808 research outputs found
TLEP, first step in a long-term vision for HEP
The discovery of H(126) has renewed interest in circular e+e- colliders that
can operate as Higgs factories, which benefit from three unique
characteristics: i) high luminosity and reliability, ii) the availability of
several interaction points, iii) superior beam energy accuracy. TLEP is an e+e-
storage ring of 80-km circumference that can operate with very high luminosity
from the Z peak (90 GeV) to the top quark pair threshold (350 GeV). It can
achieve transverse beam polarization at the Z peak and WW threshold, giving it
unparalleled accuracy on the beam energy. A preliminary study indicates that an
80 km tunnel could be constructed around CERN. Such a tunnel would allow a 100
TeV proton-proton collider to be established in the same ring (VHE-LHC),
offering a long term vision.Comment: This is a contribution to the the Snowmass process 2013: Frontier
Capabilitie
The FCC-ee Interaction Region Magnet Design
The design of the region close to the interaction point of the FCC-ee
experiments is especially challenging. The beams collide at an angle (+-15
mrad) in the high-field region of the detector solenoid. Moreover, the very low
vertical beta_y* of the machine necessitates that the final focusing
quadrupoles have a distance from the IP (L*) of around 2 m and therefore are
inside the main detector solenoid. The beams should be screened from the effect
of the detector magnetic field, and the emittance blow-up due to vertical
dispersion in the interaction region should be minimized, while leaving enough
space for detector components. Crosstalk between the two final focus
quadrupoles, only about 6 cm apart at the tip, should also be minimized.Comment: Poster presented at IPAC16, May 8-13, Busan, Kore
Comments on "Wall-plug (AC) power consumption of a very high energy e+/e- storage ring collider" by Marc Ross
The paper arXiv:1308.0735 questions some of the technical assumptions made by
the TLEP Steering Group when estimating in arXiv:1305.6498 the power
requirement for the very high energy e+e- storage ring collider TLEP. We show
that our assumptions are based solidly on CERN experience with LEP and the LHC,
as well accelerators elsewhere, and confirm our earlier baseline estimate of
the TLEP power consumption.Comment: 6 page
FCC-ee: Energy calibration
The FCC-ee aims to improve on electroweak precision measurements, with goals
of 100 keV on the Z mass and width, and a fraction of MeV on the W mass.
Compared to LEP, this implies a much improved knowledge of the centre-of-mass
energy when operating at the Z peak and WW threshold. This can be achieved by
making systematic use of resonant depolarization. A number of issues have been
identified, due in particular to the long polarization times. However the
smaller emittance and energy spread of FCC-ee with respect to LEP should help
achieve a much improved performance.Comment: Poster presented at IPAC'15, Richmond, VA, USA, May 2015. arXiv admin
note: substantial text overlap with arXiv:1501.0685
TLEP: A High-Performance Circular e+e- Collider to Study the Higgs Boson
The recent discovery of a light Higgs boson has opened up considerable
interest in circular e+e- Higgs factories around the world. We report on the
progress of the TLEP concept since last year. TLEP is an e+e- circular collider
capable of very high luminosities in a wide centre-of-mass (ECM) spectrum from
90 to 350 GeV. TLEP could be housed in a new 80 to 100 km tunnel in the Geneva
region. The design can be adapted to different ring circumference (e.g. LEP3 in
the 27 km LHC tunnel). TLEP is an ideal complementary machine to the LHC thanks
to high luminosity, exquisite determination of ECM and the possibility of four
interaction points, both for precision measurements of the Higgs boson
properties and for precision tests of the closure of the Standard Model from
the Z pole to the top threshold.Comment: Contribution to IPAC13, 12-17 May 2013, Shanghai, Chin
Constraints on Quartic Vector-Boson Interactions from Z Physics
We obtain the constraints on possible anomalous quartic vector-boson vertices
arising from the precision measurements at the pole. In the framework of
chiral Lagrangians, we examine all effective operators
of order that lead to four-gauge-boson interactions but do not induce
anomalous trilinear vertices. We constrain the anomalous quartic interactions
by evaluating their one-loop corrections to the pole physics. Our analysis
is performed in a generic gauge and it shows that only the operators
that break the custodial symmetry get limits close to the theoretical
expectations. Our results also indicate that these anomalous couplings are
already out of reach of the Next Linear Collider, while the Large
Hadron Collider could be able to further extend the bounds on some of these
couplings.Comment: 16 pages, 1 Postscript figures, uses RevTex and eps.st
The Influence of Train Leakage Currents on the LEP Dipole Field
The determination of the mass and the width of the Z boson at CERN's LEP accelerator, an e+e- storage ring with a circumference of approximately 27 kilometres, imposes heavy demands on the knowledge of the LEP counter-rotating electron and positron beam energies. The precision required is of the order of 1 MeV or »20 ppm frequency. Due to its size the LEP collider is influenced by various macroscopic and regional factors such as the position of the moon or seasonal changes of the rainfall in the area, as reported earlier. A new and not less surprising effect of the LEP energy was observed in 1995: railroad trains in the Geneva region perturb the dipole field. A parasitic flow of electricity, originating from the trains, travels along the LEP ground cable and the vacuum chamber, interacting with the dipole field. An account of the phenomenon with its explanation substantiated by dedicated measurements is presented
A newly observed Effect affects the LEP Beam Energy
The LEP magnetic bending field and therefore the beam energy is changed by a current flow over the vacuum chamber. The current is created by trains travelling between the Geneva main station and destinations in France. Some of the rail current leaks into earth and returns to the power station via the LEP tunnel, where the vacuum chamber is one of the conductors. Train leakage currents penetrate LEP at the injection lines from the SPS close to IP1 and between IP5 and IP7, thereby interacting with the magnetic dipole field. The observed changes in B field cause beam energy increases of several MeV
Evaluation of the LEP Centre-of-Mass Energy Above the W-Pair Production Threshold
Knowledge of the centre-of-mass energy at LEP2 is of primary importance to
set the absolute energy scale for the measurement of the W-boson mass. The beam
energy above 80 GeV is derived from continuous measurements of the magnetic
bending field by 16 NMR probes situated in a number of the LEP dipoles. The
relationship between the fields measured by the probes and the beam energy is
calibrated against precise measurements of the average beam energy between 41
and 55 GeV made using the resonant depolarisation technique. The linearity of
the relationship is tested by comparing the fields measured by the probes with
the total bending field measured by a flux loop. This test results in the
largest contribution to the systematic uncertainty. Several further corrections
are applied to derive the the centre-of-mass energies at each interaction
point. In addition the centre-of-mass energy spread is evaluated. The beam
energy has been determined with a precision of 25 MeV for the data taken in
1997, corresponding to a relative precision of 2.7x10^{-4}. This is small in
comparison to the present uncertainty on the W mass measurement at LEP.
However, the ultimate statistical precision on the W mass with the full LEP2
data sample should be around 25 MeV, and a smaller uncertainty on the beam
energy is desirable. Prospects for improvements are outlined.Comment: 24 pages, 10 figures, Latex, epsfig; replaced by version accepted by
European Physical Journal
Design of beam optics for the Future Circular Collider e+e- -collider rings
A beam optics scheme has been designed for the Future Circular Collider-e+e-
(FCC-ee). The main characteristics of the design are: beam energy 45 to 175
GeV, 100 km circumference with two interaction points (IPs) per ring,
horizontal crossing angle of 30 mrad at the IP and the crab-waist scheme [1]
with local chromaticity correction. The crab-waist scheme is implemented within
the local chromaticity correction system without additional sextupoles, by
reducing the strength of one of the two sextupoles for vertical chromatic
correction at each side of the IP. So-called "tapering" of the magnets is
applied, which scales all fields of the magnets according to the local beam
energy to compensate for the effect of synchrotron radiation (SR) loss along
the ring. An asymmetric layout near the interaction region reduces the critical
energy of SR photons on the incoming side of the IP to values below 100 keV,
while matching the geometry to the beam line of the FCC proton collider
(FCC-hh) [2] as closely as possible. Sufficient transverse/longitudinal dynamic
aperture (DA) has been obtained, including major dynamical effects, to assure
an adequate beam lifetime in the presence of beamstrahlung and top-up
injection. In particular, a momentum acceptance larger than +/-2% has been
obtained, which is better than the momentum acceptance of typical collider
rings by about a factor of 2. The effects of the detector solenoids including
their compensation elements are taken into account as well as synchrotron
radiation in all magnets. The optics presented in this paper is a step toward a
full conceptual design for the collider. A number of issues have been
identified for further study
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