The 2025 International Workshop on the High Energy Circular Electron Positron Collider

I present the calculation of complete next-to-leading order electroweak corrections to the Higgs boson production in $gg\to g H$ channel as well as it's rare decay.
We apply the method of differential equations combined with the selection of optimized master integrals to accomplish the calculation of master integrals. We consider three distinct renormalization schemes.
At leading order, the differential distributions and the total cross section show a strong dependence on the renormalization scheme. However, these discrepancies are considerably suppressed once electroweak corrections are taken into account. For $G_\mu$ scheme, the electroweak correction amounts to approximately $4.3\%$ of the total cross section. Importantly, {\color{red} we find that the EW corrections exhibit a strong dependence on Higgs transverse momentum.

Composite asymmetric dark matter (ADM) models provide a well-motivated paradigm that simultaneously explains dark matter (DM) relic density and matter-antimatter asymmetry. In these models, the mass of the DM candidate (the lightest dark baryon) is generated through the dark confinement scale dynamics. Although the leptophilic composite ADM model offers a viable framework, comprehensive studies of its collider phenomenology are absent. This work systematically explores novel signatures from leptophilic composite asymmetric dark sector at both low-energy and high-energy $e^+e^-$ colliders as well as other existing collider constraints. We demonstrate detectability of TeV-scale mediators along with sub-GeV to GeV-scale lightest dark mesons at Belle II and its proposed far detector, GAZELLE, as well as CEPC experiments. Moreover, these experiments exhibit complementary coverage of the model parameter space.

The CEPC Silicon Tracker, comprising the Inner Silicon Tracker (ITK) and Outer Silicon Tracker (OTK), will cover a total active area of approximately 100 m². It integrates advanced pixel sensors for the ITK and microstrip sensors for the OTK, with micron-level precision to achieve per-mille-level momentum resolution, measuring charged-particle trajectories from below 1 GeV/c to above 100 GeV/c. The detector will also serve as a high-precision Time-of-Flight system, targeting a single-layer timing resolution of 50 ps. By combining high-performance sensors, electronics, mechanics, and cooling, the design of the reference detector for the CEPC has been finalized, and the corresponding R&D work is ongoing. This presentation provides a comprehensive overview of the detector design, as well as the current status and future plans for system development.

This presentation details a study of the prospective measurement of the cross-section times branching ratio for Higgs decaying into two photons, $\sigma(e^{+}e^{-} \rightarrow ZH) \times \mathrm{Br}(H \rightarrow \gamma\gamma)$, at the Circular Electron Positron Collider (CEPC). The analysis is performed at a center-of-mass energy of $\sqrt{s} = 240$ GeV, considering the three dominant $Z$ boson decay channels: $Z \rightarrow q\bar{q}$, $\mu^{+}\mu^{-}$, and $\nu\bar{\nu}$. Using simulated Monte Carlo events corresponding to an integrated luminosity of $21.6~\text{ab}^{-1}$, a combined statistical precision of $3.1\%$ is achieved. Furthermore, we investigate the impact of the electromagnetic calorimeter (ECAL) performance by studying the degradation of the photon energy resolution. Our results indicate that the stochastic term is the dominant factor, and a transition from a Silicon-Tungsten to a glass bar ECAL design significantly improves the energy resolution, thereby enhancing the precision of the $H \rightarrow \gamma\gamma$ measurement.

It is not excluded by the LHC experiments that the SM-like Higgs boson is a mixture of CP eigenstates of opposite parities. In such a scenario, the mixing angle can be measured at CEPC in Higgs to tau-pair decays. We present a preliminary result of the mixing angle measurement obtained with the fast simulation of the CEPC detector.

Embed in Grassmannians, we can obtain the analytical hypergeometric function solutions of multi-loop Feynman integrals with masses. We can make the classification among those hypergeometric solutions by geometric configurations. We can generalize Gauss relations among the hypergeometric functions to complete analytic continuation of the solutions. This method can be applicable to the high-order corrections of physical quantities in future high-precision colliders.

In this talk, I will present a comprehensive study of Higgs boson production associated with a neutrino pair at $e^+ e^−$ colliders ($e^+ e^- \to h \nu \bar{\nu}$) at NLO electroweak (EW) accuracy in both the SM and the two-Higgs-doublet model (2HDM). I will show that new physics effects from the extended Higgs sector can be probed through EW corrections, which lead to deviations from the SM predictions reaching 6% to 7%. Even in the alignment limit, these deviations can still reach 2% to 3%, making them experimentally testable. This highlights the potential of precision studies at future $e^+ e^−$ colliders for searching new physics.

The ATLAS and CMS experiments are unique drivers of our fundamental understanding of nature at the energy frontier. In this contribution to the update of the European Strategy for Particle Physics, we update the physics reach of these experiments at the High-Luminosity LHC (HL-LHC) in a few key areas where they will dominate the state-of-the-art for decades to come.

Several excesses around 95 GeV hint at an additional light scalar beyond the Standard Model. We examine the CEPC's capability to test this hypothesis via the Higgsstrahlung channel $e^+e^-\to ZS$ ($Z\to\mu^+\mu^-$, $S\to\tau^+\tau^-/b\bar{b}$). Our results show that a 210 GeV CEPC run with deep neural networks robustly probes the 95 GeV excess, covering large model parameter spaces. We also discuss future hadron colliders (HL-LHC, HE-LHC, FCC-hh, SppC) for contrast, and use representative models (MDM, Type-I 2HDM, flipped N2HDM, NMSSM) to illustrate these colliders' reach.

The Future Circular Collider (FCC) is a post-LHC project presenting unparalleled opportunities to thoroughly examine Higgs properties. The electron-positron stage of FCC (FCC-ee), featuring operation modes at 240 and 365 GeV, will produce millions of Higgs bosons through the ZH and VBF processes. Benefiting from the clean experimental environment and the precisely known center-of-mass energy, model-independent measurements of the ZH cross-section and total Higgs width can be performed at per-mil precision. Utilizing the recoil-mass technique, the Higgs boson mass will be measured with a precision of a few MeV. With the efficient particle reconstruction and flavor tagging performance, Higgs couplings to quarks and gluons can be probed with sub-percent to percent precision. This talk summarizes the prospects of Higgs physics at FCC-ee.

We evaluate the experimental sensitivity to the $CP$-odd admixture in the standard Higgs boson in the process $e^+e^- \to HZ$, which is expected at future lepton collider CEPC with $\sqrt{s}=240~\text{GeV}$ and statistics of $5.6~\text{ab}^{-1}$. Using the Whizard generator with Higgs Characterisation model and DELPHES detector simulation framework we obtain data samples with different $CP$-odd Higgs admixture parameters $\tilde{c}_{ZZ}$. The initial state radiation (ISR) effects are taken into account in Whizard. Angular and ISR energy shift distributions are used to distinguish the $CP$-odd and $CP$-even Higgs components. Upper limits on the $CP$-odd Higgs admixture parameter are obtained.

High-Voltage CMOS (HV-CMOS) pixel detectors, with excellent radiation hardness and fast signal collection enabling nanosecond-level timing and micron-level spatial resolution, are chosen as the baseline for the CEPC Inner Silicon Tracker. Our R&D using a 55 nm process has produced the COFFEE series of prototype chips. Following verification with COFFEE2, the COFFEE3 chip was designed and submitted for tape-out in spring 2025. COFFEE3 implements two readout architectures: one digitizes within each pixel and transmits data in parallel to the array bottom for time stamping, while the other uses a pixel-level Time-to-Digital Converter (TDC) with column-level readout. Both aim for sub-5 ns timing, optimized differently for hit-rate handling and power. This talk will present the COFFEE series R&D, the COFFEE3 design and performance, preliminary test results, and future plans.

AC-coupled Low Gain Avalanche Detectors (AC-LGADs) have become leading contenders for upcoming 4D tracking systems, attracting considerable interest from numerous research organizations. These detectors have been selected as the Outer Tracker (OTK) detectors for the Circular Electron Positron Collider (CEPC), as the detector can provide both high-precision spatial resolution (∼10 µm) for momentum measurement and high-precision timing (∼ 50 ps) for particle identification. Research on AC-LGADs developed by the Institute of High Energy Physics (IHEP), featuring 5.65-mm-long strip sensors, has shown impressive results, with a timing resolution of about 40 picoseconds and a spatial resolution of approximately 10 micrometers. Total Ionizing Dose (TID) radiation studies have further indicated that these sensors maintain strong performance under CEPC's radiation conditions. Towards CEPC OTK system, An AC-LGAD with a strip length of ~4 cm has been designed, and its performance be evaluated. This presentation includes simulations of AC-LGAD design parameters, including n+ layer dose, isolation structures and so on, with a focus on capacitance optimization aimed at enhancing performance. The design of IHEP's AC-LGAD strip sensors and the preliminary testing results of AC-LGAD sensors with long strips will also be reported.

Low Gain Avalanche Detectors (LGADs) exhibit excellent properties, including ultra-fast time resolution and a high signal-to-noise ratio. They are widely used in high-energy physics experiments for precise particle detection and time-of-flight measurements. However, irradiation introduces deep-level defects and causes detector performance degradation. Therefore, improving the radiation hardness of LGADs is essential. In this work, capacitance-transient deep-level transient spectroscopy (c-DLTS) and current-transient deep-level transient spectroscopy (i-DLTS) were employed to investigate PINs and LGADs under various neutron and proton irradiation fluences. The defect parameters, including activation energies, capture cross sections, and concentrations, were analyzed. The results show that, compared with i-DLTS, c-DLTS is more sensitive to shallow-level defects. However, at high irradiation fluences, due to increased leakage current and device degradation, c-DLTS may fail to detect defects, while i-DLTS can still reveal typical deep-level defects (e.g., CiOi). Furthermore, under the same irradiation fluence, PINs can resolve both shallow- and deep-level defects, whereas shallow-level defects are hardly observable in LGADs. This phenomenon may be attributed to the gain-layer structure and electric-field effects. Therefore, PINs can serve as a reference for shallow-level defects in LGADs. With increasing irradiation fluence, the variety of observable defects increases, and the concentrations of specific defects (e.g., CiOi and BiOi) rise significantly. Both BiOi and CiOi are directly or indirectly related to the acceptor removal phenomenon, which further accelerates gain degradation in LGADs. The quantitative correlation of these defect concentrations thus provides important guidance for designing radiation-hard LGADs.

The CEPC silicon tracker (ITK and OTK) will cover a large sensor area of approximately 100 m². Achieving high performance requires minimizing the material budget while ensuring high structural strength and efficient cooling—a particular challenge for this large and sophisticated tracking system. This report presents the detailed mechanical and cooling design of the CEPC silicon tracker detectors, along with the planned R&D toward a prototype detector.

Precise jet energy reconstruction at the Circular Electron Positron Collider (CEPC) requires an advanced calorimetry system. A novel design for a particle-flow-oriented, high-granularity electromagnetic calorimeter (ECAL) has been proposed, featuring orthogonally layered crystal bars with silicon photomultiplier (SiPM) readout and a target energy resolution of $2\text{-}3\%/\sqrt{E\ (\mathrm{GeV})}\oplus1\%$. After a three-year development and test cycle, a physics prototype with dimensions of $12\times12\times26\ \text{cm}^3$ (~$25\,X_0$) has been constructed. This prototype employs 12 layers of BGO crystals alongside 2 layers of BSO crystals, the latter introduced as a cost-effective alternative and tested for the first time in this configuration. Beam tests conducted at the CERN low-energy T9 and H2 beamlines have been used to characterize its electromagnetic performance. This work provides critical benchmarks and insights for optimizing the crystal ECAL for the CEPC detector.

The future Circular Electron-Positron Collider (CEPC) is a large-scale experimental facility, which aims to accurately measure the Higgs boson, electroweak physics and the top quark. For the detector system in CEPC, a highly granular crystal electromagnetic calorimeter is proposed to achieve an EM energy resolution of less than 3%. It is a homogenous structure with long crystal scintillator bar as active material, and SiPM as the preferred photon sensor. There is a high requirement on the dynamic range of SiPM, since more thanhalf million photoelectronscan be measured for one channel. However, the calibration for SiPMs with such a large dynamic range is challenging. We have explored a series of methods to measure the nonlinear behavior of SiPMs with extremely high pixel densities—25 μm, 10 μm and 6 μm pixel size—under different conditions.

Firstly, using alaseras the light source and a PMT as an auxiliary calibration device, we measured the SiPM response when thepixels are not repeatedly fired. The results from different SiPMs show that under these conditions, the maximum number of photoelectrons measurable by the SiPM approaches its intrinsic pixel number, and nonlinearity becomes apparent when the signal exceeds 10% of the intrinsic pixel number.

Furthermore, we designed abeam experimentto investigate the nonlinearity of SiPMs when measuringintense scintillation light signals. In this case, the decay time of the scintillator is longer than the pixel recovery time of the SiPM, allowingSiPM pixels to be fired multiple times within a single event. We used tungsten plates as a pre-shower and increased the incident angle of the beam particles to enhance the energy absorbed by the crystal unit. Taking advantage of the dual-ended readout of the crystal, we added an optical filter to one end of the crystal to calibrate the actual absorbed energy. Finally, we observed energy absorption in the crystal exceeding 80 GeV as well as the nonlinear response of the SiPM.

A highly granular Silicon-Tungsten ECAL is a way to obtain a high precision for a broad range of conditions and final states. An advanced model has been developed for the Linear Colliders. We will present the progress toward its adaptation for circular colliders: ASICs, timing, power, cooling, optimisation and final state reconstruction.

Particle flow algorithm (PFA) and dual-readout are advanced calorimeter technologies proposed for precise jet energy measurements at future colliders. PFA requires highly granular calorimeters for efficient particle separation and optimal energy reconstruction depending on particle type. Dual-readout improves hadronic energy resolution by incorporating both scintillation and Cherenkov detectors, enabling event-by-event identification of the electromagnetic fraction within hadronic showers. Integrating these two technologies into a single calorimeter system poses significant challenges, as conventional dual-readout systems often rely on optical fibers, which are incompatible with the fine segmentation required by PFA. This study explores a novel approach to realize such a hybrid calorimeter by introducing tile-segmented Cherenkov layers into a calorimeter system used at Higgs factory. The expected improvement in energy resolution, achieved by combining these technologies, is evaluated through detailed simulation studies and will be presented in this conference.

Prospect for Measurement of CKM Angle $\gamma$ in $B_s^0 \rightarrow D_s^{\mp} K^{\pm}$ Decays at CEPC

We present a study projecting the sensitivity of measuring Cabibbo–Kobayashi–Maskawa (CKM) matrix elements at the CEPC, via direct observation of semi-leptonic WW decays at a center-of-mass energy (\sqrt{s} = 240\ \text{GeV}). This analysis focuses on determining six CKM matrix elements, including (|V_{cd}|), (|V_{cs}|), (|V_{cb}|), (|V_{ud}|), (|V_{us}|), and (|V_{ub}|), and further enables tests of CKM unitarity. By employing state-of-the-art jet flavor taggers, we assess the expected measurement precision. Our results indicate that the CEPC has the potential to significantly enhance the sensitivity to (|V_{cs}|) and (|V_{cb}|), while also providing constraints on the full set of six matrix elements and enabling rigorous tests of their unitarity. However, the achievable performance is found to strongly depend on the level of systematic uncertainties related to the parameters of flavor taggers.

The $b \to s\gamma$ is a critical FCNC process that could be used to probe CP violation (CPV) and New Physics (NP), especially in the context of future Z factory. The Circular Electron-Positron Collider (CEPC) offers inherent advantages for studying flavor physics, as it offers high statistic, clean collision environment, and superior detector performance. We quantify the anticipated precision of $B_s^0 \to \phi\gamma$ measurement at the CEPC Z pole modes, showing its signal strength could be determined to a relative accuracy of 0.16%, enhanced by roughly two orders of magnitudes compared to existing measurements. Additionally, we conduct a time dependent analysis of the $B_s^0 \to \phi\gamma$ decay, accounting for $B_s^0/\bar{B}_s^0$ mixing oscillations, and extract the mixing-induced and CP-violating parameters ${\mathcal{A}_{\phi\gamma}^\Delta}$, ${C_{\phi\gamma}}$ and ${S_{\phi\gamma}}$. The result are

$$ \begin{align*} {\mathcal{A}_{\phi\gamma}^\Delta} &= -0.67 \pm 0.0283(\text{stat}) \pm 0.0408(\text{syst}), \\ {C_{\phi\gamma}} &= 0.11 \pm 0.097(\text{stat}) \pm 0.0092(\text{syst}), \\ {S_{\phi\gamma}} &= 0.34 \pm 0.095(\text{stat}) \pm 0.0384(\text{syst}). \end{align*} $$

We also conduct a relative detector optimization study by establishing the correlation between the anticipated precision and the intrinsic resolution of the ECAL, as well as the performance of the PID system.

The discovery of a Higgs boson at the LHC consistent with the predictions of the Standard Model (SM) marked a major milestone in particle physics. In this context, the search for new Higgs-like bosons remains at the forefront of efforts to explore physics beyond the SM.

Based on several features observed in the data collected during Run 1 of the LHC, a simplified model was proposed in which a heavy scalar, $H$, decays into a combination of the SM Higgs boson ($h$) and a new Higgs-like scalar, $S$. One implication of this model is the appearance of excesses in lepton production when the decay $S \rightarrow WW$ dominates. These excesses, referred to as the multi-lepton anomalies at the LHC, were subsequently identified. They include events with two or more leptons, missing transverse energy, and ($b$)-jets in the final state. Based on the invariant mass of lepton pairs, the mass of the new scalar is predicted to be $m_S = 150 \pm 5\,\mathrm{GeV}$.

The analysis of $\gamma\gamma$, $Z\gamma$, and $WW$ sideband spectra in Run 2 data confirms the presence of a resonance at $m_S = 152 \pm 1\,\mathrm{GeV}$, with a global significance of $5.3\sigma$. This represents the strongest excess observed at the LHC to date that is consistent with a narrow resonance beyond the SM. These findings strongly motivate further investigation at future high-precision facilities such as the CEPC.

The statistical significance of the multilepton anomaly - the discrepancies in the channels with multiple leptons, missing energy, and (b-) jets in the final states with the SM prediction -indicates the production of a scalar with mass between 145 and 155 GeV that is beyond the standard model. The associated production of a narrow scalar resonance of mass around 150 GeV, with a significance of $5.3\sigma$ has been reported with the analysis of $\gamma\gamma$, $Z\gamma$, and $WW$ sideband spectra in Run 2 data. The requirement of the new scalar to decay dominantly to $WW$ final state by the multi-lepton anomalies and the absence of any excess in $ZZ$ final state significantly indicates the new scalar to be part of $Y = 0$ scalar-triplet. The model contains a $CP$-even neutral Higgs ($\Delta^0$), and two charged Higgs bosons ($\Delta^\pm$), which are quasi-degenerate in mass. Identifying the charged scalar at the LHC is difficult due to large SM backgrounds, production rates suppressed by small mixing angles
($\alpha$, $\beta$), and low detection efficiency for its moderately energetic leptons. This motivates dedicated searches at future $e^+e^-$-colliders, where the cleaner environment and well-defined initial state make $e^+ e^- \to \gamma^∗/Z \to \Delta^\pm \Delta^\mp$ the primary production channel. In this article, we focus on the possibility of finding the aforementioned predicted around 150 GeV BSM charged scalar at the future proposed $e^+ e^-$− collider. We emphasize on the pair production of the charged scalars, $e^+ e^- \to \Delta^\pm \Delta^\mp$ and scrutinize various signal regions depending on the decay products of $\Delta^\pm$.

In this talk, I will present new computational methods for Monte Carlo simulations based on machine learning techniques, as well as data analysis approaches utilizing quantum computing. These developments are aimed at supporting future high-energy collider programs, including the planned SPPC, as an extension of the CEPC framework.

The search for dark matter and other photon-portal long-lived particles (LLPs) at electron-positron colliders often relies on the mono-photon signature. However, this approach faces a critical challenge at future Higgs factories operating at the $Z$-pole. The search using prompt mono-photon pointing to the primary vertex is severely limited by irreducible background processes with identical signature, most notably from $e^+e^- \to \nu\bar{\nu}\gamma$. We propose a novel approach that overcomes this by searching for non-pointing photons from displaced decays of photon-portal LLPs within the barrel hadronic calorimeter. Selecting such non-pointing photons effectively rejects backgrounds with prompt mono-photon, providing exceptional sensitivity to LLPs with decay lengths between $\sim$1 and $10^6$ meters, far surpassing searches using prompt mono-photon signature.

Axion-like particles (ALPs) are well-motivated extensions of the Standard Model (SM) that appear in many new physics scenarios, with masses spanning a broad range. In this work, we systematically study the production and detection prospects of light ALPs at future lepton colliders, including electron-positron and multi-TeV muon colliders. At lepton colliders, light ALPs can be produced in association with a photon or a Z boson. For very light ALPs, the ALPs are typically long-lived and escape detection, leading to a mono-V (V=photon,Z) signature. In the long-lived limit, we find that the mono-photon channel at the Tera-Z stage of future electron-positron colliders provides the strongest constraints on ALP couplings to SM gauge bosons, thanks to the high luminosity, low background, and resonant enhancement from on-shell Z bosons. At higher energies, the mono-photon cross section becomes nearly energy-independent, and the sensitivity is governed by luminosity and background. At multi-TeV muon colliders, the mono-Z channel can yield complementary constraints. For heavier ALPs that decay promptly, mono-V signatures are no longer valid. In this case, ALPs can be probed via non-resonant vector boson scattering (VBS) processes, where the ALP is exchanged off-shell, leading to kinematic deviations from SM expectations. We analyze constraints from both light-by-light scattering and electroweak VBS, the latter only accessible at TeV-scale colliders. While generally weaker, these constraints are robust and model-independent. Our combined analysis shows that mono-V and non-resonant VBS channels provide powerful and complementary probes of ALP-gauge boson interactions.

Dark matter (DM) genesis via Ultraviolet (UV) freeze-in embeds the seed of
reheating temperature and dynamics in its relic density. Thus, the discovery of such a DM candidate can possibly open the window for post-inflationary dynamics. However, there are several challenges in this exercise, as freezing-in DM possesses feeble interaction with the visible sector and therefore very low production cross-section at the collider. We show that mono-photon (and dilepton) signal at the electron-positron collider, arising from DM effective operators connected to the SM field strength tensors, can still warrant a signal discovery. We study both the scalar
and fermionic DM production during reheating via UV freeze-in, when the inflaton oscillates at the bottom of a general monomial potential. Interestingly, we see that right DM abundance can be achieved only in the case of bosonic reheating scenario, satisfying bounds from big bang nucleosynthesis (BBN). This provides a unique correlation between the collider signal and the post-inflationary dynamics of the Universe within single-field inflationary models

The two popular frameworks for the effective field theory (EFT) describing physics beyond the standard model are the Standard Model EFT (SMEFT) and the Higgs EFT (HEFT). In this work, we present another framework, called broken phase effective field theory (bEFT), in which we deal directly with mass eigenstate fields after spontaneous symmetry breaking without employing nonlinear realization. We take the type-II seesaw model as an example to demonstrate our approach. We evaluate the Higgs pair production process through the vector boson fusion in the LHC and the Higgsstrahlung process in the linear collider. We find that our bEFT reproduces the type-II seesaw model more accurately than the SMEFT in the large parameter regions.

The Time Projection Chamber (TPC) can provide accurate measurement of the three-dimensional trajectory of charged particles and distinguish between low object mass particles and dE/dx, so it is widely used in high-energy particle physics experiments. For example, in the Ring Positron Collider (CEPC) experiment, TPC became the detector of choice for the main track detector. In order to achieve a 100-microns track resolution, TPC typically uses smaller readout pads, resulting in a dramatic increase in readout electronics density and channel count.
To meet the stringent demands on high rate and PID, pixel TPC is essential for CEPC tracking system. An interposer-based pixel readout for CEPC TPC has been proposed and a demonstrator of 500um x 500um pixels was developed, together with a multi-channel readout ASIC – TEPIX. TEPIX consists of 128 channels and each channel contains a CSA, a CDS, a 14-bit Wilkinson ADC and a 14-bit TOA. TEPIX works at a frame sampling mode and can provide information of charged particles, including time and energy. The power consumption of TEPIX is less than 0.5 mW/ch. The tested ENC is about 300e @0pF. This talk carries out the development and test results of interposer-based pixel readout to meet the high-density readout requirements of TPC detectors.

The Circular Electron Positron Collider (CEPC) is proposed for Higgs boson research, and will includes several detectors, such as the Electromagnetic Calorimeter (ECAL), Hadronic Calorimeter (HCAL), and Muon detector. Silicon photomultiplier (SiPM) is widely used in these detectors for light conversion. This paper presents a prototype design of SIPAC (SiPM readout ASIC for calorimeter).
Table 1 outlines the readout requirements of the ECAL and HCAL. Given the limitations of existing commercial chips and the CEPC detector’s requirement for a large-scale deployment of SiPM and their associated readout circuits, a dedicated SIPAC readout chip has been developed. With a maximum input charge of 3.84 nC, employing a CSA as the front-end amplifier would necessitate an impractically large input capacitor. To realize SiPM voltage adjustment, AC coupling is implemented between the preamplifier and the SiPM. Furthermore, given the slow response of the SiPM signal after passing through the crystal, SIPAC utilizes voltage amplifier as the front-end solution. Given the critical impact of the noise on time and energy resolution, the design of the shaper is critical. The energy path employs a slow shaper with two stages of low-pass filters, achieving an SNR of 8, while the timing path uses a fast shaper with a Bandpass filter, achieving an SNR of 12. Signals after shaping are sampled or compared, then quantized by the ADC or TDC and read out by the digital module. The four channels’ switched capacitor sampled signals are processed by a shared ADC and serializer for conversion and output, with each channel featuring a dedicated TDC. Figure 1 shows the overall architecture.
To address the gain variations between different SiPMs, an on-chip DAC is integrated into each channel for precise gain calibration of each SiPM. AC coupling is implemented for signal transmission, effectively isolating the adjustment effects of the DAC from the readout circuit. The signal after shaper is sampled by a switched-capacitor circuit and digitized by the SAR ADC for energy measurement. As shown in Figure 2, the post-simulation results indicate that within the input dynamic range of 1.28 pC to 3.84 nC, the nonlinearity errors are 0.4% for the high-gain path and 0.3% for the low-gain path. Furthermore, the SAR ADC achieves an ENOB of 10 bits.
For the time measurement path, the TDC employs a hybrid measurement structure combining coarse counting and fine counting. The coarse counting is derived from a counter, while the fine counting is determined by a delay line. The TDC is designed to measure the time of arrival (TOA). The digital codes generated by the TDC and ADC are encoded and serialized by the digital module for data transmission.
In summary, SIPAC, a dedicated SiPM readout ASIC for the CEPC detector, features a wide dynamic range (1.28 pC to 3.84 nC), supports a 500 kHz event rate, and achieves a 200 ps time resolution at 1.28 pC. The integrated TDC delivers 100 ps resolution with INL and DNL below 1 LSB, while the ADC achieves a 10-bit ENOB.
Currently, the chip is undergoing functional testing. The front-end circuit and TDC are working normally, and the ADC is under testing. It is expected that the accuracy of the TDC will reach 100ps, and the dynamic range of the front-end meets the design requirements. Detailed performance tests will be conducted after the functional tests are completed.

AC-coupled Low Gain Avalanche Detector (AC-LGAD) based microstrip, achieving 30 ps timing resolution with a 100 µm pitch, is proposed for the OTK in CEPC. The inherent capacitance of AC-LGAD presents significant challenges for power optimization. To match the strip pitch, a LGAD Timing Readout Integrated Chip (LATRIC) integrating 128 channels with a height of less than 100 µm per channel is proposed. A single-channel prototype, LATRIC0, is fabricated in a 55 nm process for functional verification and integrates a front-end amplifier, a time-to-digital converter (TDC) core, and two serializers for outputting encoded and raw data. For analysis and debug, both a 128-bit low-speed serializer and a 40-bit high-speed serializer are included to output raw and encoded data, respectively.
The TDC core is implemented with a compact layout height under 65 µm, including a timing controller, an event-driven ring oscillator with quantization logic, and an encoder. Upon an event trigger, the timing controller produces an enable signal to start the ring oscillator, along with separate latch signals for measuring the time of arrival (TOA) and time over threshold (TOT). A calibration (CAL) mechanism is incorporated via an additional clock cycle in the latch signal. The ring oscillator, which consists of 15 delay cells, supports simultaneous TOA, TOT, and CAL measurements.
Test results show that the TDC achieves an average bin-size of about 30 ps for both TOT and TOA. Both the tested integral and differential non-linearity are below 1 LSB.
Measurement results indicate that the average power consumption for the TDC measurement is below 0.12 mW at a 500 kHz event rate. The power consumption of the pre-amplifier and TDC block combined is less than 5.88 mW.
More detailed testing is in progress.

We give a report on new developments in the ReneSANCe Monte Carlo event generator and its application to the processes used for luminosity monitoring such as small/large angle Bhabha scattering e+e- -> e+e-, e+e- -> gamma gamma and e+e- -> mu+mu-. One-loop EW and higher order corrections, beam energy spread, polarization, and a number of background processes are taken into account.

Radiative corrections due to initial state radiation in electron-positron annihilation are calculated within the QED structure function approach. Results are shown in the next-to-leading logarithmic approximation up to O(alpha^4L^3) order, where L=ln(s/m^2_e) is the large logarithm. Dependence on factorization scale and scheme choices is analyzed. The results are relevant for future high-precision experiments at e+e− colliders.

High-Energy Physics (HEP) experiments increasingly rely on complex ASICs, driving a growing need for flexible, programmable architectures. We present a RISC-V–based System-on-Chip (SoC) that serves as a versatile control and configuration hub for CEPC ASICs. The SoC integrates tiny_riscv, a lightweight 32-bit processor with a 3-stage pipeline, capable of executing C programs to manage registers and implement communication protocols such as I²C and SPI via firmware. Its application will first be demonstrated in LATRIC, an ASIC for Low-Gain Avalanche Diode (LGAD) readout, with fabrication planned in a 55 nm CMOS process in October. This talk will present the SoC design, its implementation for CEPC ASICs, and prospects for future development and applications.

Parity-violating electron scattering is a powerful tool for precision tests of the Standard Model, enabling highly accurate measurements of the weak mixing angle. The upcoming MOLLER experiment at the Jefferson Lab will measure the electron's weak charge with 0.1% precision, providing sensitivity to new physics at the O(10) TeV scale. This talk will present recent theoretical work aimed at reducing the associated theoretical uncertainties to a level that matches or surpasses this experimental target.

The breaking of the Lam-Tung relation in the Drell-Yan process at the LHC exhibits a long-standing tension with the Standard Model (SM) prediction at $\mathcal{O}(\alpha_s^3)$ accuracy. This tension could be explained by weak dipole interactions of leptons and quarks, associated with the $Z$-boson within the framework of the Standard Model Effective Field Theory (SMEFT). In this paper, we propose to cross-check these weak dipole interactions by measuring the violation effects of the Lam-Tung relation at future lepton colliders through the processes $e^+e^- \to Z\gamma \to \ell\bar{\ell}\gamma$ and $e^+e^- \to Z\gamma \to q\bar{q}\gamma$. By considering different decay modes of the $Z$-boson, these channels exhibit distinct sensitivities to various dipole operators, providing a way to disentangle their individual effects. Additionally, the high flavor-tagging efficiencies at lepton colliders could provide strong constraints on the dipole interactions of heavy quarks, such as $b$ and $c$ quarks, which are challenging to probe in the Drell-Yan process at the LHC due to the suppression of parton distribution functions.

CEPC ref-Detector TDR is finished and submmitted for publish.CEPC plans to run at a non-empty bunch crossing rate of 1.34–40 MHz.Background data throughput will be from 100 GB/s (Higgs mode) to 1 TB/s (Z-boson pole). Simulations show the trigger system can reduce rates to the range of few to tens of GB/s efficiently and event rate to 30 kHz (Higgs) and 120 kHz (low lumi-Z). The L1 trigger employs a three-stage hardware system: the first stage generates module-level triggers from backend electronics; subsequent stages integrate sub-detector triggers and execute global selection.The L1 signals are sent to Backend Electronic of each detector for data readout via the TCDS(Trigger and Clock Distribution System).This report will show more detials of L1 trigger system design and progress on the R&D.

The Circular Electron–Positron Collider (CEPC) enables high-precision electroweak studies at the pole. We present a simulation-based study of the forward–backward charge asymmetry ($A^\mu_{FB}$) in $e^+e^-\to\mu^+\mu^-$ events using the TDR reference detector. After optimized event selection, the signal efficiency reaches about 90% with negligible background contamination. Signal and background samples are generated including $\gamma^*/Z$ interference and QED radiation, and the simulated asymmetry agrees with the LEP result. Systematic effects from muon identification, background, detector resolution, beam energy spread and beam energy calibration are evaluated. Assuming one month of low-luminosity $Z$-pole running in the first CEPC $ZH$ operation year, corresponding to $4\times10^{10}$ $Z$ bosons, the expected precision on $A^\mu_{FB}$ is $\pm3.1\times10^{-5}$ (stat.) and $\pm2.8\times10^{-5}$ (syst.), improving the LEP accuracy by two orders of magnitude.

Sphaleron production in the Standard Model at high-energy particle collisions remains experimentally unobserved, with theoretical predictions hindered by its nonperturbative real-time nature. In this work, we investigate a quantum simulation approach to this challenge. Taking the $1+1$D $O(3)$ model as a protocol towards studying dynamics of sphaleron in the electroweak theory, we identify the sphaleron configuration and establish lattice parameters that reproduce continuum sphaleron energies with controlled precision. We then develop quantum algorithms to simulate sphaleron evolutions where quantum effects can be included. This work lays the ground to establish quantum simulations for studying the interaction between classical topological objects and particles in the quantum field theory that are usually inaccessible to classical methods and computations.

The High-Luminosity LHC upgrade will present unprecedented challenges, including intense radiation and up to 200 simultaneous proton collisions. To cope with this, the CMS experiment will deploy a new MIP Timing Detector (MTD) to precisely timestamp MIP particles. This contribution focuses on the MTD's Barrel Timing Layer (BTL), which is now transitioning from a successfully validated design to full-scale construction, highlighting its innovative crystal-based technology and assembly progress.

In high-energy physics experiments, online data processing plays an important role. Positioned between the readout of the front-end electronics and the disk, it reduces the vast raw data to a storable size through fast reconstruction and event filtering. Next-generation experiments such as the Circular Electron–Positron Collider (CEPC) impose even more stringent requirements on online data processing. Heterogeneous computing—coordinating different processors like CPUs and GPUs—can boost online data-processing capability and meet these higher demands. This report presents and describes a heterogeneous online data-processing framework designed for CEPC, aiming to improve online computing power through heterogeneous computing resources and thereby provide solid online data-processing support for the CEPC.

Meeting the data processing requirements of next-generation high-energy physics collider experiments, such as the Circular Electron-Positron Collider (CEPC), poses a significant challenge for data acquisition systems, particularly in the real-time triggering, online selection, and flexible processing of enormous event rates. Conventional online computing architectures based on static pipelines exhibit limitations in flexibility, scalability, and the rapid deployment of offline algorithms.

This report presents a novel data acquisition and online computing architecture centered around a distributed in-memory cache pool. By establishing a globally shared cache pool, this architecture decouples front-end electronics readout from back-end high-performance online processing modules, enabling asynchronous communication. A core scheduling system manages the full lifecycle of online processing algorithms and enables dynamic resource allocation and isolation. This design ensures system real-time performance and stability while significantly enhancing flexibility for algorithm updates and module integration, effectively supporting the direct migration and application of complex offline algorithms in the online environment.

The core components of this architecture have been fully developed. Notably, this design has been successfully deployed and validated within the Large High Altitude Air Shower Observatory (LHAASO). Field tests confirm that the system fulfills real-time processing demands under extreme data throughput, demonstrating the architecture's effectiveness and engineering feasibility in addressing the future data challenges of large-scale facilities like CEPC.

With the public release of parton level event generator NNLOJET, antenna subtraction method has been playing an important role in the precision predictions of high energy colliders. The talk includes the latest development of the antenna subtraction method and its application to di-jet productions on electron-positron colliders with up to N3LO QCD corrections.

The +− annihilation of unpolarized beams is free from initial hadron states or initial anisotropy around the azimuthal angle, hence ideal for studying the correlations of dynamical origin via final state jets. We investigate the planar properties of the multi-jet events employing the relevant event-shape observables at next-to-next-to-leading order (O(3)) in perturbative QCD; particularly, the azimuthal angle correlations on the long pseudo-rapidity (polar angle) range (Ridge correlation) between the inclusive jet momenta are calculated. We illustrate the significant planar properties and the strong correlations which are natural results of the energy-momentum conservation of the perturbative QCD radiation dynamics. Our study provides benchmarks of hard strong interaction background for the investigations on the collective and/or thermal effects via the Ridge-like correlation observables for complex scattering processes.

Single-inclusive hadron production in electron-positron annihilation (SIA) represents the cleanest process for investigating the dynamics of parton hadronization, as encapsulated in parton fragmentation functions. In this talk, I will present the analytical computation of QCD corrections to the coefficient functions for SIA at next-to-next-to-next-to-leading order (N3LO) accuracy based on arXiv:2503.20441.