Next-generation high-energy electron-positron colliders, operating as Higgs factories, require an unprecedented jet energy resolution for precision measurements of Higgs and Z/W bosons. To address this challenge, a conceptual design is presented for a novel high-granularity crystal electromagnetic calorimeter that combines the superior intrinsic energy resolution of a homogeneous calorimeter with the fine segmentation required for particle-flow reconstruction. The crystal electromagnetic calorimeter design is based on orthogonally arranged long scintillating crystal bars read out by silicon photomultipliers (SiPMs) at both ends. Key design specifications were established through comprehensive simulation studies. Critical technical considerations, including crystal choices, photosensors, electronics, mechanical support, and radiation damage, are discussed. A dedicated digitisation framework was developed to realistically model effects from the crystal, SiPMs, and readout electronics. The performance of a single calorimeter module was evaluated using simulated electron showers. Simulation results for a single module demonstrate an excellent electromagnetic energy resolution of 1.12%/√(E(GeV))⊕0.22% and an energy linearity within ±0.5% for electrons from 3 GeV to 100 GeV. The performance significantly exceeds the design requirement of ≤ 3%/√(E(GeV))⊕1%. The results establish the feasibility of the proposed high-granularity crystal calorimeter concept and point to a promising pathway toward the precision calorimetry required for future high-energy electron-positron collider experiments.

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.

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.

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.

In the BESIII detector at Beijing electron–positron collider, billions of events from e^+e^- collisions were recorded. These events passing through the trigger system were saved in raw data format files. They play an important role in the study of physics in τ -charm energy region. Here, we published an e^+e^- collision dataset containing both Monte Carlo simulation samples and real data collected by the BESIII detector. The data pass through the detector trigger system, file format conversion, and physics information extraction and finally save the physics information and detector response in text format files. This dataset is publicly available and is intended to provide interested scientists and those outside of the BESIII collaboration with event information from BESIII, which can be used to understand physics research in e^+e^- collisions, developing visualization projects for physics education, public outreach, and science advocacy.

The BESIII experiment functions as an electron-positron collider in the tau-charm energy region, dedicated to investigating various physics objectives related to charm, charmonium, and light hadron decays. Within these goals, the accurate identification of particles plays a pivotal role, ensuring both high efficiency and minimal systematic uncertainty. In the context of the BESIII experiment, the particle identification performance heavily depends on two key measurements: the energy deposition per unit length (dE/dx) acquired from the main drift chamber sub-detector and the time-of-flight measurement from the time-of-flight sub-detector. This paper specifically delves into the dE/dx aspect, presenting a comprehensive overview of the dE/dx software utilized in the BESIII experiment, encompassing simulation, correction, calibration, and reconstruction processes.

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.

We measure the Born cross section for the reaction e+e−→ηhc from s=4.129 to 4.600 GeV using datasets collected by the BESIII detector running at the BEPCII collider. A resonant structure in the cross-section line shape near 4.200 GeV is observed with a statistical significance of 7σ. The parameters of this resonance are measured to be M=4188.8±4.7±8.0 MeV/c2 and Γ=49±16±19 MeV, where the first uncertainties are statistical and the second systematic. Published by the American Physical Society 2025

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 tracking and identification of charged particles are always essential for robust data analysis and comprehensive understanding of detector performance. As electrons and positrons constitute an important part of final state particles at BESIII, their tracking and identification efficiency should be investigated, which is useful for many experimental studies. The efficiencies for electron and positron tracking and identification in the BESIII experiment are investigated with the radiative Bhabha process e^+e^-→ e^+e^-γ from the data samples collected at the center-of-mass energies of 3.08 GeV and 3.097 GeV. The relative differences between data and MC associated with tracking and identification efficiencies of electrons and positrons, as well as the corresponding correction factors are determined here. The relative differences of tracking efficiency and particle identification efficiency after correction are mostly less than 0.5 % for transverse momenta p_T>0.4 GeV and for the entire momentum region, respectively. It is shown that the BESIII detector has good performance on the electron and positron detection and identification. This method and the two-dimensional distribution of p/p_T versus cosθ can be widely used in the systematic uncertainty studies for various experimental measurements.

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.

The CEPC clock issue is related with the RF frequency coordination between the various accelerator systems and may affect the operation modes of both the accelerator and the detector. The timing structure of CEPC has been restudied with the collaboration of the accelerator team and the detector team. After discussions between two sides, the CEPC bunch structure is set such that the spacings between adjacent bunches in any CEPC operation mode are integer numbers of 23.08 ns. The master CEPC clock will be provided by the accelerator to the detector systems with a frequency of 43.33 MHz, synchronous to the beam. The CEPC detector system relies on the clock to sample physics signal at the right time. It was found that if the circumference of CEPC is slightly changed to 99955.418 m, not only is the orbit length closer to 100 km, but also the detector would benefit more for the first 10-year operation.

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.

Using $e^+ e^-$ collision data collected at the BESIII detector at center-of-mass energies between 4.128 and 4.226 GeV, corresponding to an integrated luminosity of $7.33~{\rm fb}^{-1}$, we determine the absolute branching fractions of fifteen hadronic $D_s^{+}$ decays with a double-tag technique. In particular, we make precise measurements of the branching fractions $\mathcal{B}(D_s^+ \to K^+ K^- \pi^+)=(5.49 \pm 0.04 \pm 0.07)\%$, $\mathcal{B}(D_s^+ \to K_S^0 K^+)=(1.50 \pm 0.01 \pm 0.01)\%$ and $\mathcal{B}(D_s^+ \to K^+ K^- \pi^+ \pi^0)=(5.50 \pm 0.05 \pm 0.11)\%$, where the first uncertainties are statistical and the second ones are systematic. The \emph{CP} asymmetries in these decays are also measured and all are found to be compatible with zero.

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).