Jets at low $Q^2$ at HERA and radiation damage studies for silicon sensors for the XFEL
Jets at low $Q^2$ at HERA and radiation damage studies for silicon sensors for the XFEL
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HERA 的低 $Q^2$ 喷气机以及 XFEL 硅传感器的辐射损伤研究
DOI：
10.1142/9789814374125_0017
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发表时间：
2011
影响因子：
5.4
通讯作者：
H. Perrey
中科院分区：
文献类型：
--
作者：
H. Perrey
在本论文的第一部分中，测量了在 10 < Q2 < 100 GeV2 范围内的光子虚拟度下的包容性射流、包容性双射流和包容性三射流产生的射流横截面。分析的数据是用 Zeus 探测器在 2004 年至 2007 年记录的，对应的积分光度为 296 pb−1。中性电流深度非弹性散射中的事件被选择在上述 Q2 区域中，非弹性为 0.2 < y < 0.6。这些喷流是在布赖特框架中重建的，虚拟玻色子和质子在其中正面碰撞。要求喷流在布赖特坐标系中携带 pT,B > 8 GeV 的横向动量，并在实验室坐标系中具有 -1 < ηlab < 2.5 范围内的赝快度。对于双射流和三射流样品，对 Mjj > 20 GeV 的不变双射流质量提出了额外要求，以避免固定阶次计算对红外发散敏感的相空间区域。所提出的分析是首次在如此低的 Q2 值下进行射流分析，以利用完整的 Hera-II Zeus 数据集，因此是在比以前的出版物更高的光度下进行的。总体而言，次先导阶 (NLO) 计算正确预测了所有研究量和相空间大多数研究区域的不确定性内的测量横截面，但在包容性射流生产中靠近质子束方向（“前向”区域）的赝快速区域中，预测值大大低于数据。 NLO 预测的不确定性主要由与重正化尺度选择相关的不确定性决定，通常大于实验不确定性，而实验不确定性在很大程度上由射流能量尺度的不确定性决定。巨大的理论不确定性表明需要进行包括高阶在内的计算。这种 NNLO 计算将允许充分利用 QCD PDF 拟合和拟合中低 Q2 射流数据的敏感性来提取 αs 值。在本论文的第二部分，研究了剂量高达 1 GGy 的 12 keV X 射线对硅传感器的辐射损伤。对于这项研究，Desy 的 Hasylab 建立了辐照设施。测试结构（栅控二极管）已经过辐照，并且使用电流与电压 (I/V)、电容与电压 (C/V) 和热去极化弛豫电流 (TDRC) 测量研究了高辐照下 Si-SiO2 界面的特性。除了作为剂量函数的界面电流和平带电压的强烈增加和随后的减少之外，还发现了强烈的磁滞效应。数据可以通过包含界面陷阱和固定氧化物电荷的模型来定性描述。模型预测与 C/V 和 TDRC 测量结合使用，分别确定 Si-SiO2 界面处存在的不同类型的陷阱以及 SiO2 中的电荷。本研究中提取的参数将被实施到模拟中，目的是重现测量结果，然后将它们用于 Agipd 项目的辐射硬传感器的设计。
In the first part this thesis, jet cross-sections were measured for inclusive jet, inclusive dijet, and inclusive trijet production at photon virtualities in the range of 10 < Q2 < 100 GeV2. The data analyzed were recorded with the Zeus detector in the years 2004 – 2007 corresponding to an integrated luminosity of 296 pb−1. Events in neutral current deep inelastic scattering were selected in the above stated Q2 region for an inelasticity of 0.2 < y < 0.6. The jets were reconstructed in the Breit frame, where the virtual boson and the proton collide head on. The jets were required to carry a transverse momentum in the Breit frame of pT,B > 8 GeV and to have a pseudorapidity in the laboratory frame in the range of −1 < ηlab < 2.5. For the dijet and trijet samples, an additional requirement was imposed on the invariant dijet mass of Mjj > 20 GeV to avoid phase space regions where the fixed order calculations are sensitive to infrared divergences. The presented analysis is the first jet analysis at such low values of Q2 to exploit the full Hera-II Zeus data set, and as such is performed at significant higher luminosities than previous publications. Overall, the next-to-leading order (NLO) calculations correctly predict the measured cross-sections within the uncertainties in all studied quantities and over most of the investigated regions of phase space, except in the pseudorapidity region close to the proton beam direction (“forward” region) in inclusive jet production where the prediction is considerably below the data. The uncertainty of the NLO prediction, dominated by the uncertainty associated with the choice of the renormalization scale, is typically larger than the experimental uncertainty, which is for the most part dominated by the uncertainty of the jet energy scale. The large theoretical uncertainties indicate the need for calculations including higherorders. Such NNLO calculations will allow to fully exploit the sensitivity of the low Q2 jet data in QCD PDF fits and in fits to extract values of αs. In the second part of this thesis, a study of radiation damage of silicon sensors by 12 keV X-rays for doses up to 1 GGy is presented. For this study, an irradiation facility has been set up at Hasylab at Desy. Test structures (gate-controlled diodes) have been irradiated and the properties of the Si-SiO2 interface under high irradiation have been studied using current versus voltage (I/V), capacitance versus voltage (C/V), and thermally depolarization relaxation current (TDRC) measurements. In addition to a strong increase and subsequent decrease of the interface current and the flat-band voltage as function of dose, strong hysteresis effects have been found. The data can be qualitatively described by a model which includes interface traps and fixed oxide charges. The model predictions were used in combination with in C/V and TDRC measurements to separately determine the different types of traps present at the Si-SiO2 interface and the charges in the SiO2. The parameters extracted in this studies are to be implemented into simulations with the goal of reproducing the measurements and later use them for the design of radiation hard sensors for the Agipd project.