34,742 research outputs found
Investigation of beauty production and parton shower effects at LHC
We present hadron-level predictions from the Monte Carlo generator Cascade
and parton level calculations of open b quark, b-flavored hadron and inclusive
b-jet production in the framework of the kt-factorization QCD approach for the
LHC energies. The unintegrated gluon densities in a proton are determined using
the CCFM evolution equation and the Kimber-Martin-Ryskin (KMR) prescription.
Our predictions are compared with the first data taken by the CMS and LHCb
collaborations at 7 TeV. We study the theoretical uncertainties of our
calculations and investigate the effects coming from parton showers in initial
and final states. The special role of initial gluon transverse momenta in
description of the data is pointed out.Comment: 19 pages, 11 figures. arXiv admin note: substantial text overlap with
arXiv:1105.507
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Fractal scattering dynamics of the three-dimensional HOCl molecule
We compare the 2D and 3D classical fractal scattering dynamics of Cl and HO for energies just above dissociation of the HOCl molecule, using a realistic potential energy surface for the HOCl molecule and techniques developed to analyze 3D chaotic scattering processes. For parameter regimes where the HO dimer initially has small vibrational energy, only small intervals of initial conditions show fractal scattering behavior and the scattering process is well described by a 2D model. For parameter regimes where the HO dimer initially has large vibrational energy, the scattering process is fully 3D and is dominated by fractal behavior.Robert A. Welch Foundation F-1051CONACyT 79988DGAPA IN110110Physic
Mixed-State Entanglement and Quantum Teleportation through Noisy Channels
The quantum teleportation with noisy EPR state is discussed. Using an optimal
decomposition technique, we compute the concurrence, entanglement of formation
and Groverian measure for various noisy EPR resources. It is shown analytically
that all entanglement measures reduce to zero when , where
is an average fidelity between Alice and Bob. This fact indicates
that the entanglement is a genuine physical resource for the teleportation
process. This fact gives valuable clues on the optimal decomposition for
higher-qubit mixed states. As an example, the optimal decompositions for the
three-qubit mixed states are discussed by adopting a teleportation with W-stateComment: 18 pages, 4 figure
NRG for the bosonic single-impurity Anderson model: Dynamics
The bosonic single-impurity Anderson model (B-SIAM) is studied to understand
the local dynamics of an atomic quantum dot (AQD) coupled to a Bose-Einstein
condensation (BEC) state, which can be implemented to probe the entanglement
and the decoherence of a macroscopic condensate. Our recent approach of the
numerical renormalization group (NRG) calculation for the B-SIAM revealed a
zero-temperature phase diagram, where a Mott phase with local depletion of
normal particles is separated from a BEC phase with enhanced density of the
condensate. As an extension of the previous work, we present the calculations
of the local dynamical quantities of the B-SIAM which reinforce our
understanding of the physics in the Mott and the BEC phases.Comment: 12 pages, 13 figure
Tripartite Entanglement in Noninertial Frame
The tripartite entanglement is examined when one of the three parties moves
with a uniform acceleration with respect to other parties. As Unruh effect
indicates, the tripartite entanglement exhibits a decreasing behavior with
increasing the acceleration. Unlike the bipartite entanglement, however, the
tripartite entanglement does not completely vanish in the infinite acceleration
limit. If the three parties, for example, share the Greenberger-Horne-Zeilinger
or W-state initially, the corresponding -tangle, one of the measures for
tripartite entanglement, is shown to be or 0.176 in this
limit, respectively. This fact indicates that the tripartite quantum
information processing may be possible even if one of the parties approaches to
the Rindler horizon. The physical implications of this striking result are
discussed in the context of black hole physics.Comment: 19 pages, 5 figure
Ionic and Electronic Conductivity of Nanostructured, Samaria-Doped Ceria
The ionic and electronic conductivities of samaria doped ceria electrolytes, Ce_(0.85)Sm_(0.15)O_(1.925−δ), with nanometric grain size have been evaluated. Nanostructured bulk specimens were obtained using a combination of high specific-surface-area starting materials and suitable sintering profiles under conventional, pressureless conditions. Bulk specimens with relatively high density (≥92% of theoretical density) and low medium grain size (as small as 33 nm) were achieved. Electrical A.C. impedance spectra were recorded over wide temperature (150 to 650°C) and oxygen partial pressure ranges (0.21 to 10^(−31) atm). Under all measurement conditions the total conductivity decreased monotonically with decreasing grain size. In both the electrolytic and mixed conducting regimes this behavior is attributed to the high number density of high resistance grain boundaries. The results suggest a possible variation in effective grain boundary width with grain size, as well as a possible variation in specific grain boundary resistance with decreasing oxygen partial pressure. No evidence appears for either enhanced reducibility or enhanced electronic conductivity upon nanostructuring
Spinor Dynamics in an Antiferromagnetic Spin-1 Condensate
We observe coherent spin oscillations in an antiferromagnetic spin-1
Bose-Einstein condensate of sodium. The variation of the spin oscillations with
magnetic field shows a clear signature of nonlinearity, in agreement with
theory, which also predicts anharmonic oscillations near a critical magnetic
field. Measurements of the magnetic phase diagram agree with predictions made
in the approximation of a single spatial mode. The oscillation period yields
the best measurement to date of the sodium spin-dependent interaction
coefficient, determining that the difference between the sodium spin-dependent
s-wave scattering lengths is Bohr radii.Comment: 5 pages, 2 figures. Changes: added reference, minor correction
Reduced Fine-Tuning in Supersymmetry with R-parity violation
Both electroweak precision measurements and simple supersymmetric extensions
of the standard model prefer a mass of the Higgs boson less than the
experimental lower limit of 114 GeV. We show that supersymmetric models with R
parity violation and baryon number violation have a significant range of
parameter space in which the Higgs dominantly decays to six jets. These decays
are much more weakly constrained by current LEP analyses and would allow for a
Higgs mass near that of the . In general, lighter scalar quark and other
superpartner masses are allowed and the fine-tuning typically required to
generate the measured scale of electroweak symmetry breaking is ameliorated.
The Higgs would potentially be discovered at hadron colliders via the
appearance of new displaced vertices. The lightest neutralino could be
discovered by a scan of vertex-less events LEP I data.Comment: 5 pages, 2 figures. Significant detail added to the arguments
regarding LEP limits - made more quantitative. Better figures used, plotting
more physical quantities. Typos corrected and references updated. Conclusions
unchange
Dynamic Creation and Annihilation of Metastable Vortex Phase as a Source of Excess Noise
The large increase in voltage noise, commonly observed in the vicinity of the
peak-effect in superconductors, is ascribed to a novel noise mechanism. A
strongly pinned metastable disordered vortex phase, which is randomly generated
at the edges and annealed into ordered phase in the bulk, causes large
fluctuations in the integrated critical current of the sample. The excess noise
due to this dynamic admixture of two distinct phases is found to display
pronounced reentrant behavior. In the Corbino geometry the injection of the
metastable phase is prevented and, accordingly, the excess noise disappearsComment: 5 pages 3 figures. Accepted for publication in Europhysics letter
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