Reconstruction of leptonic physic objects at future e+e- Higgs factory
Reconstruction of leptonic physic objects at future e+e- Higgs factory
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发表时间：
2018-02
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通讯作者：
D. Yu
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作者：
D. Yu
基本粒子相互作用的标准模型是过去四十年粒子物理学实验和理论活动的杰出成就。自2012年大型强子对撞机（LHC）实验发现希格斯玻色子以来，精确测量已成为高能物理实验中的难题。许多希格斯总宽度测量精度更高的正负电子希格斯工厂被提出，包括国际直线对撞机（ILC）和圆形正负电子对撞机（CEPC）。未来将要开展的希格斯物理计划$e^{+}e^{-}$对撞机已经过评估，许多耦合的精度程度估计达到百分之或亚百分之的水平。为了达到这种精度，粒子流算法（PFA）已成为高能前沿探测器设计的范例。关键思想是在最合适的子探测器中重建每个最终状态粒子，并重建最终状态粒子之上的所有物理对象。 PFA导向的探测器在重建轻子、射流和缺失能量等物理对象方面具有很高的效率。轻子识别对于物理程序，特别是希格斯玻色子的精确测量至关重要。本论文开发了一种基于PFA的轻子识别（高粒度热量计轻子识别），用于使用高粒度热量计的探测器。利用CEPC的概念探测器几何结构和能量大于2 GeV的单带电粒子样品，LICH识别电子/μ子的效率高于99.5%，并将强子对μ子/电子的误识别率控制在优于1%/0.5%。将量热计粒度降低1-2个数量级，对于E > 2 GeV的粒子轻子识别性能稳定。应用于完全模拟的eeH/$mumu$ H事件，轻子识别性能与单粒子情况一致：识别事件中所有高能轻子的效率为95.5-98.5%。除了e和$mu$之外，$tau$s是非常有趣的物理对象，因为它与希格斯玻色子的汤川耦合相对较大。由于其丰富的衰变产物，可以精确测量 Z 工厂的希格斯 CP 和 EW 参数等特性。高能对撞机中的 $tau$ 衰变是紧密准直且低多重性的，这为探测提供了极好的特征。本文在考虑SM背景的情况下，在不同的Z衰减模式下对H$rightarrow$$tautau$通道进行分析，最终的综合准确率预计为1.3%。
The Standard Model of elementary particle interactions is the outstanding achievement of the past forty years of experimental and theoretical activity in particle physics. Since the discovery of the Higgs boson in 2012 by the experiments at the Large Hadron Collider (LHC), the precise measurement has become the issue in high energy physics experiments.Many electron-positron Higgs factories with better accuracy on the Higgs total width measurements have been proposed, including the International Linear Collider (ILC) and the Circular Electron Positron Collider (CEPC).The Higgs physics program to be carried out at the future $e^{+}e^{-}$ colliders have been be evaluated and its extent of the precision of many of couplings are estimated to percent or sub-percent levels.In order to achieve this precision, the Particle Flow Algorithm (PFA) has become the paradigm of detector design for the high energy frontier. The key idea is to reconstruct every final state particle in the most suited sub-detectors, and reconstruct all the physics objects on top of the final state particles. The PFA oriented detectors have high efficiency in reconstructing physics objects such as leptons, jets, and missing energy.The lepton identification is essential for the physics programs, especially for the precise measurement of the Higgs boson.In this thesis, a PFA based lepton identification (Lepton Identification for Calorimeter with High granularity) has been developed for detectors using high granularity calorimeters. Using the conceptual detector geometry for the CEPC and single charged particle samples with energy larger than 2 GeV, LICH identifies electrons/muons with efficiencies higher than 99.5% and controls the mis-identification rate of hadron to muons/electrons to better than 1%/0.5%. Reducing the calorimeter granularity by 1-2 orders of magnitude, the lepton identification performance is stable for particles with E > 2 GeV. Applied to fully simulated eeH/$mumu$ H events, the lepton identification performance is consistent with the single particle case: the efficiency of identifying all the high energy leptons in an event, is 95.5-98.5%.Except for e and $mu$, $tau$s are extremely intriguing physics objects as its Yukawa coupling to the Higgs boson is relatively large. Due to its rich decay products, properties such as the Higgs CP and EW parameters at the Z-factory can be precisely measured. The $tau$ decay in high energy colliders is tightly collimated and low multiplicity, which provide excellent signatures to probe. In this thesis, the H$rightarrow$ $tautau$ channels are analyzed in different Z decay modes with SM background taken into account and the combine final accuracy is expected to be 1.3%.