Session Z08: New Techniques in Neutrino Physics II

Hunting for High Energy Astrophysical Tau Neutrinos

IceCube's discovery of astrophysical neutrinos, and subsequent characterization of their energy spectrum up to a few PeV, has provided a new window into the high-energy Universe. However, many opportunities for discovery remain; low sample sizes still plague measurements of astrophysical neutrinos above 1PeV, and flavor measurements are challenging due to the difficulty in differentiating tau events from other flavors. A series of next-generation experiments aim to provide a novel aperture into the under-explored component of the high-energy neutrino spectrum. Among them is TAMBO (Tau Air-Shower Mountain-Based Observatory), a proposed water-Cherenkov detector set on a cliff-edge in the high Peruvian Andes. Utilizing the unique geometry of the Colca valley, TAMBO is situated to produce a high-purity sample of 1–100 PeV astrophysical tau neutrino events. This talk will discuss recent progress and highlight the prospects and challenges of astrophysical tau neutrino detection in the next generation of neutrino experiments.   

Reconstructing GeV-scale Neutrinos in IceCube using CNNs

The IceCube Neutrino Observatory instruments 5,160 digital optical modules, which are arrayed over a cubic kilometer deep within the South Pole ice. In the lower center, the modules are more densely configured, which are called the DeepCore subdetector, extending the observable energy threshold down to GeV-scale, where atmospheric neutrino oscillations can be studied. Reconstructing events in the detector is essential in neutrino oscillation analysis. In this talk, I will present the reconstructions of direction, energy, vertex, and particle identifications of GeV-scale events in IceCube by using convolutional neural networks and compare the results to those of the current likelihood-based reconstruction algorithm.   

Measurement of Atmospheric Neutrino Oscillation on IceCube using Convolutional Neural Network Reconstructions

The IceCube Neutrino Observatory, instrumenting a cubic kilometer of Antarctic ice, is sensitive to both astrophysical and atmospheric neutrinos. IceCube’s DeepCore subarray extends the detected energy down to GeV scales, providing additional resolution for neutrino oscillation to be observed. Neutrino oscillation is dependent on the distance the neutrino travels (L) and the energy of the neutrino (E). IceCube allows us to probe oscillations in unique ranges of L and E using 8 years of atmospheric neutrinos that travel distances through the earth at the 10 GeV-scale. Typical oscillation analyses on IceCube data use likelihood-based reconstruction methods to determine the incident neutrino’s energy, direction of travel, and interaction vertex. We have recently developed a convolutional neural network (CNN) to replace all likelihood-based reconstructed variables. This talk explores the sensitivity to the muon neutrino disappearance measurement in IceCube using a convolutional neural network reconstruction of the neutrino interactions.   

Tau Appearance from High-Energy Neutrino Interactions

High-energy muon- and electron-neutrinos yield a non-negligible flux of tau neutrinos as they propagate through Earth. In this talk, we address the impact of this additional component in the PeV and EeV energy regimes for the first time. This contribution is predicted to be significantly larger than the atmospheric background above 300 TeV, and alters current and future neutrino telescopes' capabilities to discover a cosmic tau-neutrino flux. Further we demonstrate that Earthskimming neutrino experiments, designed to observe tau neutrinos, will be sensitive to cosmogenic neutrinos even in extreme scenarios without a primary tau-neutrino component.   

Measuring the rate of electron antineutrino charged-current interactions in the NOvA near detector with NuMI neutrino- and antineutrino-mode data

The NOvA near detector (ND) is exposed to a large flux of (anti)neutrinos delivered by the NuMI beam when operating in (anti)neutrino mode. While most of the beam is composed of muon (anti)neutrinos, a small electron (anti)neutrino component is incident at the ND originating from the decay of muons, kaons, and pions resulting from the initial proton collision. The charged-current inclusive interaction rate of these intrinsic electron neutrinos in the NOvA detector has been recently measured with a sample of data observed during neutrino-mode run periods of NuMI. We now aim to measure the charged-current inclusive interaction rate of electron antineutrinos with data from NuMI antineutrino run periods.

 

A significant challenge of this measurement comes from the relatively large electron neutrino background due to similar topologies and its large cross section compared to the electron antineutrino. We present a data-driven template fit approach to signal estimation and a simultaneous fit to neutrino and antineutrino beam-mode data to constrain the electron neutrino background. This approach enables the measurement of the charged-current inclusive interaction rate of the electron antineutrino, and the ratio of measured electron neutrino and antineutrino interaction rates.   

Studies of tau neutrino appearance at the DUNE Near Detector complex

The DUNE experiment will use the new LBNF (Long-Baseline Neutrino Facility) neutrino beam sampled at the Near Detector complex (DUNE ND), 574 m downstream of the production target, and at the Far Detector complex, 1300 km away at the SURF laboratory at a depth of about 1.5 km. The highly-capable multi-component Near Detector complex, with a LArTPC (Liquid Argon Time Projection Chamber) as its primary detector, enables DUNE to probe new physics beyond the Standard Model, including the possibility of short-baseline tau neutrino appearance mediated by sterile neutrino oscillations. Tau neutrino detection is particularly challenging due to the high energy production threshold of the tau lepton and its very short lifetime. However, the excellent spatial resolution of the Near Detector LArTPC and the large statistics expected (particularly using the high-energy beam configuration) for the LBNF beam provide a unique opportunity to probe these exotic signatures. In this talk, I will review the tau neutrino selection strategy using the DUNE ND complex and present the DUNE's expected sensitivities to short-baseline tau neutrino appearance using the ND LArTPC combined with the proposed magnetized muon spectrometer (ND GAr-Lite).   

Latest Results and Status of CEvNS on LAr from the COHERENT Collaboration

Coherent Elastic Neutrino-Nucleus Scattering(CEvNS), first observed by the COHERENT Collaboration in 2017, is a neutral-current neutrino process. For neutrino energies below 100 MeV, it is the dominant cross-section. A precise measurement of the CEvNS cross-section will test new physics including constraints on nonstandard neutrino-quark interactions, the weak nuclear radius, and the particle nature of dark matter. In addition, development of CEvNS-sensitive technologies is useful for low-threshold WIMP dark matter searches and for sterile neutrino searches.

In order to obtain a precision measurement of the CEvNS cross-section, the COHERENT Collaboration has deployed a number of detectors with a range of target nuclei to the Spallation Neutron Source at Oak Ridge National Laboratory(ORNL). These include a 24-kg single-phase liquid argon detector, COH-Ar-10, which made the first low-N measurement of CEvNS in spring 2020. Using lessons learned from the previous result, we detail here an improved and expanded analysis over a larger data set. Further, we will touch on development of the ton-scale upgrade, COH-Ar-750.   

Far forward tau neutrinos at the LHC: parton distribution function uncertainties in theoretical predictions

Tau neutrinos and antineutrinos, predominately from $D_s^\pm$ production and decay, are produced in the far-forward region at the Large Hadron Collider (LHC). Two experiments, FASER$\nu$ and SND@LHC, will take data during Run 3, and proposed experiments for a Forward Physics Facility would operate during the high luminosity era. These experiments will measure neutrino pseudorapidities in the range of $\eta>6.9$ and higher, where both very small and large parton-$x$ values in the parton distribution functions (PDF) are important in theoretical predictions. We show the sensitivity of a next-to-leading order (NLO) QCD evaluation of $D_s^\pm$ production, followed by decay to tau neutrinos on the 40 PDF sets of the PROSA19 group, on QCD scale uncertainties and on regions of $x$ in the PDF. We compare results with other 3-flavor NLO PDF sets of the CT14, ABMP16 and NNPDF3.1 collaborations. The Forward Physics Facility in the high luminosity LHC era will  provide data capable of constraining NLO QCD evaluations with these PDF sets.   

Dark matter decay to neutrinos

Dark matter (DM) particles are predicted to decay into Standard Model particles, which would produce signals of neutrinos, gamma-rays, and other secondary particles. Neutrinos provide an avenue to probe astrophysical sources of DM particles. We review the decay of dark matter into neutrinos over a range of dark matter masses from MeV/c^2 to ZeV/c^2. We examine the expected contributions to the neutrino flux at current and upcoming neutrino and gamma-ray experiments, such as Hyper-Kamiokande, DUNE, CTA, TAMBO, and IceCube Gen-2. We consider galactic and extragalactic signals of decay processes into neutrino pairs, yielding constraints on the dark matter decay lifetime that ranges from tau ∼ 1.2×10^21 s at 10 MeV/c^2 to 1.5x10^29 s at 1 PeV/c^2.