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[en] We present progress towards a measurement of the quantity δα_Had⁽⁵⁾(m_Z²), which represents the variation in the value of the electromagnetic coupling constant α between q² = 0 and m_Z² due to the effects of the 5 lightest quark flavors. This quantity is one of the leading uncertainties in the global electroweak fits performed at the Z pole, and thus on the indirect determination of the Higgs boson mass. We obtain this quantity from an integral of the cross section for e⁺e^- → q q-bar γ, where the photon originates from initial-state radiation (ISR)

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No abstract available

[en] The ASDEX upgrade vacuum vessel is equipped with 14 turbo molecular pumps (TMPs) and a cryo pump (CP). The CP is cooled with boiling helium (He). To obtain similar conditions with the CP for hydrogen (H₂) and deuterium (D₂) pumping a lower helium panel temperature (T_HP) is required in the case of H₂. This is achieved by reducing the He boiling pressure (p_b) and thus the He boiling temperature (T_b) via pump down of the He cryostat. The requirements are predicted by computations and verified experimentally for this case. By raising the cryostat pressure above ambient, the prediction of the H₂ end pressure (p_eH2) of the CP could be compared with measurements in the range 5x10^-7< p_eH2 (mbar)<5x10^-4. The beneficial effect of argon frosting for helium pumping is only shown experimentally

[en] Trigger efficiencies at BESIII were determined for both the J/ψ and ψ' data taking of 2009. Both dedicated runs and physics datasets are used; efficiencies are presented for Bhabha-scattering events, generic hadronic decay events involving charged tracks, dimuon events and ψ'→ π⁺π^-, J/ψ, J/ψ → l⁺l^- events. The efficiencies are found to lie well above 99% for all relevant physics cases, thus fulfilling the BESIII design specifications. (authors)

[en] To study alternative divertor configurations in the ASDEX Upgrade (AUG) tokamak a new upper divertor, Div-IIo, with two in-vessel coils and a cryopump (CP) will be installed in 2022. For efficient density control in the new divertor configuration during plasma discharges, the CP has to guarantee an effective pumping speed for deuterium (D₂) of at least S_eff = 15 m³/s. The CP will be installed behind the inner divertor with a toroidal pumping gap of width 30 mm between the inner and outer divertor plates. It consists of 7 modules with a major radius of R = 1.2 m and a total active length of 5.4 m. To investigate reactor relevant D₂-He gas mixtures during upper single null discharges, the liquid helium cryo-panels are coated with activated charcoal as cryosorbent. For quick regeneration of the charcoal from the accumulated gases, heating wires on the cryo-panels are installed. To reduce the pumping speed during high density discharges, an in-vessel cryo valve between two modules is installed. The pumping speed can be reduced by 35%. The cryo-panels operate with saturated liquid helium (LHe) at a temperature of 4.4 K. The thermal radiation shield consisting of reflector and chevron-baffle operate with saturated liquid nitrogen (LN₂) at 80 K. To supply the new upper CP with LHe and LN₂ the existing LHe-LN₂-supply of the lower CP will be used. Therefore, an additional distributor box and a multi-channel transfer line to the upper CP have been installed in 2019.

[en] To allow highly granular trackers to contribute to first level trigger decisions or event filtering, a fast readout system with very high bandwidth is required. Space, power and material constraints, however, pose severe limitations on the maximum available bandwidth of electrical or optical data transfers. A new approach for the implementation of a fast readout system is the application of a wireless data transfer at a carrier frequency of 60 GHz. The available bandwidth of several GHz allows for data rates of multiple Gbps per link. 60 GHz transceiver chips can be produced with a small form factor and a high integration level. A prototype transceiver currently under development at the University of Heidelberg is briefly described in this paper. To allow easy and fast future testing of the chip's functionality, a bit error rate test has been developed with a commercially available transceiver. Crosstalk might be a big issue for a wireless readout system with many links in a tracking detector. Direct crosstalk can be avoided by using directive antennas, linearly polarized waves and frequency channeling. Reflections from tracking modules can be reduced by applying an absorbing material like graphite foam. Properties of different materials typically used in tracking detectors and graphite foam in the 60 GHz frequency range are presented. For data transmission tests, links using commercially available 60 GHz transmitters and receivers are used. Studies regarding crosstalk and the applicability of graphite foam, Kapton horn antennas and polarized waves are shown

[en] A new fast track reconstruction algorithm developed for the high track multiplicity environment of the Mu3e experiment where track uncertainties are dominated by multiple scattering is presented. The goal of the Mu3e experiment is to search for the LFV decay μ⁺ → e⁺e⁻e⁺. To reach the sensitivity of 10^-16 the experiment will be performed at a future high intensity beam line (HiMB) at the Paul-Scherrer Institute (Switzerland) providing more than 10⁹ muons per second. Muons with a momentum of about 28 MeV/c are stopped on a target. Their decay at rest, in which mainly low momentum electrons with energies below 53 MeV are produced, is measured by the Mu3e tracking detector consisting of four cylindrical layers of thin silicon pixel sensors. The high granularity of the pixel detector with a pixel size of 80 × 80 μm² allows for precise track reconstruction in the high occupancy environment of the Mu3e experiment reaching up to 100 tracks per readout frame of 50 ns. These tracks will be reconstructed online using a trigger-less readout scheme. The implementation of a fast 3-dimensional multiple scattering fit based on hit triplets, where spatial uncertainties are ignored, is described and performance results in the context of Mu3e experiment are presented. Also the implementation on Graphics Processor Units (GPUs) for fast online reconstruction is discussed