Muon Physics Overview (A Muon Collider Roadmap) William J. Marciano July 23, 2009 Chicago, ILL

OUTLINE 1.Great Muon Expectations 2.Recent Muon Results (PSI) i) Muon Lifetime  G  = (5)x10 -5 GeV -2 S Parameter: New Heavy Chiral Doublets? Extra Dimensions? ii) Muon-H Capture g P =7.7  1.2 (Agrees with  PT) 3.Muon Anomalous Magnetic Moment (BNL E821) a  exp -a  SM =307(63) exp (53) SM x sigma (SUSY?) 4.LFV:  e  PSI ( )  2e Fermilab/JPARC (2x ) 5.Muon Collider(  2TeV)/Neutrino Factory 6.Outlook/Vision

Apologies For Incompleteness Not enough time to discuss TRIUMF (TWIST), Muon Cooling,  -EDM, JPARC plans…

1. Great Muon Expectations Muons are very special:   ≈2.2x10 -6 sec! m  =105.66MeV (   heavy electron,   light proton) Decay:    e  e   (  ) 100%Polarized-P.V. Decay Ang. Dist. Tracks Pol.  SR (condensed matter), Muon g-2 (Garwin et al.) Copious Production: 1p(8GeV)+N    1   Intense Muon Source    /sec possible! (Currently 10 8  + /sec, 10 7  - /sec at PSI) Muon Collider    , Neutrino Factory, Nanoscience…  CF?   DT  He(4MeV)+n(14MeV)+   (10 20 p/s!!)

Muon Collider: Produce   /sec, Collect, Cool, Accelerate, Store, Collide     at  s≥m Z, …2TeV! Challenging! Neutrino Radiation Problem? (Plan B Muon SR-Neutrino Factory  +  e + e   ) Muon Technology Needs To Be Nurtured! (Pursue Fundamental Muon Physics Aggressively!) Build Muon Community

2. Recent Muon Results (PSI) Standard Model Natural Relations: e 0 2 /g 0 2 =sin 2  0 W =1-(m 0 W /m 0 Z ) 2 Radiative Corrections (Loops) Finite & Calculable m t prediction  GeV, m H  160GeV (95%CL)! (Relatively light Higgs suggests Supersymmetry) Deviation  ”New Physics”: SUSY, Technicolor, W*… * MUON LIFETIME PARTICULARLY IMPORTANT  G  eg. G  (1-  r(m Z )  M  S )=  /  2m W 2 sin 2  W (m Z )  M  S  r(m Z ) MS = S + (1)(m W /m W* ) 2 + … S=N D /6 , N D = No. of new heavy doublets eg. (4th generation), 12 (mirror fermions), Technifermions… W* excited W (extra dimensions, compositeness…)

i) Muon (   ) Lifetime MuLAN & FAST experiments at PSI: World Ave.   = (17)x10 -6 sec (Further factor ~10 improvement expected in 2010) Already Confirms (improves) Previous World Average by error/2.   -1 =  (  +  e + e   (  ))=G  2 m  5 f(m e 2 /m  2 )[1+RC]/192  3 RC =  /2  (25/4-  2 )(1+  /  [2/3ln(m  /m e )-3.7)…] Fermi Th. Other SM and “New Physics” radiative corrections absorbed into G . Eg. Top Mass, Higgs Mass, Technicolor, Susy,W*… G  = (5)x10 -5 GeV -2 precise & important

S Parameter Use , G , m W, and sin 2  W (m Z ) MS  S (Counts N D ) & m W* S/120+(m W /m W* ) 2 =[(G  x10 -5 GeV -2 )/ x10 -5 GeV -2 +(  )/ (m W GeV)/80.351GeV +(sin 2  W (m Z ) MS )/ ] X+0.019X 2, X=ln(m H /115GeV) m W =80.398(25)GeV sin 2  W (m Z )  M  S = (16) Ave  S=0.10(11) & M W* >2-3TeV No Sign of “New Physics”!

Precision Parameters (status): Quantity 2006 Value 2009 Value Comment  (96) (51) g e -2 G  (1)x10 -5 GeV (5)x10 -5 GeV -2 PSI m Z (21)GeV (21)GeV - *m t 171.4(2.1)GeV  173.1(1.2)GeV FNAL m W (32)GeV  (25)GeV LEP2/FNAL sin 2  W (m Z ) (16) (16) Ave. sin 2  W (m Z ) (26) (26) A LR sin 2  W (m Z ) (29) (29) A FB (b  b) (3 sigma difference?)

sin 2  W (m Z )  M  S  S S N D Average (16) -0.04(8) +0.10(11) 2(2) A LR (26) -0.32(13) -0.19(15) (SUSY) A FB (b  b) (29) +0.32(15) +0.45(17) 9(3)! If A LR had never been measured: sin 2  W (m Z )  M  S = (20) That would imply S=+0.28(12)  N D ~6  2.4!!) (Heavy Higgs! 4th Generation, m W*  1.6TeV…) We would be waiting for 4th Generation, Technicolor, Extra Dim. We missed our chance to nail sin 2  W (m Z )  M  S at the Z pole! Future sin 2  W (m Z )  M  S Precision: Z Factory?

ii) Hydrogen Muon Capture: Muonic Atom (  - N   N’): =-Z 2  2 m ,    =Z       + (1 + Z 2  2 /2 - Capture BR(~Z 3 /1000))  (capture)=1/   -1/   (after time dilation correction) For N=H, theory clean but high precision lifetimes needed.  n  d   (1-  5 )u  p  =g V (q 2 )  n   p +ig M (q 2 )/2m N  n   q  p -g A (q 2 )  n    5 p-g P (q 2 )q  /m   n  5 p Chiral Pert. Th. Predicts: g P (-0.88m  2 )=8.2  0.2 Exp.(Pre 2007)  g P =11-12(1) Off by 3-4 sigma

Muon-H Capture Result (Including recent update with g A =1.275(1))  (capture)=1/   -1/   (after time dilation correction) For atomic 1S singlet  (  - p   n) exp =725(17)sec -1 MuCap  (  - p   n) SM =717(3)( (g P -8.2)) 2 sec -1 Implies: g P =7.7(1.2) g p  PT  8.2(0.2) Good Agreement! Additional data  further factor 3 improvement Push as far as possible! Improve Theory

3. Muon Anomalous Magnetic Moment Final Experimental Result: E821 at BNL a  exp  (g  -2)/2 = (54) stat (33) sys x = (63)x Factor of 14 improvement over CERN results (Proposing Factor 4 Upgrade at FNAL - Up The Calumet Canal) ) D. Hertzog & B. Lee Roberts Also, JPAC low energy muon R&D

BNL Muon g -2 Experiment

N(t) = N 0 e -t/  [1+Acos(  a t +  )]

Standard Model Prediction a  SM = a  QED +a  EW +a  Hadronic QED Contributions: a  QED =0.5(  /  ) (27)(  /  ) (43)(  /  ) (80)(  /  ) (20)(  /  ) 5 +… (5 loops)  -1 = (51) From a e (new) a  QED = (2)x Very Precise!

Electroweak Loop Effects a  EW (1 loop)=194.8x goal of E821 2 loop EW corrections are large -21% a  EW (2 loop)=-40.7(1.0)(1.8)x loop EW leading logs very small O( ) a  EW =154(2)x Non Controversial Hadronic Contributions (some controversey) e + e -  hadrons vs  hadrons+  (isospin) Novosibirsk, KLOE vs BaBar (e + e -  +  -  )

KEY REGION

From e + e -  hadrons data + dispersion relation a  Had (V.P.) LO =6894(42)(18)x (Hagiwara et al) 3 loop=a  Had (V.P.) NLO +a  Had (LBL) a  Had (V.P.) NLO = -98(1)x a  Had (LBL) = 105(26)x (Consensus) a  Had =6901(42)(18)(26)x a  SM = (2)(46)(26)x10 -11

 a  =a  exp -a  SM =307(63)(53)x (3.7  !) New Physics? Nearly 2xStandard Model! Most Natural Explanation: SUSY Loops Generic 1 loop SUSY Conribution: a  SUSY = (sgn  )130x (100GeV/m susy ) 2 tan  tan  3-40, m susy  GeV Natural Explanation Other Explanations: Hadronic?      +isospin data BaBar e + e -  +  -  rad. return (  a  =~150x (1.9  ) Other New Physics ~ 2TeV eg Extra Dimensions

SUSY 1 loop a  Corrections

SUSY Loops are like EW, but depend on: 2 spin 1/2  - (charginos) 4 spin 1/2  0 (neutralinos) including dark matter! 3 spin 0 sneutrinos and sleptons with mixing Enhancement tan  =  2  /  1  ~3-40 Implications: sgn  0 (dark matter searches easier) SUSY at LHC very likely b  s ,  e , edms… Good Bets

“The deviation in a  could be to Supersymmetry what the anomalous precession of the perihelion of Mercury was for General Relativity” J. Marburger Presidential Science Advisor (Former BNL Director)

“The g  -2 experiment makes me proud to be a physicist ” Bill Foster Local Congressman

4. Charged Lepton Flavor Violation 1947 Muon established as independent elementary lepton: No  e+  implies  not excited electron 1958 Feinberg loop calculation of  e+  B(  e  )<10 -4 ~10 -5 implies second neutrino! 1959 Feinberg and Weinberg Study  - N  e - N Coherent E e  105MeV Very Clean-Distinct Stop  - in material ( sec)   N(1S) atom i)  e  Rate  0.5x10 6 /sec ii)  N   N’  (N=Al)  0.7x10 6 /sec  (N=Ti )  2.6x10 6 /sec grows  Z 4 (very roughly)

iii) R(  N)  (  N  eN)/  (  N   N’)  Z (for low Z) R(  Au)<7x SindrumII at PSI R(  Ti)<7x Unpublished Conversion can take very high rate-No Accidentals Every Muon We Can Produce mu2e would stop  /sec! Needs Clean Beam & Good E e Resolution  +  e + +  Accidentals a problem (for B(  e  )< ) MEG at PSI (DC  Beam) Ongoing Goal 2x  2x (upgrade)

 2e Fermilab/JPARC R(  Al  eAl)  2x ! Coherent  -e Conversion in Nuclei (  N  eN) Stop   in material, ~ sec,   N (1S) atom forms i)  (    e -  ) = 0.5x10 6 /sec ii)  (   N   N’) = 0.7x10 6 /sec (N=Al) = 2.6x10 6 /sec (N=Ti) iii)   N  e - N R(   Ti  e - Ti)<7x (Prelim.) *Signature: m  -BE=105 MeV monoenergetic electron single particle  no accidentals  high rate capability! It can take every muon we can provide! Stop   /sec! wait ~0.6x10 -6 sec (reject prompt background) Requires ~300keV resolution & Clean beam between pulses

Expected signal Cosmic ray background Prompt background Experimental signature is105 MeV e - originating in a thin stopping target. potential sources of fake backgrounds specify much of the design of the beam and experimental apparatus.

Charged Lepton Number Violating Processes Reaction Bound In Progress Proposed Possible BR(  e  )  1.2x x SES 2x SES ? BR(  eee)  1x R(  Ti  eTi)  4x x SES  (7x ) BR(  e  )  7.2x BR(K L  e)  4.7x BR(  )  5.9x BR(  ) <2.0x BR(Z  e) <1.7x10 -6 ( from  Ti  eTi!) (From Marciano, Mori and Roney Annual Reviews)

Straw Tracker Crystal Calorimeter Muon Stopping Target Muon Beam Stop Superconducting Production Solenoid (5.0 T – 2.5 T) Superconducting Detector Solenoid (2.0 T – 1.0 T) Superconducting Transport Solenoid (2.5 T – 2.1 T) Collimators Muon Conversion Experiment

Some Theory Considerations: If transition dipole operator (chiral changing) dominates BR(  e  )=389R(  Al  eAl)=238R(  Ti  eTi) But conversion exp. can be more sensitive by ! Eg. Popular SUSY Models (may be related to  a  ) Neutrino Mass & Mixing Effects  Lepton Flavor Violation BR(  e  )~3  /32  [m 3 2 -m 2 2 ] 2 /m W 4 (s 13 c 13 s 23 ) 2  R(  N  eN)~100BR(  e  )~ still tiny, but enhanced by Chiral conserving amplitudes. (Lesson) Conversion better for Heavy Neutrino Mixing In General: 1/200  BR(  e  )/R(  N  eN)  200 Physics scale ~3000TeV Probed!

Muon g-2 and LFV If SUSY or any other New Physics is responsible for  a , it will also induce LFV via mixing effects. (Chiral Changing) D L,R =16  2  2  a    e /G F m  2   e <4.5x10 -5 Large Slepton Mixing  (M 2 -M 1 )/M 1 <4.5x10 -5 ! Very Near Degeneracy (R Symmetry?) MEG(  e  ) at 2x may see an effect or   e <6x10 -6 !  M 2 -M 1  O(1MeV)

Sensitivity to Different Muon Conversion Mechanisms Compositeness Second Higgs doublet Heavy Z’, Anomalous Z coupling Predictions at Supersymmetry Heavy Neutrinos Leptoquarks

5. Muon Collider(  +  - )/Neutrino Factory i) Need Copious Source of Protons Fast cycling 8-16GeV Accelerator or Linac Power~4MW  >10 14  +  - /sec ii) Collect and Cool  + &  - Beams iii) Accelerate  High Energy iv) Large Storage Ring (~1000 revolutions) v) Luminosity ~ desirable (at 2TeV) Energy: 91GeV Z Factory (sin 2  W, b  b,…) GeV Higgs Pole Resonance(s) 161GeV W + W - (m W ) 350GeV t  t (m t ), HZ… SUSY Pairs  2TeV  +  - “New Physics”,  -  -  p…

Neutrino Factory  SR Intense Muon Beam:  +  e + e   ;  -  e -  e  Leads to clean source of neutrinos Statistics  E 3 Go to 20GeV Very Good  13 e  , but osc length ~500km x E (GeV) Not optimized for CP Violation  Long Distances! Very Good for small  13, New Physics Currently: All Neutrino Data (including MINOS2009) sin 2 2  13 =0.08  0.04 (relatively large!) Fogli et al. Hep-ph (2009)

6. Outlook/Vision PSI Exps. MuLAN, FAST and MuCAP interesting and timely. Expect Improvement in   and g P to continue (2010 results) No definitive sin 2  W (m Z )  M  S in sight (LHC? A FB (Z  )) Perhaps a  exp improvement (x4) at Fermilab (JPARC?) BaBar and Belle doing e+e-  hadrons +  as well as   +hadrons with high statistics. Factor 2 a  (V.P.) improvement? (Novosibirsk factor 3) MEG at PSI: BR(  e  )~2x (running!) (future 2x )  2e at Fermilab/JPARC aim for  Al  eAl with 2x SES! Sensitive to “New Physics” up to 3000TeV (Robust)

If MEG (  e  ) sees several (5) events it will be a major discovery.  2e should then see between ,000 events from  Al  eAl. If MEG sees nothing,  2e could still see 10,000 events!  2e promises to be a flagship experiment. With upgrade eg. (project X) it could be extended to No better way to push muon technology while doing forefront physics!  2e must do experiment (fast track)

LHC Many Discoveries Anticipated: Higgs, SUSY, Extra Dimensions, Z’, Strong Dynamics etc. So far, no evidence for New Physics except perhaps g  -2 (Hope Deviation is Correct) Can Mainland USA get back to Collider HEP?

Project X at Fermilab 2MW proton Linac with 8GeV protons muon, kaon, neutrino physics (motivation) (Upgradeable to 4MW) Front end of a muon collider (Real Motivation?) Z Factory, Higgs,… Neutrino Factory…  p, 2 TeV  +  - Collider at Fermilab The Future of US Collider HEP is the Muon!