arXiv subjects

Stefan Schoppmann

Publications and source records attributed to Stefan Schoppmann.

12 recordsLinked to original sources

arXiv2026

Review of Hybrid and Opaque Scintillator Technologies Advancing Neutrino and Dark Matter Detectors

Organic liquid scintillators are used since several decades, especially in neutrino physics. They excel at the detection of low-energy particles where energy and timing information is required. Organic liquid scintillators have advantages such as high light yield, radio purity, cost effectiveness, and more. However, they also exhibit disadvantages, most prominently a lack of vertex resolution and particle identification. Various novel ideas have emerged over the course of the last decade to improve the performance of organic liquid scintillators. Among them are most prominently hybrid and opaque scintillators. In this proceedings, these novel scintillators are reviewed and their current applications in the research fields of neutrino and dark matter physics are illustrated.

physics.ins-det↗

arXiv2025

Search for Double Beta Plus Decays with NuDoubt++

Double beta plus decay is a rare nuclear disintegration process. Difficulties in its measurement arise from suppressed decay probabilities, experimentally challenging decay signatures and low natural abundances of suitable candidate nuclei. In this presentation, we propose NuDoubt++, a new detector concept to overcome these challenges. It is based on the first-time combination of hybrid and opaque scintillation detector technology paired with novel light read-out techniques. This approach is particularly suitable detecting positron (beta plus) signatures. We expect to discover two-neutrino double beta plus decay modes within 1 tonne-week exposure and are able to probe neutrinoless double beta plus decays at several orders of magnitude improved significance compared to current experimental limits.

physics.ins-det↗

arXiv2025

Combining Hybrid and Opaque Scintillator Techniques in the Search for Double Beta Plus Decays

Double beta plus decay is a rare nuclear disintegration process. Difficulties in its measurement arise from suppressed decay probabilities, experimentally challenging decay signatures and low natural abundances of suitable candidate nuclei. In this article, we propose a new detector concept to overcome these challenges. It is based on the first-time combination of hybrid and opaque scintillation detector technology paired with novel light read-out techniques. This approach is particularly suitable detecting positron (beta plus) signatures. We expect to discover two-neutrino double beta plus decay modes within 1 tonne-week exposure and are able to probe neutrinoless double beta plus decays at several orders of magnitude improved significance compared to current experimental limits.

physics.ins-det↗

arXiv2025

PhyLiNO: A Forward-Folding Likelihood-Fit Framework for Neutrino Oscillation Physics

We present a framework for the analysis of data from neutrino oscillation experiments. The framework performs a profile likelihood fit and employs a forward-folding technique to optimize its model with respect to the oscillation parameters. It is capable of simultaneously handling multiple datasets from the same or different experiments and their correlations. The code of the framework is optimized for performance and allows for convergence times of a few seconds handling hundreds of fit parameters, thanks to multi-threading and usage of GPUs. The framework was developed in the context of the Double Chooz experiment, where it was successfully used to fit three- and four-flavor models to the data, as well as in the measurement of the energy spectrum of reactor neutrinos. We demonstrate its applicability to other experiments by applying it to a study of the oscillation analysis of a medium baseline reactor experiment similar to JUNO.

physics.comp-ph↗

arXiv2025

LiquidO: Neutrino Detection and Imaging in Opaque Media

For several decades now, scintillator detectors have found a wide range of applications in particle physics, including neutrino detection, the search for dark matter and even medical imaging. These detectors so far have strongly relied on the transparency of the scintillating medium, through which light is typically propagated to surrounding photosensors. In this work, we present the results of a 10 litre prototype based on a novel detection approach where an opaque scintillator medium is used to confine light near its creation point that is then collected by a grid of wavelength-shifting fibres traversing the detector. The prototype is operated with different media, including the novel opaque scintillator NoWaSH whose scattering length varies with temperature. Our results progressively demonstrate the temperature-dependent stochastic confinement of the light, with 90% (80%) of the light being confined within a radius of 5 cm (4 cm) when the scattering length is on the order of a few millimetres. The results also demonstrate the pulse shape resolution of our setup capable of resolving Cherenkov and scintillation light. Altogether, the observations match the performance expected for this new type of detector, whose capabilities are expected to include the imaging of particle interactions down to MeV-energies.

physics.ins-det↗

arXiv2024

A Hands-on Experience with a Novel Scintillation Detector for Particle Physics

Particle physics, when taught in the classroom or lecture theatre, suffers from a lack of practical experience by students. Thus, we describe the construction of a fully working small particle physics detector using state of the art detector technology for demonstration in educational context. Most of our setup can be constructed with relatively moderate effort, given that a home-level 3D-printer, a photosensor and readout electronics (at least an oscilloscope) are available.

physics.ed-ph↗

arXiv2022

Review of Novel Approaches to Organic Liquid Scintillators in Neutrino Physics

Organic liquid scintillators have been used for decades in many neutrino physics experiments. They are particularly suited for the detection of low-energy neutrinos where energy and timing information is required. Organic liquid scintillators exhibit advantages such as high light yield, cost effectiveness, radio purity, and more. However, they also entail disadvantages, most prominently a lack of vertex resolution and particle identification. In recent years, various novel ideas have emerged to improve the performance of organic liquid scintillators. In this review, novel approaches to organic liquid scintillators in neutrino experiments as of 2022 are reviewed and their prospects and applications compared.

physics.ins-det↗

arXiv2021

Status of Anomalies and Sterile Neutrino Searches at Nuclear Reactors

Two anomalies at nuclear reactors, one related to the absolute antineutrino flux, one related to the antineutrino spectral shape, have drawn special attention to the field of reactor neutrino physics during the past decade. Numerous experimental efforts have been launched to investigate the reliability of flux models and to explore whether sterile neutrino oscillations are at the base of the experimental findings. This review aims to provide an overview on the status of experimental searches at reactors for sterile neutrino oscillations and measurements of the antineutrino spectral shape in mid-2021. The individual experimental approaches and results are reviewed. Moreover, global and joint oscillation and spectral shape analyses are discussed. Many experiments allow setting constraints on sterile oscillation parameters, but cannot yet cover the entire relevant parameter space. Others find evidence in favour of certain parameter space regions. In contrast, findings on the spectral shape appear to give an overall consistent picture across experiments and allow narrowing down contributions of certain isotopes.

hep-ex↗

arXiv2019

Novel Opaque Scintillator for Neutrino Detection

There is rising interest in organic scintillators with low scattering length for future neutrino detectors. Therefore, a new scintillator system was developed based on admixtures of paraffin wax in linear alkyl benzene. The transparency and viscosity of this gel-like material can be tuned by temperature adjustment. Whereas it is a colorless transparent liquid at temperatures around 40C it has a milky wax structure below 20C. The production and properties of such a scintillator as well as its advantages compared to transparent liquids are described.

physics.ins-det↗

arXiv2019

Search for eV Sterile Neutrinos -- The STEREO Experiment [Blois 2019]

The STEREO experiment is designed to test the hypothesis of light sterile neutrinos being the cause of the Reactor Antineutrino Anomaly. It measures the antineutrino energy spectrum from the compact core of the ILL research reactor in six identical detector cells covering baselines between 9 and 11 m. Results from 119 days of reactor turned on and 211 days of reactor turned off are reported. Using a direct comparison between neutrino interaction rates of all cells, independent of any flux prediction, we find compatibility with the null oscillation hypothesis. The best fit point of the Reactor Antineutrino Anomaly is rejected at 99% C.L.

hep-ex↗

arXiv2019

Search for eV Sterile Neutrinos -- The STEREO Experiment [TAUP 2017]

In the recent years, major milestones in neutrino physics were accomplished at nuclear reactors: the smallest neutrino mixing angle $θ_{13}$ was determined with high precision and the emitted antineutrino spectrum was measured at unprecedented resolution. However, two anomalies, the first one related to the absolute flux and the second one to the spectral shape, have yet to be solved. The flux anomaly is known as the Reactor Antineutrino Anomaly and could be caused by the existence of a light sterile neutrino eigenstate participating in the neutrino oscillation phenomenon. Introducing a sterile state implies the presence of a fourth mass eigenstate, while global fits favour oscillation parameters around $\sin^{2}(2θ)=0.09$ and $Δm^{2}=1.8\textrm{eV}^{2}$. The STEREO experiment was built to finally solve this puzzle. It is one of the first running experiments built to search for eV sterile neutrinos and takes data since end of 2016 at ILL Grenoble, France. At a short baseline of 10 metres, it measures the antineutrino flux and spectrum emitted by a compact research reactor. The segmentation of the detector in six target cells allows for independent measurements of the neutrino spectrum at multiple baselines. An active-sterile flavour oscillation could be unambiguously detected, as it distorts the spectral shape of each cell's measurement differently. This contribution gives an overview on the STEREO experiment, along with details on the detector design, detection principle and the current status of data analysis.

hep-ex↗

arXiv2019

Production and Properties of the Liquid Scintillators used in the Stereo Reactor Neutrino Experiment

The electron antineutrino spectrum in the Stereo reactor experiment (ILL Grenoble) is measured via the inverse beta decay signals in an organic liquid scintillator. The six target cells of the Stereo detector are filled with about 1800 litres of Gd-loaded liquid scintillator optimised for the requirements of the experiment. These target cells are surrounded by similar cells containing liquid scintillator without the Gd-loading. The development and characteristics of these scintillators are reported. In particular, the transparency, light production and pulse shape discrimination capabilities of the organic liquids are discussed.

physics.ins-det↗