Abstract

If physics beyond the Standard Model is discovered at the LHC , the next challenge will be the identification of the underlying theory and the determination of its fundamental parameters. Observables which are sensitive to masses or mass differences are of special interest, and there are various approaches to define them. An overview of possible observables will be given.

In R-parity conserving SUSY models a typical event topology at colliders will be the cascade decay of the two produced SUSY particles. Depending on the SUSY model cascade decays via SUSY particles of equal or similar masses at one particular position in the decay chains might occur with a high abundance. For the kinematics of all events the few masses of the involved SUSY particles are unknowns. The momentum components of the LSPs are also unknown parameters but unique for each event. If the cascades are sufficiently long, e.g. enough mass constraints are available, then the problem can be over constrained by making use of a large number of events. If an efficient selection of these events is possible one can utilize kinematic fits to determine the masses of the involved SUSY particles. In this talk techniques are presented for the solution of this problem. Additionally the problem of the huge combinatorial background is addressed.