The Cosmic Neutrino Background (CνB): Its distribution on the surface of the Earth and its manipulation by laboratory-scale diffraction gratings

Nov 16, 2023 - 11:00 am to 12:00 pm

Campus, PAB 102/103

Savas Dimopoulos (Stanford) In Person and zoom

Zoom Recording

The CνB is a cosmological relic analogous to the CMB, and contains information about the universe before it was one-second-old. Reflection of relic neutrinos from the surface of the Earth creates a significant local neutrino-antineutrino asymmetry in a shell seven meters thick around the Earth's surface. This asymmetry far exceeds the expected primordial lepton asymmetry. The resulting gradient of the net neutrino density evades the forty-year-old “no-go” theorem on the vanishing of  O(G_Fermi) neutrino forces on matter.

These forces can be further enhanced by using 1-100 meter structures with shape reminiscent of a sea-urchin: they consist of rods of width w and length L>>w periodically arranged on the surface of the sphere of radius R~L. Such a structure functions as a diffraction grating for relic neutrinos and the induced neutrino-antineutrino asymmetry at its center may point to a new class of experiments to detect the CνB in a laboratory setting. At the same time, such structures can be used to similarly manipulate dark matter.