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ATLAS Collaboration(Aad, G. et al), Amoros, G., Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Ferrer, A., et al. (2012). Measurement of D*(+/-) meson production in jets from pp collisions at root s=7 TeV with the ATLAS detector. Phys. Rev. D, 85(5), 052005–22pp.
Abstract: This paper reports a measurement of D*(+/-) meson production in jets from proton- proton collisions at a center- of- mass energy of root s = 7 TeV at the CERN Large Hadron Collider. The measurement is based on a data sample recorded with the ATLAS detector with an integrated luminosity of 0.30 pb(-1) for jets with transverse momentum between 25 and 70 GeV in the pseudorapidity range vertical bar eta vertical bar <2.5. D*(+/-) mesons found in jets are fully reconstructed in the decay chain: D*(+/-)-> D-0 pi(+), D-0 -> K-pi(+), and its charge conjugate. The production rate is found to be N(D*(+/-))/N(jet) = 0.025 +/- 0.001(stat.) +/- 0.004(syst.) for D*(+/-) mesons that carry a fraction z of the jet momentum in the range 0.3< z< 1. Monte Carlo predictions fail to describe the data at small values of z, and this is most marked at low jet transverse momentum.
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ATLAS Collaboration(Aad, G. et al), Alvarez Piqueras, D., Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Fernandez Martinez, P., et al. (2016). Identification of boosted, hadronically decaying W bosons and comparisons with ATLAS data taken at root s=8 TeV. Eur. Phys. J. C, 76(3), 154–47pp.
Abstract: This paper reports a detailed study of techniques for identifying boosted, hadronically decaying W bosons using 20.3 fb(-1) of proton-proton collision data collected by the ATLAS detector at the LHC at a centre-of-mass energy root s = 8 TeV. A range of techniques for optimising the signal jet mass resolution are combined with various jet substructure variables. The results of these studies in Monte Carlo simulations show that a simple pairwise combination of groomed jet mass and one substructure variable can provide a 50 % efficiency for identifying W bosons with transverse momenta larger than 200 GeV while maintaining multijet background efficiencies of 2-4% for jets with the same transverse momentum. These signal and background efficiencies are confirmed in data for a selection of tagging techniques.
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ATLAS Collaboration(Aad, G. et al), Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Ferrer, A., Fiorini, L., et al. (2014). Measurement of the muon reconstruction performance of the ATLAS detector using 2011 and 2012 LHC proton-proton collision data. Eur. Phys. J. C, 74(11), 3130–34pp.
Abstract: This paper presents the performance of the ATLAS muon reconstruction during the LHC run with pp collisions at root s = 7-8 TeV in 2011-2012, focusing mainly on data collected in 2012. Measurements of the reconstruction efficiency and of the momentum scale and resolution, based on large reference samples of J/psi -> μmu, Z -> μμand gamma -> μμdecays, are presented and compared to Monte Carlo simulations. Corrections to the simulation, to be used in physics analysis, are provided. Over most of the covered phase space (muon |eta| < 2.7 and 5 less than or similar to p(T) less than or similar to 100 GeV) the efficiency is above 99% and is measured with per-mille precision. The momentum resolution ranges from 1.7% at central rapidity and for transverse momentum p(T) similar or equal to 10 GeV, to 4% at large rapidity and p(T) similar or equal to 100 GeV. The momentum scale is known with an uncertainty of 0.05% to 0.2% depending on rapidity. A method for the recovery of final state radiation from the muons is also presented.
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ATLAS Collaboration(Aad, G. et al), Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Ferrer, A., Fiorini, L., et al. (2014). Electron and photon energy calibration with the ATLAS detector using LHC Run 1 data. Eur. Phys. J. C, 74(10), 3071–48pp.
Abstract: This paper presents the electron and photon energy calibration achieved with the ATLAS detector using about 25 fb(-1) of LHC proton-proton collision data taken at centre-of-mass energies of root s = 7 and 8 TeV. The reconstruction of electron and photon energies is optimised using multivariate algorithms. The response of the calorimeter layers is equalised in data and simulation, and the longitudinal profile of the electromagnetic showers is exploited to estimate the passive material in front of the calorimeter and reoptimise the detector simulation. After all corrections, the Z resonance is used to set the absolute energy scale. For electrons from Z decays, the achieved calibration is typically accurate to 0.05% in most of the detector acceptance, rising to 0.2% in regions with large amounts of passive material. The remaining inaccuracy is less than 0.2-1% for electrons with a transverse energy of 10 GeV, and is on average 0.3% for photons. The detector resolution is determined with a relative inaccuracy of less than 10% for electrons and photons up to 60 GeV transverse energy, rising to 40% for transverse energies above 500 GeV.
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ATLAS Collaboration(Aad, G. et al), Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Fassi, F., Ferrer, A., et al. (2013). Performance of jet substructure techniques for large-R jets in proton-proton collisions at root s=7 TeV using the ATLAS detector. J. High Energy Phys., 09(9), 076–83pp.
Abstract: This paper presents the application of a variety of techniques to study jet substructure. The performance of various modified jet algorithms, or jet grooming techniques, for several jet types and event topologies is investigated for jets with transverse momentum larger than 300 GeV. Properties of jets subjected to the mass-drop filtering, trimming, and pruning algorithms are found to have a reduced sensitivity to multiple proton-proton interactions, are more stable at high luminosity and improve the physics potential of searches for heavy boosted objects. Studies of the expected discrimination power of jet mass and jet substructure observables in searches for new physics are also presented. Event samples enriched in boosted W and Z bosons and top-quark pairs are used to study both the individual jet invariant mass scales and the efficacy of algorithms to tag boosted hadronic objects. The analyses presented use the full 2011 ATLAS dataset, corresponding to an integrated luminosity of 4.7 +/- 0.1 fb(-1) from proton-proton collisions produced by the Large Hadron Collider at a centre-of-mass energy of root s = 7 TeV.
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