33,558 research outputs found
BTF measurements with beam-beam interactions
We present considerations about the transverse beam transfer function (BTF)
of beams under the influence of two effects: The strong-strong beam-beam effect
and the influence of a Gaussian electron lens. The BTF are investigated using
two methods: BTF excitation is simulated in a particle-in-cell (PIC) code. The
BTF model is verified using a known analytic expectation. Analytic expectations
for BTF of beams under a stationary electron lens are derived by extending BTF
from the formalism of Berg and Ruggiero. Finally we compare the analytic BTF
results for a stationary Gaussian lens to both the PIC simulation for split
tune conditions and to PIC simulations for a beam influenced by an electron
lens. We conclude that the formalism represents the electron lens well and can
be applied to a limited extend to the beam-beam effect under split tune
conditions. The analytic formalism allows us to recover the strength of an
electron lens by means of fitting and can give clues regarding the strength of
the beam-beam effect under split tune conditions.Comment: 5 pages, contribution to the ICFA Mini-Workshop on Beam-Beam Effects
in Hadron Colliders, CERN, Geneva, Switzerland, 18-22 Mar 201
A singlet-triplet extension for the Higgs search at LEP and LHC
We describe a simple extension of the standard model, containing a scalar
singlet and a triplet fermion. The model can explain the possible enhancement
in the decay at the LHC together with the excess
found in the Higgs boson search at LEP2. The structure of the model is
motivated by a recent argument, that was used to explain the number of fermion
generations. For the sake of completenes we also considered the contributions
from higher multiplets.Comment: 12 pages, 2 figure
Theory and applications of four-wave mixing in photorefractive media
The development of a theory of four-wave mixing in photo-refractive crystals is described. This theory is solved in the undepleted pumps approximation with linear absorption and without using the undepleted pumps approximation for negligible absorption. Both the transmission and reflection gratings are treated individually. The results are used to analyze several photorefractive phase conjugate mirrors, yielding reflectivities and thresholds. The use of photorefractive crystals as optical distortion correction elements and experimental demonstrations of several of the passive phase conjugate mirrors are described
Scanning Tunneling Spectroscopy of Bi2Sr2CuO6+d: New Evidence for the Common Origin of the Pseudogap and Superconductivity
Using scanning tunneling spectroscopy, we investigated the temperature dependence of the quasiparticle density of states of overdoped Bi2Sr2CuO6+ÎŽ between 275 mK and 82 K. Below Tc = 10 K, the spectra show a gap with well-defined coherence peaks at ±Îpâ12 meV, which disappear at Tc. Above Tc, the spectra display a clear pseudogap of the same magnitude, gradually filling up and vanishing at T*â68 K. The comparison with Bi2Sr2CaCu2O8+ÎŽ demonstrates that the pseudogap and the superconducting gap scale with each other, providing strong evidence that they have a common origin
Exact solution of a nonlinear model of four-wave mixing and phase conjugation
An exact solution of a nonlinear model of holographic four-wave mixing is derived. An expression for the reflectivity of a phase-conjugate mirror with depleted pumps is presented. We find that such a phase-conjugate mirror may exhibit bistability
Amplified reflection, transmission, and self-oscillation in real-time holography
A theory of phase conjugation in asymmetric materials that allow a phase shift between the grating and the light-interference pattern is developed. We find that when this phase is nonzero, maximum phase-conjugate reflectivity occurs for unequal pump intensities. The conditions for self-oscillation are studied
Passive (self-pumped) phase conjugate mirror: Theoretical and experimental investigation
We report the results of a theoretical and experimental investigation of a passive (self-pumped) phase conjugate mirror. This device is based on real time holography in materials which allow a spatial phase shift between the refractive index grating and the light interference pattern. An imaging experiment is reported showing the phase conjugating nature of the device. The holographic medium used was a single crystal of barium titanate
Nonlinear vectorial two-beam coupling and forward four-wave mixing in photorefractive materials
We present an exact solution of a nonlinear vector analysis of two-beam coupling and forward four-wave mixing in photorefractive media
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