The Second LHAASO Collaboration Conference in 2026 & The Academic Symposium for the 10th Anniversary of the LHAASO collaboration

We present a study of the γ-ray emission in the Kes 78 region using LHAASO observations. Our analysis reveals extended emission from LHAASO J1850−0004u, substantially larger than the supernova remnant, and identifies an additional point-like source, J1852−0003. Einstein Probe observations provide only an X-ray upper limit at the position of J1852−0003. Combining the LHAASO results with existing GeV measurements, we explore hadronic and leptonic interpretations. A scenario involving protons confined within and escaping from Kes 78 requires a relatively large target-gas mass to reproduce the extended TeV emission, motivating a possible additional contribution from massive-star winds. We also examine inverse-Compton models and assess their feasibility using X-ray constraints and pulsar energetics. The results constrain possible particle accelerators in this complex region, while the origin of the ultra-high-energy emission remains uncertain.

We report the first detection of TeV $\gamma$-ray emission from the region of the evolved supernova remnant (SNR) Simeis 147 (S147; G180.0$-$1.7) and its associated pulsar PSR J0538+2817, using 1484 days of LHAASO-WCDA observations and 1944 days of LHAASO-KM2A observations. The emission exhibits a clear energy-dependent morphology: the WCDA data favor a compact source plus an extended Gaussian component, whereas the KM2A emission above 25 TeV is consistent with a single compact source. A joint analysis resolves the emission into the compact source LHAASO J0538+2829 and the degree-scale extended source LHAASO J0539+2802. LHAASO J0538+2829 lies only $0.21^\circ$ from PSR J0538+2817 and is aligned with a recently discovered one-sided radio filament extending ahead of the pulsar. Accounting for both the source-localization uncertainty and this directional alignment, we estimate a local chance-coincidence probability of $0.34\%$, which decreases to $0.06\%$ for pulsars with $\dot{E}/d^2>10^{34}\ {\rm erg\,s^{-1}\,kpc^{-2}}$, favoring a pulsar-related origin. No significant 10 GeV--1 TeV counterpart is detected at the compact-source position, while XMM-Newton observations also yield only an upper limit, constraining leptonic models and implying $B\lesssim16~\mu{\rm G}$ for the adopted electron spectrum. For the extended component, an analysis of 18 years of Fermi-LAT data together with MWISP $^{12}$CO, CGPS $\mathrm{H\,I}$, and H$\alpha$ observations favors a CO+disk morphology. The GeV disk is separated from the gas-correlated emission and lies only $0.19^\circ$ from LHAASO J0539+2802, with its spectrum connecting naturally to the TeV measurements. These results reveal at least two physically distinct high-energy components in S147: a compact, likely pulsar-powered source possibly produced by collimated outflow or anisotropic particle escape, and an extended GeV--TeV component associated with the SNR environment.

Following our previous work on optimizing the analysis of LHAASO-KM2A full-array data at large zenith angles, we present preliminary results from a search for gamma-ray sources in the inner Galaxy, focusing on the W28, W30, and Galactic Center regions. These regions host various gamma-ray emission components, primarily associated with pulsar wind nebulae and interactions between high-energy cosmic rays and molecular clouds. We report several promising gamma-ray source candidates and present preliminary investigations of their spatial distributions and spectral properties. These results demonstrate the potential of large-zenith-angle observations with LHAASO-KM2A for studying particle acceleration and gamma-ray emission in the inner Galaxy.

We report the identification of a new ultra-high-energy (UHE) $\gamma$-ray source, designated LHAASO1907+0913, through a detailed analysis of LHAASO survey data. The source is clearly detected by both the WCDA and KM2A detectors with statistical significances of $8.8 \sigma$ and $5.5 \sigma$, respectively. The best-fit source position is determined to be R.A. = $286.85^\circ \pm 0.03^\circ $, Dec. = $9.22 \pm 0.03 ^\circ$. The measured differential flux from 1 to 110 TeV can be approximately described by a log-parabola model: $(2.10 \pm 0.35)\times10^{-16} \left(\frac{E}{20 \,{\rm TeV}}\right)^{-(3.10\pm0.13) - (0.45\pm0.16)\ln\left(\frac{E}{20.0}\right)}$. The parent particle spectrum inferred from the radiative model cannot be naturally explained within a purely hadronic scenario. Combined with the significant energy deficit of PSR J1907+0918, we conclude that the Galactic magnetar SGR 1900+14 is the most plausible counterpart and the likely accelerator responsible for the UHE $\gamma$-ray emission of LHAASO1907+0913.

The ultrahigh-energy gamma-ray source LHAASO J1912+1013, designated 1LHAASO J1912+1014u in the first LHAASO catalog and detected by H.E.S.S. as HESS J1912+101, lies near the middle-aged pulsar PSR J1913+1011 and is an important target for studying Galactic cosmic-ray acceleration and propagation. We analyze LHAASO observations from 2021 March 5 to 2025 July 31 and Fermi--LAT data from 2008 August 4 to 2026 January 12 to investigate its morphology, spectrum, and possible radiation mechanisms. The LHAASO analysis reveals highly significant gamma-ray excesses in both the WCDA and KM2A energy ranges, with source-detection significances of $32.35\sigma$ and $13.63\sigma$, respectively. The emission is also significantly spatially extended in both energy ranges. The best-fit Gaussian extension radii, expressed as 68% containment radii, are $R_{68}=0.448\pm0.019^\circ$ for WCDA and $R_{68}=0.511\pm0.046^\circ$ for KM2A. Their best-fit centroids are $(\mathrm{R.A.},\mathrm{decl.})=((288.21\pm0.02)^\circ,(10.17\pm0.02)^\circ)$ and $((288.17\pm0.04)^\circ,(10.30\pm0.04)^\circ)$, respectively. The WCDA spectrum is described by a power law with an exponential cutoff, with a photon index of $2.02\pm0.23$ and a cutoff energy of $7.65\pm2.85~\mathrm{TeV}$, while the KM2A spectrum is described by a power law with a photon index of $3.69\pm0.15$. Analysis of 10--500 GeV \textit{Fermi}--LAT events shows that 4FGL J1913.3+1019 is also extended at $10.14\sigma$. A uniform-disk model gives a centroid of $((288.38\pm0.04)^\circ,(10.34\pm0.04)^\circ)$ and a radius of $0.84\pm0.02^\circ$. Its spectrum is described by a power law with a photon index of $2.17\pm0.26$. Broadband modeling from 30~GeV to 1 PeV shows that both leptonic and hadronic scenarios can reproduce the observed emission. We identify a spectral point with $\mathrm{TS}=4.4$ in the 1000--1585 TeV KM2A bin. Its robustness requires further assessment, particularly accounting for systematic uncertainties from Galactic diffuse emission, instrumental exposure, and the cosmic-ray background.

Recently, LHAASO detected variable gamma-ray emission above 100 TeV from the gamma-ray binary LS I +61 303. We attempt to fit several gamma-ray binaries with a colliding pulsar wind binary model to determine whether the gamma-ray spectra above 100 TeV can be explained.

Following recent LHAASO study of microquasars, we conducted a search for gamma-ray emission from black hole X-ray binaries. Utilizing the BLACKCAT catalog of stellar-mass black hole X-ray binaries candidates and excluding the sources already analyzed in previous LHAASO microquasar study, we performed a detailed analysis of the remaining sources.

Binary systems can accelerate particles to the TeV energy range, thereby producing TeV radiation. Currently, tens of binary systems have been detected in the TeV band. Here, we report on the massive X-ray binary XTE J1858+034—a symbiotic system composed of an X-ray pulsar and a K–M type late-stage companion—located at the central position of the TeV source LHAASO J1858+0330, with an angular separation of only 0.13°. The LHAASO J1858+0330 source exhibits an extended structure of 0.52°. If there is a physical association between LHAASO and the binary system, this extension may imply the presence of an 80-pc-scale bubble or halo associated with this HMXB.

修改后的摘要：
W41 is an evolved supernova remnant embedded in a complex molecular environment, with extended GeV–TeV emission confirmed by multiple observations. The magnetar Swift J1834.9−0846, projected near the remnant’s center, is surrounded by relatively steady, asymmetric, nonthermal X-ray emission that supports a magnetar wind nebula interpretation. Energetic electrons and positrons in this nebula could contribute to the central very-high-energy excess of HESS J1834−087 through inverse-Compton scattering. However, the nebula’s energy-injection history, the magnetar’s physical association with W41, and the proposed connection to the TeV emission remain uncertain. LHAASO detects extended emission in this direction at local significances of approximately 8.9σ with WCDA in the 1–25 TeV band and 7.3σ with KM2A above 25 TeV, with respective two-dimensional Gaussian widths of σ = 0.395° ± 0.068° and 0.399° ± 0.070°. The northward-displaced best-fit centroids and larger spatial extent of the LHAASO emission do not establish an unambiguous association with the central magnetar wind nebula. The relative contributions of the supernova remnant and the magnetar wind nebula to the observed gamma-ray emission remain to be determined.

LHAASO has reported orbital modulation of PeV gamma-ray emission from Cygnus X-3. We revised the calculaiton for anisotropic scatterings and jointly fit Fermi-LAT GeV and LHAASO PeV data with a shared jet geometry model, allowing different emission heights, to test whether both modulations can be explained in the same framework.

Gamma-ray observations have established energetic isolated pulsars as outstanding particle accelerators and antimatter factories. However, many questions are still open regarding the acceleration and radiation processes involved, as well as the locations where they occur. The radiation spectra of all gamma-ray pulsars observed to date show strong break above energies of a few GeV. LHAASO may reveal the highest pulsation component from pulsars. Furthermore, they pave the way for investigating pulsars through their TeV emission, thereby imposing additional constraints on the acceleration and emission processes in their extreme energy limit.

The evolved star IRAS 18443−0231, which exhibits nonthermal radio jets, is a candidate counterpart to the GeV source 4FGL J1846.9−0227 and offers an opportunity to explore a potential new class of TeV emitters. We perform a joint morphological and spectral analysis of an 8°×8° region using LHAASO-WCDA and KM2A data, incorporating multiwavelength information to investigate the emission origin. Preliminary fits yield a regional test statistic of TS≈124. After accounting for nearby catalogued sources, the northern peak in the point-source TS scan above 25 TeV lies close to IRAS and the Fermi-LAT source, whereas the southern emission may include a contribution from the Kes75 pulsar wind nebula. The regional detection does not establish an independent association with IRAS, and the signal above 100 TeV remains insufficient to identify its counterpart. Further analysis with consistent spectral models and constraints on neighbouring sources and diffuse backgrounds will test whether an additional component at the IRAS position is required. Jet energetics and particle acceleration constraints will then assess the feasibility of TeV emission from this evolved stellar system.

In this work, we report a newly identified ultra-high-energy (UHE) $\gamma$-ray source, designated LHAASO J2200+5643, based on a detailed analysis of about 4 years of LHAASO survey observations. LHAASO J2200+5643 is an extended source detected by LHAASO, with a significance of $35.76\sigma$. The best-fit position of this source is (R.A. = $330.18\pm 0.04^\circ$, Decl. = $56.7251\pm 0.02^\circ$), with a corresponding angular size ($r_{39}$) of $0.52\pm0.02^\circ$. The differential flux of this UHE (\gamma)-ray source can be described by a power-law with exponential cutoff model: $ (1.32 \pm 0.05)\times10^{-14} \left(\frac{E}{10 TeV}\right)^{-(1.85\pm0.03)} \exp\left(-\frac{E}{42.4\pm1.5}\right).$ A potential shell-type SNR candidate, G100.97+1.57, is the only known cosmic-ray accelerator in this region. Our analysis of molecular cloud distributions using MWISP survey data reveals a $^{12}$CO clump component at the center of LHAASO J2200+5643. In this context, we suggest that LHAASO J2200+5643 arises from cosmic rays escaping from the SNR G100.97+1.57 at a distance of roughly 4.5 kpc, which illuminate the adjacent molecular cloud.

To search for the association between high‑energy neutrinos and Galactic compact objects near the Galactic plane, we select IceCube neutrino alert events after 2021 within the Galactic latitude $|b|\le 15^\circ$. We find that the neutrino alert IC250813A is spatially coincident with the microquasar MAXI J1820+070. This black‑hole X‑ray binary hosts a relativistic jet, which has long been proposed as a promising site for Galactic high‑energy neutrino production. To investigate the physical connection between IC250813A and the jet activity of MAXI J1820+070, we analyze LHAASO observations and study the very‑high‑energy gamma‑ray light curve around the neutrino alert time. Combining the neutrino localization, archival X‑ray monitoring, and LHAASO light‑curve data, we discuss possible particle acceleration and neutrino production inside the jet of this black‑hole binary. This source serves as an interesting candidate case for understanding multi‑messenger emission from Galactic microquasars.

Black hole X-ray binaries are promising sites for particle acceleration, where accretion flows, relativistic jets, and compact-object environments may produce high-energy non-thermal emission. While individual systems may be too faint to be detected significantly at TeV energies, a stacking analysis can enhance sensitivity to weak emission shared by the source population.
In this work, we perform a stacking search for TeV gamma-ray emission from a sample of black hole X-ray binary candidates using LHAASO WCDA and KM2A data. The analysis is carried out within the Gammapy framework, enabling likelihood-based modeling of each sky region. For each candidate, the surrounding field is modeled with known LHAASO sources, Galactic diffuse emission, and instrumental background. We then test for an additional gamma-ray component at the position of each black hole X-ray binary and combine the likelihood information from the full sample to search for a collective signal. The analysis will provide constraints on the collective high-energy emission from black hole X-ray binaries and help assess their role as potential Galactic particle accelerators.

The supernova remnant (SNR) G150.3+4.5 was first discovered in the radio band, which has a shell-like structure with an angular radius of approximately 1.5°. It has attracted considerable interest because of its complex surroundings, including a low-density cavity and nearby molecular clouds. We present a spatially resolved GeV–TeV study of this remnant using approximately 17 years of Fermi-LAT observations from 200 MeV to 1 TeV and LHAASO Pass 5 data above 1 TeV. Motivated by the TeV morphology, we construct separate northern and southern spatial templates to investigate regional differences in gamma-ray emission. We also incorporate multi-frequency radio measurements and ROSAT All-Sky Survey X-ray constraints into broadband spectral modeling. The northern region shows a hard GeV spectrum, with a photon index of approximately 1.4 below a spectral break, whereas the southern region has a softer spectrum with an index of approximately 1.9. The broadband emission is consistent with a predominantly leptonic inverse-Compton origin in the north and a hadronic component associated with nearby molecular gas in the south. Within the adopted emission model, the radio and X-ray constraints imply a magnetic field of approximately 8.7 μG, while the proton spectrum has a cutoff energy of approximately 280 TeV. These results suggest distinct particle populations and gamma-ray production processes across G150.3+4.5, highlighting the value of spatially resolved GeV–TeV observations for investigating particle acceleration and escape in evolved SNRs.

Gamma-ray binaries are rare systems composed of a massive star and a compact object, most likely a neutron star or black hole, in which the interaction between the compact object and the stellar wind of its companion gives rise to variable, orbitally-modulated high-energy emission. Only a handful of such systems are currently known to emit at TeV energies, making them unique laboratories for studying particle acceleration under extreme, periodically changing conditions. In this poster, I will present observations of the gamma-ray binary HESS J0632+057 with LHAASO.

HESS J0632+057 is one of the few confirmed TeV-emitting gamma-ray binaries, consisting of a Be-type star and a compact object in a highly eccentric orbit. Its gamma-ray emission varies strongly with orbital phase, believed to arise from the interaction between the compact object and the dense, variable wind and circumstellar disk of its companion. I will present our updated morphological and spectral analysis of HESS J0632+057 using joint LHAASO-WCDA and KM2A data, along with the orbital phase-resolved light curve constructed from this dataset. Careful treatment of the diffuse Galactic emission in the source region was essential given its location near the Galactic plane.

These results contribute to a broader effort to build a consistent, uniformly analyzed sample of Galactic gamma-ray binaries with LHAASO, helping to establish how particle acceleration proceeds in these compact, periodically variable systems and how they fit among the Galaxy's high-energy particle accelerators.

The discovery of twelve ultra-high-energy (UHE) gamma-ray sources by LHAASO opened a new window on the Universe above 100 TeV. The subsequent release of the first LHAASO source catalog (1LHAASO) further expanded the known population of UHE gamma-ray emitters. Building on these achievements, we are conducting a systematic search for gamma-ray sources above 100 TeV using LHAASO-KM2A data, with the aim of constructing a dedicated UHE gamma-ray source catalog. This work will provide a systematic characterization of Galactic UHE gamma-ray sources and their spatial and spectral properties, offering new insights into the diverse populations of extreme particle accelerators in our Galaxy and the origin of Galactic cosmic rays.

我们引入了一种通过神经网络对LHAASO KM2A天图进行降噪并寻找到更多弱源的的方法. 我们用真实的无源天区作为训练数据, 利用大模型学习天图数据中的时空关联信息, 进而抑制天图中的统计涨落波动. 因为源的形状可以较好的呈现在降噪后的天图中, 我们提出了一种考虑源形状的似然函数以更好地评估显著性, 并基于样本统计分布得到了最终的显著性天图. 我们通过短期数据验证了这套算法发现的弱源的正确性, 并在可靠性不变的前提下, 相比传统方法多发现了若干 5σ 源. 此外, 这套降噪方法还可以用于在复杂源区对多个扩展源成分进行分离拟合.

Motivated by the discovery of very-high-energy (VHE) emission from the low-luminosity AGN NGC 4278, we performed a systematic search for VHE emission from low-luminosity AGNs (LLAGNs). For each source we searched for both a cumulative excess and a time-variable signal; as no significant excess was found, we further carried out a stacking analysis of the LLAGN sample, which likewise yielded no significant excess. These results are of value for understanding the radiation mechanisms of LLAGNs and their contribution to ultra-high-energy neutrinos and extra-high-energy cosmic rays.

Lower bounds on intergalactic magnetic field (IGMF) have been previously derived from gamma-ray data on extreme blazars. These bounds suffer from uncertainty related to the absence of regularly sampled measurements of time-average blazar TeV band spectra.
We use LHAASO telescope to infer time-average TeV band spectrum of an extreme blazar 1ES 1218+304 and derive a lower bound on IGMF from gamma-ray observations of this source.
We consider LHAASO exposure spanning four years to measure time average source flux in the multi-TeV energy range. This measurement allows us to predict the flux of secondary emission in the GeV energy range, produced by electrons and positrons deposited in intergalactic medium by TeV gamma-ray interactions. We use Fermi Large Area Telescope to search for this secondary GeV flux. We find that the secondary GeV flux has to be suppressed by deflections of electrons and positrons by magnetic field of strength at least $3.7\times 10^{-18}$ G, if the field correlation length $\lambda>1$ Mpc and time-delay $t_d<10$ yr, while longer time-delays allow stronger bounds. These lower bounds on the field strength improve as $\lambda^{-1/2}$ if the field correlation length is shorter than 1 Mpc. The lower bounds are valid under the assumption that the time-average TeV source flux measured by LHAASO is representative for the source flux over a much longer mega-year blazar activity time span.

A Possible Star-Forming Origin of the Ultrahigh-Energy Gamma-Ray Source 1LHAASO J1814−1636u

Massive star-forming regions are promising sites of Galactic cosmic-ray acceleration to PeV energies. To investigate their connection with ultrahigh-energy gamma-ray emission, we examine the environment of 1LHAASO J1814−1636u, detected above 100 TeV at approximately 7σ, and its possible association with the star-forming complex G13.875+0.282.

The Einstein Probe Wide-field X-ray Telescope (WXT) survey reveals an extended soft X-ray structure with a radius of approximately 20 arcmin. Its center lies about 0.3° from the LHAASO gamma-ray centroid, and the structure partially overlaps the >100 TeV emission. Complementary FUGIN ¹²CO(J = 1–0) observations reveal strong molecular emission near a local-standard-of-rest velocity of +50 km s⁻¹, peaking at the center of the >100 TeV emission and the position of the embedded infrared cluster [BDS2003] 116. Located at approximately 3.9 kpc, the cluster is associated with G13.875+0.282, also known as IRAS 18116−1646. Numerous H II regions, masers, infrared bubbles, and young stellar object candidates in the surrounding field further indicate active star formation. The coincidence of the star-forming complex and molecular cloud with the gamma-ray emission suggests a possible association, with the gas providing a potential target for interactions with accelerated cosmic-ray protons.

To investigate this possibility, we have applied for Gemini infrared observations to search for massive stars in the complex, together with XMM-Newton observations to search for possible X-ray counterparts and clarify the nature of the extended soft X-ray emission. Combined with further LHAASO morphological and spectral analyses and broadband modeling, these proposed observations would help test whether the star-forming complex contributes to the >100 TeV emission and constrain the underlying acceleration and radiation mechanisms.

This is a preliminary LHAASO-WCDA analysis of the high-synchrotron-peaked BL Lac object 1ES 1218+304. Using data collected from March 2021 to July 2025, we construct an eight-day light curve, significance maps, and a time-averaged spectral energy distribution (SED), while considering possible source confusion from the nearby 1ES 1215+303 and NGC 4278. The signal is strongest in the low-$N_{\rm hit}$ bins. A Bayesian Blocks analysis of the current weighted light curve finds no clear, statistically significant change point. We describe the observed spectrum with a power law with an exponential cutoff fixed at 10 TeV. And we get the intrinsic spectrum with Saldana-Lopez's EBL model.

The Hubble constant is of paramount importance in astrophysics and cosmology. The precise determination of the Hubble constant is one of the critical problems in modern cosmology. In this poster, we present our preliminary results on measuring the Hubble constant using extragalactic sources observed by LHAASO and Fermi-LAT. By combining observations across a broad energy range, we aim to investigate the potential of gamma-ray observations to constrain the Hubble constant.

Good angular resolution is essential for resolving the fine structures of gamma-ray sources and improving detection sensitivity, and is therefore crucial for gamma-ray source observations. We present a Transformer-based deep learning model for gamma-ray direction reconstruction. Using six months of Crab Nebula observations, this method improves the angular resolution compared with traditional methods. To further improve the angular resolution, we introduce shower-core position reconstruction and systematically compare the angular resolution achieved with single-task learning (direction reconstruction only) and multi-task learning (joint direction and shower-core position reconstruction).

This poster carries out parallel optimization for the G4KM2A cosmic ray simulation program based on the Paralux heterogeneous parallel scheduling technology. The optimization significantly improves the simulation efficiency of high energy cosmic ray events.

Radio-quiet active galactic nuclei (AGNs) have recently emerged as a potential population of high-energy gamma-ray emitters. Using 15 years of Fermi-LAT observations, we previously reported a significant stacked gamma-ray signal from a sample of nearby, hard-X-ray-bright radio-quiet AGNs, revealing their average spectral energy distribution (SED) up to hundreds of GeV. However, their emission at TeV energies remains largely unexplored, leaving the high-energy behavior of the gamma-ray spectrum and the maximum energy of accelerated particles poorly constrained.

In this work, we extend the study of this radio-quiet AGN population to the TeV regime using LHAASO observations. We perform a stacking analysis of the LHAASO data and constrain the characteristic gamma-ray flux and spectral shape at TeV energies. In the $1$-$20\,\mathrm{TeV}$ band, the combined likelihood shows a moderate excess with a maximum test statistic of $\mathrm{TS}\simeq 6.5$. The corresponding characteristic luminosity is $L_{1\text{-}20\,\mathrm{TeV}}\simeq 4.8\times10^{39}\,\mathrm{erg\,s^{-1}}$. Although the current significance is insufficient to claim a detection, the LHAASO measurement provides a new constraint on the average TeV emission of radio-quiet AGNs.

By combining the LHAASO constraints with the previously measured Fermi-LAT spectrum, we construct a broadband GeV-TeV SED for radio-quiet AGNs. The results probe the suppression of their gamma-ray emission beyond the Fermi-LAT energy range and provide new constraints on the high-energy cutoff and the maximum energies of non-thermal particles.

Using the All-sky Root around in an Unbiased way (ARU) software, we search or transients within the daily-integrated LHAASO-WCDA maps. This approach has the advantage that does not require to assume a functional form of the observed data or the diffuse emissions from the galaxy. We show the results for Mrk 421 and NGC 1275 as for other variable galactic sources.

Using the publicly available observational data from LHAASO, we conducted a detailed study of the gamma-ray emission properties of the source 1858+0330 in the TeV energy range. This analysis utilizes the latest data set: for the Water Cherenkov Detector Array (WCDA, using the Cod version data covering 1–25 TeV and divided into 7 energy bins), the observation period is from March 5, 2021 to July 31, 2025, with a total exposure of approximately 1484 days; for the Kilometer Square Array (KM2A, using data processed with charged particle screening (CPC cut) covering energies above 25 TeV), the observation period extends to January 31, 2026, with a total exposure of approximately 1572 days. Using a multi-component likelihood fitting method, we subtracted the isotropic background and diffuse gamma-ray templates to fit the spatial morphology and energy spectrum of the source, thereby obtaining the gamma-ray emission spectrum of 1858+0330 in the TeV range. The results reveal distinct radiative properties across different energy bands, with the WCDA and KM2A data connecting smoothly at the transition energy. This study provides important insights for understanding the radiation mechanisms and the nature of very-high-energy gamma-ray emission from this source.

We search for very-high-energy gamma-ray emission from M31 using LHAASO data, covering 0.63–10 TeV with WCDA and 25–2500 TeV with KM2A. With two spatial models, a point source and an HI gas template, we find no significant signal and derive 95% confidence level flux upper limits in individual energy bins. At a distance of 780 kpc, the point-source limits correspond to luminosities of order 10³⁵–10³⁷ erg s⁻¹, exceeding our estimate of the Milky Way TeV luminosity (diffuse emission plus the 1LHAASO UHE sources) by factors of 1.4–24. That benchmark is only a rough estimate — the emissivity per hydrogen atom times the total number of hydrogen atoms and is sensitive to the dust-opacity calibration, the assumed gas distribution, the unaccounted CO-dark and ionized gas, and the masking of the diffuse measurement. Its uncertainty is comparable to the gap above, so the comparison cannot yet establish whether M31 has a cosmic-ray content similar to that of the Milky Way.

X-ray binaries are well established gamma-ray sources. 1LHAASO J1902+0648 is a ultra high energy gamma-ray source detected by LHAASO. It is spatially associated with GeV source 4FGL J1902.5+0654 which recently has been identified as a binary. In this talk, we present recent LHAASO analysis of 1LHAASO J1902+0648 as well as the search for its multi-wavelength counterpart.

Cyg X-3 holds a special place in the history of high-energy astrophysics. Four decades ago, this compact binary was reported as a source of TeV and PeV gamma rays. Although these early reports remained controversial and unconfirmed, they significantly drove the development of ground-based gamma-ray astronomy. LHAASO's discovery of UHE gamma rays from Cyg X-3 shows that this system hosts a powerful hadronic super-PeVatron. Cyg X-3 is unique among known UHE gamma-ray sources because it combines two exceptional ingredients: a relativistic jet with a mechanical luminosity approaching 1039 erg/s and a Wolf–Rayet companion with an equivalent radiative luminosity. The jet provides the power required to accelerate protons to tens of PeV, while the intense stellar radiation supplies an efficient target for photo-meson production. Only a small fraction of the accelerated protons interact within the binary system; the remainder escape into the interstellar medium, diffuse through the surrounding gas, and produce a UHE halo via proton-proton interactions. This mechanism may readily account for the Cygnus Bubble's highest-energy component.

Recent LHAASO observations reveal ultrahigh-energy (UHE) gamma-ray emission from Cygnus X-3 with evidence for orbital modulation, providing a rare opportunity to study particle acceleration and transport on binary scales. We develop a common binary-jet model that jointly explains the contemporaneous GeV-PeV spectra and orbital light curves. The GeV emission is produced by anisotropic inverse-Compton scattering of stellar photons by relativistic electrons, while multi-PeV protons escaping from the inner region produce TeV-PeV gamma rays through photohadronic and hadronuclear interactions. The GeV orbital modulation constrains the binary-jet geometry, allowing the UHE observations to probe the escaping proton population and its interaction with the circum-binary environment. We find that the UHE emission is strongly regulated by the accretion-driven wind structure. In the present state, a fast disk wind displaces much of the denser Wolf-Rayet (WR) wind from the escaping-proton trajectories, suppressing hadronuclear emission. Changes in the strength, collimation, or orientation of the disk wind can expose the escaping protons to a much denser WR wind and enhance the PeV gamma-ray luminosity by orders of magnitude. This provides a possible connection to the much brighter, though unconfirmed, PeV activity reported in the 1980s, and links UHE gamma-ray activity to the accretion and outflow state of the binary.

White dwarf (WD) tidal disruption events (TDEs) provide a powerful and pristine "smoking-gun" signature for locating otherwise elusive intermediate-mass black holes (IMBHs). In this talk, I will present a comprehensive, steady-state accretion-disk model designed for these highly super-Eddington systems, where fallback rates can skyrocket to $10^5$ to $10^9$ times higher than standard main-sequence TDEs. We model the newly formed central engine by incorporating advanced high-energy physics, including nuclear burning, magnetic pressure, and advection-dominated flows regulated by powerful disk winds. Going beyond the disk, we couple this engine with the microphysics governing relativistic jets to explore nonthermal particle acceleration, high-energy neutrinos, and cosmic rays. We deliver the first joint predictions for the resulting multi-messenger emissions—spanning both thermal and nonthermal electromagnetic spectra, MeV-to-high-energy neutrino channels, cosmic-ray contributions, and low-frequency gravitational wave bursts (~0.1-1 Hz) tailored for next-generation decihertz space observatories. Finally, I will apply this grand unified framework to interpret the recently discovered fast X-ray transient EP250702a, demonstrating how its multi-wavelength evolution unveils the physics of super-Eddington accretion and jet formation around an IMBH.

We first iterated over different regions and updated the latest source catalog. We then constructed templates for different annuli and inferred the diffuse gamma-ray flux in each annulus through likelihood fitting. In addition, we attempted to fit the X_CO factor for different annuli.

We report a measurement of the Galactic diffuse gamma-ray emission at Galactic Ridge with LHAASO-KM2A. Building on the optimized event-reconstruction and data-selection framework for zenith angles of 40°–60°, we significantly improve the energy and angular resolution and the cosmic-ray background estimation, thereby extending the KM2A diffuse measurement to the previously inaccessible southern sky. Using a three-dimensional likelihood fit in which the diffuse emission is assumed to follow the Planck dust distribution, we detect diffuse emission in the region 0° ≤ l ≤ 20°, −2° ≤ b ≤ 2° above 100 TeV with a significance > 5σ.

We report on the LHAASO-WCDA real-time monitoring system, which consists of two parallel monitoring strategies working in synergy to catch TeV flares: an all-sky blind search, which requires no prior source list, and a targeted monitoring of 154 AGNs. Both strategies scan the data with sliding time windows, search for the maximum significance at each position or source, and issue alerts once toy-MC-calibrated thresholds are exceeded. Both systems are now routinely producing results and have revealed multiple extragalactic flaring episodes, including the recent flares of NGC 1275 and 1ES 1959+650. In addition, an independent follow-up system continuously ingests alerts from GCN and ATel, parses them automatically, and performs rapid analyses of alert positions. All monitoring products — daily summaries, flare reports, interactive light curves, and follow-up results — are collected on a dedicated monitor website, currently used internally within the collaboration and to be officially released soon.

The high-statistics cosmic-ray observations of LHAASO-KM2A enable daily studies of the cosmic-ray Sun shadow. Observations in 2022 reveal periodic variations in the Sun-shadow deficit that are consistent with those of contemporaneous solar activity. To explain this behavior, we construct the coronal magnetic field using HMI photospheric magnetic-field data and the PFSS/outflow model, and perform G4Solar-based particle back-tracking simulations to reconstruct the Sun shadow and its daily evolution. By comparing the simulations with LHAASO-KM2A observations, we explain the magnetic origin of the deficit variations and establish their relationship with solar active regions characterized by strong photospheric magnetic fields. Our results show that the modulation of cosmic-ray propagation by magnetic fields associated with these active regions is key to understanding the periodic variations in the Sun-shadow deficit, providing a basis for probing solar magnetic fields and their evolution through daily Sun-shadow observations.

The Large High Altitude Air Shower Observatory (LHAASO), owing to its high altitude and large active area, is suitable for studying the effects of thunderstorms on cosmic ray air showers. In this work, the variations of shower events during a thunderstorm on May 27, 2025 were investigated by analyzing the data from KM2A (1.3 km², the largest sub-array of LHAASO). The results show that the shower rate significantly increased during thunderstorms, with a maximum enhancement exceeding 40% (1s/bin). Furthermore, the variations were strongly dependent on the primary zenith angle and the shower size. During the thunderstorm, the average zenith angle decreased, while the average shower size increased. Due to the acceleration/deceleration and deflection by the atmospheric electric field (AEF) within thundercloud, the number of secondary particles with energy above the detector threshold was changed. Meanwhile, the spatial distribution of secondary particles in shower events broadened, with greater amplitudes for larger zenith angles. This leads to different variation behaviors of the shower event at different zenith angles in the KM2A. According to our study, multiple thunderstorm ground enhancements were detected during negative or positive near-earth electric fields, and then terminated by nearby lightning strikes (which weaken the electric field within thundercloud). To understand the experimental phenomena, Monte Carlo simulations were performed with CORSIKA and G4KM2A (a code based on GEANT4). A simplified electric field model was employed. Assuming a uniform electric field of -1500 V/cm in the intracloud region with a layer thickness of 1000 m (extending from 5610 to 4610 m) and - 250 V/cm in the near- earth layer at an altitude from 4610 to 4410 m, the simulation results were consistent with the average variation behaviors in the experiment.

The absence of cosmic ray flux data with known energy and composition in the high-energy range makes it impossible to perform a direct absolute calibration of the energy scale for ground-based cosmic ray experiments. This leads to a discrepancy between the measured cosmic ray energy and its true energy, which affects not only the fine structure of the cosmic ray spectrum but also the absolute flux of the energy spectrum. The Moon shadow formed by cosmic rays blocked by the Moon will experience a westward shift due to the magnetic field between the Earth and the Moon. The magnitude of this shift is inversely proportional to the energy of the cosmic rays and directly proportional to their charge. Consequently, the Moon shadow shift can be utilized to calibrate the absolute energy scale of ground-based cosmic ray experiments. However, at 100 TeV, the westward shift of protons and helium nuclei, which make up the majority of cosmic rays, is too small compared to the pointing accuracy of the detectors, making the measurement of the shift at energies above 100 TeV with large systematic uncertainty. This work proposes a method for calibrating the absolute energy of cosmic rays at 100 TeV using the Moon shadow formed by irons and estimates the capability of LHAASO to measure the iron Moon shadow.

The energy spectra and mass composition of cosmic rays are key observables for understanding the origin, acceleration, and propagation of Galactic cosmic rays. Recent space-based experiments, including AMS-02 and DAMPE, have provided high-precision direct measurements of proton, helium, and heavier-nuclei spectra, while LHAASO has extended composition-sensitive measurements into the PeV knee region.

We construct an empirical multi-component cosmic-ray model over a broad energy range by combining recent space-based measurements with LHAASO results. The model consists of five representative mass groups: protons, helium, the C group, the Mg group, and the Fe group. Measurements reported in different energy variables are consistently converted to total energy per nucleus. At low energies, the model is constrained primarily by AMS-02, DAMPE, and NUCLEON data. From several hundred TeV to PeV energies, the proton and helium spectra are directly constrained by recent LHAASO measurements, while the intermediate-mass and heavy components are jointly constrained by the LHAASO all-particle spectrum and mean logarithmic mass, . At higher energies, spectral shapes from the Global Spline Fit (GSF) model are adopted, with each mass group independently normalized at its transition energy to ensure flux continuity. The resulting all-particle spectrum and mean logarithmic mass are in good agreement with LHAASO measurements, providing a unified cosmic-ray input model for air-shower simulations and composition-dependent analyses.

LHAASO is a composite cosmic ray observatory comprising KM2A, WCDA, and WFCTA detector arrays. One of the core scientific goals is to precisely measure the energy spectra of individual cosmic ray components, establish a bridge between space-borne and ground-based experiments to constrain the origin, acceleration, and propagation mechanisms of cosmic rays. This work presents the joint measurement of proton fluxes around 100 TeV using DAMPE and LHAASO. By operating six WFCTA telescopes at a zenith angle of 8° in hybrid mode with KM2A, the energy threshold is lowered to ~50 TeV. Energy reconstruction combines the Cherenkov photons from WFCTA and the muon count from KM2A, achieving a resolution better than 20%. High-purity proton samples are selected via composition-sensitive parameters, achieving an efficiency of 25% and a purity of approximately 85%. The resulting proton spectrum from 50–400 TeV exhibits a clear and smooth hardening around 100 TeV.

In the 5–300 PeV energy range, the iron nuclear spectrum—particularly above 10 PeV—suffers from large systematic uncertainties arising from hadronic interaction models. We aim to identify a selection variable that exhibits weak dependence on hadronic models to reduce these systematic errors. Existing studies have shown that the lateral azimuthal fluctuation characteristics of showers are minimally affected by hadronic models, demonstrating the potential to reduce systematic uncertainties. The LCm analysis method, based on this concept, has been validated through both simulations and experimental data at the KASCADE experiment. However, due to significant differences in array geometry, detector spacing, and trigger conditions between KASCADE and KM2A, KASCADE's analysis parameters, selection criteria, and fitting procedures cannot be directly transferred. Currently, an LCm-based multivariate discrimination and spectrum unfolding pipeline adapted to the KM2A array has not yet been established, nor is there a systematic error evaluation framework for this method. This project aims to develop an LCm-PCA heavy-nuclei discrimination and spectrum unfolding method tailored to KM2A, combining shower fluctuation features, multivariate dimensionality reduction, and two-dimensional template fitting techniques to reduce the reliance of traditional analyses on hadronic interaction models.

The energy reconstruction of LHAASO-KM2A relies on the electron and muon content of extensive air showers and is therefore sensitive to the hadronic interaction model. We compare proton- and iron-induced showers simulated with CORSIKA 7.4010/EPOS-LHC and CORSIKA 7.8050/EPOS-LHC-R in the energy range 100 TeV–100 PeV, matched in primary energy and zenith angle and analysed with a KM2A-like particle selection.

Compared with the EPOS-LHC configuration, the EPOS-LHC-R configuration predicts 2–6% fewer electrons on average, with a reduction of up to 13% for protons at 100 PeV, while the muon content increases by approximately 9% for iron and 3% for protons. These differences correspond to estimated energy-scale shifts ranging from +12% for iron at 100 TeV to −12% for protons at 100 PeV. These energy- and composition-dependent shifts affect both the normalization and the shape of the reconstructed cosmic-ray spectra. For a power-law spectrum with a spectral index of 2.7, a uniform 12% energy-scale shift corresponds to a flux change of approximately 20%. Our results quantify the sensitivity of KM2A energy reconstruction to the simulation configuration and provide an estimate of the resulting systematic uncertainty in the all-particle and light-component cosmic-ray spectra.

Muon production depth (MPD) and its maximum, $X_{\text{max}}^{\mu}$, provide information on the mass composition of primary cosmic rays. Using timing information from LHAASO-KM2A muon detectors, we reconstruct MPD distributions for proton- and iron-induced air showers simulated with CORSIKA using three high-energy hadronic interaction models: EPOS-LHC-R, QGSJET-III-01, and SIBYLL 2.3e. The simulations cover energies of 1--63 PeV and zenith angles of $10^\circ$--$30^\circ$. The reconstructed $X_{\text{max}}^{\mu}$ shows typical biases within approximately $10\ \mathrm{g/cm^2}$ and resolutions better than $20\ \mathrm{g/cm^2}$ above 10 PeV. Geant4 detector-response simulations show proton--iron discrimination powers increasing from approximately 0.4 to 1.7 with energy. Potential energy-dependent biases associated with the 608 ns MD dead time and the earliest-hit selection are also discussed. These results demonstrate the potential of $X_{\text{max}}^{\mu}$ for cosmic-ray mass-composition studies with LHAASO-KM2A.

This report presents LHAASO progress on the iron-nucleus energy spectrum above 100 TeV using WFCTA-KM2A hybrid events. Events are selected to ensure full trigger efficiency and suppress external contamination. Full efficiency is reached above 100 TeV, with an effective aperture of about 4600 m²·sr, angular resolution better than 0.5°, and core resolution better than 14 m. Energy is reconstructed by combining electromagnetic and muonic components, giving an iron energy bias below 2% and resolution below 15%. Iron identification combines the telescope-reconstructed shower-maximum variable and the KM2A muon-to-electromagnetic ratio. To improve identification, we plan to constrain heavy-nucleus abundances using LHAASO proton and helium measurements and to introduce the Wasserstein distance, which encodes the spatial distribution of secondary particles.

Accurate air-shower core reconstruction is an important basis for determining the geometry of extensive air showers, improving the reconstruction accuracy of related physical quantities, and reducing systematic uncertainties in cosmic-ray composition and energy-spectrum measurements. LHAASO-KM2A and WFCTA observe extensive air showers from different aspects: KM2A records the spatial distribution and arrival-time information of secondary particles at the ground, while WFCTA provides complementary information on shower development and geometry by measuring Cherenkov-light images. The combined use of multi-detector observations is expected to make fuller use of the multiscale responses of air showers at the ground and in the atmosphere, thereby improving the accuracy of shower-core reconstruction.

In recent years, deep-learning methods have demonstrated considerable potential for applications in high-energy physics and cosmic-ray experiments. Compared with conventional methods, neural networks can learn complex nonlinear mapping relationships from detector observations, providing a new approach for processing multi-detector, nonlinear, and multidimensional information.

Using iron simulation events generated with the CORSIKA software and the EPOS-FLUKA hadronic interaction model, we developed a ParticleNet-based graph neural network for core reconstruction in the zenith-angle range of 0°–20° and the energy range of 100 TeV–1 PeV. First, a KM2A-only model was developed using KM2A data, and its performance was superior to that of the conventional reconstruction method over the full energy range. On this basis, WFCTA information was further incorporated to construct a joint KM2A–WFCTA model. The results show that the performance of the joint model was further improved, with the core resolution improving by approximately 6%–24% over the full energy range compared with the conventional method.

This study demonstrates that multi-detector information fusion based on graph neural networks can effectively improve the core reconstruction performance, providing a technical basis for improving the accuracy of LHAASO cosmic-ray composition and energy-spectrum measurements, as well as for developing joint multi-detector geometry reconstruction methods.

Recent ultra-high-energy gamma-ray observations support powerful microquasars as promising Galactic PeVatron candidates capable of explaining the cosmic-ray flux around the knee while accounting for the Galactic diffuse gamma-ray emission. In this work, we further investigate this scenario by considering a two-component model combining a conventional supernova-remnant contribution with a stochastic population of continuously injecting microquasars. Using cosmic-ray measurements, we constrain the model parameters through simulations performed for several Galactic diffusion-halo heights. The resulting models are then used to investigate the contribution of microquasars to the diffuse gamma-ray emission and the detectability of individual sources, and assess their consistency with both the detected source population and the diffuse gamma-ray background measured by LHAASO.

Recent improvements of direct cosmic ray measurements by AMS-02, DAMPE and CALET to-
geather with precise measurements of cosmic ray proton and He, total and logA spectra at knee by
LHAASO open the possibility to study multi-component contributions to cosmic ray flux.
In this work we fit local cosmic ray flux measurements, assuming identical rigidity-dependent flux
of each component with Peters cycle approach. We identify contributions of 4 populations local
cosmic ray flux below knee. We show that first three populations describe all primary fluxes of
AMS-02 nuclei, while 2nd, 3rd and 4th populations contribute to measurements at higher energies
up to Auger for Fe group.
Since every population has it’s own evolution of sources in Galaxy, we study possible variation
of their contribution to measured diffused gamma-ray and neutrino fluxes. We add contribution
of electrons following local measurements and show that total gamma-ray flux can be fitted by
combination of contribution of electrons and cosmic rays at lower energies E < 1 TeV, while above
this energy main contribution to diffuse gamma-ray flux is hadronic. This is consistent with IceCube
measurements of diffuse flux in Galaxy.

The north–south displacement of the cosmic-ray Sun shadow has been shown to precede variations in near-Earth IMF $B_{y}$ by approximately 3.3 days. Whether this leading signal improves predictions beyond existing near-Earth observations, however, remains to be established.
In this work, we use multiple data sources from KM2A Sun shadow and OMNI data between 2020 and 2024, and apply Ridge regression to compare with and without Sun shadow information. Models incorporate magnetic-field history, 27-day recurrence, and additional solar-wind parameters. Training used the data from 2020 to 2022, with separate evaluations in 2023 and 2024. Uncertainty is estimated using a calendar-block bootstrap. For non-ICME samples in 2024, adding Sun shadow information to the baseline containing magnetic-field history and 27-day recurrence reduces the RMSE by 10.2% and increases the Pearson correlation coefficient from 0.235 to 0.425. Positive gains persist in 2024 with an enhanced near-Earth observational baseline and in a retrospective analysis incorporating photospheric and PFSS magnetic-field features.
These results provide empirical support for combining ground-based Sun shadow measurements with other observations to predict near-Earth magnetic-field variations, although the physical origin of the incremental information and its applicability to real-time forecasting require further investigation.

Identifying the hadronic accelerators that power the Galactic cosmic-ray sea remains a central goal of multi-messenger astronomy. LHAASO has observed tens of ultra-high-energy gamma-ray sources, making them compelling PeVatron candidates. ANTARES uses the Earth as an atmospheric-muon filter, giving it a low-background view of the declination band overlapping the LHAASO sky. We present a sub-threshold coincidence search between LHAASO sub-threshold gamma-ray transients and ANTARES neutrino events, adopting the methodology previously established for HAWC–IceCube and HAWC–ANTARES within AMON. This poster presents the current progress of the work.

LHAASO is located in Haizi Mountain, Daocheng County, Sichuan Province, which is an area with a high incidence of thunderstorms. Data analysis shows that the thunderstorm process will affect the overall operating state of the array. This study uses the trigger data of KM2A to find short-term Hit abnormal events, and combines WCDA data analysis to find TGF-like events. This method can be applied to data analysis in WCDA single-channel counting mode, so as to quickly and effectively search and process TGF-like events.

We present a search for gamma-ray emission from the Sun using data collected between 2021 and 2025 with the Water Cherenkov Detector Array (WCDA) of the Large High Altitude Air-shower Observatory (LHAASO). We apply an equal-zenith-angle background method and perform a spatial and spectral likelihood analysis using the WCDA detector response and point-spread function. For the cumulative bin0--6 sample, the best-fit point source is located at $(\Delta\mathrm{RA},\Delta\mathrm{Dec})=(0.10\pm0.17,\,-0.05\pm0.23)^\circ$, consistent with the solar position. The fitted spectrum has a power-law index of $\Gamma=3.22\pm0.15$ and a differential flux normalization of $\phi_0=5.03^{+2.26}_{-1.55}\times10^{-16}\,\mathrm{TeV^{-1}\,cm^{-2}\,s^{-1}}$. The corresponding local test statistic is $\mathrm{TS}=42.6$, equivalent to a local significance of approximately $6.5\sigma$. The likelihood-based significance distributions show a residual positive bias, which is being further investigated. These preliminary results indicate an excess spatially consistent with the solar position.

Terrestrial gamma-ray flashes (TGFs) are high-energy particle bursts originating from the Earth's atmosphere, typically accompanied by thunderstorm and lightning activity. The relativistic runaway electron avalanche (RREA) mechanism is widely considered responsible for the production of TGFs. In this work, Monte Carlo simulations are conducted with the CORSIKA package to investigate the RREA process initiated by seed electrons of varying energies at different altitudes. The results show that the intensity of secondary particles in the RREA process decreases rapidly with increasing altitude and exhibits only a weak dependence on seed electron energy. At altitudes above 10 km, the energy distributions of RREA particles become increasingly dependent on the seed electron energy, with higher seed energies leading to a larger proportion of high-energy secondary particles. After leaving the RREA region, the survival ratios of secondary particles decrease rapidly with decreasing altitude. At altitudes below 10 km, they show a weak dependence on seed electron energy. The relationship between the source altitude of the RREA process and the secondary particle intensity at the LHAASO site is also simulated. The results show that the farther from the RREA source region, the lower the survival ratio of ground-level particles, decreasing from ~80% at an attenuation distance of 20 m to ~5% at 1000 m.

The initiation mechanism of lightning flash remains poorly understood in
modern atmospheric physics, despite decades of observational and theoretical efforts. Gurevich et al. proposed that abundant low-energy electrons produced during
relativistic runaway electron avalanche process (RREA) can utilize hydrometeors as "amplifiers" to form a high-conductivity region, thereby reaching the conditions for
lightning initiation. This highlights the necessity of investigating the relationship
between lightning flash and hydrometeors. In this work, the correlation between
lightning activity and relative humidity (RH) during January 2022–August 2026 is
statistically analyzed using atmospheric electric field and meteorological data from
the LHAASO site (~4410 m a.s.l., Daocheng, Sichuan, China). The results show that
approximately 96% of lightning events are accompanied by an increase in relative
humidity. Meanwhile, lightning activity is frequent when RH ranges between 60%
and 90%, while it is markedly suppressed above 90%, accompanied by a sharp
decrease in flash counts. Lightning event are sparse when RH is below 60%, and no
lightning occurs when RH is below 35%. These results suggest that hydrometeors
may play a key role in lightning initiation, and this study provides observational
information for understanding the lightning initiation mechanism and its correlation
with humidity at high altitudes.

The Sun is an important source of high-energy gamma rays produced by interactions between Galactic cosmic rays and the solar atmosphere. However, discrepancies between theoretical predictions and observations suggest that the role of solar magnetic fields in gamma-ray production is not yet fully understood. In this work, we investigate the effects of localized solar magnetic structures on cosmic-ray proton transport and gamma-ray emission through numerical simulations. We construct a solar magnetic field model incorporating magnetic flux ropes and magnetic arcades, and implement it into G4SOLAR, a simulation framework based on Geant4. The simulations account for cosmic-ray proton propagation, hadronic interactions with the solar atmosphere, and the subsequent production of secondary gamma rays. We further compare the simulated gamma-ray spectra with observations from Fermi-LAT and preliminary results from LHAASO-WCDA. The observational results indicate that solar gamma-ray emission extends into the TeV energy range, while the simulated spectra suggest that localized magnetic structures can significantly enhance gamma-ray production, particularly at high energies. These findings highlight the importance of small-scale solar magnetic fields in shaping the gamma-ray spectrum and provide new insights into the physical mechanisms responsible for high-energy solar gamma-ray emission.

The LHAASO-WCDA array adopts 3-inch photomultiplier tubes (PMTs) for the small-PMT channels of its WCDA-2 and WCDA-3 sub-arrays. A total of 2,220 3-inch PMTs were fully installed in 2021 and have been in continuous operation for over five years. Notably, HZC Photonics, the original manufacturer of the deployed 3-inch PMTs, has terminated the production of this specific model. As a result, subsequent equipment replacement and maintenance necessitate the adaptation of new PMT models to the original high-voltage system. This poster systematically summarizes the in-service operational status of the 3-inch PMT system, analyzes typical faults and failure causes of defective PMTs accumulated during long-term operation, and proposes a targeted repair and maintenance scheme.Title: Operational Status and Maintenance Scheme for 3-inch PMTs of LHAASO-WCDA Array.

Accurate knowledge of atmospheric aerosol attenuation is essential for reconstructing the energy of air showers observed by the Wide Field-of-view Cherenkov Telescope Array (WFCTA) at LHAASO. We investigate whether the array’s existing laser calibration system can also be used to constrain the vertical distribution of aerosol optical depth. In this approach, WFCTA telescopes observe light scattered from laser beams fired at the site. The measured photoelectron yield as a function of scattering angle is compared with an end-to-end simulation and a molecular-scattering reference. Because scattering angle maps to laser-beam height through the observation geometry, departures from the reference can provide information about height-dependent aerosol extinction.
A reliable retrieval requires atmospheric effects to be separated from telescope response and analysis effects. We therefore examine the consistency of experimental and simulated angular profiles across laser configurations, observing periods, and detector-response corrections before interpreting any residual as an aerosol signal. This study establishes the calibration checks and forward-modeling framework needed for a vertical aerosol optical depth measurement with WFCTA. Such measurements could ultimately improve atmospheric corrections and reduce systematic uncertainty in cosmic-ray energy reconstruction.

LHAASO (4410 m a.s.l., Daocheng, Sichuan, China) is a new-generation hybrid ground-based detector array composed of three sub-arrays: KM2A, WCDA, and WFCTA, among which KM2A is used to measure electromagnetic particles and muons in cosmic ray air shower events. In the shower mode of the KM2A array, a shower event is recorded when the trigger condition is satisfied, i.e., at least 20 EDs or MDs are fired within a 400 ns time window. During thunderstorms, the noise trigger recorded by the detector will increase, primarily attributed to intense electromagnetic radiation and precipitation, which consequently elevates the shower event rate in LHAASO-KM2A. In this work, using the CORSIKA and G4KM2A packages, the relationship between the noise-level and shower rate variation in LHAASO-KM2A is simulated. Meanwhile, the noise is subtracted from each shower event by means of re-triggering.

Measurement of cosmic-ray component spectra with KM2A can be explored through template fitting as a practical route to studying the mass evolution of Galactic cosmic rays around the knee. In this work, the relative contributions of different mass groups are inferred by fitting the distribution of the muon-to-electromagnetic shower ratio in reconstructed-energy bins with a Markov Chain Monte Carlo method. Previous studies indicate that, in Monte Carlo (MC) tests, this approach can recover the input composition to a reasonable level and shows only weak sensitivity to the assumed composition model used to generate the templates. Building on that basis, the present study examines several methodological extensions under limited MC data statistics. In particular, the fit is restricted to the peak region of the distribution, and template-shape optimization is explored to reduce the influence of statistical fluctuations in the MC data. Smoothed and parameterized templates are further investigated as practical options for suppressing fluctuations in MC data and improving fit stability. Tests on MC data suggest that the updated procedure retains acceptable closure and does not show strong sensitivity to the composition model adopted in template construction. When applied to real KM2A data, the all-particle behavior remains relatively stable under different template treatments, while composition-sensitive observables still exhibit noticeable dependence on the details of the template description and fit configuration. At the present stage, the reconstructed results tend to favor a lighter composition, with enhanced proton and light-component fractions and reduced heavy components, whereas the total flux remains broadly compatible with reference expectations. These results support the feasibility of template-based composition reconstruction with KM2A and motivate further refinement of template modeling and fitting strategy toward a more robust composition measurement around the knee.

We study the high-Galactic-latitude ultra-high-energy gamma-ray source J0956+4622 with LHAASO WCDA and KM2A. At a Galactic latitude of 50.8°, it is currently the only LHAASO source above 100 TeV with latitude greater than 20°. The source is extended, shows no clear variability, and has a spectral peak at 72.2 TeV, the third highest among LHAASO sources. No firm pulsar or 4FGL counterpart is found, while the emission partly overlaps neutral hydrogen; both hadronic and leptonic models can describe the spectrum. In addition, using the Crab Nebula as a reference, we present a preliminary study of the atmospheric systematic uncertainty of KM2A.

Terrestrial gamma-ray flashes (TGFs) are brief bursts of high-energy gamma-ray emission associated with thunderstorms. In this study, electron and bremsstrahlung photon energy spectra are modeled within the framework of relativistic runaway electron avalanche (RREA) theory. Particle transport and detector response are simulated using G4KM2A, a Geant4-based simulation package for LHAASO-KM2A. Simulations with monoenergetic particles and continuous energy spectra are analyzed to investigate the effects of particle energy, propagation distance, and incidence angle on the response of the electromagnetic particle detectors (EDs). This work provides predictions of the detector response under the simulated conditions and a basis for assessing the feasibility of detecting TGFs with the LHAASO ED array.

Quasi-periodic oscillations (QPOs) in blazar gamma-ray emission offer valuable clues to jet dynamics and central-engine activity. With its wide field of view and long-term monitoring capability, LHAASO-WCDA provides an opportunity to search for such variability at TeV energies. We investigate the long-term WCDA light curves of Mrk 421 and Mrk 501 and compare them with Fermi-LAT observations over the corresponding periods. Wavelet-based time-frequency analysis is used to examine the persistence and evolution of candidate periodic features, with comparisons across different time binning schemes. Particular attention is given to the effects of red noise, the treatment of low-significance time bins, and multiple trials on the interpretation of candidate signals. We also use the Crab Nebula as a control source to investigate annual modulation and potential instrumental systematics. This poster presents the search procedure, preliminary results, and GeV–TeV comparisons, and discusses the robustness of candidate features and the next steps for their validation.

Energy reconstruction is a key component of gamma-ray spectral measurements with LHAASO-WCDA. While conventional methods use the number of triggered detector units, Nhit, as a proxy for shower size and primary energy, the spatial, timing, and charge information of individual hits can provide additional constraints. We develop a ParticleNet-based approach to event-level energy regression, using a graph neural network to learn correlations among detector hits and incorporating event geometry into the reconstruction. Reconstruction bias and energy resolution are evaluated with simulated events across different energy, Nhit, and zenith-angle ranges. To explore its application to observations, we construct a two-dimensional analysis in Nhit and predicted energy, together with the corresponding detector response, and apply a forward-folding approach to the Crab Nebula spectrum. This poster presents the model design, performance evaluation, and preliminary Crab analysis. We discuss the effects of background estimation, the point-spread function, and simulation–data differences, as well as comparisons within a common analysis framework to assess the additional information provided by the predicted energy beyond Nhit.

LHAASO-AI explores deep-learning-based approaches for event reconstruction and classification in LHAASO. We have developed models for four major tasks: gamma/hadron discrimination, arrival-direction reconstruction, shower-core reconstruction, and energy reconstruction. The models are trained and systematically evaluated using large-scale Monte Carlo simulations. Validation with experimental data has been established for gamma/hadron discrimination and directional reconstruction, while corresponding studies for shower-core and energy reconstruction are still in progress. For KM2A, the inference procedure has been optimized for computational efficiency, and an AI-based reconstruction pipeline has been implemented on the IHEP computing cluster. These studies demonstrate the potential of AI-based methods to improve the reconstruction performance and analysis capability of LHAASO.

This report presents recent progress in the application of machine learning techniques to data analysis with the Kilometer Square Array (KM2A) of the Large High Altitude Air Shower Observatory (LHAASO), focusing on two key tasks: gamma–proton discrimination and air-shower direction reconstruction. We have developed deep learning models for these tasks and conducted extensive validation using real observational data, including the Crab Nebula as a standard candle and several representative gamma-ray sources from the first LHAASO source catalog. These studies aim to evaluate the effectiveness and potential of machine learning approaches in practical physics analyses.

Furthermore, we have investigated semi-supervised learning strategies to better exploit the large amount of unlabeled observational data. Our results indicate that pretraining on large-scale unlabeled datasets can accelerate convergence during subsequent training on downstream tasks, offering a promising approach to improving the utilization of experimental data. In parallel, we are conducting studies on model interpretability to understand the underlying physical information and mechanisms learned by deep learning models for event discrimination and direction reconstruction. These efforts aim to establish a clearer connection between model predictions and the physical characteristics of extensive air showers.

This report will summarize our recent findings and discuss the future prospects of machine learning in high-energy gamma-ray astronomy and data analysis.

Precisely identifying the astrophysical sources of cosmic rays remains challenging. Further improvements in the sensitivity to gamma-ray sources are therefore required. We present a Transformer-based deep learning model that uses two separate branches to extract features from heterogeneous data recorded by the electromagnetic particle detectors (EDs) and muon detectors (MDs) of LHAASO-KM2A, and then performs physics-informed feature fusion for gamma/hadron separation and direction reconstruction. Using six months of observations of the Crab Nebula, this method improves the gamma-ray signal significance of the Crab Nebula by more than 50% in the 10–25 TeV band and by more than 35% in the 25–100 TeV band relative to traditional methods, while also improving the angular resolution for gamma-ray sources.

GammaBull is an LLM-driven agent platform that gives astroparticle physicists conversational, end-to-end access to the routine work of a large ground-based gamma-ray observatory. Rather than a single chatbot, it couples a reasoning orchestration core with a growing registry of domain skills, letting it chain multi-step tasks across the LHAASO data system.

I will report the progress regarding the Development of the LOST Trigger Algorithm and Energy Reco for LHAASO-WCDA.

1、Overview of Data Processing Platform；
2、Status of Computing Platform：Job & Resource Status，Storage
Network，Data transform system，Software publish；
3、Status of Domestic Heterogeneous Computing Platforms
4、Summary & Next Plan

INK (Interactive aNalysis worKbench) is a web-based platform that opens the compute and storage resources of batch computing clusters to physicists — enabling interactive data analysis on demand, anytime and anywhere, with just a browser and no local environment setup. In this talk we present the recent progress of INK relevant to LHAASO. We introduce the container-native one-click deployment, which allows a small site or group to set up a production-ready analysis environment on a few machines with a single command. We describe how INK is customized for individual experiments — for example, dedicated GPU resources and applications that are visible only to LHAASO members. We present JobLens, our eBPF-based job-level observability service that gives users real-time, per-job views of CPU, memory, I/O, network and GPU usage. Finally, we show how AI agents (such as OpenCode/OpenChamber) are integrated as first-class interactive applications, backed by the IHEP AI platform, so that researchers can use AI assistance out of the box.

LHAASO generates massive volumes of scientific data, posing significant challenges for efficient data access, management, and distributed analysis. To address these challenges, we present JWanFS, a wide-area distributed object storage platform with a total capacity of 8.38 PB, spanning three geographically separated sites in Beijing, Huairou, and Daocheng. JWanFS provides a unified namespace for transparent cross-site data access, with latency-aware gateway selection to optimize data access paths. It supports multiple access methods, including web interfaces, command-line tools, cross-platform clients, POSIX-compatible file system mounts, and standard S3 APIs, offering a consistent view of scientific data across heterogeneous environments. Through S3-compatible SDKs for languages such as Python, Go, and Java, JWanFS enables seamless integration with existing scientific analysis workflows and supports parallel data access from distributed computing nodes. With scalable storage capacity, reliable data management, and flexible cross-site access, JWanFS aims to simplify scientific data handling and facilitate efficient, collaborative, and large-scale data processing within the LHAASO collaboration.

Scientific collaboration heavily relies on email systems, personal endpoints, computing hosts and self-built websites. The detection and response of security risks require joint participation of security teams and resource consumers. This report proposes an intelligent security service system oriented to research users. It encapsulates back-end threat detection and automated orchestration capabilities into user-facing services including proactive risk notification, and self-service processing of standardized security workflows.
The system adopts a technical architecture featuring a main agent for overall coordination, specialized agents for collaboration, and predefined workflows for execution. By integrating data and capabilities such as asset inventories, endpoint protection and vulnerability detection, it supports phishing email analysis, vulnerability and weak-password scanning for hosts and websites, guidance for device antivirus scanning, as well as system security baseline audits.
Access control combines user roles, asset ownership and operational risks to uniformly restrict data and operation scopes across service interfaces, agent tasks and tool executions. Supported by detection evidence for risk interpretation, the system integrates user verification and remediation, forming a two-way service model of intelligent back-end discovery and collaborative user response. It aims to expand the coverage of security awareness, reduce redundant maintenance workload, and promote the implementation of security accountability to end users.

Earlier this year, the LHAASO Collaboration published measurements of the cosmic-ray proton and helium spectra from 100 TeV to 10 PeV, revealing new spectral features that suggest potentially different origins of cosmic rays in different energy ranges. To further characterize these features and clarify their physical implications, it is important to extend the proton and helium spectrum measurements to lower energies and investigate the spectra of heavier nuclei. This talk will present recent progress in these studies. In addition, the absolute energy calibration of the detector affects both the energies at which fine spectral features appear and the measured cosmic-ray fluxes. Results of absolute energy calibration using the cosmic-ray Moon shadow will also be presented

IN cosmic ray EAS experiment, it is neccessary to combine hadronic component, electromagnetic compoment and muon component to determine energy and then obtain all particle energy spectrum. ENDA-64 keeps on running and taking data at the LHAASO site. Since Jan. 2025, EAS thermal neutron sampling time has been set 5 ms for 21 months to reduce background. Detected thermal neutrons of all data are corrected according to calibration results by using neutron beam test. Moreover, detected thermal neutrons of all data in both dry season and rain season are corrected with soil moisture measurement. Different hadronic interaction models are compared in simulation. Beyond these progresses, difference between analysis results of real data and those of simulation data becomes much smaller. The upgraded all particle energy spectrum of cosmic ray around the knee region determined with electrons, muons and thermal neutrons by using coincident events between ENDA and KM2A is obtained, and systematic uncertainty is considered.

The cosmic-ray all-particle energy spectrum exhibits a distinct softening around $100~\rm PeV$, commonly known as the “second knee". This spectral feature is widely interpreted as the cutoff of the heaviest Galactic components and the onset of the transition from Galactic to extragalactic origins. In light of existing discrepancies among current experiments regarding the second knee, the Large High Altitude Air Shower Observatory (LHAASO) is uniquely equipped to provide a definitive measurement. Utilizing coincident detections of muons and electromagnetic particles with KM2A, we construct a robust energy estimator $N_{\rm e\mu}^{\rm all}$, which demonstrates minimal dependence on primary composition and hadronic interaction models. This novel reconstruction strategy substantially expands the effective detection area, boosting event statistics while mitigating detector saturation in electromagnetic measurements. Armed with more than five years of KM2A data, our preliminary results uncover a noticeable dip feature near $15~\rm PeV$ and firmly establish the second knee at $75~\rm PeV$. Concurrently, the inferred mean logarithmic mass keeps increasing up to $100~\rm PeV$; beyond which larger accumulated simulation statistics are required to draw solid conclusions.

We present a measurement of the all-particle cosmic-ray energy spectrum from about 30 TeV to 1 PeV using about 4.3 years of LHAASO-KM2A data. The shower size is described by the combined electromagnetic and muonic estimator $N_{e\mu} = N_e + 2.8\,N_\mu$, and events are selected with cores between 320 and 420 m from the array centre and zenith angles below 30°.

The reconstructed energy distribution is converted into the primary energy spectrum with an iterative Bayesian unfolding. The response matrices and efficiencies are taken from Monte Carlo simulations with four composition models (Gaisser, Hörandel, GSF, GST) and two hadronic interaction models (EPOS and QGSJET), giving eight independent unfoldings.

To test the stability of the result, the data are divided into four zenith-angle bins of equal aperture, and each bin is unfolded with its own response matrix and acceptance. The attenuation of the shower size with zenith angle is studied with the constant intensity cut method, both in data and Monte Carlo.

We will outline the full uncertainty budget under evaluation, covering data and Monte Carlo statistics as well as systematics from the unfolding procedure, composition and hadronic interaction models, selection cuts, ED and MD calibration, atmospheric pressure and temperature corrections.

LHAASO is the high-altitude cosmic-ray observatory located in Daocheng, Sichuan Province, China. LHAASO-KM2A owns a huge muon detector array (MD), which has unique advantages in the precise measurement of muons in extensive air showers (EASs). Muons are mainly generated from decays of pions and kaons in hadronic cascades. The lateral distribution of muons is sensitive to hadronic interaction processes in EASs, and can provide important information for the study of hadronic interaction models, cosmic ray energy determination, and component separation.
We analyzed both real data and simulation data of the MD array. The upgraded Greisen formula, which is more closely related to the hadronic cascade, was used to fit the muon lateral distribution, and the muon size was obtained as a fitting parameter. The consistency between the fitting results and measurements by the detectors was checked from several aspects. The fitting results were compared with those obtained by using the NKG function. We also compared the fitting results between simulation and real data, and compared the simulation results obtained with different hadronic interaction models.

Direct measurements of atmospheric muon spectrum at high energies (> 10 TeV) can help to understand the contribution of prompt muon fluxes and clarify the details of the primary energy spectrum. The dominant processes for this energy range are pair production and bremsstrahlung. It is assumed to reconstruct muon energy with a pair-meter method, using WCDA data. Due to cellular structure of WCDA it can be considered as a track detector for near horizontal directions. The report describes the simulation process of events from near-horizontal high-energy muons and the reconstruction procedure of their direction and energy. The separation quality of single muon events from the background is given. Preliminary experimental result on angle distributions is also presented.

We report the progress on the combined measurement of large-scale anisotropy by LHAASO-WCDA and LHAASO-KM2A. For wcda， we remove solar activities and improve the significance of measurement at low energy. For km2a, we add one more years' data. We find the energy dependence of tail-in, cygnus regions. And the region A can be further split into two regions

The weak anisotropies in the arrival directions of cosmic rays offer valuable insights into their origin and propagation. Compared with energy-dependent evolution, rigidity-dependent variations provide a more direct and effective probe of cosmic-ray transport, yet such measurements have remained elusive. Here, for the first time, we reconstruct rigidity using LHAASO-KM2A data by combining electromagnetic secondaries with muons. Additionally, cosmic-ray moon shadows are used to correct the energies of the samples. We thereby observe rigidity-dependent anisotropies spanning from 10 TV to 500 TV, revealing that different nucleon samples exhibit similar evolutionary behavior. Our findings have critical implications for understanding cosmic-ray propagation and origin.

Many $\gamma$-ray sources, such as supernova remnants, superbubbles, and pulsar halos, may be surrounded by regions where cosmic ray (CR) diffusion is suppressed relative to the typical galactic rate. Although these regions strongly affect CRs injected by their associated accelerators, their impact on the pre-existing CR background remains poorly understood. We have derived an analytical solution for the response of an anisotropically diffusing CR background to a spherical region with isotropically suppressed diffusion. We find that such a region can amplify the CR density gradient within it, potentially affecting $\gamma$-ray background estimates that assume a uniform CR density. A nearby slow-diffusion region (SDR) magnetically connected to Earth can also markedly reduce the observed CR dipole amplitude. If the ratio of diffusion coefficients inside and outside the region varies with CR energy, certain parameter combinations may account for the observed amplitude minimum near 150 TeV and the accompanying reversal of the right-ascension phase.