Flexprint design studies for the Mu3e experiment

The Mu3e experiment will search for the lepton-flavour violating decay μ⁺ → e⁺e^-e⁺ with a sensitivity of one in 10¹⁶ decays. To reach this sensitivity, an excellent momentum resolution as well as a very good vertex reconstruction are crucial. Since the muons will be stopped before decaying, their decay products will have very low momenta. Hence multiple scattering is a major issue that is tackled by minimizing the material budget of the tracking detector. In order to achieve this, the silicon pixel sensors will be thinned to 50 μm and mounted on flexprints consisting of very thin Kapton and aluminium (and possibly copper) traces for signals, power and ground. The material budget of the flexprints will be less than 0.5 of the radiation length of aluminium. This talk covers the design of the Mu3e pixel detector, focussing on the use of flexprints for the readout and supply of the pixel sensors. Results from measurements with flexprint prototypes as well as future designs are discussed.