2,945 research outputs found

    Search for f1(1285)→π+π−π0f_1(1285) \to \pi^+\pi^-\pi^0 decay with VES detector

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    The isospin violating decay f1(1285)→π+π−π0f_1(1285)\to\pi^+\pi^-\pi^0 has been studied at VES facility. This study is based at the statistics acquired in π−Be\pi^- Be interactions at 27, 36.6 and 41 GeV/c in diffractive reaction π−N→(f1π−)N\pi^- N \to (f_1 \pi^-) N. The f1(1285)→π+π−π0f_1(1285) \to \pi^+\pi^-\pi^0 decay is observed. The ratio of decay probabilities BR(f1(1285)→π+π−π0)BR(f_1(1285) \to \pi^+\pi^-\pi^0) to BR(f1(1285)→ηπ+π−)⋅BR(η→γγ)BR(f_1(1285) \to \eta \pi^+\pi^-) \cdot BR(\eta \to \gamma\gamma) is ∌ 1.4\sim\:1.4%.Comment: 10 pages, 8 figures, presented at XII Conference on Hadron Spectroscop

    Electroweak diboson production at ATLAS

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    This paper is giving an overview of recent ATLAS results on the production cross sections of gauge boson pairs decaying leptonically using data from pp collisions at √s = 13TeV for ZZ and at √s = 8TeV forW±Z and W±W± at the LHC at CERN. The cross sections are found to be in agreement with the expectations from the Standard Model within the estimated uncertainties. The production cross section measurements also allow for studies of anomalous triple and quartic gauge couplings for which 95% conïŹdence level limits are set

    Study of TileCal Sampling Fraction for Improvement of Monte-Carlo Data Reconstruction

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    In this work we made a detailed calculation of Tile Calorimeter Sampling Fraction parameter (TSF) using single electron and pion Geant4 Monte-Carlo simulation of ATLAS hadronic calorimeter (TileCal) within ATHENA --- common software framework of ATLAS. Our study was based on MC Truth data provided by special Geant4 MC simulation objects --- Calibration Hits, design which was implemented in TileCal simulation by our group. We used this TSF value for reconstruction of TileCal single pions simulation data. It was done for ATLAS Combined test beam 2004 (CTB2004) configuration setup. Results of the reconstruction were compared with MC Truth and CTB2004 reconstructed experimental data. Good agreement between them shows quite evident improvement in TileCal MC data reconstruction of hadronic shower energy in electromagnetic scale

    The Effect of Tile Light Collection Reduction along Radius on the ATLAS Tile Calorimeter Uniformity

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    We report on the light collection non uniformity of trapezoidal scintillating tiles along radius and its consequence on the miscalibration of the middle and back longitudinal calorimeter samplings. We discuss the need to apply extra corrections to the cells response after equalization and corrections obtained by the cesium calibration system, in order to bring all three longitudinal samplings to the right electromagnetic scale

    Electromagnetic Cell Level Calibration for ATLAS Tile Calorimeter Modules

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    We have determined the electromagnetic calibration constants of 11% TileCal modules exposed to electron beams with incident angles of 20 and 90 degrees. The gain of all the calorimeter cells have been pre-equalized using the radioactive Cs-source that will be also used in situ. The average values for these modules are equal to: for the flat filter method 1.154+/-0.002 pC/GeV and 1.192+/-0.002 pC/GeV for 20 and 90 degrees, for the fit method 1.040+/-0.002 pC/GeV and 1.068+/-0.003 pC/GeV, respectively. These average values for all cells of calibrated modules agree with the weighted average calibration constants for separate modules within the errors. Using the individual calibration constants for every module the RMS spread value of constants will be 1.9+/-0.1 %. In the case of the global constant this value will be 2.6+/-0.1 %. Finally, we present the global constants which should be used for the electromagnetic calibration of the ATLAS Tile hadronic calorimeter data in the ATHENA framework. These constants are equal to 1.15 pC/GeV in the case of the flat filter method and 1.04 pC/GeV for the fit one

    Measurement of the cross-section and charge asymmetry of WW bosons produced in proton-proton collisions at s=8\sqrt{s}=8 TeV with the ATLAS detector

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    This paper presents measurements of the W+→Ό+ÎœW^+ \rightarrow \mu^+\nu and W−→Ό−ΜW^- \rightarrow \mu^-\nu cross-sections and the associated charge asymmetry as a function of the absolute pseudorapidity of the decay muon. The data were collected in proton--proton collisions at a centre-of-mass energy of 8 TeV with the ATLAS experiment at the LHC and correspond to a total integrated luminosity of 20.2~\mbox{fb^{-1}}. The precision of the cross-section measurements varies between 0.8% to 1.5% as a function of the pseudorapidity, excluding the 1.9% uncertainty on the integrated luminosity. The charge asymmetry is measured with an uncertainty between 0.002 and 0.003. The results are compared with predictions based on next-to-next-to-leading-order calculations with various parton distribution functions and have the sensitivity to discriminate between them.Comment: 38 pages in total, author list starting page 22, 5 figures, 4 tables, submitted to EPJC. All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/STDM-2017-13

    Search for chargino-neutralino production with mass splittings near the electroweak scale in three-lepton final states in √s=13 TeV pp collisions with the ATLAS detector

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    A search for supersymmetry through the pair production of electroweakinos with mass splittings near the electroweak scale and decaying via on-shell W and Z bosons is presented for a three-lepton final state. The analyzed proton-proton collision data taken at a center-of-mass energy of √s=13  TeV were collected between 2015 and 2018 by the ATLAS experiment at the Large Hadron Collider, corresponding to an integrated luminosity of 139  fb−1. A search, emulating the recursive jigsaw reconstruction technique with easily reproducible laboratory-frame variables, is performed. The two excesses observed in the 2015–2016 data recursive jigsaw analysis in the low-mass three-lepton phase space are reproduced. Results with the full data set are in agreement with the Standard Model expectations. They are interpreted to set exclusion limits at the 95% confidence level on simplified models of chargino-neutralino pair production for masses up to 345 GeV

    Single hadron response measurement and calorimeter jet energy scale uncertainty with the ATLAS detector at the LHC

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    The uncertainty on the calorimeter energy response to jets of particles is derived for the ATLAS experiment at the Large Hadron Collider (LHC). First, the calorimeter response to single isolated charged hadrons is measured and compared to the Monte Carlo simulation using proton-proton collisions at centre-of-mass energies of sqrt(s) = 900 GeV and 7 TeV collected during 2009 and 2010. Then, using the decay of K_s and Lambda particles, the calorimeter response to specific types of particles (positively and negatively charged pions, protons, and anti-protons) is measured and compared to the Monte Carlo predictions. Finally, the jet energy scale uncertainty is determined by propagating the response uncertainty for single charged and neutral particles to jets. The response uncertainty is 2-5% for central isolated hadrons and 1-3% for the final calorimeter jet energy scale.Comment: 24 pages plus author list (36 pages total), 23 figures, 1 table, submitted to European Physical Journal
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