Artistic rendition of relevant interactions for tau lepton appearance from high-energy neutrino interactions (in the rectangular inset). The envisaged ice and water Cherenkov detectors are represented on the center left, while Earth-skimming and space-based observatories are shown on the center right. Image credit: Jackapan Pairin.
Many upcoming neutrino experiments aim to detect extragalactic neutrinos with energies thousands of times higher than ever seen before. These neutrinos contain valuable information about the most energetic — as well as some of the oldest — processes in the Universe. Tau neutrinos, one of three known flavors of neutrinos, have been the main focus of most next-generation neutrino experiments due to properties that make detecting them at high energies easier.
In the cover paper of the latest Physics Review Letters, postdoc Alfonso Garcia Soto, upcoming G1 Pavel Zhelnin, fellow of the department Ibrahim Safa, and Prof. Carlos Argüelles-Delgado show that the other neutrino flavors create tau neutrinos as they cross Earth, and produce a significant and irreducible background to tau neutrino measurements. This is the first such calculation and while it increases the prospects for detection in these upcoming experiments, it highlights the need to design and build next-generation neutrino experiments that are not only sensitive to tau neutrinos, but to all neutrino flavors in order to disentangle the backgrounds.
See A. Garcia Soto, P. Zhelnin, I. Safa, and C. A. Argüelles, "Tau Appearance from High-Energy Neutrino Interactions," Phys. Rev. Lett. 128, 27 April 2022. DOI: 10.1103/PhysRevLett.128.171101.