arXiv subjects

L. Scola

Publications and source records attributed to L. Scola.

At least 19 recordsLinked to original sources

arXiv2026

Development and Commissioning of the Cryogenic Target Detectors for the Technical Run of the NUCLEUS Experiment

The NUCLEUS experiment aims to study coherent elastic neutrino-nucleus scattering (CE$\nu$NS) of reactor electron antineutrinos at the Chooz nuclear power plant in France. In this work, the cryogenic target-detector module for the NUCLEUS Technical Run was developed and commissioned at the Technical University of Munich. The module comprises four gram-scale CaWO$_4$ detectors, each equipped with two Transition Edge Sensors (TES), providing a total target mass of 6.96 g. We present the design, integration, detector characterization, and X-ray-based energy calibration of these detectors. Across six characterized detectors, a mean baseline resolution of $\overline{\sigma}_{\mathrm{BL}} = (2.79 \pm 0.60)\,\mathrm{eV}$ was achieved. The best-performing detector reached $\sigma_{\mathrm{BL}} = (2.16 \pm 0.02_{\mathrm{stat}})\,\mathrm{eV}$, surpassing the design goal by a factor of two and representing a state-of-the-art result for a cryogenic CaWO$_4$ detector. The target detector module was successfully operated simultaneously with the surrounding Cryogenic Outer Veto, which consists of six kg-scale Ge detectors for background discrimination, showing no measurable cross-talk. These results demonstrate the readiness of the target-detector system for the NUCLEUS Technical Run at Chooz and mark a key milestone in the development of cryogenic detectors for reactor-CE$\nu$NS measurements.

physics.ins-det↗

arXiv2026

Sensitivity enhancement techniques for cryogenic calorimeters in the NUCLEUS experiment

Phonon-mediated cryogenic calorimeters find application in rare event searches due to their intrinsically low energy threshold. Achieving the best sensitivity for this kind of detectors is crucial for signal identification, leading to various optimization techniques. In this work, we present two complementary methods to increase the sensitivity of cryogenic detectors read out by transition-edge sensors, developed and tested in the context of the NUCLEUS experiment. The first procedure maps the signal-to-noise ratio of the device across a wide range of operating points, to identify the configuration with maximal sensitivity to be used during data taking. The second method exploits the double readout of the detector, combining the information on different channels with a two-dimensional optimum filter analysis that effectively lowers the energy threshold. With both techniques at the same time, we obtained a baseline resolution of 2.94 $\pm$ 0.05 (stat) eV using a CaWO4 based detector, achieving a promising result in view of the first run of NUCLEUS at the experimental site.

physics.ins-det↗

arXiv2026

Prospect of the NUCLEUS Experiment at Chooz for Coherent Elastic Neutrino-Nucleus Scattering and New Physics Searches

The NUCLEUS experiment aims to measure coherent elastic neutrino-nucleus scattering (CE$\nu$NS) at unprecedentedly low nuclear recoil energies using gram-scale cryogenic calorimeters operated at the Chooz nuclear power plant in France. Access to recoil energies at the $\mathcal{O}(10~\mathrm{eV})$ scale enables CE$\nu$NS studies at extremely low momentum transfer and provides enhanced sensitivity to new physics. In this work, we present sensitivity projections for the upcoming NUCLEUS technical and physics runs, incorporating a data-driven treatment of the low-energy excess (LEE) observed during commissioning. We develop a likelihood framework that exploits reactor-power variation to disentangle signal and background in a low signal-to-background regime and to assess the impact of the dominant systematic uncertainties. For the Technical Run with a 7 g CaWO$_4$ target, we find competitive sensitivity to several scenarios beyond the Standard Model, which do not require a CE$\nu$NS observation. For the Physics Run, assuming complete suppression of the LEE, we project a 4.7 $\sigma$ observation of CE$\nu$NS with a statistical precision of about 20 % in 1 year, enabling a determination of the weak mixing angle at the lowest momentum transfer probed to date with CE$\nu$NS and leading CE$\nu$NS-based constraints on the neutrino charge radius and new mediator models.

hep-ex↗

arXiv2026

Characterization of the Low Energy Excess using a NUCLEUS Al$_{2}$O$_{3}$ detector

The NUCLEUS experiment aims to detect coherent elastic neutrino-nucleus scattering of reactor antineutrinos using low-threshold, gram-scale cryogenic calorimeters. Similar to other low-threshold experiments, NUCLEUS observes a sharp rise in the event rate below a few hundred eV, referred to as the low energy excess (LEE), whose origin remains yet unidentified. Building on results from the NUCLEUS testing and commissioning at the Technical University of Munich and from previous characterization campaigns, we present a comprehensive study of the background rate measured with a sapphire detector equipped with two transition-edge sensors under various experimental conditions. We find no evidence for a dependence of the LEE rate on the particle background level, whereas the results indicate that slower cooling-down procedures lead to lower initial LEE rates. The behavior of the LEE rate during the same cooldown is comparable across the measurements and is best described by a power law with a common exponent across datasets of $(-0.59 \pm 0.06)$, when time is expressed from the moment the detector reaches the 4 K temperature. These findings provide valuable guidance for future LEE mitigation strategies in the NUCLEUS experiment.

physics.ins-det↗

arXiv2025

First Measurement of Neutrino Emissions from Spent Nuclear Fuel by the Double Chooz Experiment

Neutrino emission from nuclear reactors provides real-time insights into reactor power and fuel evolution, with potential applications in monitoring and nuclear safeguards. Following reactor shutdown, a low-intensity flux of ``residual neutrinos'' persists due to the decay of long-lived fission isotopes in the partially burnt fuel remaining within the reactor cores and in spent nuclear fuel stored in nearby cooling pools. The Double Chooz experiment at the Chooz B nuclear power plant in France achieved the first quantitative measurement of this residual flux based on 17.2 days of reactor-off data. In the energy range where the residual signal is most pronounced, the neutrino detector located 400$\,$m from the cores recorded $106 \pm 18$ neutrino candidate events (5.9$\sigma$ significance). This measurement is in excellent agreement with the predicted value of $88 \pm 7$ events derived from detailed reactor simulations modeling the decay activities of fission products and incorporating the best-available models of neutrino spectra.

hep-ex↗

arXiv2025

Particle background characterization and prediction for the NUCLEUS reactor CE$\nu$NS experiment

NUCLEUS is a cryogenic detection experiment which aims to measure Coherent Elastic Neutrino-Nucleus Scattering (CE$\nu$NS) and to search for new physics at the Chooz nuclear power plant in France. This article reports on the prediction of particle-induced backgrounds, especially focusing on the sub-keV energy range, which is a poorly known region where most of the CE$\nu$NS signal from reactor antineutrinos is expected. Together with measurements of the environmental background radiations at the experimental site, extensive Monte Carlo simulations based on the Geant4 package were run both to optimize the experimental setup for background reduction and to estimate the residual rates arising from different contributions such as cosmic ray-induced radiations, environmental gammas and material radioactivity. The NUCLEUS experimental setup is predicted to achieve a total rejection power of more than two orders of magnitude, leaving a residual background component which is strongly dominated by cosmic ray-induced neutrons. In the CE$\nu$NS signal region of interest between 10 and 100 eV, a total particle background rate of $\sim$ 250 d$^{-1}$kg$^{-1}$keV$^{-1}$ is expected in the CaWO$_4$ target detectors. This corresponds to a signal-to-background ratio $\gtrsim$ 1, and therefore meets the required specifications in terms of particle background rejection for the detection of reactor antineutrinos through CE$\nu$NS.

physics.ins-det↗

arXiv2025

Commissioning of the NUCLEUS Experiment at the Technical University of Munich

The NUCLEUS experiment aims to detect coherent elastic neutrino-nucleus scattering of reactor antineutrinos on CaWO$_4$ targets in the fully coherent regime, using gram-scale cryogenic calorimeters. The experimental apparatus will be installed at the Chooz nuclear power plant in France, in the vicinity of two 4.25 GW$_{\text{th}}$ reactor cores. This work presents results from the commissioning of an essential version of the experiment at the shallow Underground Laboratory of the Technical University of Munich. For the first time, two cryogenic target detectors were tested alongside active and passive shielding systems. Over a period of two months all detector subsystems were operated with stable performance. Background measurements were conducted, providing important benchmarks for the modeling of background sources at the reactor site. Finally, we present ongoing efforts to upgrade the detector systems in preparation for a technical run at Chooz in 2026, and highlight the remaining challenges to achieving neutrino detection.

hep-ex↗

arXiv2025

Sub-keV Electron Recoil Calibration for Macroscopic Cryogenic Calorimeters using a Novel X-ray Fluorescence Source

Percent-level calibration of cryogenic macro-calorimeters with energy thresholds below 100~eV are crucial for light Dark Matter (DM) searches and reactor neutrino studies based on coherent elastic neutrino-nucleus scattering (CEvNS). This paper presents a novel calibration source based on X-ray fluorescence (XRF) of light elements. It uses a $^{55}$Fe source to irradiate a two-staged target arrangement, emitting characteristic emission lines from 677\,eV to 6.5\,keV. We demonstrate the potential of this new XRF source to calibrate a 0.75 gram CaWO$_4$ crystal of the NUCLEUS and CRAB experiments. Additionally, we introduce CryoLab, an advanced analysis tool for cryogenic detector data, featuring robust methods for data processing, calibration, and high-level analysis, implemented in MATLAB and HDF5. We also present a phenomenological model for energy resolution, which incorporates statistical contributions, systematic effects, and baseline noise, enabling a novel approach to evaluating athermal phonon collection efficiency in macro-calorimeters based on transition edge sensors (TES).

physics.ins-det↗

arXiv2025

Decoupling Pulse Tube Vibrations from a Dry Dilution Refrigerator at milli-Kelvin Temperatures

With the rising adoption of dry dilution refrigerators across scientific and industrial domains, there has been a pressing demand for highly efficient vibration decoupling systems capable of operation at cryogenic temperatures in order to achieve the low vibration levels required for operation of sensitive equipment like cryogenic detectors or quantum devices. As part of the NUCLEUS experiment, a cryogenic spring pendulum has been engineered to effectively isolate pulse tube vibrations by establishing an autonomous frame of reference for the experimental volume, while sustaining temperatures below 10 mK. Attaining attenuation of up to two orders of magnitude within the region of interest of the NUCLEUS cryogenic detectors, we achieved displacement RMS values in the order of 1 nm in the axial direction and 100 pm radially, thereby reducing vibrations below typical environmental levels. Our successful detector operation across multiple cooldown cycles demonstrated negligible sensitivity to pulse tube induced vibrations, culminating in the achievement of an ultra-low $(6.22 \pm 0.07)$ eV baseline resolution on a gram-scale CaWO$_4$ cryogenic calorimeter during continuous pulse tube operation over the course of several weeks.

physics.ins-det↗

arXiv2023

A Plastic Scintillation Muon Veto for Sub-Kelvin Temperatures

Rare-event search experiments located on-surface, such as short-baseline reactor neutrino experiments, are often limited by muon-induced background events. Highly efficient muon vetos are essential to reduce the detector background and to reach the sensitivity goals. We demonstrate the feasibility of deploying organic plastic scintillators at sub-Kelvin temperatures. For the NUCLEUS experiment, we developed a cryogenic muon veto equipped with wavelength shifting fibers and a silicon photo multiplier operating inside a dilution refrigerator. The achievable compactness of cryostat-internal integration is a key factor in keeping the muon rate to a minimum while maximizing coverage. The thermal and light output properties of a plastic scintillation detector were examined. We report first data on the thermal conductivity and heat capacity of the polystyrene-based scintillator UPS-923A over a wide range of temperatures extending below one Kelvin. The light output was measured down to 0.8K and observed to increase by a factor of 1.61$\pm$0.05 compared to 300K. The development of an organic plastic scintillation muon veto operating in sub-Kelvin temperature environments opens new perspectives for rare-event searches with cryogenic detectors at sites lacking substantial overburden.

physics.ins-det↗

arXiv2022

Exploring coherent elastic neutrino-nucleus scattering of reactor neutrinos with the NUCLEUS experiment

The NUCLEUS experiment aims to perform a high-precision measurement of Coherent Elastic Neutrino-Nucleus Scattering (CEvNS) at the EdF Chooz B nuclear power plant in France. CEvNS is a unique process to study neutrino properties and to search for physics beyond the Standard Model. The study of CEvNS is also important for light Dark-Matter searches. It could be a possible irreducible background for high-sensitivity Dark-Matter searches. NUCLEUS is an experiment under construction based on ultra-low threshold (20 eVnr) cryogenic calorimeters, operated at tens-of-mK temperatures.

physics.ins-det↗

arXiv2022

Observation of a nuclear recoil peak at the 100 eV scale induced by neutron capture

Coherent elastic neutrino-nucleus scattering and low-mass Dark Matter detectors rely crucially on the understanding of their response to nuclear recoils. We report the first observation of a nuclear recoil peak at around 112 eV induced by neutron capture. The measurement was performed with a CaWO$_4$ cryogenic detector from the NUCLEUS experiment exposed to a $^{252}$Cf source placed in a compact moderator. The measured spectrum is found in agreement with simulations and the expected peak structure from the single-$\gamma$ de-excitation of $^{183}$W is identified with 3 $\sigma$ significance. This result demonstrates a new method for precise, in-situ, and non-intrusive calibration of low-threshold experiments.

nucl-ex↗

arXiv2022

Development of a compact muon veto for the NUCLEUS experiment

The NUCLEUS experiment aims to measure coherent elastic neutrino nucleus scattering of reactor anti-neutrinos using cryogenic calorimeters. Operating at an overburden of 3 m.w.e., muon-induced backgrounds are expected to be one of the dominant background contributions. Besides a high efficiency to identify muon events passing the experimental setup, the NUCLEUS muon veto has to fulfill tight spatial requirements to fit the constraints given by the experimental site and to minimize the induced detector dead-time. We developed highly efficient and compact muon veto modules based on plastic scintillators equipped with wavelength shifting fibers and silicon photo multipliers to collect and detect the scintillation light. In this paper, we present the full characterization of a prototype module with different light read-out configurations. We conclude that an efficient and compact muon veto system can be built for the NUCLEUS experiment from a cube assembly of the developed modules. Simulations show that an efficiency for muon identification of >99 % and an associated rate of 325 Hz is achievable, matching the requirements of the NUCLEUS experiment.

physics.ins-det↗

arXiv2021

Search for Signatures of Sterile Neutrinos with Double Chooz

We present a search for signatures of neutrino mixing of electron anti-neutrinos with additional hypothetical sterile neutrino flavors using the Double Chooz experiment. The search is based on data from 5 years of operation of Double Chooz, including 2 years in the two-detector configuration. The analysis is based on a profile likelihood, i.e.\ comparing the data to the model prediction of disappearance in a data-to-data comparison of the two respective detectors. The analysis is optimized for a model of three active and one sterile neutrino. It is sensitive in the typical mass range $5 \cdot 10^{-3} $ eV$^2 \lesssim Δm^2_{41} \lesssim 3\cdot 10^{-1} $ eV$^2$ for mixing angles down to $\sin^2 2θ_{14} \gtrsim 0.02$. No significant disappearance additionally to the conventional disappearance related to $θ_{13} $ is observed and correspondingly exclusion bounds on the sterile mixing parameter $θ_{14} $ as function of $ Δm^2_{41} $ are obtained.

hep-ex↗

arXiv2019

Exploring CEvNS with NUCLEUS at the Chooz Nuclear Power Plant

Coherent elastic neutrino-nucleus scattering (CE$ν$NS) offers a unique way to study neutrino properties and to search for new physics beyond the Standard Model. Nuclear reactors are promising sources to explore this process at low energies since they deliver large fluxes of (anti-)neutrinos with typical energies of a few MeV. In this paper, a new-generation experiment to study CE$ν$NS is described. The NUCLEUS experiment will use cryogenic detectors which feature an unprecedentedly low energy threshold and a time response fast enough to be operated in above-ground conditions. Both sensitivity to low-energy nuclear recoils and a high event rate tolerance are stringent requirements to measure CE$ν$NS of reactor antineutrinos. A new experimental site, denoted the Very-Near-Site (VNS) at the Chooz nuclear power plant in France is described. The VNS is located between the two 4.25 GW$_{\mathrm{th}}$ reactor cores and matches the requirements of NUCLEUS. First results of on-site measurements of neutron and muon backgrounds, the expected dominant background contributions, are given. In this paper a preliminary experimental setup with dedicated active and passive background reduction techniques is presented. Furthermore, the feasibility to operate the NUCLEUS detectors in coincidence with an active muon-veto at shallow overburden is studied. The paper concludes with a sensitivity study pointing out the promising physics potential of NUCLEUS at the Chooz nuclear power plant.

physics.ins-det↗

arXiv2018

Yields and production rates of cosmogenic $^9$Li and $^8$He measured with the Double Chooz near and far detectors

The yields and production rates of the radioisotopes $^9$Li and $^8$He created by cosmic muon spallation on $^{12}$C, have been measured by the two detectors of the Double Chooz experiment. The identical detectors are located at separate sites and depths, which means they are subject to different muon spectra. The near (far) detector has an overburden of $\sim$120 m.w.e. ($\sim$300 m.w.e.) corresponding to a mean muon energy of $32.1\pm2.0\,\mathrm{GeV}$ ($63.7\pm5.5\,\mathrm{GeV}$). Comparing the data to a detailed simulation of the $^9$Li and $^8$He decays, the contribution of the $^8$He radioisotope at both detectors is found to be compatible with zero. The observed $^9$Li yields in the near and far detectors are $5.51\pm0.51$ and $7.90\pm0.51$, respectively, in units of $10^{-8}μ^{-1} \mathrm{g^{-1} cm^{2} }$. The shallow overburdens of the near and far detectors give a unique insight when combined with measurements by KamLAND and Borexino to give the first multi--experiment, data driven relationship between the $^9$Li yield and the mean muon energy according to the power law $Y = Y_0( / 1\,\mathrm{GeV})^{\overlineα}$, giving $\overlineα=0.72\pm0.06$ and $Y_0=(0.43\pm0.11)\times 10^{-8}μ^{-1} \mathrm{g^{-1} cm^{2}}$. This relationship gives future liquid scintillator based experiments the ability to predict their cosmogenic $^9$Li background rates.

hep-ex↗

arXiv2018

The STEREO Experiment

The STEREO experiment is a very short baseline reactor antineutrino experiment aiming at testing the hypothesis of light sterile neutrinos as an explanation of the deficit of the observed neutrino interaction rate with respect to the predicted rate, known as the Reactor Antineutrino Anomaly. The detector center is located 10 m away from the compact, highly $^{235}$U enriched core of the research nuclear reactor of the Institut Laue Langevin in Grenoble, France. This paper describes the STEREO site, the detector components and associated shielding designed to suppress the external sources of background which were characterized on site. It reports the performances in terms of detector response and energy reconstruction.

physics.ins-det↗

arXiv2016

Online Monitoring of the Osiris Reactor with the Nucifer Neutrino Detector

Originally designed as a new nuclear reactor monitoring device, the Nucifer detector has successfully detected its first neutrinos. We provide the second shortest baseline measurement of the reactor neutrino flux. The detection of electron antineutrinos emitted in the decay chains of the fission products, combined with reactor core simulations, provides an new tool to assess both the thermal power and the fissile content of the whole nuclear core and could be used by the Inter- national Agency for Atomic Energy (IAEA) to enhance the Safeguards of civil nuclear reactors. Deployed at only 7.2m away from the compact Osiris research reactor core (70MW) operating at the Saclay research centre of the French Alternative Energies and Atomic Energy Commission (CEA), the experiment also exhibits a well-suited configuration to search for a new short baseline oscillation. We report the first results of the Nucifer experiment, describing the performances of the 0.85m3 detector remotely operating at a shallow depth equivalent to 12m of water and under intense background radiation conditions. Based on 145 (106) days of data with reactor ON (OFF), leading to the detection of an estimated 40760 electron antineutrinos, the mean number of detected antineutrinos is 281 +- 7(stat) +- 18(syst) electron antineutrinos/day, in agreement with the prediction 277(23) electron antineutrinos/day. Due the the large background no conclusive results on the existence of light sterile neutrinos could be derived, however. As a first societal application we quantify how antineutrinos could be used for the Plutonium Management and Disposition Agreement.

physics.ins-det↗