Determining the Higgs Boson Self Coupling at Hadron Colliders

TL;DR

This paper assesses how to measure the Higgs self-coupling lambda through Higgs pair production at hadron colliders, focusing on gg -> HH with subsequent decays to WW and challenging final states. The authors perform a detailed LO parton-level analysis of signal and a comprehensive set of backgrounds for the same-sign dilepton and three-lepton channels, incorporating exact loop matrix elements for the signal and a mix of exact and interfaced calculations for backgrounds, along with NLO-inspired K-factors. A chi-square test on the visible invariant mass distribution m_vis, combined across channels and collider scenarios (LHC, SLHC, VLHC), yields sensitivity to deviations in lambda from the SM value, with 95% CL bounds across Higgs masses 150–200 GeV and collider energies up to 200 TeV. They conclude that the LHC can establish a nonzero self-coupling, while a VLHC could measure lambda with 4–25% precision depending on luminosity, demonstrating a viable path to probing the Higgs potential directly. The study also highlights substantial uncertainties from backgrounds, pileup, and higher-order QCD effects, indicating a need for more detailed detector simulations and NLO calculations to refine the bounds.

Abstract

Inclusive Standard Model Higgs boson pair production at hadron colliders has the capability to determine the Higgs boson self-coupling, lambda. We present a detailed analysis of the gg\to HH\to (W^+W^-)(W^+W^-)\to (jjl^\pmν)(jj{l'}^\pmν) and gg\to HH\to (W^+W^-)(W^+W^-)\to (jjl^\pmν)({l'}^\pmν{l''}^\mpν) (l, {l'}, {l''}=e, μ) signal channels, and the relevant background processes, for the CERN Large Hadron Collider, and a future Very Large Hadron Collider operating at a center-of-mass energy of 200 TeV. We also derive quantitative sensitivity limits for lambda. We find that it should be possible at the LHC with design luminosity to establish that the Standard Model Higgs boson has a non-zero self-coupling and that lambda / lambda_{SM} can be restricted to a range of 0-3.8 at 95% confidence level (CL) if its mass is between 150 and 200 GeV. At a 200 TeV collider with an integrated luminosity of 300 fb^{-1}, lambda can be determined with an accuracy of 8 - 25% at 95% CL in the same mass range.

Figures (9)

• Figure 1: Representative Feynman diagrams for the process $gg\to HH$.
• Figure 2: The $pp\to HH\to (W^+W^-)(W^+W^-)\to \ell^\pm{\ell'}^\pm+4j$ differential cross section as a function of the minimum lepton transverse momentum, $p_{Tmin}(\ell)$, for $pp$ collisions at $\sqrt{s}=14$ TeV. Results are shown for $m_H=150$ GeV (solid line), $m_H=160$ GeV (dashed line), $m_H=180$ GeV (dotted line), and $m_H=200$ GeV (dash-dotted line).
• Figure 3: The $pp\to HH\to (W^+W^-)(W^+W^-)\to \ell^\pm{\ell'}^\pm+4j$ differential cross section as a function of the minimum jet transverse momentum, $p_{Tmin}(j)$, for $pp$ collisions at $\sqrt{s}=14$ TeV. Results are shown for $m_H=150$ GeV (solid line), $m_H=160$ GeV (dashed line), $m_H=180$ GeV (dotted line), and $m_H=200$ GeV (dash-dotted line).
• Figure 4: Distribution of the invariant mass of the observable final state particles, $m_{vis}$, after all cuts, in $pp\to\ell^\pm{\ell'}^\pm+4j$ for the signal with a) $m_H=150$ GeV and b) $m_H=180$ GeV, and all backgrounds (except for the contributions from overlapping events and double parton scattering) at the LHC. The dot-dashed curve shows the combined cross section of $WZjjjj$, $WWjjjj$ and $t\bar{t}t\bar{t}$ production.
• Figure 5: Distribution of the invariant mass of the observable final state particles, $m_{vis}$, after all cuts, in $pp\to\ell^\pm{\ell'}^\pm+4j$ for the signal (solid line) with a) $m_H=150$ GeV and b) $m_H=180$ GeV, and all backgrounds (except for the contributions from overlapping events and double parton scattering) at the VLHC (dashed: $WWWjj$, dotted: $t\bar{t}W$, long-dashed: $t\bar{t}Z$, long-dash-dot: $t\bar{t}j$). The dot-dashed curve shows the combined cross section of $WZjjjj$, $WWjjjj$ and $t\bar{t}t\bar{t}$ production.