A Cosmological Higgs Collider

TL;DR

The paper introduces the Cosmological Higgs Collider (CHC), a framework where Higgs fluctuations modulate inflaton decay during reheating, enabling Higgs-scale physics to imprint primordial non-Gaussianities. It demonstrates that a viable realization occurs when the inflaton decays predominantly into Higgs-portal scalars, allowing clean SM predictions for CHC signals while mitigating uncontrolled parameter dependence. The authors compute clock-like signals in the squeezed bispectrum arising from SM gauge bosons and the top quark, and discuss potential BSM signals via Higgs-related couplings, showing that CHC can probe high-scale Higgs interactions at inflationary energies. This framework provides a novel link between early-universe cosmology and Higgs phenomenology, with potential diagnostics for both SM processes and new physics.

Abstract

The quantum fluctuations of the Higgs field during inflation could be a source of primordial density perturbations through Higgs-dependent inflaton decay. By measuring primordial non-Gaussianities, this so-called Higgs-modulated reheating scenario provides us a unique chance to probe Higgs interactions at extremely high energy scale, which we call the Cosmological Higgs Collider (CHC). We realize CHC in a simple scenario where the inflaton decays into Higgs-portal scalars, taking account of the decay of the Higgs fluctuation amplitude after inflation. We also calculate the CHC signals of Standard Model particles, namely their imprints in the squeezed bispectrum, which can be naturally large. The concept of CHC can be straightforwardly generalized to cosmological isocurvature colliders with other types of isocurvature perturbations.

Figures (4)

• Figure 1: The ordinary inflation scenario versus modulated reheating, illustrating the Hubble scale (orange) and the decay rate of the inflaton (blue) as functions of time and space coordinates.
• Figure 2: The original "cosmological collider" vs. the "cosmological Higgs collider".
• Figure 3: Left: $|h_0(t)|$ as a function of time $t$. Right: $|\delta h(t)|$ as a function of time $t$. In both panels the blue solid curves represent numerical solutions of (\ref{['heq']}), while black dashed curves correspond to analytical fits (\ref{['htfit']}). For illustration we take $\lambda=0.01$ and $\delta h_\text{ini}=0.05$.
• Figure 4: SM signals at CHC. The blue, purple, and black curves show the signals strength $f_\text{NL,clock}$ as functions of particles' mass for $W$, $Z$, and top quark, respectively. The choice of parameters are $R_h=0.14$, $\lambda=0.01$, $g=0.6$, $y_t=1$ and $c_W=0.88$. Even larger non-Gaussianities are possible if smaller $\lambda$ is chosen.