A new model-independent analysis of $B \to X_{s\gamma}$ in supersymmetry

Using the example of the rare decay $B \to X_s \gamma$, we analyse the importance of interference effects for the bounds on the parameters in the squark mass matrices within the unconstrained MSSM. In former model-independent analyses no correlations between the different sources of flavour violation were taken into account. In our new analysis we include the contributions from charged Higgs bosons, charginos and neutralinos and their interference effects and, even more important, the effects that appear when several flavour violating parameters, i.e. several off-diagonal elements in the squark mass matrices, are switched on simultaneously. We derive new bounds on certain off-diagonal elements of the squark-mass matrix which are in general one order of magnitude weaker than the previous bounds.