International Journal of Modern Physics A

The Circular Electron Positron Collider (CEPC) is a proposed Higgs factory with center-of-mass energy of 240GeV to measure the properties of Higgs boson and test the standard model accurately. Synchrotron radiation (SR) generated from the final doublet (FD) magnets in the interaction region of CEPC double ring scheme is one of the typical issues. SR photons can contribute to the heat load of the beam pipe and cause photon background to the experiments. Furthermore, the radiation dose can damage detector components. In this paper, SR generated from FD magnets is analyzed when beam is with tails and offset. SR from the dipole leakage field of the FD superconducting magnets is also analyzed and the physics limit is given to protect the detector.

The Circular Electron Positron Collider (CEPC) is a proposed Higgs factory with center-of-mass energy of 240GeV to measure the properties of Higgs boson and test the standard model accurately. Beam loss background in detectors is an important topic at CEPC. During manufacture and installation, magnets are not perfect and with many kinds of errors. Beam–beam interaction in high-energy electron positron collider is the action of external field force, which changes the momentum of each beam bunch. Thus, beam loss background can be affected by the magnet errors and beam–beam effect. In this paper, the beam loss background with magnet errors and beam–beam effect is simulated in CEPC.

The CEPC Plasma Injector is designed as the beam energy multiplier for avoiding the dipole magnet issue of the Circular Electron Positron Collider (CEPC) booster. Besides the final energy, other requirements including the energy stability, bunch charge and energy spread all make the injector design very challenging. With respect to the electron acceleration, a high transformer ratio plasma wakefield acceleration stage is necessary if we constrain the beam energy at the end of the linac and the plasma injector are 10GeV and 45.5GeV, respectively. In this work, we use the particle-in-cell code QuickPIC to design the electron acceleration stage. Based on the current conceptual design, a comprehensive analysis of single-parameter tolerance is performed. Through the tolerance studies, we obtain some useful guidance for the further optimization of the injector.

After Circular Electron Positron Collider (CEPC) Conceptual Design Report (CDR), in Technical Design Report (TDR) phase, CEPC accelerator optimization design continues not only with higher luminosity at Higgs energy, but also at different energies of tt-bar, W and Z-pole. In this paper, we give a status review of CEPC optimization design, and TDR hardware R&D progresses.

This paper describes the imperfection and correction for the CEPC CDR lattice in the Higgs mode. The correction scheme contains closed orbit correction, optics correction and the betatron coupling correction. Two error cases with 1000 lattice seeds are studied and statistically analyzed. The dynamic aperture after correction is also studied to compare the on-axis beam injection requirement.

This paper describes the injection philosophy and the design of timing and filling scheme for the high luminosity Circular Electron and Positron Collider (CEPC) scheme under different energy modes. It is found that the RF frequency choice in Conceptual Design Report (CDR) cannot meet the injection requirements for the bunch number at the Z pole. A modified scheme was proposed to support the design luminosity, which basically meets our current design requirements and retains more flexibility for a future high-luminosity upgrade.

In this talk I give a snapshot of the ongoing discussion on new physics searches at future colliders. I discuss the unique opportunities of a high energy lepton collider operating at multi-TeV center-of-mass energy and in particular its peculiar capability to carry out at the same time "intensity'' searches with the copious production of Standard Model states as well as directly producing heavy new physics states or probing still heavier new physics via indirect effects.

The electroweak phase transition can be made first order by extending the Standard Model (SM) Higgs sector with extra scalars. Here, we focus on the strong first-order electroweak phase transition (SFOEWPT) in the Type-II two Higgs doublet models (2HDMs). Through a parameter space scan, we find that SFOEWPT suggests upper limits on the masses of the heavy Higgs $m_{A∕H∕H^{\pm }}$, which is less than 1TeV. High-temperature expansion and Higgs vacuum uplifting are used for analytical understanding of our results. We find that sizeable loop corrections require $m_A\approx m_{H^{\pm }}>m_H$ to meet the SFOEWPT condition in the Type-II 2HDM. We also study the possibility of probing SFOEWPT at the one-loop level from Higgs and $Z$-pole precision measurements at future Higgs and $Z$ factories.

The Circular Electron–Positron Collider (CEPC) has been proposed as a Higgs and high luminosity $Z$ factory for the last few years in China. To achieve the high precision physical goals at CEPC, the high resolution ($<100\mu \mathrm{\text{m}}$) tracker for the particle track reconstruction and particle identification are demanded. Time Projection Chamber (TPC) is one of the main concept proposal of the central tracker detector in very large 3D volume, it has an excellent performance on the moment measurement, $dE∕dx$ measurement and the spatial resolution. The simulation results were given when the TPC detector will operate at the high luminosity $Z$ pole at the future $e^{+}{e}^{-}$ circular collider. The pixelated readout TPC is a potential option to replace the traditional pad readout with the low gain, low occupancy, and outstanding pattern recognition. In the last several years, a TPC module, the readout electronics and prototype for the specific requirements have been developed at the Institute of High Energy Physics (IHEP). TPC module will could suppress the ions in chamber continuously running in the different gains (2000–5000) under T2K mixture gases. A TPC prototype with $200\mathrm{\text{mm}}\times 200\mathrm{\text{mm}}$ active area G detector module integrated the narrow 266nm UV laser tracks along the drift length of 500mm, and the low power consumption ($<5\mathrm{\text{mW}}∕\mathrm{\text{ch}}$) Application-Specific Integrated Circuits (ASIC) chip including analog to digital converter (ADC) function has been developed too. The update results of the spatial resolution has been obtained after some experimental studies have been done by the TPC prototype.

The persistent $3-4\sigma$ discrepancy between the experimental result from Brookhaven National Laboratory (BNL) for the anomalous magnetic moment of the muon, ${(g-2)}_{\mu }$, and its Standard Model (SM) prediction, was confirmed recently by the “MUON G-2” result from Fermilab. The combination of the two measurements yields a deviation of $4.2\sigma$ from the SM value. Here, we review an analysis of the parameter space of the electroweak (EW) sector of the Minimal Supersymmetric Standard Model (MSSM), which can provide a suitable explanation of the anomaly while being in full agreement with other latest experimental data like the direct searches for EW particles at the LHC and dark matter (DM) relic density and direct detection constraints. Taking the lightest supersymmetric particle (LSP) (the lightest neutralino in our case) to be the DM candidate, we discuss the case of a mixed bino/wino LSP, which can account for the full DM relic density of the universe and that of wino and higgsino DM, where we take the relic density only as an upper bound. We observe that an upper limit of $\sim 600\mathrm{\text{GeV}}$ can be obtained for the LSP and next-to (N)LSP masses establishing clear search targets for the future HL-LHC EW searches, but in particular for future high-energy $e^{+}{e}^{-}$ colliders such as the ILC or CLIC.