Disentangling Dimension Six Operators through Di-Higgs Boson Production

TL;DR

This study demonstrates how dimension-six Higgs–gluon operators, O1 and O2, can leave measurable imprints on Higgs pair production, offering a model-independent way to probe whether new TeV-scale colored states gain mass from electroweak symmetry breaking. By analyzing both rate and the differential m_hh distribution, the authors show how O1 and O2 produce distinct signatures that can help disentangle the underlying UV physics, even when direct observation of new states is difficult. They examine experimental constraints from the Tevatron and electroweak precision data, and outline LHC strategies for mh around 120 GeV and 180 GeV, including the bbγγ and WWWW final states, respectively, supported by Monte Carlo simulations. The work argues that Higgs pair production could reveal the ultraviolet structure behind new colored states and guide interpretations of any direct discoveries at the LHC.

Abstract

New physics near the TeV scale can generate dimension-six operators that modify the production rate and branching ratios of the Higgs boson. Here, we show how Higgs boson pair production can yield complementary information on dimension-six operators involving the gluon field strength. For example, the invariant mass distribution of the Higgs boson pair can show the extent to which the masses of exotic TeV-scale quarks come from electroweak symmetry breaking. We discuss both the current Tevatron bounds on these operators and the most promising LHC measurement channels for two different Higgs masses: 120 GeV and 180 GeV. We argue that the operators considered in this paper are the ones most likely to yield interesting Higgs pair physics at the LHC.

Figures (7)

• Figure 1: The contributions to Standard Model Higgs pair production are dominated by loops containing top quarks.
• Figure 2: The two diagrams that contribute to Higgs pair production coming from the higher dimension operators $\mathcal{O}_1$ and $\mathcal{O}_2$. In the first diagram, a new $g$--$g$--$h$ vertex combines with the Standard Model three Higgs boson coupling.
• Figure 3: The ratio of $\sigma(gg \rightarrow hh)$ to the Standard Model di-Higgs cross section for $m_h = 120$ GeV. This includes the effect of interference between the contributions from $\mathcal{O}_1$, $\mathcal{O}_2$, and the Standard Model. We assume the new contribution to di-Higgs production inherit the same NLO K-factors as the Standard Model. The Standard Model cross section is 30 fb, and the allowed range in Eq. (\ref{['Eqn:DirectGammaGamma']}) from direct Tevatron searches is $-2.8 \!\mathrel{\hbox{$\sim$ $<$}} (c_1 + c_2) \!\mathrel{\hbox{$\sim$ $<$}} 2.1$.
• Figure 4: Differential cross-sections as a function of $m_{hh}$. In the top graph $c_2 = 0$ is fixed while $c_{1}$ varies, and in the bottom graph $c_1 = 0$ is fixed while $c_{2}$ varies. We have set $m_{h}= 120$ GeV and $m_{t}=174.3$ GeV. The curves for $m_h = 180$ GeV are quite similar, with the trivial modification that the threshold energy is changed. Note that the asymptotic behavior at large $m_{hh}$ is controlled by the difference $|c_1 - c_2|$. When $c_1 = -0.5$ and $c_2 = 0$, there is a pronounced dip at $m_{hh} = 400$ GeV, coming from interference between $\mathcal{O}_1$ and the Standard Model top loops.
• Figure 5: Differential cross-sections as a function of $m_{hh}$ for $m_{h}= 120$ GeV. Here, the single Higgs production rate is fixed by fixing $(c_1 + c_2)$, but the properties of di-Higgs production are clearly modified as the proportion of $\mathcal{O}_1$ and $\mathcal{O}_2$ changes.