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The Mu3e Experiment: New Physics in Different Places? The Mu3e Experiment: New Physics in Different Places? Moritz Kiehn Université de Genève Département de physique nucléaire et corpusculaire DPNC Seminar, Genève, February 2017 Overview 1 1. Charged lepton flavor violation 2. Signal and background 3. Detector concept 4. Technologies 5. Reconstruction 6. Summary Moritz Kiehn The Mu3e Experiment:New Physics in Different Places? DPNC Seminar Flavor in the Standard Model 2 Three Generations of Matter (Fermions) I II III Initially: mass→ 2.4 MeV/c 2 1.27 GeV/c2 171.2 GeV/c 2 0 charge→ ⅔ ⅔ ⅔ 0 spin→ γ ½ u ½ c ½ t 1 • Quark transitions via weak interaction name→ up charm top photon 2 2 2 • 4.8 MeV/c 104 MeV/c 4.2 GeV/c 0 Lepton flavor conserved -⅓ -⅓ -⅓ 0 ½ d ½ s ½ b 1 g down strange bottom gluon Quarks Neutrino Mixing <2.2 eV/c 2 <2.2 eV/c2 <2.2 eV/c2 91.2 GeV/c 2 0 0 0 0 0 ½νe ½νμ ½ντ 1 Z • LFV in neutral sector electron muon tau Z boson neutrino neutrino neutrino • Charged sector? 0.511 MeV/c 2 105.7 MeV/c2 1.777 GeV/c2 80.4 GeV/c 2 -1 -1 -1 ±1 ± ½ e ½ μ ½ τ 1 W electron muon tau W boson Leptons Gauge Bosons Anything else? adapted from Wikipedia Moritz Kiehn The Mu3e Experiment:New Physics in Different Places? DPNC Seminar Charged lepton flavor violation? 3 In the Standard Model + + e W • Via neutrino mixing γ/Z 2 2 ∆mν • Suppressed by ∼ 2 mW − −50 e • Expected BR(µ ! eee) 10 µ+ νµ νe e+ Importance + + − + Example: µ ! e e e • Observable rate only from new physics • Sensitive new physics search Moritz Kiehn The Mu3e Experiment:New Physics in Different Places? DPNC Seminar Searches for charged lepton flavor violation 4 • Long history • Multiple future experiments planned W. Marciano et al. (2008), with modifications Moritz Kiehn The Mu3e Experiment:New Physics in Different Places? DPNC Seminar Beyond the Standard Model 5 e− + γ/Z e + µ+ e + − e+ µ e + E.g at loop level Contact-like e • Supersymmetry • Extra dimensions • Seesaw • New heavy bosons • … • … Moritz Kiehn The Mu3e Experiment:New Physics in Different Places? DPNC Seminar Effective theory 6 e− γ/Z + Dipole-like e Contact-like + µ+ e + − e+ µ e e+ Sensitive up to O(1000 TeV) Compare Kuno, Okada (2001) and de Gouvêa, Vogel (2013) Moritz Kiehn The Mu3e Experiment:New Physics in Different Places? DPNC Seminar Searches with muons 7 µ+ ! e+γ µ− + Au ! e− + Au µ+ ! e+e−e+ MEG upgrade Comet/Mu2e Mu3e: this talk Moritz Kiehn The Mu3e Experiment:New Physics in Different Places? DPNC Seminar Current Limits 8 cLFV Process BR @ 90 %CL Experiment + + − + −12 µ ! e e e <1 × 10 Sindrum Nucl.Phys. B299(1) + + −13 µ ! e γ <5:7 × 10 MEG arXiv:1303.0754 − − −13 µ + Au ! e + Au <7 × 10 Sindrum II Eur. Phys. J. C47 337–346 Moritz Kiehn The Mu3e Experiment:New Physics in Different Places? DPNC Seminar The Mu3e experiment 9 + + − + Search for µ ! e e e Planned sensitivity: 15 • Phase I: 2 in 10 decays (existing beamline) 16 • Phase II: 1 in 10 decays (future beamline) 4 orders of magnitude over previous experiment (SINDRUM 1988) Moritz Kiehn The Mu3e Experiment:New Physics in Different Places? DPNC Seminar The Mu3e collaboration 10 Paul Scherrer Institute Université de Genève ETH Zürich University Zürich Heidelberg University Karlsruhe Institute of Technology Mainz University Moritz Kiehn The Mu3e Experiment:New Physics in Different Places? DPNC Seminar Signal 11 e+ • Common vertex • Same time 2 2 + (Í ) = e • Pi mµ Í ® = 0 e- • pi (muon at rest) • p < 53 MeV Moritz Kiehn The Mu3e Experiment:New Physics in Different Places? DPNC Seminar Internal conversion background 12 + ν e • Common vertex • Same time ν Í 2 2 • ( Pi) < mµ Í • p®i , 0 e- • p < 53 MeV → Requires excellent momentum resolution e+ Moritz Kiehn The Mu3e Experiment:New Physics in Different Places? DPNC Seminar Internal conversion background 12 • Common vertex • Same time Í 2 2 • ( Pi) < mµ Í • p®i , 0 • p < 53 MeV → Requires excellent momentum resolution Djilkibaev, Konoplich, Phys.Rev.D79, 2009 Moritz Kiehn The Mu3e Experiment:New Physics in Different Places? DPNC Seminar Combinatorial background 13 e+ • from Michel decay, Bhabba scattering, photon conversion, … • No common vertex - e • Not same time → Requires good vertex resolution → Requires good time resolution e+ Moritz Kiehn The Mu3e Experiment:New Physics in Different Places? DPNC Seminar Multiple scattering 14 MS ∼ 1p / θMS p x X0 Mu3e example θMS • p = 35 MeV/c • 50 µm Si • ΩR = 5 cm Ω → ∆y ≈ 320 µm B → Scattering dominates Moritz Kiehn The Mu3e Experiment:New Physics in Different Places? DPNC Seminar Detector requirements 15 Environment e+ 9 + • High rate: >10 µ Decays/s • Low momentum: p <53 MeV • Multiple scattering dominates e+ Detector e- • Spatial resolution: <100 µm • Time resolution: <1 ns • Low mass: x/X0 ∼ 1 ‰ • Momentum resolution: 0:5 MeV Moritz Kiehn The Mu3e Experiment:New Physics in Different Places? DPNC Seminar Detector Layout 16 Question: Acceptance vs. resolution Moritz Kiehn The Mu3e Experiment:New Physics in Different Places? DPNC Seminar Detector Layout 16 Question: Acceptance vs. resolution Moritz Kiehn The Mu3e Experiment:New Physics in Different Places? DPNC Seminar Detector Layout 16 Question: Acceptance vs. resolution Moritz Kiehn The Mu3e Experiment:New Physics in Different Places? DPNC Seminar Detector Layout 16 Question: Acceptance vs. resolution Answer: both Moritz Kiehn The Mu3e Experiment:New Physics in Different Places? DPNC Seminar Recurling tracks 17 MS θ MS Momentum resolution dominated by multiple scattering σ θ p ∼ MS p Ω Ω ~ π B ∼ 1 p / with θMS p x X0 Uncertainty vanishes at Ω ∼ π (first order) Moritz Kiehn The Mu3e Experiment:New Physics in Different Places? DPNC Seminar Detector Concept 18 ̀ Beam Target 9 + • >10 µ Decays/s • Electrons p <53 MeV • Multiple scattering dominates Moritz Kiehn The Mu3e Experiment:New Physics in Different Places? DPNC Seminar Detector Concept 18 Inner pixel layers ̀ Beam Target 9 + • >10 µ Decays/s • Electrons p <53 MeV • Multiple scattering dominates Moritz Kiehn The Mu3e Experiment:New Physics in Different Places? DPNC Seminar Detector Concept 18 Inner pixel layers ̀ Beam Target Scintillating fibres Outer pixel layers 9 + • >10 µ Decays/s • Electrons p <53 MeV • Multiple scattering dominates Moritz Kiehn The Mu3e Experiment:New Physics in Different Places? DPNC Seminar Detector Concept 18 Recurl pixel layers Scintillator tiles Inner pixel layers ̀ Beam Target Scintillating fibres Outer pixel layers 9 + • >10 µ Decays/s • Electrons p <53 MeV • Multiple scattering dominates Moritz Kiehn The Mu3e Experiment:New Physics in Different Places? DPNC Seminar Paul Scherrer Institut 19 Paul Scherrer Institut Villigen, Switzerland www.psi.ch Proton accelerator 20 Proton accelerator 2:2 mA at 590 MeV Continuous beam 8 Muon beams 10 µ/s available Higher rates are under study www.psi.ch Experimental area and beamline 21 Infrastructure Removable platform II access stairway Access Infrastructure walkway platform I Controlled access door MEG II Target E Mu3e Detector control Existing πE5 and lter farm front access barracks πE5 beamline ∼28 MeV surface muons Shared with MEG Moritz Kiehn The Mu3e Experiment:New Physics in Different Places? DPNC Seminar Experimental area and beamline 21 Z- Branch Momentum Spectrum 4000 3500 3000 2500 Triplet II QSM ASK dipole Normalized Rate Normalized 2000 Triplet I ASC Singlet Dipole ASL dipole Split 1500 Triplet QSO PiE5 Channel AST Doublet 1000 Dipole Collimator 500 Mu3e solenoid Mu3e Triplet II 0 solenoid 25 26 27 28 29 30 31 32 33 Muon Momentum [MeV/c] πE5 beamline ∼28 MeV surface muons Shared with MEG Moritz Kiehn The Mu3e Experiment:New Physics in Different Places? DPNC Seminar Target 22 100 mm Simulated stopping distribution 900 20.8° 800 Entries 38 mm 700 600 75 μm Mylar 85 μm Mylar 500 400 300 200 19 mm 100 0 −40 −20 0 20 40 z of muon stop [cm] Thin, hollow, double-cone geometry Optimized stopping power Moritz Kiehn The Mu3e Experiment:New Physics in Different Places? DPNC Seminar Ultra-lightweight mechanics 23 • 50 µm Silicon sensor • 75 µm Kapton flexprint • 25 µm Kapton support frame → ∼1 ‰ Radiation length Moritz Kiehn The Mu3e Experiment:New Physics in Different Places? DPNC Seminar Ultra-lightweight mechanics 24 Outer layers Outer layer module Mupix sensor 50µm tap-bonds HDI ~100µm 4mm Mupix periphery polyimide 15µm 6mm V-shaped groove for stability and cooling Moritz Kiehn The Mu3e Experiment:New Physics in Different Places? DPNC Seminar Mechanical prototype 25 Silicon Pixel Sensors 26 Hybrid Monolithic Active Pixel Sensor Sensor 250 Monolithic Sensor 50 Readout chipμm 180 μm μm Pixel Pixel Connection via Pixel electronics solder bump On-chip interconnect Global logic and data driver Pixel electronics Global logic and data driver • HV ∼700 V • HV ∼80 V (HV-MAPS) • Sensor thickness ∼250 µm • Thin active zone <20 µm • Extra material • Cheap, commercial process • Complex, (expensive) Moritz Kiehn The Mu3e Experiment:New Physics in Different Places? DPNC Seminar 50 µm silicon 27 Monolithic Active Pixel Sensors 28 • HV ∼80 V (HV-MAPS) I. Peric, P. Fischer et al. NIMA 582(2007)876 • Fast charge collection by drift • Thin active zone <20 µm • Fully integrated readout electronics Moritz Kiehn The Mu3e Experiment:New Physics in Different Places? DPNC Seminar MuPix7 sensor prototype 29 2 • 103 × 80 µm pixel size 2 • 3:8 × 4:1 mm sensor size • Zero-suppressed, binary hits • Global threshold + per-pixel tune-dac • Fully integrated trigger-less readout • LVDS serial link 1:6 Gbit/s Moritz Kiehn The Mu3e Experiment:New Physics in Different Places? DPNC Seminar Testbeam at DESY External EUDET-type telescope Testbeam at PSI Custom
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