Ali, S. Ambrosanio, A. Andreazza, J. Andruszkow, B. Badelek, A. Ballestrero, T. Barklow, A. Bartl, M. Battaglia, T. Behnke, G. Belanger, D. Benson, M. Berggren, W. Bernreuther, M. Besancon, J. Biebel, O. Biebel, I. Bigi, J. J. van der Bij, T. Binoth, G. A. Blair, C. Blochinger, J. Blumlein, M. Boonekamp, E. Boos, G. Borissov, A. Brandenburg, J. -C. Brient, G. Bruni, K. Busser, P. Burrows, R. Casalbuoni, C. Castanier, P. Chankowski, A. Chekanov, R. Chierici, S. Y. Choi, P. Christova, P. Ciafaloni, D. Comelli, G. Conteras, M. Danilov, W. Da Silva, A. Deandrea, W. de Boer, S. De Curtis, S. J. De Jong, A. Denner, A. De Roeck, K. Desch, E. De Wolf, S. Dittmaier, V. Djordjadze, A. Djouadi, D. Dominici, M. Doncheski, M. T. Dova, V. Drollinger, H. Eberl, J. Erler, A. Eskreys, J. R. Espinosa, N. Evanson, E. Fernandez, J. Forshaw, H. Fraas, F. Franke, A. Freitas, F. Gangemi, P. Garcia-Abia, R. Gatto, P. Gay, T. Gehrmann, A. Gehrmann-De Ridder, U. Gensch, N. Ghodbane, I. F. Ginzburg, R. Godbole, S. Godfrey, G. Gounaris, M. Grazzini, E. Gross, B. Grzadkowski, J. Guasch, J. F. Gunion, K. Hagiwara, T. Han, K. Harder, R. Harlander, R. Hawkings, S. Heinemeyer, S. Hesselbach, C. A. Heusch, J. Hewett, G. Hiller, A. Hoang, W. Hollik, J. I. Illana, V. A. Ilyin, D. Indumathi, S. Ishihara, M. Jack, S. Jadach, F. Jegerlehner, M. Jezabek, G. Jikia, L. Jonsson, P. Jankowski, P. Jurkiewicz, A. Juste, A. Kagan, J. Kalinowski, M. Kalmykov, P. Kalyniak, B. Kamal, J. Kamoshita, S. Kanemura, F. Kapusta, S. Katsanevas, R. Keranen, V. Khoze, A. Kiiskinen, W. Kilian, M. Klasen, J. L. Kneur, B. A. Kniehl, M. Kobel, K. Kolodziej, M. Kramer, S. Kraml, M. Krawczyk, J. H. Kuhn, J. Kwiecinski, P. Laurelli, A. Leike, J. Letts, W. Lohmann, S. Lola, P. Lutz, P. Mattig, W. Majerotto, T. Mannel, M. Martinez, H. -U. Martyn, T. Mayer, B. Mele, M. Melles, W. Menges, G. Merino, N. Meyer, D. J. Miller, P. Minkowski, R. Miquel, K. Monig, G. Montagna, G. Moortgat-Pick, P. Mora de Freitas, G. Moreau, M. Moretti, S. Moretti, L. Motyka, G. Moultaka, M. Muhlleitner, U. Nauenberg, R. Nisius, H. Nowak, T. Ohl, R. Orava, J. Orloff, P. Osland, G. Pancheri, A. A. Pankov, C. Papadopoulos, N. Paver, D. Peralta, H. T. Phillips, F. Picinini, W. Placzek, M. Pohl, W. Porod, A. Pukhov, A. Raspereza, D. Reid, S. Riemann, T. Riemann, S. Rosati, M. Roth, S. Roth, C. Royon, R. Ruckl, E. Ruiz-Morales, M. Sachwitz, J. Schieck, H. -J. Schreiber, D. Schulte, M. Schumacher, R. D. Settles, M. Seymour, R. Shanidze, T. Sjostrand, M. Skrzypek, S. Soldner-Rembold, A. Sopczak, H. Spiesberger, M. Spira, H. Steiner, M. Stratmann, Y. Sumino, S. Tapprogge, V. Telnov, T. Teubner, A. Tonazzo, C. Troncon, O. Veretin, C. Verzegnassi, A. Vest, A. Vicini, H. Videau, W. Vogelsang, A. Vogt, H. Vogt, D. Wackeroth, A. Wagner, S. Wallon, G. Weiglein, S. Weinzierl, T. Wengler, N. Wermes, A. Werthenbach, G. Wilson, M. Winter, A. F. Zarnecki, B. Ziaja, J. Zochowski

The TESLA Technical Design Report Part III: Physics at an e+e- Linear Collider Read More

Preliminary results of measurements of fermion-pair production at LEP2 are used to derive limits on new physics phenomena. Combinations of the cross sections and asymmetrie of the 4 LEP collaborations are interpreted in terms four-fermion contact interactions, exchange of Z' and leptoquarks. Results on the search for extra dimensions are also presented. Read More

This report summarizes the results of the two-fermion working group of the LEP2-MC workshop, held at CERN from 1999 to 2000. Recent developments in the theoretical calculations of the two fermion production process in the electron-positron collision at LEP2 center of the mass energies are reported. The Bhabha process and the production of muon, tau, neutrino and quark pairs is covered. Read More

Affiliations: 1LNP, JINR, Dubna, Russia, 2DESY Zeuthen, Germany, 3DESY Zeuthen, Germany, 4DESY Zeuthen, Germany

The past ten years of physics with e+e- colliding experiments at LEP and SLAC have shown the success of these experiments on not only impressively proving the theoretical predictions of the Standard Model (SM), but also to help provide stringent bounds on physics beyond the SM. With this experience in mind, there appear two equally fascinating opportunities for studying fermion-pair production processes at a future Linear Collider (LC). On the one hand, performing high precision measurements to the SM, for example, when running with high luminosity at the Z boson resonance, could be a quick and feasible enterprise in order to pin down the symmetry breaking mechanism of the electroweak sector through indirectly determining the masses of a light SM or MSSM Higgs boson or supersymmetric particles via virtual corrections. Read More

New data on parity violation in atomic cesium can be explained by a new neutral vector boson almost unmixed with Z, with a mass in the TeV range and sizeable couplings to the fermions. The properties of such additional Z' can be investigated at future linear colliders. Read More

Affiliations: 1JINR Dubna, 2IPAS Prague, 3Univ. Shoumen, 4DESY Zeuthen, 5JINR Dubna, 6JINR Dubna, 7DESY Zeuthen, 8DESY Zeuthen

We describe ZFITTER, a Fortran program based on a semi-analytical approach to fermion pair production in e+e- annihilation at a wide range of centre-of-mass energies, including the PETRA, TRISTAN, LEP1/SLC, and LEP2 energies. A flexible treatment of complete O(alpha) QED corrections and of some higher order contributions is made possible with three calculational chains containing different realistic sets of restrictions in the photon phase space. Numerical integrations are at most one-dimensional. Read More

Affiliations: 1Univ. Shoumen, Bulgaria and JINR, Dubna, Russia, 2DESY Zeuthen, Germany, 3DESY Zeuthen, Germany, 4DESY Zeuthen, Germany

ZFITTER is a Fortran package for the description of fermion-pair production in e+e- annihilation. We report on results of a rederivation of the complete set of analytical O(alpha) formulae for the treatment of photonic corrections to the total cross-section and the integrated forward-backward asymmetry with combined cuts on acollinearity angle, acceptance angle, and minimal energy of the fermions. Numerically, the following changes result in ZFITTER v. Read More

The status of predictions for fermion-pair production at LEP is summarized with emphasis on LEP2 energies and on the physics interest there. Some numerical comparisons with other programs are performed. We also present first results of a semi-analytical recalculation of photonic corrections with acollinearity cut in the ZFITTER approach. Read More

We derive a method for a common treatment of Z' exchange, QED corrections, and weak loops. It is based on the form factor approach to the description of weak loop corrections to partial Z widths and cross sections. Problems connected with ZZ' mixing are discussed with special care. Read More

The search for a Z' is one of the tasks of future colliders. I study the capability to detect the Z' at a linear e+e- collider operating below resonance production. Depending on m_{\Zp} and the collider parameters we will be able to discriminate between Z' models. Read More

The report summarizes the results of the activities of the Working Group on Precision Calculations for the Z Resonance at CERN during 1994. Read More

The discovery of a Z' and the measurement of Z' couplings to fermions are main tasks of future colliders. Here, the possibilities to measure Z' f \bar f couplings at an NLC operating below a Z' resonance are studied. In dependence on the mass of the Z' and the collider parameters one will be able to discriminate between Z' models. Read More

Expectations for constraints on extra Z bosons are derived for LEP 2 and future linear e+e- colliders. For typical GUTs, a Z' with M_{Z'} \le 3 to 6 \sqrt{s} may cause observable effects. The Z' discovery limits are dominated by statistical errors. Read More

The limits on extra neutral gauge bosons, which could be reached at LEP2, are reviewed. Exclusion and discovery limits are discussed for f\bar f and WW production. Read More

Constraints on extra neutral gauge bosons are obtained from $e^+e^-\rightarrow f\bar f$ at NLC energies. Model independent limits on the $Z'f\bar f$ couplings and lower limits on the $Z'$ mass are discussed. Typical GUTs with $M_{Z'}$ up to (3 -- 6) $\sqrt{s}$ can be excluded. Read More

We present a method for a common treatment of $Z'$ exchange, QED corrections, and weak loops in $e^+ e^-$ annihilation. QED corrections are taken into account by convoluting a hard-scattering cross section containing $\gamma,\ Z,$ and $Z'$ exchange. Weak corrections and $ZZ'$ mixing are treated simultaneously by a generalization of weak form factors. Read More

We describe how to use ZFITTER, a program based on a semi-analytical approach to fermion pair production in e+e- annihilation and Bhabha scattering. A flexible treatment of complete ${\cal O}(\alpha)$ QED corrections, also including higher orders, allows for three calculational {\bf chains} with different realistic sets of restrictions in the photon phase space. {\tt ZFITTER} consists of several {\bf branches} with varying assumptions on the underlying hard scattering process. Read More