Dark Matter Searches with LUX-ZEPLIN

LZ直接暗物质探测器利用电离释放的电子产生的闪烁光子和电致发光光子来检测粒子相互作用。对于2022年的第一个科学结果，LZ依靠一系列快速的模拟，通过与校准数据相适应的参数化响应函数来建立用于设置初始限制的信号和背景模型。然而，这样的模拟不能处理需要理解的分布的尾部，以完全计划的1000天暴露。为了最大限度地提高LZ的灵敏度，需要进行全链模拟来跟踪发射的光和电荷。LZ具有这样的模拟，该模拟在第三个模拟数据挑战的探测器构建之前完成，并且使用该模拟以使得可以创建模拟波形事件以通过整个重建和分析链。牛津大学在这一模拟开发中发挥了主导作用。尼古拉斯·菲尔德豪斯最初的工作将集中在完整的模拟链上，使波形看起来与LZ探测器中记录的波形完全相同。与以前的LUX探测器相比，需要改进的电场模拟代码来建立来自第一原理的电离信号，这些信号看起来像LZ一样参差不齐。一旦有了改进的全链模拟，并根据扩展的校准数据集进行了验证，它就可以用于改进事件处理和测试分析。然后，Nicholas的项目可以通过两种方式探索全模拟链的使用。第一个将是通过使用脉冲子结构来改进我们对整数个提取的电子的电离信号的重建。这种改进的重建可以帮助降低能量阈值，减少测量能量的不确定性，并有望增加对电子反冲背景的辨别。第二项任务将是针对偶然的符合事件开发新的切割，在意外符合事件中，电离信号与电极或捕获在液体表面的电子的发射有关。一个大型的模拟数据集将在开发这些针对罕见事件的削减方面发挥关键作用，否则在我们的第一次科学运行中很难消除这些事件。最后，尼古拉斯将拥有从事电极电子发射研发研究的硬件经验，作为下一代液体氙气TPC暗物质实验的设计。这些硬件研究将受益于为LZ所做的分析和仿真工作，并有望为LZ分析提供有用的反馈。

The LZ direct dark matter detector utilizes scintillation photons and electroluminescence photons created by electrons released by ionization to detect particle interactions. For the first science result in 2022, LZ relied upon a fast chain of simulations with parametrised response functions fit to calibration data to build the signal and background models used in setting initial limits. However, such simulations cannot handle the tail of distributions needed to be understood for the full planned exposure of 1000 days. A full chain simulation that tracks the emitted light and charge will be necessary to maximize LZ's sensitivity. LZ has such a simulation, completed prior to detector construction for the third mock data challenge, and used such that mock waveform events could be created to go through the entire reconstruction and analysis chain. Oxford played a leading role in this simulation development. Nicholas Fieldhouse's initial work will focus on the full simulation chain making waveforms that look precisely like waveforms recorded in the LZ detector. Improved simulations from electric field modelling code will be required to build ionization signals from first principles that appear as jagged as LZs do, in contrast to the previous LUX detector. Once an improved full chain simulation is in hand, and verified against extended calibration data sets, it can then be used for improving event processing and testing analyses.Nicholas' projects can then explore the use of the full simulation chain in two ways. The first will be improving our ionization signal reconstruction of integer numbers of extracted electrons by using the pulse substructure. This improved reconstruction can help lower the energy threshold, reduce the uncertainty on the measured energy, and hopefully increase discrimination against electronic recoil backgrounds. The second task would be developing new cuts against accidental coincidence events where the ionization signal is linked to the emission of electrons from the electrodes or from electrons trapped on the liquid surface. A large simulation dataset will play a key role in developing these cuts against rare events that have otherwise proved difficult to eliminate in our first science run.Finally, Nicholas will have hardware experience working on R&D studies of electron emission from electrodes as designs for the next generation liquid xenon TPC dark matter experiment. These hardware studies will benefit from the analysis and simulation work done for LZ, and can hopefully provide useful feedback to the LZ analysis too.