Cosmic Neutrino Detector: A New Way to Glimpse the Beginning of Time express
Imagine the early Universe as a giant balloon, instantly inflated to incredible size. The tiny bumps on its surface are frozen quantum ripples that later became galaxy clusters. This rapid inflation left behind an ancient glow — a map of the sky that astronomers study.
Hidden in those patterns could be traces of superheavy twin neutrinos. Normally invisible, they might be revealed by a special interaction introduced in new research: like a magnet, it attracts particles with a particular "spin". Then a clear imprint emerges on the celestial sphere, like a watermark.
Finding such an imprint would be a breakthrough. It would prove heavy neutrinos exist and explain why our neutrinos are almost weightless. The secret lies in the seesaw effect: the more massive the invisible twins, the lighter the familiar particles become. The Big Bang turns into a microscope, letting us peer into physics beyond the Standard Model.
Original abstract
as written by the authors arXiv:2605.21419
We study cosmological collider (CC) signatures generated by right-handed neutrino loops in the setup of inflation combined with the neutrino seesaw mechanism. We formulate the inflaton interaction with the right-handed neutrinos through a unique dimension-5 operator respecting shift symmetry, which induces an effective chemical potential in the slow-roll background, leading to helicity-dependent production of right-handed neutrinos and enhancing the CC signatures. The right-handed neutrino is described by a two-component Weyl spinor with a Majorana mass term. Using the Schwinger-Keldysh formalism, we derive a set of seed integrals for fermion propagators of the right-handed Majorana neutrino. With these, we compute the factorized nonlocal contributions to the three-point inflaton correlator generated by the triangle loop of right-handed neutrinos. We show that the chemical potential can substantially soften the heavy-mass Boltzmann suppression and amplify the oscillatory non-Gaussianity signatures associated with the dominant helicity mode. We systematically analyze the spinor structure, the factorization of fermion triangle loop, the loop-momentum integrals and the time seed integrals, which give a controlled computation of the nonlocal contributions to the CC signals of the right-handed neutrinos.
The seesaw effect links the mass of ordinary neutrinos with superheavy twins: the more massive the heavy partner, the lighter our neutrino.