Abstract (summary)
Fixed target experiments in particle physics provide the possibility of reaching a large number of particle collisions, allowing precise measurements of physics observables. CERN hosts a variety of fixed target experiments that aim at high-precision measurements, few of them located in the so-called North Area. These experiments make use of the 400 GeV/c proton beam extracted from the SPS that is led to collide on a target head to produce diverse particle species. Among these experiments there is NA62 that aims at measuring ultra rare decays (mainly K⁺ → π⁺νν̄) to a high precision (10% for K⁺ → π⁺νν̄) in order to challenge the Standard Model and conduct searches for new particles. In the case of NA62, the primary protons coming from the SPS are transported via a series of transfer lines to the P42 beam line, which guides the beam to the T10 beryllium target that generates a secondary beam. A 75 GeV/c positive particle component of the beam is selected by the K12 beam line; it contains about 6% of positive kaons that are afterwards transported to the NA62 experiment. Such a high precision experiment requires detailed Monte Carlo simulation models for understanding the beam and characterisation of the background. These models have been created and are studied within this thesis. The software tools used for the development are BDSIM, FLUKA and MADX. It is shown in particular that the beam in K12 can be simulated to a very high detail in BDSIM and FLUKA reaching an overall agreement with data within 1%. The BDSIM model is used to study background for muons generated along the beam line, showing satisfactory agreement with data for a large part of the spectrum. Finally, the FLUKA model is used to show that the background produced by particle interactions with the residual gas present in the vacuum tank is negligible. Besides NA62, more high-intensity experiments are currently being considered to take place in the P42 and K12 beam lines in future These are KLEVER, NA62-HIGH-INTENSITY, NA62-BEAM-DUMP and SHADOWS. The nature of these experiments is quite diverse and they all cover different physics topics, including Standard Model investigation and dark matter searches. Feasibility and characterisation studies for the beam lines of these experiments are carried out and presented in this thesis. In particular, it's shown in this thesis how the KLEVER beam line can be optimised regarding the radiation levels, calculated in FLUKA, outside the experimental hall. Studies on the P42 beam line in MADX and AppLE.py show that the current intensity for K12 can be increased using a target bypass technique useful for KLEVER and NA62-HIGH-INTENSITY. Finally, an NA62-BEAM-DUMP model is created in BDSIM and benchmarked to data for muon background characterisation. The same model is used for studies on the background reduction for SHADOWS that show first proof of feasibility of the experiment with the existing beam line design.