Showing 1–34 of 34 results for author: Riemann, S

A Linear Collider Vision for the Future of Particle Physics

Authors: H. Abramowicz, E. Adli, F. Alharthi, M. Almanza-Soto, M. M. Altakach, W. Altmannshofer, S. Ampudia Castelazo, D. Angal-Kalinin, J. A. Anguiano, R. B. Appleby, O. Apsimon, A. Arbey, F. Arco, O. Arquero, A. Aryshev, S. Asai, D. Attie, J. L. Avila-Jimenez, H. Baer, J. A. Bagger, Y. Bai, I. R. Bailey, C. Balazs, P. Bambade, T. Barklow , et al. (426 additional authors not shown)

Abstract: In this paper we review the physics opportunities at linear $e^+e^-$ colliders with a special focus on high centre-of-mass energies and beam polarisation, take a fresh look at the various accelerator technologies available or under development and, for the first time, discuss how a facility first equipped with a technology mature today could be upgraded with technologies of tomorrow to reach much… ▽ More In this paper we review the physics opportunities at linear $e^+e^-$ colliders with a special focus on high centre-of-mass energies and beam polarisation, take a fresh look at the various accelerator technologies available or under development and, for the first time, discuss how a facility first equipped with a technology mature today could be upgraded with technologies of tomorrow to reach much higher energies and/or luminosities. In addition, we will discuss detectors and alternative collider modes, as well as opportunities for beyond-collider experiments and R\&D facilities as part of a linear collider facility (LCF). The material of this paper will support all plans for $e^+e^-$ linear colliders and additional opportunities they offer, independently of technology choice or proposed site, as well as R\&D for advanced accelerator technologies. This joint perspective on the physics goals, early technologies and upgrade strategies has been developed by the LCVision team based on an initial discussion at LCWS2024 in Tokyo and a follow-up at the LCVision Community Event at CERN in January 2025. It heavily builds on decades of achievements of the global linear collider community, in particular in the context of CLIC and ILC. △ Less

Submitted 23 December, 2025; v1 submitted 25 March, 2025; originally announced March 2025.

Comments: Community document for EPPSU, major updates of several sections, in particular the global interpretation section

R&D for Positron Sources at High-Energy Lepton Colliders

Authors: Gudrid Moortgat-Pick, Sabine Riemann, Peter Sievers, Carmen Tenholt

Abstract: Several designs for high-energy Lepton Colliders serving as Higgs factories but extendable to higher energies up to the TeV range are under discussion. The most mature design is the International Linear Collider (ILC), but also the Compact Linear Collider (CLIC) as well as the new concept of a Hybrid Asymmetric Linear Higgs Factory (HALHF) have a large physics potential. The first energy stage wit… ▽ More Several designs for high-energy Lepton Colliders serving as Higgs factories but extendable to higher energies up to the TeV range are under discussion. The most mature design is the International Linear Collider (ILC), but also the Compact Linear Collider (CLIC) as well as the new concept of a Hybrid Asymmetric Linear Higgs Factory (HALHF) have a large physics potential. The first energy stage with $\sqrt{s}=250$~GeV requires high luminosity and polarized beams and imposes an effort for all positron source designs at high-energy colliders. In the baseline design of the ILC, an undulator-based source is foreseen for the positron source in order to match the physics requirements. In this contribution an overview is given about the undulator-based source, the target tests, the rotating target wheel design, as well as the pulsed solenoid and the new technology development of plasma lenses as optic matching devices. △ Less

Submitted 27 September, 2023; v1 submitted 5 September, 2023; originally announced September 2023.

Comments: 14 pages, 17 figures, talk presented at the International Workshop on Future Linear Colliders (LCWS2023), 15-19 May 2023. C23-05-15.3 Report number added

Report number: DESY-23-138

Computer package DIZET v. 6.45

Authors: A. Arbuzov, J. Gluza, L. Kalinovskaya, S. Riemann, T. Riemann, V. Yermolchyk

Abstract: The new version of the DIZET electroweak library is described. Changes and additional code features concerning the previous version are explained. The software allows one to make state-of-the-art theoretical predictions for pseudo-observable quantities, including higher-order radiative corrections. The current version of the DIZET library v. 6.45 incorporates advanced recent results of theoretical… ▽ More The new version of the DIZET electroweak library is described. Changes and additional code features concerning the previous version are explained. The software allows one to make state-of-the-art theoretical predictions for pseudo-observable quantities, including higher-order radiative corrections. The current version of the DIZET library v. 6.45 incorporates advanced recent results of theoretical calculations. Numerical comparisons with the results of the previous version are performed. Estimates of theoretical uncertainties are discussed. △ Less

Submitted 17 January, 2023; originally announced January 2023.

Comments: 14 pages, 3 figures, 8 tables

The International Linear Collider: Report to Snowmass 2021

Authors: Alexander Aryshev, Ties Behnke, Mikael Berggren, James Brau, Nathaniel Craig, Ayres Freitas, Frank Gaede, Spencer Gessner, Stefania Gori, Christophe Grojean, Sven Heinemeyer, Daniel Jeans, Katja Kruger, Benno List, Jenny List, Zhen Liu, Shinichiro Michizono, David W. Miller, Ian Moult, Hitoshi Murayama, Tatsuya Nakada, Emilio Nanni, Mihoko Nojiri, Hasan Padamsee, Maxim Perelstein , et al. (487 additional authors not shown)

Abstract: The International Linear Collider (ILC) is on the table now as a new global energy-frontier accelerator laboratory taking data in the 2030s. The ILC addresses key questions for our current understanding of particle physics. It is based on a proven accelerator technology. Its experiments will challenge the Standard Model of particle physics and will provide a new window to look beyond it. This docu… ▽ More The International Linear Collider (ILC) is on the table now as a new global energy-frontier accelerator laboratory taking data in the 2030s. The ILC addresses key questions for our current understanding of particle physics. It is based on a proven accelerator technology. Its experiments will challenge the Standard Model of particle physics and will provide a new window to look beyond it. This document brings the story of the ILC up to date, emphasizing its strong physics motivation, its readiness for construction, and the opportunity it presents to the US and the global particle physics community. △ Less

Submitted 16 January, 2023; v1 submitted 14 March, 2022; originally announced March 2022.

Comments: 356 pages, Large pdf file (40 MB) submitted to Snowmass 2021; v2 references to Snowmass contributions added, additional authors; v3 references added, some updates, additional authors

Report number: DESY-22-045, IFT--UAM/CSIC--22-028, KEK Preprint 2021-61, PNNL-SA-160884, SLAC-PUB-17662

Plasma Lenses: Possible alternative OMD at the ILC

Authors: Manuel Formela, Niclas Hamann, Klaus Floettmann, Gudrid Moortgat-Pick, Sabine Riemann, Andriy Ushakov

Abstract: In the baseline design of the International Linear Collider (ILC) an undulator-based source is foreseen for the positron source in order to match the physics requirements. The recently chosen first energy stage with sqrt(s)=250 GeV requires high luminosity and imposes an effort for all positron source designs at high-energy colliders. In this paper we perform a simulation study and adopt the new t… ▽ More In the baseline design of the International Linear Collider (ILC) an undulator-based source is foreseen for the positron source in order to match the physics requirements. The recently chosen first energy stage with sqrt(s)=250 GeV requires high luminosity and imposes an effort for all positron source designs at high-energy colliders. In this paper we perform a simulation study and adopt the new technology of plasma lenses to capture the positrons generated by the undulator photons and to create the required high luminosity positron beam. △ Less

Submitted 10 March, 2020; v1 submitted 6 March, 2020; originally announced March 2020.

Comments: Talk presented at the International Workshop on Future Linear Colliders (LCWS2019), Sendai, Japan, 28 October-1 November 2019

Report number: DESY 20-027

Standard Model Theory for the FCC-ee Tera-Z stage

Authors: A. Blondel, J. Gluza, S. Jadach, P. Janot, T. Riemann, A. Akhundov, A. Arbuzov, R. Boels, S. Bondarenko, S. Borowka, C. M. Carloni Calame, I. Dubovyk, Y. Dydyshka, W. Flieger, A. Freitas, K. Grzanka, T. Hahn, T. Huber, L. Kalinovskaya, R. Lee, P. Marquard, G. Montagna, O. Nicrosini, C. G. Papadopoulos, F. Piccinini , et al. (13 additional authors not shown)

Abstract: The future 100-km circular collider FCC at CERN is planned to operate in one of its modes as an electron-positron FCC-ee machine. We give an overview comparing the theoretical status to the experimental demands of one of four foreseen FCC-ee operating stages, Z-boson resonance energy physics, called the FCC-ee Tera-Z stage for short. The FCC-ee Tera-Z will deliver the highest integrated luminositi… ▽ More The future 100-km circular collider FCC at CERN is planned to operate in one of its modes as an electron-positron FCC-ee machine. We give an overview comparing the theoretical status to the experimental demands of one of four foreseen FCC-ee operating stages, Z-boson resonance energy physics, called the FCC-ee Tera-Z stage for short. The FCC-ee Tera-Z will deliver the highest integrated luminosities as well as very small systematic errors for a study of the Standard Model (SM) with unprecedented precision. In fact, the FCC-ee Tera-Z will allow the study of at least one more perturbative order in quantum field theory compared to the LEP/SLC precision. The real problem is that the present precision of theoretical calculations of the various SM observables does not match that of the anticipated experimental measurements. The bottle-necks to overcoming this situation are identified. In particular, the issues of precise QED unfolding and the correct calculation of SM pseudo-observables are critically reviewed. In an Executive Summary, we specify which basic theoretical calculations are needed to meet the strong experimental expectations at the FCC-ee Tera-Z. Several methods, techniques and tools needed for higher-order multi-loop calculations are presented. By inspection of the Z-boson partial and total decay width analyses, it is argued that at the beginning of operation of the FCC-ee Tera-Z, the theory predictions may be tuned to be precise enough not to limit the physics interpretation of the measurements. This statement is based on anticipated progress in analytical and numerical calculations of multi-loop and multi-scale Feynman integrals and on the completion of two-loop electroweak radiative corrections to the SM pseudo-observables this year. However, the above statement is conditional as the theoretical issues demand a very dedicated and focused investment by the community. △ Less

Submitted 20 September, 2019; v1 submitted 6 September, 2018; originally announced September 2018.

Comments: Published version

Report number: BU-HEPP-18-04, CERN-TH-2018-145, IFJ-PAN-IV-2018-09, KW 18-003, MITP/18-052, MPP-2018-143, SI-HEP-2018-21

Journal ref: CERN Yellow Rep. Monogr. 3 (2019)

The role of positron polarization for the inital $250$ GeV stage of the International Linear Collider

Authors: Keisuke Fujii, Christophe Grojean, Michael E. Peskin, Tim Barklow, Yuanning Gao, Shinya Kanemura, Hyungdo Kim, Jenny List, Mihoko Nojiri, Maxim Perelstein, Roman Pöschl, Jürgen Reuter, Frank Simon, Tomohiko Tanabe, James D. Wells, Jaehoon Yu, Mikael Berggren, Moritz Habermehl, Robert Karl, Gudrid Moortgat-Pick, Sabine Riemann, Junping Tian, Graham W. Wilson, James Brau, Hitoshi Murayama

Abstract: The International Linear Collider is now proposed with a staged machine design, with the first stage at $\sqrt{s}=$~250 GeV and an integrated luminosity goal of 2~ab$^{-1}$. One of the questions for the machine design is the importance of positron polarization. In this report, we review the impact of positron polarization on the physics goals of the $250$ GeV stage of the ILC and demonstrate that… ▽ More The International Linear Collider is now proposed with a staged machine design, with the first stage at $\sqrt{s}=$~250 GeV and an integrated luminosity goal of 2~ab$^{-1}$. One of the questions for the machine design is the importance of positron polarization. In this report, we review the impact of positron polarization on the physics goals of the $250$ GeV stage of the ILC and demonstrate that positron polarization has distinct advantages. △ Less

Submitted 9 January, 2018; originally announced January 2018.

Comments: 19

Report number: DESY 17-237, KEK Preprint 2017-57, SLAC-PUB-17197

Physics at the CLIC e+e- Linear Collider -- Input to the Snowmass process 2013

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 , et al. (98 additional authors not shown)

Abstract: 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 accomp… ▽ More 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. △ Less

Submitted 30 September, 2013; v1 submitted 19 July, 2013; originally announced July 2013.

Comments: Updated the author list, updated Higgs results and small changes in the text of the Higgs section, updated results on composite Higgs bosons, added and updated references. Final submission for the Snowmass proceedings

The International Linear Collider Technical Design Report - Volume 2: Physics

Authors: Howard Baer, Tim Barklow, Keisuke Fujii, Yuanning Gao, Andre Hoang, Shinya Kanemura, Jenny List, Heather E. Logan, Andrei Nomerotski, Maxim Perelstein, Michael E. Peskin, Roman Pöschl, Jürgen Reuter, Sabine Riemann, Aurore Savoy-Navarro, Geraldine Servant, Tim M. P. Tait, Jaehoon Yu

Abstract: 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… ▽ More 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. It is shown that no significant technical issues remain to be solved. Once a site is selected and the necessary site-dependent engineering is carried out, construction can begin immediately. The TDR also gives baseline documentation for two high-performance detectors that can share the ILC luminosity by being moved into and out of the beam line in a "push-pull" configuration. These detectors, ILD and SiD, are described in detail. They form the basis for a world-class experimental programme that promises to increase significantly our understanding of the fundamental processes that govern the evolution of the Universe. △ Less

Submitted 26 June, 2013; originally announced June 2013.

Comments: See also http://www.linearcollider.org/ILC/TDR . The full list of signatories is inside the Report

Report number: ILC-REPORT-2013-040; ANL-HEP-TR-13-20; BNL-100603-2013-IR; IRFU-13-59; CERN-ATS-2013-037; Cockcroft-13-10; CLNS 13/2085; DESY 13-062; FERMILAB TM-2554; IHEP-AC-ILC-2013-001; INFN-13-04/LNF; JAI-2013-001; JINR E9-2013-35; JLAB-R-2013-01; KEK Report 2013-1; KNU/CHEP-ILC-2013-1; LLNL-TR-635539; SLAC-R-1004; ILC-HiGrade-Report-2013-003

ZFITTER 1985-2013

Authors: Arif Akhundov, Andrej Arbuzov, Sabine Riemann, Tord Riemann

Abstract: 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. The present status of the project and perspectives are given as well. 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. The present status of the project and perspectives are given as well. △ Less

Submitted 12 June, 2014; v1 submitted 6 February, 2013; originally announced February 2013.

Comments: Dedicated to Pena Christova on the occasion of her 70th birthday. Version 2 has minor improvements, added references and a changed affiliation. Version 3 is published in Phys.Part.Nucl. 45 (2014) 3, 529-549 under the title "The ZFITTER project", the references are updated in May 2014. Online at SpringerLink http://link.springer.com/article/10.1134%2FS1063779614030022

Journal ref: Phys.Part.Nucl. 45 (2014) 3, 529-549

From the LHC to Future Colliders

Authors: A. De Roeck, J. Ellis, C. Grojean, S. Heinemeyer, K. Jakobs, G. Weiglein, J. Wells, G. Azuelos, S. Dawson, B. Gripaios, T. Han, J. Hewett, M. Lancaster, C. Mariotti, F. Moortgat, G. Moortgat-Pick, G. Polesello, S. Riemann, M. Schumacher, K. Assamagan, P. Bechtle, M. Carena, G. Chachamis, K. F. Chen, S. De Curtis , et al. (39 additional authors not shown)

Abstract: 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 po… ▽ 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. In the contexts of these scenarios, the Working Groups reviewed the capabilities of the future colliders to study in more detail whatever new physics may be discovered by the LHC. Their reports provide the particle physics community with some tools for reviewing the scientific priorities for future colliders after the LHC produces its first harvest of new physics from multi-TeV collisions. △ Less

Submitted 17 September, 2009; originally announced September 2009.

Comments: 98 pages, CERN Theory Institute Summary Report

Report number: CERN-PH-TH/2009-166, DCPT/09/136, IPPP/09/068, SLAC-PUB-13782

Journal ref: Eur.Phys.J.C66:525-583,2010

Challenge of polarized beams at future colliders

Authors: G. Moortgat-Pick, I. R. Bailey, D. P. Barber, E. Baynham, A. Birch, T. Bradshaw, A. Brummitt, S. Carr, J. A. Clarke, P. Cooke, J. B. Dainton, T. Hartin, Y. Ivanyushenkov, L. J. Jenner, A. Lintern, L. I. Malysheva, O. B. Malyshev, J. Rochford, S. Riemann, A. Schälicke, P. Schmid, D. J. Scott, A. Ushakov, L. Zang

Abstract: 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. Updates concerning the theoretical calculations as well a… ▽ 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. Updates concerning the theoretical calculations as well as their implementation in simulation codes are reported. △ Less

Submitted 15 January, 2008; originally announced January 2008.

Comments: 5 pages, contribution to the proceedings of EPS07

Report number: COCKCROFT-07-22, IPPP/07/72, DCPT/07/144

Journal ref: J.Phys.Conf.Ser.110:112004,2008

CP Studies and Non-Standard Higgs Physics

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 , et al. (141 additional authors not shown)

Abstract: 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. These non-standard Higgs scenarios have important implications for… ▽ More 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. These non-standard Higgs scenarios have important implications for collider physics as well as for cosmology, and understanding their phenomenology is essential for a full comprehension of electroweak symmetry breaking. This report discusses the most relevant theories which go beyond the Standard Model and its minimal, CP-conserving supersymmetric extension: two-Higgs-doublet models and minimal supersymmetric models with CP violation, supersymmetric models with an extra singlet, models with extra gauge groups or Higgs triplets, Little Higgs models, models in extra dimensions, and models with technicolour or other new strong dynamics. For each of these scenarios, this report presents an introduction to the phenomenology, followed by contributions on more detailed theoretical aspects and studies of possible experimental signatures at the LHC and other colliders. △ Less

Submitted 7 August, 2006; originally announced August 2006.

Comments: Report of the CPNSH workshop, May 2004 - Dec 2005, 542 pages. The complete report as well as its individual chapters are also available from http://kraml.home.cern.ch/kraml/cpnsh/report.html

Report number: CERN-2006-009

Z' Signals from Kaluza-Klein Dark Matter

Authors: S. Riemann

Abstract: 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 neu… ▽ 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. △ Less

Submitted 12 August, 2005; v1 submitted 11 August, 2005; originally announced August 2005.

Comments: Talk given at 2005 International Linear Collider Workshop (LCWS 2005), Stanford, California, 18-22 Mar 2005

ZFITTER: a semi-analytical program for fermion pair production in e+e- annihilation, from version 6.21 to version 6.42

Authors: A. B. Arbuzov, M. Awramik, M. Czakon, A. Freitas, M. W. Gruenewald, K. Moenig, S. Riemann, T. Riemann

Abstract: 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… ▽ More 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 6.42 compared to version 6.21. The most important additions are: (i) some higher-order QED corrections to fermion pair production, (ii) electroweak one-loop corrections to atomic parity violation, (iii) electroweak one-loop corrections to nu-e nu-e-bar production, (iv) electroweak two-loop corrections to the W boson mass and the effective weak mixing angle. △ Less

Submitted 12 July, 2005; originally announced July 2005.

Comments: 60 pages, latex, 3 tables

Report number: DESY 05-034, UCD-EXPH/050701, FERMILAB-Pub-05-256-T, WUE-ITP-2005-004, SFB/CPP-05-22

Journal ref: Comput.Phys.Commun.174:728-758,2006

The role of polarized positrons and electrons in revealing fundamental interactions at the Linear Collider

Authors: G. Moortgat-Pick, T. Abe, G. Alexander, B. Ananthanarayan, A. A. Babich, V. Bharadwaj, D. Barber, A. Bartl, A. Brachmann, S. Chen, J. Clarke, J. E. Clendenin, J. Dainton, K. Desch, M. Diehl, B. Dobos, T. Dorland, H. Eberl, J. Ellis, K. Flöttmann, H. Fraas, F. Franco-Sollova, F. Franke, A. Freitas, J. Goodson , et al. (49 additional authors not shown)

Abstract: 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 elec… ▽ 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. The physics case for this option is illustrated explicitly by analyzing reference reactions in different physics scenarios. The results show that positron polarization, combined with the clean experimental environment provided by the linear collider, allows to improve strongly the potential of searches for new particles and the identification of their dynamics, which opens the road to resolve shortcomings of the Standard Model. The report also presents an overview of possible designs for polarizing both beams at the ILC, as well as for measuring their polarization. △ Less

Submitted 1 July, 2005; originally announced July 2005.

Comments: 149 pages, 95 eps+ps figures, report of the polarization working group `POWER'; version with high resolutions figures are available via http://www.ippp.dur.ac.uk/~gudrid/power/ and the slac preprint server

Report number: CERN-PH-TH/2005-036,DCPT-04-100,DESY 05-059,FERMILAB-PUB-05-060-T,IPPP-04-50,KEK Preprint 2005-16,PRL-TH-05/01, SHEP-05-03,SLAC-PUB-11087

Journal ref: Phys.Rept.460:131-243,2008

Physics Interplay of the LHC and the ILC

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 , et al. (99 additional authors not shown)

Abstract: 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… ▽ More 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. Topics under study comprise the physics of weak and strong electroweak symmetry breaking, supersymmetric models, new gauge theories, models with extra dimensions, and electroweak and QCD precision physics. The status of the work that has been carried out within the LHC / LC Study Group so far is summarised in this report. Possible topics for future studies are outlined. △ Less

Submitted 27 October, 2004; originally announced October 2004.

Comments: 472 pages, a version with high-resolution figures can be found at http://www.ippp.dur.ac.uk/~georg/lhclc/lhclcdoc.ps.gz

Report number: ANL-HEP-PR-04-108, CERN-PH-TH/2004-214, DCPT/04/134, DESY 04-206, IFIC/04-59, IISc/CHEP/13/04, IPPP/04/67, SLAC-PUB-10764, UB-ECM-PF-04/31, UCD-04-28, UCI-TR-2004-37

Journal ref: Phys.Rept.426:47-358,2006

Probing New Scales at a e+e- Linear Collider

Authors: M. Battaglia, S. De Curtis, D. Dominici, S. Riemann

Abstract: 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 wit… ▽ 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. △ Less

Submitted 20 December, 2001; originally announced December 2001.

Comments: 5 pages, 2 figures, to appear on the proceedings of the APS / DPF / DPB Summer Study on the Future of Particle Physics (Snowmass 2001), Snowmass, Colorado, 30 Jun - 21 Jul 2001

Journal ref: eConf C010630 (2001) E3020

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

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 , et al. (215 additional authors not shown)

Abstract: The TESLA Technical Design Report Part III: Physics at an e+e- Linear Collider The TESLA Technical Design Report Part III: Physics at an e+e- Linear Collider △ Less

Submitted 27 June, 2001; originally announced June 2001.

Comments: 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

Report number: DESY 2001-011, ECFA 2001-209

Two-Fermion Production in Electron-Positron Collisions

Authors: Michael Kobel, Zbigniew Was, C. Ainsley, A. Arbuzov, S. Arcelli, D. Bardin, I. Boyko, D. Bourilkov, P. Christova, J. Fujimoto, M. Gruenewald, T. Ishikawa, M. Jack, S. Jadach, L. Kalinovskaya, Y. Kurihara, A. Leike, R. Mcpherson, M-N. Minard, G. Montagna, M. Moretti, T. Munehisa, O. Nicrosini, A. Olchevski, F. Piccinini , et al. (9 additional authors not shown)

Abstract: 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. On the ba… ▽ 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. On the basis of comparison of various calculations, theoretical uncertainties are estimated and compared with those needed for the final LEP2 data analysis. The subjects for the further studies are identified. △ Less

Submitted 17 July, 2000; originally announced July 2000.

Comments: 2-fermion working group report of the LEP2 Monte Carlo Workshop 1999/2000, 113 pages, 24 figures, 35 tables

Radiative corrections to e+e- --> f+f-

Authors: P. Christova, M. Jack, S. Riemann, T. Riemann

Abstract: 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 p… ▽ More 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. On the other hand, looking for such particles in direct production or other `New Physics' effects at energies between, for example, roughly 500 and 800 GeV will naturally be the main motivation to pursue the challenging endeavor of building and utilizing such a unique facility. These two scenarios for the LC shall be sketched here, with particular emphasis on the semi-analytical program ZFITTER for fermion-pair production in comparison with numerical programs like TOPAZ0, KK2f, and others. △ Less

Submitted 2 August, 2000; v1 submitted 4 February, 2000; originally announced February 2000.

Comments: 14 pages (Latex), 8 figures (Postscript), 1 table, uses sprocl_mod.sty (included), to appear in the Proceedings of the 2nd Joint ECFA/DESY Study on Physics and Detectors for a Linear Electron-Positron Collider, held at Orsay, Lund, Frascati, Oxford, and Obernai from April 1998 until Oct 1999, to appear as DESY report 123F, ``Physics Studies for a Future Linear Collider'' (R. Heuer, F. Richard, P. Zerwas, eds.); one statement corrected

Report number: LC-TH-2000-008

Z' indication from new APV data in Cesium and searches at linear colliders

Authors: R. Casalbuoni, S. De Curtis, D. Dominici, R. Gatto, S. Riemann

Abstract: 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. 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. △ Less

Submitted 20 January, 2000; originally announced January 2000.

Comments: 10 pages, 6 figures, Proceedings of the Second ECFA/DESY Study on Physics and Detectors for a Linear Electron - Positron Collider

Report number: LC-TH-2000-006

ZFITTER v.6.21 - A Semi-Analytical Program for Fermion Pair Production in e+e- Annihilation

Authors: D. Bardin, M. Bilenky, P. Christova, M. Jack, L. Kalinovskaya, A. Olchevski, S. Riemann, T. Riemann

Abstract: 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 reali… ▽ More 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. Complete O(alpha) weak loop corrections supplemented by selected higher-order terms may be included. The program calculates Delta r, the Z width, differential cross-sections, total cross-sections, integrated forward-backward asymmetries, left-right asymmetries, and for tau pair production also final-state polarization effects. Various interfaces allow fits to be performed with different sets of free parameters. △ Less

Submitted 1 March, 2000; v1 submitted 23 August, 1999; originally announced August 1999.

Comments: 200 pages, Latex2e, 26 figures, 4 tables; uses axodraw, epsfig, epsf, graphicx, espcrc1; typos of v.1 corrected, version for subm. to Comp. Phys. Commun

Report number: DESY 99-070

Journal ref: Comput.Phys.Commun. 133 (2001) 229-395

Predictions of ZFITTER v.6 for fermion-pair production with acollinearity cut

Authors: P. Christova, M. Jack, S. Riemann, T. Riemann

Abstract: 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 fermion… ▽ More 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. 6.11 compared to ZFITTER v. 5.20/21: (i) at the Z resonance -- numerical changes are negligible; (ii) at LEP 1 energies off-resonance -- corrections amount to at most few per mil; (iii) at LEP 2 energies -- corrections amount to one per cent or less. Thus, the predictions for LEP/SLC data remain unchanged within the actual errors. △ Less

Submitted 6 August, 1999; originally announced August 1999.

Comments: 28 pages, Latex2e, 16 figures, 8 tables; uses sprocl_mod.sty (included), rotating, epsfig, graphicx

Report number: DESY 99-037

Predictions for Fermion-Pair Production at LEP

Authors: P. Ch. Christova, M. Jack, S. Riemann, T. Riemann

Abstract: 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. 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. △ Less

Submitted 17 December, 1998; originally announced December 1998.

Comments: 9 pages, 1 table, 4 figures; LaTeX, uses sprocl.sty, epsfig; to appear in the Proceedings of the IVth International Symposium on Radiative Corrections (RADCOR98), Barcelona, Catalonia, Spain, 8-12 Sep 1998

Report number: DESY 98-184

ZZ' Mixing in Presence of Standard Weak Loop Corrections

Authors: A. Leike, S. Riemann, T. Riemann

Abstract: 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. Our theoretical results are applied to the package ZFITTER. We demonstrate two different ways to the data analysis… ▽ 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. Our theoretical results are applied to the package ZFITTER. We demonstrate two different ways to the data analysis - one based on an extension of the standard model cross sections, the other on model-independent formulae together with the Z width calculations in presence of a Z'. With the resulting package ZEFIT+ZFITTER, LEP1 data from fermion pair production, including Bhabha scattering, can be analysed on, but also off the Z peak. Further, the code may be used at very high energies, e.g. in the region of a possible future linear e+e- collider. △ Less

Submitted 20 August, 1998; originally announced August 1998.

Comments: Latex, 24 pages, a typo in eqs. 23,24 corrected

Report number: LMU-91/06 (Dec 1991)

Prospects to detect a Z' with the LC

Authors: S. Riemann

Abstract: 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. 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. △ Less

Submitted 31 October, 1997; originally announced October 1997.

Comments: 8 pages, LaTex, 10 figures. To be published in the proceedings of Joint ECFA / DESY Study: Physics and Detectors for a Linear Collider, Hamburg, Germany, 20-22 Nov 1996

Electroweak Working Group Report

Authors: D. Bardin, W. Beenakker, M. Bilenky, W. Hollik, M. Martinez, G. Montagna, O. Nicrosini, V. Novikov, L. Okun, A. Olshevsky, G. Passarino, F. Piccinini, S. Riemann, T. Riemann, A. Rozanov, F. Teubert, M. Vysotsky

Abstract: The report summarizes the results of the activities of the Working Group on Precision Calculations for the Z Resonance at CERN during 1994. The report summarizes the results of the activities of the Working Group on Precision Calculations for the Z Resonance at CERN during 1994. △ Less

Submitted 3 September, 1997; originally announced September 1997.

Comments: 158 Latex, including 37 figures (27 eps figures), 30 tables; The report is part of: D. Bardin, W. Hollik, G. Passarino (eds.), Reports of the working group on precision calculations for the Z resonance, CERN 95-03 (31 March 1995)

Study of Z' Couplings to Leptons and Quarks at NLC

Authors: S. Riemann

Abstract: 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. 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. △ Less

Submitted 28 October, 1996; originally announced October 1996.

Comments: 9 pages, LaTex, 9 figures. Talk given at 1996 DPF / DPB Summer Study on New Directions for High-energy Physics (Snowmass 96), Snowmass, CO, 25 Jun - 12 Jul 1996

Report number: DESY-Zeuthen 96-07

Journal ref: ECONF C960625:NEW141,1996

Z' Search in e+e- Annihilation

Authors: A. Leike, S. Riemann

Abstract: 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. However, if a Z' signal is observed, the discrimination between different models becomes much worse if systematic errors are taken into account. Disc… ▽ 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. However, if a Z' signal is observed, the discrimination between different models becomes much worse if systematic errors are taken into account. Discrimination between models is possible for M_{Z'} < 3 \sqrt{s}. A determination of Z' f \bar f couplings independently of models becomes attractive with future colliders. Anticipated bounds are determined. △ Less

Submitted 23 September, 1996; v1 submitted 14 July, 1996; originally announced July 1996.

Comments: 15 pages, LaTex, 11 figures, 3 tables; table 3 changed. Version to appear in Zeitschrift f. Physik C

Report number: DESY 96-111, LMU--02/96

Journal ref: Z.Phys. C75 (1997) 341-348

Z' Physics

Authors: P. Chiappetta, C. Verzegnassi, A. Fiandrino, J. Layssac, A. Leike, G. Montagna, O. Nicrosini, F. Piccinini, F. M. Renard, S. Riemann, D. Schaile

Abstract: 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. 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. △ Less

Submitted 3 May, 1996; originally announced May 1996.

Comments: 20 pages Latex, 7 figures included by epsfig, Contribution to the Proceedings the workshop "Physics at LEP2", Geneva, 1996

Z' Constraints from e+e- to f fbar at NLC

Authors: A. Leike, S. Riemann

Abstract: 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. A distinction between different GUT scenarios is possible if $M_{Z'}\le 3\sqrt{s}$. Radiative corrections give only smal… ▽ 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. A distinction between different GUT scenarios is possible if $M_{Z'}\le 3\sqrt{s}$. Radiative corrections give only small changes to the $Z'$ exclusion limits provided that appropriate cuts are applied. %The inclusion of systematic errors leads to slightly worse results for %$M_{Z'}^{lim}$. △ Less

Submitted 15 April, 1996; originally announced April 1996.

Comments: 7 pages, LaTex, 3 figures, 1 table, available from http://www.ifh.de/~riemanns/ or on request from e-mail: riemanns@ifh.de; to appear in: Proceedings of Physics with e+e- Linear Colliders Workshop, Annecy - Gran Sasso - Hamburg 1995

Report number: DESY-Zeuthen 96-06

ZZ' Mixing and Radiative Corrections at LEP I

Authors: Arnd Leike, Sabine Riemann, Tord Riemann

Abstract: 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 $γ,\ Z,$ and $Z'$ exchange. Weak corrections and $ZZ'$ mixing are treated simultaneously by a generalization of weak form factors. Using the properly extended Standard Model program… ▽ 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 $γ,\ Z,$ and $Z'$ exchange. Weak corrections and $ZZ'$ mixing are treated simultaneously by a generalization of weak form factors. Using the properly extended Standard Model program for the $Z$ line shape, ZFITTER, we perform and compare two different analyses of the 1990 LEP~I data in terms of theories based on the E$_6$-group and in terms of LR-symmetric models. From the LEP~I data alone, the $ZZ'$ mixing angle may be limited to $|θ_M| \le 0.01$ and the $Z'$ mass to $M_2 > 118$--148 GeV, depending on the model (95\%~CL). △ Less

Submitted 27 July, 1995; originally announced July 1995.

Comments: 12 pages, LaTex, 4 figures, a uuencoded file containing the latex file and figures is available via anonymous ftp at ftp://ftp.ifh.de/pub/preprint/cernth92-6545.uu ; paper publ. in Phys. Lett. B291 (1992) 187

Report number: CERN-TH.6545/92

Journal ref: Phys.Lett. B291 (1992) 187-194

ZFITTER -- An Analytical Program for Fermion Pair Production in e+e- Annihilation

Authors: D. Bardin, M. Bilenky, A. Chizhov, O. Fedorenko, S. Ganguli, A. Gurtu, M. Lokajicek, G. Mitselmakher, A. Olshevsky, J. Ridky, S. Riemann, T. Riemann, M. Sachwitz, A. Sazonov, A. D. Schaile, Yu. Sedykh, I. Sheer, L. Vertogradov

Abstract: 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 ${\cal O}(α)$ 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… ▽ 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 ${\cal O}(α)$ 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. One includes complete ${\cal O}(α)$ weak loop corrections with a resummation of leading higher-order terms. Alternatively, an ansatz inspired from S-matrix theory, or several model-independent effective Born cross sections may be convoluted. The program calculates cross sections, forward-backward asymmetries, and for $τ$~pair production also the final-state polarization. Various {\bf interfaces} allow fits to be performed with different sets of free parameters. △ Less

Submitted 29 September, 1995; v1 submitted 1 December, 1994; originally announced December 1994.

Comments: 76 pages (LaTeX), 19 figures, 12 tables, files containing the LaTeX text and the figures are available via anonymous ftp at ftp://ftp.ifh.de/pub/preprint/cernth92-6443.uu and the ps file from http://www.ifh.de/~riemann/ New submission for inclusion of figures. No changes of the paper