ICARUS at the Fermilab Short-Baseline Neutrino Program -- Initial Operation

The ICARUS collaboration employed the 760-ton T600 detector in a successful three-year physics run at the underground LNGS laboratory studying neutrino oscillations with the CERN Neutrino to Gran Sasso beam (CNGS) and searching for atmospheric neutrino interactions. ICARUS performed a sensitive search for LSND-like anomalous $\nu_e$ appearance in the CNGS beam, which contributed to the constraints on the allowed parameters to a narrow region around 1 eV$^2$, where all the experimental results can be coherently accommodated at 90% C.L.. After a significant overhaul at CERN, the T600 detector has been installed at Fermilab. In 2020, cryogenic commissioning began with detector cool down, liquid argon filling and recirculation. ICARUS has started operations and successfully completed its commissioning phase, collecting the first neutrino events from the Booster Neutrino Beam (BNB) and the Neutrinos at the Main Injector (NuMI) beam off-axis, which were used to test the ICARUS event selection, reconstruction and analysis algorithms. The first goal of the ICARUS data taking will then be a study to either confirm or refute the claim by Neutrino-4 short baseline reactor experiment both in the $\nu_\mu$ channel with the BNB and in the $\nu_e$ with NuMI. ICARUS will also address other fundamental studies such as neutrino cross sections with the NuMI beam and a number of Beyond Standard Model searches. After the first year of operations, ICARUS will commence its search for evidence of a sterile neutrino jointly with the Short Baseline Near Detector, within the Short-Baseline Neutrino program.