| 1. |
- Aad, G, et al.
(författare)
-
- 2014
-
Ingår i: Physical Review Letters. - 1079-7114 .- 0031-9007. ; 113:17
-
Tidskriftsartikel (refereegranskat)
|
|
| 2. |
- Abulaiti, Yiming, et al.
(författare)
-
Technical Design Report for the Phase-II Upgrade of the ATLAS Tile Calorimeter
- 2018
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This Technical Design Report describes the project to upgrade the ATLAS Tile Calorimeter for the operation at the High Luminosity LHC. The High Luminosity LHC is planned to begin operation in 2026 and to deliver more than ten times the integrated luminosity (up to 4000 fb"^{-1}" of the LHC Runs 1-3 combined. To achieve this integrated luminosity in a reasonable amount of time, an instantaneous luminosity of up to "7.5\times 10^{34} cm^{-2}s^{-1}" is required, corresponding to up to 200 simultaneous pp interactions per bunch crossing. The large luminosity offers the opportunity for a wealth of physics measurements but presents significant challenges to the detector as well as to the trigger and data acquisition systems in the form of increased trigger rates and detector occupancy. This document summarises the requirements and motivations for the Tile Calorimeter upgrade and gives a detailed technical description of the different components. It describes the beam tests with the prototypes in recent years and the plans for the assembly, quality assurance and the integration of the final system. The document also presents the key aspects of project management with an overview of the organisation, the schedule and the cost.
|
|
| 3. |
- Molander, Simon, 1980-
(författare)
-
Studies of Top Physics Sensitivity and of Pile-Up Effects on Energy Reconstruction in the ATLAS Detector : A Licentiate Thesis About the Treatment of Troublesome $\tau$ and Producing Pulses to Probe Pile-up Problems
- 2016
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis presents two studies conducted using the ATLAS detectorat the Large Hadron Collider. The first one is a technical study abouthow out-of-time pile-up affects energy reconstruction using the optimalfiltering 2 algorithm in the TILE calorimeter sub detector. The studyis conducted using a pulse simulator software that is also described.Although the algorithm is potentially sensitive to the effects ofout-of-time pile-up, the effects under actual running conditions areestimated to be lower than 1.5 ADC counts for 68 \% of the pulses,which is considered a small effect. It is also shown that out-of-timepile-up is a potential reason to get negatively reconstructed energies.The second study regards a measurement of the $t\bar{tZ}$ cross sectionwith one hadronically decaying $\tau$ leptons and two lighter leptonsin the final state using 8 TeV data. The conclusion is that it isnot possible to make a significant such measurement from the 8 TeVdata due to low efficiencies in reconstruction of $\tau$ leptons.In addition to these two studies, this thesis also contain brief overviewsof the atlas detector and the standard model of particles and interactions.
|
|
| 4. |
- Milstead, David A., et al.
(författare)
-
Study of the material of the ATLAS inner detector for Run 2 of the LHC
- 2017
-
Ingår i: Journal of Instrumentation. - : Institute of Physics (IOP). - 1748-0221. ; 12:12
-
Tidskriftsartikel (refereegranskat)abstract
- 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 s=13 TeV pp collision sample corresponding to around 2.0 nb-1 collected in 2015 with the ATLAS experiment at the LHC. In this paper, the material within the innermost barrel region is studied using reconstructed hadronic interaction and photon conversion vertices. For the forward rapidity region, the material is probed by a measurement of the efficiency with which single tracks reconstructed from pixel detector hits alone can be extended with hits on the track in the strip layers. The results of these studies have been taken into account in an improved description of the material in the ATLAS inner detector simulation, resulting in a reduction in the uncertainties associated with the charged-particle reconstruction efficiency determined from simulation. © 2017 CERN.
|
|
| 5. |
|
|
| 6. |
- Aad, G., et al.
(författare)
-
Identification and energy calibration of hadronically decaying tau leptons with the ATLAS experiment in pp collisions at root s=8 TeV
- 2015
-
Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 75:7
-
Tidskriftsartikel (refereegranskat)abstract
- This paper describes the trigger and offline reconstruction, identification and energy calibration algorithms for hadronic decays of tau leptons employed for the data collected from pp collisions in 2012 with the ATLAS detector at the LHC center-of-mass energy root s = 8 TeV. The performance of these algorithms is measured in most cases with Z decays to tau leptons using the full 2012 dataset, corresponding to an integrated luminosity of 20.3 fb(-1). An uncertainty on the offline reconstructed tau energy scale of 2-4%, depending on transverse energy and pseudorapidity, is achieved using two independent methods. The offline tau identification efficiency is measured with a precision of 2.5% for hadronically decaying tau leptons with one associated track, and of 4% for the case of three associated tracks, inclusive in pseudorapidity and for a visible transverse energy greater than 20 GeV. For hadronic tau lepton decays selected by offline algorithms, the tau trigger identification efficiency is measured with a precision of 2-8%, depending on the transverse energy. The performance of the tau algorithms, both offline and at the trigger level, is found to be stable with respect to the number of concurrent proton-proton interactions and has supported a variety of physics results using hadronically decaying tau leptons at ATLAS.
|
|
| 7. |
|
|
| 8. |
|
|
| 9. |
- Abulaiti, Yiming, et al.
(författare)
-
Fiducial, total and differential cross-section measurements of t-channel single top-quark production in pp collisions at 8TeV using data collected by the ATLAS detector
- 2017
-
Ingår i: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 77:8
-
Tidskriftsartikel (refereegranskat)abstract
- Detailed measurements of t-channel single top-quark production are presented. They use 20.2 fb(-1) of data collected by the ATLAS experiment in proton-proton collisions at a centre-of-mass energy of 8 TeV at the LHC. Total, fiducial and differential cross-sections are measured for both top-quark and top-antiquark production. The fiducial cross-section is measured with a precision of 5.8% (top quark) and 7.8% (top antiquark), respectively. The total cross-sections are measured to be stot(tq) = 56.7(-3.8)(+4.3) pb for top-quark production and sigma(tot)((t) over barq) = 32.9(-2.7)(+3.0) pb for top-antiquark production, in agreement with the Standard Model prediction. In addition, the ratio of top-quark to top-antiquark production cross-sections is determined to be R-t = 1.72 +/- 0.09. The differential cross-sections as a function of the transverse momentum and rapidity of both the top quark and the top antiquark are measured at both the parton and particle levels. The transverse momentum and rapidity differential cross-sections of the accompanying jet from the t-channel scattering are measured at particle level. All measurements are compared to various Monte Carlo predictions as well as to fixed-order QCD calculations where available.
|
|
| 10. |
- Abulaiti, Yiming, et al.
(författare)
-
Search for direct top squark pair production in events with a Higgs or Z boson, and missing transverse momentum in root s=13 TeV pp collisions with the ATLAS detector
- 2017
-
Ingår i: Journal of High Energy Physics (JHEP). - : Springer. - 1126-6708 .- 1029-8479. ; :8
-
Tidskriftsartikel (refereegranskat)abstract
- A search for direct top squark pair production resulting in events with either a same-flavour opposite-sign dilepton pair with invariant mass compatible with a Z boson or a pair of jets compatible with a Standard Model (SM) Higgs boson (h) is presented. Requirements on the missing transverse momentum, together with additional selections on leptons, jets, jets identified as originating from b-quarks are imposed to target the other decay products of the top squark pair. The analysis is performed using proton-proton collision data at root s = 13 TeV collected with the ATLAS detector at the LHC in 20152016, corresponding to an integrated luminosity of 36.1 fb(-1). No excess is observed in the data with respect to the SM predictions. The results are interpreted in two sets of models. In the first set, direct production of pairs of lighter top squarks ((t) over tilde (1)) with long decay chains involving Z or Higgs bosons is considered. The second set includes direct pair production of the heavier top squark pairs ((t) over tilde (2)) decaying via (t) over tilde (2) -> Z (t) over tilde (1) or (t) over tilde (2) -> h (t) over tilde (1). The results exclude at 95% confidence level (t) over tilde (2) and (t) over tilde (1) masses up to about 800 GeV, extending the exclusion region of supersymmetric parameter space covered by previous LHC searches.
|
|
