arXiv subjects

G. Yang

Publications and source records attributed to G. Yang.

At least 19 recordsLinked to original sources

arXiv2026

The Eos detector: a demonstrator of hybrid optical detection technology

Eos is an R&D testbed for hybrid detector technologies, featuring state-of-the-art sub-ns photosensors, the first implementation of dichroicons in a large-scale demonstrator, and the deployment of novel detection media such as water-based liquid scintillator (WbLS). By separating Cherenkov and scintillation light, Eos leverages the benefits of both to explore the potential of next-generation neutrino technologies. An extensive radioactive source calibration program enables the characterization of position, direction, and energy reconstruction performance of a variety of target materials. Furthermore, Eos will provide data to refine optical models and inform the development and simulation of future neutrino experiments. This paper describes the as-built design and data-taking plan of Eos, outlining its scientific motivations and role in the development of future detector technologies.

physics.ins-det↗

arXiv2026

Performance of the Eos detector with water

In this manuscript we present the first results from Eos, a four tonne optical detector located at the University of California, Berkeley. The primary goal of Eos is to demonstrate the performance capabilities of scintillation-based, 'hybrid' detector technology for future neutrino detectors. The data presented were collected while both the inner target vessel and the outer buffer vessel were filled with water. The water target acts as a well-understood medium that produces only Cherenkov light, which can be used to calibrate and develop the detector model and reconstruction algorithms prior to the deployment of scintillating material. Using deployed optical and radioactive calibration sources, a series of detailed detector calibrations are performed. These enable a suite of tests for various reconstruction algorithms. Simulations that use calibrated models are compared with the data across a variety of different types of calibration sources, source positions, and rotations.

hep-ex↗

arXiv2026

Construction, commissioning, and beam test of a pilot 3D-projection opaque water-based liquid scintillator detector

We report on the design, construction, and beam test of a pilot three-dimensional projection detector based on opaque water-based liquid scintillator (oWbLS). The detector consists of an $8 \times 8 \times 16$ cm$^3$ acrylic vessel instrumented with three orthogonal planes of Kuraray Y11 multi-clad wavelength-shifting fibers read out by Hamamatsu multi-pixel photon counters. The readout electronics are based on the CITIROC front-end boards developed for the WAGASCI and SuperFGD detectors of the T2K experiment. The detector was filled with oWbLS and tested with cosmic rays and proton beams of 50, 100, 250, and 500 MeV kinetic energy at the NASA Space Radiation Laboratory at Brookhaven National Laboratory. We present three-dimensional event displays of cosmic muon and proton beam candidates, and a study of transverse light confinement via radial charge distribution measurements. The measured data show tighter light confinement than a Geant4 simulation with a 2 cm scattering length, placing the effective scattering length well below 2 cm and confirming effective optical confinement of scintillation light in the oWbLS medium. A first measurement of the hit-level timing resolution using 500 MeV proton beam data yields a single-channel timing resolution of $\sigma_t \approx 0.17$--$0.28$ ns with good photostatistics. These results demonstrate the viability of the 3D-projection oWbLS technology as a scalable, fully-active detector concept for next-generation particle physics experiments.

physics.ins-det↗

arXiv2026

Design, construction, and operation of a 30-ton Water-based Liquid scintillator detector at Brookhaven National Laboratory

Water-based Liquid Scintillator (WbLS) was proposed over a decade ago as a novel detector medium that might allow the separation and tuning of the relative ratio of the Cherenkov and scintillation signals. A detector employing this technology could support large-scale neutrino detection over both the GeV and MeV energy regimes, while its metal-loading capability could provide an effective means of neutron tagging. WbLS is attractive for two reasons. It can be deployed in very large detectors. It also allows in-situ tuning of the scintillator concentration, and hence the ratio of Cherenkov to scintillation light. Neither pure water Cherenkov detectors nor conventional liquid scintillator detectors offer this capability. At Brookhaven National Laboratory (BNL), two prototypes have been built for understanding WbLS properties and stability, with masses of 1-ton and 30-ton, respectively. We present here the 30-ton prototype detector design, installation, and initial operation including the real-time observation of a transient optical response during the staged scintillator injection. Results from the analysis of data collected in the two detectors will follow in separate publications.

physics.ins-det↗

arXiv2026

JWST Reveals Two Overmassive Black Hole Candidates in Dwarf Galaxies at z $\approx$ 0.7: Pushing Black Hole Searches into the Dwarf-Galaxy Regime

We report the discovery and characterization of two compact galaxies, Pelias and Neleus, at z ~ 0.71 and z ~ 0.75, identified in MACS J0416.1-2403 and GOODS-North. Both exhibit unusual spectral energy distributions (SEDs), with very blue rest-frame UV-optical emission and a steep rise toward near- and mid-infrared wavelengths. JWST/NIRISS and JWST/NIRSpec spectroscopy show strong rest-frame optical lines ([O III] 4959,5007 and Halpha) with extreme equivalent widths (>= 1000 Angstrom), indicating young burst-dominated populations with low metallicities (Z ~ 0.1-0.4 Zsun), low dust attenuation (Av ~ 0.2 mag), and stellar masses of Mstar ~ 10^7 Msun. Nonetheless, JWST/MIRI photometry reveals a strong mid-infrared excess that cannot be explained by stellar populations or star-formation-heated dust alone, requiring a hot-dust component most naturally associated with a deeply embedded active galactic nucleus (AGN). SED modelling yields log10(Lbol [erg/s]) ~ 43.7-44.0, implying black hole masses of log10(MBH [Msun]) ~ 5.7-6.7 under the assumption of Eddington-limited accretion. Given the very low stellar masses of the hosts, this corresponds to black-hole-to-stellar mass ratios of about 6-60%, well above the extrapolation of local scaling relations. The lack of X-ray detections suggests that the accretion may be either heavily obscured or intrinsically X-ray weak. Their SEDs also resemble those of Blue Excess Hot Dust Obscured Galaxies and show the characteristic V-shaped continuum seen in Little Red Dots, although with the inflection occurring at redder wavelengths.

astro-ph.GA↗

arXiv2025

Measurement of Light Yield Response of Gd-compatible Water-based Liquid Scintillator with the Brookhaven 1-ton testbed

The Water-based Liquid Scintillator (WbLS) enables hybrid detection by combining scintillation and Cherenkov signals, providing superior event reconstruction capabilities compared to conventional neutrino detectors. We measured the light yield of Gd-compatible WbLS at varying concentrations from 0.35\% to 1\% by mass, using cosmic-ray muons in a 1-ton scale detector at BNL. The light yield is measured as (69.16 $\pm$ 6.92) ph / MeV at 0.35\% concentration, which increased to (87.32 $\pm$ 8.73) ph / MeV at 1\%. These results establish a quantitative basis for optimizing future WbLS-based detectors in neutrino physics.

physics.ins-det↗

arXiv2025

Design and development of optical modules for the BUTTON-30 detector

BUTTON-30 is a neutrino detector demonstrator located in the STFC Boulby underground facility in the north-east of England. The main goal of the project is to deploy and test the performance of the gadolinium-loaded water-based liquid scintillator for neutrino detection in an underground environment. This will pave the way for a future large-volume neutrino observatory that can also perform remote monitoring of nuclear reactors for nonproliferation. This paper describes the design and construction of the watertight optical modules of the experiment.

physics.ins-det↗

arXiv2025

The BUTTON-30 detector at Boulby

The BUTTON-30 detector is a 30-tonne technology demonstrator designed to evaluate the potential of hybrid event detection, simultaneously exploiting both Cherenkov and scintillation light to detect particles produced in neutrino interactions. The detector is installed at a depth of 1.1 km in the Boulby Underground Laboratory allowing to test the performance of this new technology underground in a low background environment. This paper describes the design and construction of the 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

A high-lying isomer in ^{92}Zr with lifetime modulated by the atomic charge states: a proposed approach for a nuclear gamma-ray laser

The nuclides ^{92}Zr are produced and transported by using a radioactive beam line to a lowbackground detection station. After a flight time of about 1.14 {\mu}s, the ions are implanted into a carbon foil, and four {\gamma} rays deexciting the 8+ state in ^{92}Zr are observed in coincidence with the implantation signals within a few nanoseconds. We conjecture that there exists an isomer located slightly above the 8^{+} state in ^{92}Zr. The isomeric lifetime in highly charged states is extended significantly due to the blocking of internal conversion decay channels, enabling its survival over the transportation. During the slowing-down process in the carbon foil, the ^{92}Zr ions capture electron and evolve toward neutral atoms, and consequently the lifetime is restored to a normal short value. Such a high-lying isomer depopulated by a low-energy transition may provide unique opportunity to develop nuclear {\gamma} laser.

nucl-ex↗

arXiv2025

Experimental Study of Rare Kaon Decays at J-PARC with KOTO and KOTO II

The rare kaon decay $K_L\to\pi^0\nu\bar{\nu}$ is extremely sensitive to new physics, because the contribution to this decay in the Standard Model (SM) is highly suppressed and known very accurately; the branching ratio is $3\times 10^{-11}$ in the SM with a theoretical uncertainty of just 2%. The measurement of this branching ratio could provide essential new information about the flavor structure of the quark sector from the $s\to d$ transition. The decay is being searched for in the KOTO experiment at J-PARC, which has obtained the current best upper limit on the branching ratio of $2.2\times 10^{-9}$; a sensitivity to branching ratios below $10^{-10}$ is achievable by the end of the decade. A next-generation experiment at J-PARC, KOTO II, was proposed in 2024 with 82 members worldwide, including significant contributions from European members. The goal of KOTO II is to measure the $K_L\to\pi^0\nu\bar{\nu}$ branching ratio with sensitivity below $10^{-12}$ in the 2030s. Discovery of the decay with $5\sigma$ significance is achievable at the SM value of the branching ratio. An indication of new physics with a significance of 90% is possible if the observed branching ratio differs by 40% from the SM value. Another important goal of KOTO II is to measure the branching ratio of the unobserved $K_L\to \pi^0e^+e^-$ decay, which can give an input to flavor structures of new physics. Other rare $K_L$ decays and hidden-sector particles are also in the scope of the study. After 2026, KOTO will be the only dedicated rare kaon decay experiment in the world, and KOTO II is the only future rare kaon decay project currently proposed. We would like to lead a global initiative for the experimental study of rare kaon decays, with significant contributions and support from the European community.

hep-ex↗

arXiv2025

Extended source fringe flats for the JWST MIRI Medium Resolution Spectrometer

The detectors of the JWST Mid-Infrared Instrument (MIRI) Medium Resolution Spectrometer (MRS) form low-finesse resonating cavities that cause periodic count rate modulations (fringes) with peak amplitudes of up to 15% for sources external to MIRI. To detect weak features on a strong continuum and reliably measure line fluxes and line-flux ratios, fringe correction is crucial. This paper describes the first of two steps implemented in the JWST Science Calibration Pipeline, which is the division by a static fringe flat that removes the bulk of the fringes for extended sources. Fringe flats were derived by fitting a numerical model to observations of spatially extended sources. The model includes fringes that originate from two resonating cavities in the detector substrate (a third fringe component that originates from the dichroic filters is not included). The model, numerical implementation, and resulting fringe flats are described, and the efficiency of the calibration was evaluated for sources of various spatial extents on the detector. Flight fringe flats are obtained from observations of the planetary nebula NGC 7027. The two fringe components are well recovered and fitted by the model. The derived parameters are used to build a fringe flat for each MRS spectral band, except for 1A and 1B due to the low signal-to-noise ratio of NGC 7027 in these bands. When applied to extended sources, fringe amplitudes are reduced to the sub-percent level on individual spaxels. For point sources, they are reduced to amplitudes of 1 to 5% considering individual spaxels and a single dither position, and decrease to the 1 to 2% level after two-dimensional residual fringe correction. The fringe flats derived from this work are the reference files currently in use by the JWST Science Calibration Pipeline. They provide an efficient calibration for extended sources, and are less efficient for point sources.

astro-ph.IM↗

arXiv2025

Ultra High-Redshift or Closer-by, Dust-Obscured Galaxies? Deciphering the Nature of Faint, Previously Missed F200W-Dropouts in CEERS

The James Webb Space Telescope (JWST) is revolutionizing our understanding of the Universe by unveiling faint, near-infrared dropouts previously beyond our reach, ranging from exceptionally dusty sources to galaxies up to redshift $z \sim 14$. In this paper, we identify F200W-dropout objects in the Cosmic Evolution Early Release Science (CEERS) survey which are absent from existing catalogs. Our selection method can effectively identify obscured low-mass ($\log \text{M}_* \leq 9$) objects at $z \leq 6$, massive dust-rich sources up to $z \sim 12$, and ultra-high-redshift ($z > 15$) candidates. Primarily relying on NIRCam photometry from the latest CEERS data release and supplementing with Mid-Infrared/(sub-)mm data when available, our analysis pipeline combines multiple SED-fitting codes, star formation histories, and CosMix - a novel tool for astronomical stacking. Our work highlights three $2 15$, with best-fit masses compatible with $\Lambda$CDM and a standard baryons-to-star conversion efficiency. Their bi-modal redshift probability distributions suggest they could also be $z<1.5$ dwarf galaxies with extreme dust extinction. We also identify a strong line emitter galaxy at $z \sim 5$ mimicking the near-infrared emission of a $z \sim 13$ galaxy. Our sample holds promising candidates for future follow-ups. Confirming ultra high-redshift galaxies or lower-z dusty dwarfs will offer valuable insights into early galaxy formation, evolution with their central black holes and the nature of dark matter, and/or cosmic dust production mechanisms in low-mass galaxies, and will help us to understand degeneracies and contamination in high-z object searches.

astro-ph.GA↗

arXiv2025

Simultaneous Superconducting and Topological Properties in Mg-Li Electrides at High Pressures

Electrides as a unique class of emerging materials exhibit fascinating properties and hold important significance for understanding the matter under extreme conditions, which is characterized by valence electrons localized into the interstitial space as quasi-atoms (ISQs). In this work, using crystal structure prediction and first-principles calculations, we identified seven stable phases of Mg-Li that are electride with novel electronic properties under high pressure. Among them, MgLi10 is a semiconductor with a band gap of 0.22 eV; and Pm-3m MgLi is superconductor with a superconducting transition temperature of 22.8 K. The important role played by the localization degree of ISQ in the superconducting transition temperature of these electrides is revealed by systematic comparison of Mg-Li with other Li-rich electride superconductors. Furthermore, we proved that Pm-3m MgLi and Pnma MgLi also have distinct topological behavior with metallic surface states and the non-zero $Z_2$ invariant. The simultaneous coexistence of superconductivity, electronic band topology and electride property in the same structure of Pm-3m MgLi and Pnma MgLi demonstrates the feasibility of realizing multi-quantum phases in a single material, which will stimulate further research in these interdisciplinary fields.

cond-mat.mtrl-sci↗

arXiv2024

ASTRODEEP-JWST: NIRCam-HST multiband photometry and redshifts for half a million sources in six extragalactic deep fields

We present a set of photometric catalogs primarily aimed at providing the community with a comprehensive database for the study of galaxy populations in the high redshift Universe. The set gathers data from eight JWST NIRCam observational programs, targeting the Abell 2744 (GLASS-JWST, UNCOVER, DDT2756 and GO3990), EGS (CEERS), COSMOS and UDS (PRIMER), and GOODS North and South (JADES and NGDEEP) deep fields, for a total area of $\sim$0.2 sq. degrees. Photometric estimates are obtained by means of well-established techniques, including tailored improvements designed to enhance the performance on the specific dataset. We also include new measurements from HST archival data, thus collecting 16 bands spanning from 0.44 to 4.44 $\mu$m. A grand total of $\sim$530 thousand sources is detected on stacks of NIRCam 3.56 and 4.44 $\mu$m mosaics. We assess the photometric accuracy by comparing fluxes and colors against archival catalogs. We also provide photometric redshift estimates, statistically validated against a large set of robust spectroscopic data. The catalogs are publicly available on the Astrodeep website.

astro-ph.GA↗

arXiv2024

Dust and Power: Unravelling the merger - active galactic nucleus connection in the second half of cosmic history

Galaxy mergers represent a fundamental physical process under hierarchical structure formation, but their role in triggering AGNs is still unclear. We aim to investigate the merger-AGN connection using state-of-the-art observations and novel methods in detecting mergers and AGNs. We selected stellar mass-limited samples at redshift z<1 from KiDS, focusing on the KiDS-N-W2 field with a wide range of multi-wavelength data. Three AGN types, selected in the MIR, X-ray, and via SED modelling, were analysed. To identify mergers, we used convolutional neural networks trained on two cosmological simulations. We created mass and redshift-matched control samples of non-mergers and non-AGNs. We observe a clear AGN excess (a factor of 2-3) in mergers with respect to non-mergers for the MIR AGNs, and a mild excess for the X-ray and SED AGNs, indicating that mergers could trigger all 3 types but are more connected with the MIR AGNs. About half of the MIR AGNs are in mergers but it is unclear whether mergers are the main trigger. For the X-ray and SED AGNs, mergers are unlikely to be the dominant trigger. We also explore the relation using the continuous AGN fraction $f_{AGN}$ parameter. Mergers exhibit a clear excess of high $f_{AGN}$ values relative to non-mergers, for all AGNs. We unveil the first merger fraction $f_{merg}-f_{AGN}$ relation with two distinct regimes. When the AGN is not dominant, the relation is only mildly increasing or even flat, with the MIR AGNs showing the highest $f_{merg}$. In the regime of very dominant AGNs ($f_{AGN}\geq0.8$), $f_{merg}$ shows a steeply rising trend with increasing $f_{AGN}$ for all AGN types. These trends are also seen when plotted against AGN bolometric luminosity. We conclude that mergers are most connected with dust-obscured AGNs (linked to a fast-growing phase of the SMBH) and are the main or even the sole fuelling mechanism of the most powerful AGNs.

astro-ph.GA↗

arXiv2024

A Cigale module tailored (not only) for Low-Luminosity AGN

The spectral energy distribution (SED) of low-luminosity active galactic nuclei (LLAGN) presents challenges due to their faint emissions and the complexity of their accretion processes. This study introduces a new CIGALE module tailored for LLAGN, combining the empirical $L_X$-$L_{12\mu m}$ relationship with physical models like advection-dominated accretion flows (ADAFs) and truncated accretion disks. This module yields a refined depiction of LLAGN emissions, and a mock analysis shows reliable parameter recovery, with only minor biases. We tested the module on a sample of 50 X-ray-detected local galaxies, including LINERs and Seyferts, where it demonstrated good estimation of bolometric luminosities, even in the presence of significant galaxy contamination. Notably, the previous X-ray module failed to provide AGN solutions for this sample, stressing the need for a novel approach. Comparisons with mid-luminosity AGN confirm the module's robustness and applicability to AGN up to $L_X$ < $10^{45}$ erg/s. We also expanded the X-ray to bolometric correction formula, making it applicable to AGN spanning ten orders of magnitude in luminosity, and revealing lower $k_X$ values than typically assumed. Additionally, our analysis of the $\alpha_{ox}$ index, representing the slope between UV and X-ray emissions, uncovered trends that differ from those observed in high-luminosity AGN, suggesting a shift in accretion physics and photon production mechanisms in low-luminosity regimes. These results underscore the importance of a multiwavelength approach in AGN studies and reveal distinct behaviors in LLAGN compared to quasars. Our findings significantly advance the understanding of LLAGN and offer a comprehensive framework for future research aimed at completing the census of the AGN population.

astro-ph.GA↗

arXiv2024

Design, construction, and operation of a 1-ton Water-based Liquid scintillator detector at Brookhaven National Laboratory

Water-based liquid scintillators (WbLS) are attractive neutrino detector materials because they allow us to tune the ratio of the Cherenkov and scintillation signals. Using WbLS large-scale neutrino experiments can benefit from both directional reconstruction and enhanced low-energy efficiency. Furthermore, broadening the science capability of such materials by metal doping may be better suited for water based liquid scintillators. We recently constructed and commissioned a 1-ton WbLS detector with good photosensor coverage and a capable data acquisition system. We intend to use this flexible detector system as a testbed for WbLS R&D. In this paper we give an overview of the 1-ton system and provide some early analysis results.

physics.ins-det↗