326 research outputs found

    Jet energy measurement with the ATLAS detector in proton-proton collisions at root s=7 TeV

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    The jet energy scale and its systematic uncertainty are determined for jets measured with the ATLAS detector at the LHC in proton-proton collision data at a centre-of-mass energy of √s = 7TeV corresponding to an integrated luminosity of 38 pb-1. Jets are reconstructed with the anti-kt algorithm with distance parameters R=0. 4 or R=0. 6. Jet energy and angle corrections are determined from Monte Carlo simulations to calibrate jets with transverse momenta pT≄20 GeV and pseudorapidities {pipe}η{pipe}<4. 5. The jet energy systematic uncertainty is estimated using the single isolated hadron response measured in situ and in test-beams, exploiting the transverse momentum balance between central and forward jets in events with dijet topologies and studying systematic variations in Monte Carlo simulations. The jet energy uncertainty is less than 2. 5 % in the central calorimeter region ({pipe}η{pipe}<0. 8) for jets with 60≀pT<800 GeV, and is maximally 14 % for pT<30 GeV in the most forward region 3. 2≀{pipe}η{pipe}<4. 5. The jet energy is validated for jet transverse momenta up to 1 TeV to the level of a few percent using several in situ techniques by comparing a well-known reference such as the recoiling photon pT, the sum of the transverse momenta of tracks associated to the jet, or a system of low-pT jets recoiling against a high-pT jet. More sophisticated jet calibration schemes are presented based on calorimeter cell energy density weighting or hadronic properties of jets, aiming for an improved jet energy resolution and a reduced flavour dependence of the jet response. The systematic uncertainty of the jet energy determined from a combination of in situ techniques is consistent with the one derived from single hadron response measurements over a wide kinematic range. The nominal corrections and uncertainties are derived for isolated jets in an inclusive sample of high-pT jets. Special cases such as event topologies with close-by jets, or selections of samples with an enhanced content of jets originating from light quarks, heavy quarks or gluons are also discussed and the corresponding uncertainties are determined. © 2013 CERN for the benefit of the ATLAS collaboration

    Search for the neutral Higgs bosons of the minimal supersymmetric standard model in pp collisions at root s=7 TeV with the ATLAS detector

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    A search for neutral Higgs bosons of the Minimal Supersymmetric Standard Model (MSSM) is reported. The analysis is based on a sample of proton-proton collisions at a centre-of-mass energy of 7TeV recorded with the ATLAS detector at the Large Hadron Collider. The data were recorded in 2011 and correspond to an integrated luminosity of 4.7 fb-1 to 4.8 fb-1. Higgs boson decays into oppositely-charged muon or τ lepton pairs are considered for final states requiring either the presence or absence of b-jets. No statistically significant excess over the expected background is observed and exclusion limits at the 95% confidence level are derived. The exclusion limits are for the production cross-section of a generic neutral Higgs boson, φ, as a function of the Higgs boson mass and for h/A/H production in the MSSM as a function of the parameters mA and tan ÎČ in the mhmax scenario for mA in the range of 90GeV to 500 GeV. Copyright CERN

    Observation of associated near-side and away-side long-range correlations in √sNN=5.02  TeV proton-lead collisions with the ATLAS detector

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    Two-particle correlations in relative azimuthal angle (Δϕ) and pseudorapidity (Δη) are measured in √sNN=5.02  TeV p+Pb collisions using the ATLAS detector at the LHC. The measurements are performed using approximately 1  Όb-1 of data as a function of transverse momentum (pT) and the transverse energy (ÎŁETPb) summed over 3.1<η<4.9 in the direction of the Pb beam. The correlation function, constructed from charged particles, exhibits a long-range (2<|Δη|<5) “near-side” (Δϕ∌0) correlation that grows rapidly with increasing ÎŁETPb. A long-range “away-side” (Δϕ∌π) correlation, obtained by subtracting the expected contributions from recoiling dijets and other sources estimated using events with small ÎŁETPb, is found to match the near-side correlation in magnitude, shape (in Δη and Δϕ) and ÎŁETPb dependence. The resultant Δϕ correlation is approximately symmetric about π/2, and is consistent with a dominant cos⁥2Δϕ modulation for all ÎŁETPb ranges and particle pT

    Measurement of the cross-section of high transverse momentum vector bosons reconstructed as single jets and studies of jet substructure in pp collisions at √s = 7 TeV with the ATLAS detector

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    This paper presents a measurement of the cross-section for high transverse momentum W and Z bosons produced in pp collisions and decaying to all-hadronic final states. The data used in the analysis were recorded by the ATLAS detector at the CERN Large Hadron Collider at a centre-of-mass energy of √s = 7 TeV;{\rm Te}{\rm V}andcorrespondtoanintegratedluminosityof and correspond to an integrated luminosity of 4.6\;{\rm f}{{{\rm b}}^{-1}}.ThemeasurementisperformedbyreconstructingtheboostedWorZbosonsinsinglejets.ThereconstructedjetmassisusedtoidentifytheWandZbosons,andajetsubstructuremethodbasedonenergyclusterinformationinthejetcentre−of−massframeisusedtosuppressthelargemulti−jetbackground.Thecross−sectionforeventswithahadronicallydecayingWorZboson,withtransversemomentum. The measurement is performed by reconstructing the boosted W or Z bosons in single jets. The reconstructed jet mass is used to identify the W and Z bosons, and a jet substructure method based on energy cluster information in the jet centre-of-mass frame is used to suppress the large multi-jet background. The cross-section for events with a hadronically decaying W or Z boson, with transverse momentum {{p}_{{\rm T}}}\gt 320\;{\rm Ge}{\rm V}andpseudorapidity and pseudorapidity |\eta |\lt 1.9,ismeasuredtobe, is measured to be {{\sigma }_{W+Z}}=8.5\pm 1.7$ pb and is compared to next-to-leading-order calculations. The selected events are further used to study jet grooming techniques

    Search for R-parity-violating supersymmetry in events with four or more leptons in sqrt(s) =7 TeV pp collisions with the ATLAS detector

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    A search for new phenomena in final states with four or more leptons (electrons or muons) is presented. The analysis is based on 4.7 fb−1 of s=7  TeV \sqrt{s}=7\;\mathrm{TeV} proton-proton collisions delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in two signal regions: one that requires moderate values of missing transverse momentum and another that requires large effective mass. The results are interpreted in a simplified model of R-parity-violating supersymmetry in which a 95% CL exclusion region is set for charged wino masses up to 540 GeV. In an R-parity-violating MSUGRA/CMSSM model, values of m 1/2 up to 820 GeV are excluded for 10 < tan ÎČ < 40

    Search for high-mass resonances decaying to dilepton final states in pp collisions at s√=7 TeV with the ATLAS detector

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    The ATLAS detector at the Large Hadron Collider is used to search for high-mass resonances decaying to an electron-positron pair or a muon-antimuon pair. The search is sensitive to heavy neutral Zâ€Č gauge bosons, Randall-Sundrum gravitons, Z * bosons, techni-mesons, Kaluza-Klein Z/Îł bosons, and bosons predicted by Torsion models. Results are presented based on an analysis of pp collisions at a center-of-mass energy of 7 TeV corresponding to an integrated luminosity of 4.9 fb−1 in the e + e − channel and 5.0 fb−1 in the ÎŒ + ÎŒ −channel. A Z â€Č boson with Standard Model-like couplings is excluded at 95 % confidence level for masses below 2.22 TeV. A Randall-Sundrum graviton with coupling k/MPl=0.1 is excluded at 95 % confidence level for masses below 2.16 TeV. Limits on the other models are also presented, including Technicolor and Minimal Zâ€Č Models

    Search for new phenomena in final states with an energetic jet and large missing transverse momentum in pp collisions at √ s = 8 TeV with the ATLAS detector

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    Results of a search for new phenomena in final states with an energetic jet and large missing transverse momentum are reported. The search uses 20.3 fb−1 of √ s = 8 TeV data collected in 2012 with the ATLAS detector at the LHC. Events are required to have at least one jet with pT > 120 GeV and no leptons. Nine signal regions are considered with increasing missing transverse momentum requirements between Emiss T > 150 GeV and Emiss T > 700 GeV. Good agreement is observed between the number of events in data and Standard Model expectations. The results are translated into exclusion limits on models with either large extra spatial dimensions, pair production of weakly interacting dark matter candidates, or production of very light gravitinos in a gauge-mediated supersymmetric model. In addition, limits on the production of an invisibly decaying Higgs-like boson leading to similar topologies in the final state are presente

    Productivity trends and collaboration patterns: A diachronic study in the eating disorders field

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    [EN] Objective The present study seeks to extend previous bibliometric studies on eating disorders (EDs) by including a time-dependent analysis of the growth and evolution of multi-author collaborations and their correlation with ED publication trends from 1980 to 2014 (35 years). Methods Using standardized practices, we searched Web of Science (WoS) Core Collection (WoSCC) (indexes: Science Citation Index-Expanded [SCIE], & Social Science Citation Index [SSCI]) and Scopus (areas: Health Sciences, Life Sciences, & Social Sciences and Humanities) to identify a large sample of articles related to EDs. We then submitted our sample of articles to bibliometric and graph theory analyses to identify co-authorship and social network patterns. Results We present a large number of detailed findings, including a clear pattern of scientific growth measured as number of publications per five-year period or quinquennium (Q), a tremendous increase in the number of authors attracted by the ED subject, and a very high and steady growth in collaborative work. Conclusions We inferred that the noted publication growth was likely driven by the noted increase in the number of new authors per Q. Social network analyses suggested that collaborations within ED follow patters of interaction that are similar to well established and recognized disciplines, as indicated by the presence of a Âżgiant clusterÂż, high cluster density, and the replication of the Âżsmall worldÂż phenomenonÂżthe principle that we are all linked by short chains of acquaintances.This work was performed with a subsidy from Universidad Catolica de Valencia "San Vicente Martir" to resarch group INDOTEI: Evaluacion de la Ciencia, for the years 2016-2017. This work is benefited from Spanish Government assistance through Government Delegation for the National Drugs Plan of the Ministry of Health, Social Services and Equality (project 2016/028); and National R+D+I (projects: CS02012-39632-C02-01 and CS02015-65594-C2-2-R) and 2015-Networks of Excellence Call (project CS02015-71867-REDT) of the Ministry of Economy and Competitiveness.Valderrama Zurian, JC.; Aguilar-Moya, R.; Cepeda-Benito, A.; Melero-Fuentes, D.; Navarro-Moreno, MÁ.; GandĂ­a-Balaguer, A.; Aleixandre-Benavent, R. (2017). Productivity trends and collaboration patterns: A diachronic study in the eating disorders field. PLoS ONE. 12(8):1-17. https://doi.org/10.1371/journal.pone.0182760S117128McClelland, J., Bozhilova, N., Campbell, I., & Schmidt, U. (2013). A Systematic Review of the Effects of Neuromodulation on Eating and Body Weight: Evidence from Human and Animal Studies. European Eating Disorders Review, 21(6), 436-455. doi:10.1002/erv.2256Lancelot, C., Brooks-Gunn, J., Warren, M. P., & Newman, D. L. (1991). Comparison of DSM-III and DSM-III-R bulimia nervosa classifications for psychopathology and other eating behaviors. International Journal of Eating Disorders, 10(1), 57-66. doi:10.1002/1098-108x(199101)10:13.0.co;2-tWONDERLICH, S. A., CROSBY, R. D., JOINER, T., PETERSON, C. B., BARDONE-CONE, A., KLEIN, M., 
 VRSHEK, S. (2005). Personality subtyping and bulimia nervosa: psychopathological and genetic correlates. Psychological Medicine, 35(5), 649-657. doi:10.1017/s0033291704004234Spitzer, R. L., Devlin, M. J., Walsh, B. T., Hasin, D., Wing, R., Marcus, M. D., 
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The Increasing Dominance of Teams in Production of Knowledge. Science, 316(5827), 1036-1039. doi:10.1126/science.1136099Kumar, S. (2015). Co-authorship networks: a review of the literature. Aslib Journal of Information Management, 67(1), 55-73. doi:10.1108/ajim-09-2014-0116BarabĂĄsi, A. ., Jeong, H., NĂ©da, Z., Ravasz, E., Schubert, A., & Vicsek, T. (2002). Evolution of the social network of scientific collaborations. Physica A: Statistical Mechanics and its Applications, 311(3-4), 590-614. doi:10.1016/s0378-4371(02)00736-7Newman, M. E. J. (2004). Coauthorship networks and patterns of scientific collaboration. Proceedings of the National Academy of Sciences, 101(Supplement 1), 5200-5205. doi:10.1073/pnas.0307545100Aleixandre-Benavent, R., & Alonso-Arroyo, A. (2011). Indicadores bibliomĂ©tricos, patologĂ­a del aparato respiratorio y reducciĂłn del consumo de tabaco. Revista de PatologĂ­a Respiratoria, 14(1), 1-3. doi:10.1016/s1576-9895(11)70095-9Pino-DĂ­az, J., JimĂ©nez-Contreras, E., RuĂ­z-Baños, R., & BailĂłn-Moreno, R. (2011). EvaluaciĂłn de redes tecnocientĂ­ficas: la red española sobre Áreas Protegidas, segĂșn la Web of Science. Revista española de DocumentaciĂłn CientĂ­fica, 34(3), 301-333. doi:10.3989/redc.2011.3.804Valderrama-ZuriĂĄn, J.-C., Aguilar-Moya, R., Melero-Fuentes, D., & Aleixandre-Benavent, R. (2015). A systematic analysis of duplicate records in Scopus. Journal of Informetrics, 9(3), 570-576. doi:10.1016/j.joi.2015.05.002Guardiola-Wanden-Berghe, R., Sanz-Valero, J., & Wanden-Berghe, C. (2012). Medical subject headings versus American Psychological Association Index Terms: indexing eating disorders. Scientometrics, 94(1), 305-311. doi:10.1007/s11192-012-0866-7Soh, N., Walter, G., Touyz, S., Russell, J., Malhi, G. S., & Hunt, G. E. (2012). Food for thought: Comparison of citations received from articles appearing in specialized eating disorder journals versus general psychiatry journals. International Journal of Eating Disorders, 45(8), 990-994. doi:10.1002/eat.22036Theander, S. S. (2004). Trends in the literature on eating disorders over 36 years(1965-2000): terminology, interpretation and treatment. European Eating Disorders Review, 12(1), 4-17. doi:10.1002/erv.559Kawamura, M., Thomas, C. D. L., Tsurumoto, A., Sasahara, H., & Kawaguchi, Y. (2000). Lotka’s law and productivity index of authors in a scientific journal. Journal of Oral Science, 42(2), 75-78. doi:10.2334/josnusd.42.75Lawani SM. Quality, collaboration and citations in cancer research: A bibliometric study. PhD thesis. Florida State University, Tallahassee. 1980.Watts, D. J., & Strogatz, S. H. (1998). Collective dynamics of ‘small-world’ networks. Nature, 393(6684), 440-442. doi:10.1038/30918Jacomy, M., Venturini, T., Heymann, S., & Bastian, M. (2014). ForceAtlas2, a Continuous Graph Layout Algorithm for Handy Network Visualization Designed for the Gephi Software. PLoS ONE, 9(6), e98679. doi:10.1371/journal.pone.0098679Pike, K. M., & Dunne, P. E. (2015). The rise of eating disorders in Asia: a review. Journal of Eating Disorders, 3(1). doi:10.1186/s40337-015-0070-2El Ghoch, M., Soave, F., Calugi, S., & Dalle Grave, R. (2013). Eating Disorders, Physical Fitness and Sport Performance: A Systematic Review. Nutrients, 5(12), 5140-5160. doi:10.3390/nu5125140Jones, A. W. (2007). The distribution of forensic journals, reflections on authorship practices, peer-review and role of the impact factor. Forensic Science International, 165(2-3), 115-128. doi:10.1016/j.forsciint.2006.05.013Baker, T., Hatsukami, D., Lerman, C., O’Malley, S., Shields, A., & Fiore, M. (2003). Transdisciplinary science applied to the evaluation of treatments for tobacco use. 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    Measurements of normalized differential cross sections for tt̄ production in pp collisions at √(s)=7  TeV using the ATLAS detector

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    Measurements of normalized differential cross sections for top-quark pair production are presented as a function of the top-quark transverse momentum, and of the mass, transverse momentum, and rapidity of the t¯t system, in proton–proton collisions at a center-of-mass energy of √s=7  TeV. The data set corresponds to an integrated luminosity of 4.6  fb−1, recorded in 2011 with the ATLAS detector at the CERN Large Hadron Collider. Events are selected in the lepton+jets channel, requiring exactly one lepton and at least four jets with at least one of the jets tagged as originating from a b-quark. The measured spectra are corrected for detector efficiency and resolution effects and are compared to several Monte Carlo simulations and theory calculations. The results are in fair agreement with the predictions in a wide kinematic range. Nevertheless, data distributions are softer than predicted for higher values of the mass of the t¯t system and of the top-quark transverse momentum. The measurements can also discriminate among different sets of parton distribution functions

    Flavor tagged time-dependent angular analysis of the B0s → J/ψϕ decay and extraction of ΔΓs and the weak phase ϕs in ATLAS

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    A measurement of the B0s→J/ψϕ decay parameters, updated to include flavor tagging is reported using 4.9  fb−Âč of integrated luminosity collected by the ATLAS detector from √s=7  TeV pp collisions recorded in 2011 at the LHC. The values measured for the physical parameters are ϕs=0.12±0.25(stat)±0.05(syst)  rad ΔΓs=0.053±0.021(stat)±0.010(syst)  ps−Âč Γs=0.677±0.007(stat)±0.004(syst)  ps−Âč |A∄(0)|2=0.220±0.008(stat)±0.009(syst) |A0(0)|2=0.529±0.006(stat)±0.012(syst) Ύ⊄=3.89±0.47(stat)±0.11(syst)  rad where the parameter ΔΓs is constrained to be positive. The S-wave contribution was measured and found to be compatible with zero. Results for ϕs and ΔΓs are also presented as 68% and 95% likelihood contours, which show agreement with the Standard Model expectations
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