Orateur
Description
ALICE is one of the experiments of the LHC (Large Hadron Collider) at CERN (European Organization for Nuclear Research). The purpose of ALICE (A Large Ion Collider Experiment) is to study the properties of strongly interacting matter by performing different kinds of measurements in proton-proton, proton-nucleus and nucleus-nucleus collisions. The first detector encountered by collisions' products is the ITS (Inner Tracking System).
In prevision of the Run 3 of the LHC, that will start in 2022, many detectors of ALICE were upgraded, the ITS being one of those. During the commissioning of this tracking system in 2020, cosmic-ray data were taken. The ITS is built of ALPIDE (ALICE Pixel Detector) silicon sensors that allow for detecting particles by means of their pixels that become activated when particles cross sensors. When several neighbouring pixels are activated during the same particle crossing, they form a cluster. This talk shall present two ongoing studies.
First, a study of the shape of these clusters with real data from the commissioning but also with data generated by the official ALICE's Monte-Carlo simulation code. We investigate the impact of various parameters on the clusters' shape such as the dimensions of the pixels and especially the inclination of particle tracks with respect to the surface of sensors.
With the recent upgrades of the ITS, the first detection layers are closer to the primary vertex (the collision point). This is a huge improvement in secondary vertex reconstruction which is important for short-lived heavy-flavour hadrons like $\Xi_b^-$ for instance, which is at the heart of this second study via a specific decay channel: $\Xi_b^- \to (\Xi_c^0 \to \Xi^- \pi^+) \pi^-$. The desire is to create an analysis prototype using a state-of-the-art detector and a brandnew technique called strangeness tracking. The purpose of strangeness tracking is to improve the efficiency and precison of the reconstruction of weakly decaying particles (such as $\Xi^-$ or hypertritons). This can be achieved using silicon detectors with a few layers very close to the primary vertex. These layers will provide the tracking algorithm with information about the decaying particle before it actually decays.
