The Deep Underground Neutrino Experiment (DUNE) is an upcoming international neutrino experiment, hosted in the U.S., and combining the efforts of more than 1400 scientists and engineers from more than 200 institutions across the globe. The experiment is conceived primarily as a neutrino oscillation experiment with the goal of completing our knowledge on this phenomenon particularly by determining the neutrino mass ordering, measuring the Charge-Partity violating phase (if non-zero), improving the precision on the oscillation parameters and testing the 3-flavour paradigm. To do this, the world’s most intense neutrino beam is being constructed at FNAL (Fermilab), and 1,300 km away, deep underground at the Sandford Underground Research Facility (South Dakota), four gigantic Far Detector modules are planned. These Far Detector modules are Liquid Argon Time-Projection Chambers (LArTPC), each containing 17-ktons of liquid argon. With colossal well-shielded detectors, DUNE is able to widen its physics scope and study neutrinos from sources other than the beam. Of interest to DUNE and the APC team is the ability to study atmospheric neutrinos, which are produced high in the Earth’s atmosphere, traverse the planet and can interact within DUNE’s Far Detectors. The atmospheric sample spans a wide range of energies, encompassing that of DUNE’s beam (~0.8 - 10 GeV), and can also be used to study neutrino oscillations, offering sensitivity to the neutrino mass ordering and mixing angle θ23. It has also been shown that the neutrinos of energies <1GeV (sub-GeV) offer sensitivity to the CP violating phase [1].
DUNE’s Far Detectors are cutting-edge instruments, the largest LArTPCs ever conceived. The experiment has an ambitious prototyping effort to prove the ever-advancing technology at large-scale which is hosted at the CERN Neutrino Platform. Two ~kton detectors, known as the protoDUNEs, have been built, and so far have tested three different read-out technologies. Two technologies have been retained and will be used for the first two Far Detector modules, the first is a wire-based read-out known as Horizontal Drift and the second is PCB-based known as Vertical Drift.
Neutrinos are detected via their interactions with Argon nuclei within the LArTPC. These interactions release energetic charged particles which ionise and excite the liquid argon media. The electrons are drifted, by an applied electric field, towards and induce signals on three read-out planes orientated at different angles. LArTPCs can produce fine grained 3D images of neutrino events which can span several metres. Large quantities of data are produced by these instruments which require multiple layers of processing before obtaining the physical relevant variables of interest. Typically Machine Learning methods are exploited to obtain the best performance.
At CERN, the protoDUNE LArTPCs are characterised with charged particle beams which allows to study individually the response of the detector to these charged particles such as: electrons, muon, protons, pions etc. However, in these test beams only very few neutrinos can be collected there.
This PhD is funded through a UChicago-CNRS project called 'Exploiting Liquid Argon Instruments for sub-GeV Neutrinos' (ELAIN) which unites the DUNE team at APC with a team at UChicago working on the Short Baseline Near Detector (SBND) at FNAL. SBND is a LArTPC similar in design to DUNE’s Horizontal Drift, located 110m from the target of the Booster Neutrino Beam and records more than 1 million neutrino events per year. The project aims to use data from real neutrino interactions in SBND and use them to study DUNE’s performance to sub-GeV atmospheric neutrinos. As part of this effort, the proposed thesis will focus on event reconstruction in DUNE, working closely with the team at UChicago.
The work will entail:
- studying existing reconstruction methods in DUNE, using both simulation and existing charged-particle beam data from the protoDUNEs.
- comparing the performance obtained with single-track events in the protoDUNE detectors and SBND
- study neutrino event reconstruction using DUNE's Far Detector simulation. Compare DUNE's expected performance to low energy neutrino interactions with SBND.
- Estimate systematic uncertainties related to the reconstruction, in particular those most impacting the determination of the oscillation parameters with the atmospheric sample.
Regular remote meetings between the APC and UChicago team will be held, as well as in-person meetings held in Paris, CERN and annual visits to Chicago.
[1] Kevin J. Kelly, Pedro A. N. Machado, Ivan Martinez-Soler, Stephen J. Parke, Yuber F. Perez-Gonzalez, Phys. Rev. Lett. 123, 081801 (2019)