Abstract
The inclusive cross-section for the associated production of a W boson and top quark is measured using data from proton-proton collisions at sqrt{s}=13 TeV. The dataset corresponds to an integrated luminosity of 3.2 fb−1, and was collected in 2015 by the ATLAS detector at the Large Hadron Collider at CERN. Events are selected requiring two opposite sign isolated leptons and at least one jet; they are separated into signal and control regions based on their jet multiplicity and the number of jets that are identified as containing b hadrons. The W t signal is then separated from the toverline{t} background using boosted decision tree discriminants in two regions. The cross-section is extracted by fitting templates to the data distributions, and is measured to be σW t = 94 ± 10(stat.)− 22+ 28(syst.) ± 2(lumi.) pb. The measured value is in good agreement with the SM prediction of σtheory = 71.7±1.8 (scale)± 3.4 (PDF) pb [1].
Highlights
The ATLAS detectorThe ATLAS detector [15] at the LHC covers nearly the entire solid angle around the collision point, and consists of an inner tracking detector (ID) surrounded by a thin superconducting solenoid magnet producing a 2 T axial magnetic field, electromagnetic (EM) and hadronic calorimeters, and an external muon spectrometer (MS)
(b) the W t channel only depends on the latter; it is important to study this channel separately to provide a comparison with the other channels [7, 8]
The measured value is in good agreement with the SM prediction of σtheory = 71.7±1.8± 3.4 (PDF) pb [1]
Summary
The ATLAS detector [15] at the LHC covers nearly the entire solid angle around the collision point, and consists of an inner tracking detector (ID) surrounded by a thin superconducting solenoid magnet producing a 2 T axial magnetic field, electromagnetic (EM) and hadronic calorimeters, and an external muon spectrometer (MS). The ID consists of a high-granularity silicon pixel detector and a silicon microstrip tracker, together providing precision tracking in the pseudorapidity range |η| < 2.5, complemented by a transition radiation tracker providing tracking and electron identification information for |η| < 2.0. A lead liquid-argon (LAr) electromagnetic calorimeter covers the region |η| < 3.2, and hadronic calorimetry is provided by steel/scintillator tile calorimeters within |η| < 1.7 and copper/LAr hadronic endcap calorimeters in the range 1.5 < |η| < 3.2. The MS consists of precision tracking chambers covering the region |η| < 2.7, and separate trigger chambers covering |η| < 2.4. A two-level trigger system, using a custom hardware level followed by a software-based level, selects from the 40 MHz of collisions a maximum of around 1 kHz of interesting events for offline storage
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