307 research outputs found
CP Phases in Supersymmetric Tri-lepton Signals at the Tevatron
We have analyzed the supersymmetric tri-lepton signals for sparticle searches
at the Tevatron in the minimal supersymmetric standard model with general CP
phases without generational mixing. The CP phases may affect very strongly the
chargino and neutralino mass spectrums and
as well as and . Even under the stringent
constraints from the electron electric dipole moment the CP phases can lead to
a minimum of the tri-lepton event rate for their non-trivial values.Comment: 10 pages, 3 eps figures, largely revised by including the electron
EDM constraint
Photo-induced reduction of graphene oxide coating on optical waveguide and consequent optical intermodulation
Increased absorption of transverse-magnetic (TM) - polarised light by a graphene-oxide (GO) coated polymer waveguide has been observed in the presence of transverse-electric (TE) - polarised light. The GO-coated waveguide exhibits very strong photo-absorption of TE-polarised light - and acts as a TM-pass waveguide polariser. The absorbed TE-polarised light causes a significant temperature increase in the GO film and induces thermal reduction of the GO, resulting in an increase in optical-frequency conductivity and consequently increased optical propagation loss. This behaviour in a GO-coated waveguide gives the action of an inverted optical switch/modulator. By varying the incident TE-polarised light power, a maximum modulation efficiency of 72% was measured, with application of an incident optical power level of 57 mW. The GO-coated waveguide was able to respond clearly to modulated TE-polarised light with a pulse duration of as little as 100 μs. In addition, no wavelength dependence was observed in the response of either the modulation (TE-polarised light) or the signal (TM-polarised light)
Fracture behavior and damage development in self-reinforced PET composites assessed by located acoustic emission and thermography: Effects of flame retardant and recycled PET
Surface structure and solidification morphology of aluminum nanoclusters
Classical molecular dynamics simulation with embedded atom method potential
had been performed to investigate the surface structure and solidification
morphology of aluminum nanoclusters Aln (n = 256, 604, 1220 and 2048). It is
found that Al cluster surfaces are comprised of (111) and (001) crystal planes.
(110) crystal plane is not found on Al cluster surfaces in our simulation. On
the surfaces of smaller Al clusters (n = 256 and 604), (111) crystal planes are
dominant. On larger Al clusters (n = 1220 and 2048), (111) planes are still
dominant but (001) planes can not be neglected. Atomic density on cluster
(111)/(001) surface is smaller/larger than the corresponding value on bulk
surface. Computational analysis on total surface area and surface energies
indicates that the total surface energy of an ideal Al nanocluster has the
minimum value when (001) planes occupy 25% of the total surface area. We
predict that a melted Al cluster will be a truncated octahedron after
equilibrium solidification.Comment: 22 pages, 6 figures, 34 reference
Intrasubband and Intersubband Electron Relaxation in Semiconductor Quantum Wire Structures
We calculate the intersubband and intrasubband many-body inelastic Coulomb
scattering rates due to electron-electron interaction in two-subband
semiconductor quantum wire structures. We analyze our relaxation rates in terms
of contributions from inter- and intrasubband charge-density excitations
separately. We show that the intersubband (intrasubband) charge-density
excitations are primarily responsible for intersubband (intrasubband) inelastic
scattering. We identify the contributions to the inelastic scattering rate
coming from the emission of the single-particle and the collective excitations
individually. We obtain the lifetime of hot electrons injected in each subband
as a function of the total charge density in the wire.Comment: Submitted to PRB. 20 pages, Latex file, and 7 postscript files with
Figure
Examining the Higgs boson potential at lepton and hadron colliders: a comparative analysis
We investigate inclusive Standard Model Higgs boson pair production at lepton
and hadron colliders for Higgs boson masses in the range 120 GeV < m_H < 200
GeV. For m_H < 140 GeV we find that hadron colliders have a very limited
capability to determine the Higgs boson self-coupling, \lambda, due to an
overwhelming background. We also find that, in this mass range, supersymmetric
Higgs boson pairs may be observable at the LHC, but a measurement of the self
coupling will not be possible. For m_H > 140 GeV we examine ZHH and HH nu
bar-nu production at a future e+e- linear collider with center of mass energy
in the range of sqrt{s}=0.5 - 1 TeV, and find that this is likely to be equally
difficult. Combining our results with those of previous literature, which has
demonstrated the capability of hadron and lepton machines to determine \lambda
in either the high or the low mass regions, we establish a very strong
complementarity of these machines.Comment: Revtex, 25 pages, 2 tables, 10 figure
Determining the Higgs Boson Self Coupling at Hadron Colliders
Inclusive Standard Model Higgs boson pair production at hadron colliders has
the capability to determine the Higgs boson self-coupling, lambda. We present a
detailed analysis of the gg\to HH\to (W^+W^-)(W^+W^-)\to
(jjl^\pm\nu)(jj{l'}^\pm\nu) and gg\to HH\to (W^+W^-)(W^+W^-)\to
(jjl^\pm\nu)({l'}^\pm\nu {l''}^\mp\nu) (l, {l'}, {l''}=e, \mu) signal channels,
and the relevant background processes, for the CERN Large Hadron Collider, and
a future Very Large Hadron Collider operating at a center-of-mass energy of 200
TeV. We also derive quantitative sensitivity limits for lambda. We find that it
should be possible at the LHC with design luminosity to establish that the
Standard Model Higgs boson has a non-zero self-coupling and that lambda /
lambda_{SM} can be restricted to a range of 0-3.8 at 95% confidence level (CL)
if its mass is between 150 and 200 GeV. At a 200 TeV collider with an
integrated luminosity of 300 fb^{-1}, lambda can be determined with an accuracy
of 8 - 25% at 95% CL in the same mass range.Comment: 28 pages, Revtex3, 9 figures, 3 table
Triggering Threshold Spacecraft Charging with Changes in Electron Emission from Materials
Modest changes in spacecraft charging conditions can lead to abrupt changes in the spacecraft equilibrium, from small positive potentials to large negative potentials relative to the space plasma; this phenomenon is referred to as threshold charging. It is well known that temporal changes of the space plasma environment (electron plasma temperature or density) can cause threshold charging. Threshold charging can also result from by temporal changes in the juxtaposition of the spacecraft to the environment, including spacecraft orbit, orientation, and geometry. This study focuses on the effects of possible changes in electron emission properties of representative spacecraft materials. It is found that for electron-induced emission, the possible threshold scenarios are very rich, since this type of electron emission can cause either positive or negative charging. Alternately, modification of photon- or ion-induced electron emission is found to induce threshold charging only in certain favorable cases. Changes of emission properties discussed include modifications due to: contamination, degradation and roughening of surfaces and layered materials; biasing and charge accumulation; bandstructure occupation and density of states caused by heat, optical or particle radiation; optical reflectivity and absorptivity; and inaccuracies and errors in measurements and parameterization of materials properties. An established method is used here to quantitatively gauge the relative extent to which these various changes in electron emission alter a spacecraft’s charging behavior and possibly lead to threshold charging. The absolute charging behavior of a hypothetical flat, two-dimensional satellite panel of a single material (either polycrystalline conductor Au or the polymeric polyimide Kapton™ H) is modeled as it undergoes modification and concomitant changes in spacecraft charging in three representative geosynchronous orbit environments, from full sunlight to full shade (eclipse) are considered
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