ALICE is one of the four experiments at the CERN LHC (Large Hadron Collider) which has started its activity the 10th of September 2008. Though a large physics program for the expected p-p collisions (up to 14TeV) has been planned, ALICE is the LHC experiment devoted also to heavy ion collisions (Pb-Pb at 5.5 ATeV), which have the goal to detect and study the Quark Gluon Plasma (QGP), the same matter which would have existed some microseconds after the Bing Bang. In order to explore all the observables needed to characterize this new state of matter, ALICE plans to detect and identify all the products of the beam collisions (hadrons, hadronic resonances, dileptons and direct photons, jets, high pT particles, open charm and open beauty). Due to this ambitious program, ALICE is a very complex experiment made by different sub-detectors [Figura_Alice] to address specific physics topics.
The ALICE experiment continuously took data during the first physics campaign of the LHC machine from fall 2009 until early 2013, using proton and lead-ion beams. The performance of the experiment was in good agreement with expectations and, as main result, the ALICE experiment confirmed that the QCD matter created in Pb-Pb collisions behaves like a perfect fluid, with strong collective motions that are well described by hydrodynamic equations. The first run was then followed by a long shutdown period of about 18 month dedicated to increasing the colliding beam's energies and the luminosity, on the accelerator side, and straighten the detectors on the experiments side. Data taking has been resumed again in 2015, first with proton-proton collisions at a center of mass energy of 13 TeV (about a factor 2 with respect to previous run), to be followed by a Pb-Pb run at 5 TeV per nucleon-nucleon collision.
During the construction phase, the Catania group has been involved in the realization of two sub-detectors:
- the Inner Tracking System (ITS), that consists of 6 layers of silicon detectors and is devoted to the vertex reconstruction and tracking of low-pT particles. Catania was one of the collaboration sites where the pixel sensors were tested in the clean room before the final assembly. Moreover, the Catania team is currently involved in the upgrade activities of the current ITS, that will be performed during the second long shutdown, in 2018.
- the Electromagnetic Calorimeter (EMCal), that is a Pb-scintillator sampling calorimeter devoted to the study of jets and high pT particles. The Catania group characterized the photosensors needed to read the scintillation light and contributed to the assembly of the EMcal modules.
Together with this experimental activity, the Catania team is also studying accurately the ability of the ALICE detector to reconstruct some hadronic resonances (such as K*(892) and φ(1020)) both in in p-p and in Pb-Pb collisions, in order to study the deconfinement and chiral symmetry restoration phenomena that should occur in the dense and hot matter produced at LHC.
The amount of data produced each year by the LHC experiments has required a complex GRID computing architecture both for the storing and physics analyses. Catania is one of 155 Tier 2 centres in the world where copies of experimental data are stored and specific analysis tasks are performed..
RESEARCH TEAM (2015)
A. Andronico, A. Badalà, R. Barbera, A.Grimaldi, P. La Rocca, F. Librizzi, S.Monforte, G. S. Pappalardo, O.Parasole, C. Petta, G.Platania, F. Riggi, D.Sciliberto,.
Catania Team Leader: Prof. Francesco Riggi