Production of light flavor hadrons and anti-nuclei at the LHC

With the recording of the first collisions of the Large Hadron Collider (LHC) in November 2009, a new era in the domain of high energy and relativistic heavy-ion physics has started. As one of the early observables which can be addressed, the measurement of light quark flavor production is presented in this thesis. Hadrons that consist only of u, d, and s quarks constitute the majority of the produced particles in pp and Pb–Pb collisions. Their measurement forms the basis for a detailed understanding of the collision and for the answer of the question if hadronic matter undergoes a phase transition to the deconfined quark-gluon plasma at high temperatures. The basics of ultra-relativistic heavy- ion physics are briefly introduced in the first chapter followed by a short description of the ALICE experiment. A particular focus is put on the unique particle identification (PID) capabilities as they provide the basis of the measurements which are presented in the following chapters. The particle identification via the specific energy loss in the Time Projection Chamber (TPC) is an essential part of the overall particle identification within the experiment. Its underlying principles, the complex extraction of relevant calibration parameters, and the achieved performance belong to the main topics of this thesis and are presented in the second chapter. The particle identification with the TPC can be directly used for the extraction of transverse mo- mentum (pt) spectra of charged pions, kaons, and protons. The analysis, together with its related systematic error, is discussed in detail in the third chapter. In order to enlarge the pt-range of the spectrum, the analysis presented in this thesis was extended by a combined PID of the TPC dE/dx signal together with the information from the Time-of-Flight (TOF) system. Together with two in- dependent analyses, which are based on stand-alone tracking and PID in the Inner Tracking System (ITS) and on a TPC-independent PID with the TOF, a complete pt-spectrum can be obtained. The different and independent analyses are overlapping in several pt-intervals and provide thus a useful cross-check of the results. In the fourth chapter, the resulting pt-spectra of pions, kaons, and pro- tons are put into a larger context based on complementing ALICE measurements on strange particle production. In particular, it is found that the measured particle yields follow the trend from lower energies and that strange particle production in pp collisions is suppressed with respect to Pb–Pb collisions. The measurement of light anti- and hyper-nuclei is presented in the following chapter. It is shown that nuclei up to the 4He can be observed. The basic identification, reconstruction, and efficiency correction techniques for anti- and hyper-nuclei are outlined. In addition to this, trigger strategies for future running and searches for unknown hyper-matter states are briefly discussed. The thesis concludes in the last chapter with an interpretation of the obtained results based on hydrodynamical and thermal models. In particular, preliminary thermal fits of the measured particle yields are shown.