Argon Purification Studies and a Novel Liquid Argon Re-circulation System

Future giant liquid argon (LAr) time projection chambers (TPCs) require a purity of better than 0.1 parts per billion (ppb) to allow the ionised electrons to drift without significant capture by any electronegative impurities. We present a comprehensive study of the effects of electronegative impurity on gaseous and liquid argon scintillation light, an analysis of the efficacy of various purification chemicals, as well as the Liverpool LAr setup, which utilises a novel re-circulation purification system. Of the impurities tested - Air, O_2, H_2O, N_2 and CO_2 in the range of between 0.01 ppm to 1000 ppm - H_2O was found to have the most profound effect on gaseous argon scintillation light, and N_2 was found to have the least. Additionally, a correlation between the slow component decay time and the total energy deposited with 0.01 ppm - 100 ppm O_2 contamination levels in liquid argon has been established. The superiority of molecular sieves over anhydrous complexes at absorbing Ar gas, N_2 gas and H_2O vapour has been quantified using BET isotherm analysis. The efficiency of Cu and P_2O5 at removing O_2 and H_2O impurities from 1 bar N6 argon gas at both room temperature and -130 ^oC was investigated and found to be high. A novel, highly scalable LAr re-circulation system has been developed. The complete system, consisting of a motorised bellows pump operating in liquid and a purification cartridge, were designed and built in-house. The system was operated successfully over many days and achieved a re-circulation rate of 27 litres/hour and high purity

Neutrino Interactions In Oscillation Experiments

We calculate neutrino induced cross-sections relevant for oscillation experiments, including the $\tau$-lepton threshold for quasi-elastic, resonance and deep inelastic scattering. In addition to threshold effects, we include nuclear corrections for heavy targets which are moderate for quasi-elastic and large for single pion production. Nuclear effects for deep inelastic reactions are small. We present cross sections together with their nuclear corrections for various channels which are useful for interpreting the experimental results and for determining parameters of the neutrino sector..Comment: 24 pages, 18 figure

Reconstruction of interactions in the ProtoDUNE-SP detector with Pandora

The Pandora Software Development Kit and algorithm libraries provide pattern-recognition logic essential to the reconstruction of particle interactions in liquid argon time projection chamber detectors. Pandora is the primary event reconstruction software used at ProtoDUNE-SP, a prototype for the Deep Underground Neutrino Experiment far detector. ProtoDUNE-SP, located at CERN, is exposed to a charged-particle test beam. This paper gives an overview of the Pandora reconstruction algorithms and how they have been tailored for use at ProtoDUNE-SP. In complex events with numerous cosmic-ray and beam background particles, the simulated reconstruction and identification efficiency for triggered test-beam particles is above 80% for the majority of particle type and beam momentum combinations. Specifically, simulated 1 GeV/c charged pions and protons are correctly reconstructed and identified with efficiencies of 86.1±0.6% and 84.1±0.6%, respectively. The efficiencies measured for test-beam data are shown to be within 5% of those predicted by the simulation.ISSN:1434-6044ISSN:1434-605

Measurements of neutrino oscillation parameters from the T2K experiment using 3.6 × 10²¹ protons on target

The T2K experiment presents new measurements of neutrino oscillation parameters using 19.7(16.3)×10²⁰ protons on target (POT) in (anti-)neutrino mode at the far detector (FD). Compared to the previous analysis, an additional 4.7×10²⁰ POT neutrino data was collected at the FD. Significant improvements were made to the analysis methodology, with the near-detector analysis introducing new selections and using more than double the data. Additionally, this is the first T2K oscillation analysis to use NA61/SHINE data on a replica of the T2K target to tune the neutrino flux model, and the neutrino interaction model was improved to include new nuclear effects and calculations. Frequentist and Bayesian analyses are presented, including results on sin² θ₁₃ and the impact of priors on the δ_CP measurement. Both analyses prefer the normal mass ordering and upper octant of sin² θ₂₃ with a nearly maximally CP-violating phase. Assuming the normal ordering and using the constraint on sin² θ₁₃ from reactors, sin² θ₂₃ = 0.561⁺⁰.⁰²¹₋₀.₀₃₂ using Feldman–Cousins corrected intervals, and Δm²₃₂ = 2.494⁺⁰.⁰⁴¹₋₀.₀₅₈×10−3 eV² using constant Δχ² intervals. The CP-violating phase is constrained to δCP=−1.97⁺⁰.⁹⁷₋₀.₇₀ using Feldman–Cousins corrected intervals, and δ_CP = 0,π is excluded at more than 90% confidence level. A Jarlskog invariant of zero is excluded at more than 2σ credible level using a flat prior in δCP, and just below 2σ using a flat prior in sin δ_CP. When the external constraint on sin² θ₁₃ is removed, sin² θ₁₃ = 28.0+2.8−6.5×10−3, in agreement with measurements from reactor experiments. These results are consistent with previous T2K analyses.ISSN:1434-6044ISSN:1434-605

First measurement of muon neutrino charged-current interactions on hydrocarbon without pions in the final state using multiple detectors with correlated energy spectra at T2K

This paper reports the first measurement of muon neutrino charged-current interactions without pions in the final state using multiple detectors with correlated energy spectra at T2K. The data was collected on hydrocarbon targets using the off-axis T2K near detector (ND280) and the on-axis T2K near detector (INGRID) with neutrino energy spectra peaked at 0.6 GeV and 1.1 GeV, respectively. The correlated neutrino flux presents an opportunity to reduce the impact of the flux uncertainty and to study the energy dependence of neutrino interactions. The extracted double-differential cross sections are compared to several Monte Carlo neutrino-nucleus interaction event generators showing the agreement between both detectors individually and with the correlated result.ISSN:1550-7998ISSN:0556-2821ISSN:1550-236

Updated T2K measurements of muon neutrino and antineutrino disappearance using 3.6×10²¹ protons on target

Muon neutrino and antineutrino disappearance probabilities are identical in the standard three-flavor neutrino oscillation framework, but CPT violation and nonstandard interactions can violate this symmetry. In this work we report the measurements of sin²θ₂₃ and Δm²₃₂ independently for neutrinos and antineutrinos. The aforementioned symmetry violation would manifest as an inconsistency in the neutrino and antineutrino oscillation parameters. The analysis discussed here uses a total of 1.97 × 10²¹ and 1.63 × 10²¹ protons on target taken with a neutrino and antineutrino beam respectively, and benefits from improved flux and cross section models, new near-detector samples and more than double the data reducing the overall uncertainty of the result. No significant deviation is observed, consistent with the standard neutrino oscillation picture.ISSN:1550-7998ISSN:0556-2821ISSN:1550-236