Cygnus is a proposed global network of large-scale gas time projection chambers (TPCs) with the capability of directionally detecting nuclear and electron recoils at  $$\gtrsim $$  <math> <mo>≳</mo> </math>  keV energies. The primary focus of Cygnus so far has been the detection of dark matter, with directional sensitivity providing a means of circumventing the so-called “neutrino fog”. However, the excellent background rejection and electron/nuclear recoil discrimination provided by the 3-dimensional reconstruction of ionisation tracks could turn the solar neutrino background into an interesting signal in its own right. For example, directionality would facilitate the simultaneous spectroscopy of multiple different flux sources. Here, we evaluate the possibility of measuring solar neutrinos using the same network of gas TPCs built from 10 m $$^3$$  <math> <mmultiscripts> <mrow></mrow> <mrow></mrow> <mn>3</mn> </mmultiscripts> </math>  -scale modules operating under conditions that enable simultaneous sensitivity to both dark matter and neutrinos. We focus in particular on electron recoils, which provide access to low-energy neutrino fluxes like pp, pep,  $$^7$$  <math> <mmultiscripts> <mrow></mrow> <mrow></mrow> <mn>7</mn> </mmultiscripts> </math>  Be, and CNO. An appreciable event rate is already detectable in experiments consisting of a single 10 m $$^3$$  <math> <mmultiscripts> <mrow></mrow> <mrow></mrow> <mn>3</mn> </mmultiscripts> </math>   module, assuming standard fill gases such as CF $$_4$$  <math> <mmultiscripts> <mrow></mrow> <mn>4</mn> <mrow></mrow> </mmultiscripts> </math>   mixed with helium at atmospheric pressure. With total volumes around 1000 m $$^3$$  <math> <mmultiscripts> <mrow></mrow> <mrow></mrow> <mn>3</mn> </mmultiscripts> </math>   or higher, the TPC network could be complementary to dedicated neutrino observatories, whilst entering the dark-matter neutrino fog via the nuclear recoil channel. We evaluate the required directional performance and background conditions to observe, discriminate, and perform spectroscopy on neutrino events. We find that, under reasonable projections for planned technology that will enable 10–30-degree angular resolution and  $$\sim 10$$  <math> <mrow> <mo>∼</mo> <mn>10</mn> </mrow> </math>  % fractional energy resolution, Cygnus could be a competitive directional neutrino experiment.

Australia

Chiara Lisotti

Ciaran O’Hare

Italy

Elisabetta Baracchini

Victoria Bashu

Lindsey Bignell

Ferdos Dastgiri

United States

Majd Ghrear

Gregory Lane

Lachlan McKie

Peter McNamara

Samuele Torelli

CYG $$\nu $$  <math> <mi>ν</mi> </math>  S: detecting solar neutrinos with directional gas time projection chambers

We study the phenomenology of the ‘companion-axion model’ consisting of two coupled QCD axions. The second axion is required to rescue the Peccei–Quinn solution to the strong-CP problem from the effects of colored gravitational instantons. We investigate here the combined phenomenology of axion–axion and axion–photon interactions, recasting present and future single-axion bounds onto the companion-axion parameter space. Most remarkably, we predict that future axion searches with haloscopes and helioscopes may well discover two QCD axions, perhaps even within the same experiment.

Zhe Chen

Archil Kobakhidze

Zachary Picker

Giovanni Pierobon

Phenomenology of the companion-axion model: photon couplings

We present the first proof-of-concept simulations of detectors using biomaterials to detect particle interactions. The essential idea behind a “DNA detector” involves the attachment of a forest of precisely-sequenced single or double-stranded nucleic acids from a thin holding layer made of a high-density material. Incoming particles break a series of strands along a roughly co-linear chain of interaction sites and the severed segments then fall to a collection area. Since the sequences of base pairs in nucleic acid molecules can be precisely amplified and measured using polymerase chain reaction (PCR), the original spatial position of each broken strand inside the detector can be reconstructed with nm precision. Motivated by the potential use as a low-energy directional particle tracker, we perform the first Monte Carlo simulations of particle interactions inside a DNA detector. We compare the track topology as a function of incoming direction, energy, and particle type for a range of ionising particles. While particle identification and energy reconstruction might be challenging without a significant scale-up, the excellent potential angular and spatial resolution ( $$\lesssim 25^\circ $$  <math> <mrow> <mo>≲</mo> <msup> <mn>25</mn> <mo>∘</mo> </msup> </mrow> </math>   axial resolution for keV-scale particles and nm-scale track segments) are clear advantages of this concept. We conclude that a DNA detector could be a cost-effective, portable, and powerful new particle detection technology. We outline the outstanding experimental challenges, and suggest directions for future laboratory tests.