4,147 research outputs found
Physics opportunities with future proton accelerators at CERN
We analyze the physics opportunities that would be made possible by upgrades
of CERN's proton accelerator complex. These include the new physics possible
with luminosity or energy upgrades of the LHC, options for a possible future
neutrino complex at CERN, and opportunities in other physics including rare
kaon decays, other fixed-target experiments, nuclear physics and antiproton
physics, among other possibilities. We stress the importance of inputs from
initial LHC running and planned neutrino experiments, and summarize the
principal detector R&D issues.Comment: 39 page, word document, full resolution version available from
http://cern.ch/pofpa/POFPA-arXive.pd
Energy versus information based estimations of dissipation using a pair of magnetic colloidal particles
Using the framework of stochastic thermodynamics, we present an experimental
study of a doublet of magnetic colloidal particles which is manipulated by a
time-dependent magnetic field. Due to hydrodynamic interactions, each bead
experiences a state-dependent friction, which we characterize using a
hydrodynamic model. In this work, we compare two estimates of the dissipation
in this system: the first one is energy based since it relies on the measured
interaction potential, while the second one is information based since it uses
only the information content of the trajectories. While the latter only offers
a lower bound of the former, we find it to be simple to implement and of
general applicability to more complex systems.Comment: Main text: 5 pages, 4 figures. Supplementary material: 5 pages, 5
figure
Reachability problems for PAMs
Piecewise affine maps (PAMs) are frequently used as a reference model to show
the openness of the reachability questions in other systems. The reachability
problem for one-dimentional PAM is still open even if we define it with only
two intervals. As the main contribution of this paper we introduce new
techniques for solving reachability problems based on p-adic norms and weights
as well as showing decidability for two classes of maps. Then we show the
connections between topological properties for PAM's orbits, reachability
problems and representation of numbers in a rational base system. Finally we
show a particular instance where the uniform distribution of the original orbit
may not remain uniform or even dense after making regular shifts and taking a
fractional part in that sequence.Comment: 16 page
Three-photon detachment of electrons from the fluorine negative ion
Absolute three-photon detachment cross sections are calculated for the
fluorine negative ion within the lowest-order perturbation theory. The Dyson
equation of the atomic many-body theory is used to obtain the ground-state 2p
wavefunction with correct asymptotic behaviour, corresponding to the true
(experimental) binding energy. We show that in accordance with the adiabatic
theory (Gribakin and Kuchiev 1997 {Phys. Rev. A} {\bf 55} 3760) this is crucial
for obtaining absolute values of the multiphoton cross sections. Comparisons
with other calculations and experimental data are presented.Comment: 10 pages, two figures, Latex, IOP styl
Longitudinal Polarization at future Colliders and Virtual New Physics Effects
The theoretical merits of longitudinal polarization asymmetries of
electron-positron annihilation into two final fermions at future colliders are
examined, using a recently proposed theoretical description. A number of
interesting features, valid for searches of virtual effects of new physics, is
underlined, that is reminiscent of analogous properties valid on top of
resonance. As an application to a concrete example, we consider the case of a
model with triple anomalous gauge couplings and show that the additional
information provided by these asymmetries would lead to a drastic reduction of
the allowed domain of the relevant parameters.Comment: 18 pages and 1 figure. e-mail: [email protected]
Weakly coupled neutral gauge bosons at future linear colliders
A weakly coupled new neutral gauge boson forms a narrow resonance that is
hard to discover directly in e+e- collisions. However, if the gauge boson mass
is below the center-of-mass energy, it can be produced through processes where
the effective energy is reduced due to initial-state radiation and
beamstrahlung. It is shown that at a high-luminosity linear collider, such a
gauge boson can be searched for with very high sensitivity, leading to a
substantial improvement compared to existing limits from the Tevatron and also
extending beyond the expected reach of the LHC in most models. If a new vector
boson is discovered either at the Tevatron Run II, the LHC or the linear
collider, its properties can be determined at the linear collider with high
precision, thus helping to reveal origin of the new boson.Comment: 21 p
Role of CD8 T cell subsets in the pathogenesis of multiple sclerosis
AbstractMultiple sclerosis (MS) is an immune-mediated disease of the central nervous system leading to demyelination and axonal/neuronal loss. Cumulating evidence points to a key role for CD8 T cells in this disabling disease. Oligoclonal CD8 T cells reside in demyelinating plaques where they are likely to contribute to tissue destruction. Histopathological analyses and compelling observations from animal models indicate that cytotoxic CD8 T cells target neural cell populations with the potential of causing lesions reminiscent of MS. However, CD8 T cell differentiation results in several subsets of effector CD8 T cells that could be differentially implicated in the mechanisms contributing to tissue damage. Moreover CD8 regulatory T cells arise as important populations involved in restoring immune homoeostasis and in maintaining immune privileged sites. Here we examine the current literature pertaining to the role of CD8 effector and regulatory T cell subsets in the pathogenesis of MS
Top quark production at future lepton colliders in the asymptotic regime
The production of a tt(bar) pair from lepton-antilepton annihilation is
considered for values of the center of mass energy much larger than the top
mass, typically of the few TeV size. In this regime a number of simplifications
occurs that allows to derive the leading asymptotic terms of various
observables using the same theoretical description that was used for light
quark production. Explicit examples are shown for the Standard Model and the
Minimal Supersymmetric Standard Model cases.Comment: 20 pages and 13 figures. e-mail: [email protected]
A geomorphological investigation of lateral spreading and translational sliding within the Storegga Slide
Lateral spreading and translational sliding are two of the most prevalent types of slope
failures within the Storegga Slide. This has been concluded from a thorough analysis
of three acoustic data sets from the Storegga Slide complex â high-resolution multibeam
bathymetry, TOBI sidescan sonar imagery and 3D seismic data.We have applied
quantitative geomorphometric techniques to the bathymetry data set and analysed the
texture of sidescan sonar images using Grey-Level Occurrence Matrices (GLCMs).
Both techniques have been shown to improve the geological interpretation of submarine
environments (e.g. Micallef et al., 2006), and allowed an objective characterisation
of the slide surface to be carried out. These results were then combined with
the interpretation of the seismic data set and all the geological information currently
available for Storegga in the literature. In this way we were able to define the types
and boundaries of the different styles of mass movements, and represent them on a
geomorphological map. Further insight is provided into the origin and the mode of
failure of lateral spreading and translational sliding. Finally we attempt to describe
the characteristic morphology of lateral spreading and demonstrate that it is a very
common slope failure process in the Norwegian margin.peer-reviewe
Reconciling the LEP and Slac Measurements of Sin^2(\Theta_W)
We consider whether a discrepancy between the SLAC and LEP measurements of
\Sw can be explained by new physics. We find that only the contribution of a
new neutral gauge boson, , nearly degenerate with the Z can affect
the SLAC measurement while leaving the LEP observables almost unaffected. We
briefly discuss possible signals for this new gauge boson, including changes in
the lineshape when measured with polarised electrons, small changes in
, , and larger changes in two jet and production at
hadron colliders.Comment: 8 pages , CERN-TH.7474/94, OUTP9424
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