13,226 research outputs found
Fiberglass container shells form contamination-free storage units
Interchangeable molded fiberglass shells are locked together to form storage units of various depths. These units can hold components weighing 1500 pounds, are easily transportable, and protect contents from contamination
Matching the Nagy-Soper parton shower at next-to-leading order
We present an MC@NLO-like matching of next-to-leading order QCD calculations
with the Nagy-Soper parton shower. An implementation of the algorithm within
the HELAC-DIPOLES Monte Carlo generator is used to address the uncertainties
and ambiguities of the matching scheme. First results obtained using the
Nagy-Soper parton shower implementation in DEDUCTOR in conjunction with the
HELAC-NLO framework are given for the pp -> top anti-top j + X process at the
LHC with sqrt(s)=8 TeV. Effects of resummation are discussed for various
observables.Comment: 53 pages, 18 figures, 3 tables. References and a few typos corrected,
acknowledgments added, dependence on the variation of the starting shower
time corrected, version to appear in JHE
Off-shell Top Quarks with One Jet at the LHC: A comprehensive analysis at NLO QCD
We present a comprehensive study of the production of top quark pairs in
association with one hard jet in the di-lepton decay channel at the LHC. Our
predictions, accurate at NLO in QCD, focus on the LHC Run II with a
center-of-mass energy of 13 TeV. All resonant and non-resonant contributions at
the perturbative order are taken into account,
including irreducible backgrounds to production, interferences and
off-shell effects of the top quark and the gauge boson. We extensively
investigate the dependence of our results upon variation of renormalisation and
factorisation scales and parton distribution functions in the quest for an
accurate estimate of the theoretical uncertainties. Additionally, we explore a
few possibilities for a dynamical scale choice with the goal of stabilizing the
perturbative convergence of the differential cross sections far away from the
threshold. Results presented here are particularly relevant for
searches of new physics as well as for precise measurements of the top-quark
fiducial cross sections and top-quark properties at the LHC.Comment: 51 pages, 36 figures, 6 tables, version to appear in JHE
Self-consistent stationary MHD shear flows in the solar atmosphere as electric field generators
Magnetic fields and flows in coronal structures, for example, in gradual
phases in flares, can be described by 2D and 3D magnetohydrostatic (MHS) and
steady magnetohydrodynamic (MHD) equilibria. Within a physically simplified,
but exact mathematical model, we study the electric currents and corresponding
electric fields generated by shear flows. Starting from exact and analytically
calculated magnetic potential fields, we solveid the nonlinear MHD equations
self-consistently. By applying a magnetic shear flow and assuming a nonideal
MHD environment, we calculated an electric field via Faraday's law. The formal
solution for the electromagnetic field allowed us to compute an expression of
an effective resistivity similar to the collisionless Speiser resistivity. We
find that the electric field can be highly spatially structured, or in other
words, filamented. The electric field component parallel to the magnetic field
is the dominant component and is high where the resistivity has a maximum. The
electric field is a potential field, therefore, the highest energy gain of the
particles can be directly derived from the corresponding voltage. In our
example of a coronal post-flare scenario we obtain electron energies of tens of
keV, which are on the same order of magnitude as found observationally. This
energy serves as a source for heating and acceleration of particles.Comment: 11 pages, 9 figures, accepted to Astronomy and Astrophysic
Mapping vesicle shapes into the phase diagram: A comparison of experiment and theory
Phase-contrast microscopy is used to monitor the shapes of micron-scale
fluid-phase phospholipid-bilayer vesicles in aqueous solution. At fixed
temperature, each vesicle undergoes thermal shape fluctuations. We are able
experimentally to characterize the thermal shape ensemble by digitizing the
vesicle outline in real time and storing the time-sequence of images. Analysis
of this ensemble using the area-difference-elasticity (ADE) model of vesicle
shapes allows us to associate (map) each time-sequence to a point in the
zero-temperature (shape) phase diagram. Changing the laboratory temperature
modifies the control parameters (area, volume, etc.) of each vesicle, so it
sweeps out a trajectory across the theoretical phase diagram. It is a
nontrivial test of the ADE model to check that these trajectories remain
confined to regions of the phase diagram where the corresponding shapes are
locally stable. In particular, we study the thermal trajectories of three
prolate vesicles which, upon heating, experienced a mechanical instability
leading to budding. We verify that the position of the observed instability and
the geometry of the budded shape are in reasonable accord with the theoretical
predictions. The inability of previous experiments to detect the ``hidden''
control parameters (relaxed area difference and spontaneous curvature) make
this the first direct quantitative confrontation between vesicle-shape theory
and experiment.Comment: submitted to PRE, LaTeX, 26 pages, 11 ps-fi
Noncommutative spin-1/2 representations
In this letter we apply the methods of our previous paper hep-th/0108045 to
noncommutative fermions. We show that the fermions form a spin-1/2
representation of the Lorentz algebra. The covariant splitting of the conformal
transformations into a field-dependent part and a \theta-part implies the
Seiberg-Witten differential equations for the fermions.Comment: 7 pages, LaTe
Particle production in p-p collisions at sqrt(s) = 17 GeV within the statistical model
A thermal-model analysis of particle production of p-p collisions at sqrt(s)
= 17 GeV using the latest available data is presented. The sensitivity of model
parameters on data selections and model assumptions is studied. The system-size
dependence of thermal parameters and recent differences in the statistical
model analysis of p-p collisions at the super proton synchrotron (SPS) are
discussed. It is shown that the temperature and strangeness undersaturation
factor depend strongly on kaon yields which at present are still not well known
experimentally. It is conclude, that within the presently available data at the
SPS it is rather unlikely that the temperature in p-p collisions exceeds
significantly that expected in central collisions of heavy ions at the same
energy.Comment: 6 pages, 3 figures, submitted to Phys. Rev.
- …