用ATLAS探测器重建能量为900 GeV和7 TeV的$pp$碰撞的主顶点
Reconstruction of primary vertices in $pp$ collisions at energies of 900 GeV and 7 TeV with the ATLAS detector
摘要：
欧洲核子研究组织（CERN）的大型强子对撞机（LHC）于2009年秋季开始运行。最初的运行在一个中心的质量能量为900 GeV，随后一直在进行中的运行在7 TeV的能量。虽然最初在同一束流交叉中发生多个质子-质子碰撞的概率约为10^-5，但随着LHC束流在碰撞点的更好聚焦和压缩，堆积的水平稳步增长。在这方面的贡献是主要的顶点重建算法用于分析在大型强子对撞机的第一次碰撞的性能。不同的方法用于重建的主要顶点在900 GeV和7 TeV的碰撞。的效率的主要顶点重建用于ATLAS的第一次物理分析。通过研究人工生成的半顶点之间的距离拉力的分布，研究了重建的主顶点的位置分辨率。ATLAS的性能方面的主要顶点重建正在进行的和未来的物理分析的影响进行了讨论。
英文摘要：
The Large Hadron Collider (LHC) of the European Organisation for Nuclear Research (CERN) started its operation in Autumn of 2009. The initial run at a centre-of-mass energy of 900 GeV, has been followed by the on-going run at the energy of 7 TeV. While initially the probability of several proton-proton collisions to happen within the same bunch-crossing was approximately 10^-5, the level of the pile-up grows steadily with better focusing and squeezing of the LHC beams at collision point. Presented in this contribution is the performance of the primary vertex reconstruction algorithms used for analysis of the first collisions at the LHC. Different approaches used for the reconstruction of primary vertices in 900 GeV and 7 TeV collisions are presented. The efficiencies of the primary vertex reconstruction used for the first physics analyses of ATLAS are shown. The resolutions on positions of the reconstructed primary vertices are investigated by studying the distributions of pulls of distance between artificially created half-vertices. Implications of the ATLAS performancewith respect to primary vertex reconstruction for the on-going and future physics analyses are discussed.
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