Higgs-boson-pair production H(→bb¯)H(→γγ

Abstract

arXiv:1804.07130v3 [hep-ph] 15 Jul 2019 Higgs boson are very different among the SM, two-Higgs doublet models (2HDM), and MSSM. One of the probes of Higgs self-coupling is Higgs-boson-pair production at the LHC [4][5][6]. There have been a large number of works in literature on Higgs-pair production in the SM [7], in model-independent formalism [8], in models beyond the SM [9], and in SUSY [10]. The predictions for various models are largely different such that the production rates can give valuable information on the self-coupling λ 3H . In the SM, Higgs-pair production receives contributions from both the triangle and box diagrams, which interfere with each other. It is only the triangle diagram that involves the Higgs self-trilinear coupling λ 3H , yet the top-Yukawa coupling appears in both triangle and box diagrams. Therefore, we have to disentangle the triangle diagram from the box diagram in order to probe the Higgs trilinear coupling. In Ref.[11], we pointed out that the triangle diagram, with s-channel Higgs propagator, is more important at low invariant-mass region than the box diagram. Thus, the Higgs-boson pair from the triangle diagram tends to have lower invariant mass, and therefore the opening angle in the decay products of each Higgs boson tends to be larger than that from the box diagram. Indeed, the opening angle separations ∆R γγ and ∆R bb between the decay products of the Higgs-boson pair are very useful variables to disentangle the two sources. However, in Ref. [11] we only assumed some level of signal uncertainties to evaluate the sensitivity to the parameter space of self-coupling λ 3H and the top-Yukawa coupling g S t , without calculating all the other SM backgrounds, e.g., jet-fake backgrounds, single Higgs associated backgrounds, and non-resonant backgrounds.In this work, we perform the most up-to-date comprehensive signal-background analysis for Higgs-pair production through gluon fusion and the HH → bbγγ decay channel. For other production and decay channels and some combined analyses, see Refs. [12]. We simulate the signal and all background processes using simulation tools as sophisticated as what experimentalists use. The signal subprocess is gg → HH → bbγγ with various values for λ 3H . The background includes tt, ttγ, single Higgs associated backgrounds (e.g. ZH, ttH, bbH, ggH followed by H → γγ), and non-resonant or jet-fake backgrounds (e.g. bbγγ, bbjγ, bbjj, jjγγ, etc). We found a set of useful selection cuts to reduce the backgrounds. We express the sensitivity that can be achieved in terms of significance. We find that even for the most promising channel HH → bbγγ at the HL-LHC, the significance is still not high enough to establish the Higgs self-coupling at the SM value, though the self-coupling can be constrained to the range 0 < λ 3H < 7.1 at 95% confidence level (CL) with an integrated luminosity of 3000 fb −1 . Taking account of the uncertainties associated with the top-Yukawa coupling and the estimation of backgrounds, we have found that the 95% CL region broadens i...

Leading two-loop corrections to the Higgs boson self-couplings in models with extended scalar sectors

“…Further in the future, a 100-TeV FCC-hh hadron collider with 30 ab −1 of data could allow reaching a 5% accuracy (at 68% CL) on the measurement of the Higgs trilinear coupling [44,45] (see also Ref. [51]). Finally, it will most probably not be possible to probe the Higgs quartic coupling experimentally in a foreseeable future, the involved cross sections being far too small -for instance, with 30 ab −1 of data, the FCC-hh would only be able to constrain the ratio λ exp.…”

Probing the trilinear Higgs boson self-coupling at the high-luminosity LHC via multivariate analysis

“…In a previous work [11], we showed that even with the HL-LHC one cannot establish the self-coupling λ 3H at the SM value using the most promising decay mode HH → (bb)(γγ). Indeed, one can only constrain the self-coupling to be within −1.0 λ 3H 7.6 at 95% CL [11]. These results were based on a conventional cut-based analysis.…”

“…For generation and simulation of backgrounds, we closely follow Ref. [11], except for the use of the post-LHC PDF set of CT14LO [17] and merged cross sections for non-resonant backgrounds. More precisely, for the two main non-resonant backgrounds of bbγγ and ccγγ, we use the merged cross sections and distributions by MLM matching [18,19] with xqcut and Q cut set to 20 GeV and 30 GeV, respectively.…”

“…(2) as adopted in Ref. [20] which might provide more reliable and conservative estimation of the non-resonant backgrounds containing light jets [11].…”

Probing the trilinear Higgs boson self-coupling via single Higgs production at the LHeC

“…For the bbbb production, the observed upper limit by ATLAS using the non-resonant Higgs pair production data is 13 times the SM value at 95% C.L [11]. There are also extensive phenomenological studies on determinning the trilinear Higgs self-coupling directly at the LHC [12][13][14][15][16][17][18][19][20][21], the future electron-positron collider [22][23][24][25], and future high energy hadron colliders [26][27][28][29][30][31][32][33][34], in which strict constraints are obtained with higher integrated luminosities and energies. On the other hand, an indirect method is proposed for constraining the Higgs self-coupling via single Higgs production at next-to-leading order (NLO) [24,[35][36][37][38][39].…”