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[en] The Mu3e experiment will search for the lepton flavour violating decay of a positive muon into two positrons and an electron, which is suppressed to unobservable levels in the Standard Model. A signal would be a clear sign of new physics. The aim is to reach a sensitivity for the branching ratio of 10"-"1"6. This requires high momentum resolution of the tracking detector. Since the muons will decay at rest on target the energy of the decay electrons is E ≤53 MeV. In this energy regime the momentum resolution is limited by multiple scattering in the detector material. Therefore, the entire detector, including the support structure and services, has to consist of as little material as possible. The main component of the Mu3e detector is a tracking detector consisting of four cylindrical layers of high-voltage monolithic active pixel sensors (HV-MAPS) that can be thinned to 50 μ m. A power consumption of 400 (mW)/(cm"2) is expected. To keep the material budget low, the detector will be cooled with gaseous helium. In this talk results of experimental tests as well as computational fluid dynamics simulations of the Mu3e cooling system are presented.

[en] Today's high energy physics experiments produce large amounts of data in a short time. The fast readout of this data is a big challenge. The license-free 60 GHz band allows for short distance applications with high data rates of the order of several Gb/s. The transceivers can be produced in SiGe HBT BiCMOS technology. As we are dealing with mm-waves, even antennas, which increase the directivity of the transmission, can be built in small structures. So, this technique seems very promising for the readout of particle detectors. For example, it can be used for the readout of the upgraded ATLAS silicon micro-strip tracker and make a first level track trigger feasible. We present first results of our tests with semi-commercially available 60 GHz transceivers regarding the usage in a high energy physics experiment. We examined the intensity of the carrier signal regarding reflectivity and absorption using graphite foam. Moreover, we tested the directivity of a horn antenna made from Kapton. We furthermore investigated the quality of a modulated signal with respect to bit errors using pseudo-random data as well as real data files.

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[en] The Mu3e experiment - searching for the lepton-flavour violating decay of the muon into three electrons at an unprecedented sensitivity of one in 10"1"6 decays - is based on a pixel tracking detector. The sensors are High-Voltage Monolithic Active Pixel Sensors, a technology which allows for very fast and thin detectors. This makes it an ideal fit for the high rate and low-momentum environment of Mu3e, where momentum resolution is dominated by multiple Coulomb scattering. As the detector will consist of about 275 million pixels and will be operated at up to 10"9 muon stops per second, fast data readout is crucial. The current sensor prototype MuPix7 features a readout control state machine on-chip. This allows for sending zero-suppressed hit data to an FPGA via an 800 Mbit/s LVDS link. This FPGA buffers the data and sorts it by time stamps before processing and sending to the next readout stage. The MuPix7 design including its readout architecture is presented.