Neutrino Scattering on Superfluid Helium with Account for Neutrino Electromagnetic Properties and Collective Effects

Superfluid He-4 is a promising tool for neutrino and dark matter detection. The low-energy neutrino interaction with superfluid He-4 proceeds through coherent elastic neutrino–atom scattering (CE\(\nu\)AS), which has not yet been observed. The first experimental study of CE\(\nu\)AS is under preparation in Sarov using a tritium neutrino source and a superfluid He-4 detector. This will allow testing the neutrino physics of the Standard Model and beyond at unprecedentedly low energies. We develop a theoretical approach for studying neutrino interaction with a superfluid He-4, taking into account single quasiparticle (phonon and roton) production in the target upon tritium neutrino scattering. We show that such collective effects significantly affect the neutrino scattering cross section at energy transfers of the order of 1 meV and less.