A Vertex Fit for Low Momentum Particles in a Solenoidal Magnetic Field with Multiple Scattering
A Vertex Fit for Low Momentum Particles in a Solenoidal Magnetic Field with Multiple Scattering
复制标题
具有多重散射的螺线管磁场中低动量粒子的顶点拟合
DOI：
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发表时间：
2013
期刊：
影响因子：
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通讯作者：
N. Berger
中科院分区：
文献类型：
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作者：
S. Schenk;N. Berger
由于已经观察到中微子振荡，很明显，在中性轻子区域中违反了原始标准模型预测的轻子风味守恒。许多新的物理模型也包括带电区域中的轻子味道破坏，但仍然缺少实验发现。 Mu3e 实验将寻找违反 μ→ eee 的轻子味道，该味道在 SM 中受到严重抑制。它采用了一种新颖的设计，涉及螺线管磁场中的四个薄圆柱形像素探测器层。由于电子动量较低，第一探测器层中的多重散射非常显着。在 Mu3e 实验的背景下，我研究了一种新的线性化三维顶点拟合，将多重散射视为唯一的不确定性来源。在模拟的基础上，从重建效率、顶点位置分辨率、粒子动量和算法配置依赖性、背景抑制和不变质量分辨率等方面评估其性能。顶点重建的新方法有效并实现了 200μm 的顶点位置分辨率。此外，通过公共顶点的重建可以极大地抑制偶然背景。结果表明，线性化顶点拟合对于实现所提出的 1× 10−16 分支比灵敏度至关重要。
Since neutrino oscillations have been observed, it is evident that lepton flavour conservation as predicted by the original Standard Model is violated in the neutral lepton sector. Many new physics models include lepton flavour violation in the charged sector as well, but an experimental discovery is still missing. The Mu3e experiment will search for the lepton flavour violating muon decay μ→ eee, which is heavily suppressed in the SM. It uses a novel design involving four thin cylindrical layers of pixel detectors in a solenoidal magnetic field. Due to low momentum electrons, multiple scattering in the first detector layer is significant. In the context of the Mu3e experiment, I investigated a new linearised threedimensional vertex fit, treating multiple scattering as the only source of uncertainty. Its performance is evaluated in terms of reconstruction efficiency, vertex position resolution, particle momentum and algorithm configuration dependencies, background suppression and invariant mass resolution on the basis of a simulation. The new approach of vertex reconstruction works and achieves a vertex position resolution of 200μm. Moreover, accidental background can be greatly suppressed by the reconstruction of a common vertex. The results show that the linearised vertex fit is essential to achieve the proposed branching ratio sensitivity of 1× 10−16.