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Abstract:

High-Pressure Gas Time Projection Chambers (HPgTPCs) have benefits such as low energy thresholds, magnetisability, and 4π acceptance, making them ideal for neutrino experiments such as DUNE. We present the design of an FPGA-based solution optimised for Gaseous Argon Near Detector (ND-GAr), which is part of the Phase-II more capable near detector for DUNE. These electronics reduce the cost significantly compared to using collider readout electronics, which are typically designed for much higher occupancy and therefore, for example, need much larger numbers of FPGAs and power per channel. We demonstrate the performance of our electronics with the Teststand for an Overpressurised Argon Detector (TOAD) at Fermilab in the US at a range of pressures and gas mixtures up to 4.5 barA, reading out ∼10 000 channels from a Multi-Wire Proportional Chamber (MWPC). The operation took place between April and July of 2024. We measure the noise characteristics of the system to be sufficiently low, and we identify sources of noise that can be further mitigated in the next iteration. We also note that the cooling scheme used in the test requires improvement before full-scale deployment. Despite these necessary improvements, we show that the system can fulfil the needs of a HPgTPC for a fraction of the price of collider readout electronics.

Abstract:

Bayesian analysis results require a choice of prior distribution. In long-baseline neutrino oscillation physics, the usual parameterisation of the mixing matrix induces a prior that privileges certain neutrino mass and flavour state symmetries. Here we study the effect of privileging alternate symmetries on the results of the T2K experiment. We find that constraints on the level of CP violation (as given by the Jarlskog invariant) are robust under the choices of prior considered in the analysis. On the other hand, the degree of octant preference for the atmospheric angle depends on which symmetry has been privileged.

Abstract:

New neutrino–nucleus interaction cross-section measurements are required to improve nuclear models sufficiently for future long baseline neutrino experiments to meet their sensitivity goals. A time projection chamber (TPC) filled with a high-pressure gas is a promising detector to characterise the neutrino sources used for such experiments. A gas-filled TPC is ideal for measuring low-energy particles, which travel further in gas than in solid or liquid detectors and using high-pressure increases the target density, resulting in more neutrino interactions. We examine the suitability of multiwire proportional chambers (MWPCs) from the ALICE TPC for use as the readout chambers of a high-pressure gas TPC. These chambers were previously operated at atmospheric pressure. We report the successful operation of an ALICE TPC outer readout chamber (OROC) at pressures up to 4.2 bar absolute (barA) with Ar-CH 4 mixtures with a CH 4 content between 2.8 and 5.0%, and so far up to 4 bar absolute with Ar-CO 2 (90-10). The charge gain of the OROC was measured with signals induced by an 55Fe source. The largest gain achieved at 4.2 bar was (29 ± 1) · 10 3 in Ar-CH 4 with 4.0% CH 4 with an anode voltage of 2975V . In Ar-CO 2 with 10% CO 2 at 4 barA, a gain of (4.2 ± 0.1) · 10 3 was observed with anode voltage 2975V . We extrapolate that at 10 barA, an interesting pressure for future neutrino experiments, a gain of 5000 in Ar-CO 2 with 10% CO 2 (10,000 in Ar-CH 4 with ∼4%CH 4) may be achieved with anode voltage of 4.6kV (∼3.6kV).