Study of Reconstructed 39Ar Beta Decays at the MicroBooNE Detector

Liquid Argon Time Projection Chambers (LArTPCs) are imaging detectors that can be used to reconstruct the energies of particles and their trajectories with fine-grained resolution. One open question regarding large LArTPCs is their capability of measuring low-energy, point-like charge depositions such as those associated with interactions of low-energy supernova burst neutrinos within the detector. Given their point-like nature and low energies, naturally occurring 39Ar beta decays in LArTPCs provide a powerful resource in probing energy scales relevant for the reconstruction of supernova burst neutrinos and solar neutrinos at future large-scale LArTPC experiments such as DUNE (Deep Underground Neutrino Experiment). We present the first study of reconstructed 39Ar beta decays in a large LArTPC with data from MicroBooNE, a large (85-ton active mass) LArTPC neutrino experiment operating near the surface at Fermilab in Batavia, Illinois. The use of 39Ar beta decays as a potential calibration source in large LArTPC detectors is also discussed in detail.