Abstract
We study polarisation of W-bosons produced in association with one jet at the LHC. In particular, we provide all necessary theoretical ingredients for the precise extraction of polarisation fractions. To that end, we present new polarised predictions up to NNLO QCD accuracy employing the narrow-width approximation, in two phase spaces: inclusive and fiducial. We compare results in the fiducial phase space to a full off-shell computation as well as experimental data. Finally, we fit the polarisation fractions using shape templates and show that NNLO corrections significantly improve their determination.
Highlights
The LO is defined at order O α2αs, while the NLO and NNLO QCD corrections are defined at orders O α2αs2 and O α2αs3, respectively
To show how the result of the fit compares with our results from polarised cross section calculations, we present the error bar corresponding to polarisation fractions in table 2 and its theoretical uncertainty
One way of probing it is through the extraction of polarisation fractions, which are thought to be sensitive to potential new-physics effects
Summary
Are usually referred to as W + j production. In this study, given that we consider massless leptons, both cases = e, μ are equivalent. We will use the following notation for the cross sections and their perturbative expansions: σ(pp → ± ν(−) j) ≡ σ± = σ±(0) + σ±(1) + σ±(2) + O αs. We will use the following notation for the cross sections and their perturbative expansions: σ(pp → ± ν(−) j) ≡ σ± = σ±(0) + σ±(1) + σ±(2) + O αs4 We consider both the “plus” and “minus” signatures separately unless explicitly stated otherwise, so we will omit the ± superscript for brevity. The ‘transversely polarised’ amplitudes is represented by Λ = T = {+1, −1} and the ‘longitudinally polarised’ by Λ = L = {0} By squaring this amplitude, one obtains unpolarised cross sections. For estimating the scale uncertainty in the ratio, we use an uncorrelated estimation, that is we perform the squared error propagation of independent scale variations in both the numerator and denominator
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