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Mu2e: Coherent Μ→E Conversion Experiment at Fermilab

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Mu2e: Coherent Μ→E Conversion Experiment at Fermilab Mu2e: Coherent μ→e Conversion Experiment at Fermilab David Brown, LBNL representing the mu2e collaboration Charged Lepton Flavor Violation • ν mixing implies Charged Lepton Flavor Violation (CLFV) • Predicted rate is un-observably small • Any observation of 0-ν μ→e transition would be an unambiguous sign of new physics • similar story for τ→μ, τ→e David Brown, Lawrence Berkeley National Lab 2 mu2e conversion at FNAL PANIC 2011 CLFV in µ+→e+γ and µ-N→e-N Model independent effective CLFV Lagrangian Loops ‘Contact’ Interactions κ << 1 κ >> 1 µ → eγ rate ~100X µN → eN >> µN → eN rate µ → eγ rate David Brown, Lawrence Berkeley National Lab 3 mu2e conversion at FNAL PANIC 2011 David Brown, Lawrence Berkeley National Lab Berkeley Lawrence Brown, David - - accessible by µ N → e N PossibleSources of Many models predict detectable signals for for signals detectable predict models Many and µ- → e-γ 4 Marciano, Mori, and Roney , Ann. Rev. Nucl.58 Sci. Ann. Rev. Marciano, Mori,and Roney , mu2e conversion at FNAL conversion mu2e μ → Λ >> 1 TeV >> 1 e PANIC 2011 PANIC accessible by µ-N → e-N μ→e Conversion • μ- + N form muonic atom µ-N → e-N μ- tightly bound in K shell • ~20 fm • significant WF overlap with N μ- e- ~4 fm • μ- converts coherently with N • e- recoil is against N • N WF can participate in process • Unique Experimental Signature - • isolated, mono-energetic e with Pe ≅ mμ David Brown, Lawrence Berkeley National Lab 5 mu2e conversion at FNAL PANIC 2011 Status of CLFV Searches MEG arXiv:1012.2110 David Brown, Lawrence Berkeley National Lab 6 mu2e conversion at FNAL PANIC 2011 The Mu2e Experiment • Experimental Goal: Measure the ratio Rμe -17 • 90% C.L. sensitivity to Rμe > 6×10 • 4 orders of magnitude better than current limits • Requires ~ 1018 stopped muons • ~ 4×1020 protons on target (2 year run @ 25 KW) • Requires negligible (<1) background events • Many challenges for beamline and detector design David Brown, Lawrence Berkeley National Lab 7 mu2e conversion at FNAL PANIC 2011 Best Previous Measurement SINDRUM-II Prompt Background ❚ Prompt Beam π + N → N*→ N + γ ❚ Cosmic γ + N → N + e+e- Induced ❚ µ Decay -13 Rμ(Ti) < 6.1X10 David Brown, Lawrence Berkeley National Lab 8 mu2e conversion at FNAL PANIC 2011 The Mu2e Collaboration Boston University Brookhaven National Laboratory University of California, Berkeley University of California, Irvine California Institute of Technology City University of New York Duke University Fermilab University of Houston University of Illinois, Urbana-Champaign Institute for Nuclear Research, Moscow, Russia JINR, Dubna, Russia INFN Lecce, Università del Salento, Italy Lawrence Berkeley National Laboratory Rice University Los Alamos National Laboratory Syracuse University Northern Illinois University/Lewis University of Virginia Northwestern University College of William and Mary INFN Frascati University of Washington, Seattle INFN Pisa, Università di Pisa, Pisa, Italy ~120 collaborators David Brown, Lawrence Berkeley National Lab 9 mu2e conversion at FNAL PANIC 2011 Mu2e at FNAL Mu2e Building New transfer line Conditioning in Protons Accumulator and from Booster Debuncher No intereference with NOVA David Brown, Lawrence Berkeley National Lab 10 mu2e conversion at FNAL PANIC 2011 Mu2e Apparatus Proton Beam 2.0 T 2.5 T 5.0 T 1.0 T stopping Texttarget ~ 20 meters • Proton delivery beamline • SC solenoids for muon collection, transportation, and analysis • Primary (proton) and secondary (muon) targets • Active devices: tracker, calorimeter, Cosmic Ray veto David Brown, Lawrence Berkeley National Lab 11 mu2e conversion at FNAL PANIC 2011 Muon (pion) production Heavy W, Cu shielding protects SC coil 8 GeV Protons delivered off- axis to Au target Graded field reflects and focuses low-Pz particles David Brown, Lawrence Berkeley National Lab 12 mu2e conversion at FNAL PANIC 2011 Momentum Selection ʻSʼ bend transports charged particles, blocks line-of-sight neutrals muons → ʻDʼ Collimators select low-momentum negative particles David Brown, Lawrence Berkeley National Lab 13 mu2e conversion at FNAL PANIC 2011 Muon Stopping and Decay Low Pz e- reflected by graded field Muons stop in thin- film Al (Ti) targets e- energy measured in crystal calorimeter e- momentum measured by straw tracker (in vacuum) David Brown, Lawrence Berkeley National Lab 14 mu2e conversion at FNAL PANIC 2011 Achieving 10-17 Sensitivity • Reduce prompt beam backgrounds • Pulsed beam with < 10-10 inter-pulse rates • ʻSʼ bend transport away from proton target • Veto cosmic rays • Shielding • Active veto with ϵ > 99.99% • Minimize signal window • Precision low-mass tracker • σP/P ~ 10-3 David Brown, Lawrence Berkeley National Lab 15 mu2e conversion at FNAL PANIC 2011 Beam Timing Inter-bunch protons < 10-10 Muon stopping time ~900 nsec • Prompt pions decay rapidly • τ = 26 nsec • Muons survive to reach the stopping target • Stopped muon lifetime on Al ~800 nsec David Brown, Lawrence Berkeley National Lab 16 mu2e conversion at FNAL PANIC 2011 e- Momentum Measurement Tracker has acceptance only for high-P electrons David Brown, Lawrence Berkeley National Lab 17 mu2e conversion at FNAL PANIC 2011 Momentum Sensitivity Decay in orbit Long tail due to nuclear recoil Conversion Electron Signal Window Shanker, Phys.Rev D25, 1847 New calculation by Czarnecki etal (1982) agrees within 30% arXiv:1106.4756v1 David Brown, Lawrence Berkeley National Lab 18 mu2e conversion at FNAL PANIC 2011 Backgrounds for 2×107 s Running Source Events Comment Anti-proton capture 0.06 ± 0.06 Radiative π- capture 0.04 ± 0.02 Assumes 10-10 extinction Beam electrons 0.001 ± 0.001 μ decay in orbit 0.03 ± 0.01 From μ captured on Al Cosmic ray induced 0.025 ± 0.025 Assumes 10-4 inefficiency μ decay in flight 0.01 ± 0.005 With e- scatter in target Total 0.17 ± 0.12 -17 Rμ = 6 × 10 gives ~ 3 events David Brown, Lawrence Berkeley National Lab 19 mu2e conversion at FNAL PANIC 2011 Mu2e Project Status Mu2e received mission-need approval (CD0) • from DOE in November 2009 Detector Design Solenoid Design Solenoid Fabrication Detector Hall Construction Detector Construction David Brown, Lawrence Berkeley National Lab 20 mu2e conversion at FNAL PANIC 2011 Conclusions • CLFV provides a complementary way to search for New Physics compared to LHC • Sensitive to mass scales >> 1TeV • Mu2e is a proposed experiment to search for CLFV muon decays • A unique design provides high sensitivity • 104 improvement relative to previous searches • Mu2e has preliminary FNAL and DOE approval • Conceptual design (almost) complete • Major component fabrication to begin in 2013 • First data in 2018 David Brown, Lawrence Berkeley National Lab 21 mu2e conversion at FNAL PANIC 2011 Backup David Brown, Lawrence Berkeley National Lab 22 mu2e conversion at FNAL PANIC 2011 Constraints on new physics David Brown, Lawrence Berkeley National Lab 23 mu2e conversion at FNAL PANIC 2011 Constraints on new physics L. Calibbi, A. Faccia, A. Masiero, S. Vempati hep-ph/0605139 Neutrino-Matrix Like (PMNS) Minimal Flavor Violation (CKM) Current limits Can distinguish between PMNS and MFV Mu2e Complementarity between Lepton Flavor Violation (LFV) and LHC experiments David Brown, Lawrence Berkeley National Lab 24 mu2e conversion at FNAL PANIC 2011 CLFV and Tau Decays τ processes suppressed, but less than µ Smaler hep-ph/9810484 GIM -40 Cancellations -14 SM ~ 10 because of SM ~ 10 Phys.Rev.D16:1444,1977 Lee, Shrock large τ mass Good News: Bad News: Pham, Beyond SM rates are τ’s hard to produce: several orders of ~1010 τ/yr vs ~1011 µ/sec magnitude larger than in fixed-target in associated muon experiments (Mu2e/ decays COMET) 33 25 also e→τ at electron-ion collider? M. Gonderinger, M. Ramsey-Musolf, arXiv:1006.5063v1 David Brown, Lawrence Berkeley National Lab mu2e conversion at FNAL PANIC 2011 Extinction momentum scrapeing when beam is ‘wide’ |dE/E| = xmax/D David Brown, Lawrence Berkeley National Lab 4426 mu2e conversion at FNAL PANIC 2011 Mu2e and Project X • Project X: high intensity proton source to replace existing Booster. • Booster: 20 kW beam power at 8 GeV. • Project X: 200 kW at 8 GeV (with upgrade path to 2000 kW). • Sensitivity of Rμe < 10-18 Requires detector, beamline • upgrades David Brown, Lawrence Berkeley National Lab 27 mu2e conversion at FNAL PANIC 2011 Choice of Stopping Material rate normalized to Al • Physics reach sensitive to target Z • μ- lifetime, e- momentum also affected Kitano, et al., PRD 66, 096002 (2002) Z David Brown, Lawrence Berkeley National Lab 4128 mu2e conversion at FNAL PANIC 2011.
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