During the 2010 CERN Large Hadron Collider operation at $\sqrt{s}$ = 7 TeV, 35 pb$^{-1}$ of high $p_T$ triggers has been collected by the ATLAS detector. This corresponds to the production of approximately $\number 2500$ top-quark pair events containing at least one lepton in the final state ($e$ or $μ$).
These proceedings present the first observation of single top-quark production associated with a photon using the full Run2 proton-proton dataset collected by the ATLAS experiment at the LHC.
New measurements from ATLAS at the LHC are presented on the total cross section at $\sqrt{s}=8$ TeV from elastic scattering using the ALFA sub-detector and on the inelastic cross section at $\sqrt{s}=13$ TeV using the MBTS sub-detector.
In this contribution, the results on soft hadron physics concerning the underlying event and Bose-Einsten correlations obtained using data collected in proton-proton collisions with the ATLAS experiment are presented.
Many theories beyond the Standard Model predict new phenomena which decay to well isolated, high-$p_{\text{T}}$ leptons. Searches for new physics with these signatures are performed using the ATLAS experiment at the LHC. The results reported here use the pp collision data sample collected by the ATLAS detector at the LHC with a center-of-mass energy of 13 TeV.
This report summarises studies of associated production of electroweak gauge bosons and jets in proton-proton collisions at LHC with center of mass energy of 8 and 13 TeV. It is based on a selection of results published by the ATLAS Collaboration in the first half of 2017.
This article presents a review of recent results on direct top quark mass measurements performed by the ATLAS and CMS collaborations on $pp$ collisions collected during Run 2 of the LHC at $\sqrt{s}=$13 TeV.
We report a measurement of the charge asymmetry $A_C$ in top quark pair production with the ATLAS experiment. The measurement focuses on dilepton channels ($ee$, $eμ$, $μμ$). The data are unfolded to parton level at full phase space using a fully Bayesian unfolding method. Inclusive and differential measurements of the charge asymmetry are performed.
The ATLAS detector at the LHC is equipped with dedicated systems designed for the detection of forward protons produced in diffractive and photon-induced processes. These detectors significantly extend the ATLAS physics reach. Recent measurements performed using these forward proton detectors: elastic proton-proton scattering, exclusive charged pion-pair production, and two-photon production of lepton pairs are presented.
Leptoquarks (LQ) are predicted by many new physics theories to describe the similarities between the lepton and quark sectors of the Standard Model and offer an attractive potential explanation for the lepton flavour anomalies observed at LHCb and flavour factories. The ATLAS experiment has a broad program of direct searches for Leptoquarks, coupling to the first-, second- or third-generation particles. The most recent 13 TeV results on the searches for Leptoquarks and contact interactions with the ATLAS detector are reviewed, covering flavour-diagonal and cross-generational final states.
We report a measurement of the charge asymmetry in top quark pair production with the ATLAS experiment at the LHC using 20.3 fb$^{-1}$ of pp collision data at $\sqrt{s}$ = 8 TeV. The data are unfolded using a fully Bayesian unfolding method. Differential measurements of the charge asymmetry are performed.
The luminosity determination for the ATLAS detector at the LHC during pp collisions at $\sqrt{s}$ = 8 TeV in 2012 is presented. The evaluation of the luminosity scale is performed using several luminometers, and comparisons between these luminosity detectors are made to assess the accuracy, consistency and long-term stability of the results. A luminosity uncertainty of dL/L = +/- 1.9% is obtained for the 22.7 fb$^{-1}$ of pp collision data delivered to ATLAS at $\sqrt{s}$ = 8 TeV in 2012.
The measurement of the inclusive $Wt$ cross-section at 13 TeV is performed using 3.2$\,\text{fb}{^{-1}}$ of proton--proton collision data collected by the ATLAS detector at the LHC in 2015. Events are required to have at least one jet and two opposite sign leptons. The cross section is measured to be $σ_{Wt} = 94\pm 10\text{(stat.)}^{+28}_{-22}\text{(syst.)}\pm 2\text{(lumi})$pb, corresponding to an observed significance of 4.5\,$σ$ (3.9\,$σ$ expected). The result is consistent with the Standard Model prediction.
Searches for high-mass resonances decaying to pairs of standard model bosons using ATLAS and CMS detectors are presented. The searches use 15 - 36 $\textrm{fb}^{-1}$ of proton-proton collision data collected at the centre-of-mass energy of 13 TeV at the LHC. Many different final states have been considered and the results are interpreted in a range of theories beyond the standard model of particle physics, most common being heavy vector triplet and warped extra dimensions.
Measurement of the inclusive and differential top-quark charge asymmetry is carried out using full Run 2 data from proton-proton collisions at a center-of-mass energy of $13$ TeV collected by the ATLAS detector. The single-lepton and dilepton $t\bar{t}$ decay channels are combined. Distorting detector effects are removed using fully Bayesian unfolding. In the dilepton decay channel, the leptonic charge asymmetry is determined. Results from the measurements are compared with the Standard Model prediction. The excess of charge asymmetry from zero charge-asymmetry hypothesis at the level of $4.7$…
The top-quark mass is one of the fundamental parameters of the Standard Model of particle physics. The latest ATLAS measurements of the top-quark mass in top quark pair final states are presented. Measurements use di-lepton, lepton+jets and all-jets final states and their combination is performed. Measurements of the top-quark pole mass based on precision theoretical QCD calculations for lepton kinematic distribution and for top quark pair production with an additional jet are also presented.
A review of the searches for the SM Higgs boson produced in association with a pair of top quarks, ${t\bar{t}H}$, using up to 13.3 fb$^{-1}$ of $pp$ collisions at $\sqrt{s}$ = 13 TeV collected with the ATLAS detector at the LHC is presented. Searches in the diphoton, multilepton and $b\bar{b}$ decay channels are summarised. The combination of these searches yields a measured (expected) significance for the observation of the ${t\bar{t}H}$ production process of $2.8 σ$ ($1.8 σ$).
A measurement of the material in the ATLAS inner detector using secondary hadronic interactions
ATLAS内部探测器用于重建初级碰撞产物强子相互作用的次级顶点，从而探测ATLAS内部区域的物质位置和数量。收集的数据在7 TeV pp碰撞在LHC，与最小的偏置触发，用于与模拟事件的比较。重建的次顶点的空间分辨率范围从~200微米到1毫米。模拟中的整体材料描述被验证在约7%的实验不确定度内。这将导致更好地理解各种物体的重建，如轨道，轻子，喷流和丢失的横向动量。
The ATLAS inner detector comprises three different sub-detectors: the pixel detector, the silicon strip tracker, and the transition-radiation drift-tube tracker. The Insertable $B$-Layer, a new innermost pixel layer, was installed during the shutdown period in 2014, together with modifications to the layout of the cables and support structures of the existing pixel detector. The material in the inner detector is studied with several methods, using a low-luminosity $\sqrt{s}=13$ TeV $pp$ collision sample corresponding to around $2.0\,\mathrm{nb}^{-1}$ collected in 2015 with the ATLAS experiment…
Non-ionizing energy loss causes bulk damage to the silicon sensors of the ATLAS pixel and strip detectors. This damage has important implications for data-taking operations, charged-particle track reconstruction, detector simulations, and physics analysis. This paper presents simulations and measurements of the leakage current in the ATLAS pixel detector and semiconductor tracker as a function of location in the detector and time, using data collected in Run 1 (2010-2012) and Run 2 (2015-2018) of the Large Hadron Collider. The extracted fluence shows a much stronger |z|-dependence in the inner…
