分类： 物理学 >> 核物理学 提交时间： 2024-06-02
摘要： The Circular Electron Positron Collider (CEPC) is designed to precisely measure the properties of the Higgs boson, study electroweak interactions at the Z-boson peak, and search for new physics beyond the Standard Model. As a component of the 4th Conceptual CEPC detector, the drift chamber facilitates the measurement of charged particles. This study implemented a Geant4-based simulation and track reconstruction for the drift chamber. For the simulation, detector construction and response were implemented and added to the CEPC simulation chain. The development of track reconstruction involved track finding using the Combinatorial Kalman Filter method and track fitting using the tool of GenFit. Using the simulated data, the tracking performance was studied. The results showed that both the reconstruction resolution and tracking efficiency satisfied the requirements of the CEPC experiment.
分类： 核科学技术 >> 辐射物理与技术 提交时间： 2024-04-30
摘要： Transverse mode-coupling instability (TMCI) is a dangerous transverse single-bunch instability that can leadto severe particle loss. The mechanism of TMCI can be explained by the coupling of transverse coherentoscillation modes owing to the transverse short-range wakefield (i.e., the transverse broadband impedance).Recent studies on future circular colliders, e.g., FCC-ee, showed that the threshold of TMCI decreased significantlywhen longitudinal and transverse impedances were included. We performed computations for a circularelectron-positron collider (CEPC) and observed a similar phenomenon. Systematic studies on the influence oflongitudinal impedance on the TMCI threshold were conducted. We concluded that the imaginary part of thelongitudinal impedance, which caused a reduction in the incoherent synchrotron tune, was the primary reasonfor the reduction in the TMCI threshold. Additionally, the real part of the longitudinal impedance assists inincreasing the TMCI threshold.
分类： 核科学技术 >> 核科学与技术 提交时间： 2023-08-27
摘要： As a unique probe, precision measurement of textit{pp} solar neutrinos is important for studying the Sun's energy mechanism, monitoring thermodynamic equilibrium, and studying neutrino oscillation in the vacuum-dominated region. For a large-scale liquid scintillator detector, one bottleneck for textit{pp} solar neutrino detection comes from pile-up events of intrinsic $^{14}$C decays. This paper presents a few approaches to discriminate textit{pp} solar neutrinos and $^{14}$C pile-up events by considering the difference in their time and spatial distributions. In this work, a Geant4-based Monte Carlo simulation is constructed. Then multivariate analysis and deep learning technology were adopted respectively to investigate the capability of $^{14}$C pile-up reduction. As a result, the BDTG model and VGG network showed good performance in discriminating textit{pp} solar neutrinos and $^{14}$C double pile-up events. hl{At the $^{14}$C concentration assumption $5 times10^{-18} g/g$,} their signal significance can achieve 10.3 and 15.6 using only one day of statistics. In this case, the signal efficiency is 51.1 % for discrimination using the BDTG model when rejecting 99.18 % $^{14}$C double pile-up events, and the signal efficiency is 42.7 % for the case using the VGG network when rejecting 99.81 % $^{14}$C double pile-up events.
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