Searches for other vacua. Part II. A new Higgstory at the cosmological collider

Abstract

The detection of an oscillating pattern in the bispectrum of density perturbations could suggest the existence of a high-energy second minimum in the Higgs potential. If the Higgs field resided in this new minimum during inflation and was brought back to the electroweak vacuum by thermal corrections during reheating, the coupling of Standard Model particles to the inflaton would leave its imprint on the bispectrum. We focus on the fermions, whose dispersion relation can be modified by the coupling to the inflaton, leading to an enhanced particle production during inflation even if their mass during inflation is larger than the Hubble scale. This results in a large non-analytic contribution to non-Gaussianities, with an amplitude f NL as large as 100 in the squeezed limit, potentially detectable in future 21-cm surveys. Measuring the contributions from two fermions would allow us to compute the ratio of their masses, and to ascribe the origin of the signal to a new Higgs minimum. Such a discovery would be a tremendous step towards understanding the vacuum instability of the Higgs potential, and could have fascinating implications for anthropic considerations.

Cosmological collider physics and the curvaton

“…This is the focus of the "cosmological collider physics" program [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]. For various recent ideas in this direction see, [18][19][20][21][22][23][24][25][26][27][28].…”

On the inflationary massive field with a curved field manifold

“…From this point of view, one well-studied example is quasi-single field inflation (QSFI) [7][8][9][10][11][12], where the extra fields during inflation with mass of O(H) can leave unique signatures in the primordial bispectrum of curvature perturbation. This idea has been further developed into model-independent frameworks for probing primordial physics, such as the proposals of cosmological collider physics [13][14][15][16][17][18][19][20][21] and primordial standard clocks [22][23][24][25].…”

In search of large signals at the cosmological collider

“…Fig. 4), [12] evaluates it at the saddle point of the integral while [16] used an "improved" late-time expansion. None of these worked perfectly.…”

“…(We will henceforth refer to this oscillatory shape the "signal.") Detecting such a signal at this so-called cosmological collider offers direct evidence of new physics particles and a tool of studying their properties [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21].…”

“…Therefore, when µ m, the enhancement can help to largely cancel the Boltzmann suppression, leaving an O(1) rate for particle production. Using this mechanism to generate large signals has been explored in several directions in the context of cosmological collider physics [12,16,17].…”