Technical design of the phase I Mu3e experiment

The Mu3e experiment aims to find or exclude the lepton flavour violating decay μ→eee at branching fractions above 10−16. A first phase of the experiment using an existing beamline at the Paul Scherrer Institute (PSI) is designed to reach a single event sensitivity of 2⋅10−15. We present an overview of all aspects of the technical design and expected performance of the phase I Mu3e detector. The high rate of up to 108 muon decays per second and the low momenta of the decay electrons and positrons pose a unique set of challenges, which we tackle using an ultra thin tracking detector based on high-voltage monolithic active pixel sensors combined with scintillating fibres and tiles for precise timing measurements

Technical design of the phase I Mu3e experiment

The Mu3e experiment aims to find or exclude the lepton flavour violating decay $\mu \rightarrow eee$ at branching fractions above $10^{-16}$. A first phase of the experiment using an existing beamline at the Paul Scherrer Institute (PSI) is designed to reach a single event sensitivity of $2\cdot 10^{-15}$. We present an overview of all aspects of the technical design and expected performance of the phase~I Mu3e detector. The high rate of up to $10^{8}$ muon decays per second and the low momenta of the decay electrons and positrons pose a unique set of challenges, which we tackle using an ultra thin tracking detector based on high-voltage monolithic active pixel sensors combined with scintillating fibres and tiles for precise timing measurements.Comment: 114 pages, 185 figures. Submitted to Nuclear Instruments and Methods A. Edited by Frank Meier Aeschbacher This version has many enhancements for better readability and more detail

GPS velocity field for the Tien Shan and surrounding regions

Measurements at ∼400 campaign-style GPS points and another 14 continuously recording stations in central Asia define variations in their velocities both along and across the Kyrgyz and neighboring parts of Tien Shan. They show that at the longitude of Kyrgyzstan the Tarim Basin converges with Eurasia at 20 ± 2 mm/yr, nearly two thirds of the total convergence rate between India and Eurasia at this longitude. This high rate suggests that the Tien Shan has grown into a major mountain range only late in the evolution of the India-Eurasia collision. Most of the convergence between Tarim and Eurasia within the upper crust of the Tien Shan presumably occurs by slip on faults on the edges of and within the belt, but 1–3 mm/yr of convergence is absorbed farther north, at the Dzungarian Alatau and at a lower rate with the Kazakh platform to the west. The Tarim Basin is thrust beneath the Tien Shan at ∼4–7 mm/yr. With respect to Eurasia, the Ferghana Valley rotates counterclockwise at ∼0.7° Myr−1 about an axis at the southwest end of the valley. Thus, GPS data place a bound of ∼4 mm/yr on the rate of crustal shortening across the Chatkal and neighboring ranges on the northwest margin of the Ferghana Valley, and they limit the present-day slip rate on the right-lateral Talas-Ferghana fault to less than ∼2 mm/yr. GPS measurements corroborate geologic evidence indicating that the northern margin of the Pamir overthrusts the Alay Valley and require a rate of at least 10 and possibly 15 mm/yr.Russian Basic Research FoundationNational Science Foundation (U.S.) (Grant EAR‐8915334)National Science Foundation (U.S.) (Grant EAR‐9117889)National Science Foundation (U.S.) (Grant EAR‐9614302)National Science Foundation (U.S.) (Grant EAR‐9708618)National Science Foundation (U.S.) (Grant EAR‐0636092)National Aeronautics and Space Administration (Grant NAG5‐1941)National Aeronautics and Space Administration (Grant NAG5‐1947