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... energy spectra mentioned in Sec. 3.1.1, the radial distribution, and the so-called pulse shape variable distribution, a parameter tuned to distinguish electron and positron events. It is used to disentange the 11 C e + decays originating from the remaining 11 C in the TFC-subtracted spectrum. Examples of the distributions and fits are shown in Fig. ...
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... Solar neutrinos, generated in the Sun's core via fusion reactions, produce a particle flux of approximately 7×10 10 s −1 cm −2 at Earth. The majority originate from the proton-proton chain and exhibit characteristic energy spectra extending to several MeV [41]. While predominantly traversing LXe detectors without interaction, a subset induce NRs through coherent elastic neutrino-nucleus scattering (CEνNS), mimicking WIMP signals. ...
The XENONnT experiment has achieved an unprecedented reduction of the Rn activity concentration within its liquid xenon dual-phase time projection chamber to a level of (0.900.01stat.0.07 sys.)Bq/kg, equivalent to about 1200 Rn atoms per cubic meter of liquid xenon. This represents a 15-fold improvement over the Rn levels encountered during XENON1T's main science runs and is a factor five lower compared to other currently operational multi-tonne liquid xenon detectors engaged in dark matter searches. This breakthrough enables the pursuit of various rare event searches that lie beyond the confines of the standard model of particle physics, with world-leading sensitivity. The ultra-low Rn levels have diminished the radon-induced background rate in the detector to a point where it is for the first time lower than the solar neutrino-induced background, which is poised to become the primary irreducible background in liquid xenon-based detectors.
... For CsI data from COHERENT experiment, only the Fef quenching model is employed. In order to include the time information of the CsI data of COHERENT, we calculate the theoretical event number N pred We also include constraints from other experiments including SN1987A [3], TEXONO [45], LSND [3], Atomspheric ν (Super-K) [10] which looks for atomspheric neutrino upscattering to N with subsequent N → νγ decay, Borexino [8,46], Solar N → νγ (Borexino and Super-K) [9] for solar neutrino upscattering to N with subsequent N decays, MiniBooNE [3,7,47], Charm-II [7,48] and IceCube [12] for comparison. All limits are for the one flavor transitional magnetic moment, except for the SN case where flavor universal couplings are used. ...
... As a result, our limits for the COHERENT experiment improve over previous ones [17,18] significantly, by roughly one order of magnitude. Though in the mass range lower than 1 MeV, the constraint from COHERENT CsI data is not as good as the results from solar neutrino EνES observation at Borexino [8,46], it provides better constraints for higher masses. We also show the constraints from accelerator experiments including MiniBooNE [3,7,47] and Charm-II [7,48] and the non-observation of atmospheric neutrino upscattering to N with subsequent N decays at Super-K for µ flavor (cyan shaded region) [10]. ...
Sterile neutrinos that couple to the Standard Model via the neutrino magnetic dipole portals have been extensively studied at various experiments. In this work, we scrutinize these interactions for sterile neutrinos in the mass range of \unit[0.1]{}-\unit[50]{MeV} through the nuclear and electron recoils at various neutrino scattering experiments. For the e-flavor specific dipole portal, we demonstrate that Dresden-II can provide leading constraints for m_N \lesssim \unit[0.5]{MeV}, setting aside currently unresolved theoretical uncertainties. For the -flavor case, we show that the COHERENT experiment can probe a unique parameter region for in the range of \unit[10]{}-\unit[40]{MeV} with the full dataset collected by the CsI[Na] scintillation detector, including both the energy and timing structure of the neutrino beam. We also present limits on the parameter regions of the -flavor dipole portal using measurements of the solar neutrino flux from dark matter direct detection experiments.
... However, for a CENNS precision measurement experiment, the Sun is clearly not a relevant source because even if the energy of some neutrinos is low enough for 8 Chapter 1. Measurement of the CENNS with Cryogenic Bolometers in the RICOCHET experiment On the left, simulated spectra of solar neutrinos seen from the Earth associated with the different fusion reactions, taken from [25]. On the right, solar neutrino spectrum and its components measured by the Borexino experiment at the Gran Sasso in Italy, taken from [49]. ...
The Coherent Elastic Neutrino-Nucleus Scattering (CENNS) is a process predicted nearly 40 years ago. In August 2017, the COHERENT experiment reported the first keV-scale detection at the 6.7 sigma level of this process, which is a probe for the new low energy physics, opening a window on a myriad of new physics opportunities. The RICOCHET experiment aims at measuring with high accuracy the CENNS process in order to probe various exotic physics scenarios in the electroweak sector. Using cryogenic bolometers operated in a cryostat 8 meters away from the core of the ILL research nuclear reactor, the experiment will benefit from an intense neutrino flux, allowing the results of COHERENT to be reproduced in a single week. The objective of an accurate measurement will be achieved after one year of data collection, by 2024. The CRYOCUBE is a compact cubic array of cryogenic detectors with the following specifications: a very low energy threshold of O(10) eV on the thermal signal, an electromagnetic background rejection of at least 10^3 and a total target mass of 1 kg distributed among 27 germanium crystals of about 30 g each. The objective of this thesis is to propose an optimized detector design for the CRYOCUBE, inspired by the cryogenic germanium detectors equipped with charge and temperature readings of the direct dark matter search experiment EDELWEISS. This joint R&D program is based on event discrimination realized in germanium semiconductor crystals. The recoil energy of an incident particle is derived either from the increase of the crystal temperature measured by a GeNTD thermistor (heat channel) or from the excited electric charges collected by electrodes on its surface (ionization channel). This double energy measurement makes it possible to distinguish the nuclear recoils produced by the CENNS or the dark matter from the electronic radioactive background. As these recoils are of the order of O(100) eV, this thesis work is focused on the development of a new generation of cryogenic low threshold germanium detectors with particle identification. It explores how to improve the resolution in heat and ionization energy up to O(10) eV while maintaining a good rejection of background events. This study is based on the testing of prototype detectors in the IP2I cryostat, which are compared to theoretical predictions from electro-thermal and electrostatic modeling of the detectors. This manuscript begins with the definition of the CENNS process, its scientific importance and the objectives of the RICOCHET experiment. It then presents the cryogenic installation allowing the surface operation of the detectors at 20 mK in optimal conditions. An electro-thermal model of the bolometers, compared with experimental data, is developed and applied to the simulation of the noise associated with the electronics of the heat signal. The thesis then formalizes the generation of the ionization signals arising from excited charge carriers drifting in the germanium crystal under the influence of the applied electric field. The expected resolution from a future low-noise electronics is modeled based on two detector designs. They are optimized by their electrostatic simulation in a finite element calculation software. A comparison of the theoretical and experimental performance of ionization is performed on the basis of the RED80 and REDN1 prototype detectors. This work ends with the characterization of the radioactive background in the cryogenic laboratory with the analysis of the data from RED80, and in particular its neutron component, used to estimate the expected background at the ILL site for RICOCHET
Over the past five decades, solar neutrino research has been pivotal in driving significant scientific advancements, enriching our comprehension of both neutrino characteristics and solar processes. Despite numerous experiments dedicated to solar neutrino detection, a segment of the lower pp spectrum remains unexplored, while the precision of measurements from the CNO cycle remains insufficient to resolve the solar abundance problem determined by the discrepancy between the data gathered from helioseismology and the forecasts generated by stellar interior models for the Sun. The CYGNO/INITIUM experiment aims to deploy a large 30 m3 directional detector for rare event searches focusing on Dark Matter. Recently, in the CYGNUS collaboration, there has been consideration for employing these time projection chamber technology in solar neutrino directional detection trough neutrino-electron elastic scattering. This is due to their potential to conduct low-threshold, high-precision measurements with spectroscopic neutrino energy reconstruction on an event-by-event basis driven by the kinematic. However, so far, no experiments have been investigated on the feasibility of this measurement using actual detector performances and background levels. Such a detector already with a volume of O(10) m3 could perform an observation of solar neutrino from the pp chain with an unprecedented low threshold, while with larger volumes it could measure the CNO cycle eventually solving the solar metallicity problem.
