Improved measurement of the neutral pion decay into electron, positron and photon, and optimisation of the kaon tagger using hydrogen in NA62.

我的研究将作为CERN NA 62实验的一部分进行。NA 62是一个固定靶实验，旨在测量K介子和π介子的罕见衰变。其主要目的是获得Vtd CKM参数的10%测量值。需要大量的探测器来提供必要的粒子识别、高分辨率计时、运动学排斥和光子的密封否决。NA 62实验使用切伦科夫探测器（称为KTAG），通过探测发射的切伦科夫光来识别K介子和π介子。KTAG使用CEDAR容器，该容器充满氮气并包含几个光学仪器，这些光学仪器被微调，使得粒子发射的切伦科夫光被聚焦到CEDAR上游的光电倍增管组。在我研究的初始阶段，我将研究是否可以调整当前的光学器件，以便使用氢气而不是氮气。这将具有减少通过检测器行进的K介子的多重散射的优点。我的研究项目的主要部分将致力于改进单Dalitz衰变分支分数。单Dalitz衰变的电流分支分数测量值为（1.174 +/- 0.035）%。我的项目的目标是将这一指标从3%提高到1%。

My research will be carried out as part of the NA62 experiment at CERN. NA62 is a fixed target experiment and is designed to measure rare decays of kaons and pions. It's main aim is to obtain a 10% measurement of the Vtd CKM parameter. A large number of detectors are required to provide the necessary particle identification, high-resolution timing, kinematic rejection and hermetic vetoing of photons. The NA62 experiment uses a Cherenkov detector (known as KTAG) which identifies kaons and pions by detecting the Cherenkov light emitted. The KTAG uses a CEDAR vessel which is filled with nitrogen gas and contains several optical instruments which are finely tuned so that the Cherenkov light emitted by the particles is focused to sets of photomultiplier tubes upstream of the CEDAR. For the initial stage of my research, I will be investigating whether the current optics can be adapted so that instead of using nitrogen gas, hydrogen could be used. This would have the advantage of reducing the multiple scattering of the kaons travelling through the detector. The main part of my research project will be working on an improvement in the single Dalitz decay branching fraction. The current branching fraction measurement of the single Dalitz decay is (1.174 +/- 0.035)%. The aim of my project will be to improve this from a 3% to a 1% measurement.