Higgs Boson self-coupling measurements using ratios of cross sections

TL;DR

This paper proposes using the ratio of Higgs pair to single Higgs production cross sections, C_HH, to measure the Higgs trilinear self-coupling λ at the LHC by exploiting cancellations of correlated QCD uncertainties. It provides LO and NLO cross-section expressions showing λ and top Yukawa dependence, demonstrates the theoretical stability of C_HH against higher-order corrections, and applies conservative experimental uncertainties to derive prospective constraints. The results indicate that λ can be constrained to be positive at 600 fb^-1 and that at 3000 fb^-1 the precision could reach about +30%/−20%, with the caveat that an accurate determination of the top Yukawa y_t is essential for a model-independent extraction. The study presents the most precise framework to date for determining the Higgs trilinear coupling and highlights the potential need for further refinements and extensions to BSM scenarios.

Abstract

We consider the ratio of cross sections of double-to-single Higgs boson production at the Large Hadron Collider at 14 TeV. Since both processes possess similar higher-order corrections, leading to a cancellation of uncertainties in the ratio, this observable is well-suited to constrain the trilinear Higgs boson self-coupling. We consider the scale variation, parton density function uncertainties and conservative estimates of experimental uncertainties, applied to the viable decay channels, to construct expected exclusion regions. We show that the trilinear self-coupling can be constrained to be positive with a 600/fb LHC dataset at 95% confidence level. Moreover, we demonstrate that we expect to obtain a ~+30% and ~-20 uncertainty on the self-coupling at 3000/fb without statistical fitting of differential distributions. The present article outlines the most precise method of determination of the Higgs trilinear coupling to date.

Figures (11)

• Figure 1: The Higgs pair production diagrams contributing to the gluon fusion process at LO are shown, for a generic fermion $f$.
• Figure 2: The cross sections for single and double Higgs boson production at leading order using the MSTW2008lo68cl PDF set. In the lower plot, the fractional uncertainty due to scale variation is shown in the blue band, as well as the PDF uncertainty in the green band.
• Figure 3: The cross sections for single and double Higgs boson production at next-to-leading order using the MSTW2008nlo68cl PDF set. In the lower plot, the fractional uncertainty due to scale variation is shown in the blue band, as well as the PDF uncertainty in the green band.
• Figure 4: The cross section for double Higgs production and the ratio $C_{HH}$ at next-to-leading order using the MSTW2008nlo68cl PDF set, as a function of $\lambda$ at $y_t = 1$.
• Figure 5: The cross section for double Higgs production and the ratio $C_{HH}$ at next-to-leading order using the MSTW2008nlo68cl PDF set, as a function of $y_t$ at $\lambda = 1$.