Multi-Higgs boson production and unitarity in vector-boson fusion at future hadron colliders

Abstract

We study multi-Higgs final states in vector boson fusion (VBF) processes at the LHC and at future proton-proton colliders, focusing on the prospects for measurements at 27 TeV and at 100 TeV. We use an effective Lagrangian which includes higher-dimensional operators in the mass eigenstates which are relevant to VBF processes and relate this to specific param-At the LHC, the dominant SM process of multi-Higgs production is gluon-gluon-fusion (ggF) via a heavy top-quark loop. Current LHC data constrain the triple Higgs self-coupling only very weakly [3], and not at all the quartic Higgs self-coupling. Multiple groups have evaluated the potential for a first meaningful measurement of the triple Higgs self-coupling at future highluminosity runs of the LHC [4-10]. The considered decay channels of the Higgs pair include and bbbb [18, 22, 23]. It is expected that the triple self-coupling can be constrained within 40% accuracy after collecting 3 ab −1 of data at the 14 TeV LHC [24]. There will be no access to the quartic self-coupling. Beyond the LHC, at a future 100 TeV hadron collider, the Higgs pair-production rate is enhanced significantly [9,13,[25][26][27][28][29][30], allowing for a more accurate determination of the Higgs potential.A subdominant process of multi-Higgs production in hadron collisions is vector-bosonfusion (VBF) [31], W + W − → hh, where the W bosons are effectively radiated from incoming quarks. In addition to its dependence on the Higgs self-interaction, this process also gives access to the hhW W coupling, which is another SM interaction that has not been accessible by other means. In fact, the hVV (V = W ± , Z ) couplings can be derived from the precise measurement of the decay branching fractions h → W W * and h → Z Z * at the LHC, up to a common normalization factor. The current LHC data on the decay branching fractions for these channels are consistent with the SM predictions [32, 33]. By contrast, there are no significant constraints from data on hhV V direct couplings.The VBF mode of double-Higgs production at hadron colliders has been studied in Refs. [34][35][36][37][38]. Beyond tree level, the NLO QCD correction enhances the cross section by ∼ 7% [39,40]. In the high-luminosity mode of the LHC (HL-LHC) with 3000 fb −1 at 14 TeV, the hhV V interaction can be constrained to 20%. A 100 TeV hadron collider has the potential to reduce the uncertainty down to 1% [37]. The hhW W coupling is also accessible in the W ± W ± h final state. In Ref. [41] it is found that this particular final state can constrain this coupling to O(100%) at the HL-LHC, and to 20% at a 100 TeV collider.The other modes of double Higgs production are tt hh or V hh production. The production rates of these mode are smaller than ggF and VBF mode. The discussion of these modes is beyond the scope of current work. For interested readers, we refer to [39,40,[42][43][44][45][46][47][48].Measuring the quartic Higgs self-coupling in the SM is a much more challenging task. At the 14 TeV LHC, the cross section of g g → hhh is onl...

Exploring anomalous couplings in Higgs boson pair production through shape analysis

“…The trilinear Higgs boson coupling λ can be constrained by measurements of Higgs boson pair production [1,2], where the gluon fusion channel yields the largest cross section, and the most stringent 95% CL limits on the total gg → HH cross section at √ s = 13 TeV are currently σ HH max = 6.9 × σ SM , constraining trilinear coupling modifications to the range −5.0 ≤ λ/λ SM ≤ 12.0 [1]. The trilinear Higgs couplings can also be constrained in an indirect way, through measurements of processes which are sensitive to these couplings via electroweak corrections [3][4][5][6][7][8][9][10][11][12][13][14]. Such processes offer important complementary information, however they are susceptible to other BSM couplings entering the loop corrections at the same level, and therefore the limits on c hhh = λ/λ SM extracted this way may be more model dependent than the ones extracted from the direct production of Higgs boson pairs.…”

Universal relations in composite Higgs models

“…The VBF channel has been studied previously [54][55][56][57][58] and the prospect at a future lepton collider has also been considered [66][67][68][69][70]. On the other hand, we are not aware of any studies in the associated production channel or the off-shell single Higgs decay channel.…”

“…In particular, the HHVV coupling sits among the least tested sectors of the SM Higgs boson. A number of theoretical studies exist in the literature [54][55][56][57][58], although none specifically addresses the issue of measuring the tensor structures, which requires including the complete list of operators up to O(p 4 ). Therefore, it is clear that testing the universal relation is a long-term program and should be among the priorities of the future experimental program on the Higgs boson.…”

Collider and gravitational wave complementarity in exploring the singlet extension of the standard model

“…[75](for other studies, see e.g. [78,[165][166][167][167][168][169][170]). Here the inner and outer bar regions denote the 68%CL and 95%CL results.…”