Scalar production and decay to top quarks including interference effects at NLO in QCD in an EFT approach

Abstract

Scalar and pseudo-scalar resonances decaying to top quarks are common predictions in several scenarios beyond the standard model (SM) and are extensively searched for by LHC experiments. Challenges on the experimental side require optimising the strategy based on accurate predictions. Firstly, QCD corrections are known to be large both for the SM QCD background and for the pure signal scalar production. Secondly, leading order and approximate next-to-leading order (NLO) calculations indicate that the interference between signal and background is large and drastically changes the lineshape of the signal, from a simple peak to a peak-dip structure. Therefore, a robust prediction of this interference at NLO accuracy in QCD is necessary to ensure that higher-order corrections do not alter the lineshapes. We compute the exact NLO corrections, assuming a point-like coupling between the scalar and the gluons and consistently embedding the calculation in an effective field theory within an automated framework, and present results for a representative set of beyond the SM benchmarks. The results can be further matched to parton shower simulation, providing more realistic predictions. We find that NLO corrections are important and lead to a significant reduction of the uncertainties. We also discuss how our computation can be used to improve the predictions for physics scenarios where the gluon-scalar loop is resolved and the effective approach is less applicable.

Electroweak and QCD corrections to Z and W pole observables in the standard model EFT

“…A program of calculations has begun to treat the SMEFT contributions at NLO, for both the QCD and electroweak (EW) contributions. The SMEFT QCD corrections to gauge boson pair production [11,12] and top quark production and decay [13][14][15][16] are known. The electroweak SMEFT corrections to Higgs decays to bb [17][18][19], γγ [20][21][22][23], Zγ [24,25], ZZ [24], and W W [20] have also been computed, along with partial corrections to the Drell Yan process [26].…”

Constraining scalar resonances with top-quark pair production at the LHC

“…Resonant top-quark pair production at the LHC has been analyzed for several of the models mentioned above already. Color neutral resonances decaying into tt have been studied in several works for a large number of models [ effects at NLO in QCD [56][57][58]. The case of a color-octet signal has been considered in [43,52,60,61], also considering other production channels, e.g.…”

“…In fact, they can completely change the line-shape of the resonance from a pure Breit-Wigner peak to a peak-dip structure, or even dip-peak, pure dip or an enhanced peak [50][51][52][53][54][55]. QCD corrections to this effect have recently been computed [56][57][58] and shown to be important. A pilot experimental analysis investigating such interference effects has been presented recently [59].…”

Interference effects in $$ t\overline{t} $$ production at the LHC as a window on new physics

“…The NLO QCD corrections to the interference between signal and background in resonant the process gg → H/A → tt have been calculated recently using an effective field theory approach [64]. In our case, we take into account the QCD corrections simply by rescaling the Higgs signal and the QCD background cross sections by the respective NNLO K-factors K S NNLO (computed using the program SusHi) and K QCD NNLO .…”