arXiv subjects

Chao Chen

Publications and source records attributed to Chao Chen.

At least 451 records · Page 25Linked to original sources

arXiv2024

Search for $e^{+}e^{-} \to ϕχ_{c0}$ and $ϕη_{c2}(1D)$ at center-of-mass energies from 4.47 to 4.95 GeV

Utilizing a data set of $6.7$ fb$^{-1}$ from electron-positron collisions recorded by the BESIII detector at the BEPCII storage ring, a search is conducted for the processes $e^{+}e^{-} \to ϕχ_{c0}$ and $ϕη_{c2}(1D)$ across center-of-mass energies from 4.47 to 4.95 GeV. In the absence of any significant signals, upper limits are set. These include limits on the Born cross sections for $e^{+}e^{-} \to ϕχ_{c0}$, as well as the product of the Born cross section for $e^{+}e^{-} \to ϕη_{c2}(1D)$ and a sum of five branching fractions. Furthermore, the product of the electronic width of $Y(4660)$ and the branching fraction of the $Y(4660) \to ϕχ_{c0}$, denoted as $Γ^{Y(4660)}_{e^{+}e^{-}} \mathcal{B}_{Y(4660) \to ϕχ_{c0}}$, is determined to be $< 0.40$ eV at the 90\% confidence level.

hep-ex↗

arXiv2024

Observation of $χ_{cJ}\to p \bar p K^0_S K^- π^+ + c.c.$

By analyzing $(27.12\pm0.14)\times10^8$ $ψ(3686)$ events collected with the BESIII detector operating at the BEPCII collider, the decays of $χ_{cJ} \to p \bar{p} K^0_S K^- π^+ +c.c.(J=0, 1, 2)$ are observed for the first time with statistical significances greater than $10σ$. The branching fractions of these decays are determined to be $\mathcal{B}(χ_{c0}\to p \bar p K^{0}_{S} K^- π^+ + c.c.)=(2.61\pm0.27\pm0.32)\times10^{-5},$ $\mathcal{B}(χ_{c1}\to p \bar p K^{0}_{S} K^- π^+ + c.c.)=(4.16\pm0.24\pm0.46)\times10^{-5},$ and $\mathcal{B}(χ_{c2}\to p \bar p K^{0}_{S} K^- π^+ + c.c.)=(5.63\pm0.28\pm0.46)\times10^{-5}$, respectively. The processes $χ_{c1,2} \to \bar{p} Λ(1520) K^0_S π^{+} + c.c.$ are also observed, with statistical significances of 5.7$σ$ and 7.0$σ$, respectively. Evidence for $χ_{c0} \to\bar{p} Λ(1520) K^0_S π^{+} + c.c.$ is found with statistical significances of 3.3$σ$ each. The corresponding branching fractions are determined to be $\mathcal{B}(χ_{c0}\to \bar{p} Λ(1520) K^0_S π^{+} + c.c.) =(1.61^{+0.68}_{-0.64}\pm0.23)\times10^{-5}$, $\mathcal{B}(χ_{c1}\to \bar{p} Λ(1520) K^0_S π^{+} + c.c.)=(4.06^{+0.80}_{-0.76}\pm0.52)\times10^{-5}$, and $\mathcal{B}(χ_{c2}\to \bar{p} Λ(1520) K^0_S π^{+} + c.c.)=(4.09^{+0.87}_{-0.84}\pm0.42)\times10^{-5}$. Here, the first uncertainties are statistical and the second ones are systematic.

hep-ex↗

arXiv2024

Charge Stripe Manipulation of Superconducting Pairing Symmetry Transition

Charge stripes have been widely observed in many different types of unconventional superconductors, holding varying periods ($\mathcal{P}$) and intensities. However, a general understanding on the interplay between charge stripes and superconducting properties is still incomplete. Here, using large-scale unbiased numerical simulations on a general inhomogeneous Hubbard model, we discover that the charge-stripe period $\mathcal{P}$, which is variable in different real material systems, could dictate the pairing symmetries -- $d$ wave for $\mathcal{P} \ge 4$, $s$ and $d$ waves for $\mathcal{P} \le 3$. In the latter, tuning hole doping and charge-stripe amplitude can trigger a $d$-$s$ wave transition and magnetic-correlation shift, where the $d$-wave state converts to a pairing-density wave state, competing with the $s$ wave. These interesting phenomena arise from an unusual stripe-induced selection rule of pairing symmetries around on-stripe region and within inter-stripe region, giving rise to a critical point of $\mathcal{P}=3$ for the phase transition. In general, our findings offer new insights into the differences in the superconducting pairing mechanisms across many $\mathcal{P}$-dependent superconducting systems, highlighting the decisive role of charge stripe.

cond-mat.str-el↗

arXiv2024

Search for the massless dark photon with $D^0\toωγ'$ and $D^0\toγγ'$

Using $7.9~\rm{fb^{-1}}$ of $e^+e^-$ collision data collected at $\sqrt{s}=3.773$ GeV with the BESIII detector at the BEPCII collider, we search for the massless dark photon with the flavor-changing neutral current processes $D^0\toωγ'$ and $D^0\toγγ'$ for the first time. No significant signals are observed, and the upper limits at the 90% confidence level on the massless dark photon branching fraction are set to be $1.1\times10^{-5}$ and $2.0\times10^{-6}$ for $D^0\toωγ'$ and $D^0\toγγ'$, respectively. These results provide the most stringent constraint on the new physics energy scale associated with $cuγ'$ coupling in the world, with the new physics energy scale related parameter $|\mathbb{C}|^2+|\mathbb{C}_5|^2<8.2\times10^{-17}~\rm{GeV}^{-2}$ at the 90% confidence level.

hep-ex↗

arXiv2024

Search for the radiative decays $D^+\toγρ^+$ and $D^+\toγK^{*+}$

We search for the radiative decays $D^{+} \to γρ^+$ and $D^{+} \to γK^{*+}$ using 20.3~fb$^{-1}$ of $e^+e^-$ annihilation data collected at the center-of-mass energy $\sqrt{s}=3.773$ GeV by the BESIII detector operating at the BEPCII collider. No significant signals are observed, and the upper limits on the branching fractions of $D^{+} \to γρ^+$ and $D^{+} \to γK^{*+}$ at 90\% confidence level are set to be $1.3\times10^{-5}$ and $1.8\times10^{-5}$, respectively.

hep-ex↗

arXiv2024

Observation of an axial-vector state in the study of $ψ(3686) \to ϕηη'$ decay

Using (2712.4 $\pm$ 14.3)$\times 10^{6}$ $ψ(3686)$ events collected with the BESIII detector at BEPCII, a partial wave analysis of the decay $ψ(3686) \to ϕηη' $ is performed with the covariant tensor approach. An axial-vector state with a mass near 2.3 $\rm GeV/c^2$ is observed for the first time. Its mass and width are measured to be 2316 $\pm 9_{\mathrm{stat}} \pm 30_{\mathrm{syst}}\,\rm MeV/c^2$ and 89 $\pm 15_{\mathrm{stat}} \pm 26_{\mathrm{syst}}\,\rm MeV$, respectively. The product branching fractions of $\mathcal{B}(ψ(3686) \to X(2300) η') \mathcal{B}(X(2300)\to ϕη)$ and $\mathcal{B}(ψ(3686) \to X(2300) η)\mathcal{B}(X(2300)\to ϕη')$ are determined to be (4.8 $\pm 1.3_{\mathrm{stat}} \pm 0.7_{\mathrm{syst}})\times 10^{-6}$ and (2.2 $\pm 0.7_{\mathrm{stat}} \pm 0.7_{\mathrm{syst}})\times 10^{-6}$, respectively. The branching fraction $\mathcal{B}(ψ(3686) \to ϕηη')$ is measured for the first time to be (3.14$\pm0.17_{\mathrm{stat}}\pm0.24_{\mathrm{syst}})\times10^{-5}$. The first uncertainties are statistical and the second are systematic.

hep-ex↗

arXiv2024

Enhanced primordial gravitational waves from a stiff post-inflationary era due to an oscillating inflaton

We investigate two classes of inflationary models, which lead to a stiff period after inflation that boosts the signal of primordial gravitational waves (GWs). In both families of models studied, we consider an oscillating scalar condensate, which when far away from the minimum it is overdamped by a warped kinetic term, a la $α$-attractors. This leads to successful inflation. The oscillating condensate is in danger of becoming fragmented by resonant effects when non-linearities take over. Consequently, the stiff phase cannot be prolonged enough to enhance primordial GWs at frequencies observable in the near future for low orders of the envisaged scalar potential. However, this is not the case for a higher-order scalar potential. Indeed, we show that this case results in a boosted GW spectrum that overlaps with future observations without generating too much GW radiation to de-stabilise Big Bang Nucleosynthesis. For example, taking $α={\cal O}(1)$, we find that the GW signal can be safely enhanced up to $Ω_{\rm GW}(f)\sim 10^{-11}$ at frequency $f\sim 10^2\,$Hz, which will be observable by the Einstein Telescope (ET). Our mechanism ends up with a characteristic GW spectrum, which if observed, can lead to the determination of the inflation energy scale, the reheating temperature and the shape (steepness) of the scalar potential around the minimum.

hep-ph↗

arXiv2024

Formation of Anisotropic Polarons in Antimony Selenide

Antimony Selenide (Sb$_2$Se$_3$) is an attractive candidate of photovoltaics with not yet satisfying efficiency. Beside defects, polaron formation originated from lattice distortion was proposed to account for trapping free carriers, and the subsequent photoexcitation dynamics and optoelectronic properties, but such a mechanism is still lack of structural observations. Here we directly track the pathways of carrier and lattice evolutions after photoexcitation through optical and electron diffraction pump-probe methods, revealing the temporal correlations between dynamics of both degrees of freedom. The observed opposite separation changes of Se2-Sb2 and Sb2-Sb1 atom pairs in a few picoseconds, and the intermediate state induced by local structural distortions lasting several tens of picoseconds, coinciding with the optical phonons population and coupling, and the trapping process of carriers, respectively, together with the analyses of modulation on diffuse scattering by the atomic displacement fields of polaron model, indicate the formation of anisotropic polarons with large size. Our findings provide carrier and structural information for helping the elucidation of polaron scenario in Sb2Se3, and probably in materials with anisotropic structure and soft lattice which are popular in developing novel optoelectronics.

cond-mat.mtrl-sci↗

arXiv2024

Sine-transform-based fast solvers for Riesz fractional nonlinear Schrödinger equations with attractive nonlinearities

This paper presents fast solvers for linear systems arising from the discretization of fractional nonlinear Schrödinger equations with Riesz derivatives and attractive nonlinearities. These systems are characterized by complex symmetry, indefiniteness, and a $d$-level Toeplitz-plus-diagonal structure. We propose a Toeplitz-based anti-symmetric and normal splitting iteration method for the equivalent real block linear systems, ensuring unconditional convergence. The derived optimal parameter is approximately equal to 1. By combining this iteration method with sine-transform-based preconditioning, we introduce a novel preconditioner that enhances the convergence rate of Krylov subspace methods. Both theoretical and numerical analyses demonstrate that the new preconditioner exhibits a parameter-free property (allowing the iteration parameter to be fixed at 1). The eigenvalues of the preconditioned system matrix are nearly clustered in a small neighborhood around 1, and the convergence rate of the corresponding preconditioned GMRES method is independent of the spatial mesh size and the fractional order of the Riesz derivatives.

math.NA↗

arXiv2024

Hard Negative Sample Mining for Whole Slide Image Classification

Weakly supervised whole slide image (WSI) classification is challenging due to the lack of patch-level labels and high computational costs. State-of-the-art methods use self-supervised patch-wise feature representations for multiple instance learning (MIL). Recently, methods have been proposed to fine-tune the feature representation on the downstream task using pseudo labeling, but mostly focusing on selecting high-quality positive patches. In this paper, we propose to mine hard negative samples during fine-tuning. This allows us to obtain better feature representations and reduce the training cost. Furthermore, we propose a novel patch-wise ranking loss in MIL to better exploit these hard negative samples. Experiments on two public datasets demonstrate the efficacy of these proposed ideas. Our codes are available at https://github.com/winston52/HNM-WSI

cs.CV↗

arXiv2024

Semi-Supervised Contrastive VAE for Disentanglement of Digital Pathology Images

Despite the strong prediction power of deep learning models, their interpretability remains an important concern. Disentanglement models increase interpretability by decomposing the latent space into interpretable subspaces. In this paper, we propose the first disentanglement method for pathology images. We focus on the task of detecting tumor-infiltrating lymphocytes (TIL). We propose different ideas including cascading disentanglement, novel architecture, and reconstruction branches. We achieve superior performance on complex pathology images, thus improving the interpretability and even generalization power of TIL detection deep learning models. Our codes are available at https://github.com/Shauqi/SS-cVAE.

eess.IV↗

arXiv2024

TrojVLM: Backdoor Attack Against Vision Language Models

The emergence of Vision Language Models (VLMs) is a significant advancement in integrating computer vision with Large Language Models (LLMs) to produce detailed text descriptions based on visual inputs, yet it introduces new security vulnerabilities. Unlike prior work that centered on single modalities or classification tasks, this study introduces TrojVLM, the first exploration of backdoor attacks aimed at VLMs engaged in complex image-to-text generation. Specifically, TrojVLM inserts predetermined target text into output text when encountering poisoned images. Moreover, a novel semantic preserving loss is proposed to ensure the semantic integrity of the original image content. Our evaluation on image captioning and visual question answering (VQA) tasks confirms the effectiveness of TrojVLM in maintaining original semantic content while triggering specific target text outputs. This study not only uncovers a critical security risk in VLMs and image-to-text generation but also sets a foundation for future research on securing multimodal models against such sophisticated threats.

cs.CV↗

arXiv2024

OWL: A Large Language Model for IT Operations

With the rapid development of IT operations, it has become increasingly crucial to efficiently manage and analyze large volumes of data for practical applications. The techniques of Natural Language Processing (NLP) have shown remarkable capabilities for various tasks, including named entity recognition, machine translation and dialogue systems. Recently, Large Language Models (LLMs) have achieved significant improvements across various NLP downstream tasks. However, there is a lack of specialized LLMs for IT operations. In this paper, we introduce the OWL, a large language model trained on our collected OWL-Instruct dataset with a wide range of IT-related information, where the mixture-of-adapter strategy is proposed to improve the parameter-efficient tuning across different domains or tasks. Furthermore, we evaluate the performance of our OWL on the OWL-Bench established by us and open IT-related benchmarks. OWL demonstrates superior performance results on IT tasks, which outperforms existing models by significant margins. Moreover, we hope that the findings of our work will provide more insights to revolutionize the techniques of IT operations with specialized LLMs.

cs.CL↗

arXiv2024

Denial-of-Service or Fine-Grained Control: Towards Flexible Model Poisoning Attacks on Federated Learning

Federated learning (FL) is vulnerable to poisoning attacks, where adversaries corrupt the global aggregation results and cause denial-of-service (DoS). Unlike recent model poisoning attacks that optimize the amplitude of malicious perturbations along certain prescribed directions to cause DoS, we propose a Flexible Model Poisoning Attack (FMPA) that can achieve versatile attack goals. We consider a practical threat scenario where no extra knowledge about the FL system (e.g., aggregation rules or updates on benign devices) is available to adversaries. FMPA exploits the global historical information to construct an estimator that predicts the next round of the global model as a benign reference. It then fine-tunes the reference model to obtain the desired poisoned model with low accuracy and small perturbations. Besides the goal of causing DoS, FMPA can be naturally extended to launch a fine-grained controllable attack, making it possible to precisely reduce the global accuracy. Armed with precise control, malicious FL service providers can gain advantages over their competitors without getting noticed, hence opening a new attack surface in FL other than DoS. Even for the purpose of DoS, experiments show that FMPA significantly decreases the global accuracy, outperforming six state-of-the-art attacks.

cs.LG↗

arXiv2024

Competition between $d$-wave and $d$+$is$-wave superconductivity in the Hubbard model on a checkerboard lattice

By employing determinant quantum Monte Carlo simulations, we investigate a checkerboard lattice with next-nearest-neighbor hopping $t'$ as the frustration-control parameter, which exhibits an energetically partial flat-band in the system. Our numerical simulation identifies the dominant pairing symmetry of the checkerboard lattice Hubbard model, and we reveal the competition between the $d$-wave and $d+is$ wave in the parameter space of electron filling $\avg{n}$ and frustration control parameter $t^{\prime}/t$. To ensure the reliability and accuracy of our results, we evaluate the sign problem. We also find that the spin susceptibility, the effective pairing interactions of different pairing symmetries and the superconducting instability are enhanced as the on-site Coulomb interaction increases, demonstrating that superconductivity is driven by strong electron--electron correlation. Our work provides a further understanding of pairing symmetry in the Hubbard model and improves prospects for exploring rich correlated behaviors in frustrated systems.

cond-mat.str-el↗

arXiv2024

Search for $D^0\to K^-ηe^+ν_e$, $D^+\to K_S^0 ηe^+ν_e$ and $D^+\to ηηe^+ν_e$ decays

By analyzing $e^+e^-$ annihilation data corresponding to an integrated luminosity of 7.93 fb$^{-1}$, collected at the center-of-mass energy of 3.773 GeV with the BESIII detector, we search for the semileptonic decays $D^0\to K^-ηe^+ν_e$, $D^+\to K_S^0 ηe^+ν_e$ and $D^+\to ηηe^+ν_e$ for the first time. We present evidence for $D^0\to K^-ηe^+ν_e$ with a significance of $3.3σ$. The branching fraction of $D^0\to K^-ηe^+ν_e$ is measured to be $(0.84_{-0.34}^{+0.29}\pm0.22)\times 10^{-4}$. Here, the first uncertainties are statistical and the second ones are systematic. No significant signals are observed for the decays $D^+\to K_S^0 ηe^+ν_e$ and $D^+\to ηηe^+ν_e$ and we set the upper limits on their branching fractions.

hep-ex↗

arXiv2024

Search for $X(3872)\toπ^0π^0χ_{c1,2}$

Using 10.1 fb$^{-1}$ of $e^+e^-$ collision data collected by the BESIII detector with center-of-mass energies between 4.15 GeV and 4.30 GeV, we search for the decays $X(3872)\toπ^0π^0χ_{c1,2}$, where the $X(3872)$ is produced in $e^+e^-\toγX(3872)$. No evidence above $3σ$ is found for either decay. Upper limits at the $90\%$ C.L. on the branching fractions of $X(3872)\toπ^0π^0χ_{c1,2}$ normalized to the branching fraction of $X(3872)\toπ^+π^-J/ψ$ are set to be $\mathcal{B}(X(3872)\toπ^0π^0χ_{c1})/\mathcal{B}(X(3872)\toπ^+π^-J/ψ) < 1.1$ and $\mathcal{B}(X(3872)\toπ^0π^0χ_{c2})/\mathcal{B}(X(3872)\toπ^+π^-J/ψ) < 0.5$, taking into account both statistical and systematic uncertainties.

hep-ex↗

arXiv2024

Measurements of the $CP$-even fractions of $D^0\toπ^{+}π^{-}π^{0}$ and $D^0\to K^{+}K^{-}π^{0}$ at BESIII

The $CP$-even fractions ($F_{+}$) of the decays $D^0\toπ^{+}π^{-}π^{0}$ and $D^0\to K^{+}K^{-}π^{0}$ are measured with a quantum-correlated $ψ(3770)\to D\bar{D}$ data sample collected by the BESIII experiment corresponding to an integrated luminosity of 7.93 $\mathrm{fb}^{-1}$. The results are $F_{+}^{π^{+}π^{-}π^{0}}=0.9406\pm0.0036\pm0.0021$ and $F_{+}^{K^{+}K^{-}π^{0}}=0.631\pm0.014\pm0.011$, where the first uncertainties are statistical and the second systematic. These measurements are consistent with the previous determinations, and the uncertainties for $F_{+}^{π^{+}π^{-}π^{0}}$ and $F_{+}^{K^{+}K^{-}π^{0}}$ are reduced by factors of 3.9 and 2.6, respectively. The reported results provide important inputs for the precise measurement of the angle $γ$ of the Cabibbo-Kobayashi-Maskawa matrix and indirect $CP$ violation in charm mixing.

hep-ex↗