Towards high-pressure noble gaseous detectors for coherent elastic neutrino-nucleus scattering

Abstract

Coherent elastic neutrino-nucleus scattering (CE$ν$NS) is a dominant low-energy neutrino interaction that remains experimentally challenging due to its weak-scale cross section and the small nuclear recoil energies involved. This thesis explores the scientific motivations and technical feasibility of CE$ν$NS\ detection, emphasizing the use of diverse neutrino sources -reactor, spallation, and solar- and multiple target materials. The European Spallation Source (ESS) is identified as a particularly promising site, with simulations indicating an optimal signal-to-background ratio achievable with minimal shielding at a location $\sim$24 meters from the tungsten target. Alternative facilities, such as JPARC-MFL, are also evaluated given construction delays at ESS. A significant contribution of this work is the development of a compact, low-cost, 4$π$ neutron scatter camera with integrated optical imaging, capable of characterizing neutron backgrounds and localizing sources using advanced discrimination algorithms and neural networks. Additionally, the thesis presents the design and early testing of GanESS, a novel high-pressure noble gas time projection chamber with electroluminescence amplification, optimized for CE$ν$NS detection using argon, xenon, or krypton. The Gaseous Prototype (GaP) demonstrates a promising energy threshold of 0.42$\pm$0.04 $\rm{keV}_{\rm{ee}}$ at 8.62 bar of argon and stable high-pressure performance. Detailed simulations using Garfield++ and COMSOL provide insights into electroluminescence behavior and threshold estimation, although some non-linear detector responses at low E/p remain unresolved. Overall, this work establishes a robust foundation for CE$ν$NS studies at spallation sources and advances detection technologies with broader implications for neutrino physics and rare-event searches.

Figures (75)

• Figure 1: Diagram of coherent elastic neutrino-nucleus scattering (CE$\nu$NS) in the SM. $\nu_\alpha$ here denotes any neutrino or anti-neutrino with flavor $\alpha=e,\,\mu,\,\text{or}\,\tau$, and $^A_Z\mathcal{N}$ a nucleus with $A$ nucleons. $Z^0$ is the neutral vector boson mediator in neutral-current interactions in the SM.
• Figure 2: Representation for $^{133}\text{Cs}$, $^{127}\text{I}$, $^{132}\text{Xe}$ and $^{40}\text{Ar}$ isotopes. Left: The nuclear form factor according to the Klein-Nystrand parametrization. Right: The CE$\nu$NS cross section for as a function of the incoming neutrino energy. Note the overlap between Cs, I and Xe as they have similar atomic numbers, and the smaller cross-section for Ar as it is a lighter nucleus.
• Figure 3: Flux-averaged cross section as a function of the neutron number for both spallation and reactor. Specific isotopes of conventional target materials for CE$\nu$NS are also marked. Klein-Nystrand parametrization is used for the nuclear form factor and setting this to unity will have a visible steeper deviation as the neutron number increases.
• Figure 4: Illustration of the total cross-section for several neutrino interactions present at spallation and reactor neutrino energy ranges. CE$\nu$NS cross-section with cesium and iodine (blue), charged-current (CC) interaction with iodine (green), inverse beta decay (red) and neutrino-electron scattering (dotted red) are shown. CE$\nu$NS dominates over any charged-current interaction for incoming neutrino energies of less than 55 MeV. Plot extracted from scholz2018first.
• Figure 5: Extracted from Coloma2022. The analysis of COHERENT CsI and Ar data, the Dresden-II reactor data (Fef and YBe quenching factor in the respective panels) and their combination for 90$\%$ CL allowed regions on flavor diagonal NSI with up-quarks (for zero values of all other NSI coefficients). Note that, in the two-dimensional panels, the results are obtained for 2 dof ($\Delta \chi^2 = 4.61$) except for the Dresden-II reactor experiment data which is obtained for 1 dof ($\Delta \chi^2 = 2.71$).