Study of collisional losses in the Large Hadron Collider for Pb-Pb and p-Pb operation

During about one month per operational year, the Large Hadron Collider (LHC) at CERN works as a heavy-ion collider. Fully-stripped lead ions ($^{208}$Pb$^{+82}$) are accelerated up to 7 $Z$ TeV and brought into collision between themselves (Pb-Pb) or with protons (p-Pb). Four one-month Pb-Pb runs have been executed so far as well as two p-Pb runs. The LHC heavy-ion programme is scheduled to continue in the future, featuring increased luminosity and beam energy. Beam losses caused by ions fragmenting in the collision process risk introducing performance limitations. Most notably, when colliding Pb-Pb nuclei, the bound-free pair production (BFPP) causes a localized power deposition downstream of each interaction point (IP), which can induce beam dumps or the quench of superconducting magnets, hence imposing an upper limit on the luminosity. This work aims both at studying alleviations of BFPP losses at the LHCb experiment, as well as setting up a reliable simulation model that can be used to predict collisional losses in future operation. For the first time a full analysis of the BFPP losses at LHCb has been conducted, adopting the simulation code SixTrack. A partial mitigation strategy by means of orbit bumps, which do not require any new hardware to be installed in the LHC, has been proposed. It would allow to safely increase the levelled luminosity of LHCb by a factor 2-3 in future runs. A new simulation approach to simulate the losses arising around the LHC ring during Pb-Pb and p-Pb collisions has been presented and benchmarked. It relies on the SixTrack-FLUKA coupling to simulate the beam-beam collisions at the IPs and track the collision products. Collisional lossmaps have been simulated and compared to the measured data for both 2018 Pb-Pb and 2016 p-Pb runs. The simulation approach proposed has proven capable of providing results with an excellent agreement with experimental data and it can be considered a valid tool to estimate the beam losses for future operation. Consequently, the prediction of Pb-Pb and p-Pb master lossmaps for future runs has been provided, including in the simulation setup all the changes envisaged for the next machine configuration.