Speaker
Description
The ALICE Inner Tracking System (ITS) is responsible for vertex reconstruction and charged particle tracking in the vicinity of the interaction point. The current ITS2 was installed during the LHC Long Shutdown 2 (2018-2022) and is completely based on the Monolithic Active Pixel silicon Sensor (MAPS). It has an active surface of 10 m2 with nearly 12.5 billion pixels, thus representing the largest application of MAPS. The ITS2 is composed of seven concentric layers equipped with the ALPIDE chip, a sensor implemented in a 180 nm CMOS technology, designed specifically for the ALICE ITS2.
ITS2 has an enhanced tracking performance in terms of impact-parameter resolution and efficiency at low transverse momentum during Pb-Pb collisions at interaction rates of up to 50 kHz. This is achieved through its increased granularity (pixel pitch of 27×29 μm2), low material budget of 0.36% X0 per layer for the three innermost layers, and the placement of the first layer at a radial distance of 23 mm from the interaction point.
This contribution will give an overview of ITS2 operational experience during LHC Run 3 (2022-2026), with a particular focus on detector calibration and tracking performance, including operational insights as beam background effects, investigations on data reconstruction for readout frames of variable timing/length and exploratory studies on energy-loss measurements, from which the development of future detectors as ITS3 and ALICE 3 will profit.