arXiv subjects

P. Fierlinger

Publications and source records attributed to P. Fierlinger.

At least 19 recordsLinked to original sources

arXiv2026

Performance of the TUCAN Magnetically Shielded Room

The TRIUMF Ultracold Advanced Neutron (TUCAN) collaboration has commissioned a large magnetically shielded room to be used for measuring the neutron electric dipole moment (nEDM) to a precision of $10^{-27}~e\mathrm{cm}$. The room is composed of five layers of MuMetal and one layer of copper and sits within the $\lesssim 370~μ\mathrm{T}$ ambient field produced by the TRIUMF cyclotron. Within this environment, the quasi-static shielding factor was measured to be $2.95(2) \times 10^4$ at $0.01~\mathrm{Hz}$ with an external peak-to-peak perturbation of $2~μ\mathrm{T}$. Without the large ambient cyclotron field, the shielding factor improves to $3.40(3)\times 10^4$ at the same perturbation amplitude and frequency. After idealization in the cyclotron field, the residual field at the room center was $B = 1.8(2)~\mathrm{nT}$ and the vertical first-order gradient across the central 1~m$^3$ ($dB_{\mathrm{z}}/dz$) was $-307(26)~\mathrm{pT/m}$. With additional improvement to the idealization, and with active compensation, we expect the room to be adequate for a $10^{-27}~e\mathrm{cm}$ nEDM search.

physics.ins-det↗

arXiv2026

FINESSE: A Versatile Beamline for Fundamental Interactions with Neutrons at the European Spallation SourcE

FINESSE (A Versatile Beamline for \textbf{F}undamental \textbf{I}nteractions with \textbf{N}eutrons at the \textbf{E}uropean \textbf{S}pallation \textbf{S}ourc\textbf{E}) is a proposed versatile beamline for fundamental interactions with neutrons at the European Spallation Source. Building on the HIBEAM design studies, FINESSE extends the original concept into a dual-guide beamline capable of operating either in a high-flux configuration or in a low-background configuration within a single ESS beam port. The high-flux branch is optimized for rare-process searches, including neutron--antineutron oscillations, neutron--sterile-neutron transitions, axion-like-particle searches, neutron charge measurements, and rare neutron decays. The low-background branch is designed for precision measurements requiring strong suppression of prompt and line-of-sight backgrounds, with a cryogenic neutron electric-dipole-moment experiment used as a benchmark case. A baseline exchangeable-guide concept has been developed in which only short guide sections inside the ESS bunker are exchanged, while the upstream extraction system and chopper positions remain fixed. A staged implementation, Short FINESSE, would use the upstream section of the high-flux beamline together with a compact magnetically controlled experimental region, enabling an early physics and R\&D programme before completion of the full facility. This paper summarizes the scientific case, beamline concept, guide simulations, chopper and timing system, magnetic-field control, detector developments, and staged implementation strategy. FINESSE would establish a long-term particle-physics infrastructure at ESS, providing a beamline for both discovery-driven searches and precision neutron measurements throughout the lifetime of the facility.

physics.ins-det↗

arXiv2026

EXO-200 Public Data Release for AI/ML Applications

We present a public release of a subset of calibration data from the EXO-200 experiment, a liquid xenon time projection chamber designed to search for neutrinoless double-beta decay in $^{136}$Xe. The released dataset consists of approximately one million events collected during $^{228}$Th calibration campaigns performed near the end of Phase-II operations between February 26 and March 2, 2018. For each event, the dataset includes raw detector waveforms from the U-wire, V-wire, and avalanche photodiode (APD) readout channels together with reconstructed event quantities including charge energy, light energy, rotated energy, and charge-cluster information. The dataset is distributed in HDF5 format and is intended to support data preservation, educational activities, and the development of modern machine-learning techniques for rare-event physics. This paper describes the detector, dataset contents, file structure, and public access mechanism.

physics.ins-det↗

arXiv2025

Search for Double Beta Decays of $^{134}$Xe with EXO-200 Phase II

EXO-200 was a leading double beta decay experiment consisting of a single-phase, enriched liquid xenon time projection chamber filled with an admixture of 80.672% $^{136}$Xe and 19.098% $^{134}$Xe. The detector operated at WIPP between 2010 and 2018 and was designed to search for double beta decay of $^{136}$Xe. Data was acquired in two phases separated by a period of detector upgrades. We report on the search for $0νββ$ and $2νββ$ decay of $^{134}$Xe with Phase II EXO-200 data, with median 90% C.L. exclusion sensitivity $T_{1/2}^{0ν} \geq 3.7\times 10^{23}$ yr and $T_{1/2}^{2ν} \geq 2.6 \times 10^{21}$ yr, respectively. No statistically significant signal is observed for either decay mode. We set a world-leading lower limit on the half-life of the neutrinoless decay mode of $^{134}$Xe of $T_{1/2}^{0ν} \geq 8.7\times10^{23}$ (90% C.L.) and the second strongest constraint on the two-neutrino decay of $T_{1/2}^{2ν} \geq 2.9\times10^{21}$ (90% C.L.), a 3-fold improvement over the EXO-200 Phase I measurement. New constraints are also set for the $2νββ$ and $0νββ$ decays of $^{134}$Xe to the lowest excited state of $^{134}$Ba.

nucl-ex↗

arXiv2025

The HIBEAM Instrument at the European Spallation Source

The European Spallation Source (ESS) will be the world's brightest neutron source and will open a new intensity frontier in particle physics. The HIBEAM collaboration aims to exploit the unique potential of the ESS with a dedicated ESS instrument for particle physics which offers world-leading capability in a number of areas. The HIBEAM program includes the first search in thirty years for free neutrons converting to antineutrons and searches for sterile neutrons, ultralight axion dark matter and nonzero neutron electric charge. This paper outlines the capabilities, design, infrastructure, and scientific potential of the HIBEAM program, including its dedicated beamline, neutron optical system, magnetic shielding and control, and detectors for neutrons and antineutrons. Additionally, we discuss the long-term scientific exploitation of HIBEAM, which may include measurements of the neutron electric dipole moment and precision studies of neutron decays.

physics.ins-det↗

arXiv2024

HighNESS Conceptual Design Report: Volume I

The European Spallation Source, currently under construction in Lund, Sweden, is a multidisciplinary international laboratory. Once completed to full specifications, it will operate the world's most powerful pulsed neutron source. Supported by a 3 million Euro Research and Innovation Action within the EU Horizon 2020 program, a design study (HighNESS) has been completed to develop a second neutron source located below the spallation target. Compared to the first source, designed for high cold and thermal brightness, the new source has been optimized to deliver higher intensity, and a shift to longer wavelengths in the spectral regions of cold (CN, 2--20\,Å), very cold (VCN, 10--120\,Å), and ultracold (UCN, ${>}\,{500}$\,Å) neutrons. The second source comprises a large liquid deuterium moderator designed to produce CN and support secondary VCN and UCN sources. Various options have been explored in the proposed designs, aiming for world-leading performance in neutronics. These designs will enable the development of several new instrument concepts and facilitate the implementation of a high-sensitivity neutron-antineutron oscillation experiment (NNBAR). This document serves as the Conceptual Design Report for the HighNESS project, representing its final deliverable.

physics.ins-det↗

arXiv2024

A Ramsey Neutron-Beam Experiment to Search for Ultralight Axion Dark Matter at the ESS

High-intensity neutron beams, such as those available at the European Spallation Source (ESS), provide new opportunities for fundamental discoveries. Here we discuss a novel Ramsey neutron-beam experiment to search for ultralight axion dark matter through its coupling to neutron spins, which would cause the neutron spins to rotate about the velocity of the neutrons relative to the dark matter halo. We estimate that experiments at the HIBEAM beamline at the ESS can improve the sensitivity to the axion-neutron coupling compared to the current best laboratory limits by up to $2-3$ orders of magnitude over the axion mass range $10^{-22} \, \textrm{eV} - 10^{-16}$ eV.

hep-ph↗

arXiv2024

Particle Physics at the European Spallation Source

Presently under construction in Lund, Sweden, the European Spallation Source (ESS) will be the world's brightest neutron source. As such, it has the potential for a particle physics program with a unique reach and which is complementary to that available at other facilities. This paper describes proposed particle physics activities for the ESS. These encompass the exploitation of both the neutrons and neutrinos produced at the ESS for high precision (sensitivity) measurements (searches).

physics.ins-det↗

arXiv2023

Search for Two-neutrino Double-Beta Decay of $^{136}\rm Xe$ to the $0^+_1$ excited state of $^{136}\rm Ba$ with the Complete EXO-200 Dataset

A new search for two-neutrino double-beta ($2νββ$) decay of $^{136}\rm Xe$ to the $0^+_1$ excited state of $^{136}\rm Ba$ is performed with the full EXO-200 dataset. A deep learning-based convolutional neural network is used to discriminate signal from background events. Signal detection efficiency is increased relative to previous searches by EXO-200 by more than a factor of two. With the addition of the Phase II dataset taken with an upgraded detector, the median 90$\%$ confidence level half-life sensitivity of $2νββ$ decay to the $0^+_1$ state of $^{136}\rm Ba$ is $2.9 \times 10^{24}~\rm yr$ using a total $^{136}\rm Xe$ exposure of $234.1~\rm kg~yr$. No statistically significant evidence for $2νββ$ decay to the $0^+_1$ state is observed, leading to a lower limit of $T^{2ν}_{1/2}(0^+ \rightarrow 0^+_1) > 1.4\times10^{24}~\rm yr$ at 90$\%$ confidence level, improved by 70$\%$ relative to the current world's best constraint.

hep-ex↗

arXiv2023

Generative Adversarial Networks for Scintillation Signal Simulation in EXO-200

Generative Adversarial Networks trained on samples of simulated or actual events have been proposed as a way of generating large simulated datasets at a reduced computational cost. In this work, a novel approach to perform the simulation of photodetector signals from the time projection chamber of the EXO-200 experiment is demonstrated. The method is based on a Wasserstein Generative Adversarial Network - a deep learning technique allowing for implicit non-parametric estimation of the population distribution for a given set of objects. Our network is trained on real calibration data using raw scintillation waveforms as input. We find that it is able to produce high-quality simulated waveforms an order of magnitude faster than the traditional simulation approach and, importantly, generalize from the training sample and discern salient high-level features of the data. In particular, the network correctly deduces position dependency of scintillation light response in the detector and correctly recognizes dead photodetector channels. The network output is then integrated into the EXO-200 analysis framework to show that the standard EXO-200 reconstruction routine processes the simulated waveforms to produce energy distributions comparable to that of real waveforms. Finally, the remaining discrepancies and potential ways to improve the approach further are highlighted.

hep-ex↗

arXiv2023

Search for MeV Electron Recoils from Dark Matter in EXO-200

We present a search for electron-recoil signatures from the charged-current absorption of fermionic dark matter using the EXO-200 detector. We report an average electron recoil background rate of $6.8 \times 10^{-4}\, \mathrm{cts}\,\mathrm{kg}^{-1}\mathrm{yr}^{-1}\mathrm{keV}^{-1}$ above $4\,\mathrm{MeV}$ and find no statistically significant excess over our background projection. Using a total ${}^{136}\mathrm{Xe}$ exposure of $234.1\,\mathrm{kg}\,\mathrm{yr}$ we exclude new parameter space for the charged-current absorption cross-section for dark matter masses between $m_χ= 2.6\,\mathrm{MeV} - 11.6\,\mathrm{MeV}$ with a minimum of $6\times 10^{-51}\,\mathrm{cm}^2$ at $8.3\,\mathrm{MeV}$ at the $90\%$ confidence level.

hep-ex↗

arXiv2022

The Development of the NNBAR Experiment

The NNBAR experiment for the European Spallation Source will search for free neutrons converting to antineutrons with a sensitivity improvement of three orders of magnitude compared to the last such search. This paper describes progress towards a conceptual design report for NNBAR. The design of a moderator, neutron reflector, beamline, shielding and annihilation detector is reported. The simulations used form part of a model which will be used for optimisation of the experiment design and quantification of its sensitivity.

physics.ins-det↗

arXiv2022

Development of a High Intensity Neutron Source at the European Spallation Source: The HighNESS project

The European Spallation Source (ESS), presently under construction in Lund, Sweden, is a multidisciplinary international laboratory that will operate the world's most powerful pulsed neutron source. Supported by a 3M Euro Research and Innovation Action within the EU Horizon 2020 program, a design study (HighNESS) is now underway to develop a second neutron source below the spallation target. Compared to the first source, located above the spallation target and designed for high cold and thermal brightness, the new source will provide higher intensity, and a shift to longer wavelengths in the spectral regions of cold (2 /- 20 Å), very cold (VCN, 10 /- 120 Å), and ultra cold (UCN, > 500 Å) neutrons. The core of the second source will consist of a large liquid deuterium moderator to deliver a high flux of cold neutrons and to serve secondary VCN and UCN sources, for which different options are under study. The features of these new sources will boost several areas of condensed matter research and will provide unique opportunities in fundamental physics. Part of the HighNESS project is also dedicated to the development of future instruments that will make use of the new source and will complement the initial suite of instruments in construction at ESS. The HighNESS project started in October 2020. In this paper, the ongoing developments and the results obtained in the first year are described.

physics.ins-det↗

arXiv2022

A Highly Drift-stable Atomic Magnetometer for Fundamental Physics Experiments

We report the design and performance of a non-magnetic drift stable optically pumped cesium magnetometer with a measured sensitivity of 35 fT at 200 s integration time and stability below 50 fT between 70 s and 600 s. To our knowledge this is the most stable magnetic field measurement to date. The sensor is based on the nonlinear magneto-optical rotation effect: in a Bell-Bloom configuration a higher order polarization moment (alignment) of Cs atoms is created with a pump laser beam in an anti-relaxation coated Pyrex cell under vacuum, filled with Cs vapor at room temperature. The polarization plane of light passing through the cell is modulated due the precession of the atoms in an external magnetic field of 2.1 muT, used to optically determine the Larmor precession frequency. Operation is based on a sequence of optical pumping and observation of freely precessing spins at a repetition rate of 8 Hz. This free precession decay readout scheme separates optical pumping and probing and thus ensures a systematically highly clean measurement. Due to the residual offset of the sensor of < 15 pT together with the cross-talk free operation of adjacent sensors, this device is uniquely suitable for a variety of experiments in low-energy particle physics with extreme precision, here as highly stable and systematically clean reference probe in search for time-reversal symmetry violating electric dipole moments.

physics.app-ph↗

arXiv2021

Search for Majoron-emitting modes of $^{136}$Xe double beta decay with the complete EXO-200 dataset

A search for Majoron-emitting modes of the neutrinoless double-beta decay of $^{136}$Xe is performed with the full EXO-200 dataset. This dataset consists of a total $^{136}$Xe exposure of 234.1 kg$\cdot$yr, and includes data with detector upgrades that have improved the energy threshold relative to previous searches. A lower limit of T$_{1/2}^{\rm{^{136}Xe}}>$4.3$\cdot$10$^{24}$ yr at 90\% C.L. on the half-life of the spectral index $n=1$ Majoron decay was obtained, a factor of 3.6 more stringent than the previous limit from EXO-200, corresponding to a constraint on the Majoron-neutrino coupling constant of $|\langle g_{ee}^{M}\rangle|$$<(0.4$-$0.9)\cdot10^{-5}$. The lower threshold and the additional data taken resulted in a factor 8.4 improvement for the $n=7$ mode compared to the previous EXO search. This search provides the most stringent limits to-date on the Majoron-emitting decays of $^{136}$Xe with spectral indices $n=1,2,3,$ and 7.

hep-ex↗

arXiv2021

The EXO-200 detector, part II: Auxiliary Systems

The EXO-200 experiment searched for neutrinoless double-beta decay of $^{136}$Xe with a single-phase liquid xenon detector. It used an active mass of 110 kg of 80.6%-enriched liquid xenon in an ultra-low background time projection chamber with ionization and scintillation detection and readout. This paper describes the design and performance of the various support systems necessary for detector operation, including cryogenics, xenon handling, and controls. Novel features of the system were driven by the need to protect the thin-walled detector chamber containing the liquid xenon, to achieve high chemical purity of the Xe, and to maintain thermal uniformity across the detector.

physics.ins-det↗

arXiv2020

Measurement of the scintillation and ionization response of liquid xenon at MeV energies in the EXO-200 experiment

Liquid xenon (LXe) is employed in a number of current and future detectors for rare event searches. We use the EXO-200 experimental data to measure the absolute scintillation and ionization yields generated by $γ$ interactions from $^{228}$Th (2615~keV), $^{226}$Ra (1764~keV) and $^{60}$Co (1332~keV and 1173~keV) calibration sources, over a range of electric fields. The $W$-value that defines the recombination-independent energy scale is measured to be $11.5~\pm~0.5$~(syst.)~$\pm~0.1$~(stat.) eV. These data are also used to measure the recombination fluctuations in the number of electrons and photons produced by the calibration sources at the MeV-scale, which deviate from extrapolations of lower-energy data. Additionally, a semi-empirical model for the energy resolution of the detector is developed, which is used to constrain the recombination efficiency, i.e., the fraction of recombined electrons that result in the emission of a detectable photon. Detailed measurements of the absolute charge and light yields for MeV-scale electron recoils are important for predicting the performance of future neutrinoless double beta decay detectors.

physics.ins-det↗

arXiv2020

New high-sensitivity searches for neutrons converting into antineutrons and/or sterile neutrons at the European Spallation Source

The violation of Baryon Number, $\mathcal{B}$, is an essential ingredient for the preferential creation of matter over antimatter needed to account for the observed baryon asymmetry in the universe. However, such a process has yet to be experimentally observed. The HIBEAM/NNBAR %experiment program is a proposed two-stage experiment at the European Spallation Source (ESS) to search for baryon number violation. The program will include high-sensitivity searches for processes that violate baryon number by one or two units: free neutron-antineutron oscillation ($n\rightarrow \bar{n}$) via mixing, neutron-antineutron oscillation via regeneration from a sterile neutron state ($n\rightarrow [n',\bar{n}'] \rightarrow \bar{n}$), and neutron disappearance ($n\rightarrow n'$); the effective $Δ\mathcal{B}=0$ process of neutron regeneration ($n\rightarrow [n',\bar{n}'] \rightarrow n$) is also possible. The program can be used to discover and characterise mixing in the neutron, antineutron, and sterile neutron sectors. The experiment addresses topical open questions such as the origins of baryogenesis, the nature of dark matter, and is sensitive to scales of new physics substantially in excess of those available at colliders. A goal of the program is to open a discovery window to neutron conversion probabilities (sensitivities) by up to three orders of magnitude compared with previous searches. The opportunity to make such a leap in sensitivity tests should not be squandered. The experiment pulls together a diverse international team of physicists from the particle (collider and low energy) and nuclear physics communities, while also including specialists in neutronics and magnetics.

physics.ins-det↗