The two-photon exclusive production of charged supersymmetric pairs at the LHC has a clean and unique signature - two very forward scattered protons and two opposite charged leptons produced centraly. For low-mass SUSY scenarios, significant cross-se
ctions are expected and background processes are well controlled. Measurement of the forward proton energies would allow for mass reconstruction of right-handed sleptons and the LSP with a few GeV resolution. Methods to reduce backgrounds at high luminosity resulting from accidental coincidences between events in the central and forward detectors are discussed.
A significant fraction of pp collisions at the LHC will involve (quasi-real) photon interactions occurring at energies well beyond the electroweak energy scale. Hence, the LHC can to some extend be considered as a high-energy photon-photon or photon-
proton collider. This offers a unique possibility for novel and complementary research where the available effective luminosity is small, relative to parton-parton interactions, but it is compensated by better known initial conditions and usually simpler final states. This is in a way a method for approaching some of the issues to be addressed by the future lepton collider. Such studies of photon interactions are possible at the LHC, thanks to the striking experimental signatures of events involving photon exchanges, in particular the presence of very forward scattered protons.
The detection of pairs of sleptons, charginos and charged higgs bosons produced via photon-photon fusion at the LHC is studied, assuming a couple of benchmark points of the MSSM model. Due to low cross sections, it requires large integrated luminosit
y, but thanks to the striking signature of these exclusive processes the backgrounds are low, and are well known. Very forward proton detectors can be used to measure the photon energies, allowing for direct determination of masses of the lightest SUSY particle, of selectrons and smuons with a few GeV resolution. Finally, the detection and mass measurement of quasi-stable particles predicted by the so-called sweet spot supersymmetry is discussed.
Computing the trajectories of particles in generic beamlines is an important ingredient of experimental particle physics, in particular regarding near-beam detectors. A new tool, Hector, has been built for such calculations, using the transfer matrix
approach and energy corrections. The limiting aperture effects are also taken into account. As an illustration, the tool was used to simulate the LHC beamlines, in particular around the high luminosity interaction points (IPs), and validated with results of the Mad-X simulator. The LHC beam profiles, trajectories and beta functions are presented. Assuming certain forward proton detector scenarios around the IP5, acceptance plots, irradiation doses and chromaticity grids are produced. Furthermore, the reconstruction of proton kinematic variables at the IP (energy and angle) is studied as well as the impact of the misalignment of beamline elements.
