Higgs "Photo-Production" and Related Experimental Issues in the Forward Direction of the ATLAS Detector

This thesis is devoted to the study of aspects of the forward physics and forward detector system of the ATLAS detector. The first topic involves LUCID, the official luminosity monitor of ATLAS during Run-2. Here we concentrate on the simulation, calibration system and performance of the LUCID-2 detector. The second topic covers the ATLAS Forward Proton (AFP) detector. In this case, the testing and performance studies of the readout electronics for the precision AFP ToF detector - required to reduce pile-up background - are the key issues. The main topic is devoted to the study of Higgs production in Central Exclusive Diffractive (CED) processes with the ATLAS detector at the LHC. A detailed calculation of diffractive ultra-peripheral CED "photoproduction" of the Higgs boson, in proton-proton and heavy-ion - proton interactions at the LHC, is presented for the first time. CED Higgs production via Double Pomeron Exchange is also studied using the same calculation techniques and compared with other well reported results in this area. This was done as a test of the techniques used and in order to assess the error on the cross-section for Higgs "photoproduction" reported in this thesis.