Speaker
Description
The ALICE Inner Tracking System (ITS) has recently been replaced with a full silicon-pixel detector constructed entirely with CMOS monolithic active pixel sensors. It consists of three inner layers (50 $\mu$m thick sensors) and four outer layers (100 $\mu$m thick sensors) covering 10 m$^2$ and containing 12.5 billion pixels with a pixel size of 27 $\mu$m x 29 $\mu$m. Its increased granularity, the very low material budget (0.35% X$_0$/layer in the inner barrel) as well as a small radius of the innermost layer combined with a thin beam pipe, will result in a significant improvement of impact-parameter resolution and tracking efficiency at low $p_{\rm T}$ with respect to the previous tracker. The assembly of the full detector and services finished in December 2019. A comprehensive commissioning phase (on surface) was completed in December 2020, including detector calibration, fake-hit rate determination, data transmission tests and preliminary evaluation of the detector efficiency and the sensors alignment, based on reconstruction of cosmic rays tracks. The commissioning of the ITS within the ALICE apparatus has recently started. After a first phase of standalone tests and detector performance optimization, the ITS will be included in the global commissioning activities in summer 2021. In this talk, the first results of the performance of the new ALICE ITS detector, studied during commissioning, will be presented.
| Collaboration / Activity | ALICE |
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