ATLAS Collaboration(Aad, G. et al), Alvarez Piqueras, D., Barranco Navarro, L., Cabrera Urban, S., Castillo Gimenez, V., Cerda Alberich, L., et al. (2016). Muon reconstruction performance of the ATLAS detector in proton-proton collision data at root s=13 TeV. Eur. Phys. J. C, 76(5), 292–30pp.
Abstract: This article documents the performance of the ATLAS muon identification and reconstruction using the LHC dataset recorded at root s = 13 TeVin 2015. Using a large sample of J/.psi -> μμand Z -> μμdecays from 3.2 fb(-1) of pp collision data, measurements of the reconstruction efficiency, as well as of the momentum scale and resolution, are presented and compared to Monte Carlo simulations. The reconstruction efficiency is measured to be close to 99 % over most of the covered phase space (vertical bar eta vertical bar < 2.5 and 5 < p(T) < 100 GeV). The isolation efficiency varies between 93 and 100 % depending on the selection applied and on the momentum of the muon. Both efficiencies are well reproduced in simulation. In the central region of the detector, the momentum resolution is measured to be 1.7 % (2.3 %) for muons from J/psi -> μmu(Z -> μmu) decays, and the momentum scale is known with an uncertainty of 0.05 %. In the region vertical bar eta vertical bar > 2.2, the p(T) resolution for muons from Z -> μdecays is 2.9 % while the precision of the momentum scale for low-p(T) muons from J/psi -> μμdecays is about 0.2 %.
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ATLAS Collaboration(Aad, G. et al), Aparisi Pozo, J. A., Bailey, A. J., Cabrera Urban, S., Cardillo, F., Castillo, F. L., et al. (2021). Muon reconstruction and identification efficiency in ATLAS using the full Run 2 pp collision data set at root s = 13 TeV. Eur. Phys. J. C, 81(7), 578–44pp.
Abstract: This article documents the muon reconstruction and identification efficiency obtained by the ATLAS experiment for 139 fb-1 of pp collision data at <mml:msqrt>s</mml:msqrt>=13 TeV collected between 2015 and 2018 during Run 2 of the LHC. The increased instantaneous luminosity delivered by the LHC over this period required a reoptimisation of the criteria for the identification of prompt muons. Improved and newly developed algorithms were deployed to preserve high muon identification efficiency with a low misidentification rate and good momentum resolution. The availability of large samples of Z -> μμand J/psi -> μμdecays, and the minimisation of systematic uncertainties, allows the efficiencies of criteria for muon identification, primary vertex association, and isolation to be measured with an accuracy at the per-mille level in the bulk of the phase space, and up to the percent level in complex kinematic configurations. Excellent performance is achieved over a range of transverse momenta from 3 GeV to several hundred GeV, and across the full muon detector acceptance of |eta|<2.7.
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ATLAS Collaboration(Aad, G. et al), Aparisi Pozo, J. A., Bailey, A. J., Cabrera Urban, S., Cardillo, F., Castillo, F. L., et al. (2021). Medium-Induced Modification of Z-Tagged Charged Particle Yields in Pb plus Pb Collisions at 5.02 TeV with the ATLAS Detector. Phys. Rev. Lett., 126(7), 072301–20pp.
Abstract: The yield of charged particles opposite to a Z boson with large transverse momentum (p(T)) is measured in 260 pb(-1) of pp and 1.7 nb(-1) of Pb + Pb collision data at 5.02 TeV per nucleon pair recorded with the ATLAS detector at the Large Hadron Collider. The Z boson tag is used to select hard-scattered partons with specific kinematics, and to observe how their showers are modified as they propagate through the quarkgluon plasma created in Pb + Pb collisions. Compared with pp collisions, charged-particle yields in Pb + Pb collisions show significant modifications as a function of charged-particle p(T) in a way that depends on event centrality and Z boson p(T). The data are compared with a variety of theoretical calculations and provide new information about the medium-induced energy loss of partons in a p(T) regime difficult to measure through other channels.
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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 W boson angular distributions in events with high transverse momentum jets at root s=8 TeV using the ATLAS detector. Phys. Lett. B, 765, 132–153.
Abstract: The W boson angular distribution in events with high transverse momentum jets is measured using data collected by the ATLAS experiment from proton-proton collisions at a centre-of-mass energy root s = 8 TeV at the Large Hadron Collider, corresponding to an integrated luminosity of 20.3 fb(-1). The focus is on the contributions to W + jets processes from real W emission, which is achieved by studying events where a muon is observed close to a high transverse momentum jet. At small angular separations, these contributions are expected to be large. Various theoretical models of this process are compared to the data in terms of the absolute cross-section and the angular distributions of the muon from the leptonic W decay.
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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). Performance of the ATLAS Transition Radiation Tracker in Run 1 of the LHC: tracker properties. J. Instrum., 12, P05002–42pp.
Abstract: The tracking performance parameters of the ATLAS Transition Radiation Tracker (TRT) as part of the ATLAS inner detector are described in this paper for different data-taking conditions in proton-proton, proton-lead and lead-lead collisions at the Large Hadron Collider (LHC). The performance is studied using data collected during the first period of LHC operation (Run 1) and is compared with Monte Carlo simulations. The performance of the TRT, operating with two different gas mixtures (xenon-based and argon-based) and its dependence on the TRT occupancy is presented. These studies show that the tracking performance of the TRT is similar for the two gas mixtures and that a significant contribution to the particle momentum resolution is made by the TRT up to high particle densities.
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