The first stage of the FCC (Future Circular Collider) is a high-luminosity electron-positron collider (FCC-ee) with centre-of-mass energy ranging from 88 to 365 GeV, to study with high precision the ...Z, W, Higgs and top particles, with samples of \(5 \times 10^{12}\) Z bosons, \(10^8\) W pairs, \(10^6\) Higgs bosons and \(10^6\) top quark pairs. A cornerstone of the physics program lays in the precise (ppm) measurements of the W and Z masses and widths, as well as forward-backward asymmetries. To this effect the centre-of-mass energy distribution should be determined with the high precision. This document describes the capacity offered by FCC-ee, starting with transverse polarization of the beams around the Z pole and the W pair threshold. A running scheme based on regular measurements of the beam energy by resonant depolarization of pilot bunches, during physics data taking, is proposed. The design for polarization wigglers, polarimeter and depolarizer is outlined. The \(e^\pm\) beam energies will be monitored with a relative precision of \(10^{-6}\). The centre-of-mass energy is derived subject to further corrections, related to the beam acceleration, synchrotron radiation and beamstrahlung; these effects are identified and evaluated. Dimuon events \(e^+e^- \to \mu^+ \mu^-\), recorded in the detectors, provide with great precision the beam crossing angle, the centre-of-mass energy spread, and the \(e^+\) and \(e^-\) energy difference. Monitoring methods to minimize absolute error and relative uncertainties are discussed. The impact on the physics measurements is given. A programme of further simulations, design, monitoring and R&D is outlined.
Status and Challenges for FCC-ee Benedikt, Michael; Oide, Katsunobu; Zimmermann, Frank ...
arXiv (Cornell University),
08/2015
Paper, Journal Article
Odprti dostop
We report the design status and beam dynamics challenges for the electron-positron branch of the Future Circular Collider (FCC) study, as of August 2015. After recalling motivation and physics ...requirements for the FCC-ee, we briefly discuss configurations and parameters, collider layout, the superconducting RF system, possible staging scenarios, final-focus optics, interaction-region (IR) issues, machine detector interface and IR synchrotron radiation, dynamic aperture, beam-beam effects, top-up injection, mono-chromatization option, impedances, instabilities, energy calibration and polarization, and SuperKEKB as a key demonstrator, before presenting conclusions and outlook.
JACoW Publishing (2018) The international Future Circular Collider (FCC) study aims at a design of
$pp$, $e^+e^-$, $ep$ colliders to be built in a new 100 km tunnel in the Geneva
region. The $e^+e^-$ ...collider (FCC-ee) has a centre of mass energy range
between 90 (Z-pole) and 375 GeV (tt_bar). To reach such unprecedented energies
and luminosities, the design of the interaction region is crucial. The
crab-waist collision scheme has been chosen for the design and it will be
compatible with all beam energies. In this paper we will describe the machine
detector interface layout including the solenoid compensation scheme. We will
describe how this layout fulfills all the requirements set by the parameters
table and by the physical constraints. We will summarize the studies of the
impact of the synchrotron radiation, the analysis of trapped modes and of the
backgrounds induced by single beam and luminosity effects giving an estimate of
the losses in the interaction region and in the detector.
This document answers in simple terms many FAQs about FCC-ee, including comparisons with other colliders. It complements the FCC-ee CDR and the FCC Physics CDR by addressing many questions from ...non-experts and clarifying issues raised during the European Strategy symposium in Granada, with a view to informing discussions in the period between now and the final endorsement by the CERN Council in 2020 of the European Strategy Group recommendations. This document will be regularly updated as more questions appear or new information becomes available.
The international Future Circular Collider (FCC) study aims at a design of \(pp\), \(e^+e^-\), \(ep\) colliders to be built in a new 100 km tunnel in the Geneva region. The \(e^+e^-\) collider ...(FCC-ee) has a centre of mass energy range between 90 (Z-pole) and 375 GeV (tt_bar). To reach such unprecedented energies and luminosities, the design of the interaction region is crucial. The crab-waist collision scheme has been chosen for the design and it will be compatible with all beam energies. In this paper we will describe the machine detector interface layout including the solenoid compensation scheme. We will describe how this layout fulfills all the requirements set by the parameters table and by the physical constraints. We will summarize the studies of the impact of the synchrotron radiation, the analysis of trapped modes and of the backgrounds induced by single beam and luminosity effects giving an estimate of the losses in the interaction region and in the detector.
The author examines a procedure to correct various initial machine errors, using the JLC final focus system as an example. A simulation shows that the combination of alignment by the beam method and ...linear knobs is a possible tuning method for the start-up of the final focus system. It allows a conventional level of initial alignment of the magnets, setting errors and sensitivity of position monitors. It also has to rely on the spot size monitor at the interaction point and the accuracy and the stability of the magnet movers. It is not necessary for the magnet movers to be able to set the position in the submicron accuracy, because one can use a correction dipole instead of such a small displacement of a quadrupole. In the simulation, about 400 pulses were used to tune up the entire beam line. Since the linear collider has a few hundred Hz repetition rate, the actual speed of the tuning is limited by the response of the movers and the monitors. This means that, in the actual situation, one can use more pulses to determine the displacement of the magnets and the minimum search than in the simulation. Therefore, the accuracy of the method may become even better than the simulation.< >
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