The Future of Higgs Physics

TL;DR

The Future of Higgs Boson Physics argues that precision measurements of the Higgs sector at future e+e− Higgs factories are essential to probe beyond the Standard Model, complementing HL-LHC results. It adopts a SMEFT framework to parameterize deviations in Higgs couplings, width, and rare decays, and analyzes three energy regimes: threshold (≈240–250 GeV) for model-independent Higgs studies, the Z-pole for ultra-high-precision electroweak tests, and energies above the top threshold (550 GeV–1 TeV) to access top Yukawa, Higgs self-coupling, and high-energy SMEFT effects. The work compares circular and linear collider capabilities, highlights the role of beam polarization, and emphasizes the need for robust theory control and extensive detector R&D to realize percent-level sensitivity to new physics at multi-TeV scales. It concludes that precision Higgs and EW measurements can reveal subtle BSM signals and guide future collider decisions, while stressing the importance of engaging early-career scientists in detector design and program planning.

Abstract

In this lecture, I discuss measurements of the properties of the Higgs boson and related observables in the era of Higgs factories. This highly motivated experimental program is the challenge for the next generation of particle physicists.

Figures (10)

• Figure 1: The correspondence between Higgs boson couplings and particle mass, according to the Higgs coupling measurements achieved by the CMS experiment, from CMScouplings. The lower plot shows the residual uncertainties on a linear scale.
• Figure 2: Expected instantaneous luminosities as a function of CM energy for proposed circiular and linear Higgs factories, from LCVision.
• Figure 3: Cross sections for Higgs boson production in $e^+e^-$ annhilation reactions as a function of CM energy, showing also the dominant Feynman diagrams for the reactions $e^+e^-\to ZH$ and $e^+e^-\to \nu\overline{\nu} H$.
• Figure 4: Determination of the Higgs boson mass at 250 GeV from measurement of the $Z$ recoil mass in $e^+e^-\to ZH$ with $Z \to \mu^+\mu^-$, from Yan:2016xyx. The plot shown corresponds to an integrated luminosity of 250 fb$^{-1}$, to be compared to 3 ab$^{-1}$ for the LCF program at 250 GeV.
• Figure 5: Scatter plots from a scan of the parameter space in Two Higgs Doublet (THDM) models, showing the relation between the heavy Higgs boson mass and the fractional deviation of a Yukawa coupling from its SM value. Left: the deviation of the $b$ quark Yukawa coupling in the conventional Type II THDM; Right: the deviation of the $c$ quark Yukawa coupling in the flavorful THDM model of Altmannshofer. The horizontal dashed lines show 3$\sigma$ deviation lines for stages of the LCF program. The bottom such line shows the 3$\sigma$ sensitivity for the full Higgs factory program, either LCF or FCC-ee. From DevinKamal1.