4,893 research outputs found
The Matrix Element Method and QCD Radiation
The matrix element method (MEM) has been extensively used for the analysis of
top-quark and W-boson physics at the Tevatron, but in general without dedicated
treatment of initial state QCD radiation. At the LHC, the increased center of
mass energy leads to a significant increase in the amount of QCD radiation,
which makes it mandatory to carefully account for its effects. We here present
several methods for inclusion of QCD radiation effects in the MEM, and apply
them to mass determination in the presence of multiple invisible particles in
the final state. We demonstrate significantly improved results compared to the
standard treatment.Comment: 15 pp; v2: references and some clarifications added; v3: discussion
of NLO effects, version published in PR
Gravitational Model of High Energy Particles in a Collimated Jet
Observations suggest that relativistic particles play a fundamental role in
the dynamics of jets emerging from active galactic nuclei as well as in their
interaction with the intracluster medium. However, no general consensus exists
concerning the acceleration mechanism of those high energy particles. A
gravitational acceleration mechanism is here proposed, in which particles
leaving precise regions within the ergosphere of a rotating supermassive black
hole produce a highly collimated flow. These particles follow unbound geodesics
which are asymptotically parallel to the spin axis of the black hole and are
characterized by the energy , the Carter constant and zero
angular momentum of the component . If environmental effects are
neglected, the present model predicts at distances of about 140 kpc from the
ergosphere the presence of electrons with energies around 9.4 GeV. The present
mechanism can also accelerate protons up to the highest energies observed in
cosmic rays by the present experiments.Comment: 27 pages and 5 figures. Accepted for publication in Astrophysical
Journal. arXiv admin note: text overlap with arXiv:1011.654
A frictionless microswimmer
We investigate the self-locomotion of an elongated microswimmer by virtue of
the unidirectional tangential surface treadmilling. We show that the propulsion
could be almost frictionless, as the microswimmer is propelled forward with the
speed of the backward surface motion, i.e. it moves throughout an almost
quiescent fluid. We investigate this swimming technique using the special
spheroidal coordinates and also find an explicit closed-form optimal solution
for a two-dimensional treadmiler via complex-variable techniques.Comment: 6 pages, 4 figure
Statistical stability of equilibrium states for interval maps
We consider families of multimodal interval maps with polynomial growth of
the derivative along the critical orbits. For these maps Bruin and Todd have
shown the existence and uniqueness of equilibrium states for the potential
, for close to 1. We show that these
equilibrium states vary continuously in the weak topology within such
families. Moreover, in the case , when the equilibrium states are
absolutely continuous with respect to Lebesgue, we show that the densities vary
continuously within these families.Comment: More details given and the appendices now incorporated into the rest
of the pape
Custo de produção - o caso do carå-da-costa.
bitstream/item/72339/1/CPAMN-COM.-TEC.-6-92.pd
Sistemas agroflorestais na agricultura familiar como alternativa para diversificação da produção e redução de queimadas no nordeste Paraense.
Implementing Safety Leading Indicators in Construction: Insights on Relative Importance of Indicators
Lagging indicators have been widely used in the construction industry to measure and improve safety performance for decades; however, they are criticised for providing insufficient information to generate continuous improvement because they only indicate safety outputs. Against this backdrop, industry and academia have investigated safety leading indicators in addition to traditionally used lagging indicators. Leading indicators are proactive in nature because they measure safety initiatives that provide an early indication of impending adverse events, which in turn allows management to initiate corrective steps. Although leading indicators are an emergent area of research, there is limited knowledge to guide their implementation in terms of their selection and use. Having insight regarding their relative importance could thus be useful. To address the knowledge gap, this study conducted a systematic literature review on safety leading indicators in construction which resulted in the identification of 16 safety leading indicators. A subsequent two-round Delphi technique involving industry experts was used to determine the relative importance. The results show that organisational commitment, client engagement, main contractor engagement, supply chain engagement, and designer engagement are perceived by the industry experts as being among the topmost important indicators for safety management performance. The findings would enhance the construction industryâs understanding of safety leading indicators and help organisations prioritise efforts to enhance their safety performance
The governance of formal universityâindustry interactions: understanding the rationales for alternative models
This article develops a conceptual framework to explain the economic rationale underpinning the choice of different modes of governance of formal universityâindustry interactions: personal contractual interactions, where the contract regulating the collaboration involves a firm and an individual academic researcher, and institutional interactions, where the relationship between the firm and the academic is mediated by the university. Although institutional interactions, for numerous reasons, have become more important, both governance modes are currently being implemented. We would argue that they have some important specificities that need to be understood if universityâindustry knowledge transfer is to be managed effectively and efficiently
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