Higgs self coupling measurement in e+e- collisions at center-of-mass energy of 500 GeV

TL;DR

This work assesses the feasibility of measuring the Higgs trilinear self-coupling $\lambda_{hhh}$ at a future $e^+e^-$ collider with $\sqrt{s}=500$ GeV by studying the small $hhZ$ production cross-section for $m_h\approx120$ GeV. Using GRACE- and PYTHIA-based event generation, a TESLA-like detector model, and a neural-network–driven multivariate analysis, the study demonstrates that, despite overwhelming backgrounds, a precise determination of $\sigma_{hhZ}$ can be achieved and translated into a measurement of $\lambda_{hhh}$ with about 18% relative precision at an integrated luminosity of 2 ab$^{-1}$. The analysis highlights the importance of strong $b$-tagging, accurate jet reconstruction, and advanced discrimination techniques to probe the Higgs potential and test the Standard Model (and, by extension, MSSM scenarios in certain limits). The results illustrate the potential of future linear colliders to illuminate the Higgs sector beyond mass and coupling measurements, by accessing the self-interaction that shapes the Higgs potential.

Abstract

Feasibility of the measurement of the trilinear self-couplings of the Higgs boson is studied. Such a measurement would experimentally determine the structure of the Higgs potential. Full hadronic and semi-leptonic final states of the double-Higgs strahlung have been investigated.

Figures (6)

• Figure 1: Feynman diagrams involved in the $\mathrm{e^+ e^-}$$\rightarrow$$\hbox{\rm h}$$\hbox{\rm h}$$\hbox{\rm Z}$ cross-section via the double Higgs-strahlung.
• Figure 2: MSSM trilinear Higgs self-coupling ($\lambda_{\hbox{$\hbox{\rm h}$}\hbox{$\hbox{\rm h}$}\hbox{$\hbox{\rm h}$}}$) as a function of the mass of the pseudo-scalar Higgs boson mass ($m_{\mathrm A}$) and different assumptions of $m_{\tilde{\mathrm{t}}}$ from 300 GeV/$\mathrm{c^2}$ to 1 TeV/$\mathrm{c^2}$ with a 100 GeV/$\mathrm{c^2}$ step size; the horizontal line corresponds to the standard model value of $\lambda_{\hbox{$\hbox{\rm h}$}\hbox{$\hbox{\rm h}$}\hbox{$\hbox{\rm h}$}}$. A 100 GeV/$\mathrm{c^2}$ Higgs boson mass has been assumed.
• Figure 3: Distribution of the invariant mass of each hemisphere ($\rm M_{hemi}$) for (a) signal and (b) background processes.
• Figure 4: Distribution of the variable DIST (defined in text) for (a) signal and (b) background processes.
• Figure 5: Neural Network output distribution ($NN_{output}$) for $\rm H$$\rm H$$\rm Z$ signal (full histogram) and background (empty histogram) with 500 $\hbox{fb}^{-1}$ and $m_{\mathrm h}$=120 GeV/$\mathrm{c^2}$.