Higgs Self-Coupling Measurements at a 100 TeV Hadron Collider

TL;DR

This study assesses the feasibility of measuring the Higgs trilinear self-coupling $\lambda$ at a future 100 TeV hadron collider, focusing on dihiggs production via gluon fusion with the $hh \to b\bar{b}\gamma\gamma$ final state and the complementary $hh+\text{jet}$ topology. The authors perform a realistic simulation including detector effects and reducible backgrounds (notably jet-to-photon and jet-to-$b$-jet fakes), and optimize selection cuts to maximize signal significance. They project a sensitivity of roughly 40% on $\lambda/\lambda_{\text{SM}}$ with 3/ab and about 10–12% with 30/ab, with the combined channels offering the strongest constraint; however, the results are more conservative than earlier Snowmass estimates due to backgrounds and detector realism. The work motivates exploring additional final states and improving detector capabilities to further enhance sensitivity, and highlights the importance of accounting for fake backgrounds in future collider studies.

Abstract

An important physics goal of a possible next-generation high-energy hadron collider will be precision characterisation of the Higgs sector and electroweak symmetry breaking. A crucial part of understanding the nature of electroweak symmetry breaking is measuring the Higgs self-interactions. We study dihiggs production in proton-proton collisions at 100 TeV centre of mass energy in order to estimate the sensitivity such a machine would have to variations in the trilinear Higgs coupling around the Standard Model expectation. We focus on the two b-jets plus diphotons final state, including possible enhancements in sensitivity by exploiting dihiggs recoils against a hard jet. We find that it should be possible to measure the trilinear self-coupling with 40% accuracy given 3/ab and 12% with 30/ab of data.

Figures (6)

• Figure 1: Leading-order parton level distributions (including flat NLO normalisation $K$ factors) of the dihiggs invariant mass $m_{hh}$ and transverse momentum $p_{T,h}$ for $pp \to h h$ at $\sqrt{s} = 100$ TeV for $\lambda=0, \lambda_{\text{SM}}$ and $2\lambda_{\text{SM}}$, shown with the $\lambda/\lambda_{\text{SM}}=1$ case for $\sqrt{s}=14$ TeV for comparison.
• Figure 2: Leading-order parton level distributions of the dihiggs invariant mass $m_{hh}$ and maximum transverse momentum $\max p_{T,h}$ for $pp \to h hj$ at $\sqrt{s} = 100$ TeV for $p_{T,j}\geq 80~\text{GeV}$ and $|\eta_j|\leq 4.5$, for $\lambda=0, \lambda_{\text{SM}}$ and $2\lambda_{\text{SM}}$. We also include the $\lambda/\lambda_{\text{SM}}=1$ case for $\sqrt{s}=14$ TeV for comparison.
• Figure 3: The left panel (a) shows the transverse momentum of the leading photon in $hh\to b\bar{b} \gamma \gamma$ events for $\lambda=0,\lambda_{\text{DM}}$ and $2\lambda_{\text{SM}}$ along with various background contributions, while the right panel (b) shows the subleading photon transverse momentum.
• Figure 4: The left panel (a) displays the differential $m_{b\bar{b}}$ distribution for $\lambda=0,\lambda_{\text{DM}}$ and $2\lambda_{\text{SM}}$ and background contributions. The right panel (b) shows the invariant mass of the 2-photon and 2-$b$-jet system $m_{b\bar{b} \gamma \gamma}$.
• Figure 5: The left panel (a) shows the ratio of the transverse momentum of leading reconstructed Higgs to the transverse momentum of the extra jet for $\lambda=0,\lambda_{\text{SM}}$ and $2\lambda_{\text{SM}}$ as well as the backgrounds. The right panel (b) shows the $\Delta \phi$ between the subleading $b$-let and the $\gamma\gamma$ system for the same data.