Neutrino signatures in primordial non-gaussianities

Abstract

We study the cosmological collider phenomenology of neutrinos in an effective field theory. The mass spectrum of neutrinos and their characteristic oscillatory signatures in the squeezed limit bispectrum are computed. Both dS-covariant and slow-roll corrections are considered, so is the scenario of electroweak symmetry breaking during inflation. Interestingly, we show that the slow-roll background of the inflaton provides a chemical potential for the neutrino production. The chemical potential greatly amplifies the oscillatory signal and makes the signal observably large for heavy neutrinos without the need of fine tuning. *

Cosmological collider physics and the curvaton

“…if it is not forbidden by parity. Such a coupling is special since it gives rise to an effective "chemical potential" λ =φ 0 /Λ φ for the fermion Ψ once the inflaton is set to its background value [18,27,28]. It can help production of Ψ even when the fermion mass, m Ψ is somewhat heavier than H without paying significant Boltzmann suppression.…”

“…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].…”

Probing P and CP violations on the cosmological collider

“…For light fields, signals are usually large [26]. For heavy fields, signals are in general suppressed by Boltzmann factors, but can be naturally lifted up in the presence of chemical potentials [47,48], or in the scenario of special inflation models [49,50]. Even for off-shell production of massive particles, the EFT description still gives a signal which is only power-law-suppressed [51].…”

In search of large signals at the cosmological collider

“…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].…”