Large Hadron Collider momentum calibration and accuracy

Todesco, E.; Wenninger, J.

doi:10.1103/physrevaccelbeams.20.081003

Cited by 33 publications

(32 citation statements)

References 15 publications

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“…Only events recorded with stable beams and the detector operating well are selected. The relative uncertainty of the LHC proton beam energy of ±0.1% [23] has no significant effect on the results.Events from Monte Carlo (MC) simulations, including simulation of the ATLAS detector, are used for the background estimation and to correct the measured data for detector acceptance, efficiency, and resolution effects.The W → µν signal process was simulated using Powheg-Box [24,25] at next-to-leading order (NLO) in perturbative QCD using the CT10 set of PDFs [26] and interfaced to Pythia 8.170 [27] with the AU2 set of tuned parameters [28] to simulate the parton shower, hadronisation, and underlying event and to Photos [29] to simulate final-state photon radiation (FSR). This is referred to as Powheg+Pythia8 in this paper.…”

mentioning

confidence: 86%

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

Aad

Abbott

et al. 2019

Eur. Phys. J. C

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Measurement of the cross-section and charge asymmetry of W bosons produced in proton-proton collisions at √ s = 8 TeV with the ATLAS detectorThe ATLAS Collaboration This paper presents measurements of the W + → µ + ν and W − → µ − ν 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 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.1 ATLAS uses a right-handed coordinate system with its origin at the nominal interaction point in the centre of the detector and the z-axis coinciding with the axis of the beam pipe. The x-axis points from the interaction point to the centre of the LHC ring, and the y-axis points upward. Polar coordinates (r, φ) are used in the transverse plane, φ being the azimuthal angle around the beam pipe. The pseudorapidity is defined in terms of the polar angle θ as η = − ln tan(θ/2). The rapidity y of a system is defined in terms of its energy E and its longitudinal momentum p z as y = (1/2) ln[(E + p z )/(E − p z )]. Angular separations between particles or reconstructed objects are measured in η-φ space using ∆R = (∆η) 2 + (∆φ) 2 . The ATLAS detectorThe ATLAS detector [20] at the LHC covers nearly the entire solid angle around the collision point. It consists of an inner tracking detector (ID) surrounded by a thin superconducting solenoid, electromagnetic and hadronic calorimeters, and a muon spectrometer (MS) incorporating three large superconducting toroid magnets. The ID is immersed in a 2 T axial magnetic field and provides charged-particle tracking in the range |η| < 2.5. A high-granularity silicon pixel detector typically provides three measurements per track and is followed by a silicon microstrip tracker, which usually provides four three-dimensional measurement points per track. These silicon detectors are complemented by a transition radiation tracker, which enables radially extended track reconstruction up to |η| = 2.0.The calorimeter system covers the pseudorapidity range |η| < 4.9. Electromagnetic calorimetry is provided by barrel and endcap high-granularity lead/liquid-argon (LAr) sampling calorimeters in the |η| < 3.2 region. A thin LAr presampler, covering |η| < 1.8, corrects for energy loss in the material upstream of the calorimeters. Hadronic calorimetry is provided in the |η| < 1.7 region by the steel/scintillator tile calorimeter, segmented into three barrel structures, and in the endcap region by two copper/LAr calorimeters. The forward ...

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confidence: 86%

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

Aad

Abbott

et al. 2019

Eur. Phys. J. C

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“…Beam energy: The LHC beam energy during the 2012 pp run was determined to be within 0.1 % of the nominal value of 4 TeV per beam, based on the LHC magnetic model together with measurements of the revolution frequency difference of proton and lead-ion beams [91]. Following the approach used in Ref.…”

Section: Luminosity and Beam Energymentioning

confidence: 99%

Measurement of lepton differential distributions and the top quark mass in $$t\bar{t}$$ t t ¯

Aaboud¹,

Aad²,

Abbott³

et al. 2017

Eur. Phys. J. C

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This paper presents single lepton and dilepton kinematic distributions measured in dileptonic tt events produced in 20.2 fb −1 of √ s = 8 TeV pp collisions recorded by the ATLAS experiment at the LHC. Both absolute and normalised differential cross-sections are measured, using events with an opposite-charge eμ pair and one or two btagged jets. The cross-sections are measured in a fiducial region corresponding to the detector acceptance for leptons, and are compared to the predictions from a variety of Monte Carlo event generators, as well as fixed-order QCD calculations, exploring the sensitivity of the cross-sections to the gluon parton distribution function. Some of the distributions are also sensitive to the top quark pole mass; a combined fit of NLO fixed-order predictions to all the measured distributions yields a top quark mass value of m pole t = 173.2 ± 0.9 ± 0.8 ± 1.2 GeV, where the three uncertainties arise from data statistics, experimental systematics, and theoretical

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“…The systematic uncertainties in the theoretical tt cross section are associated with the choice of the renormalization (µ R ) and factorization (µ F ) scales-nominally set at µ R = µ F = √ m 2 top + p 2 T,top with p T,top the top quark transverse momentum-as well as with the PDF set and the α s value. The uncertainty of 0.1% in the LHC beam energy [35] translates into an additional uncertainty of 0.22 pb in the expected cross section, with negligible impact on the acceptance of any of the channels included in this analysis.…”

Section: Introductionmentioning

confidence: 99%

Measurement of the inclusive $$ \mathrm{t}\overline{\mathrm{t}} $$ cross section in pp collisions at $$ \sqrt{s}=5.02 $$ TeV using final states with at least one charged lepton

Sirunyan¹,

Tumasyan²,

Adam³

et al. 2018

J. High Energ. Phys.

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Measurement of the inclusive tt cross section in pp collisions at √ s = 5.02 TeV using final states with at least one charged leptonThe CMS Collaboration * AbstractThe top quark pair production cross section (σ tt ) is measured for the first time in pp collisions at a center-of-mass energy of 5.02 TeV. The data were collected by the CMS experiment at the LHC and correspond to an integrated luminosity of 27.4 pb −1 . The measurement is performed by analyzing events with at least one charged lepton. The measured cross section is σ tt = 69.5 ± 6.1 (stat) ± 5.6 (syst) ± 1.6 (lumi) pb, with a total relative uncertainty of 12%. The result is in agreement with the expectation from the standard model. The impact of the presented measurement on the determination of the gluon distribution function is investigated.This analysis represents the first measurement of σ tt in pp collisions at √ s = 5.02 TeV using tt candidate events with +jets, where leptons are either electrons ( = e) or muons ( = µ), and dilepton (e ± µ ∓ or µ ± µ ∓ ) final states. In the former case, σ tt is extracted by a fit to the distribution of a kinematic variable for different categories of lepton flavor and jet multiplicity, while in the latter an event counting approach is used. The two results are then combined in the final measurement, which is used as input to a quantum chromodynamics (QCD) analysis at next-to-next-to-leading order (NNLO) to investigate the impact on the determination of the gluon distribution in the less-explored kinematic range of x 0.1. This paper is structured as follows. Section 2 describes the CMS detector. Section 3 gives a summary of the data and simulated samples used. After the discussion of the object reconstruction in Section 4, and of the trigger and event selection in Section 5, Section 6 describes the determination of the background sources. The systematic uncertainties are discussed in Section 7. The extraction of σ tt is presented in Section 8 and the impact of the presented measurement on the determination of the proton PDFs is discussed in Section 9. A summary of all the results is given in Section 10. The CMS detectorThe central feature of the CMS apparatus is a superconducting solenoid of 6 m internal diameter, providing a magnetic field of 3.8 T parallel to the beam direction.Within the solenoid volume are a silicon pixel and strip tracker, a lead tungstate crystal electromagnetic calorimeter (ECAL), and a brass and scintillator hadron calorimeter (HCAL), each composed of a barrel and two endcap sections. A preshower detector, consisting of two planes of silicon sensors interleaved with about 3 radiation lengths of lead, is located in front of the endcap regions of ECAL. Hadron forward calorimeters using steel as an absorber and quartz fibers as the sensitive material extend the pseudorapidity coverage provided by the barrel and endcap detectors from |η| = 3.0 to 5.2.Charged particle trajectories with |η| < 2.5 are measured by the tracker system, while the energy deposits in ECAL and HCAL cells are summed to ...

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Large Hadron Collider momentum calibration and accuracy

Cited by 33 publications

References 15 publications

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

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

Measurement of lepton differential distributions and the top quark mass in $$t\bar{t}$$ t t ¯

Measurement of the inclusive $$ \mathrm{t}\overline{\mathrm{t}} $$ cross section in pp collisions at $$ \sqrt{s}=5.02 $$ TeV using final states with at least one charged lepton

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