Performance of the LHCb Vertex Locator
Performance of the LHCb Vertex Locator
复制标题
DOI：
10.1088/1748-0221/9/09/p09007
复制
发表时间：
2014-09-01
影响因子：
1.3
通讯作者：
Zverev, E.
中科院分区：
文献类型：
--
作者：
Aaij, R.;Affolder, A.;Zverev, E.
顶点定位器（VELO）是一种硅微条探测器，它环绕着大型强子对撞机底夸克实验（LHCb）中的质子 - 质子相互作用区域。本文回顾了该探测器在其物理运行的最初几年中的性能。该系统在真空中运行，使用双相二氧化碳冷却系统，并且在获取物理数据时传感器移动到距离大型强子对撞机束流7毫米处。描述了探测器这些特性的性能和稳定性，并给出了材料预算的细节。介绍了在现场可编程门阵列（FPGA）中实现的定时校准和数据处理算法。对系统性能进行了全面的表征。传感器的信噪比约为20，在最佳径迹角度下可实现4微米的最佳击中分辨率。2011年标准运行条件下最小偏置事件的典型探测器占有率约为0.5%，并且探测器有不到1%的故障条。探测器靠近束流意味着n⁺ - on - n传感器的内部区域由于辐射损伤已经发生了空间电荷符号反转。还给出了影响实验物理灵敏度的VELO性能参数。VELO的径迹寻找效率通常高于98%，并且模块在垂直于束流的平面内平移时已对准到1微米的精度。对于有25条径迹的顶点，在横向平面内实现了13微米的初级顶点分辨率，沿束流轴方向实现了71微米的分辨率。对于横向动量大于1GeV/c的粒子，实现了小于35微米的碰撞参数分辨率。
The Vertex Locator (VELO) is a silicon microstrip detector that surrounds the proton-proton interaction region in the LHCb experiment. The performance of the detector during the first years of its physics operation is reviewed. The system is operated in vacuum, uses a bi-phase CO2 cooling system, and the sensors are moved to 7mm from the LHC beam for physics data taking. The performance and stability of these characteristic features of the detector are described, and details of the material budget are given. The calibration of the timing and the data processing algorithms that are implemented in FPGAs are described. The system performance is fully characterised. The sensors have a signal to noise ratio of approximately 20 and a best hit resolution of 4 mu m is achieved at the optimal track angle. The typical detector occupancy for minimum bias events in standard operating conditions in 2011 is around 0.5%, and the detector has less than 1% of faulty strips. The proximity of the detector to the beam means that the inner regions of the n(+)-on-n sensors have undergone space-charge sign inversion due to radiation damage. The VELO performance parameters that drive the experiment's physics sensitivity are also given. The track finding efficiency of the VELO is typically above 98% and the modules have been aligned to a precision of 1 mu m for translations in the plane transverse to the beam. A primary vertex resolution of 13 mu m in the transverse plane and 71 mu m along the beam axis is achieved for vertices with 25 tracks. An impact parameter resolution of less than 35 mu m is achieved for particles with transverse momentum greater than 1GeV/c.