NNLO QCD corrections tot-channel single top quark production and decay

Abstract

We present a fully differential next-to-next-to-leading order calculation of t-channel single top-quark production and decay at the LHC under narrow-width approximation and neglecting cross-talk between incoming protons. We focus on the fiducial cross sections at 13 TeV, finding that the next-to-next-to-leading order QCD corrections can reach the level of −6%. The scale variations are reduced to the level of a percent. Our results can be used to improve experimental acceptance estimates and the measurements of the single top-quark production cross section and the top-quark electroweak couplings.Introduction. The top quark can be produced singly at a hadron collider through the electroweak (EW) W tb vertex. There are three production channels: the t-channel and s-channel processes through exchange of a W boson, and associated production of tW . All three channels are sensitive to the structure of the W tb vertex and to the CKM matrix element V tb , an important motivation for their study. Moreover, single top production provides an important window to physics beyond the standard model (SM) [1], e.g., a modified W tb vertex, new heavy quarks, new gauge bosons, flavor-changing neutral current, and so forth. Single top-quark production was first established at the Fermilab Tevatron [2,3], and later at the Large Hadron Collider (LHC) [4][5][6][7]. Single top-quark studies are expected to enter an era of high precision during the upcoming run of the LHC at higher energy and larger luminosity.The t-channel production has the largest rate among the three at the LHC, about 210 pb at √ s = 13 TeV. Significant efforts to improve the theoretical description of this process include next-to-leading order (NLO) QCD corrections in both 4-and 5-flavor schemes in Refs. [8][9][10][11][12][13][14][15][16]. Soft gluon resummation has been considered in Refs. [17][18][19][20]. Matching NLO calculations to parton showers is done in Refs. [21][22][23]. Recently, next-to-nextto-leading order (NNLO) QCD corrections with a stable top quark were calculated in Ref. [24], neglecting certain subleading contributions in color.In this manuscript we present the first fully differential NNLO calculation of t-channel single top quark production and decay at the LHC in the 5-flavor scheme in QCD. We follow Ref. [24] in neglecting cross-talk between the hadronic systems of the two incoming protons. To the best of our knowledge, our calculation is the first to combine QCD corrections at NNLO for production and decay, meaning that a realistic simulation at NNLO is now

The gluon-fusion production of Higgs boson pair: N3LO QCD corrections and top-quark mass effects

“…is computed with the aid of the transverse-momentum resummation formalism in SCET. The cross section of this part is factorised as a convolution 1 With qT -subtraction method, tremendous works have been done at the NNLO accuracy [46,[68][69][70][71][72][73][74][75][76][77][78][79][80][81][82][83][84][85][86].…”

Heavy-flavor parton distributions without heavy-flavor matching prescriptions

“…The 5FS NNLO corrections to the t-channel single top cross-section are not computed from first principles but are obtained by rescaling the NLO 5FS results with an NNLO K-factor derived from the results of refs. [62,63]. Specifically, the proxy to the NNLO t-channel single-top cross-section in the 5FS is…”

“…[63] (i.e. for κ = 1) and σ NLO (NNLO pdf, κ) is calculated exactly, using the relevant pdf set with κ ≥ 1.…”

“…For this reason we have not extended the NNLO curves for scales outside the µ F range considered in refs. [62,63], which is sufficient for our goals. The 5FS cross-section for bbZ has been calculated at NNLO by using a private code [64], which has been cross-checked at LO and NLO against MadGraph5 aMC@NLO.…”

Precise predictions for single-top production: the impact of EW corrections and QCD shower on the t-channel signature

“…On the theoretical front, predictions for t-channel single-top quark production have been known at the NLO accuracy in QCD for quite some time [30][31][32][33] in the five flavour scheme (5FS), and for about ten years in the four-flavour scheme (4FS) [34][35][36]. Much more recently, also the NNLO corrections have been computed [37], also including the decay of the top quark in the narrow width approximation up to the same level of accuracy, but neglecting some interference contributions in the NNLO corrections [38,39]. The NLO corrections in the electroweak coupling have been computed [40][41][42] and are found to be small for the inclusive production, but can be significantly enhanced in certain regions of phase space.…”