Antiproton production measurement for indirect Dark Matter search at the AMBER experiment at CERN

The AMBER (Apparatus for Meson and Baryon Experimental Research) experiment is a newborn particle physics experiment located in the North Area at CERN. The beam accelerated by the Super Proton Synchrotron (SPS) impinges on a fixed target in the Experimental Hall N2 and the AMBER spectrometer allows the particle identification and track reconstruction of the particles produced in the collisions. The AMBER collaboration submitted in June 2019 a Proposal in order to establish a ”New QCD facility at the M2 beam line of the CERN SPS”. This thesis work fits in one of proposed measurement concerning the study of proton-induced antiproton production cross sections for indirect dark matter searches. Evidence strongly suggests that most of the universe’s matter is non-baryonic and electrically neutral, commonly referred to as Dark Matter (DM) due to its lack of electromagnetic interactions. A leading candidate for DM is the Weakly Interacting Massive Particle (WIMP), which is believed to decay or annihilate into standard model particles and appear as distortions in the spectra of rare cosmic ray components like positrons, antiprotons and heavier (anti-)nuclei. One way to test this hypothesis is by studying Cosmic Ray (CR), particles that arrive at the top of the Earth’s atmosphere. Indeed, the dominant part of the antiprotons in our galaxy originates from inelastic scattering of incoming cosmic rays off InterStellar Medium (ISM) nuclei at rest. In particular, the dominant reactions producing antiprotons involve Helium and proton and represents the background when searching for small contributions from exotic sources; in order to obtain a significant sensitivity to DM signals, it is then very important to achieve a small uncertainty on the prediction of cosmic anti-proton produced in the collision with proton and Helium. The idea is to study the antiproton production cross sections in pHe scattering for projectile energies from several tens to a few hundreds GeV/c. The AMBER experiment collected in 2023 precise data on pHe collision and in combination with similar measurements by LHCb in the TeV range, these data set represent the only available measurements with Helium. The new results are expected to allow for higher accuracy of the predicted natural flux of antiprotons in the galactic cosmic rays, especially in the relevant energy regime for space based spectrometer like AMS-02. This thesis project is focused on the preparation and the first analysis of the 2023 data with beam momentum at 190 GeV/c. In the first chapter, I provide an overview of the current scenario of the cosmic rays production and propagation mechanism and of the dark matter detection methods. Chapter two is dedicated to a description of the experimental apparatus, with a focus on the novelties of the 2023 setup. In chapter three the first tasks performed for the data analysis, which include the spetrometer alignment, vi the data quality and stability studies, the luminosity estimation and lifetime correction, are discussed. In the fourth chapter, I estimate the efficiency of the hadron beam tagging with the CEDARs and provide the characterization of the RICH-1 detector used for the particle identification of hadrons produced in interactions. The fifth chapter contains a description of the work that I performed on the preparation of the MonteCarlo chain and on the MonteCarlo related studies like the description of the target and the trigger system in the spectrometer simulation and the extraction of the tracking efficiency. Finally, in the last chapter I present the first results from the 190 GeV/c proton-helium collision, with the hadron spectra corrected for the acceptance of the apparatus and for the PID purity, compared to the expected shape predicted by the PYTHIA8 event generator.