5,734 research outputs found
Vincia for Hadron Colliders
We present the first public implementation of antenna-based QCD initial- and
final-state showers. The shower kernels are antenna functions, which
capture not only the collinear dynamics but also the leading soft (coherent)
singularities of QCD matrix elements. We define the evolution measure to be
inversely proportional to the leading poles, hence gluon emissions are evolved
in a measure inversely proportional to the eikonal, while processes
that only contain a single pole (e.g., ) are evolved in
virtuality. Non-ordered emissions are allowed, suppressed by an additional
power of . Recoils and kinematics are governed by exact on-shell phase-space factorisations. This first implementation is limited to massless
QCD partons and colourless resonances. Tree-level matrix-element corrections
are included for QCD up to (4 jets), and for
Drell-Yan and Higgs production up to ( + 3
jets). The resulting algorithm has been made publicly available in Vincia 2.0
Baryon Number Violation and String Topologies
In supersymmetric scenarios with broken R-parity, baryon number violating
sparticle decays become possible. In order to search for such decays, a good
understanding of expected event properties is essential. We here develop a
complete framework that allows detailed studies. Special attention is given to
the hadronization phase, wherein the baryon number violating vertex is
associated with the appearance of a junction in the colour confinement field.
This allows us to tell where to look for the extra (anti)baryon directly
associated with the baryon number violating decay.Comment: 1+55 pages, 30 figure
Higher-Order Corrections to Timelike Jets
We present a simple formalism for the evolution of timelike jets in which
tree-level matrix element corrections can be systematically incorporated, up to
arbitrary parton multiplicities and over all of phase space, in a way that
exponentiates the matching corrections. The scheme is cast as a shower Markov
chain which generates one single unweighted event sample, that can be passed to
standard hadronization models. Remaining perturbative uncertainties are
estimated by providing several alternative weight sets for the same events, at
a relatively modest additional overhead. As an explicit example, we consider Z
-> q qbar evolution with unpolarized, massless quarks and include several
formally subleading improvements as well as matching to tree-level matrix
elements through alpha_s^4. The resulting algorithm is implemented in the
publicly available VINCIA plugin to the PYTHIA 8 event generator.Comment: 72 pages, 78 figure
THE TOOLS AND MONTE CARLO WORKING GROUP Summary Report from the Les Houches 2009 Workshop on TeV Colliders
This is the summary and introduction to the proceedings contributions for the
Les Houches 2009 "Tools and Monte Carlo" working group.Comment: 144 Pages. Workshop site
http://wwwlapp.in2p3.fr/conferences/LesHouches/Houches2009/ . Conveners were
Butterworth, Maltoni, Moortgat, Richardson, Schumann and Skand
Design and Development of a Twisted String Exoskeleton Robot for the Upper Limb
High-intensity and task-specific upper-limb treatment of active, highly repetitive movements are the effective approaches for patients with motor disorders. However, with the severe shortage of medical service in the United States and the fact that post-stroke survivors can continue to incur significant financial costs, patients often choose not to return to the hospital or clinic for complete recovery. Therefore, robot-assisted therapy can be considered as an alternative rehabilitation approach because the similar or better results as the patients who receive intensive conventional therapy offered by professional physicians.;The primary objective of this study was to design and fabricate an effective mobile assistive robotic system that can provide stroke patients shoulder and elbow assistance. To reduce the size of actuators and to minimize the weight that needs to be carried by users, two sets of dual twisted-string actuators, each with 7 strands (1 neutral and 6 effective) were used to extend/contract the adopted strings to drive the rotational movements of shoulder and elbow joints through a Bowden cable mechanism. Furthermore, movements of non-disabled people were captured as templates of training trajectories to provide effective rehabilitation.;The specific aims of this study included the development of a two-degree-of-freedom prototype for the elbow and shoulder joints, an adaptive robust control algorithm with cross-coupling dynamics that can compensate for both nonlinear factors of the system and asynchronization between individual actuators as well as an approach for extracting the reference trajectories for the assistive robotic from non-disabled people based on Microsoft Kinect sensor and Dynamic time warping algorithm. Finally, the data acquisition and control system of the robot was implemented by Intel Galileo and XILINX FPGA embedded system
Report of the QCD Tools Working Group
We report on the activities of the ``QCD Tools for heavy flavors and new
physics searches'' working group of the Run II Workshop on QCD and Weak Bosons.
The contributions cover the topics of improved parton showering and comparisons
of Monte Carlo programs and resummation calculations, recent developments in
Pythia, the methodology of measuring backgrounds to new physics searches,
variable flavor number schemes for heavy quark electro-production, the
underlying event in hard scattering processes, and the Monte Carlo MCFM for NLO
processes.Comment: LaTeX, 47 pages, 41 figures, 10 tables, uses run2col.sty, to appear
in the Proceedings of the Workshop on "QCD and Weak Boson Physics in Run II",
Fermilab, March - November 199
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