501 research outputs found
High multiplicity W+jets predictions at NLO
In these proceedings we present results from a recent calculation for the
production of a W boson in conjunction with five jets at next-to-leading order
in perturbative QCD. We also use results at lower multiplicities to extrapolate
the cross section to the same process with six jets.Comment: 5 pages, Proceedings for the DIS2013 conferenc
High multiplicity processes at NLO with BlackHat and Sherpa
In this contribution we review recent progress with fixed-order QCD
predictions for the production of a vector boson in association with jets at
hadron colliders, using the programs BlackHat and SHERPA. We review general
features of next-to-leading-order (NLO) predictions for the production of a
massive vector boson in association with four jets. We also discuss how precise
descriptions of vector-boson production can be applied to the determination of
backgrounds to new physics signals. Here we focus on data-driven backgrounds to
a missing-energy-plus-jets search performed by CMS. Finally, we review recent
progress in developing theoretical tools for high-multiplicity loop-computation
within the BlackHat-library. In particular, we discuss methods for handling the
color degrees of freedom in multi-jet predictions at NLO.Comment: 12 pages, contribution to the proceedings of Loops and Legs 201
Orbital entanglement and violation of Bell inequalities in mesoscopic conductors
We propose a spin-independent scheme to generate and detect two-particle
entanglement in a mesoscopic normal-superconductor system. A superconductor,
weakly coupled to the normal conductor, generates an orbitally entangled state
by injecting pairs of electrons into different leads of the normal conductor.
The entanglement is detected via violation of a Bell inequality, formulated in
terms of zero-frequency current cross-correlators. It is shown that the Bell
inequality can be violated for arbitrary strong dephasing in the normal
conductor.Comment: 4 pages, 2 figure
Conditional preparation of a quantum state in the continuous variable regime: generation of a sub-Poissonian state from twin beams
We report the first experimental demonstration of conditional preparation of
a non classical state of light in the continuous variable regime. Starting from
a non degenerate OPO which generates above threshold quantum intensity
correlated signal and idler "twin beams", we keep the recorded values of the
signal intensity only when the idler falls inside a band of values narrower
than its standard deviation. By this very simple technique, we generate a
sub-Poissonian state 4.4dB below shot noise from twin beams exhibiting 7.5dB of
noise reduction in the intensity difference.Comment: 4 pages, Accepted in Phys. Rev. Let
Application of the Principle of Maximum Conformality to Top-Pair Production
A major contribution to the uncertainty of finite-order perturbative QCD
predictions is the perceived ambiguity in setting the renormalization scale
. For example, by using the conventional way of setting , one obtains the total production cross-section
with the uncertainty \Delta \sigma_{t \bar{t}}/\sigma_{t
\bar{t}}\sim ({}^{+3%}_{-4%}) at the Tevatron and LHC even for the present
NNLO level. The Principle of Maximum Conformality (PMC) eliminates the
renormalization scale ambiguity in precision tests of Abelian QED and
non-Abelian QCD theories. In this paper we apply PMC scale-setting to predict
the cross-section at the Tevatron and LHC
colliders. It is found that remains almost unchanged by
varying within the region of . The convergence
of the expansion series is greatly improved. For the -channel,
which is dominant at the Tevatron, its NLO PMC scale is much smaller than the
top-quark mass in the small -region, and thus its NLO cross-section is
increased by about a factor of two. In the case of the -channel, which is
dominant at the LHC, its NLO PMC scale slightly increases with the subprocess
collision energy , but it is still smaller than for
TeV, and the resulting NLO cross-section is increased by
. As a result, a larger is obtained in comparison
to the conventional scale-setting method, which agrees well with the present
Tevatron and LHC data. More explicitly, by setting GeV, we
predict pb,
pb and pb. [full abstract can be found in the
paper.]Comment: 15 pages, 11 figures, 5 tables. Fig.(9) is correcte
Defective neuroepithelial cell cohesion affects tangential branchiomotor neuron migration in the zebrafish neural tube
Facial branchiomotor neurons (FBMNs) in zebrafish and mouse embryonic hindbrain undergo a characteristic tangential migration from rhombomere (r) 4, where they are born, to r6/7. Cohesion among neuroepithelial cells (NCs) has been suggested to function in FBMN migration by inhibiting FBMNs positioned in the basal neuroepithelium such that they move apically between NCs towards the midline of the neuroepithelium instead of tangentially along the basal side of the neuroepithelium towards r6/7. However, direct experimental evaluation of this hypothesis is still lacking. Here, we have used a combination of biophysical cell adhesion measurements and high-resolution time-lapse microscopy to determine the role of NC cohesion in FBMN migration. We show that reducing NC cohesion by interfering with Cadherin 2 (Cdh2) activity results in FBMNs positioned at the basal side of the neuroepithelium moving apically towards the neural tube midline instead of tangentially towards r6/7. In embryos with strongly reduced NC cohesion, ectopic apical FBMN movement frequently results in fusion of the bilateral FBMN clusters over the apical midline of the neural tube. By contrast, reducing cohesion among FBMNs by interfering with Contactin 2 (Cntn2) expression in these cells has little effect on apical FBMN movement, but reduces the fusion of the bilateral FBMN clusters in embryos with strongly diminished NC cohesion. These data provide direct experimental evidence that NC cohesion functions in tangential FBMN migration by restricting their apical movement
Cyclical Quantum Memory for Photonic Qubits
We have performed a proof-of-principle experiment in which qubits encoded in
the polarization states of single-photons from a parametric down-conversion
source were coherently stored and read-out from a quantum memory device. The
memory device utilized a simple free-space storage loop, providing a cyclical
read-out that could be synchronized with the cycle time of a quantum computer.
The coherence of the photonic qubits was maintained during switching operations
by using a high-speed polarizing Sagnac interferometer switch.Comment: 4 pages, 5 figure
Quantum Noise in Multipixel Image Processing
We consider the general problem of the quantum noise in a multipixel
measurement of an optical image. We first give a precise criterium in order to
characterize intrinsic single mode and multimode light. Then, using a
transverse mode decomposition, for each type of possible linear combination of
the pixels' outputs we give the exact expression of the detection mode, i.e.
the mode carrying the noise. We give also the only way to reduce the noise in
one or several simultaneous measurements.Comment: 8 pages and 1 figur
Symmetric qubits from cavity states
Two-mode cavities can be prepared in quantum states which represent symmetric
multi-qubit states. However, the qubits are impossible to address individually
and as such cannot be independently measured or otherwise manipulated. We
propose two related schemes to coherently transfer the qubits which the cavity
state represents onto individual atoms, so that the qubits can then be
processed individually. In particular, our scheme can be combined with the
quantum cloning scheme of Simon and coworkers [C. Simon et al, PRL 84, 2993
(2000)] to allow the optimal clones which their scheme produces to be spatially
separated and individually utilized.Comment: 8 pages, 4 figures, minor typographical errors correcte
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