Quantifying the power of multiple event interpretations

A number of methods have been proposed recently which exploit multiple highly-correlated interpretations of events, or of jets within an event. For example, Qjets reclusters a jet multiple times and telescoping jets uses multiple cone sizes. Previous work has employed these methods in pseudo-experimental analyses and found that, with a simplified statistical treatment, they give sizable improvements over traditional methods. In this paper, the improvement gain from multiple event interpretations is explored with methods much closer to those used in real experiments. To this end, we derive a generalized extended maximum likelihood procedure. We study the significance improvement in Higgs to bb with both this method and the simplified method from previous analysis. With either method, we find that using multiple jet radii can provide substantial benefit over a single radius. Another concern we address is that multiple event interpretations might be exploiting similar information to that already present in the standard kinematic variables. By examining correlations between kinematic variables commonly used in LHC analyses and invariant masses obtained with multiple jet reconstructions, we find that using multiple radii is still helpful even on top of standard kinematic variables when combined with boosted decision trees. These results suggest that including multiple event interpretations in a realistic search for Higgs to bb would give additional sensitivity over traditional approaches.Comment: 13 pages, 2 figure

Measurement of dijet production with a veto on additional central jet activity in pp collisions at √s = 7TeV using the ATLAS detector

A measurement of jet activity in the rapidity interval bounded by a dijet system is presented. Events are vetoed if a jet with transverse momentum greater than 20 GeV is found between the two boundary jets. The fraction of dijet events that survive the jet veto is presented for boundary jets that are separated by up to six units of rapidity and with mean transverse momentum 50 < p_T < 500 GeV. The mean multiplicity of jets above the veto scale in the rapidity interval bounded by the dijet system is also presented as an alternative method for quantifying perturbative QCD emission. The data are compared to a next-to-leading order plus parton shower prediction from the powheg-box, an all-order resummation using the hej calculation and the pythia, herwig++ and alpgen event generators. The measurement was performed using pp collisions at √s=7 TeV using data recorded by the ATLAS detector in 2010

A search for tt resonances with the ATLAS detector in 2.05 fb^(−1) of proton-proton collisions at √s =7 TeV

A search for top quark pair resonances in final states containing at least one electron or muon has been performed with the ATLAS experiment at the CERN Large Hadron Collider. The search uses a data sample corresponding to an integrated luminosity of 2.05 fb^(−1), which was recorded in 2011 at a proton-proton centre-of-mass energy of 7 TeV. No evidence for a resonance is found and limits are set on the production cross-section times branching ratio to tt for narrow and wide resonances. For narrow Z′ bosons, the observed 95 % Bayesian credibility level limits range from 9.3 pb to 0.95 pb for masses in the range of m_(Z′)=500 GeV to m_(Z′)=1300 GeV. The corresponding excluded mass region for a leptophobic topcolour Z′ boson (Kaluza-Klein gluon excitation in the Randall-Sundrum model) is m_(Z′)<880 GeV (m_(gKK)< 1130 GeV)

Efecto de la edad y el nivel de vitamina E en dietas de pollos broiler sobre la modulación de la respuesta inmune.

La vitamina E pertenece al grupo de nutrientes con capacidad reguladora del sistema inmune (Koutsos y Klasing, 2008). En aves, la vitamina E induce cambios tanto en el sistema inmune innato como en el específico, mejora la función fagocítica de los macrófagos, amortigua la respuesta en fase aguda, disminuye la proporción de heterófilos y potencia la síntesis de anticuerpos (Koutsos y Klasing, 2008; Khan et al., 2012). Recientemente se ha demostrado que parte del efecto de la vitamina E está ligado a su capacidad de actuar directamente sobre factores de transcripción nuclear que modulan la expresión de citoquinas, tales como el factor-Kappa B o el PPAR γ (Koutsos y Klasing, 2008; Nakamura y Omaye, 2009). Por otro lado, el impacto de la vitamina E sobre la modulación del sistema inmune viene definido por factores tales como la edad y la relación dosis-respuesta. En broiler la inclusión en la dieta de niveles moderadamente superiores (25-50 UI/kg dieta) al recomendado por el National Research Council (NRC, 1994; 10 UI/kg) aumenta los títulos de anticuerpos tras la vacunación (Friedman et al., 1998; Leshchinsky y Klasing, 2001; Lin y Chang, 2006). Sin embargo, niveles superiores a 150 UI/kg tienen un efecto supresor sobre la producción de anticuerpos (Koutsos y Klasing, 2008). En relación a la edad es importante determinar aquellos periodos o “ventanas” en los que es necesario estimular el sistema inmune (Kogut, 2009). Un periodo a considerar sería el de las dos primeras semanas de vida del pollo debido a la menor funcionalidad de macrófagos y heterófilos (Kogut, 2009). El presente trabajo tiene como objetivo evaluar el efecto del nivel de Vitamina E y la edad sobre la modulación de la respuesta inmune en pollos. Para ello se estudió el efecto de la inclusión de 40 y 160 ppm de vitamina E en la dieta sobre la expresión de la interleuquina 2 (IL 2), el interferón gamma (IFN γ) y el factor de crecimiento mielomonocítico (MGF) en el bazo de los animales a los 7 y 21 días de edad

Anthropogenic ecosystem disturbance and the recovery debt

Ecosystem recovery from anthropogenic disturbances, either without human intervention or assisted by ecological restoration, is increasingly occurring worldwide. As ecosystems progress through recovery, it is important to estimate any resulting deficit in biodiversity and functions. Here we use data from 3,035 sampling plots worldwide, to quantify the interim reduction of biodiversity and functions occurring during the recovery process (that is, the 'recovery debt'). Compared with reference levels, recovering ecosystems run annual deficits of 46-51% for organism abundance, 27-33% for species diversity, 32-42% for carbon cycling and 31-41% for nitrogen cycling. Our results are consistent across biomes but not across degrading factors. Our results suggest that recovering and restored ecosystems have less abundance, diversity and cycling of carbon and nitrogen than 'undisturbed' ecosystems, and that even if complete recovery is reached, an interim recovery debt will accumulate. Under such circumstances, increasing the quantity of less-functional ecosystems through ecological restoration and offsetting are inadequate alternatives to ecosystem protection

Measurement of the inclusive jet cross-section in pp collisions at √s = 2.76 TeV and comparison to the inclusive jet cross-section at √s = 7 TeV using the ATLAS detector

The inclusive jet cross-section has been measured in proton–proton collisions at √s = 2.76 TeV in a dataset corresponding to an integrated luminosity of 0.20^(-1) collected with the ATLAS detector at the Large Hadron Collider in 2011. Jets are identified using the anti-k_t algorithm with two radius parameters of 0.4 and 0.6. The inclusive jet double-differential cross-section is presented as a function of the jet transverse momentum p_T and jet rapidity y, covering a range of 20≤p_T<430 GeV and |y|<4.4. The ratio of the cross-section to the inclusive jet cross-section measurement at √s = 7 TeV , published by the ATLAS Collaboration, is calculated as a function of both transverse momentum and the dimensionless quantity x_T =2 p_T/√s, in bins of jet rapidity. The systematic uncertainties on the ratios are significantly reduced due to the cancellation of correlated uncertainties in the two measurements. Results are compared to the prediction from next-to-leading order perturbative QCD calculations corrected for non-perturbative effects, and next-to-leading order Monte Carlo simulation. Furthermore, the ATLAS jet cross-section measurements at √s = 2.76 TeV and √s = 7 TeV are analysed within a framework of next-to-leading order perturbative QCD calculations to determine parton distribution functions of the proton, taking into account the correlations between the measurements

Search for a light charged Higgs boson in the decay channel H^+→cs in tt events using pp collisions at s√=7 TeV with the ATLAS detector

A search for a charged Higgs boson (H^+) in tt decays is presented, where one of the top quarks decays via t→H^+ b, followed by H^+→ two jets (cs). The other top quark decays to Wb, where the W boson then decays into a lepton (e/μ) and a neutrino. The data were recorded in pp collisions at s√=7 TeV by the ATLAS detector at the LHC in 2011, and correspond to an integrated luminosity of 4.7 fb^(−1). With no observation of a signal, 95 % confidence level (CL) upper limits are set on the decay branching ratio of top quarks to charged Higgs bosons varying between 5 % and 1 % for H^+ masses between 90 GeV and 150 GeV, assuming B(H^+→cs)=100%

Measurement of the tt production cross section in the tau + jets channel using the ATLAS detector

A measurement of the top quark pair production cross section in the final state with a hadronically decaying tau lepton and jets is presented. The analysis is based on proton–proton collision data recorded by the ATLAS experiment at the LHC, with a centre-of-mass energy of 7 TeV. The data sample corresponds to an integrated luminosity of 1.67 fb^(−1). The cross section is measured to be σ_(tt)=194±18 (stat.)±46 (syst.) pb and is in agreement with other measurements and with the Standard Model prediction

Multi-channel search for squarks and gluinos in √s = 7 TeV pp collisions with the ATLAS detector at the LHC

A search for supersymmetric particles in final states with zero, one, and two leptons, with and without jets identified as originating from b-quarks, in 4.7 fb^(−1) of s√=7 TeV pp collisions produced by the Large Hadron Collider and recorded by the ATLAS detector is presented. The search uses a set of variables carrying information on the event kinematics transverse and parallel to the beam line that are sensitive to several topologies expected in supersymmetry. Mutually exclusive final states are defined, allowing a combination of all channels to increase the search sensitivity. No deviation from the Standard Model expectation is observed. Upper limits at 95 % confidence level on visible cross-sections for the production of new particles are extracted. Results are interpreted in the context of the constrained minimal supersymmetric extension to the Standard Model and in supersymmetry-inspired models with diverse, high-multiplicity final states

Measurement of Multi-jet Production Cross Section at a Center-of-Mass Energy of 7 TeV at the Large Hadron Collider with the ATLAS Detector

Inclusive multi-jet production is studied using proton-proton collisions at a center-of-mass energy of 7 TeV. The data sample corresponds to an integrated luminosity of 2.43 pb-1, and uses a subset of the data collected by the ATLAS detector in 2010. Measurements of multi-jet production cross sections with up to six jets are presented and compared to both leading-order predictions enhanced by a parton shower and next-to-leading-order calculations. Generally, agreement is found between data and leading-order and next-to-leading-order predictions. Regions of phase space or observables in which pure parton-shower simulations differ from the measurements are well described by leading-order calculations that combine matrix-element calculations with several outgoing partons in the final state to parton-shower simulations. Measurements compared to next-to-leading-order calculations are shown to be sensitive to the value of the strong coupling constant