50 research outputs found

    Measurement of event-shape observables in Z→ℓ+ℓ− events in pp collisions at √ s=7 TeV with the ATLAS detector at the LHC

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    Event-shape observables measured using charged particles in inclusive ZZ-boson events are presented, using the electron and muon decay modes of the ZZ bosons. The measurements are based on an integrated luminosity of 1.1fb11.1 {\rm fb}^{-1} of proton--proton collisions recorded by the ATLAS detector at the LHC at a centre-of-mass energy s=7\sqrt{s}=7 TeV. Charged-particle distributions, excluding the lepton--antilepton pair from the ZZ-boson decay, are measured in different ranges of transverse momentum of the ZZ boson. Distributions include multiplicity, scalar sum of transverse momenta, beam thrust, transverse thrust, spherocity, and F\mathcal{F}-parameter, which are in particular sensitive to properties of the underlying event at small values of the ZZ-boson transverse momentum. The Sherpa event generator shows larger deviations from the measured observables than Pythia8 and Herwig7. Typically, all three Monte Carlo generators provide predictions that are in better agreement with the data at high ZZ-boson transverse momenta than at low ZZ-boson transverse momenta and for the observables that are less sensitive to the number of charged particles in the event.Comment: 36 pages plus author list + cover page (54 pages total), 14 figures, 4 tables, submitted to EPJC, All figures including auxiliary figures are available at http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/STDM-2014-0

    The relevance of age for work in a warm humid climate

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    The present study was designed to study the relevance of age related differences in heat stress response in relation to physical fitness related differences. For this purpose, a test group was selected (age 20-73 years) in which no correlation was present between the subjects fitness level and their age, but in which large variations of both parameters within groups were present. The question whether the effect of age, as observed in other studies, is relevant com-pared to the effect of physical fitness was answered in a negative sense. Though a small age effect may exist, this is only measurable when groups are matched precisely with respect to their physical characteristics. No relevant age effect on heat stress response in body core temperature and heart rate (expressed as percentage of maximal heart rate) is present when comparing age groups with equal average V_O2max. The reduction in individual absolute maximal heart rate with age resulted in lower heart rates for equal work loads in older subjects
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