5,096 research outputs found
Photon production at the interaction point of the ILC
The intense beam-beam effect at the interaction point of the International
Linear Collider (ILC) causes large disruption of the beams and the production
of photons. These photons, arising dominantly through beamstrahlung emission,
are problematic for the machine design as they need to be transported and
dumped in a controlled way. In this work, we perform simulations of the
beam-beam interaction to predict photon production rates and distributions for
the different beam parameters considered at ILC. The results are expressed in
terms of a set of cones of excluded power, allowing to define the
beam-stay-clear requirements relevant for different cases and contexts. A
comparison is also made with theoretical expectations. The suggested photon
cone half-opening angles are 0.75 and 0.85 mrad in the horizontal and vertical
planes, respectively. These cones cover all machine energies and parameter
sets, and include the low power Compton photons
Theory and phenomenology of non-global logarithms
We discuss the theoretical treatment of non-global observables, those
quantities that are sensitive only to radiation in a restricted region of phase
space, and describe how large `non-global' logarithms arise when we veto the
energy flowing into the restricted region. The phenomenological impact of
non-global logarithms is then discussed, drawing on examples from event shapes
in DIS and energy-flow observables in 2-jet systems. We then describe
techniques to reduce the numerical importance of non-global logarithms, looking
at clustering algorithms in energy flow observables and the study of associated
distribution of multiple observables.Comment: Based on talks presented at the XXXVIIIth Rencontres de Moriond 'QCD
and high-energy hadronic interactions', 8 page
A simple construction of complex equiangular lines
A set of vectors of equal norm in represents equiangular lines
if the magnitudes of the inner product of every pair of distinct vectors in the
set are equal. The maximum size of such a set is , and it is conjectured
that sets of this maximum size exist in for every . We
describe a new construction for maximum-sized sets of equiangular lines,
exposing a previously unrecognized connection with Hadamard matrices. The
construction produces a maximum-sized set of equiangular lines in dimensions 2,
3 and 8.Comment: 11 pages; minor revisions and comments added in section 1 describing
a link to previously known results; correction to Theorem 1 and updates to
reference
Benchmarking of Tracking Codes (BDSIM/DIMAD) using the ILC Extraction Lines
The study of beam transport is of central importance to the design and
performance assessment of modern particle accelerators. In this work, we
benchmark two contemporary codes - DIMAD and BDSIM, the latter being a
relatively new tracking code built within the framework of GEANT4. We consider
both the 20 mrad and 2 mrad extraction lines of the International Linear
Collider (ILC) and we perform tracking studies of heavily disrupted
post-collision electron beams. We find that the two codes mostly give an
equivalent description of the beam transport.Comment: Contribution to the Tenth European Particle Accelerator Conference
`"EPAC'06'', Edinburgh, United-Kingdom, 26-30 June 200
Particle tracking in the ILC extraction lines with DIMAD and BDSIM
The study of beam transport is of central importance to the design and
performance assessment of modern particle accelerators. In this paper, we
benchmark two contemporary codes, DIMAD and BDSIM, the latter being a
relatively new tracking code built within the framework of GEANT4. We consider
both the 20 mrad and 2 mrad extraction lines of the 500 GeV International
Linear Collider (ILC) and we perform particle tracking studies of heavily
disrupted post-collision electron beams. We find that the two codes give an
almost equivalent description of the beam transport
Linking learning and everyday life: a social perspective on adult language, literacy and numeracy classses
Tensor Minkowski Functionals for random fields on the sphere
We generalize the translation invariant tensor-valued Minkowski Functionals
which are defined on two-dimensional flat space to the unit sphere. We apply
them to level sets of random fields. The contours enclosing boundaries of level
sets of random fields give a spatial distribution of random smooth closed
curves. We obtain analytic expressions for the ensemble expectation values for
the matrix elements of the tensor-valued Minkowski Functionals for isotropic
Gaussian and Rayleigh fields. We elucidate the way in which the elements of the
tensor Minkowski Functionals encode information about the nature and
statistical isotropy (or departure from isotropy) of the field. We then
implement our method to compute the tensor-valued Minkowski Functionals
numerically and demonstrate how they encode statistical anisotropy and
departure from Gaussianity by applying the method to maps of the Galactic
foreground emissions from the PLANCK data.Comment: 1+23 pages, 5 figures, Significantly expanded from version 1. To
appear in JCA
Optimization of the e-e- option for the ILC
The e-e- running mode is one of the interesting physics options at the
International Linear Collider (ILC). The luminosity for e-e- collisions is
reduced by the beam-beam effects. The resulting beamstrahlung energy loss and
beam-beam deflection angles as function of the vertical transverse offset are
different compared to the e+e- collisions. In this paper, the dependence of
these observables with the offset for different beam sizes has been analyzed to
optimize performances for the e-e- mode, taking into account the requirements
of the beam-beam deflection based intra-train feedback system. A first study of
the implications for the final focus and extraction line optics is also
presented for the cases of the 20 mrad and 2 mrad ILC base line crossing angle
geometries
On the interpretation of lateral manganin gauge stress measurements in polymers
Encapsulated wire-element stress gauges enable changes in lateral stress during
shock loading to be directly monitored. However, there is substantial debate
with regards to interpretation of observed changes in stress behind the shock
front; a phenomenon attributed both to changes in material strength and shock-
dispersion within the gauge-encapsulation. Here, a pair of novel techniques
which both modify or remove the embedding medium where such stress gauges are
placed within target materials have been used to try and inform this debate. The
behavior of three polymeric materials of differing complexity was considered,
namely polystyrene, the commercially important resin transfer moulding RTM 6
resin and a commercially available fat lard. Comparison to the response of
embedded gauges has suggested a possible slight decrease in the absolute
magnitude of stress. However, changing the encapsulation has no detectable
effect on the gradient behind the shock in such polymeric systems
Achievable Qubit Rates for Quantum Information Wires
Suppose Alice and Bob have access to two separated regions, respectively, of
a system of electrons moving in the presence of a regular one-dimensional
lattice of binding atoms. We consider the problem of communicating as much
quantum information, as measured by the qubit rate, through this quantum
information wire as possible. We describe a protocol whereby Alice and Bob can
achieve a qubit rate for these systems which is proportional to N^(-1/3) qubits
per unit time, where N is the number of lattice sites. Our protocol also
functions equally in the presence of interactions modelled via the t-J and
Hubbard models
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