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Lepton Flavor Violation and Dipole Moments in the Muon System at High Intensity Beams

Lepton Flavor Violation and Dipole Moments in the Muon System at High Intensity Beams. Marco Incagli - INFN Pisa SPSC meeting - Villars - 27 sep 2004. Precision Physics as complementary to Frontier Energy Physics Precision Measurement relevant if:

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Lepton Flavor Violation and Dipole Moments in the Muon System at High Intensity Beams

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  1. Lepton Flavor Violation and Dipole Moments in the Muon System at High Intensity Beams Marco Incagli - INFN Pisa SPSC meeting - Villars - 27 sep 2004

  2. Precision Physics as complementary to Frontier Energy Physics • Precision Measurement relevant if: • firm predictions (eventually null) from Standard Model • relevant informations on Standard Model or on Standard Model extensions can be extracted • experimentally accessible • (relatively) low cost • Muons satisfy all requirements! M. Incagli - INFN Pisa Villars SPSC meeting 22-28 sep 2004

  3. Physics motivations: LFV • Lepton flavor violation processes (LFV),like meg , meee , me conversion , are negligibly small in the extended Standard Model (SM) with massive Dirac neutrinos (BR  10-50) • Super-Symmetric extensions of the SM (SUSY-GUTs) with right handed neutrinos and see-saw mechanismmay produce LFV processes at significant rates m-LFVdecays are therefore a clean (no SM contaminated) indication of New Physics and they are accessible experimentally M. Incagli - INFN Pisa Villars SPSC meeting 22-28 sep 2004

  4. Physics motivations : m moments • Magnetic Dipole Moment (g-2) : • measured and predicted with very high accuracy (10 ppb in electron; 0.5 ppm in muon), it represents the most precise test of QED ; • most extensions of SM predict a contribution to g-2 ; • a 2.7 s discrepancy between theory and experiment has raised a lot of interest (and publications) . • Electric Dipole Moment (mEDM) : • Like LFV processes, a positive measurement ofm Electric Dipole Moment (mEDM) would be a signal of physics beyond the SM Both experiments need a new high intensity muon source for the next generation of measurements M. Incagli - INFN Pisa Villars SPSC meeting 22-28 sep 2004

  5. Connection between LFV and m-moments • In SUSY, g-2 and EDM probe the diagonal elements of the slepton mixing matrix, while the LFV decay meprobes the off-diagonal terms • In case SUSY particles are observed at LHC, measurements of the LFV decays and of the m-moments will provide one of the cleanest measarements of tanb and of the new CP violating phase . M. Incagli - INFN Pisa Villars SPSC meeting 22-28 sep 2004

  6. The Anomalous Magnetic Moment : am QED Schwinger 1948 (Nobel price 1965) QED Prediction: Computed up to 4th order [Kinoshita et al.] (5th order estimated [Mohr, Taylor])    Kinoshita-Nio, hep-ph/0402206 corrected feb 04 QED Hadronic Weak SUSY... ... or other new physics ? shad LBL M. Incagli - INFN Pisa Villars SPSC meeting 22-28 sep 2004

  7. Storage ring to measure am polarized Precession of spin and momentum vectors in E, B fields (in the hyp. bB=0) : Electric field used for focusing (electrostatic quadrupoles) B (out of plane) E • At gmagic= 29.3, corresponding to Em=3.09 GeV, K=0 and precession is directely proportional to am M. Incagli - INFN Pisa Villars SPSC meeting 22-28 sep 2004

  8. Muon anomaly (from Hoecker’s presentation at ICHEP04 - Beijing) Including CMD2 and KLOEe+e- results Melnikov-Vainshtein, hep-ph/0312226 a SM[e+e–] = (11 659 182.8 ±6.3had±3.5LBL±0.3QED+EW)  10 –10 BNL E821 (2004) : aexp = (11 659 208.0  5.8) 1010 Observed Difference with Experiment: not yet published not yet published preliminary m+ and m- data combined together (CPT) M. Incagli - INFN Pisa Villars SPSC meeting 22-28 sep 2004

  9. Possible new physics contribution… • New physics contribution can affect am through the muon coupling to new particles • In particular SUSY can easily predict values which contribute to am at the 1ppm level • t data can be affected differently than e+e- data by this new physics • In particular H- exchange is at the same scale as W- exchange, while m(H0)>>m(r) Marciano + others     W- H- M. Incagli - INFN Pisa Villars SPSC meeting 22-28 sep 2004

  10. LoI to J-PARC • An experiment with sensitivity of 0.05 ppm proposed at J-PARC • At the moment, the project is scheduled for Phase2 (>2011) • Together with the experiment there must be an improvement on: • evaluation of LBL • experimetal data on s(had) to cover m(p)<s<m(r) and 1<s<2 GeV M. Incagli - INFN Pisa Villars SPSC meeting 22-28 sep 2004

  11. New proposal - statistics • The new experiment aims to a precision of 0.1-0.05 ppm, which needs a factor of 25-100 more muons • This can be achieved by increasing the … • … number of primary protons on target target must be redisigned • … number of bunches • … muon injection efficiency which, at E821, was 7% • … running time (it was 7months with m- at BNL) • The J-PARC proposal is mostly working on items 2 (go from 12  90 bunches) and 3 M. Incagli - INFN Pisa Villars SPSC meeting 22-28 sep 2004

  12. Intermediate step on g-2 … • As intermediate step between now ( 0.6 ppm) and a future storage ring ( 0.05) a proposal of upgrading E821, in order to reach  0.2 ppm, has been submitted to BNL in July 2004 and defended Sep 9  positive response from PAC M. Incagli - INFN Pisa Villars SPSC meeting 22-28 sep 2004

  13. Electric Dipole Moment (EDM) • The electromagnetic interaction Hamiltonian of a particle with both magnetic andelectric dipole momentis: g-2 term • The existence of dE, in SM, is suppressed because • dEviolates both P and T (and also CP in the CPT hyp.) • only one weak phase exist in CKM • This is not the case for SUSY where many CP phases exist M. Incagli - INFN Pisa Villars SPSC meeting 22-28 sep 2004

  14. Limits on EDM unit conversion • Up to now EDMs have been measured only on: • Neutrons • Heavy paramagnetic/diamagnetic atoms/molecules (Tl,Hg,YbF) • Electron EDM extracted from (2.) : dE(e)<210-27 ecm • New idea to measure directly the EDM on an elementary particle : muons in storage ring • What value for mEDM if new physics exists in am at 1ppm? This New Physics would induce a mEDM : dmNP amNP tanfCP10-13e  cm tanfCP10-22e  cm • With new technique expected sensitivity isdm  10-24e  cm M. Incagli - INFN Pisa Villars SPSC meeting 22-28 sep 2004

  15. New approach to mEDM • Muons in storage ring: combination of g, E, B that cancels out muon spin (g-2) precession(electric field E must be radial and Eb=Bb=0) ; only mEDM precession left . - precession due to am - precession due to mEDM NO out of plane precession side view M. Incagli - INFN Pisa Villars SPSC meeting 22-28 sep 2004

  16. Muon ring for mEDM measurement LOI to J-PARC with following parameters: P = 500 MeV/c Bz = 0.25 T Er = 2MV/m R = 7m <R>= 11m B+E = 2.6 m Intervals = 1.7 m n. elements = 16 circunference 40m Required statistics: NmP2 = 1016 P = Beam Polarization • Optimal momentum choice : pm 300-500 MeV • Below 300 MeV the muon polarization becomes a concern • Above 500 MeV the radial electric field needed to cancel out g-2 precession is >20kV/cm M. Incagli - INFN Pisa Villars SPSC meeting 22-28 sep 2004

  17. Systematics • Basic idea to fight systematics: compare clockwise vs counter-clockwise results • Needs 2 injection points and possibility of changing polarity of dipole magnets (not necessary for quadrupoles) 0 due to choice of b,B,E cw  ccw b -b B -B E E Opposite sign Same sign M. Incagli - INFN Pisa Villars SPSC meeting 22-28 sep 2004

  18. Summary on m-moments • Both g-2 and mEDM are sensitive to new physics beyond the SM(maybe behind the corner) • Unique opportunity of studying phases of mixing matrix for SUSY particles • mEDM first direct probe of dE on elementary particle • The experiments are hard but, in particular the mEDM, not impossible • A large flux of polarized muons of energy 3 GeV (g-2) or 500 MeV (mEDM) is required M. Incagli - INFN Pisa Villars SPSC meeting 22-28 sep 2004

  19. Lepton Flavor Violation m decays • Three relevant processes : e3eNeN • Model Indipendent Interactions: • Relative strength depends upon arbitrary parameters L, LF • In the hyp. L/LF<<1, as in large class of SUSY-GUT theories: BR(m-e conv) 10-3BR(meg) BR(m3e)10-2BR(meg) e.g. : slepton mixing matrix Dipole Transition Direct violation M. Incagli - INFN Pisa Villars SPSC meeting 22-28 sep 2004

  20. +e+ background signal eg accidental en n egn n ee  g g eZ  eZ g e+ +g e+ +g correlated egn n n n n n e+ + qeg = 180° Ee= Eg=52.8MeV Te = Tg g M. Incagli - INFN Pisa Villars SPSC meeting 22-28 sep 2004

  21. +e+ : present Present limit B(me ) < 1.2x10-11by the MEGA Collab.M.L.Brooks et al. Phys.Rev.Lett. 83(1999)1521 Revised document now • New approved experiment: MEG @ PSI • Stopped beam of >107 /sec in a 150 mm target • Liquid Xenon calorimeter for  detection (scintillation) • Solenoid spectrometer & drift chambers fore+ momentum • Scintillation counters for e+ timing LoI Proposal Planning R & D Assembly Data Taking 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 M. Incagli - INFN Pisa Villars SPSC meeting 22-28 sep 2004

  22. +e+ : future • MEG sensitivity : 10-13 with 107+/s • The PSI E5 can deliver up to 3x108+/s • The MEG sensitivity is accidental background limited • With better detector resolutions a BR of 10-14 would be possible but... Challenging ! No immediate (next 10 years) need for a more intense beam M. Incagli - INFN Pisa Villars SPSC meeting 22-28 sep 2004

  23. +e+e+e- e+ n e+ + e- n n e+ e+ + e+ + e+ n e- n e+ e- n e- + background signal eee accidental en n en n e+e-e+e- correlated e e e n n Coplanarity Vertexing Ee= m Te+ = Te+ = Te- M. Incagli - INFN Pisa Villars SPSC meeting 22-28 sep 2004

  24. +e+e+e- : SINDRUM I Present limit B(m3e ) < 1x10-12U.Bellgardt et al. Nucl.Phys. B299(1985)1 No other experimental proposal SINDRUM I parameters • beam intensity 6x106m+/s • m+ momentum 25 MeV/c • magnetic field 0.33T • acceptance 24% • momentum resolution 10% FWHM • vertex resolution  2 mm2 FWHM • timing resolution  ns • target length 220 mm • target density 11 mg/cm2 M. Incagli - INFN Pisa Villars SPSC meeting 22-28 sep 2004

  25. +e+e+e- : summary • A new experiment should aim at a sensitivity of 10-15, which means to increase beam intensity by 103 • Technically not impossible, but uncorrelated background scales quadratically with the beam intensity, therefore six orders of magnitude of background reduction, wrt to SINDRUM I, is required • four orders of magnitude could be achieved … more? Challenging ! No immediate (next 10 years) need for a more intense beam M. Incagli - INFN Pisa Villars SPSC meeting 22-28 sep 2004

  26. -e- conversion (A,Z) e- -g n g (A,Z) - e- - n (A,Z) background signal  (A,Z)e (A,Z) RPC  (A,Z)(A,Z-1) MIO (A,Z)en n (A,Z) Ee= mm- EB M. Incagli - INFN Pisa Villars SPSC meeting 22-28 sep 2004

  27. -e- : present Present limit B(me:Au ) < 8x10-13 SINDRUM II COLLABORATION SINDRUM II parameters • beam intensity 3x107m-/s • m- momentum 53 MeV/c • magnetic field 0.33T • acceptance 7% • momentum res. 2% FWHM Main background : Radiative Pion Capture (RPC)  suppressed with an 8mm carbon absorber at the entrance of the solenoid M. Incagli - INFN Pisa Villars SPSC meeting 22-28 sep 2004

  28. -e- : future • Differently from other channels, this one is not limited by accidentals but by RPC • Two techinques to improve beam purity proposed for two next generation experiments: • New approved experiment at BNL: MECO (E940)BR(me) < 10-16 (2008 ??) • New project LOI to J-PARC: PRISM/PRIMEBR(me) < 10-18 (>2008 ??? ) M. Incagli - INFN Pisa Villars SPSC meeting 22-28 sep 2004

  29. -e- : beam line for MECO • New AGS beam structure: • 21013 protons/bucket (71012 for g-2 experiment) • Short pulses of 30nsec with 1.35 µsec separation between pulses (2 per rotation) • Extinction between pulses must be>109; fast kicker in transport will divert beam from production solenoid Pulsed beam from AGS to eliminate prompt background M. Incagli - INFN Pisa Villars SPSC meeting 22-28 sep 2004

  30. -e- : MECO detector Straw Tracker Muon Stopping Target Superconducting Transport Solenoid (2.5 T – 2.1 T) Crystal Calorimeter 2 x 1013 incident p/sec 1 x 1011 stopping µ/sec Superconducting Detector Solenoid (2.0 T – 1.0 T) Superconducting Production Solenoid (5.0 T – 2.5 T) ~ 5 signal events for 107 s (2800 hours) running if Rme = 10-16 ~ 0.45 expected bckg eventsif extinction factor = 10-9 M. Incagli - INFN Pisa Villars SPSC meeting 22-28 sep 2004

  31. -e- : PRISM beam • PRISM (Phase Rotated Intense Slow Muon source): • Pion capture section • Decay section • Phase rotation section • Ejection system • Machine parameters • Intensity: 1011-1012m/sec • Muon momentum : 68 MeV • Momentum spread :  0.5-1.0 MeV • Beam repetition : 100 Hz M. Incagli - INFN Pisa Villars SPSC meeting 22-28 sep 2004

  32. -e- : PRIME detector M. Incagli - INFN Pisa Villars SPSC meeting 22-28 sep 2004

  33. -e- : summary • This channel will definitely benefit from an increase in beam intensity BUT • The problem of pion contamination of the muon beam is the fundamental issue • Two proposals : • Beam extinction at <10-9 level (!) - BNL • New kind of muon extraction technique with circular (compact) FFAG - PRISM Very promising channel ! M. Incagli - INFN Pisa Villars SPSC meeting 22-28 sep 2004

  34. mEDM and me conversion with “same” beam? • In mEDM LOI to J-PARC the possibility of accomodating mEDM and me in the same hall is prospected • The FFAG system must be projected with the possibility of providing muons both of 80 and of 400 MeV me detector PRISM FFAG mEDM ring M. Incagli - INFN Pisa Villars SPSC meeting 22-28 sep 2004

  35. Summary table and Conclusions • Muons have historically played a key role in understanding the structure of the Standard Model (V-A, QED tests, …) • Muons are fundamental tools to discover and/or to understand the structure of any physics beyond the SM • All future projects (J-PARC, Fermilab) foresee high intensity flux of muons to be used in a storage ring and/or LFV exp. • me transitions and mEDM (also g-2) seem very promising • Europe (CERN) should not loose this opportunity and aim for a leading role in the field of m decays and m moments M. Incagli - INFN Pisa Villars SPSC meeting 22-28 sep 2004

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