arXiv subjects

Z. Wang

Publications and source records attributed to Z. Wang.

At least 19 recordsLinked to original sources

arXiv2026

Drift wave turbulence and transport analysis of hot ion L-mode plasma with fishbone instability on the HL-3 tokamak

We establish the cross-scale coupling by which a fishbone mode governs both toroidal rotation and drift-wave turbulence in the HL-3 hot ion mode ($T_i \approx 3T_e$, $T_i(0)\approx9.8$\,keV). Combining multi-diagnostic measurements, OMFIT modeling, and TGLF simulations, we show that under 2.5\,MW co-injected NBI a steep fast-ion pressure gradient excites an $m=1,n=1$ fishbone mode. The mode redistributes resonant fast ions outward and decouples the NBI torque, and the sawtooth crash it triggers collapses the rotation from above $100$ to $60$\,krad/s. The same fast ions drive the fishbone and stabilize ion scale ITG/TEM turbulence. Their redistribution lowers the instability threshold and erodes the internal transport barrier. The effective ITG threshold combines a dominant temperature-ratio term, a fast-ion dilution factor, and an $E\times B$ shear term. TGLF scans show the high $T_i/T_e$ ratio suppresses all transport fluxes, synergistically with the fast-ion population. A single macroscopic MHD mode governs both momentum balance and microturbulence stability.

physics.plasm-ph↗

arXiv2026

Investigating a TeV-Halo Candidate around PSR J1928+1746 with HAWC

We present an updated High-Altitude Water Cherenkov (HAWC) analysis of the crowded Galactic-plane area near PSR J1928+1746, which was previously linked to the extended source 3HWC J1928+178. With 2904 days of HAWC data, improved event reconstruction, and a multicomponent likelihood model that includes six TeV source components and Galactic diffuse emission, we describe the region using six components and find a distinct, moderately extended source close to PSR J1928+1746. This source, HAWC J1928+1750, is detected from about 2 TeV to above 100 TeV and is well-described by a log-parabola spectrum with normalization $K = 5.0 \times 10^{-15}$ TeV$^{-1}$ cm$^{-2}$ s$^{-1}$ at 12 TeV, index $α= 2.09$, curvature $β= 0.35$, and Gaussian extension $σ= 0.19^\circ$. Interpreting the emission using diffusion-halo templates under the assumption $B = 8 μ\mathrm{G}$ yields the diffusion coefficient D(100 TeV) = $2.1 \times 10^{27}$ cm$^2$ s$^{-1}$, which is about 500 times smaller than typical interstellar diffusion values at similar energies. This suggests that particle transport around PSR J1928+1746 is strongly suppressed under the TeV-halo interpretation. The TeV spectrum is consistent with leptonic inverse-Compton emission originating from pulsar-injected electrons and positrons, which requires less than approximately 1% of the pulsar's characteristic spin-down energy. However, a hadronic contribution from the surrounding environment cannot be excluded.

astro-ph.HE↗

arXiv2026

oMEGACat. IX. Chemical Tagging of Omega Centauri Populations with Machine-Learning-Inferred Abundances from the MUSE Spectrograph

We present chemical abundance measurements for 7,302 red giant branch stars within the half-light radius (~5') of $ω$ Centauri ($ω$ Cen), derived from MUSE spectra using the neural network model DD-Payne. DD-Payne effectively identifies spectral features of C, N, and O for [Fe/H]>-1.0 dex; Mg for [Fe/H]>-1.5 dex; and Na, Ca, and Ba for all metallicities. By combining these measurements with previous high-resolution studies, we create the most comprehensive picture of $ω$ Cen's rich chemical evolutionary history. For the first time, we map elemental variations across the entire chromosome diagram, which is widely used to identify multiple populations. We analyze the median chemical abundance trends as functions of age and metallicity for different subpopulations. The DD-Payne measurements of [C/Fe], [N/Fe], and [O/Fe] extend literature trends to higher metallicities and show continuous abundance-metallicity relations, with [(C+N+O)/Fe] increasing steadily with [Fe/H]. [Ca/Fe] and the s-process element [Ba/Fe] also increase with metallicity across all populations. For [Ba/Fe], the chemically enhanced (P2) populations are more enriched than primordial (P1) and the intermediate (Im) populations. Furthermore, [N/Fe] correlates strongly with stellar age while [Ca/Fe] and [Ba/Fe] exhibit a weaker age dependence. Using these abundance-metallicity-age relations, we evaluate formation scenarios of $ω$ Cen proposed in the literature and find none fully explains all the observed relations. Our study demonstrates that combining MUSE with machine learning enables large-sample stellar abundance measurements in crowded cluster cores, overcoming the limitations of fiber-fed spectroscopy for studying multiple stellar populations and their evolutionary histories.

astro-ph.GA↗

arXiv2026

TeV Gamma-Ray Emission in the DA 495 Region from HAWC Observations of J1952+2924, J1954+2837, and J1958+2848

Previous observations of the DA 495 region, which contains the pulsar wind nebula (PWN) DA 495 and other very-high-energy (VHE; $>100~\textrm{GeV}$) gamma-ray emitters, showed inconsistent results across different VHE experiments, including differences in the measured flux of DA 495 and in the number of reported sources. Our new dedicated analysis using 3071 days of HAWC data resolves these discrepancies. We identify three extended sources, HAWC J1952+2924 (DA 495), HAWC J1954+2837, and HAWC J1958+2848, all with curved spectra, and find a hint of a fourth source. For DA 495, a multi-wavelength analysis, including our results, radio, X-ray, and other gamma-ray data, reveals that its extended emission is best described by leptonic interactions with an inferred magnetic field of $B\sim10~μ\textrm{G}$ and that hadronic components are not required. On the other hand, we interpret the other two sources, which have no confirmed counterparts, as TeV halos associated with nearby pulsars, PSR J1954+2836 and PSR J1958+2846, respectively. These results reinforce the interpretation of DA 495 as a leptonic-dominated PWN and add two candidates to the growing population of TeV halos.

astro-ph.HE↗

arXiv2026

FRB 20250607A: Weirder Than Fiction

We present a detailed analysis of FRB 20250607A, a two-component FRB detected by the CRAFT survey which exhibits several unusual component-dependent properties, including apparent differential DM, circular polarisation, and time-resolved RM, together with a polarisation-angle (PA) swing that persists through the scattering tail. The scattering timescale and scintillation bandwidth are inconsistent with a single thin-screen origin, placing the dominant scattering screen within $\lesssim61$ kpc of the FRB source. The lack of PA flattening in the scattering tail is a behaviour not previously reported in an FRB or pulsar and difficult to reconcile with a simple propagation origin. We find no statistically significant differential DM between the two components despite an apparent, and visually obvious, difference in their dispersion, indicating that current uncertainties may be overly conservative. If this apparent differential DM is true, it implies a substantial difference in electron column density between the component sightlines. Two further CRAFT FRBs, FRB 20190611B and FRB 20210407E, show similarly large component-dependent electron-column differences, corresponding to electron-density contrasts consistent with plasma local to a neutron-star magnetosphere. We find no evidence for generalised Faraday rotation, and FRB 20210407E shows component-dependent PA structure. Taken together, these results suggest that the observed DM, circular polarisation, and PA behaviour may arise from differing sightlines through an inhomogeneous or evolving magnetosphere rather than from independent phenomena. Multi-component FRBs therefore provide a sensitive probe of plasma structure local to their progenitors.

astro-ph.HE↗

arXiv2026

Investigating IceCube Neutrino Alerts with the HAWC $γ$-Ray Observatory

Neutrino emission from astrophysical sources has long been considered a signature of cosmic-ray acceleration. The IceCube neutrino observatory has observed a diffuse flux of TeV-PeV neutrinos, but very few confirmed sources have emerged. With the recent publication of IceCube Event Catalog (IceCat-1), IceCube has released a list of the most promising astrophysical neutrino events since May 2011. Using the archival data from the High Altitude Water Cherenkov (HAWC) Gammma-ray observatory, we perform a coincidence search for gamma rays and neutrinos using a Bayesian Block algorithm with the public IceCube alerts from IceCat-1, along with additional alerts issued later. In this work, we consider 368 alerts, up to July 8, 2025, that are within HAWC's field of view. We observe approximately a 5\% coincident detection rate, which is consistent with expectations from background. Two of these detections contain the Active Galactic Nuclei (AGN) Markarian 421 and Markarian 501. We discuss the likelihood that the neutrino/$γ$-ray coincidences are false positives and a brief overview of the results.

astro-ph.HE↗

arXiv2026

Real-Time Wiener Deconvolution for feature reconstruction in JUNO

In particle physics, experiments generate substantial amounts of data that can be difficult to process without preliminary scaling. To avoid losing potentially crucial data, experimental collaborations are studying novel techniques for real-time data processing to extract features for further physics analysis. A common approach, especially in neutrino physics, is to use FPGAs for data acquisition and pre-processing. This paper presents an advanced Real-Time Wiener deconvolution algorithm designed to leverage the processing capabilities of the FPGA integrated into the readout boards of the Jiangmen Underground Neutrino Observatory (JUNO). The goal is to enable real-time reconstruction of the signal generated by photomultiplier tubes (PMTs) when neutrino interactions are detected. By exploiting online reconstruction of the signal generated by PMTs, we expect to improve the detection of low-energy depositions, such as those produced by transient astrophysical phenomena. These depositions are usually not saved because of the significant background that affects the low end of the energy spectrum, which would result in a large trigger rate, hence a large amount of data required for storage. This paper presents the features of the algorithm, including its ability to manage high-throughput data streams with minimal latency, adaptability, and resilience in discerning the characteristics of input data. Performance is evaluated on a JUNO electronic board. This study further demonstrates the potential of FPGA-based solutions for neutrino physics.

physics.ins-det↗

arXiv2026

Ion-Scale Waves Regulated by Plasma Beta and Cross Helicity: Observational Evidence for the Helicity Barrier in Imbalanced Solar Wind Turbulence

Ion-scale waves are believed to play an important role in heating of the solar corona and wind, though their generation mechanism remains unclear. Based on Parker Solar Probe observations, this Letter investigates the occurrence of ion-scale waves in the near-Sun solar wind with heliocentric distances between 0.1 and 0.2 au. Results show that the occurrence rate of left-handed polarized waves significantly depends on the plasma beta ($β$) and cross helicity ($σ_c$). The occurrence rate rapidly increases with decreasing $β$ and increasing $σ_c$. Overall, the occurrence rate exceeds 45$\%$ when $β<0.2$ and $σ_c > 0.7$ are satisfied. These observations are consistent with the direct predictions of the helicity barrier theory that suggests the generation of ion cyclotron waves via imbalanced magnetized turbulence.

astro-ph.SR↗

arXiv2026

Turbulence Closure in RANS and Flow Inference around a Cylinder using PINNs and Sparse Experimental Data

Traditional Reynolds-averaged Navier-Stokes (RANS) closures, based on the Boussinesq eddy viscosity hypothesis and calibrated on canonical flows, often yield inaccurate predictions of both mean flow and turbulence statistics. Here, we consider flow past a circular cylinder over a range of Reynolds numbers (3,900-100,000) and Mach numbers (0-0.3), encompassing incompressible and weakly compressible regimes, with the goal of improving predictions of mean velocity and Reynolds forces. To this end, we assemble a cross-validated dataset comprising hydrodynamic particle image velocimetry (PIV) in a towing tank, aerodynamic PIV in a wind tunnel, and high-fidelity spectral element DNS and LES. Analysis of these data reveals a universal distribution of Reynolds stresses across the parameter space, which provides the foundation for a data-driven closure. We employ physics-informed neural networks (PINNs), trained with the unclosed RANS equations, to infer the velocity field and Reynolds-stress forcing from boundary information alone. The resulting closure, embedded in a forward PINN solver and the numerical solver OpenFOAM, significantly improves RANS predictions of both mean flow and turbulence statistics relative to conventional models.

physics.flu-dyn↗

arXiv2026

Radiation damage study of Belle II silicon strip sensors with 90 MeV electron irradiation

The silicon strip sensors of the Belle II silicon vertex detector were irradiated with 90 MeV electron beams up to an equivalent 1-MeV-neutron fluence of $3.0\times 10^{13}~{\rm n}_{\rm eq}/{\rm cm^2}$. We measure changes in sensor properties induced by radiation damage in the semiconductor bulk. Electrons around this energy are a major source of beam-induced background during Belle II operation. We discuss observed changes in full depletion voltage, sensor leakage current, noise, and charge collection. The sensor bulk type inverts at an equivalent 1-MeV-neutron fluence of $6.0\times 10^{12}~{\rm n}_{\rm eq}/{\rm cm^2}$. The leakage current increases proportionally to the radiation dose. We determine a damage constant of $3.9 \times 10^{-17}$ A/cm at 17 C$^\circ$ immediately after irradiation, which drops significantly to approximately 40% of the initial value in 200 hours, then stabilizes to approximately 30% of the initial value in 1000 hours. We measure sensor noise and signal charge for a sensor irradiated with the equivalent 1-MeV-neutron fluence of $3.0\times 10^{13}~{\rm n}_{\rm eq}/{\rm cm^2}$. Noise increases by approximately 44% after irradiation, while signal charge does not change significantly when a sufficiently high bias voltage is applied.

physics.ins-det↗

arXiv2026

HAWC Study on the Ultra-High-Energy Gamma-Ray Emissions from the Pulsar Wind Nebula G32.64+0.53

Multi-TeV gamma-ray emission around eHWC J1850+001 (a source from the first HAWC catalog of gamma-ray sources emitting above 56 TeV) is spatially coincident with the pulsar wind nebula (PWN) G32.64+0.53, powered by PSR J1849-0001. The absence of counterparts in radio, optical, and GeV energy ranges, contrasted with clear detections in X-rays and very-high-energy (VHE) gamma-rays, is indicative of a non-thermal leptonic origin for the nebula. We apply a systematic analysis pipeline, including a sophisticated model for the Galactic diffuse emission, to 2860 days of data from the HAWC Observatory. Our detailed analysis confirms that the ultra-high-energy (UHE) emission originates from G32.64+0.53, and we measure its spectrum up to 270 TeV with significant emission well beyond 100 TeV. We fit the multi-wavelength observations with a time-dependent leptonic model powered by the pulsar's rotational energy, and the results establish the nebula as a leptonic PeV accelerator, capable of accelerating electrons to a maximum energy of $E_{\mathrm{cut}}\geq2.9~\mathrm{PeV}$ (95\% one-sided lower bound). The model also constrains the nebular magnetic field to $4.28 ~\mathrm{μG}$, supporting a leptonic PWN origin for the observed UHE emission.

astro-ph.HE↗

arXiv2026

Electronic inhomogeneity in Cs- and Sb-terminated surfaces of CsV$_3$Sb$_5$ probed by scanning photoemission spectromicroscopy

Electronic structures of Cs- and Sb-terminated surfaces of a kagome superconductor CsV$_3$Sb$_5$ have been elucidated by means of scanning photoemission microscopy (SPEM). The observed band structure of the Cs-terminated surface is rather close to that of the bulk while that of the Sb-terminated one is substantially modified around K/H point of the Brillouin zone. While the contrast between the Cs- and Sb-terminated regions is reduced below the charge density wave transition temperature, the Sb 5$p$ band of Cs-terminated region exhibits electronic inhomogeneity which slightly increases below it. The inhomogeneity of the Sb 5$p$ band would be related to disorders of the out-of-plane Sb and relevant for the band folding along $Γ$-A with the charge density wave. The SPEM results suggest that the less inhomogeneous Cs termination is more suitable for interface of kagome superconductors. However, the inhomogeneity of Cs termination, which is significant at $Γ$/A, noticeable at K/H, and negligible at M/L, is expected to affect the Sb 5$p$-V 3$d$ hybridization at the interface.

cond-mat.supr-con↗

arXiv2026

High Multiplicity Trigger for Long-Lived Particles in CMS detector

Searches for long-lived particles (LLPs) at the CMS experiment often involve unconventional event topologies that are difficult to efficiently select using standard trigger strategies. To improve sensitivity to such signatures during LHC Run~3 operation, a dedicated High Multiplicity Trigger (HMT) has been developed and deployed in the CMS trigger system. The trigger targets events containing unusually large numbers of hits in the CMS cathode strip chamber (CSC) muon detectors, a characteristic signature of several LLP scenarios involving displaced decays in the muon system. The HMT implementation, trigger logic, rate dependence with pileup, and operational stability are described. Optimized hit multiplicity thresholds are used to maintain acceptable trigger rates under high-luminosity and high-pileup conditions while preserving high efficiency across a broad range of LLP lifetimes and kinematic regimes. The trigger performance is evaluated using both simulated event samples and proton-proton collision data collected during Run~3 of the LHC. The HMT substantially extends the CMS sensitivity to non-standard signatures associated with LLP decays and provides a flexible platform for future searches for physics beyond the Standard Model.

hep-ex↗

arXiv2026

The X-ray emission of the long-period transient and accreting cataclysmic variable ASKAP J174508.9-505149

Long-period transients (LPTs) challenge our knowledge of the mechanism producing radio periodic pulsations in compact objects. Some LPTs have been associated with systems hosting a white dwarf and a low-mass star in a detached binary. Recently, a new LPT (ASKAP\,J174508.9-505149) has been classified as an accreting cataclysmic variable (CV). In the present letter, we report on the detailed study of the X-ray variability of ASKAP\,J174508.9-505149 as observed by \emph{XMM-Newton} and \emph{Einstein Probe} between September 2025 and May 2026. Simultaneous optical and radio observations are also presented. We studied the timing variability of the source, and estimated an X-ray periodicity of $P=4868(22)$\,s, consistent with radio and optical periods. We also observe the same periodicity in the hardness ratio extracted from the \emph{XMM-Newton} observation, peaking at the minimum of the modulation. A long-term modulation is also present in the X-rays and in the B-band photometry, but it is poorly constrained by the current dataset. Spectral X-ray analysis shows the presence of a black-body component ($\sim$0.1\,keV), a collisionally ionised plasma ($\sim$15\,keV), and an absorption feature at 0.77 keV (possibly due to Oxygen-VII). This is the third LPT detected in the X-ray band, the second with a detected X-ray periodicity and variable X-ray emission, and the first conclusively recognised as an accreting magnetic CV.

astro-ph.HE↗

arXiv2026

Constraints on axion-like particles from ultra-high-energy observations of M87 with the HAWC observatory

In this work, we perform an indirect search for axion-like particles (ALPs) through their hypothesized mixing with photons in the presence of magnetic fields. ALPs are a well-motivated dark-matter candidate class, and the photon-ALP conversion mechanism provides a unique channel to constrain their mass and coupling constant using very-high-energy gamma-ray observations. The photon-ALP mixing could alter the observed gamma-ray spectrum from extragalactic sources by effectively reducing the apparent attenuation due to extragalactic-background-light absorption. We analyze 7.5 years of data from the High Altitude Water Cherenkov (HAWC) Observatory, targeting the nearby radio galaxy M87. This source is located within the Virgo cluster and is an ideal environment for photon-ALP conversion due to its low redshift and the large-scale, strongly magnetized medium of the cluster. We find no evidence for a photon-ALP conversion signal and, consequently, set constraints on the ALP mass and photon-ALP coupling constant with emission from M87 which are consistent with previous results. Our analysis places competitive constraints on the ALP parameter space, defining an exclusion region in the mass range of approximately $10^{-8}$ to $10^{-6}$ eV for coupling constants above $5\times10^{-12}$ GeV$^{-1}$, complementing previous constraints from other gamma-ray observatories.

astro-ph.HE↗

arXiv2026

First constraints on point-like astrophysical sources using Baikal-GVD muon neutrino events

Baikal-GVD is a new-generation neutrino telescope under final construction stages in Lake Baikal, Russia. With an instrumented volume already at 0.7 km$^3$, Baikal-GVD is currently the largest neutrino telescope in the Northern hemisphere. A sub-degree angular resolution, made possible thanks to high purity of Baikal water, further enhances Baikal-GVD sensitivity to cosmic neutrino sources. In this work, we employ track-like events collected from the partially completed detector between April 2019 and March 2024 to search for muon neutrino fluxes from 92 astrophysical objects of interest. For this, a $χ^2$-based track reconstruction method is used along with a cut-based analysis. The analysis uses upward-going muons only, providing coverage for declinations between -90$^\circ$ and +38$^\circ$. No significant excess has been found, so upper limits are reported. The obtained limits are competitive with those set by ANTARES and KM3NeT. We briefly comment on a possible low-significance indication of an excess from the direction of Westerlund 1. This work sets a major milestone on the way to full-scale scientific exploitation of Baikal-GVD data.

astro-ph.HE↗

arXiv2026

Cryogenic hydrogen embrittlement of 316plus (EN 1.4420) stainless steel at 77 K and 20 K

This paper presents the first experimental characterisation of combined hydrogen-temperature effects in 316plus (EN 1.4420), a new austenitic stainless steel for liquid hydrogen (LH2) storage. Uniaxial tensile tests were conducted at room temperature (RT), 77 K and 20 K on uncharged and hydrogen-precharged specimens, complemented by fractography and EBSD-based quantification of strain-induced martensite (SIM). 316plus exhibited cryogenic strengthening at 77 K and 20 K by enhanced SIM formation. Hydrogen did not influence strength at RT or 77 K and caused a modest decrease (~10%) at 20 K, keeping 316plus at the upper bound of cryogenic strength for 316L. The presence of hydrogen resulted in significant reductions in ductility at all temperatures, being most severe at 77 and 20K (~40-50%). Hydrogen suppressed SIM at 20 K, but SIM fraction did not correlate with ductility reduction. Despite the combined effect of temperature and hydrogen, 316plus retained notable ductility (reduction in area ~30%).

physics.chem-ph↗

arXiv2026

Search for TeV emission from spider millisecond pulsars with HAWC

Millisecond pulsars (MSPs) are observed to emit multi-wavelength radiation, from radio to GeV. Spider MSPs, which interact with their low-mass companion in close orbit (orbital periods $< 1$ day), may lead to strong intrabinary shocks that can further accelerate electron and positron pairs produced in the magnetosphere, possibly emitting very-high-energy (0.1--100 TeV; VHE) photons through inverse Compton scattering. Using 2565 days of HAWC Pass 5 data, we search for VHE emission from spider MSPs and present upper limits on individual sources. We also perform a stacking analysis to examine whether the two sets of spider systems, classified as redbacks and black widows depending on the companion mass, exhibit different spectral properties. Our study places constraints on TeV emission from MSPs and suggests that they are unlikely to contribute significantly to the Galactic diffuse emission at TeV and higher energies.

astro-ph.HE↗