ATLAS Collaboration(Aad, G. et al), Amos, K. R., Aparisi Pozo, J. A., Bailey, A. J., Bouchhar, N., Cabrera Urban, S., et al. (2023). Studies of the muon momentum calibration and performance of the ATLAS detector with pp collisions at √s=13 TeV. Eur. Phys. J. C, 83(8), 686–37pp.
Abstract: This paper presents the muon momentum calibration and performance studies for the ATLAS detector based on the pp collisions data sample produced at root s = 13 TeV at the LHC during Run 2 and corresponding to an integrated luminosity of 139 fb(-1). An innovative approach is used to correct for potential charge-dependent momentum biases related to the knowledge of the detector geometry, using the Z ->mu(+)mu(-) resonance. The muon momentum scale and resolution are measured using samples of J/psi ->mu(+)mu(-) and Z ->mu(+)mu(-) events. A calibration procedure is defined and applied to simulated data to match the performance measured in real data. The calibration is validated using an independent sample of Upsilon ->mu(+)mu(-) events. At the Z(J/psi) peak, the momentum scale is measured with an uncertainty at the 0.05% (0.1%) level, and the resolution is measured with an uncertainty at the 1.5% (2%) level. The charge-dependent bias is removed with a dedicated in situ correction for momenta up to 450 GeV with a precision better than 0.03 TeV-1.
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ATLAS Collaboration(Aaboud, M. et al), Alvarez Piqueras, D., Barranco Navarro, L., Cabrera Urban, S., Castillo Gimenez, V., Cerda Alberich, L., et al. (2017). Reconstruction of primary vertices at the ATLAS experiment in Run 1 proton-proton collisions at the LHC. Eur. Phys. J. C, 77(5), 332–35pp.
Abstract: This paper presents the method and performance of primary vertex reconstruction in proton-proton collision data recorded by the ATLAS experiment during Run 1 of the LHC. The studies presented focus on data taken during 2012 at a centre-of-mass energy of root s = 8 TeV. The performance has been measured as a function of the number of interactions per bunch crossing over a wide range, from one to seventy. The measurement of the position and size of the luminous region and its use as a constraint to improve the primary vertex resolution are discussed. A longitudinal vertex position resolution of about 30 μm is achieved for events with high multiplicity of reconstructed tracks. The transverse position resolution is better than 20 μm and is dominated by the precision on the size of the luminous region. An analytical model is proposed to describe the primary vertex reconstruction efficiency as a function of the number of interactions per bunch crossing and of the longitudinal size of the luminous region. Agreement between the data and the predictions of this model is better than 3% up to seventy interactions per bunch crossing.
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ATLAS Collaboration(Aaboud, M. et al), Alvarez Piqueras, D., Barranco Navarro, L., Cabrera Urban, S., Castillo Gimenez, V., Cerda Alberich, L., et al. (2016). Measurement of the relative width difference of the B-0-(B)over-bar(0) system with the ATLAS detector. J. High Energy Phys., 06(6), 081–39pp.
Abstract: This paper presents the measurement of the relative width difference Delta Gamma(d)/Gamma(d) of the B-0-(B) over bar (0) system using the data collected by the Lambda TLAS experiment at the LHC in pp collisions at root s = 7 TeV and root s= 8 TeV and corresponding to an integrated luminosity of 25.2 fb(-1). The value of Delta Gamma(d)/Gamma(d) is obtained by comparing the decay-time distributions of B-0 -> J/Psi K-S and (B) over bar (0) -> J/Psi K*(0)(892) decays. The result is Delta Gamma(d)/Gamma(d) = (-0.1 +/- 1.1 (stat.) +/- 0.9 (syst.)) x 10(-2). Currently, this is the most precise single measurement of AFd/Fd. It agrees with the Standard Model prediction and the measurements by other experiments.
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ATLAS Collaboration(Aaboud, M. et al), Alvarez Piqueras, D., Barranco Navarro, L., Cabrera Urban, S., Castillo Gimenez, V., Cerda Alberich, L., et al. (2017). Measurement of (WW +/-)-W-+/- vector-boson scattering and limits on anomalous quartic gauge couplings with the ATLAS detector. Phys. Rev. D, 96(1), 012007–34pp.
Abstract: This paper presents the extended results of measurements of (WW +/-)-W-+/- jj production and limits on anomalous quartic gauge couplings using 20.3 fb(-1) of proton-proton collision data at root s = 8 TeV recorded by the ATLAS detector at the Large Hadron Collider. Events with two leptons (e or mu) with the same electric charge and at least two jets are analyzed. Production cross sections are determined in two fiducial regions, with different sensitivities to the electroweak and strong production mechanisms. An additional fiducial region, particularly sensitive to anomalous quartic gauge coupling parameters alpha 4 and alpha 5, is introduced, which allows more stringent limits on these parameters compared to the previous ATLAS measurement.
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ATLAS Collaboration(Aaboud, M. et al), Alvarez Piqueras, D., Aparisi Pozo, J. A., Bailey, A. J., Barranco Navarro, L., Cabrera Urban, S., et al. (2019). Electron and photon energy calibration with the ATLAS detector using 2015-2016 LHC proton-proton collision data. J. Instrum., 14, P03017–60pp.
Abstract: This paper presents the electron and photon energy calibration obtained with the ATLAS detector using about 36 fb(-1) of LHC proton-proton collision data recorded at root s = 13 TeV in 2015 and 2016. The different calibration steps applied to the data and the optimization of the reconstruction of electron and photon energies are discussed. The absolute energy scale is set using a large sample of Z boson decays into electron-positron pairs. The systematic uncertainty in the energy scale calibration varies between 0.03% to 0.2% in most of the detector acceptance for electrons with transverse momentum close to 45 GeV. For electrons with transverse momentum of 10 GeV the typical uncertainty is 0.3% to 0.8% and it varies between 0.25% and 1% for photons with transverse momentum around 60 GeV. Validations of the energy calibration with J/psi -> e(+)e(-) decays and radiative Z boson decays are also presented.
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