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 $\sqrt{s}=$ 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.
Highlights
Precision measurements of Standard Model processes at the Large Hadron Collider (LHC) are crucial for probing the fundamental structure of the strong and electroweak interactions
The data sample corresponding to an integrated luminosity of 20.3 fb−1 collected by the ATLAS experiment√from proton–proton collisions at a centre-of-mass energy s = 8 TeV at the LHC allows detailed study of perturbative quantum chromodynamics and real and virtual electroweak (EW) corrections that impact measurements of W + jets production
The muon with the higher pT is chosen to define R. Using data from these control regions and the signal region, a scale factor is derived for each main background process and the W + jets signal to correct the normalisation of the Monte Carlo (MC) sample to that observed in data
Summary
Precision measurements of Standard Model processes at the Large Hadron Collider (LHC) are crucial for probing the fundamental structure of the strong and electroweak interactions. The measurements presented here focus on events that contain a muon and a jet with transverse momentum pT > 500 GeV In this kinematic regime, contributions to W + jets processes from real W boson emission are enhanced in the region of small angular separation between the W boson decay products and the closest jet. The ATLAS Collaboration / Physics Letters B 765 (2017) 132–153 muon and the closest jet, R(μ, jet) = ( φ)2 + ( η) hereafter referred to as R Measurements of this angular separation provide precision tests of pQCD and electroweak predictions for the rate and pattern of real W boson emission. The result is that W emission from quarks at very high pT can yield single jets with definite substructure that resemble the boosted top-quark signals being searched for
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