Kaon production in mid-rapidity in Be+Be collisions at the CERN SPS

Abstract

This thesis presents inclusive spectra of identified charged hadrons, namely K + , K − , π + , π − , proton and anti-proton, produced in inelastic 7 Be+ 9 Be collisions at four beam momenta: 30A, 40A, 75A and 150A GeV/c. The data acquisition was performed by the NA61/SHINE Collaboration with the NA61/SHINE fixed target experiment placed at CERN SPS. The hadron production in Be+Be collisions was measured and studied for the first time in SPS energy range. Charged-hadron identification was obtained with the so-called tof − dE/dx analysis method, based on measurements of hadron mass by Time of Flight detectors and energy loss by Time Projection Chambers. The results were corrected for effects related to the spectrometer acceptance, detection and reconstruction efficiency, the contribution of particles originating in weak decays and secondary interactions, as well as the analysis technique. The double-differential particle spectra were derived as a function of rapidity and transverse momentum. Particular attention was paid to the strangeness production in mid-rapidity by studying the charged K meson spectra. The K + and K − yields in mid-rapidity were calculated and the transverse momentum spectra were parametrised by the inverse slope parameter. These results were further used in the study of the onset of deconfinement and the phenomenon of the light-nuclei collisions at ultra-relativistic energies. The identification of charged-hadron spectra in Be+Be collisions belongs to the main NA61/SHINE programme of the onset of deconfinement of strongly interacting matter study in collisions of light and intermediate-size ions. The results on strangeness production in mid-rapidity, derived in the framework of this thesis, were compared with the results from p+p interactions and Pb+Pb collisions at the same beam momenta per nucleon, measured by the NA61/SHINE and NA49 experiments, respectively, and also world data in broader collision energy range. Furthermore, the results on charged-kaon spectra in mid-rapidity were compared with the calculation of three microscopic theoretical models of high-energy nuclear collisions and confronted with the prediction of the Statistical Model of the Early Stage