We study the prospects of observing the non-resonant di-Higgs pair production in the Standard Model (SM) at the high luminosity run of the 14 TeV LHC (HL-LHC), upon combining multiple final states chosen on the basis of their yield and cleanliness. In particular, we consider the bbγγ, bbτ + τ − , bbW W * , W W * γγ and 4W channels mostly focusing on final states with photons and/or leptons and study 11 final states. We employ multivariate analyses to optimise the discrimination between signal and backgrounds and find it performing better than simple cut-based analyses. The various differential distributions for the Higgs pair production have non-trivial dependencies on the Higgs self-coupling (λ hhh ). We thus explore the implications of varying λ hhh for the most sensitive search channel for the double Higgs production, viz., bbγγ. The number of signal events originating from SM di-Higgs production in each final state is small and for this reason measurement of differential distributions may not be possible. In order to extract the Higgs quartic coupling, we have to rely on the total number of events in each final state and these channels can be contaminated by various new physics scenarios. Furthermore, we consider various physics beyond the standard model scenarios to quantify the effects of contamination while trying to measure the SM di-Higgs signals in detail. In particular, we study generic resonant heavy Higgs decays to a pair of SM-like Higgs bosons or to a pair of top quarks, heavy pseudoscalar decaying to an SM-like Higgs and a Z-boson, charged Higgs production in association with a top and a bottom quark and also various well-motivated supersymmetric channels. We set limits on the cross-sections for the aforementioned new physics scenarios, above which these can be seen as excesses over the SM background and affect the measurement of Higgs quartic coupling. We also discuss the correlations among various channels which can be useful to identify the new physics model. 2.5.3 The 4 final state 35 2.6 Summarising the non-resonant search results 36 3 Ramifications of varying the Higgs self-coupling 37 4 Contaminations to non-resonant di-Higgs processes 40 4.1 The hh(+X) channels 41 4.2 The h + X channels 46 4.3 Null Higgs channels 49 A Appendix A 68 B Appendix B 69
In this work, we show the importance of searches for heavy resonant scalars (H) and pseudoscalars (A). Taking cue from the present searches, we make projections for searches in an extended scalar sector at the high luminosity run of the Large Hadron Collider. We study the three most relevant search channels, i.e., H → hh, H/A → tt and bbH/A. Upon studying multifarious final states for the resonant double Higgs production, we find that the bbγγ (σ(pp → H → hh) ∈ [81.27, 14.45] fb for m H ∈ [300, 600] GeV at 95% C.L.) and bbbb ([5.4, 2.5] fb for m H ∈ [800, 1000] GeV at 95% C.L.) channels are the most constraining. For the bbH channel, we can exclude σ(pp → bbH) ∈ [22.2, 3.7] fb for m H ∈ [300, 500] GeV. Finally, we consider the phenomenological Minimal Supersymmetric Standard Model as an example and impose various present constraints and our future direct search-limits and obtain strong constraints on the m A − tan β parameter space, where m A and tan β are respectively the mass of the pseudoscalar and the ratio of the vacuum expectation values of the two Higgs doublets. Assuming that the heavy Higgs boson decays only to Standard Model (SM) states, we find that the H → hh → bbγγ (H → tt) channel excludes tan β as low as 4 (m A ∈ [400, 800] GeV) at 95% CL. This weakens up to ∼ 5.5 when the bbH channel dominates. Upon allowing for non-SM decay modes, the limits weaken.
In this work, we analyse and demonstrate possible strategies to explore extended Higgs sector of the Minimal Supersymmetric Standard Model (MSSM). In particular we concentrate on heavy Higgs decays to electroweakinos. We analyse the Higgs to electroweakino decays in the allowed MSSM parameter space after taking into account 13 TeV LHC searches for supersymmetric particles and phenomenological constraints such as flavour physics, Higgs measurements and dark matter constraints. We explore some novel aspects of these Higgs decays. The final states resulting from Higgs to electroweakino decays will have backgrounds arising from the Standard Model as well as direct electroweakino production at the LHC. We demonstrate explicit kinematical differences between Higgs to electroweakino decays and associated backgrounds. Furthermore, we demonstrate for a few specific example points, optimised analysis search strategies at the high luminosity LHC (HL-LHC) run. Finally, we comment on possible search strategies for heavy Higgs decays to exotic final states, where the lightest chargino is long lived and leads to a disappearing track at the LHC.
An $$H^\pm W^{\mp } Z$$ H ± W ∓ Z interaction at the tree level is a common feature of new physics models that feature scalar triplets. In this study, we aim to probe the strength of the aforementioned interaction in a model-agnostic fashion at the futuristic 27 TeV proton-proton collider. We assume that the $$H^\pm $$ H ± couples dominantly to ($$W^\pm ,Z$$ W ± , Z ) and (t, b) and specifically study the processes that involve the $$H^\pm W^{\mp } Z$$ H ± W ∓ Z vertex at the production level, that is, $$p p \rightarrow H^\pm j j$$ p p → H ± j j and $$p p \rightarrow Z H^\pm $$ p p → Z H ± . Moreover, we look into both $$H^\pm \rightarrow W^\pm Z,~t b$$ H ± → W ± Z , t b decays for either production process. Our investigations reveal that the $$H^\pm j j$$ H ± j j production process has a greater reach compared to $$Z H^\pm $$ Z H ± . Moreover, the discovery potential of a charged Higgs improves markedly with respect to the earlier studies corresponding to lower centre-of-mass energies. Finally, we recast our results in the context of the popular Georgi–Machacek model.
The prospects of observing the non-resonant di-Higgs production in the Standard Model at the proposed high energy upgrade of the LHC, viz. the HE-LHC ($$ \sqrt{s} $$ s = 27 TeV and ℒ = 15 ab−1) is studied. Various di-Higgs final states are considered based on their cleanliness and production rates. The search for the non-resonant double Higgs production at the HE-LHC is performed in the $$ b\overline{b}\gamma \gamma $$ b b ¯ γγ , $$ b\overline{b}{\tau}^{+}{\tau}^{-} $$ b b ¯ τ + τ − , $$ b\overline{b}{WW}^{\ast } $$ b b ¯ WW ∗ , WW∗γγ, $$ b\overline{b}{ZZ}^{\ast } $$ b b ¯ ZZ ∗ and $$ b\overline{b}{\mu}^{+}{\mu}^{-} $$ b b ¯ μ + μ − channels. The signal-background discrimination is performed through multivariate analyses using the Boosted Decision Tree Decorrelated (BDTD) algorithm in the TMVA framework, the XGBoost toolkit and Deep Neural Network (DNN). The variation in the kinematics of Higgs pair production as a function of the self-coupling of the Higgs boson, λh, is also studied. The ramifications of varying λh on the $$ b\overline{b}\gamma \gamma $$ b b ¯ γγ , $$ b\overline{b}{\tau}^{+}{\tau}^{-} $$ b b ¯ τ + τ − and $$ b\overline{b}{WW}^{\ast } $$ b b ¯ WW ∗ search analyses optimized for the SM hypothesis is also explored.
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