DUNE at Sheffield

Background

As a long baseline neutrino experiment, DUNE has three principal components: a beamline, a near detector, and a far detector. The far detector will be located at the Sanford Underground Research Facility (SURF)—better known to neutrino physicists as the Homestake Mine, former home of the original Davis solar neutrino experiment.

The dark matter experiment LZ, in which the Sheffield Dark Matter group is participating, is also housed at SURF. The near detector and neutrino beamline are at Fermilab, giving a baseline of 1300 km from the target to the far detector. 

DUNE has similar physics goals to Hyper-Kamiokande but uses a completely different strategy to achieve them. As a result, the DUNE and Hyper-Kamiokande projects are highly complementary: the combination of the two will be much more effective than either one alone

The main physics goals of DUNE include:

• Measuring the magnitude of the CP-violating phase in the PMNS matrix by looking at the difference in oscillatory behaviour between neutrinos and antineutrinos.
• Precision measurements of other neutrino mixing parameters, θ₂₃, θ₁₃, Δm²₁₃ and Δm²₂₃.
• Determining the mass-ordering of the active neutrinos by measuring the sign of Δm²₁₃.
• Determining the octant of θ₂₃.
• Searches for proton decay, supernova neutrinos, and solar neutrino measurements.

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DUNE

Unlike T2K and Hyper-K, DUNE is an on-axis experiment. It therefore sees a broad range of neutrino energies, peaking between 1 and 5 GeV, as opposed to Hyper-K's relatively narrow energy range peaking around 600 MeV.

However, the key variable for neutrino oscillation experiments is the ratio of baseline length to the neutrino energy, L/E: Hyper-K has an L/E value of 500 km/GeV, and DUNE's range of ~260–1300 km/GeV covers this value, showing that both are optimised for the same squared mass difference Δm²₁₃.

The choice of an on-axis geometry has advantages and disadvantages: the absolute sensitivity to oscillation is reduced, because a smaller fraction of the beam is at the L/E value corresponding to peak oscillation probability (this is why T2K and NOνA, designed when we had only an upper limit to the value of the mixing angle θ₁₃, both chose an off-axis geometry), but the ability to observe the oscillation over a range of L/E values helps to distinguish between different phenomena, e.g. the effects of CP violation and those of matter-enhanced oscillation. It does mean that accurate reconstruction of the neutrino energy is crucial to realising the physics potential of the experiment.

The DUNE far detector will consist of four independent modules, with at least one being an LArTPC (link to LArTPC page) containing about 17 kilotons of liquid argon. The modules will likely contain a mixture of horizontal drift (HD), as used in all the large-scale LArTPCs that have been built to date, and vertical drift modules (a new technology currently being explored by DUNE scientists). One major component of the DUNE HD LArTPC design and construction process to which Sheffield contributes is the Anode Plane Assembly (APA), a rectangular (7m by 2m) multi-wire charge plane readout technology which will be implemented in at least one of the four far detectors of the Deep Underground Neutrino Experiment (DUNE).

The technologies to be used in DUNE are tested at CERN, by the ProtoDUNE project. The technology for the first module (horizontal drift) was successfully tested at 1/20th scale in 2019 - and even that was the largest LArTPC ever operated at the time! Prototyping like this allows physicists to identify areas for improvement, both in the design used and in the software used to consider the results. Further testing of the horizontal drift technology and initial testing of the vertical drift technology will be conducted by the ProtoDUNE-II project at the CERN neutrino platform towards the end of 2024.

The DUNE near detector will be located only 574 m downstream of the neutrino source. It will be a physics experiment in its own right, consisting of a number of different components including a modular LArTPC, a gaseous argon TPC, and a large beam monitor module. It will also be capable of taking data at different off-axis beam positions. This allows it to be extremely useful in minimising uncertainties from the near-to-far flux difference.

Groundbreaking for the far detector happened in 2017, and the work is currently ongoing (as of March 2024) to fit the resulting caverns with all the necessary equipment to operate the huge experiment that will move in soon. The first detector is hoped to be operational before the end of 2028.

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DUNE at Sheffield

Sheffield has participated in a range of different activities over the course of the DUNE experiment so far, including being part of the ProtoDUNE Single-Phase project. The group previously had a significant focus on the 35-ton prototype, a predecessor to the ProtoDUNE project used to field test new features for the DUNE far detector. It has also been part of the physics analysis teams, studying proton decays and supernova neutrinos.

Currently (as of March 2024) Sheffield is focussing its efforts on natural-source calibration developments for the DUNE Far Detectors and the ProtoDUNE-II detectors, with Rhiannon Jones as a co-convener of the physics-calibration working group. The primary cosmic-ray particle generator used in DUNE simulations is the Muon Simulations Underground package (MUSUN), first developed by Sheffield’s own Vitaly Kudryavtsev. MUSUN utilises inputs from the Muon Simulation Code (MUSIC) package, which simulates muon transport through matter, also developed at the University of Sheffield. 

The Sheffield group also played a leading role in the development and design of each of the 29 DUNE APA printed circuit board (PCB) types. In total, 204 geometry PCBs are required to build an APA and 150 APAs are needed to construct the DUNE far detector.

The required 30,600 PCBs are produced by a UK-based world-leading PCB manufacturer. After production, the PCBs are tested, labelled and washed/baked and those determined to be within the required DUNE APA specifications are then shipped to institutions including the University of Sheffield for assembly. At Sheffield, wire pitch tooth strips are attached to the APA boards. After the board assembly processes, dimension and electrical contact connectivity quality control checks are performed before the boards are shipped to the Daresbury APA winding factory.

Below is a photo of a DUNE APA under construction at the Daresbury APA factory. Anthony Ezeribe, a member of our group is the current Technical Lead and work package Manager for the DUNE APA PCB work package. Prof. Vitaly Kudryavtsev, another member of the Sheffield group serves as the Academic Lead for the DUNE APA PCB work package. The first set of ProtoDUNE-I (a DUNE test stand at CERN) APA frames were developed by Sheffield Engineers led by Trevor Gamble. These earlier ProtoDUNE APA development works formed the basis of the current final DUNE far detector APA frame design.

The Sheffield group have also been involved in background studies for nucleon decay searches in DUNE, including leadership roles, and contributed in this capacity to the DUNE physics volumes of the conceptual, interim and technical design reports (CDR, IDR, TDR respectively). Between 2019 and 2022, members of the University of Sheffield DUNE group collaborated with academics from Universiti Malaya and Universiti Kebangsaan Malaysia on the development of cosmic-ray simulations for nucleon decay background studies.

The current DUNE group at Sheffield consists of Vitaly Kudryavtsev, Rhiannon Jones, Anthony Ezeribe and Alexandra Moor.