NNLO event generation for $$ pp\to Zh\to {\mathrm{\ell}}^{+}{\mathrm{\ell}}^{-}b\overline{b} $$ production in the SM effective field theory

Abstract

We consider associated Zh production with Z → ℓ+ℓ− and $$ h\to b\overline{b} $$ h → b b ¯ decays in hadronic collisions. In the framework of the Standard Model effective field theory (SMEFT) we calculate the QCD corrections to this process and achieve next-to-next-to-leading order plus parton shower (NNLO+PS) accuracy using the MiNNLOPS method. This precision is obtained for a subset of six SMEFT operators, including the corrections from effective Yukawa- and chromomagnetic dipole-type interactions. Missing higher-order QCD effects associated with the considered dimension-six operators are estimated to have a relative numerical impact of less than a percent on the total rate once existing experimental limits on the relevant Wilson coefficients are taken into account. We provide a dedicated Monte Carlo (MC) code that evaluates the NNLO SMEFT corrections on-the-fly in the event generation. This MC generator is used to study the numerical impact of NNLO+PS corrections on the kinematic distributions in $$ pp\to Zh\to {\mathrm{\ell}}^{+}{\mathrm{\ell}}^{-}b\overline{b} $$ pp → Zh → ℓ + ℓ − b b ¯ production employing simple SMEFT benchmark scenarios. We identify the invariant mass $$ {m}_{b\overline{b}} $$ m b b ¯ of the two b-tagged jets as well as the three-invariant jet mass $$ {m}_{b\overline{b}j} $$ m b b ¯ j as particularly interesting observables to study SMEFT effects. These distributions receive contributions that change both their normalisation and shape with the latter modifications depending on the exact jet definition. To our knowledge SMEFT effects of this type have so far not been discussed in the literature. The presented MC generator can also serve as a starting point to obtain NNLO+PS accuracy for a suitable enlarged set of effective operators in the future.

Loop counting matters in SMEFT

“…The latter process has been treated for instance in [48][49][50]. Detailed calculations of Zh production in pp collisions including SMEFT corrections have recently appeared in [51,52].…”

B-hadron production at the LHC from bottom-quark pair production at NNLO+PS

“…Leading-order (LO) Feynman diagrams for this process are shown in Figure 1. Our calculation is based on the MiNNLO PS method [53,54], which was originally developed and later used for several colour-singlet processes [55][56][57][58][59][60][61][62]. More precisely, we employ the extension of the MiNNLO PS method that was derived and applied to top-quark pair production in Refs.…”

High precision theory predictions in the Higgs sector

“…Recent updates for pp → Z H production also include NNLO+PS results with H → b b, in the SM [35] as well as including anomalous Yukawa couplings [36]. NNLO results with NNLO Higgs boson decays to massive b-quarks, including anomalous HVV couplings, have been calculated in Ref.…”