Abstract
We present details of the calculation of the pp → W(→ lν)γ process at next-to-next-to-leading order in QCD, calculated using the jettiness slicing method. The calculation is based entirely on analytic amplitudes. Because of the radiation zero, the NLO QCD contribution from the gq channel is as important as the contribution from the Born qoverline{q} process, disrupting the normal counting of leading and sub-leading contributions. We also assess the importance of electroweak (EW) corrections, including the EW corrections to both the six-parton channel 0 → overline{u} dnu {e}^{+}gamma g and the five-parton channel 0 → overline{u} dnu {e}^{+}gamma . Previous experimental results have been shown to agree with theoretical predictions, taking into account the large experimental errors. With the advent of run II data from the LHC, the statistical errors on the data will decrease, and will be competitive with the error on theoretical predictions for the first time. We present numerical results for sqrt{s} = 7 and 13 TeV. Analytic results for the one-loop six-parton QCD amplitude and the tree-level seven-parton QCD amplitude are presented in appendices.
Highlights
The process pp → W (→ lν) + γ occupies a special place amongst the high-energy processes sensitive to triple coupling of three vector bosons
More recently NLO W γ production in hadronic collisions has been interfaced to a shower generator according to the POWHEG prescription in such a way that the contribution arising from hadron fragmentation into photons is fully modelled [11]
The results presented in this paper are similar in spirit, but different in detail from the results of refs. [14, 18]: 1. Instead of the qT slicing method, we use the N -jettiness slicing method, which has been successfully implemented in MCFM for the following processes, pp → H + X, pp → W ±, pp → Z, pp → W H, pp → ZH, pp → γγ [19], pp → Zγ [20], pp → Z+ jet [21], pp → H+ jet [22]
Summary
The process pp → W (→ lν) + γ occupies a special place amongst the high-energy processes sensitive to triple coupling of three vector bosons. 2. All amplitudes and matrix elements entering our NNLO QCD calculation are implemented using analytic formulae. All amplitudes and matrix elements entering our NNLO QCD calculation are implemented using analytic formulae We believe this will have benefits for both the stability and speed of the code. The first complete one-loop analytic result for this process is presented in an appendix to this paper. Part of this result is derivable from ref. Indicated are the predictions for the theoretical cross sections, presented in the papers cited by the experimental collaborations. For the most part the experimental results are fiducial cross sections for the process pp → ±νγ or pp → ±νγ with differing cuts, and as such they are not directly comparable, even at the same energy. Definitions of spinor products and analytic results for the 6- and 7-parton QCD processes are provided in the appendices
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