1 fact03 NY June 6 th 2003 Particle physics with intense muon beams A.M. Baldini - INFN Pisa

2 fact03 NY June 6 th 2003 Layout of this talk 1.Precise measurements of muon lifetime (G F ) 2.High precision experiments mesuring the carachteristics of the normal muon decay 3.(C)LFV experiments (muon rare decays mainly) 4.g-2 and EDM Do these experiments benefit by an increase of the muon intensity ? Statistics vs systematics J. Aysto et al., CERN-TH/

3 fact03 NY June 6 th Measurements of muon lifetime (G F ) G F is one of the three parameters of the bosonic sector of the standard model  (0,045 ppm), M Z (23 ppm), G F (9 ppm) The accuracy is dominated by the knowledge of the muon lifetime (theoretical uncertainty <1ppm) True in pure V-A Electroweak fits depend on G F M 2 Z

4 fact03 NY June 6 th 2003 Experiments 3 experiments going-on RAL (D. Tomono) Need to depolarize the muons (limited  coverage) Detector segmented (MWPC+scint.) to avoid pile-up Benefits from pulsed structure of the beam (time) But repetition rate too low (50 Hz) -> statistically limited to 10 4 events/s to avoid pile-up In order a 1 ppm accuracy events are needed 50 Hz ->50 KHz

5 fact03 NY June 6 th 2003 muLan (G. Onderwater) at PSI Scintillator tiles + PMTs symmetric detector to reduce polarization effects Beam structure created artificially at PSI 20 muons of the DC beam are used every 10 muon lifetimes events collection This class of experiments could gain an additional order of magnitude by an increase of the muon rate if pile-up and detector timing stability are kept under control

6 fact03 NY June 6 th 2003 FAST at PSI Use of a pion beam After a final beam test this year they will take data in 2004 and might be ready with results for fact04

7 fact03 NY June 6 th TWIST (E614) at TRIUMF (P. Kitching) Precise measurement of the Michel spectrum

8 fact03 NY June 6 th 2003 TWIST setup  is sensitive to right handed W bosons of several hundred GeV: sensitivity better than direct searches (D0) Need of a higly polarized muon beam (surface muon beam) sensitivity limited by systematic effects

9 fact03 NY June 6 th 2003 T-violation experiment at PSI (W. Fetscher)

10 fact03 NY June 6 th 2003 T-violation (2) principle of the measurement

11 fact03 NY June 6 th (C)LFV: History of lepton flavour searches

12 fact03 NY June 6 th 2003  e  : SUGRA indications SUSY SU(5) predictions BR (  e  )   SUSY SO(10) predictions BR SO(10)  100 BR SU(5) R. Barbieri et al., Phys. Lett. B338(1994) 212 R. Barbieri et al., Nucl. Phys. B445(1995) 215 LFV induced by finite slepton mixing through radiative corrections MEG goal Experimental limit combined LEP results favour tan  >10

13 fact03 NY June 6 th 2003 MEG goal Experimental limit Connection with -oscillations J. Hisano, N. Nomura, Phys. Rev. D59 (1999) Additional contribution to slepton mixing from V 21 (the matrix element responsible for solar neutrino deficit) tan(  )=30 tan(  )=1 After SNO After Kamland in the Standard Model !!

14 fact03 NY June 6 th 2003 Signal and background e+ +  e+ +   e  = 180° Ee = E  = 52.8 MeV Te = T  signal   e  background correlated   e  e+ +  e+ +  accidental   e    e  ee   eZ  eZ  e+ + e+ + 

15 fact03 NY June 6 th 2003 Required Performances Exp./LabYear  E e /E e (%)  E  /E  (%)  t e  (ns)  e  (mrad) Stop rate (s -1 ) Duty cyc.(%) BR (90% CL) SIN x x TRIUMF x x LANL x x Crystal Box x 10 5 (6..9)4.9 x MEGA x 10 8 (6..7)1.2 x MEG x x The sensitivity is limited by the by the accidental background The  3  allows BR (  e  )  but needs FWHM Need a DC beam here

16 fact03 NY June 6 th 2003 The MEG experiment at PSI Easy signal selection with  + at rest e +  +  Ee = E  = 52.8 MeV  e  = 180° Detector outline Stopped beam of >10 7  /sec in a 150  m target Liquid Xenon calorimeter for  detection (scintillation) - fast: 4 / 22 / 45 ns - high LY: ~ 0.8 * NaI - short X 0 : 2.77 cm Solenoid spectrometer & drift chambers for e + momentum Scintillation counters for e + timing

17 fact03 NY June 6 th Summary and Time Scale This experiment may provide a clean indication of New Physics Measurements and detector simulation make us confident that we can reach the SES of 4 x to  e  (BR ) Final prototypes will be measured within this year Large Prototype for energy, position and timing resolutions of  s Full scale Drift Chamber  -Transport and degrader-target Financed very recently also in Italy (april)+Switzerland (may) Tentative time profile More details at PlanningR & D Assembly Data Taking now LoIProposalReviseddocument

18 fact03 NY June 6 th 2003 Calculation of B  - e/B  e 

19 fact03 NY June 6 th 2003 Sindrum II setup

20 fact03 NY June 6 th 2003 Sindrum II gold target

21 fact03 NY June 6 th 2003 Beam related background Moderator: range  about ½ range 

22 fact03 NY June 6 th 2003 Sindrum II results  Decay In Orbit 2% FWHM resolution

23 fact03 NY June 6 th 2003 MECO (P. Yamin) 1.Large acceptance pion capture in a SCS 2.Muon transport (60 – 120 MsV/c) in a curved solenoid 3.Long detector solenoid with muon stpping target and tracking system

24 fact03 NY June 6 th 2003 MECO (2)   /s 900 KeV (FWHM) electron resolution, dominated by interactions in the target < extinction between bursts (beam background) Sensitivity to B  % duty cycle

25 fact03 NY June 6 th 2003 PRISM (A. Sato) High intensity pulsed proton beam Pion capture solenoid Pion decay section Phase rotation (muon energy spread reduction) by means of an rf field Very similar to the front end of the proposed neutrino factories

26 fact03 NY June 6 th 2003 MECO (2) Intensity  muons/s Low momentum (68 MeV/c) Narrow energy spread (few % FWHM) The last characteristic is essential to stop enough muons in thin targets. If the electron momentum resolution can be kept below 350 KeV (FWHM) the experiment can be sensitive to  e conversion down to Other LFV processes such as muonium-antimuonium oscillations could be studied with improvements of some order of magnitudes wrt previous limits

27 fact03 NY June 6 th g-2(L. Roberts) a  = (7)(5) x (0.7 ppm) a  for negative muons (CPT test)

28 fact03 NY June 6 th 2003 Muon anomaly vs theory

29 fact03 NY June 6 th 2003  edm (W.Morse) P and T violating Best limit from g-2 CERN experiment: 3.7  3.4 x e. cm Letter of intent (Jan 2003) for a dedicated experiment -> e. cm level Disentangle the EDM effect from the g-2 precession by means of a radial electric field High intensity beam of 0.5 GeV/c polarized muons: new PRISM; PRISMII

30 fact03 NY June 6 th 2003 Illustration of the beam needs for the different kinds of experiments

31 fact03 NY June 6 th 2003 Conclusions Muons are sensitive probes of physics beyond the standard model SUGRA theories need (C)LFV not too far from the existing limits Many of the on going measurements will benefit from an increase of the muon flux In some cases better experiments should be conceived This constitutes a challenge for the field of detectors R&D The effort is worthwhile: new physics could be not so far...