70 research outputs found
Near-threshold production of , and at a fixed-target experiment at the future ultra-high-energy proton colliders
We outline the opportunities to study the production of the Standard Model
bosons, , and at "low" energies at fixed-target experiments
based at possible future ultra-high-energy proton colliders, \ie\ the
High-Energy LHC, the Super proton-proton Collider and the Future Circular
Collider -- hadron-hadron. These can be indeed made in conjunction with the
proposed future colliders designed to reach up to TeV by using
bent crystals to extract part of the halo of the beam which would then impinge
on a fixed target. Without disturbing the collider operation, this technique
allows for the extraction of a substantial amount of particles in addition to
serve for a beam-cleaning purpose. With this method, high-luminosity
fixed-target studies at centre-of-mass energies above the , and
masses, GeV, are possible. We also discuss the
possibility offered by an internal gas target, which can also be used as
luminosity monitor by studying the beam transverse shape
Investigation of classical radiation reaction with aligned crystals
Classical radiation reaction is the effect of the electromagnetic field
emitted by an accelerated electric charge on the motion of the charge itself.
The self-consistent underlying classical equation of motion including
radiation-reaction effects, the Landau-Lifshitz equation, has never been tested
experimentally, in spite of the first theoretical treatments of radiation
reaction having been developed more than a century ago. Here we show that
classical radiation reaction effects, in particular those due to the near
electromagnetic field, as predicted by the Landau-Lifshitz equation, can be
measured in principle using presently available facilities, in the energy
emission spectrum of electrons crossing a
- thick diamond crystal in the axial channeling regime. Our
theoretical results indicate the feasibility of the suggested setup, e.g., at
the CERN Secondary Beam Areas (SBA) beamlines.Comment: 8 pages, 5 figure
X-ray emission from a crystal undulatorâExperimental results at channeling of electrons
Experiments have been performed at the Mainz Microtron MAMI
to explore the radiation emission from a 4-period epitaxially grown strained layer Si1âxGex undulator with a period length λu = 9.9 ÎŒm. Electron energies of 270 and
855MeV have been chosen. In comparison with a flat silicon reference crystal, a broad excess yield around the theoretically expected photon energies of 0.069 and 0.637 MeV, respectively, has been observed for channeling at the undulating (110) planes. The results are discussed within the framework of the classical undulator theory
Near-Threshold Production of ± , 0 , and 0 at a Fixed-Target Experiment at the Future Ultrahigh-Energy Proton Colliders
We outline the opportunities to study the production of the Standard Model bosons, ± , 0 , and 0 , at "low" energies at fixed-target experiments based on possible future ultrahigh-energy proton colliders, that is, the High-Energy LHC, the Super proton-proton Collider, and the Future Circular Collider hadron-hadron. These can be indeed made in conjunction with the proposed future colliders designed to reach up to â = 100 TeV by using bent crystals to extract part of the halo of the beam which would then impinge on a fixed target. Without disturbing the collider operation, this technique allows for the extraction of a substantial amount of particles in addition to serving for a beam-cleaning purpose. With this method, high-luminosity fixed-target studies at centreof-mass energies above the ± , 0 , and 0 masses, â â 170-300 GeV, are possible. We also discuss the possibility offered by an internal gas target, which can also be used as luminosity monitor by studying the beam transverse shape
Experimental investigation of the Landau-Pomeranchuk-Migdal effect in low-Z targets
In the CERN NA63 collaboration we have addressed the question of the
potential inadequacy of the commonly used Migdal formulation of the
Landau-Pomeranchuk-Migdal (LPM) effect by measuring the photon emission by 20
and 178 GeV electrons in the range 100 MeV - 4 GeV, in targets of
LowDensityPolyEthylene (LDPE), C, Al, Ti, Fe, Cu, Mo and, as a reference
target, Ta. For each target and energy, a comparison between simulated values
based on the LPM suppression of incoherent bremsstrahlung is shown, taking
multi-photon effects into account. For these targets and energies, we find that
Migdal's theoretical formulation is adequate to a precision of better than
about 5%, irrespective of the target substance.Comment: 8 pages, 13 figure
A Fixed-Target ExpeRiment at the LHC (AFTER@LHC) : luminosities, target polarisation and a selection of physics studies
We report on a future multi-purpose fixed-target experiment with the proton
or lead ion LHC beams extracted by a bent crystal. The multi-TeV LHC beams
allow for the most energetic fixed-target experiments ever performed. Such an
experiment, tentatively named AFTER for "A Fixed-Target ExperRiment", gives
access to new domains of particle and nuclear physics complementing that of
collider experiments, in particular at RHIC and at the EIC projects. The
instantaneous luminosity at AFTER using typical targets surpasses that of RHIC
by more than 3 orders of magnitude. Beam extraction by a bent crystal offers an
ideal way to obtain a clean and very collimated high-energy beam, without
decreasing the performance of the LHC. The fixed-target mode also has the
advantage of allowing for spin measurements with a polarised target and for an
access over the full backward rapidity domain up to xF ~ - 1. Here, we
elaborate on the reachable luminosities, the target polarisation and a
selection of measurements with hydrogen and deuterium targets.Comment: 6 pages. Proceedings of the Sixth International Conference on Quarks
and Nuclear Physics QNP2012 (16-20 April 2012, Ecole Polytechnique,
Palaiseau,France
Experimental investigations of synchrotron radiation at the onset of the quantum regime
The classical description of synchrotron radiation fails at large Lorentz
factors, , for relativistic electrons crossing strong transverse
magnetic fields . In the rest frame of the electron this field is comparable
to the so-called critical field T. For quantum corrections are essential for the description of
synchrotron radiation to conserve energy. With electrons of energies 10-150 GeV
penetrating a germanium single crystal along the axis, we have
experimentally investigated the transition from the regime where classical
synchrotron radiation is an adequate description, to the regime where the
emission drastically changes character; not only in magnitude, but also in
spectral shape. The spectrum can only be described by quantum synchrotron
radiation formulas. Apart from being a test of strong-field quantum
electrodynamics, the experimental results are also relevant for the design of
future linear colliders where beamstrahlung - a closely related process - may
limit the achievable luminosity.Comment: 11 pages, 18 figures, submitted to PR
- âŠ