Abstract
In models with extended scalars and CP violation, resonance searches in double Higgs final states stand in competition with related searches in top quark final states as optimal channels for the discovery of beyond the Standard Model (BSM) physics. This complementarity is particularly relevant for benchmark scenarios that aim to highlight multi-Higgs production as a standard candle for the study of BSM phenomena. In this note, we compare interference effects in $t\bar t$ final states with correlated phenomena in double Higgs production in the complex singlet and the complex 2-Higgs-Doublet Models. Our results indicate that the BSM discovery potential in di-Higgs searches can be underestimated in comparison to $t\bar t $ resonance searches. Top pair final states are typically suppressed due to destructive signal-background interference, while $hh$ final states can be enhanced due to signal-signal interference. For parameter choices where the two heavy Higgs resonances are well separated in mass, top final states are suppressed relative to the naive signal expectation, while estimates of the production cross section times branching ratio remain accurate at the ${\cal{O}}(10\%)$ level for double Higgs final states.
Highlights
The search for new physics beyond the Standard Model remains a priority of the Large Hadron Collider (LHC) phenomenology program
Our results indicate that the beyond the Standard Model (BSM) discovery potential in di-Higgs searches can be underestimated in comparison to tt resonance searches
In this paper we have shown that the signal-background interference that the ATLAS and CMS experiments are already considering in setting limits on models of the kind discussed in this work needs to be extended to signalsignal interference effects, in particular when considering di-Higgs production as a BSM discovery tool
Summary
The search for new physics beyond the Standard Model remains a priority of the Large Hadron Collider (LHC) phenomenology program. Recent investigations [1,2,3,4] highlight the point that the nonobservation of new physics can be reconciled with “standard” Higgs sector extensions far away from their decoupling limits This is possible when the non-Standard Model (non-SM) degrees of freedom have suppressed production cross sections, or when they are hidden in channels that are experimentally difficult to observe. The sensitivity from di-Higgs final states [24] can be underestimated relative to top pair production; i.e., destructive interference effects in tt searches correlate with constructive interference in hh searches in parameter regions of the C2HDM that are allowed in the light of current LHC searches We contrast these findings against results obtained for the CxSM.
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