arXiv subjects

Chao Chen

Publications and source records attributed to Chao Chen.

At least 37 records · Page 2Linked to original sources

arXiv2026

Prospects for geoneutrino detection with JUNO

Geoneutrinos, which are antineutrinos emitted during the decay of long-lived radioactive elements inside Earth, serve as a unique tool for studying the composition and heat budget of our planet. The Jiangmen Underground Neutrino Observatory (JUNO) experiment in China, which has recently completed construction, is expected to collect a sample comparable in size to the entire existing world geoneutrino dataset in less than a year. This paper presents an updated estimation of sensitivity to geoneutrinos of JUNO using the best knowledge available to date about the experimental site, the surrounding nuclear reactors, the detector response uncertainties, and the constraints expected from the TAO satellite detector. To facilitate comparison with present and future geological models, our results cover a wide range of predicted signal strengths. Despite the significant background from reactor antineutrinos, the experiment will measure the total geoneutrino flux with a precision comparable to that of existing experiments within its first few years, ultimately achieving a world-leading precision of about 8% over ten years. The large statistics of JUNO will also allow separation of the Uranium-238 and Thorium-232 contributions with unprecedented precision, providing crucial constraints on models of formation and composition of Earth. Observation of the mantle signal above the lithospheric flux will be possible but challenging. For models with the highest predicted mantle concentrations of heat-producing elements, a 3-sigma detection over six years requires knowledge of the lithospheric flux to within 15%. Together with complementary measurements from other locations, the geoneutrino results of JUNO will offer cutting-edge, high-precision insights into the interior of Earth, of fundamental importance to both the geoscience and neutrino physics communities.

hep-ex↗

arXiv2026

Observation of $χ_{cJ}\to ΛK^0_S\bar Ξ^0 + c.c.$ and improved measurements of $χ_{cJ}\to ΛK^-\bar Ξ^+ + c.c.$

By analyzing $(2712.4\pm14.3)\times10^6$ $ψ(3686)$ events collected with the BESIII detector operating at the BEPCII collider, we report the first observation of $χ_{cJ}\to ΛK^0_S\bar Ξ^0 + c.c.$ ($J=0,1,2$) with significances greater than $10σ$, including systematic uncertainties, and improved measurements of $χ_{cJ}\to ΛK^-\bar Ξ^+ + c.c.$ The branching fractions of these decays are determined to be $\mathcal{B}(χ_{c0}\to ΛK^0_S\bar Ξ^0+c.c.)=(1.13\pm0.13\pm0.13)\times10^{-4}$, $\mathcal{B}(χ_{c1}\to ΛK^0_S\bar Ξ^0+c.c.)=(0.74\pm0.08\pm0.07)\times10^{-4}$, $\mathcal{B}(χ_{c2}\to ΛK^0_S\bar Ξ^0+c.c.)=(1.16\pm0.11\pm0.14)\times10^{-4}$, $\mathcal{B}(χ_{c0}\to ΛK^-\bar Ξ^++c.c.)=(1.90\pm0.08\pm0.16)\times10^{-4}$, $\mathcal{B}(χ_{c1}\to ΛK^-\bar Ξ^++c.c.)=(1.40\pm0.05\pm0.11)\times10^{-4}$, and $\mathcal{B}(χ_{c2}\to ΛK^-\bar Ξ^++c.c.)=(1.95\pm0.07\pm0.15)\times10^{-4}$. The first uncertainties are statistical, and the second are systematic.

hep-ex↗

arXiv2026

Observation of the electromagnetic Dalitz transition $J/ψ\to e^+ e^- η_c$

Using $(10.087\pm0.044)\times10^9$ $J/ψ$ events collected with the BESIII detector at the $e^+e^-$ BEPCII collider, we present the first observation of the electromagnetic Dalitz decay $J/ψ\to e^+ e^- η_c$. The relative branching fraction $R \equiv \frac{Γ(J/ψ\to e^+e^-η_c)}{Γ(J/ψ\to γη_c)}$ is determined to be $(0.65\pm0.02_{\rm stat.}\pm0.07_{\rm sys.})\%$, where the first uncertainty is statistical and the second systematic. The $q^2$-dependent form factors are also extracted, and no significant deviation from the theoretical prediction is seen.

hep-ex↗

arXiv2026

Does On-Policy Distillation for Safety Pose Backdoor Risks?

On-policy distillation (OPD) has attracted growing attention as an effective way to transfer capabilities from teacher models to student models. Recent studies further explore OPD as a tool for improving large language model safety with promising results. However, these approaches typically assume that the teacher and training data are trustworthy. In this paper, we uncover an overlooked threat to OPD for safety: a safety-aligned but backdoored teacher can propagate its hidden malicious behavior to an initially clean student. Under our threat model, a poisoning rate as low as 3% results in an attack success rate (ASR) of up to 70% on the distilled student. We further identify two training choices that can amplify this risk. First, increasing the number of training epochs can lead to high ASR even at low poisoning rates. With only 10 poisoned samples, ASR reaches 67% after 16 epochs. Second, the commonly used top-k KL can accelerate backdoor transfer, causing trigger-conditioned harmful behavior to emerge earlier than sampled-token KL in most settings. Alongside these findings, we explore a simple mitigation, Lazy Defense, which clips KL rewards to make student updates less aggressive, limiting aggressive updates and slowing backdoor learning. Experiments show that Lazy Defense delays backdoor transfer in low poisoning rate settings. Together, our findings reveal that OPD can propagate backdoors, highlighting the need to address the safety risks of OPD.

cs.LG↗

arXiv2026

First observation of the electromagnetic Dalitz decay $ψ(3686) \rightarrow μ^+ μ^- η^\prime$

Utilizing $(2712.4 {\pm} 14.3)\times10^{6}~ψ(3686)$ events collected by the BESIII detector at the symmetric $e^+ e^-$ collider BEPCII, we report the first observation of the electromagnetic Dalitz decay $ψ(3686) \to μ^+ μ^-η^{\prime} $ with a statistical significance of 6.1$σ$. The branching fraction is determined to be $\mathcal{B}(ψ(3686) \to μ^+ μ^- η^{\prime})=(4.1 \pm 1.0_{\rm stat.} \pm 0.4_{\rm syst.})\times 10^{-7}$. The ratio to the branching fraction of the radiative decay $ψ(3686) \to γη^{\prime}$ is estimated to be $(3.3\pm0.9)\times10^{-3}$, which is consistent with the prediction of the vector meson dominance model within $1σ$. Furthermore, using the branching fraction of $ψ(3686) \to e^+ e^- η^{\prime}$ previously measured by the BESIII experiment, the ratio between the muon and the electron channels is evaluated to be $0.22\pm0.07$, which is consistent with the calculation of the vector meson dominance model within $1σ$, and no significant violation of lepton flavor universality is found.

hep-ex↗

arXiv2026

Updated measurement of the branching fraction of $D_s^+ \to τ^+ ν_τ$

Using a dataset of 7.33 fb$^{-1}$ of $e^+ e^-$ annihilation data collected with the BESIII detector at center-of-mass energies from 4.128 to 4.226 GeV, we report an updated measurement of the branching fraction of $D_s^+ \to τ^+ ν_τ$ via four $τ^+$ decay modes: $τ^+ \to e^+ ν_e \barν_τ$, $μ^+ ν_μ \barν_τ$, $π^+\barν_τ$, and $π^+ π^{0} \barν_τ$. The branching fraction is determined to be $\mathcal{B}({D_s^+ \to τ^+ ν_τ}) = (5.37 \pm 0.08_{\rm stat} \pm 0.06_{\rm syst})$ %. The product of the modulus of the Cabibbo-Kobayashi-Maskawa matrix element $|V_{cs}|$ and the $D_s^+$ decay constant $f_{D_s^+}$ is measured to be $f_{D_s^+} |V_{cs}| = (248.2 \pm 1.9_{\rm stat} \pm 1.4_{\rm syst} \pm 0.6_{\rm input} \pm 0.8_{\rm EM})$ MeV. Both the branching fraction and the product $f_{D_s^+} |V_{cs}|$ are the most precise results yet obtained. Then, taking $f_{D_s^+}$ from lattice quantum chromodynamics calculations results in $|V_{cs}| = 0.993 \pm 0.008_{\rm stat} \pm 0.006_{\rm syst} \pm 0.003_{\rm input} \pm 0.003_{\rm EM}$. Conversely, one finds $f_{D_s^+} = (255.0 \pm 1.9_{\rm stat} \pm 1.4_{\rm syst} \pm 0.6_{\rm input} \pm 0.8_{\rm EM})$ MeV when taking $|V_{cs}|$ from the CKMfitter group as an input. Combining with the world average value of $D_s^+ \to μ^+ ν_μ$, the ratio of the branching fractions between $D_s^+ \to τ^+ ν_τ$ and $D_s^+ \to μ^+ ν_μ$ is estimated to be $10.04 \pm 0.29$, which is consistent with the Standard Model prediction of lepton flavor universality.

hep-ex↗

arXiv2026

Revealing After Overwriting: An Exponential POMDP OPE Lower Bound under History-Dependent Logging

Multi-step revealing can make off-policy evaluation tractable under memoryless logging. With history-dependent logging, state decodability and target-relevant evidence can separate. For every horizon $H\ge3$, we construct two exactly realizable POMDPs with four actions, at most four states per layer, a known logger, and a memoryless target. Action overlap, history coverage, and observation-only revealing remain bounded independently of $H$, yet the target values differ by $1/2$ and the KL divergence between the logged laws is $Θ(4^{-(H-1)})$, forcing exponential sample complexity. Logger memory makes states distinguishable, while reset erases the model-distinguishing evidence preserved by the target. A separate construction retains this barrier with common, known observation-only revealing operators. Under action and history coverage, we give a finite-class OPE guarantee using common observable value representations that remain valid at every history. The sample bound depends polynomially on their second-moment cost. In the common-operator construction, the same value direction has constant marginal decoding cost but exponential history-conditioned cost. Finally, on a fixed four-action continuum, we derive matching passive and budgeted readout rates. With one known channel and unit read cost, early reads are optimal. With unknown sensor bias, early reads alone remain exponentially costly. Combining them with post-reset calibration gives sample complexity independent of $H$ when both read types receive fixed positive expected budgets per trajectory.

cs.LG↗

arXiv2026

Observation of $D^+ \to K^{0}ρ^+$ and $D^+\to K^{+}ρ^0$ in Doubly Cabibbo-Suppressed Decay $D^+ \to K^+π^+π^-π^0$

By analyzing an $e^+e^-$ collision data sample with an integrated luminosity of 20.3 fb$^{-1}$ collected with the BESIII detector at the center-of-mass energy of 3.773 GeV, we perform the first amplitude analysis on the doubly Cabibbo-suppressed decay $D^+ \to K^+π^+π^-π^0$ and report the first observation of $D^+ \to K^{*0}ρ^+$ and $D^+\to K^{*+}ρ^0$. The corresponding branching fractions are $(5.67\pm0.41_{\rm stat}\pm0.17_{\rm syst})\times10^{-4}$ and $(5.32\pm0.57_{\rm stat}\pm0.24_{\rm syst})\times10^{-4}$, respectively. These two $D\to VV$ decay both have large transverse polarizations. The longitudinal polarization fractions are measured to be $0.111\pm0.024_{\rm stat}\pm0.008_{\rm syst}$ and $0.263\pm0.049_{\rm stat}\pm0.015_{\rm syst}$, respectively. The branching fraction of the decay $D^+\to K^+ω$ is measured to be $(4.76\pm0.84_{\rm stat}\pm0.13_{\rm syst})\times 10^{-5}$.

hep-ex↗

arXiv2026

GATE-ST: Gene-Aware Text-image Encoder for Spatial Transcriptomics

Spatial transcriptomics enables spatially resolved gene expression analysis from slide-level images while preserving morphological features, providing valuable information for studying disease mechanisms and developing treatments. However, spatial gene expression profiling typically requires expensive and time-consuming tests. While existing image-based prediction optimizations mostly revolve around including positional embeddings and further image-based changes, text-based optimizations remain relatively unexplored. We present GATE-ST, which incorporates text-based inputs into image-based spatial gene expression predictions. With this approach, generated text descriptions of genes are utilized to better spatial transcriptomics prediction results. Gene summaries are put through a text encoder, generating embeddings that integrate with image embeddings through cross-attention layers to align with morphological features. We demonstrate the effectiveness of such text inputs by benchmarking performance against random gene embeddings and multiple other image-text fusion architectures, and show that GATE-ST outperforms these alternatives. Our results demonstrate the effectiveness of GATE-ST in pathology imaging, which may greatly reduce the time and cost of accurate spatial transcriptomic predictions, proving the potential of text-guided spatial gene expression prediction.

cs.AI↗

arXiv2026

MATCH: Performance Characterization and Scientific Observations of the Wuhan University 1-m Optical Telescope

The Multi-mode Autonomous Terminal for Compatible Hybrid-optics (MATCH), operated by Wuhan University and located at Lenghu, is a 1-m Ritchey--Chrétien telescope equipped with imaging and spectroscopic instruments. MATCH has been in trial operation since October 2025. In this work, we present the telescope and instrument configuration, characterize its performance during the first year of operation, and describe the integrated observing workflow developed for routine and time-domain observations, including the observatory control system, observation scheduler, and automated data reduction pipelines. Under typical observing conditions, the imaging system reaches 60-s-equivalent $5σ$ limiting magnitudes of approximately 18--20 mag across the $ugri$ bands, while the spectroscopic system reaches approximately 15--16~mag in the B and G channels in a 30-minute integration at the effective spectral resolution of the instrument. In the best-quality imaging observations, the $g$- and $r$-band depths approach 21~mag. Together with flexible scheduling and Target-of-Opportunity capability, MATCH provides photometric and spectroscopic follow-up and long-term monitoring of transient and variable sources.

astro-ph.IM↗

arXiv2026

Improved search for $ψ(3770) \to γη_{c}(1S, 2S)$ radiative transitions

Based on an integrated luminosity of $20.3~\mathrm{fb}^{-1}$ of $e^{+}e^{-}$ annihilation data collected at a center-of-mass energy of $3.773~\rm{GeV}$ with the BESIII detector operating at the BEPCII collider, an improved search for the radiative transitions $ψ(3770) \to γη_{c}(1S, 2S)$ is performed using the hadronic decays $η_{c}(1S, 2S) \to K^{0}_{S} K^{\pm} π^{\mp}$. No significant signal is observed. The corresponding 90$\%$ confidence level upper limits on the product branching fractions are set to be $5.0 \times 10^{-6}$ for the $η_{c}(1S)$ transition and $3.7 \times 10^{-6}$ for the $η_{c}(2S)$ transition. The 90$\%$ confidence level upper limits on the partial decay widths are also reported to be $Γ(ψ(3770) \to γη_{c}(1S)) < 5.5$ keV and $Γ(ψ(3770) \to γη_{c}(2S)) < 29.4~\rm{keV}$. With about seven times larger integrated luminosity than used previously, these results lower the upper limits by approximately a factor of three and two for the $η_{c}(1S)$ and $η_{c}(2S)$ transitions, respectively.

hep-ex↗

arXiv2026

JIVE: Jacobian-Informed Volume Expansion for Diverse Generative Sampling

Generative models often suffer from mode collapse and limited sample diversity. While prior works attempt to mitigate this by jointly generating a batch of samples and repelling their trajectories, these heuristics do not explicitly maximize the diversity of the resulting endpoints. We introduce JIVE, a training-free framework that enhances generative diversity by injecting velocity perturbations aligned with the leading right singular subspace of the generator's endpoint Jacobian. By leveraging this local geometric structure, JIVE provably maximizes endpoint diversity while preserving sample quality. To maintain practical efficiency, we compute these perturbation directions via matrix-free iterations rooted in classical numerical linear algebra, requiring only a small computational overhead. Across different benchmarks, JIVE boosts both pixel and feature-level diversity in few-step and one-step generation.

cs.LG↗

arXiv2026

Precision Studies and Searches for CP Asymmetries in the Inclusive Decay $Λ_{c}^{+}\to ΛX$

Based on $e^{+}e^{-}$ annihilation data collected with the BESIII detector at center-of-mass energies from $4.600$ to $4.699~\mathrm{GeV}$, corresponding to an integrated luminosity of $4.5~\mathrm{fb}^{-1}$, we present the first measurement of the longitudinal polarization of $Λ$ hyperon produced in the inclusive decay $Λ_c^+ \to ΛX$, where $X$ denotes any allowed final states. The polarizations are determined to be $P_Λ=-0.393\pm0.055_{\rm stat}\pm0.020_{\rm syst}$ and $P_{\barΛ}=0.288\pm0.056_{\rm stat}\pm0.017_{\rm syst}$. A search for CP violation is performed using an asymmetry constructed from the $Λ$ polarization and the $Λ\to pπ^{-}$ decay asymmetry parameter, and $A_{\mathrm{CP}}^{\mathrm{pol}}=0.15\pm0.12_{\rm stat}\pm0.03_{\rm syst}$ was obtained. Furthermore, an updated measurement of the absolute branching fraction is reported as $B(Λ_c^+ \to ΛX)=(38.07\pm0.38_{\rm stat}\pm0.49_{\rm syst})\%$, representing a fourfold precision improvement over the previous BESIII measurement. A search for CP violation in the decay rate yields $A_{\mathrm{CP}}^{\mathrm{dir}}=(1.5\pm1.0_{\rm stat}\pm1.0_{\rm syst})\%$. No evidence for CP violation is observed in this inclusive charm baryon decay. The subscripts `stat' and `syst' denote statistical and systematic uncertainties, respectively.

hep-ex↗

arXiv2026

A Multi-level Information Integration Framework for Physically Verifiable Fault Diagnosis of Rotating Machinery

Integrating multi-level information, from physical models through data-driven diagnostics to natural language reasoning, into verifiable decision chains is a growing need in intelligent manufacturing. In bearing fault diagnosis, taken here as a representative testbed, the standard output is a class label and a confidence score derived from the classifier's own distribution, offering limited means of comparison against independent physical knowledge. Meanwhile, language models increasingly used for maintenance communication may introduce unsupported content. This work addresses both limitations from the output side. The proposed Diagnostic Evidence Network (DENet) is an encoder-agnostic multi-task framework that extends the output to a structured evidence record: the classification, a predicted characteristic frequency comparable against the theoretical value determined by bearing geometry and shaft speed, and a temporal localization of transient impulses inspectable on the raw waveform. Across four encoders and three public datasets, this evidence incurs no statistically significant accuracy cost, with a frequency error of about 6 Hz on 1,024-point segments. The deviation between predicted and theoretical frequency constitutes a label-free, inference-time validation signal. It detects misclassifications with AUROC of 0.970 and 0.871, and retains separation within the high-confidence subset. Finally, a QLoRA-adapted language model renders DENet's evidence into traceable maintenance reports without contributing diagnostic decisions, reducing unsupported-claim rates from 10-12% to 2% with no fabricated quantities observed.

cs.LG↗

arXiv2026

Observation of $η(2600)$ and Threshold Enhancements in the $Λ\barΛ$ System

Using $2712.4 \pm 14.3$ million $ψ(3686)$ events collected with the BESIII detector, the $Λ\barΛ$ system produced in $ψ(3686)$ radiative decays is studied. A model-independent partial wave analysis reveals a significant threshold enhancement structure dominated by the $^1S_0$ and $^3P_0$ partial waves, corresponding to $J^{PC} = 0^{-+}$ and $0^{++}$, respectively. In addition, a new pseudoscalar resonance, designated as $η(2600)$, is observed in the $^1S_0$ partial wave with a mass value consistent with the previously reported $X(2600)$ state, which represents the heaviest light meson observed to date. These results enhance our understanding of baryon-antibaryon threshold dynamics and the pseudoscalar light hadron spectroscopy.

hep-ex↗

arXiv2026

Measurements of the Absolute Branching Fraction of the Semileptonic Decay $\mathbf{Ξ^{-}\rightarrow Λe^- \barν_{e}}$ and the Axial Charge of the $\mathbfΞ^{-}$

Using $(10087\pm44)\times10^6$ $J/ψ$ events collected with the BESIII detector, we study the semileptonic decay $Ξ^{-}\rightarrow Λe^- \barν_{e}$ for the first time at an electron-positron collider. The absolute branching fraction is determined for the first time to be $(3.60\pm0.40_{\mathrm{stat}}\pm0.10_{\mathrm{syst}})\times10^{-4}$, which is 3.9 standard deviations below the world average. In addition, using an 11-dimensional angular analysis, the axial-vector to vector coupling $g_{av}$ is determined to be $0.18\pm0.07_{\mathrm{stat}}\pm0.02_{\mathrm{syst}}$. These results are used to test various SU(3)-flavour effective models. Under the SU(3)-flavour symmetry limit, the axial charge is found to be $g_A^H = 0.22\pm0.08_{\mathrm{stat}}\pm0.02_{\mathrm{syst}}$. Despite using only 5\% of the statistics of previous experiments, this analysis achieves a comparable precision for the axial charge.

hep-ex↗

arXiv2026

Search for the reaction channel $e^+ e^- \to ηη\,J/ψ$ and the isospin partner of the $Z_c(3900)$ at center-of-mass energies $\sqrt{s} = 4.226-4.950$ GeV

We search for the reaction channel $e^+ e^- \to ηη\,J/ψ$ in a data sample with center-of-mass energies from 4.226 to 4.950 GeV that was collected by the BESIII detector operating at the Beijing Electron Positron Collider (BEPCII). The data analysis is performed with two different reconstruction methods, exclusive and semi-inclusive, enabling a comparison and combination of the results. Only at a few energy points a non-zero cross section is observed with a statistical significance of more than 3$σ$ using one of the methods. Therefore, the corresponding upper limits of the cross section at the 90% confidence level are determined. The energy dependent results show clear deviations from the the line shape expected from three-body phase space alone. Since the statistical significance for almost all center-of-mass energies is low, the upper limits for the reaction channel $e^+ e^- \to ηη\,J/ψ$ also serve as limits for the existence of a possible isospin partner to the charmonium-like isospin triplet $Z_{\rm c}(3900)$ which decays to $J/ψη$.

hep-ex↗

arXiv2026

Search for the radiative decay $D^+_s \to γK^*(892)^+$

Using 7.33 fb$^{-1}$ of $e^+e^-$ collision data samples collected with the BESIII detector at center-of-mass energies between 4.128 and 4.226 GeV, we perform a simultaneous fit to search for the radiative decay $D_s^+\toγK^*(892)^+$ via $K^*(892)^+\to K^+π^0$ and $K^*(892)^+\to K_S^0π^+$ for the first time. No significant signals are observed. The upper limit on the branching fraction of $D^+_s\toγK^*(892)^+$ is set to be $2.3\times10^{-4}$ at the $90\%$ confidence level.

hep-ex↗