Scale-invariant resonance tagging in multijet events and new physics in Higgs pair production

TL;DR

This work introduces scale-invariant resonance tagging to unify boosted and resolved multijet analyses, enabling a single strategy to search for pair-produced heavy resonances across broad mass ranges. It applies the method to resonant Higgs-pair production in warped extra dimensions, focusing on radion and KK-graviton mediators that decay to b-quark pairs. The study demonstrates that the all-hadronic HH→4b final state, combined with jet-substructure tagging and b-tagging, provides meaningful sensitivity and model-independent limits, with substantial reach at 14 TeV. The results map onto concrete radion/graviton benchmark scenarios, illustrating robust exclusion capabilities and highlighting the potential for complementary channels in LHC new-physics searches.

Abstract

We study resonant pair production of heavy particles in fully hadronic final states by means of jet substructure techniques. We propose a new resonance tagging strategy that smoothly interpolates between the highly boosted and fully resolved regimes, leading to uniform signal efficiencies and background rejection rates across a broad range of masses. Our method makes it possible to efficiently replace independent experimental searches, based on different final state topologies, with a single common analysis. As a case study, we apply our technique to pair production of Higgs bosons decaying into $b\bar{b}$ pairs in generic New Physics scenarios. We adopt as benchmark models radion and massive KK graviton production in warped extra dimensions. We find that despite the overwhelming QCD background, the $4b$ final state has enough sensitivity to provide a complementary handle in searches for enhanced Higgs pair production at the LHC.

Figures (19)

• Figure 1: Schematic diagrams for the generic process $pp \to X \to 2 Y \to 4 z$ in the boosted (left plot) regime, corresponding to large values of the mass ratio $r_M=M_X/2M_Y$, and in the resolved (right plot) regime, corresponding to small values of $r_M$.
• Figure 2: Left plot: the fraction of events with a given number of reconstructed jets, as a function of the resonance mass ratio $r_{M}$ (Eq. (\ref{['eq:rm']}), for parton-level toy Monte Carlo events. No cuts have been applied to the final state particles. Right plot: the same at hadron-level, with the basic cuts Eq. (\ref{['eq:cuts']}) applied. Note that at parton level the only possible topologies are two-, three- and four-jet events, so their sum is equal to the total number of events. A higher density of mass points has been used in the left-hand figure than in the right-hand figure, and for $r_M \lesssim 1.5$ only the left-hand figure gives a faithful representation of the structures that are present.
• Figure 3: Flow chart summarizing the basic structure of the resonance-pair tagger algorithm. The quality conditions are specified in the text.
• Figure 4: Left plot: The efficiency of the resonance pair tagging algorithm as a function of resonances mass ratio $r_{M}$ Eq. (\ref{['eq:rm']}) for parton-level toy Monte Carlo events. We show both the total efficiency and the break-up for the 2-tag, 1-tag and 0-tag samples. No cuts have been applied to the final state particles. Right plot: same for hadron-level events, which include the basic jet selection cuts.
• Figure 5: The efficiency of the resonance pair tagging algorithm as a function of the resonance mass ratio $r_{M}$, Eq. (\ref{['eq:rm']}), for toy Monte Carlo events, comparing parton-level and hadron-level results for LHC 8 TeV. We show the total efficiency (upper left plot) and then the break-up for the 2-tag, 1-tag and 0-tag samples. The parton level results including the basic selection cuts Eq. (\ref{['eq:cuts']}) are very close to the inclusive parton level case and thus not shown here.