Mu2e: Coherent μ e Conversion Experiment at Fermilab. David Brown, LBNL representing the mu2e collaboration

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1 Mu2e: Coherent μ e Conversion Experiment at Fermilab David Brown, LBNL representing the mu2e collaboration

2 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 2

3 CLFV in µ + e + γ and µ - N e - N Model independent effective CLFV Lagrangian Loops Contact Interactions κ << 1 µ eγ rate ~100X µn en rate κ >> 1 µn en >> µ eγ rate 3

4 Possible Sources of μ e Marciano, Mori, and Roney, Ann. Rev. Nucl. Sci. 58 accessible by µ - N e - N and µ - e - γ accessible by µ - N e - N Many models predict detectable signals for Λ >> 1 TeV 4

5 μ e Conversion μ- + N form muonic atom μ- tightly bound in K shell significant WF overlap with N ~4 fm µ - N e - N 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 ~20 fm μ- e- 5

6 Status of CLFV Searches MEG arxiv:

7 The Mu2e Experiment Experimental Goal: Measure the ratio R μe 90% C.L. sensitivity to R μe > orders of magnitude better than current limits Requires ~ 1018 stopped muons ~ protons on target (2 year 25 KW) Requires negligible (<1) background events Many challenges for beamline and detector design 7

8 Best Previous Measurement SINDRUM-II Prompt Beam Cosmic Induced µ Decay Prompt Background π + N N* N + γ γ + N N + e + e - Rμ(Ti) < 6.1X

The Mu2e Collaboration Boston University Brookhaven National Laboratory University of

City University of New York Duke University Fermilab University of Houston University of

Russia Lawrence Berkeley National Laboratory Los Alamos National Laboratory Northern

Pisa, Pisa, Italy INFN Lecce, Università del Salento, Italy Rice University Syracuse

9 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 Lawrence Berkeley National Laboratory Los Alamos National Laboratory Northern Illinois University/Lewis Northwestern University INFN Frascati INFN Pisa, Università di Pisa, Pisa, Italy INFN Lecce, Università del Salento, Italy Rice University Syracuse University University of Virginia College of William and Mary University of Washington, Seattle ~120 collaborators 9

10 Mu2e at FNAL Mu2e Building New transfer line Protons from Booster Conditioning in Accumulator and Debuncher No intereference with NOVA 10

11 Mu2e Apparatus Proton Beam 2.5 T 2.0 T 5.0 T Proton delivery beamline stopping Text target ~ 20 meters 1.0 T SC solenoids for muon collection, transportation, and analysis Primary (proton) and secondary (muon) targets Active devices: tracker, calorimeter, Cosmic Ray veto 11

12 Muon (pion) production Heavy W, Cu shielding protects SC coil Graded field reflects and focuses low-pz particles 8 GeV Protons delivered offaxis to Au target 12

13 Momentum Selection ʻSʼ bend transports charged particles, blocks line-of-sight neutrals muons ʻDʼ Collimators select low-momentum negative particles 13

14 Muon Stopping and Decay Low Pz e - reflected by graded field Muons stop in thinfilm Al (Ti) targets e - energy measured in crystal calorimeter e - momentum measured by straw tracker (in vacuum) 14

15 Achieving Sensitivity Reduce prompt beam backgrounds Pulsed beam with < 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 σ P/P ~

16 Beam Timing Inter-bunch protons < 10 Muon -10 stopping time 16 ~900 nsec Prompt pions decay rapidly τ = 26 nsec Muons survive to reach the stopping target Stopped muon lifetime on Al ~800 nsec

17 e - Momentum Measurement Tracker has acceptance only for high-p electrons 17

18 Momentum Sensitivity Decay in orbit Long tail due to nuclear recoil Conversion Electron Signal Window Shanker, Phys.Rev D25, 1847 (1982) New calculation by Czarnecki etal agrees within 30% arxiv: v1 18

19 Backgrounds for s Running Source Events Comment Anti-proton capture 0.06 ± 0.06 Radiative π - capture 0.04 ± 0.02 Assumes extinction Beam electrons ± μ decay in orbit 0.03 ± 0.01 From μ captured on Al Cosmic ray induced ± Assumes 10-4 inefficiency μ decay in flight 0.01 ± With e - scatter in target Total 0.17 ± 0.12 Rμ = gives ~ 3 events 19

20 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 20

21 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

22 Backup 22

23 Constraints on new physics 23

Violation (CKM) Current limits Can distinguish between PMNS and MFV

24 Constraints on new physics L. Calibbi, A. Faccia, A. Masiero, S. Vempati hep-ph/ 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 24

10-40 because of SM ~ 10-14 Good News: Beyond SM rates are several orders of

τ mass M. Gonderinger, M. Ramsey-Musolf, arxiv:1006.

25 Lee, Shrock Phys.Rev.D16:1444,1977 CLFV and Tau Decays τ processes suppressed, but less than µ SM ~ because of SM ~ Good News: Beyond SM rates are several orders of magnitude larger than in associated muon decays Smaler GIM Cancellations large τ mass M. Gonderinger, M. Ramsey-Musolf, arxiv: v1 Pham, hep-ph/ Bad News: τ s hard to produce: ~10 10 τ/yr vs ~10 11 µ/sec in fixed-target experiments (Mu2e/ COMET) also e τ at electron-ion collider? 33 25

26 Extinction momentum scrapeing when beam is wide de/e = xmax/d 26 44

27 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 < Requires detector, beamline upgrades 27

28 Choice of Stopping Material Physics reach sensitive to target Z rate normalized to Al μ - lifetime, e - momentum also affected Kitano, et al., PRD 66, (2002) Z 28 41

Experimental Searches for Muon to Electron Conversion

Experimental Searches for Muon to Electron Conversion Yoshitaka Kuno Department of Physics Osaka University May 20th, 2009 FJPPL, EPOCHAL, Tsukuba Outline Overview of Our Proposal to FJPPL Physics Motivation