124,628 research outputs found
Electroweak precision measurements and collider probes of the Standard Model with large extra dimensions
The elementary particles of the Standard Model may live in more than 3+1
dimensions. We study the consequences of large compactified dimensions on
scattering and decay observables at high-energy colliders. Our analysis
includes global fits to electroweak precision data, indirect tests at
high-energy electron-positron colliders (LEP2 and NLC), and direct probes of
the Kaluza-Klein resonances at hadron colliders (Tevatron and LHC). The present
limits depend sensitively on the Higgs sector, both the mass of the Higgs boson
and how many dimensions it feels. If the Higgs boson is trapped on a 3+1
dimensional wall with the fermions, large Higgs masses (up to 500 GeV) and
relatively light Kaluza-Klein mass scales (less than 4 TeV) can provide a good
fit to precision data. That is, a light Higgs boson is not necessary to fit the
electroweak precision data, as it is in the Standard Model. If the Higgs boson
propagates in higher dimensions, precision data prefer a light Higgs boson
(less than 260 GeV), and a higher compactification scale (greater than 3.8
TeV). Future colliders can probe much larger scales. For example, a 1.5 TeV
electron-positron linear collider can indirectly discover Kaluza-Klein
excitations up to 31 TeV if 500 fb^-1 integrated luminosity is obtained.Comment: 29 pages, LaTe
Adjunct hexagonal array token Petri nets and hexagonal picture languages
Adjunct Hexagonal Array Token Petri Net Structures (AHPN) are re-
cently introduced hexagonal picture generating devices which extended the Hexag- onal Array Token Petri Net Structures . In this paper we consider AHPN model along with a control feature called inhibitor arcs and compare it with some ex- pressive hexagonal picture generating and recognizing models with respect to the
generating power
Duality Symmetries and Supersymmetry Breaking in String Compactifications
We discuss the spontaneous supersymetry breaking within the low-energy
effective supergravity action of four-dimensional superstrings. In particular,
we emphasize the non-universality of the soft supersymmetry breaking
parameters, the -problem and the duality symmetries.Comment: (invited talk to the 27th ICHEP, Glasgow, July 1994), 11 page
Kinetic Theory of Flocking: Derivation of Hydrodynamic Equations
It is shown how to explicitly coarse-grain the microscopic dynamics of the
Vicsek model for self-propelled agents. The macroscopic transport equations are
derived by means of an Enskog-type kinetic theory. Expressions for all
transport coefficients at large particle speed are given. The phase transition
from a disordered to a flocking state is studied numerically and analytically.Comment: 4 pages, 1 figur
Large Nc Continuum Reduction and the Thermodynamics of QCD
It is noted that if large Nc continuum reduction applies to an observable,
then that observable is independent of temperature for all temperatures below
some critical value. This fact, plus the fact that mesons and glueballs are
weakly interacting at large Nc is used as the basis for a derivation of large
Nc continuum reduction for the chiral condensate. The structure of this
derivation is quite general and can be extended to a wide class of observables
Initial '80s Development of Inflated Antennas
State of the art technology was considered in the definition and documentation of a membrane surface suitable for use in a space reflector system for long durations in orbit. Requirements for a metal foil-plastic laminate structural element were determined and a laboratory model of a rigidized element to test for strength characteristics was constructed. Characteristics of antennas ranging from 10 meters to 1000 meters were determined. The basic antenna configuration studied consists of (1) a thin film reflector, (2) a thin film cone, (3) a self-rigidizing structural torus at the interface of the cone and reflector; and (4) an inflation system. The reflector is metallized and, when inflated, has a parabolic shape. The cone not only completes the enclosure of the inflatant, but also holds the antenna feed at its apex. The torus keeps the inflated cone-reflector from collapsing inward. Laser test equipment determined the accuracy of the inflated paraboloids
Possible Suppression of Resonant Signals for Split-UED by Mixing at the LHC?
The mixing of the imaginary parts of the transition amplitudes of nearby
resonances via the breakdown of the Breit-Wigner approximation has been shown
to lead to potentially large modifications in the signal rates for new physics
at colliders. In the case of suppression, this effect may be significant enough
to lead to some new physics signatures being initially missed in searches at,
e.g., the LHC. Here we explore the influence of this `width mixing' on the
production of the nearly degenerate, level-2 Kaluza-Klein (KK) neutral gauge
bosons present in Split-UED. We demonstrate that in this particular case large
cross section modifications in the resonance region are necessarily absent and
explain why this is so based on the group theoretical structure of the SM.Comment: 10 pages, 2 figures; discussion and references adde
Lidar measurements of thermal structure
Rayleigh backscatter observations at 532 nm and 355 nm of relative atmospheric density above Aberystwyth on a total of 93 nights between Dec. 1982 and Feb. 1985 were used to derive the height variation of temperature in the upper stratosphere and mesosphere. Preliminary results for height up to about 25 km were also obtained from observations of Raman backscattering from nitrogen molecules. Comparisons were carried out for stratospheric heights with satellite borne measurements; good agreement was found between equivalent black body temperatures derived from the lidar observations and those obtained from nadir measurements in three channels of the stratosphere sounder units on NOAA satellites; the lidar based atmospheric temperatures have shown general agreement with but a greater degree of structure than the limb sounding measurements obtained using the SAMS experiment on the NOAA-7 satellite. In summer, stratospheric and mesospheric temperatures showed a smooth height variation similar to that of the CIRA model atmosphere. In contrast, the winter data showed a great variability with height, and marked temperature changes both from night to night and within a given night
Taking the C out of CVMFS
The Cern Virtual Machine File System is most well known as a distribution mechanism for the WLCG VOs@@ experiment software; as a result, almost all the existing expertise is in installing clients mount the central Cern repositories. We report the results of an initial experiment in using the cvmfs server packages to provide Glasgow-based repository aimed at software provisioning for small UK-local VOs. In general, although the documentation is sparse, server configuration is reasonably easy, with some experimentation. We discuss the advantages of local CVMFS repositories for sites, with some examples from our test VOs, vo.optics.ac.uk and neiss.org.uk
Highly loaded multi-stage fan drive turbine: Performance of final three configurations
Results for a three-stage highly loaded fan drive turbine follow-on test program are presented. The effects of combinations of tandem and leaned bladerows on three-stage turbine performance were tested. The three-stage turbine with a tandem stator in stage two exhibited a total-to-total efficiency of approximately 0.887 as compared to 0.886 for the plain blade turbine base case
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