488 research outputs found
Quantum excitation-free radiation emission including multiple scattering
In order to increase the luminosity of electron-positron colliders it is
desirable to find a means to reduce the phase-space of the beams. The
transverse cooling of positrons imposed by the quantum excitation-free
radiation emission in a single crystal is considered as a potential route to
achieving ultra-cold beams. An analysis of the problem is presented, including
an evaluation of the contribution from multiple scattering during the passage.
The analysis shows that an emittance reduction may be achieved in special
cases, but in general the emittance will increase as a result of the multiple
scattering.Comment: Presented at the 3rd Workshop on Quantum Aspects of Beam Physics,
Hiroshima 200
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
Bremsstrahlung from relativistic heavy ions in a fixed target experiment at the LHC
We calculate the emission of bremsstrahlung from lead and argon ions in A
Fixed Target ExpeRiment (AFTER) that uses the LHC beams. With nuclear charges
of equal and respectively, these ions are accelerated to
energies of TeV. The bremsstrahlung peaks around
GeV and the spectrum exposes the nuclear structure of the incoming ion. The
peak structure is significantly different from the flat power spectrum
pertaining to a point charge. Photons are predominantly emitted within an angle
of to the direction of ion propagation. Our calculations are based
on the Weizs\"{a}cker-Williams method of virtual quanta with application of
existing experimental data on photonuclear interactions.Comment: 9 pages, 3 figures. Submitted to Advances in High Energy Physic
Characteristics of Cherenkov Radiation in Naturally Occuring Ice
We revisit the theory of Cherenkov radiation in uniaxial crystals.
Historically, a number of flawed attempts have been made at explaining this
radiation phenomenon and a consistent error-free description is nowhere
available. We apply our calculation to a large modern day telescope - IceCube.
Being located at the Antarctica, this detector makes use of the naturally
occuring ice as a medium to generate Cherenkov radiation. However, due to the
high pressure at the depth of the detector site, large volumes of hexagonal ice
crystals are formed. We calculate how this affects the Cherenkov radiation
yield and angular dependence. We conclude that the effect is small, at most
about a percent, and would only be relevant in future high precision
instruments like e.g. Precision IceCube Next Generation Upgrade (PINGU). For
radio-Cherenkov experiments which use the presence of a clear Cherenkov cone to
determine the arrival direction, any variation in emission angle will directly
and linearly translate into a change in apparent neutrino direction. In
closing, we also describe a simple experiment to test this formalism, and
calculate the impact of anisotropy on light-yields from lead tungstate crystals
as used, for example, in the CMS calorimeter at the CERN LHC
Praksisforskning: nĂĽr forskning, kundskabsproduktion og faglig udvikling forenes
The article describes the background and need for developing and initiating practice research in social work â including the possibility of connecting research, learning processes and knowledge production in practice. Furthermore, the possibilities of utilizing the knowledge, developed, but seldom made explicit, in practice, and the possibility of producing societal impact are described. Practice research is diverse, because it is negotiated by different stakeholders when launched. The article suggests a scientific position, a definition and a description of different approaches within practice research, which may support negotiations and discussions of practice research â among researchers and within collaborations between research and practice. 
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