The pixelation technique in the timing analysis of the data collected by the FARCOS correlator in the CHIFAR experiment

The main aim of the CHIFAR experiment, carried out at INFN-LNS, was the investigation of the emission probability of Intermediate Mass Fragments (IMFs) in non-central Heavy Ion Collisions. This phenomenon is linked to the features of the Equation of State of nuclear matter, focusing also on the role of the isospin degree of freedom of the colliding nuclei. The CHIMERA Collaboration has investigated six nuclear reactions at 20 AMeV beam energy, achieved by combining three beams —124Sn, 112Sn, 124Xe— and three targets —64Ni, 58Ni, 64Zn. The experimental setup consisted of the CHIMERA multi-detector coupled to 10 telescopes of the FARCOS (Femtoscope ARray for COrrelations and Spectroscopy) correlator. The triple array configuration of FARCOS is based on 2 DSSSDs (Double Sided Silicon Strip Detectors, 300 μm and 1500 μm thick, respectively) and 4 CsI crystals (6 cm thick). The high energy and angular resolution of FARCOS make it an appropriate tool for intended research: the IMFs can be identified up to Z ≈ 16, and furthermore the coupling with CHIMERA allows to study correlations among IMFs and light charged particles produced in the nuclear reactions. The results obtained by the “pixelation” technique will be explained. According to a timing analysis applied to the data collected by the two DSSSDs, the position of each detected particle can be assigned unambiguously, from the crossing of a strip of the front side to another of the back side, considering its angles in the laboratory frame (polar angle θ and azimuthal angle φ).