30,439 research outputs found

    Use of ordination and classification procedures to evaluate phytoplankton communities during Superflux II

    Get PDF
    Cluster analysis and an ordination procedure were performed on two data matrices to investigate real and environmental spatial relationships. Multiple regression analysis was used to relate the measured environmental variables to the phytoplankton community changes. Qualitative type phytoplankton data proved to be less structured in both of these spaces, relative to the biomass data. The salinity gradients of the northern transects covaried significantly with the phytoplankton association changes. In the southern transects the light variable was most important in explaining the variance in the ordination axes. These data suggest the close relationships between phytoplankton community changes and the physical hydrology of the area

    Resolving an Individual One-Proton Spin Flip to Determine a Proton Spin State

    Full text link
    Previous measurements with a single trapped proton or antiproton detected spin resonance from the increased scatter of frequency measurements caused by many spin flips. Here a measured correlation confirms that individual spin transitions and states are detected instead. The high fidelity suggests that it may be possible to use quantum jump spectroscopy to measure the p and \pbar magnetic moments much more precisely.Comment: 4 pages, 7 figure

    Measurement of the differential cross-sections of inclusive, prompt and non-prompt J/ψ production in proton–proton collisions at √s = 7 TeV

    Get PDF
    The inclusive J/ψ production cross-section and fraction of J/ψ mesons produced in B-hadron decays are measured in proton–proton collisions at √s = 7 TeV with the ATLAS detector at the LHC, as a function of the transverse momentum and rapidity of the J/ψ, using 2.3 pb^(−1) of integrated luminosity. The cross-section is measured from a minimum pT of 1 GeV to a maximum of 70 GeV and for rapidities within |y|<2.4 giving the widest reach of any measurement of J/ψ production to date. The differential production cross-sections of prompt and non-prompt J/ψ are separately determined and are compared to Colour Singlet NNLO^★, filled, Colour Evaporation Model, and FONLL predictions

    Search for Diphoton Events with Large Missing Transverse Energy in 7 TeV Proton-Proton Collisions with the ATLAS Detector

    Get PDF
    A search for diphoton events with large missing transverse energy is presented. The data were collected with the ATLAS detector in proton-proton collisions at √s = 7  TeV at the CERN Large Hadron Collider and correspond to an integrated luminosity of 3.1  pb^(-1). No excess of such events is observed above the standard model background prediction. In the context of a specific model with one universal extra dimension with compactification radius R and gravity-induced decays, values of 1/R < 729  GeV are excluded at 95% C.L., providing the most sensitive limit on this model to date

    Search for Supersymmetry Using Final States with One Lepton, Jets, and Missing Transverse Momentum with the ATLAS Detector in √s = 7 TeV pp Collisions

    Get PDF
    This Letter presents the first search for supersymmetry in final states containing one isolated electron or muon, jets, and missing transverse momentum from √s = 7 TeV proton-proton collisions at the LHC. The data were recorded by the ATLAS experiment during 2010 and correspond to a total integrated luminosity of 35 pb^(-1). No excess above the standard model background expectation is observed. Limits are set on the parameters of the minimal supergravity framework, extending previous limits. Within this framework, for A_0 = GeV, tanÎČ = 3, and ” > 0 and for equal squark and gluino masses, gluino masses below 700 GeV are excluded at 95% confidence level

    A search for new physics in dijet mass and angular distributions in pp collisions at √s = 7 TeV measured with the ATLAS detector

    Get PDF
    A search for new interactions and resonances produced in LHC proton–proton (pp) collisions at a centre-of-mass energy √s = 7 TeV was performed with the ATLAS detector. Using a dataset with an integrated luminosity of 36 pb^(−1), dijet mass and angular distributions were measured up to dijet masses of ~3.5 TeV and were found to be in good agreement with Standard Model predictions. This analysis sets limits at 95% CL on various models for new physics: an excited quark is excluded for mass between 0.60 and 2.64 TeV, an axigluon hypothesis is excluded for axigluon masses between 0.60 and 2.10 TeV and quantum black holes are excluded in models with six extra space–time dimensions for quantum gravity scales between 0.75 and 3.67 TeV. Production cross section limits as a function of dijet mass are set using a simplified Gaussian signal model to facilitate comparisons with other hypotheses. Analysis of the dijet angular distribution using a novel technique simultaneously employing the dijet mass excludes quark contact interactions with a compositeness scale Λ below 9.5 TeV

    Measurement of the W charge asymmetry in the W→ΌΜ decay mode in pp collisions at √s = 7 TeV with the ATLAS detector

    Get PDF
    This Letter reports a measurement of the muon charge asymmetry from W bosons produced in proton–proton collisions at a centre-of-mass energy of 7 TeV with the ATLAS experiment at the LHC. The asymmetry is measured in the W→ΌΜ decay mode as a function of the muon pseudorapidity using a data sample corresponding to a total integrated luminosity of 31 pb^(−1). The results are compared to predictions based on next-to-leading order calculations with various parton distribution functions. This measurement provides information on the u and d quark momentum fractions in the proton

    Search for high-mass states with one lepton plus missing transverse momentum in proton–proton collisions at √s = 7 TeV with the ATLAS detector

    Get PDF
    The ATLAS detector is used to search for high-mass states, such as heavy charged gauge bosons (Wâ€Č,W_*), decaying to a charged lepton (electron or muon) and a neutrino. Results are presented based on the analysis of pp collisions at a center-of-mass energy of 7 TeV corresponding to an integrated luminosity of 36 pb^(−1). No excess beyond standard model expectations is observed. A Wâ€Č with sequential standard model couplings is excluded at 95% confidence level for masses below 1.49 TeV, and a Wlow asterisk (charged chiral boson) for masses below 1.35 TeV
    • 

    corecore