1. Measurement of T-violating Transverse Muon Polarization in  + →     Decays at J-PARC Suguru SHIMIZU Osaka University Oct. 6, 2006 SPIN2006

2. Transverse muon polarization Spurious effects from final state interaction are small. Non- zero P T is a signature of T violation. Clear channel to search for T violation. Long history of theoretical and experimental studies. (J.J. Sakurai, 1957) Experiment at KEK(E246) P T =  0.0017 ± 0.0023(stat) ± 0.0011(syst) ( |P T | < 0.0050 : 90% C.L. ) PRD73, 72005(2006) K + →     decay T-odd

3. Matrix element of K + →     decay P T is sensitive to scalar couplings. T-violation parameter : Im(ξ) Im(ξ)≠0 T-violation

4. Beyond the Standard Model Standard Model contribution to P T : –Only from vertex radiative corrections and P T (SM) < 10 -7 Spurious effects from final state interactions (FSI) –Recent elaborate calculation : P T (FSI) < 10 -5 There is a large window for new physics beyond the SM in the region of P T = 10 -3 ~ 10 -5 There are theoretical models which allow sizeable P T without conflicting with other experimental constraints.

5. Model descriptions of P T Multi-Higgs doublet (3 Higgs doublet) model (MH) –Im  = (m K 2 /m H 2 ) Im(  1  1 * ) –| Im(  1  1 * ) | < 544 (m H /GeV) 2 from the E246 limit –B→  X constraints also Im(  1  1 * ) but weaker ( <1900 (m H /GeV) 2 ) –N-EDM and b→s  constraint differently Im(  1  1 * ) SUSY with s-quark mixing (SUS) –Im  ∝ Im[V 33 H+ V 32 DL * V 31 UR *]/ m H 2 –m H ≥ 140 GeV from the E246 limit and no stringent limit from other modes SUSY with R-parity violation (SUR) –Im  l ~ Im [ 2i2 ( i12 ) * ], Im  d ~ Im [ ’ 21k ( ’ 22k ) * ] –No stringent limits from other modes

6. Stopped K + method Large solid angle and high resolution of Toroidal Spectrometer and CsI(Tl) calorimeter side view end view decay T-violation search in KEK E246 experiment

7. Double ratio measurement ＋ P T (π 0 forward) ＝ － P T (π 0 backward) P N contribution to systematic error is drastically reduced. Determination of P T Stopped K + beam B

8. E246 result P T =  0.0017 ± 0.0023(stat) ± 0.0011(syst) ( |P T | < 0.0050 : 90% C.L. ) Im  =  0.0053 ± 0.0071(stat) ± 0.0036(syst) ( |Im  | <0.016 : 90% C.L. ) Statistical error dominant A T = (A fwd - A bwd ) / 2 N cw - N ccw A fwd(bwd) = N cw + N ccw P T = A T / {  }  : analyzing power : attenuation factor Im  = P T / KF KF : kinematic factor PRD73, 072005(2006)

9. New experiment at J-PARC We aim at a sensitivity of  P T ~10 -4 (E246-  P T ~10 -3 )  Statistical error  P T stat ≤ 0.1  P T stat (E246) ~10 -4 with 1) × 30 of beam intensity, 2) × 10 of detector acceptance Systematic error  P T syst ~ 0.1  P T syst (E246) ~10 -4 by 1) precise calibration of misalignments using data 2) correction of systematic effects JPARC

10. Method of experiment Stopped K + decay –Superior to in-flight decay Toroidal spectrometer E246 detector upgrade –Well known performance –Well studied systematics –Good alignment in magnet and CsI(Tl) –Lower cost FoM (A√N) distribution Detector acceptance

11. Upgrade of the detector Muon polarimeter passive → active Muon magnetic field toroid → muon field magnet Target smaller and finer segmentation Charged particle tracking addition of two chambers CsI(Tl) readout PIN diode → APD New analysis scheme

12. Active polarimeter Identification of muon stopping point/ decay vertex Measurement of positron energy E e + and angle  e + Large positron acceptance of nearly 4  Larger analyzing power Higher sensitivity Lower BG in positron spectra Parallel plate stopper with Gap drift chambers Number of plates 31 Plate material Al, Mg or alloy Plate thickness ~ 2 mm Plate gap ~ 8 mm Ave. density 0.24  Al   stop efficiency ~ 85% Small systematics for L/R positron Fit for  0 fwd/bwd measurement

13. Muon field magnet Uniform field of 0.03 T Precise field alignment of 10 -3 Gap : 30 cm Pole face : 60 cm ×40 cm No. of coils : 24 Mag. motive force : 3.6×10 3 A Turn/coil 20 cm

14. Systematic error from B field rotation muon field magnet Active polarimeter   fwd   bwd  P N fwd P N bwd spectrometer Side ViewEnd View P N fwd P N bwd LeftRight LeftRight B π 0 fwd 1+  P N bwd 1   P N fwd/bwd = 1+2  P N ≠1 systematic error Calibration of the polarimeter is very Important. B P T fwd P T bwd π 0 fwd 1+  P T bwd 1   P T fwd/bwd = 1+2  P T

15. Calibration of four misalignments Polarimeter left/right asymmetry measurement using longitudinal pol. P L K + →   (K  2 ) radial polarization P r from K + →     (K  2 )-  + decay in flight PrPr PLPL dangerous A(P L )= (  r   r )cos  t + (  z -  z ) sin  t +  r A(Pr)= (  r   r ) sin  t  (  z -  z ) cos  t +  z Unique determination of  r  z  r  z  with an accuracy of ~10 -4 rr rr zz ZZ

16. MC results: calibration of misalignments  r=(3.7±0.2) x 10 -3  z=(4.0±0.2) x 10 -3  r=(3.9±0.2) x 10 -3  z=(3.7±0.2) x 10 -3 with use of 10 8 muons K  : 1 day collection K  : simultaneous data collection with K  PrPr PLPL 4 rotations L:black R: red

17. Target and tracking Better kinematical resolution Stronger K  2 dif  + BG suppression Addition of C0 and C1 GEM chambers with - high position resolution - higher rate performance Larger C3-C4 distance Use of He bags New target E246J-PARC

18. MC studies of tracking Four chamber tracking including C0 with 0.1mm resolution Suppression of K  2 -dif down to ~1.0% Remaining BG is from the  + decay between the target and C0. Further suppression down to 0.1% level with the fit trajectory consistency with target fibers, and target fiber analysis.  P T (   2 BG) < 10 -4 K3K3 K  2 -dif

19. Beamline for K + extraction Momentum 800 MeV/c Momentum bite ±2.5% Acceptance 6.5 msr %  p/p K + intensity 3 ×10 6 /s K/  ratio > 2 Beam spot 1.04 ×0.78 cm (FWQM) Final focus achromatic K0.8 ( K1.1-BR) K0.8 proton

20. Sensitivity estimate Source  P T Net run time 1.0 ×10 7 s Proton beam intensity 9  A on T1 K + beam intensity 3×10 6 /s Total number of good K  3 2.4×10 9 Total number of fwd/bwd (N) 7.2×10 8 Sensitivity coefficient 3.73√N Total ~ 10 -4 Statistical sensitivitySystematic errors Source  P T  z < 10 -4  z < 10 -4  e +, E e + < 10 -4 Total ~ 10 -4 JPARC

21. Summary P T in K  3 is a very sensitive probe of new physics We propose a J-PARC experiment in the early stage of Phase 1 to pursue a limit of  P T ~ 10 -4. New K0.8 beamline Upgraded E246 detector Stage 1 approval –Upgrade will be finished by 2010. –Data taking will be started from 2011.

22. Collaboration (present group) Canada U.Saskatchewan TRIUMF UBC U. Montreal USA MIT U. South Carolina Iowa State U. Japan KEK Tohoku U. Osaka U. NDA Beamline Target Muon field magnet Active polarimeter CsI(Tl) readout DAQ GEM chambers Tracking upgrade We will organize more people after obtaining an approval.