PoS(NuFACT2018)140 at the − e + e + https://pos.sissa.it/ e → + µ /s will be stopped inside a + µ 8 for the phase I detector described 15 − 10 · for the Mu3e Collaboration level, initially with a single event sensitivity of 2 ∗ 16 − [email protected] 10 · Speaker. The Mu3e experiment aims to measure the lepton-flavour violating decay 2 here. A DC muon beam at the Paul Scherrer Institute (PSI) of 10 Si pixel tracker constructed fromcomplemented with High-Voltage timing Monolithic detectors. Active An Pixel excellentthe momentum Sensors resolution low (HV-MAPS), is momentum achieved by positrons tracking (electrons)being inside the a limiting 1T factor magneticapproximately on field. 0.1% the of momentum a With resolution, radiation multipleto length. each scattering the detector required Currently, specifications, all layer and detector has their prototypesintegrate design a all is perform detector thickness being according systems finalized. of and The install collaboration the is experiment working at to PSI. ∗ Copyright owned by the author(s) under the terms of the Creative Commons c Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND 4.0). Johannes Gutenberg University Mainz E-mail: F. Wauters The search for Lepton-Flavour Violation withMu3e the Experiment The 20th International Workshop on Neutrinos12-18 (NuFact2018) August 2018 Blacksburg, Virginia PoS(NuFACT2018)140 to m µ F. Wauters ], aiming for a available at the 5 s , / 4 + ). For signal events, , 1 µ 3 , 8 2 , 1 , an improvement of 3 orders of ] which are thinned to 50 − 7 e + e + e → + µ 1 ]. 6 on the process 15 − 10 · 0.1% of a radiation length. To sufficiently suppress combinatorial backgrounds, ≈ , and Bhabha scattered positrons combined with a Michel positron from a second muon νν eee To identify candidate signal events, three electron/positron tracks need to be reconstructed. The Mu3e experiment will run at the Paul Scherrer Institute, where 10 Searching for Charged Lepton Flavour Violation (CLFV) in muon decays is a remarkabally → µ The full detector information needsFront-end to FPGA be boards read inside out the triggerless magnet before collect a the decision LVDS can serial be data taken. from 114 the detector ASICs, 1.2 Data Acquisition System and Reconstruction Figure 1: The Mu3e detector. Athe Si Michel pixel electrons/positrons tracker recurl achieves in optimalclose a momentum to resolution homogeneous the by magnetic stopping letting field. target allows An for inner good vertex central resolution. detector 2 positron tracks and 1summed electron energy track equal share to a the common muon vertex, mass. have a The balanced maindecay. momentum backgrounds An and excellent are a momentum internal resolution conversion betterbackground. decays, then 1 For MeV/c this is reason, requiredminimize to we multiple separate have scattering. signal developed from Combined HV-MAPScooling [ with gas, a and Kapton low-Z support flexthickness structure, print of ducts cables to for guide signal, helium additional timing control, detectors and are power, added: onecentral detector, 4 detector and layers layer a of scintillating has scintillating tile a detector fibers at between the the outer inner detector stations. and outer 1.1 The Mu3e detector sensitive method to search for new physics.grounds, The with CLFV a decays relatively are simple freeaccelerator from and Standard facilities clear Model provide signature back- a in the highis detectors. yield part of In of muons addition, ongoing as modern global a proton effort secondary searching beam. for CLFV The in Mu3e muon experiment decays [ Mu3e Status 1. The Mu3e Experiment single event sensitivity of 2 magnitude over the SINDRUM result [ compact muon beam line willdetector be is stopped a on cylindrical Si a pixel double-coned tracker mylar sitting target. in a At 1 its T heart, magnetic the field (figure Mu3e PoS(NuFACT2018)140 , ). 2 10 0.01 ± 0.00815 400 ± 5.578e+02 ± 14.34 2.012e+05 / 22 F. Wauters 0.05996 300 8.261e+05 200 / ndf 2 time difference / ns χ Constant Mean Sigma 15 ns (figure < 100 0 (c) 100 − 200 − 300 − 6 10 × 0

0.1 0.6 0.5 0.4 0.3 0.2 0.8 0.7

]. The 1.25 Gbit/s data from these ASICs Entries 12

], this reduction factor can be achieved with a noiserate per pixel / Hz / pixel per noiserate 8 1 − ]: Efficient charge collection allows for a wide 10 1 10 2 99.5% and a time resolution of 180 13 > 160 100. We showed that with commercial GPUs available efficiency noise ∼ 140 threshold / mV 120 (b) 100 ] for signal events in the acceptance of the detector. 80 9 60 40 1

0.8 0.9

0.95 0.85 efficiency (a) Since 2018 we have a full mechanical design of the experiment, and the collaboration is work- MuPix7, our small 32x40 pixel matrix 3x3 mm chip which meets all further requirements for Recent test-beam results show that both the scintillating fiber and the tile detector prototypes 15 ns. < ]. Our latest nearly full size prototype, the 1x2 cm MuPix8 chip, is currently under evaluation, Figure 2: The a) 1x2 cm large MuPix8 chip [ ing towards a full integrationvertical of slice all of detector the systems. databoth Test acquisition, timing beam and containing campaigns pixel prototypes are detectors. conducted of At with the PSI, a FPGA where readout the boards, experimental area reading is being prepared to host the range of working points with b)of optimal efficiency and a low noise figure, and c) a time resolution 2.2 Detector construction and commissioning the experiment, was extensively tested during 2016 and 2017 and showed good performance [ meet all requirements, with aare respective being time read resolution out of by 350 a ps custom and ASIC 70 called ps. MuTrig There [ SiPM signals 2. Status of the project 2.1 The pixel tracker and timing detector and shows promising results with efficiencies The final chip will be 2x2The cm. central Detector and modules are outer made trackersthe up combined from front-end will strips electronics. of contain 6 Thermo-mechanical 2844 tothe and chips, 18 mechanical cabling MuPix each design ASICs. mockups with of are a the being detector. 1.25 constructed Gbit/s to link test to is combined with the pixel data for further online processing. 11 98% reconstruction efficiency [ Mu3e Status and send it off viadata optical gets fibres distributed to to 12 thedetector FGPA+GPU hits. filter boxes, On farm each the at GPUs, machine a theget receiving written data events time are to rate slices disk reconstructed of with online containing a and about all today, reduction selected. and 100 factor Selected an Gbit/s. data optimized frames reconstruction There, algorithm the [ PoS(NuFACT2018)140 F. Wauters NuFact2017 (2017) 325 Nucl.Phys. , PoS − , e The MuPix . C39 + MuPix8: A large area e (2017) C01087. + Characterization e 12 −→ . + Nuovo Cim. ]. µ (2018) 01003 , 179 Nuclear Instruments and Methods in (2017) 008 , 1803.01581 [ . will be reached after 300 days of data taking. . 15 TWEPP-17 EPJ Web Conf. 3 Journal of Instrumentation . − Search for the Decay , , . 10 PoS · , . (2018) 158 (2017) 00013 (2007) 876 DeeMe experiment to search for muon to electron conversion at A902 150 (2017) 00005 COMET muon conversion experiment in J-PARC (2018) 109 A582 (2017) 104 Final Results of the MEG Experiment 150 Online data reduction using track and vertex reconstruction on GPUs for the Track reconstruction for the Mu3e experiment based on a novel multiple NuFact2017 Efficiency and timing performance of the MuPix7 high-voltage monolithic active EPJ Web Conf. , NuFact2017 Status of the Mu2e experiment ]. PoS . EPJ Web Conf. , Nucl. Instrum. Meth. , PoS Nucl.Instrum.Meth. , , . , Status and prospects of charged lepton flavor violation searches with the MEG-II collaboration, N. Teshima, A novel monolithic pixelated particle detector implemented in high-voltage CMOS . E (1988) 1 M EE 1606.08168 monolithic HVCMOS pixel detector for the mu3e experiment scattering fit B299 technology Mu3e experiment telescope: A thin, high-rate tracking telescope Measurement Results of MuTRiG - APrecision Silicon and Photomultiplier High Readout Event ASIC Rate with Capability High Timing Physics Research Section A: Accelerators, Spectrometers,(2018) Detectors and Associated Equipment pixel sensor J-PARC MLF [ experiment (2018) 107 [8] Kozlinskiy, Alexandr, [7] I. Peric, [5] S. Giovannella, [9] vom Bruch, Dorothea, [2] C. Voena, [1] MEG collaboration, T. Mori, [3]D [4] COMET collaboration, M. Lee, [6] SINDRUM collaboration, U. Bellgardt et al., [13] H. Augustin, N. Berger, S. Dittmeier, F. Ehrler, C. Grzesik, J. Hammerich et al., [10] H. Augustin et al., [11] H. Augustin, N. Berger, S. Dittmeier, C. Grzesik, J. Hammerich, Q. Huang[12] et al., H. Chen, W. Shen, K. Briggl, V. Stankova, Y. Munwes, D. Schimansky et al., References Mu3e Status experiment, our 1T magnet will besystem delivered in in 2019. 2020 once We are the expectingsingle first to event detector start sensitivity modules commissioning of the are phase constructed. I Mu3e Once of data 2 taking starts, the target