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H. Chen

Publications and source records attributed to H. Chen.

At least 19 recordsLinked to original sources
arXiv2026

The NOvA Test Beam Experiment

NOvA is a long-baseline neutrino oscillation experiment designed to study the neutrino mixing parameters, mass ordering, and CP violation in the lepton sector. A key component of the success of the experiment is a robust understanding of the systematic uncertainties associated with detector response and calibration. To address this, NOvA deployed a Test Beam experiment at the Fermilab Test Beam Facility, which collected data from April 2019 through July 2022. The NOvA Test Beam experiment used a 30-ton segmented liquid scintillator detector functionally identical to the NOvA Near and Far Detectors to analyze tagged particles produced from p-Cu collisions, with instrumentation capable of selecting and identifying electrons, muons, pions, kaons, and protons with momentum ranging from 0.4-1.5GeV/c. Analysis of the collected data provides a better understanding of the largest systematic uncertainties impacting NOvA's analyses, which include the detector response, energy calibration, and hadronic and electromagnetic energy resolutions.

hep-ex↗
arXiv2026

NOvA Dual-Baseline Search for Active-to-Sterile Neutrino Oscillations using Neutrino- and Antineutrino-Enriched Samples

We report a search for neutrino oscillations to sterile neutrinos in the NOvA detectors under a model with three active and one sterile neutrinos. This search simultaneously fits data in the two NOvA detectors and is the first from NOvA to use both neutrino- and antineutrino-mode beams, with exposures of $26.61\times10^{20}$ and $12.50\times10^{20}$ protons on target, respectively. There is no evidence for sterile neutrinos in the data and we are able to exclude regions of parameter space that were allowed by previous experiments, including most of the allowed region reported by IceCube.

hep-ex↗
arXiv2026

Neutron detector response modeling in NOvA

Neutrons can present a significant challenge for neutrino experiments in which energy reconstruction is critical. With the ability to escape detection completely and with a weak correlation between their kinetic energy and any eventual energy deposition, it is difficult to fully account for neutrons produced in neutrino interactions. This in turn leads to significant model dependence when evaluating neutron-related systematic uncertainties. The NOvA experiment is a long-baseline neutrino oscillation experiment with a high-statistics sample of antineutrino data collected by its near detector. We report an excess relative to data of simulated neutron candidates with low energy depositions when using standard Geant4 physics lists. The simulation excess is traced to an overabundance of secondary photons produced from interactions of neutrons with kinetic energy greater than \SI{20}{\mega\eV}. Improved agreement with data is obtained by applying the data-driven neutron-on-carbon \menate model for neutrons between \SI{20}{\mega\eV} and ${\sim}$\SI{100}{\mega\eV}. With \menate, the residual oversimulation is more uniform across the calorimetric neutron energy spectrum, suggesting possible overproduction of primary neutrons by the GENIE neutrino interaction generator. These results motivate the adoption of \menate-supplemented Geant4 simulation as the nominal simulation in the production of future \nova simulation.

hep-ex↗
arXiv2026

Quality control and quality assurance evaluation of ALFE2, a large-dynamic-range front-end ASIC de-veloped for the ATLAS Liquid Argon Calorimeter high-luminosity LHC upgrade

ALFE2 is a front-end ASIC developed for the ATLAS Liquid Argon (LAr) Calorimeter upgrade during the High-Luminosity Large Hadron Collider (HL-LHC) phase. ALFE2 comprises four preamplifier/shaper channels, each providing two distinct gain outputs to cover a 16-bit dynamic range. A robotic system has been developed for the automatic quality control test of ALFE2, and over 10% of the 80,000 chips have been evaluated by September 2025. The evaluation has allowed us to establish grading criteria. Using these criteria, a yield of over 85% was achieved in the evaluation tests, and these criteria are now being applied to the ongoing full-production QC. Irradiation tests were also performed for the quality assurance of ALFE2. No significant performance degradation was observed during the total-ionizing-dose (TID) test. Based on the single-event effect (SEE) test results, an error rate of fewer than 4.6 single-event upsets (SEUs) per day is extrapolated for the entire ATLAS LAr Calorimeter during HL-LHC operation.

physics.ins-det↗
arXiv2026

Absolute Calibration of a Time-Resolved High Resolution X-ray Spectrometer for the National Ignition Facility (invited)

A high resolution, Diagnostic Instrument Manipulator (DIM)-based x-ray Bragg crystal spectrometer has been calibrated for and deployed at the National Ignition Facility (NIF) to diagnose plasma conditions in ignition capsules near stagnation times. The spectrometer has two conical crystals in the Hall geometry focusing rays from the Kr He$\alpha$, Ly$\alpha$, and He$\beta$ complexes onto a streak camera, with the physics objectives of measuring time-resolved electron density and temperature through observing Stark broadening and the relative intensities of dielectronic satellites. A third von H\'amos crystal that time-integrates the Kr He$\alpha$, He$\beta$ and intervening energy range provides in-situ calibration for the streak camera signals. The spectrometer has been absolutely calibrated using a microfocus x-ray source, an array of CCD and single-photon-counting detectors, and multiple K- and L-absorption edge filters at the Princeton Plasma Physics Laboratory (PPPL) x-ray laboratory. Measurements of the integrated reflectivity, energy range, and energy resolution for each crystal are discussed. These calibration data provide absolute x-ray signal levels for NIF measurements, enabling precise filter selection and comparisons to simulations.

physics.plasm-ph↗
arXiv2026

Hot Spot Evolution Measured by High-Resolution X-Ray Spectroscopy at the National Ignition Facility

Evolution of the hot spot plasma conditions was measured using high-resolution x-ray spectroscopy at the National Ignition Facility (NIF). The capsules were filled with DD gas with trace levels of Kr, and had either a high-density-carbon (HDC) ablator or a tungsten (W)-doped HDC ablator. Time-resolved measurement of the Kr He$\beta$ spectra, absolutely calibrated by a simultaneous time-integrated measurement, allows inference of the electron density and temperature through observing Stark broadening and the relative intensities of dielectronic satellites. By matching the calculated hot spot emission using a collisional-radiative code to experimental observations, the hot spot size and areal density are determined. These advanced spectroscopy techniques further reveal the effect of W dopant in the ablator on the hot spot parameters for their improved implosion performance.

physics.plasm-ph↗
arXiv2026

Production and installation of wavelength-shifting reflective light enhancers for the Short-Baseline Near Detector

We report on the design, production, and installation of a wavelength-shifting reflective system on the cathode of the Short-Baseline Near Detector (SBND), a liquid argon time projection chamber located along the Fermilab Booster Neutrino Beam. To increase and homogenize scintillation-light collection, 64 double-sided plates were fabricated from FR4, laminated with specular reflector film and coated with 300 $\mu$g/cm$^2$ of tetraphenyl butadiene (TPB) wavelength shifter using controlled physical vapor deposition. The coating uniformity was validated through dedicated measurements of deposited mass and profilometry studies. Because exposure to ambient blue/UV light could degrade the TPB, protective filtering and controlled storage conditions were implemented during handling and installation. The coated plates were assembled between conductive meshes for high-voltage compatibility and installed in situ during detector integration. This system constitutes the largest TPB-coated area deployed in a neutrino detector. It operates in conjunction with SBND's photon detection system, which consists of photomultiplier tubes and X-ARAPUCAs. Early light-collection measurements show high uniformity and light response across the detector, supporting improved triggering, calorimetry, and position reconstruction in SBND.

physics.ins-det↗
arXiv2026

GUP-corrected black holes: Thermodynamic properties, evaporation time and shadow constraint from EHT Observations of M87* and Sgr A*

In this manuscript, we implement the generalized uncertainty principle (GUP) with linear and quadratic moment for Schwarzschild black hole metric in order to study the influence of quantum effect on the thermodynamics and evaporation of black hole. To this end, we first derive the GUP-modified Hawking temperature of a black hole in the semi-classical framework. Due to the existence of the GUP effect, there is a maximum Hawking temperature. We determine the entropy, heat capacity and Helmholtz free energy with heuristic analysis that investigates the particle absorbed by black hole. Furthermore, we also verify that these quantities are modified by the GUP, the influence of quantum effect on the black hole phase transition is discussed in detail. Then, we analyze the black hole evaporation process in the mentioned framework and examine the obtained results by graphical methods and compare them with each other. We likewise explore the behavior of the event horizon radius, photon sphere radius, and shadow silhouette when influenced by the GUP-corrected Schwarzschild black hole (GCSBH) parameters. We intend to establish restrictions for $\alpha$ by utilizing the event horizon telescope (EHT) data for M87* and Sagittarius A* (Sgr A*). Our findings show that Sgr A* provides more robust constraints. As the parameter $\beta$ grows, the range of constraints for $\alpha$ expands. For Sgr A* one, we find that the shadow radius is close to the observed value at smaller values of $\alpha$.

gr-qc↗
arXiv2026

Precision measurement of positron decay modes of Xe-125 in the LUX-ZEPLIN experiment

The radioisotope $^{125}\text{Xe}$ is a short-lived ($T_{1/2}\sim16.9 h$) activation product of the neutron calibrations performed in the LUX-ZEPLIN experiment. Subsequently, $^{125}$Xe decays primarily ($>99\%$) via electron capture, but positron emission has been confirmed by direct measurement to at least the 243 keV level of $^{125}\text{I}$. An additional decay to the 188keV level is expected from triple-coincident measurements of the annihilation and relaxation $\gamma$ rays, but has not been directly confirmed. By utilizing multiple-scatter event analysis and the pre-activation data to constrain backgrounds, this work reports positron emission with a statistical significance of 5.5$\sigma$. This corresponds to a total branching ratio of $0.29\pm0.08_{\text{stat.}}\pm0.04_{\text{sys.}}$ %, and is the first constraint to the individual branching levels of $^{125}\text{I}$.

hep-ex↗
arXiv2026

Pushing the Limits of Pulse Shape Discrimination in a Large Liquid Xenon Detector

The LUX-ZEPLIN (LZ) experiment is a direct-detection dark matter experiment, optimized to search for weakly interacting massive particles (WIMPs) through WIMP-nucleon interactions. The main challenge in dark matter detection is differentiating between WIMP signals and background events. In LZ, the ratio of ionization to scintillation signals (charge-to-light) is the primary method for rejecting electronic recoil (ER) background. Pulse shape discrimination (PSD) offers a method for additional ER backgrounds rejection in liquid xenon detectors. In this paper, the discrimination power of PSD with the LZ experiment is discussed. To precisely characterize the scintillation pulse shape, an analysis framework is developed to reconstruct the detection time of individual photons. Using LZ calibration data, the photon-timing prompt fraction discriminator is optimized and achieves ER leakage as low as $15\%$. For specific background processes such as $^{124}$Xe double electron capture, the leakage is reduced further to about $5\%$. PSD is combined with charge-to-light to form two-factor discrimination (TFD). The optimized TFD performance is compared with the performance of the charge-to-light method, with the corresponding false positive rate reduced by up to a factor of two for large scintillation pulses. Finally, PSD and TFD are applied to data from LZ's WS2024 run and their performance is summarized.

physics.ins-det↗
arXiv2026

Low-Energy Radon Backgrounds from Electrode Grids in Dual-Phase Xenon TPCs

The dual-phase xenon time projection chamber (TPC) is a powerful technology to detect rare interactions such as scatters of dark matter particles on nuclei. In particular, the built-in gain of ionization signals in a dual-phase TPC makes it sensitive to events in the few-electron regime, as expected from low-mass dark matter interactions. The pursuit of this low-energy sensitivity through ionization-only signal detection has so far been hindered by excessive electron backgrounds observed across experiments. Much of this background is attributed to the plate-out of $^{222}$Rn decay chain isotopes on the high voltage electrode grid surfaces that span the full cross section of the TPC. This work presents a first-principle model constructed for this background, the predictions of which are consistent with data from the LZ and LUX experiments. We then discuss mitigation strategies of this background in future dual-phase TPCs and the possibility of applying this grid background model to ionization-only dark matter searches.

hep-ex↗
arXiv2026

Suppression of Electromagnetic Pulses from Laser-Target Interactions by Strong Magnetic Fields

Laser-target interactions generate intense electromagnetic pulses (EMP) that can interfere with measurements and damage equipment. In this paper we show that applying a magnetic field to nanosecond pulse laser-target interactions decreases the magnitude of EMP. We demonstrate this effect in two experiments with different geometries (spherical vs. planar), laser intensities (${\sim}10^{13}$ vs. ${\sim} 10^{15}$~W/cm$^2$) and applied field strength (12~T vs. 0.1~T) that both observed suppression of EMP in the ${\sim} 1$~GHz band (by factors of $0.65\times$ and $0.32\times$ respectively). We then observe the opposite effect at high intensities with a picosecond pulse: for planar experiments with laser intensities ${\sim}10^{19}$~W/cm$^2$ and magnetic fields of 6--10~T, the magnitude of EMP is increased by a factor of $1.75\times$. These results provide a benchmark for models of EMP generation, but suggest that magnetic fields are not a viable solution for mitigating EMP on the high intensity laser facilities where it is most damaging.

physics.plasm-ph↗
arXiv2026

Measurement of the Muon Flux at the Sanford Underground Research Facility with the LUX-ZEPLIN Dark Matter Detector

High-energy cosmic-ray muons reaching deep underground laboratories can cause events in detectors that mimic signals expected from dark matter particles, neutrinos, or rare decays. Knowledge of the muon flux and energy spectrum is important for evaluating the background rate caused by muons and their secondaries. In this paper, we report the measurement of the cosmic-ray muon flux in the Davis Campus of the Sanford Underground Research Facility with the LUX-ZEPLIN detector. Using 366.4~days of exposure, the muon rate through the detector was measured as $10.94\pm0.17_\textrm{stat.}~\textrm{day}^{-1}$ with energy thresholds of 20~MeV in the inner xenon detector and 8 MeV in the outer liquid scintillator detector. This rate corresponds to a muon flux of $(5.09\pm0.08_\textrm{stat.}\pm0.10_\textrm{sys.})\times10^{-9}~\textrm{cm}^{-2}\textrm{s}^{-1}$ in the Davis Cavern.

hep-ex↗
arXiv2026

Dark matter effects on the properties of hybrid neutron stars

We study the effects of dark matter on the properties of hybrid neutron stars, in particular the influence on the mass-radius relation, the value of the maximum mass, and the hadron-quark phase transition. To single out the equilibrium configurations of dark-matter-admixed hybrid neutron stars (DHSs), we also study their radial oscillations. Both the stellar structure equations and the radial oscillation equations are solved for the two-fluid system, where the ordinary matter component and dark matter component couple only through gravity. For the ordinary matter components, we adopt the Brueckner-Hartree-Fock method for nuclear matter, and the Dyson-Schwinger or the field-correlator model for quark matter. For the dark matter component, we use a non-self-annihilating self-interacting fermionic model. We find that the presence of dark matter in DHSs leads to a decrease of the critical mass of the hadron-quark phase transition, a related possible onset of quark matter in dark-matter accreting stars, and a significant reduction of radial oscillation frequencies.

nucl-th↗
arXiv2026

Inverse Design of Tunable Infrared Metasurface Absorbers via a Conditional Wasserstein Generative Adversarial Network

Narrowband perfect absorbers are interesting for spectrum sensing, molecular detection, and infrared imaging. However, their design remains constrained by intuitive, iterative methods that lack flexibility, while also facing challenges in multi-objective optimization. Here, we introduce a deep learning-enabled inverse-design framework that overcomes these limitations through a conditional Wasserstein Generative Adversarial Network (WGAN). The main contribution of this work is a dual-channel image encoding scheme that jointly represents the geometry and thickness of a Si$_3$N$_4$ meta-layer, facilitating the network to learn the distribution of viable structures for a target optical response. This approach naturally solves the inherent ``one-to-many'' design issue, giving a diverse portfolio of functional candidates from a single input spectrum. The designed absorbers achieve exceptional spectral fidelity, with resonance peak errors below 5 nm, a mean squared error (MSE) on the order of $10^{-3}$, and the capacity to produce over 10 distinct, high-performance designs per target. Furthermore, we demonstrate the model's robustness under oblique illumination, showing that it can be efficiently fine-tuned to maintain spectral accuracy across incidence angles from $10^\circ$ to $40^\circ$ by transfer learning, thus extending its practical utility to non-normal operating conditions. Full-wave simulations confirm that the generated geometries support a hybrid plasmonic-dielectric resonance, leading to near-perfect absorption and strong near-field enhancement. Our study provides a robust, physics-aware design paradigm that moves beyond conventional parametric optimization. The introduced framework establishes a versatile platform for the on-demand inverse design of advanced photonic devices for sensing, spectroscopy, and optical signal processing.

physics.optics↗
arXiv2026

Search for Cosmic Ray Electron Boosted Dark Matter with the CDEX-10 Experiment

We present new constraints on the cosmic ray electron boosted light dark matter (CReDM) using the 205.4 kg$\cdot$day data of the CDEX-10 experiment located at the China Jinping Underground Laboratory. The cosmic ray electron spectrum and distribution in the Galaxy are generated by the $\tt GALPROP$ code package. In the calculation process of DM-electron scattering process in the Galaxy, we consider the energy-dependency of the DM-electron scattering cross section. The constraints on CReDM are set for both heavy and light mediator scenarios using the CDEX-10 dataset. The result exceeds previous Standard Halo Model (SHM) limits for DM mass lower than 0.6 MeV in heavy mediator case and corresponds to the best sensitivity among all direct detection experiments from 1 keV to 0.5 MeV in the light mediator scenario.

hep-ex↗
arXiv2026

E-XQR-30: Evidence for an Increase in the Ionization State of Metal Absorbers from z~6 to z~2

We investigate the evolution of the ionization state of metal-enriched gas in and around galaxies near the epoch of reionization using a sample of 488 metal absorption systems at 4.3<z<6.3 from the E-XQR-30 survey. We classify the absorption systems based on whether they display only low-ionization absorption (CII, SiII, MgII), only high-ionization absorption (CIV, SiIV), or both. The percentage of low-ionization-only systems decreases from 24% at $z\sim$6 to 2% at $z\sim$4.3, whilst the fraction of high-ionization-only systems increases from 52% to 82%. For mixed absorbers (with both low and high ionization absorption), we use the column density ratios log(N_CII/N_CIV) and log(N_SiII/N_SiIV) to quantify the average ionization as a function of redshift. The log(N_SiII/N_SiIV) ratio does not change significantly over 5$\lesssim z \lesssim$6.3. We combine the E-XQR-30 log(N_CII/N_CIV) measurements with literature measurements at $z\sim$2-4 and find that the log(N_CII/N_CIV) ratio declines by a factor of $\sim$20 between $z\sim$6 and $z\sim$2. To explore possible drivers of this evolution, we run photoionization models of gas slabs illuminated by a uniform UV background at fixed density, metallicity and HI column density. We find that the increase in the ionization state of metal absorbers towards lower redshifts can likely be explained by some combination of 1) an increase in the metallicity of CIV-absorbing gas and 2) a decrease in the typical HI column densities of the absorbing gas, driven by the declining cosmic mean density and a rapid rise in the strength of the UV background during the final stages of reionization.

astro-ph.GA↗
arXiv2025

Searches for Light Dark Matter and Evidence of Coherent Elastic Neutrino-Nucleus Scattering of Solar Neutrinos with the LUX-ZEPLIN (LZ) Experiment

We present searches for light dark matter (DM) with masses 3-9 GeV/$c^2$ in the presence of coherent elastic neutrino-nucleus scattering (CE$\nu$NS) from $^{8}$B solar neutrinos with the LUX-ZEPLIN experiment. This analysis uses a 5.7 tonne-year exposure with data collected between March 2023 and April 2025. In an energy range spanning 1-6 keV, we report no significant excess of events attributable to dark matter nuclear recoils, but we observe a significant signal from $^{8}$B CE$\nu$NS interactions that is consistent with expectation. We set world-leading limits on spin-independent and spin-dependent-neutron DM-nucleon interactions for masses down to 5 GeV/$c^2$. In the no-dark-matter scenario, we observe a signal consistent with $^{8}$B CE$\nu$NS events, corresponding to a $4.5\sigma$ statistical significance. This is the most significant evidence of $^{8}$B CE$\nu$NS interactions and is enabled by robust background modeling and mitigation techniques. This demonstrates LZ's ability to detect rare signals at keV-scale energies.

hep-ex↗