Low-energy physics in neutrino LArTPCs

Abstract

In this paper, we review scientific opportunities and challenges related to detection and reconstruction of low-energy (less than 100 MeV) signatures in liquid argon time-projection chamber (LArTPC) neutrino detectors. LArTPC neutrino detectors designed for performing precise long-baseline oscillation measurements with GeV-scale accelerator neutrino beams also have unique sensitivity to a range of physics and astrophysics signatures via detection of event features at and below the few tens of MeV range. In addition, low-energy signatures are an integral part of GeV-scale accelerator neutrino interaction final-states, and their reconstruction can enhance the oscillation physics sensitivities of LArTPC experiments. New physics signals from accelerator and natural sources also generate diverse signatures in the low-energy range, and reconstruction of these signatures can increase the breadth of Beyond the Standard Model scenarios accessible in LArTPC-based searches. A variety of experimental and theory-related challenges remain to realizing this full range of potential benefits. Neutrino interaction cross-sections and other nuclear physics processes in argon relevant to sub-hundred-MeV LArTPC signatures are poorly understood, and improved theory and experimental measurements are needed; pion decay-at-rest sources and charged particle and neutron test beams are ideal facilities for improving this understanding. There are specific calibration needs in the low-energy range, as well as specific needs for control and understanding of radiological and cosmogenic backgrounds. Low-energy signatures, whether steady-state or part of a supernova burst or larger GeV-scale event topology, have specific triggering, DAQ and reconstruction requirements that must be addressed outside the scope of conventional GeV-scale data collection and analysis pathways. Novel concepts for future LArTPC technology that enhance low-energy capabilities should also be explored to help address these challenges.

Convolutional neural network for multiple particle identification in the MicroBooNE liquid argon time projection chamber

“…The energy spectrum predicted by the GENIE simulation for neutrons produced by neutrinos in MicroBooNE is shown in gray, with arbitrary normalization. These theoretical predictions have not been directly validated with data [26], although in the energy range of interest the total (including elastic interactions) neutron-argon cross section has been measured [27]. The neutron-argon total cross section between neutron kinetic energies of 95 and 720 MeV is fairly flat and approximately 700 mb, corresponding to a mean free path in liquid argon of ∼70 cm.…”

Observation of radon mitigation in MicroBooNE by a liquid argon filtration system

“…Far lower in energy, the DarkSide-50 dualphase LArTPC and DEAP single-phase scintillation detector used O(1-100 keV) ionization signatures from electron and argon nuclear recoils to place new limits on dark matter [13][14][15][16]. While sub-MeV scale reconstruction techniques and tools are mature for dark matter LAr experiments using dual-phase LArTPC or scintillation detector technology, similar tools are in an early stage of development for single-phase LAr neutrino detectors relying primarily on charge readout technologies [17][18][19].…”

“…At the end of this decade, the ≈10 kT underground single-phase LArTPCs of the DUNE experiment will be sensitive to neutrinos produced in nearby supernovae [20], and may ultimately serve as a probe of solar neutrinos [21,22], neutrinoless double-β decay [23], and dark sector particle interactions [18,24]. Other impending or proposed future efforts also plan to realize multiton-scale LAr detectors, such as the LEGEND neutrino- * microboone info@fnal.gov less double-β decay detector [25] and the DarkSide-20k and Argo dark matter detectors [26,27].…”