Study of $K^{0}_{S}$ meson production in NA61 experiment at the CERN SP

One of the main problems of heavy-ion physics is search for the quark-gluon plasma (QGP), study its properties and characteristics of the phase transition between hadron nuclear matter and the QGP. Existence of the QGP has been introduced by J. C. Collins and M. J. Perry in 1975 [1]. In the QGP quarks and gluons, fundamental constituents of known matter, are expected to appear as free particles. Outside the plasma they are always confined inside hadrons. Unfortunately the quark-gluon plasma can not be directly observed experimentally. However, there are certain phenomena that attest to its existence. These include strangeness production enhancement, suppression of J = , fluctuations and jet quenching. They allow to study properties the plasma. In 2008, the world’s most powerful particle accelerator – the LHC at CERN has been launched. In the nearest future it will be able to collide protons at the energy of up to 14 TeV per nucleon pair and lead ions at the maximum energy of 5.5 TeV per nucleon pair. There are four big and three smaller experiments located at the accelerator exploring the most interesting areas of high energy physics. However, due to too high energy, data on the QGP describe the area beyond the onset of deconfinement. NA61/SHINE (SPS Heavy Ion and Neutrino Experiment) operates at the SPS accelerator (Su- per Proton Synchrotron) at CERN with much less energy than in LHC. It focuses on the study of the phase transition and the expected critical point’s properties. This would allow to provide infor- mation on the formation of the plasma. NA61/SHINE studies QGP signatures at different available energies and using different sizes of projectile and target. In addition, the experiment collects refer- ence data for the T2K experiment (neutrino physics), and KASKADE-Grande experiment (cosmic ray physics). This thesis is devoted to the study of production processes of K 0 S mesons in collisions of beam of protons with a carbon target at the beam momentum of 30.9 GeV/c. Data was collected in 2007 by the NA61/SHINE experiment. The goal of the analysis was to understand better mechanisms of production of strange particles in collisions at the low SPS energies.