Higher-order QCD effects in the Higgs to ZZ search channel at the LHC

TL;DR

This study develops a consistent framework to assess higher-order QCD effects in the Higgs to ZZ search channel at the LHC by performing soft-gluon resummation to NLL accuracy for ZZ production and matching to LO, with comparisons to fixed-order NLO and MC@NLO. Using $m_h=200$ GeV, it analyzes signal and irreducible ZZ background, showing that resummation modestly affects total rates but significantly shapes transverse momentum distributions and can enhance the signal-to-background ratio when applying a cut on the ZZ pair transverse momentum. A fully transverse angular variable, $\Delta\phi_T$, is introduced as a CP-sensitive observable, offering a robust probe of the Higgs CP nature. The results indicate that a judicious $p_T^{ZZ}$ cut can boost discovery potential and CP studies, though nonperturbative effects and some subleading contributions are not included and may alter quantitative outcomes.

Abstract

We present a consistent analysis of the signal as well as the irreducible background for the search of the SM Higgs boson in the ZZ decay channel at the LHC. Soft-gluons effects are resummed up to next-to-leading logarithmic accuracy, and the results are compared to those obtained with fixed order calculations and the MC@NLO event generator. The soft-gluon effects are typically modest but should be taken into account when precise predictions are demanded. Our results show that the signal over background ratio can be significantly enhanced with a cut on the transverse momentum pt(ZZ) of the ZZ pair. We also introduce a fully transverse angular variable that could give information about the CP nature of the Higgs boson.

Figures (9)

• Figure 1: Comparison of the transverse momentum spectra of the $ZZ$ pair obtained at NLL+LO (solid) with MC@NLO (dashes) and NLO results (dots). No cuts are applied.
• Figure 2: Comparison of the transverse momentum spectra of the $ZZ$ pair obtained at NLL+LO for different values of the resummation scale $Q$. No cuts are applied.
• Figure 3: Comparison of the transverse momentum spectra of one of the $Z$ at NLL+LO (solid) with NLO (dots) and MC@NLO (dashed) results. The lower part of the plot shows the NLO and MC@NLO results normalized to NLL+LO.
• Figure 4: Transverse momentum spectra of the leptons: NLL+LO (solid), MC@NLO (dashes) and NLO (dots).
• Figure 5: Same as in Fig. \ref{['fig:ptleptons_cuts']} but for the $\Delta\phi_T$ distribution.