CYGNUS: Feasibility of a nuclear recoil observatory with directional sensitivity to dark matter and neutrinos

TL;DR

CYGNUS proposes a large-scale, directional dark matter and neutrino detector using TPCs filled with helium and SF6, capable of distinguishing WIMP signals from neutrino backgrounds and observing various neutrino sources.

Contribution

This paper presents the first detailed analysis of a 1000 m³-scale directional detector for low-energy nuclear recoils, demonstrating its potential to explore new dark matter and neutrino physics parameter spaces.

Findings

Capable of distinguishing 10 GeV WIMP signals from solar neutrino background.

Can observe 10-40 solar neutrinos depending on energy threshold.

Extends sensitivity to sub-10 GeV dark matter interactions.

Abstract

Now that conventional weakly interacting massive particle (WIMP) dark matter searches are approaching the neutrino floor, there has been a resurgence of interest in detectors with sensitivity to nuclear recoil directions. A large-scale directional detector is attractive in that it would have sensitivity below the neutrino floor, be capable of unambiguously establishing the galactic origin of a purported dark matter signal, and could serve a dual purpose as a neutrino observatory. We present the first detailed analysis of a 1000 m$^3$-scale detector capable of measuring a directional nuclear recoil signal at low energies. We propose a modular and multi-site observatory consisting of time projection chambers (TPCs) filled with helium and SF$_6$ at atmospheric pressure. Depending on the TPC readout technology, 10-20 helium recoils above 6 keVr or only 3-4 recoils above 20 keVr would suffice to distinguish a 10 GeV WIMP signal from the solar neutrino background. High-resolution charge readout also enables powerful electron background rejection capabilities well below 10 keV. We detail background and site requirements at the 1000 m$^3$-scale, and identify materials that require improved radiopurity. The final experiment, which we name CYGNUS-1000, will be able to observe 10-40 neutrinos from the Sun, depending on the final energy threshold. With the same exposure, the sensitivity to spin independent cross sections will extend into presently unexplored sub-10 GeV parameter space. For spin dependent interactions, already a 10 m$^3$-scale experiment could compete with upcoming generation-two detectors, but CYGNUS-1000 would improve upon this considerably. Larger volumes would bring sensitivity to neutrinos from an even wider range of sources, including galactic supernovae, nuclear reactors, and geological processes.