The DUNE Vertical Drift detector and its potential to measure the leptonic CP-violating phase with sub-GeV atmospheric neutrinos



The Deep Underground Neutrino Experiment (DUNE) [a,b] is a next-generation neutrino oscillation experiment to measure unknown parameters of the Standard Model of particle physics and to search for new phenomena.  A high power wide-band beam operating in neutrino or anti-neutrino mode will be produced at Fermilab, the flux and flavour composition will be characterised with the Near Detector. At a baseline of 1,300 km, deep underground at the Sanford Underground Research Facility (SURF, South Dakota), four gigantic Far Detector modules will measure the three neutrino flavours with the goals of determining the Neutrino Mass Ordering, determining the charge-parity (CP) Violation phase, measuring precisely the oscillation parameters and testing the 3-flavour paradigm.

The DUNE Far Detector modules will be liquid Argon Time Projection Chambers (LAr-TPCs) each with a fiducial mass of 10 ktons. With huge detectors deep underground, DUNE will be able to search for physics beyond the Standard Model and to observe also neutrinos from astrophysical sources. 

Liquid Argon is an ideal target for neutrinos, thanks to its high density, good scintillation and ionization yields, and transparency to its own scintillation light. The TPC technology combines fine-grained tracking with total absorption calorimetry to provide mm-scale resolution in 3D for all charged particles, excellent energy resolution and particle identification capabilities. The French groups in DUNE are heavily involved in the development of the Vertical Drift [c] (VD) LAr-TPC envisaged for the second Far Detector module. This novel design attempts to reduce the overall cost and the construction difficulties related to LArTPC detectors, while keeping the same performance. In order to demonstrate its suitability to achieve the DUNE physics goals, including their long-term performance and stability, the ProtoDUNE detectors are being operated at the CERN Neutrino Platform, near Geneva. A full-scale prototype with a fiducial volume of 6x6x6 m3, ProtoDUNE-VD or "Module 0", is currently being constructed: it is expected to be operational as of summer 2023 and to be exposed to cosmic rays for a few months.  It will provide the first full-scale validation of the VD technology. As a first stage, the charge signal needs to be understood and exploited at different levels of the analysis chain. Special efforts must be devoted to the analysis of the light signal, validating the photon detection system readout developed at APC. During the first year of the PhD, the candidate will actively participate in the operation of the detector at CERN and the analysis of the collected data. The main goals are 

- understanding the response of the detector, both to the ionisation and to the scintillation signal;

- assessing the performance of the Vertical Drift module in view of the physics goals of DUNE; 

- validating the MonteCarlo simulations that will be used for the Far Detector studies.

The first two DUNE Far Detector modules are expected to be completed in 2029. Before the neutrino beam becomes operational, the DUNE detectors will be exposed to atmospheric neutrinos for several months. The analysis of the first data will not only allow to assess the detector performance, but also to provide measurements of the neutrino oscillation parameters. Most of the studies so far have focused on the potential to measure the neutrino Mass Ordering and the θ23 mixing angle using GeV atmospheric neutrinos. The unique reconstruction capabilities of DUNE, and in particular the detection of the low-energy recoil proton, will also allow to study sub-GeV atmospheric neutrinos, which can provide a determination of the leptonic CP-violating phase independent of the accelerator neutrino measurement [d]. Moreover, the determination of the sub-GeV atmospheric neutrino flux will have important consequences in the detection of diffuse supernova neutrinos and in dark matter experiments. The focus of the thesis will be on the potential of the DUNE detectors to study sub-GeV atmospheric neutrinos, including:

- development of dedicated event reconstruction algorithms, based either on conventional techniques or on machine learning, and assessment of their performance;

- full-simulation studies of the sensitivity to the leptonic CP-violating phase;

- complete assessment of the physics potential of sub-GeV atmospheric neutrinos and their complementarity with other measurements.

The DUNE Science Collaboration is currently made up of over 1400 collaborators from over 200 institutions in over 30 countries plus CERN. The DUNE group at the APC Laboratory is composed of 6 permanent members, 2 post-docs and 3 PhD candidates.

An international co-supervision (cotutelle) with Italy can be envisaged, in the context of the tight collaboration with the group of Milano Bicocca University on the development of the Photon Detection System.


b)   DUNE Collaboration, Far detector Technical Design Report. Vol. I: Introduction to DUNE, JINST 15 (2020) 08, T08008; Vol. II: DUNE Physics, arXiv:2002.03005
c)    S. Sacerdoti for the DUNE Collaboration, A LArTPC with Vertical Drift for the DUNE Far Detector, PoS NuFact2021 (2022) 173
d)   K. J. Kelly, P. A. N. Machado, I. Martinez-Soler, S. J. Parke, Y. F. Perez-Gonzalez, Sub-GeV Atmospheric Neutrinos and CP-Violation in DUNE, Phys. Rev. Lett. 123, 081801 (2019)

Contact (Alessandra Tonazzo) 



Alessandra Tonazzo






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