arXiv subjects

A. M. Szelc

Publications and source records attributed to A. M. Szelc.

At least 19 recordsLinked to original sources

arXiv2026

Axion-Like Particle Search with a Hybrid Cherenkov-Scintillation Detector

This analysis presents the first proof-of-concept search for axion-like particles (ALPs) using a hybrid Cherenkov-scintillation detector at a beam-dump facility. The work is based on the Coherent CAPTAIN-Mills (CCM) experiment, a 10-ton liquid argon light collection detector located at Los Alamos National Laboratory. The CCM200 detector is instrumented with 200 photomultiplier tubes (PMTs), providing approximately 50% photocathode coverage. To enable optical discrimination, 80% of the PMTs are coated with a wavelength-shifting material while the remaining 20% are left uncoated. This configuration, combined with nanosecond-scale timing resolution, provides sensitivity to prompt Cherenkov radiation while maintaining efficient detection of liquid argon scintillation light [1, 2]. This analysis constructs four observables that exploit the Cherenkov emission and event topology expected from ALP-induced electromagnetic interactions. These observables are combined into a likelihood-ratio classifier that provides powerful rejection of steady-state backgrounds. No statistically significant excess above the expected background prediction is observed for $10^{-3}~\mathrm{MeV} < m_a < 10~\mathrm{MeV}$. Nevertheless, the improved background rejection enabled by hybrid Cherenkov-scintillation detection allows this analysis to surpass the sensitivity of the previous CCM120 search [3] despite less exposure and demonstrate the physics potential for hybrid Cherenkov-scintillation detectors.

hep-ex↗

arXiv2025

Cosmic Ray Measurements Using Charge and Light Readout in a Pixelated Liquid Argon Time Projection Chamber

Liquid argon time projection chambers have emerged as a competitive technology for detecting solar neutrinos. The SoLAr collaboration was formed to explore argon detectors with pixelated light and charge readout, aiming for high detection efficiency and improved energy resolution. Building on the success of an initial prototype, we present results obtained with a second SoLAr prototype (V2), a $30 \times 30 \times 30$ cm$^{3}$ time projection chamber operated in a cryostat containing several hundred kilograms of liquid argon. We report measurements of cosmic-ray muons using both tracking and calorimetry from light and charge sensors, and we highlight the improved performance achieved through combined charge and light reconstruction. These results demonstrate the promise of dual-readout detectors and motivate future prototyping efforts toward kiloton-scale facilities.

physics.ins-det↗

arXiv2025

First Event-by-Event Identification of Cherenkov Radiation from Sub-MeV Particles in Liquid Argon

This Letter reports the event-by-event observation of Cherenkov light from sub-MeV electrons in a high scintillation light-yield liquid argon (LAr) detector by the Coherent CAPTAIN-Mills (CCM) experiment. The CCM200 detector, located at Los Alamos National Laboratory, instruments 7 tons (fiducial volume) of LAr with 200 8-inch photomultiplier tubes (PMTs), 80% of which are coated in a wavelength shifting material and the remaining 20% are uncoated. In the prompt time region of an event, defined as $-6 \leq t < 0$ ns relative to the event start time $t=0$, the uncoated PMTs are primarily sensitive to visible Cherenkov photons. Using gamma-rays from a $^{22}$Na source for production of sub-MeV electrons, we isolated prompt Cherenkov light with $>5σ$ confidence and developed a selection to obtain a low-background electromagnetic sample. This is the first event-by-event observation of Cherenkov photons from sub-MeV electrons in a high-yield scintillator detector, and represents a milestone in low-energy particle detector development.

physics.ins-det↗

arXiv2025

Measurement of the Liquid Argon Scintillation Pulse Shape Using Differentiable Simulation in the Coherent CAPTAIN-Mills Experiment

The Coherent CAPTAIN-Mills (CCM) experiment is a liquid argon (LAr) light collection detector searching for MeV-scale neutrino and Beyond Standard Model physics signatures. Two hundred 8-inch photomultiplier tubes (PMTs) instrument the 7 ton fiducial volume with 50% photocathode coverage to detect light produced by charged particles. CCM's light-based approach reduces requirements of LAr purity, compared to other detection technologies, such that sub-MeV particles can be reliably detected without additional LAr filtration and with O(1) parts-per-million of common contaminants. We present a measurement of LAr light production and propagation parameters, with uncertainties, obtained from a sample of MeV-scale electromagnetic events. The optimization of this high-dimensional parameter space was facilitated by a differentiable optical photon Monte-Carlo simulation, and detailed PMT response characterization. This result accurately predicts the timing and spatial distribution of light due to scintillation and Cherenkov emission in the detector. This is the first description of photon propagation in LAr to include several effects, including: anomalous dispersion of the index of refraction near the ultraviolet resonance, Mie scattering from impurities, and Cherenkov light production.

physics.ins-det↗

arXiv2025

First Observation of Antiproton Annihilation At Rest on Argon in the LArIAT Experiment

We report the first observation and measurement of antiproton annihilation at rest on argon using the LArIAT experiment. Antiprotons from a charged particle test beam that come to rest inside LArIAT's liquid argon time projection chamber (LArTPC) are identified through beamline instrumentation and LArTPC track reconstruction algorithms. The multiplicity of charged particle tracks originating from the annihilation vertex is manually assessed through hand-scanning, resulting in a distribution with a mean of 3.2 $\pm$ 0.4 tracks and a standard deviation of 1.3 tracks. This is consistent with an automated track reconstruction, which produces a mean of 2.8 $\pm$ 0.4 tracks and a standard deviation of 1.2 tracks. Good agreement is found between data and Monte Carlo simulations for both methods. Additionally, we report the shower multiplicity and particle identification of outgoing tracks, both of which align closely with theoretical predictions. These findings will contribute to modeling of intranuclear annihilation interactions on argon, including scenarios such as neutron-antineutron oscillations.

hep-ex↗

arXiv2024

Demonstration of the light collection stability of a PEN-based wavelength shifting reflector in a tonne scale liquid argon detector

Liquid argon detectors rely on wavelength shifters for efficient detection of scintillation light. The current standard is tetraphenyl butadiene (TPB), but it is challenging to instrument on a large scale. Poly(ethylene 2,6-naphthalate) (PEN), a polyester easily manufactured as thin sheets, could simplify the coverage of large surfaces with wavelength shifters. Previous measurements have shown that commercial grades of PEN have approximately 50% light conversion efficiency relative to TPB. Encouraged by these results, we conducted a large-scale measurement using $4~m^2$ combined PEN and specular reflector foils in a two-tonne liquid argon dewar to assess its stability over approximately two weeks. This test is crucial for validating PEN as a viable substitute for TPB. The setup used for the measurement of the stability of PEN as a wavelength shifter is described, together with the first results, showing no evidence of performance deterioration over a period of 12 days.

physics.ins-det↗

arXiv2024

Testing Meson Portal Dark Sector Solutions to the MiniBooNE Anomaly at CCM

A solution to the MiniBooNE excess invoking rare three-body decays of the charged pions and kaons to new states in the MeV mass scale was recently proposed as a dark-sector explanation. This class of solution illuminates the fact that, while the charged pions were focused in the target-mode run, their decay products were isotropically suppressed in the beam-dump-mode run in which no excess was observed. This suggests a new physics solution correlated to the mesonic sector. We investigate an extended set of phenomenological models that can explain the MiniBooNE excess as a dark sector solution, utilizing long-lived particles that might be produced in the three-body decays of the charged mesons and the two-body anomalous decays of the neutral mesons. Over a broad set of interactions with the long-lived particles, we show that these scenarios can be compatible with constraints from LSND, KARMEN, and MicroBooNE, and evaluate the sensitivity of the ongoing and future data taken by the Coherent CAPTAIN Mills experiment (CCM) to a potential discovery in this parameter space. See addendum for updated predictions for future MicroBooNE sensitivity.

hep-ph↗

arXiv2024

First Demonstration of a Combined Light and Charge Pixel Readout on the Anode Plane of a LArTPC

The novel SoLAr concept aims to extend sensitivities of liquid-argon neutrino detectors down to the MeV scale for next-generation detectors. SoLAr plans to accomplish this with a liquid-argon time projection chamber that employs an anode plane with dual charge and light readout, which enables precision matching of light and charge signals for data acquisition and reconstruction purposes. We present the results of a first demonstration of the SoLAr detector concept with a small-scale prototype detector integrating a pixel-based charge readout and silicon photomultipliers on a shared printed circuit board. We discuss the design of the prototype, and its operation and performance, highlighting the capability of such a detector design.

physics.ins-det↗

arXiv2024

Measurements of Pion and Muon Nuclear Capture at Rest on Argon in the LArIAT Experiment

We report the measurement of the final-state products of negative pion and muon nuclear capture at rest on argon by the LArIAT experiment at the Fermilab Test Beam Facility. We measure a population of isolated MeV-scale energy depositions, or blips, in 296 LArIAT events containing tracks from stopping low-momentum pions and muons. The average numbers of visible blips are measured to be 0.74 $\pm$ 0.19 and 1.86 $\pm$ 0.17 near muon and pion track endpoints, respectively. The 3.6$σ$ statistically significant difference in blip content between muons and pions provides the first demonstration of a new method of pion-muon discrimination in neutrino liquid argon time projection chamber experiments. LArIAT Monte Carlo simulations predict substantially higher average blip counts for negative muon (1.22 $\pm$ 0.08) and pion (2.34 $\pm$ 0.09) nuclear captures. We attribute this difference to Geant4's inaccurate simulation of the nuclear capture process.

hep-ex↗

arXiv2023

Prospects for detecting axionlike particles at the Coherent CAPTAIN-Mills experiment

We show results from the Coherent CAPTAIN Mills (CCM) 2019 engineering run which begin to constrain regions of parameter space for axion-like particles (ALPs) produced in electromagnetic particle showers in an 800 MeV proton beam dump, and further investigate the sensitivity of ongoing data-taking campaigns for the CCM200 upgraded detector. Based on beam-on background estimates from the engineering run, we make realistic extrapolations for background reduction based on expected shielding improvements, reduced beam width, and analysis-based techniques for background rejection. We obtain reach projections for two classes of signatures; ALPs coupled primarily to photons can be produced in the tungsten target via the Primakoff process, and then produce a gamma-ray signal in the Liquid Argon (LAr) CCM detector either via inverse Primakoff scattering or decay to a photon pair. ALPs with significant electron couplings have several additional production mechanisms (Compton scattering, $e^+e^-$ annihilation, ALP-bremsstrahlung) and detection modes (inverse Compton scattering, external $e^+e^-$ pair conversion, and decay to $e^+e^-$). In some regions, the constraint is marginally better than both astrophysical and terrestrial constraints. With the beginning of a three year run, CCM will be more sensitive to this parameter space by up to an order of magnitude for both ALP-photon and ALP-electron couplings. The CCM experiment will also have sensitivity to well-motivated parameter space of QCD axion models. It is only a recent realization that accelerator-based large volume liquid argon detectors designed for low energy coherent neutrino and dark matter scattering searches are also ideal for probing ALPs in the unexplored $\sim$MeV mass scale.

hep-ph↗

arXiv2023

First Constraints on Heavy QCD Axions with a Liquid Argon Time Projection Chamber using the ArgoNeuT Experiment

We present the results of a search for heavy QCD axions performed by the ArgoNeuT experiment at Fermilab. We search for heavy axions produced in the NuMI neutrino beam target and absorber decaying into dimuon pairs, which can be identified using the unique capabilities of ArgoNeuT and the MINOS near detector. This decay channel is motivated by a broad class of heavy QCD axion models that address the strong CP and axion quality problems with axion masses above the dimuon threshold. We obtain new constraints at a 95\% confidence level for heavy axions in the previously unexplored mass range between 0.2-0.9 GeV, for axion decay constants around tens of TeV.

hep-ex↗

arXiv2022

Measurement of the ($π^-$, Ar) total hadronic cross section at the LArIAT experiment

We present the first measurement of the negative pion total hadronic cross section on argon, which we performed at the Liquid Argon In A Testbeam (LArIAT) experiment. All hadronic reaction channels, as well as hadronic elastic interactions with scattering angle greater than 5~degrees are included. The pions have a kinetic energies in the range 100-700~MeV and are produced by a beam of charged particles impinging on a solid target at the Fermilab Test Beam Facility. LArIAT employs a 0.24~ton active mass Liquid Argon Time Projection Chamber (LArTPC) to measure the pion hadronic interactions. For this measurement, LArIAT has developed the ``thin slice method", a new technique to measure cross sections with LArTPCs. While generally higher than the prediction, our measurement of the ($π^-$,Ar) total hadronic cross section is in agreement with the prediction of the Geant4 model when considering a model uncertainty of $\sim$5.1\%.

hep-ex↗

arXiv2022

First Dark Matter Search Results From Coherent CAPTAIN-Mills

This paper describes the operation of the Coherent CAPTAIN-Mills (CCM) detector located at the Lujan Neutron Science Center (LANSCE) at Los Alamos National Laboratory (LANL). CCM is a 10-ton liquid argon (LAr) detector located 20 meters from a high flux neutron/neutrino source and is designed to search for sterile neutrinos ($ν_s$) and light dark matter (LDM). An engineering run was performed in Fall 2019 to study the characteristics of the CCM120 detector by searching for coherent scattering signals consistent with $ν_s$'s and LDM resulting from $π^+$ and $π^0$ decays in the tungsten target. New parameter space in a leptophobic dark matter model was excluded for DM masses between $\sim2.0$ and 30 MeV. The lessons learned from this run have guided the development and construction of the new CCM200 detector that will begin operations in 2021 and significantly improve on these searches.

hep-ex↗

arXiv2022

First Leptophobic Dark Matter Search from Coherent CAPTAIN-Mills

We report the first results of a search for leptophobic dark matter (DM) from the Coherent CAPTAIN-Mills (CCM) liquid argon (LAr) detector. An engineering run with 120 photomultiplier tubes (PMTs) and $17.9 \times 10^{20}$ protons-on-target (POT) was performed in Fall 2019 to study the characteristics of the CCM detector. The operation of this 10-ton detector was strictly light-based with a threshold of 50 keV and used coherent elastic scattering off argon nuclei to detect DM. Despite only 1.5 months of accumulated luminosity, contaminated LAr, and non-optimized shielding, CCM's first engineering run already achieved sensitivity to previously unexplored parameter space of light dark matter (LDM) models with a baryonic vector portal. With an expected background of 115,005 events, we observe 115,005+16.5 events which is compatible with background expectations. For a benchmark mediator-to-dark matter mass ratio of $m_{_{V_B}}/m_χ=2.1$, DM masses within the range $9\,\text{MeV} \lesssim m_χ\lesssim 50\,\text{MeV}$ have been excluded at 90% C.L. in the leptophobic model after applying the Feldman-Cousins test statistic. CCM's upgraded run with 200 PMTs, filtered LAr, improved shielding, and ten times more POT will be able to exclude the remaining thermal relic density parameter space of this model, as well as probe new parameter space of other leptophobic DM models.

hep-ex↗

arXiv2022

Direct comparison of PEN and TPB wavelength shifters in a liquid argon detector

A large number of particle detectors employ liquid argon as their target material owing to its high scintillation yield and its ability to drift ionization charge over large distances. Scintillation light from argon is peaked at 128 nm and a wavelength shifter is required for its efficient detection. In this work, we directly compare the light yield achieved in two identical liquid argon chambers, one of which is equipped with PolyEthylene Naphthalate (PEN) and the other with TetraPhenyl Butadiene (TPB) wavelength shifter. Both chambers are lined with enhanced specular reflectors and instrumented with SiPMs with a coverage fraction of approximately 1%, which represents a geometry comparable to the future large scale detectors. We measured the light yield of the PEN chamber to be 39.4$\pm$0.4(stat)$\pm$1.9(syst)% of the yield of the TPB chamber. Using a Monte Carlo simulation this result is used to extract the wavelength shifting efficiency of PEN relative to TPB equal to 47.2$\pm$5.7%. This result paves the way for the use of easily available PEN foils as a wavelength shifter, which can substantially simplify the construction of future liquid argon detectors.

physics.ins-det↗

arXiv2022

A deep-learning based raw waveform region-of-interest finder for the liquid argon time projection chamber

The liquid argon time projection chamber (LArTPC) detector technology has an excellent capability to measure properties of low-energy neutrinos produced by the sun and supernovae and to look for exotic physics at very low energies. In order to achieve those physics goals, it is crucial to identify and reconstruct signals in the waveforms recorded on each TPC wire. In this paper, we report on a novel algorithm based on a one-dimensional convolutional neural network (CNN) to look for the region-of-interest (ROI) in raw waveforms. We test this algorithm using data from the ArgoNeuT experiment in conjunction with an improved noise mitigation procedure and a more realistic data-driven noise model for simulated events. This deep-learning ROI finder shows promising performance in extracting small signals and gives an efficiency approximately twice that of the traditional algorithm in the low energy region of $\sim$0.03-0.1 MeV. This method offers great potential to explore low-energy physics using LArTPCs.

physics.ins-det↗

arXiv2021

New constraints on tau-coupled Heavy Neutral Leptons with masses $m_N = 280-970$ MeV

A search for Heavy Neutral Leptons has been performed with the ArgoNeuT detector exposed to the NuMI neutrino beam at Fermilab. We search for the decay signature $N \to νμ^+ μ^-$, considering decays occurring both inside ArgoNeuT and in the upstream cavern. In the data, corresponding to an exposure to $1.25 \times 10^{20}$ POT, zero passing events are observed consistent with the expected background. This measurement leads to a new constraint at 90\% confidence level on the mixing angle $\left\vert U_{τN}\right\rvert^2$ of tau-coupled Dirac Heavy Neutral Leptons with masses $m_N =$ 280 - 970 MeV, assuming $\left\vert U_{eN}\right\rvert^2 = \left\vert U_{μN}\right\rvert^2 = 0$.

hep-ex↗

arXiv2021

Wavelength-Shifting Performance of Polyethylene Naphthalate Films in a Liquid Argon Environment

Liquid argon is commonly used as a detector medium for neutrino physics and dark matter experiments in part due to its copious scintillation light production in response to its excitation and ionization by charged particle interactions. As argon scintillation appears in the vacuum ultraviolet (VUV) regime and is difficult to detect, wavelength-shifting materials are typically used to convert VUV light to visible wavelengths more easily detectable by conventional means. In this work, we examine the wavelength-shifting and optical properties of poly(ethylene naphthalate) (PEN), a recently proposed alternative to tetraphenyl butadiene (TPB), the most widely-used wavelength-shifter in argon-based experiments. In a custom cryostat system with well-demonstrated geometric and response stability, we use 128~nm argon scintillation light to examine various PEN-including reflective samples' light-producing capabilities, and study the stability of PEN when immersed in liquid argon. The best-performing PEN-including test reflector was found to produce 34% as much visible light as a TPB-including reference sample, with widely varying levels of light production between different PEN-including test reflectors. Plausible origins for these variations, including differences in optical properties and molecular orientation, are then identified using additional measurements. Unlike TPB-coated samples, PEN-coated samples did not produce long-timescale light collection increases associated with solvation or suspension of wavelength-shifting material in bulk liquid argon.

physics.ins-det↗