To explore the feasibility of high-precision particle identification using the cluster counting technique for the drift chamber, a dedicated readout electronics system with low noise, high bandwidth, and high sampling rate is required. This paper presents the design and performance evaluation of a scalable readout prototype developed for this application. The system architecture integrates a custom front end with a 1.3 GSps waveform sampling back end, implemented within a modular 120-channel framework. Laboratory characterization of the 40-channel prototype demonstrates a -3 dB analog bandwidth of 550 MHz and an equivalent noise input current of 0.83 μA_rms . These specifications are essential for preserving the fast temporal features of ionization signals. Furthermore, the system achieves an intrinsic timing jitter of 0.88 ns , which satisfies the timing precision requirements for drift distance measurement. Joint experiments with a drift chamber prototype using cosmic rays verified the system’s capability to resolve discrete ionization peaks within pileup waveforms. The presented results confirm that the readout electronics provide the signal fidelity and temporal resolution necessary for future cluster counting algorithm development.

A bstract Particle identification (PID) is essential for future particle physics experiments such as the Circular Electron-Positron Collider (CEPC) and the Future Circular Collider. A high-granularity Time Projection Chamber (TPC) not only provides precise tracking but also enables d N /d x measurements for PID. The d N /d x method estimates the number of primary ionization electrons, offering significant improvements in PID performance. However, accurate reconstruction remains a major challenge for this approach. In this paper, we introduce a deep learning model, the Graph Point Transformer (GraphPT), for d N /d x reconstruction. In our approach, TPC data are represented as point clouds. The network backbone adopts a U-Net architecture built upon graph neural networks, incorporating an attention mechanism for node aggregation specifically optimized for point cloud processing. The proposed GraphPT model surpasses the traditional truncated mean method in PID performance. In particular, for the CEPC baseline TPC, the K/π separation power improves by approximately 10% to 20% in the momentum interval from 5 to 20 GeV/ c .

Photon reconstruction in calorimeters represents a crucial challenge in particle physics experiments, especially in high-density environments where shower overlapping probabilities become significant. We present an energy-core-based photon reconstruction method. It is achieved through extending the application of the Hough transform to exploit the energy-core structure of photon showers. The method, validated through simulations of the CEPC crystal electromagnetic calorimeter, demonstrates outstanding performance. It achieves a reconstruction efficiency of nearly 100

Crystal electromagnetic calorimeters (ECALs) are essential for high-precision measurements of electrons and photons in particle physics experiments. However, the conventional design, in which long crystal bars point radially toward the interaction region and lack longitudinal segmentation, is incompatible with the three-dimensional shower imaging required by Particle Flow Approach (PFA). We propose a novel perspective on crystal ECAL design to address this limitation. The key innovation is a geometric reconfiguration in which crystal bars are oriented to face the interaction region and arranged orthogonally in adjacent longitudinal layers. This layout achieves fine spatial segmentation of energy deposits by correlating measurements of orthogonal crystal bars. An interleaved structure of regular and inverted trapezoidal modules is incorporated to maximize structural uniformity and detector hermeticity. This design is engineered to preserve the excellent intrinsic energy resolution of crystal ECALs while simultaneously providing the detailed three-dimensional shower imaging essential for PFA. Simulation results confirm the feasibility of achieving excellent energy resolution of 1.14%/√(E)⊕ 0.44%. Consequently, the proposed design repositions crystal ECAL as a foundational component for PFA-oriented detector systems at facilities such as the Circular Electron Positron Collider (CEPC), offering a new technical pathway to advance the physics goals of future colliders.

Based on 6.1  fb^{-1} of e^{+}e^{-} annihilation data collected at center-of-mass energies from 4.600 to 4.843 GeV with the BESIII detector at the BEPCII collider, a partial wave analysis of Λ_{c}^{+}→Λπ^{+}η is performed, and branching fractions and decay asymmetry parameters of intermediate processes are determined. The process Λ_{c}^{+}→Λa_{0}(980)^{+} is observed for the first time, and evidence for the pentaquark candidate Σ(1380)^{+} decaying into Λπ^{+} is found with statistical significance larger than 3σ with mass and width fixed to theoretical predictions. The branching fraction product B[Λ_{c}^{+}→Λa_{0}(980)^{+}]B[a_{0}(980)^{+}→π^{+}η] is determined to be (1.05±0.16_{stat}±0.05_{syst}±0.07_{ext})%, which is larger than theoretical calculations by 1-2 orders of magnitude. Here the third (external) systematic is from B(Λ_{c}^{+}→Λπ^{+}η). Finally, we precisely obtain the absolute branching fraction B(Λ_{c}^{+}→Λπ^{+}η)=(1.94±0.07_{stat}±0.11_{syst})%.

The process e^+e^-→K_S^0K_S^0ψ (3686) is studied by analyzing e+e− collision data samples collected at eight center-of-mass energies ranging from 4.682 to 4.951 GeV with the BESIII detector operating at the BEPCII collider, corresponding to an integrated luminosity of 4.1 fb−1. Observation of the e^+e^-→K_S^0K_S^0ψ (3686) process is found for the first time with a statistical significance of 6.3σ, and the cross sections at each center-of-mass energy are measured. The ratio of cross sections of e^+e^-→K_S^0K_S^0ψ (3686) relative to e+e− → K+K−ψ(3686) is determined to be σ(e^+e^-→K_S^0K_S^0ψ (3686))/σ(e^+e^-→K^+K^-ψ (3686))=0.45± 0.25 , which is consistent with the prediction based on isospin symmetry. The uncertainty includes both statistical and systematic contributions. Additionally, the K_S^0ψ (3686) invariant mass distribution is found to be consistent with three-body phase space. The significance of a contribution beyond three-body phase space is only 0.8σ.

The particle identification (PID) of hadrons plays a crucial role in particle physics experiments, especially in flavor physics and jet tagging. The cluster-counting method, which measures the number of primary ionizations in gaseous detectors, is a promising breakthrough in PID. However, developing an effective reconstruction algorithm for cluster counting remains challenging. To address this challenge, we propose a cluster-counting algorithm based on long short-term memory and dynamic graph convolutional neural networks for the CEPC drift chamber. Experiments on Monte Carlo simulated samples demonstrate that our machine-learning-based algorithm surpasses traditional methods. It improves the K/π separation of PID by 10%, meeting the PID requirements of CEPC.

Due to high spatial resolution, low material budget and good particle identification (PID) performance, drift chamber is an important choice for CEPC trackers. In order to improve the PID capability of drift chambers, an innovative cluster counting method (dN/dx) is proposed. Unlike the dE/dx method by measuring the energy loss directly, the dN/dx method measures the number of primary ionizations along the trajectories of particles as they pass through the drift chamber. In this study, a test system with a detector prototype and fast readout electronics was set up and tested with an electron beam. Derivative-based reconstruction algorithm was adopted for the peak finding and clusterization in the signal waveforms. The test results show that the mean noise is about 0.9 mV, and the rise time of most peaks is less than 3 ns, which indicates that the system has low noise and high bandwidth, and can be used to accurately measure the ionization signals. The preliminary test results have basically validated the feasibility of the dN/dx method.

Based on a sample of (2712.4 ± 14.3) × 106 ψ(3686) events collected with the BESIII detector, a partial wave analysis of the decay ψ (3686)→ΛΣ^0π^0 + c.c. is performed to investigate Λ* and Σ* resonances in the π^0Σ^0 and π0Λ invariant mass distributions. Significant contributions are found from the Λ(1405), Λ(1520), Λ(1600), Λ(1670), Λ(1690), Λ(1800), Λ(1890), Λ(2325), Σ(1385), Σ(1660), Σ(1670), Σ(1750), and Σ(1910). The masses, widths, and production branching fractions for each component are determined. In addition, the branching fraction of ψ (3686)→ΛΣ^0π^0 + c.c. is measured to be (1.544 ± 0.013 ± 0.071) × 10−4 for the first time, where the first uncertainty is statistical and the second systematic.

A bstract Based on 7.33 fb − 1 of e + e − collision data collected by the BESIII detector operating at the BEPCII collider at center-of-mass energies from 4.128 to 4.226 GeV, a search for the Majorana neutrino ν m is conducted in the lepton-number-violating decays of $$ {D}_{\textrm{s}}^{+} $$ D s + → h − h 0 e + e + . Here, h − represents a K − or π − , and h 0 represents a π 0 , $$ {K}_S^0 $$ K S 0 or ϕ . No significant signal is observed, and the upper limits of their branching fractions at the 90% confidence level are determined to be $$ \mathcal{B} $$ B ( $$ {D}_{\textrm{s}}^{+} $$ D s + → ϕπ − e + e + ) < 6 . 9 × 10 − 5 , $$ \mathcal{B} $$ B ( $$ {D}_{\textrm{s}}^{+} $$ D s + → ϕK − e + e + ) < 9 . 9 × 10 − 5 , $$ \mathcal{B} $$ B ( $$ {D}_{\textrm{s}}^{+} $$ D s + → $$ {K}_S^0 $$ K S 0 π − e + e + ) < 1 . 3 × 10 − 5 , $$ \mathcal{B} $$ B ( $$ {D}_{\textrm{s}}^{+} $$ D s + → $$ {K}_S^0 $$ K S 0 K − e + e + ) < 2 . 9 × 10 − 5 , $$ \mathcal{B} $$ B ( $$ {D}_{\textrm{s}}^{+} $$ D s + → π − π 0 e + e + ) < 2 . 9 × 10 − 5 and $$ \mathcal{B} $$ B ( $$ {D}_{\textrm{s}}^{+} $$ D s + → K − π 0 e + e + ) < 3 . 4 × 10 − 5 . The Majorana neutrino is searched for with different mass assumptions within the range [0 . 20 , 0 . 80] GeV /c 2 in the decay of $$ {D}_{\textrm{s}}^{+} $$ D s + → ϕe + ν m with ν m → π − e + , and the upper limits of the branching fractions at the 90% confidence level are at the level of 10 − 5 –10 − 2 , depending on the mass of the Majorana neutrino.

A bstract By analyzing e + e − collision data with an integrated luminosity of 7.9 fb − 1 collected with the BESIII detector at the center-of-mass energy of 3.773 GeV, the branching fraction of D + → τ + ν τ is determined as $$ \mathcal{B} $$ B = (9.9 ± 1.1 stat ± 0.5 syst ) × 10 − 4 . Using the most precise result $$ \mathcal{B} $$ B ( D + → μ + ν μ ) = (3.981 ± 0.079 stat ± 0.040 syst ) × 10 − 4 [1], we determine R τ/μ = Γ( D + → τ + ν τ )/Γ( D + → μ + ν μ ) = 2.49 ± 0.31, achieving a factor of two improvement in precision compared to the previous BESIII result. This measurement is in agreement with the standard model prediction of lepton flavor universality within one standard deviation.

The Circular Electron-Positron Collider (CEPC), as the next-generation electron-positron collider, is tasked with advancing not only Higgs physics but also the discovery of new physics. Achieving these goals requires high-precision measurements of particles. Taichu seires, Monolithic Active Pixel Sensor (MAPS), a key component of the vertex detector for CEPC was designed to meet the CEPC's requirements. For the geometry of vertex detector is long barrel with no endcap, and current silicon lacks a complete digitization model, precise estimation of cluster size particularly causing by particle with large incident angle is needed. Testbeam results were conducted at the Beijing Synchrotron Radiation Facility (BSRF) to evaluate cluster size dependence on different incident angles and threshold settings. Experimental results confirmed that cluster size increases with incident angle. Simulations using the Allpix^2 framework replicated experimental trends at small angles but exhibited discrepancies at large angles, suggesting limitations in linear electric field assumptions and sensor thickness approximations. The results from both testbeam and simulations have provided insights into the performance of the TaichuPix chip at large incident angles, offering a crucial foundation for the establishment of a digital model and addressing the estimation of cluster size in the forward region of the long barrel. Furthermore, it offers valuable references for future iterations of TaichuPix, the development of digital models, and the simulation and estimation of the vertex detector's performance.

Using (10087 ± 44) × 10^6 J/ψ events collected with the BESIII detector in 2009, 2012, 2018 and 2019, the tracking efficiency of charged pions is studied using the decay J/ψ→π^+ π^- π^0. The systematic uncertainty of the tracking efficiency and the corresponding correction factors for charged pions are evaluated, in bins of transverse momentum and polar angle of the charged pions.

The Circular Electron Positron Collider (CEPC) is a large-scale scientific project proposed by the Chinese high-energy physics community. In the updated CEPC Physics and Detector Technical Design Report (TDR), the baseline detector design concept features a large gaseous Time Projection Chamber (TPC) as the main tracker detector (MTK). Accurate momentum resolution is critical for precision physics measurements at the CEPC. As a lepton collider, the CEPC provides a cleaner environment than hadron colliders, but inevitably contains a certain amount of background. Beam-induced background is the primary source of space charge in the TPC, which may degrade the TPC performance and pose challenges for its operation. In this paper, two types of beam-induced background in the CEPC Higgs and low luminosity Z modes are generated according to the CEPC accelerator parameters. These background seeds are exported to Geant4 for detailed detector simulation and space charge density estimation. The space charge in the TPC is mainly caused by the interaction of low-energy photons with the working gas. The space charge density in the CEPC TPC is only about 1/60 of the ALICE TPC in the Higgs mode. However, further optimization strategies are required to mitigate the background, particularly in the low luminosity Z mode.

Using 20.3  fb^{-1} of e^{+}e^{-} collision data collected at a center-of-mass energy of E_{c.m.}=3.773  GeV with the BESIII detector operating at the BEPCII collider, we determine the branching fraction of the leptonic decay D^{+}→μ^{+}ν_{μ} to be (4.034±0.080_{stat}±0.040_{syst})×10^{-4}. Interpreting our measurement with knowledge of the Fermi coupling constant G_{F}, the masses of the D^{+} and μ^{+} as well as the lifetime of the D^{+}, we determine f_{D^{+}}|V_{cd}|=(48.02±0.48_{stat}±0.24_{syst}±0.12_{input}±0.15_{EM})  MeV after taking into account necessary radiative corrections. This result is a factor of 2.3 more precise than the previous best measurement. Using the value of the magnitude of the c→d Cabibbo-Kobayashi-Maskawa matrix element |V_{cd}| given by the global standard model fit, we obtain the D^{+} decay constant f_{D^{+}}=(213.5±2.1_{stat}±1.1_{syst}±0.8_{input}±0.7_{EM})  MeV. Alternatively, using the value of f_{D^{+}} from a precise lattice quantum chromodynamics calculation, we extract |V_{cd}|=0.2265±0.0023_{stat}±0.0011_{syst}±0.0009_{input}±0.0007_{EM}.

Utilizing a dataset 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(-) -> phi chi(c0) and phi eta(c2)(1D) across centerof-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 dressed cross sections for e(+)e(-) -> phi chi(c0), as well as the product of the dressed cross section for e(+)e(-) -> phi eta(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) ->phi chi(c0), denoted as Gamma Y-e+e-((4660)) B-Y(4660)->phi chi(c0), is determined to be <0.35 eV at the 90% confidence level.

One of the main goals of studying semileptonic decays in flavor physics is to gain a better understanding of hadronic transitions in the nonperturbative region of Quantum Chromodynamics. This involves measuring Cabibbo-Kobayashi-Maskawa matrix elements, understanding form factors, and comparing them with theoretical predictions. We report a first study of the semileptonic decay D^{0}→K^{-}π^{0}μ^{+}ν_{μ} by analyzing an e^{+}e^{-} annihilation data sample of 7.93  fb^{-1} collected at the center-of-mass energy of 3.773 GeV with the BESIII detector. The absolute branching fraction of D^{0}→K^{-}π^{0}μ^{+}ν_{μ} is measured for the first time, providing necessary input for extracting the c→s Cabibbo-Kobayashi-Maskawa matrix element through this process. This measurement allows us to test lepton flavor universality, with no indication of violation found. Furthermore, a series of hadronic form factors have been determined and compared with theoretical predictions, which will impose stricter constraints on theoretical models.

Using e+e− collision data collected with the BESIII detector at the BEPCII collider at center-of-mass energies between 3.510 and 4.914 GeV, corresponding to an integrated luminosity of 25 fb−1, we measure the Born cross sections for the process e^+e^-→K^-Ξ^+Λ /Σ^0 at thirty-five energy points with a partial-reconstruction strategy. By fitting the dressed cross sections of e^+e^-→K^-Ξ^+Λ /Σ^0 , evidence for ψ (4160)→K^-Ξ^+Λ is found for the first time with a significance of 4.4σ, including systematic uncertainties. No evidence for other possible resonances is found. In addition, the products of electronic partial width and branching fraction for all assumed resonances decaying into K^-Ξ^+Λ /Σ^0 are determined.

Based on (2.712 +/- 0.014) x 10(9) psi(3686) events collected by the BESIII Collaboration, evidence of the hadronic decay h(c) -> (KSK+)-K-0 pi(-) + c.c. is found with a significance of 4.3 sigma in the psi(3686) -> pi(0)h(c) process. The branching fraction of h(c) -> (KSK+)-K-0 pi(-) + c.c. is measured to be (7.3 +/- 1.8 +/- 0.8) x 10(-4), where the first and second uncertainties are statistical and systematic, respectively. Combining with the exclusive decay width of eta(c) -> K (K) over bar pi, our result indicates inconsistencies with both pQCD and NRQCD predictions.

Based on (10.09 +/- 0.04) x 10(9) J/psi events collected with the BESIII detector operating at the BEPCII collider, a partial wave analysis of the decay J/psi -> phi pi(0 eta). is performed. We observe for the first time two new structures on the phi eta invariant mass distribution, with significances exceeding 27 sigma and 13 sigma; the first with J(PC) = 1(+-), mass M = (1908 +/- 6(stat)(-4)(+8) (sys)) MeV/c(2), and width Gamma = (175 +/- 13(stat)(-16)(+7) (sys)) MeV, the second with J(PC) = 1(--), mass M = (1992 +/- 12 (stat)(-6)(+15) (sys)) MeV/c(2), and width Gamma = (132 +/- 22(stat)(-4)(+17) (sys)) MeV. These measurements provide important input for the strangeonium spectrum. In addition, the f(0) (980) - a(0)(980)(0) mixing signal in J/psi -> phi f(0)(980) -> phi a(0)(980)(0) and the corresponding electromagnetic decay J/psi -> phi a(0)(980)(0) are measured with improved precision, providing crucial information to understand the nature of a(0)(980)(0) and f(0)(980).