Mu2e Jason Bono on behalf of the Mu2e Collaboration Fermilab Users’ Meeting June 16, 2016
PREFACE Mu2e ▸ Mu2e will search for µN → eN with unprecedented sensitivity, 𝓟 (10 -17 ) ▸ µ → e conversion is Charged Lepton Flavor Violating (CLFV) Reaction ▸ The SM rate (from neutrino mixing) is unobservably small, 𝓟 (10 -52 ) ▸ An observation is unambiguously New Physics ▸ Mu2e is sensitive to BSM phenomena on mass scales up to 10,000 TeV! 2 Jason Bono, Rice University
PREFACE CLFV ▸ Despite nearly eight decades of searching, no one has ever observed CLFV ▸ Why search again? 3 Jason Bono, Rice University
PREFACE Why Search Again? ▸ Leading New Physics models predict rates for µN → eN conversion to be within Mu2e’s discovery sensitivity but out of reach of all previous experiments! ▸ The Mu2e measurement, with its revolutionary sensitivity, will strongly constrain theory, regardless of the outcome 4 Jason Bono, Rice University
SCOPE We will cover ▸ What will be measured ▸ Design aspects of Mu2e ▸ Mu2e sensitivity & physics reach 5 Jason Bono, Rice University
WHAT IS MEASURED? The basic idea ▸ Produce 10 18 muonic 27 Al atoms ▸ Overlap of muon and Al wave function ▸ Count “conversion electrons” with tracking and calorimetry ▸ Mono-energetic electrons emanating from the Al target ▸ E e = m µ c 2 - E b - E recoil = 104.96 MeV ▸ Suppress background Signal 6 Jason Bono, Rice University
WHAT IS MEASURED? What else will muonic Al do? Conversion < 10 -12 7 Jason Bono, Rice University
WHAT IS MEASURED? What else will muonic Al do? Nuclear Capture ~ 61% Decay In Orbit (DIO) ~ 39% Conversion < 10 -12 8 Jason Bono, Rice University
WHAT IS MEASURED? What else will muonic Al do? Nuclear Capture ~ 61% Decay In Orbit (DIO) ~ 39% Normalization Factor Dominant Background Conversion < 10 -12 Signal 9 Jason Bono, Rice University
WHAT IS MEASURED? Muon to electron conversion rate: R µe R µe = Γ ( µ − +( A,Z ) → e − +( A,Z )) Γ ( µ − +( A,Z ) → ν µ +( A,Z − 1) Numerator: # of conversions Denominator: # of nuclear captures 10 Jason Bono, Rice University
SCOPE We will cover ▸ What will be measured ▸ Design aspects of Mu2e ▸ Mu2e sensitivity & physics reach 11 Jason Bono, Rice University
MU2E DESIGN Mu2e consists of 3 solenoids Transport Solenoid Production Detector Solenoid Solenoid About 25 meters end-to-end 12 Jason Bono, Rice University
MU2E DESIGN Graded field 2.5 T Transport Bz = 4.6 T 1.0 T Solenoid 2.0 T Production Detector Solenoid Solenoid 13 Jason Bono, Rice University
MU2E DESIGN Enter the Production Solenoid 8 GeV Protons Transport Solenoid Production Detector Solenoid Solenoid 14 Jason Bono, Rice University
MU2E DESIGN Enter the Production Solenoid Tungsten Target Target Shielding Reflected Pions (8 kW) Muons & pions exit here to enter the Transport Solenoid Bz = 4.6 T 8 GeV Protons Bz = 2.5 T 15 Jason Bono, Rice University
MU2E DESIGN Enter the Transport Solenoid Muon Beam Spectrum ‣ S-shaped solenoid eliminates line-of-sight transport of photons and neutrons ‣ Curvature drift and collimators select low momentum negative muons 16 Jason Bono, Rice University
MU2E DESIGN Enter the Detector Solenoid 8 GeV Protons Tracker Transport Al Stopping Target Solenoid Production Detector Calorimeter Solenoid Solenoid After three years of running, 10 18 muons will be stopped! 17 Jason Bono, Rice University
MU2E DESIGN The Tracker ▸ Primary method of detection ▸ ~20000 metalized mylar straw drift tubes transverse to detector solenoid ▸ 15 um wall thickness, filled with drift gas + sense wire ▸ Blind to low momentum background ▸ 180 KeV resolution @ 105 MeV Signal electrons ▸ Ultra low mass & can operate in vacuum Low momentum background ▸ Unprecedented requirements, but essential! electrons 18 Jason Bono, Rice University
MU2E DESIGN Decay in orbit background DIO Electron Energy Spectrum Free Muon Decay Decay-In-Orbit VB DIO tail extends near the muon rest mass & accounts for ~55% of the total background 19 Jason Bono, Rice University
MU2E DESIGN Decay in orbit background 20 Jason Bono, Rice University
MU2E DESIGN The Calorimeter ▸ To distinguish muons from electrons, cross check tracker ▸ ~ 1350 pure Cesium Iodide Crystals within two annular disks (IR = 37 cm, OR = 66 cm) ▸ Blind to low momentum 1/2 wavelength background 21 Jason Bono, Rice University
MU2E DESIGN The Cosmic Ray Veto System ▸ The CRV suppresses the spurious detection of conversion- like particles initiated by cosmic-ray muons ▸ Without the CRV, we would see 1 such event per day! ▸ 99.99% efficiency requirement ▸ 4 layers of extruded polystyrene scintillator counter 22 Jason Bono, Rice University
MU2E DESIGN Total Background 23 Jason Bono, Rice University
SCOPE We will cover ▸ What will be measured ▸ Design aspects of Mu2e ▸ Mu2e sensitivity & physics reach e 𝝂 ? N N 24 Jason Bono, Rice University
PHYSICS REACH Mu2e Sensitivity ▸ Previous experiments rule out R µe > 7 x 10 -13 @ 90%CL ▸ Most New Physics models predict conversion rates of R µe ~ 10 -14 - 10 -16 ▸ If R µe ~ 10 -15 , we’ll will see ~ 40 events! ▸ If R µe = 3x10 -17 , we should see 1 event ▸ Expected background is ~ 0.5 an event ▸ Mu2e will be sensitive to R µe > 6 x 10 -17 @ 90%CL! 25 Jason Bono, Rice University
PHYSICS REACH Mu2e Sensitivity ▸ Previous experiments rule out R µe > 7 x 10 -13 @ 90%CL ▸ Most New Physics models predict conversion rates of R µe ~ 10 -14 - 10 -16 ▸ If R µe ~ 10 -15 , we’ll will see ~ 40 events! ▸ If R µe = 3x10 -17 , we should see 1 event ▸ Expected background is ~ 0.5 an event ▸ Mu2e will be sensitive to R µe > 6 x 10 -17 @ 90%CL! 10,000 times beyond previous experiments 26 Jason Bono, Rice University
PHYSICS REACH Breaking Through the Plateau… And Beyond the SM? 27 Jason Bono, Rice University
PHYSICS REACH Enhanced 𝝂→ e Rates A multitude of models predict R µe ~ 10 -15 or higher If they are right, we will see ~ 40+ conversions! Supersymmetry Heavy neutrinos Two Higgs doublets Compositeness Leptoquarks Anomalous coupling 28 Jason Bono, Rice University Theory Reviews: Y. Kuno, Y. Okada, 2001; M. Raidal et al., 2008; A. de Gouvea, P. Vogel, 2013
PHYSICS REACH What if we see a signal? Mu2e Signal? Yes No Precision Higher sensitivity measurement of R μ e search Measure R μ e for Accelerator different target upgrade material R. Bernstein 29 Jason Bono, Rice University
PHYSICS REACH R μ e in different materials is a powerful model discriminator Cirigliano, V., R. Kitano, Y. Okada, and P. Tuzon (2009), Phys. Rev. D 80, 013002, arXiv:0904.0957 [hep-ph] Pb Al Ti Mu2e Signal? R μ e (Normalized to Al) Yes No Precision Higher sensitivity measurement of R μ e search Measure R μ e for Accelerator different target upgrade material Z 30 Jason Bono, Rice University
PHYSICS REACH What if we don't see a signal? ▸ R μ e < 6 x 10 -17 will strongly Mu2e Signal? constrain models Yes No ▸ Conduct next-generation search Precision Higher sensitivity measurement of R μ e with higher sensitivity search Measure R μ e for Accelerator different target upgrade material 31 Jason Bono, Rice University
PHYSICS REACH A next generation Mu2e experiment is well motivated in all scenarios Mu2e Signal? Yes No Precision Higher sensitivity measurement of R μ e search To read about upgrading the Mu2e experiment, Measure R μ e for Accelerator see arXiv:1307.1168 different target upgrade material Mu2e is a long term project 32 Jason Bono, Rice University
PHYSICS REACH Discovery at LHC? Yes No If LHC sees a signal, Mu2e should see ~ 40 events! Mu2e still has plenty of Mu2e Signal? parameter space in which to make a discovery Yes No Mu2e measured Severely constrain conversion rate NP mechanism constrains NP models Mu2e is a potential discovery experiment, complementary to the LHC 33 Jason Bono, Rice University
SCOPE We have covered ▸ What will be measured ▸ Design aspects of Mu2e ▸ Mu2e sensitivity & physics reach e 𝝂 ? N N 34 Jason Bono, Rice University
R&D Active R&D program, mature design, ready for data collection in 2021 35 Jason Bono, Rice University
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