Measurement of T-violating transverse muon polarization

in K+→ decay at Ｊ－ＰＡＲＣ

Suguru SHIMIZU

Osaka University

for the E06(TREK) collaboration

June 5, 2007INPC’07, Tokyo

RE collaboration

Japan:– Osaka University– National Defense Academy (NDA)– Tohoku University– KEK

Canada:– University of Saskatchewan – University of British Columbia (UBC)– University of Montreal– TRIUMF

US:– MIT– University of South Carolina (USC)– Iowa State University (ISU)

Russia:– Institute for Nuclear Research (INR, Russia)

Vietnam:– University of Natural Sciences (UNS, Vietnam)

T K

Transverse muon polarization

Non-zero PT is a signature of T violation.

Standard model contribution is very small(10-7). Spurious effect from final state interaction is also small(10-5). Therefore, PT is sensitive to physics beyond the Standard Model.

Experiment at KEK(E246) PT = 0.0017 ± 0.0023(stat) ± 0.0011(syst) ( |PT | < 0.0050 : 90% C.L. ) PRD73, 72005(2006)

K+→decay

T-odd

Model descriptions of PT Multi-Higgs doublet (3 Higgs doublet) model (MH)

– Im = (mK2/mH

2) Im(11*)

– | Im(11*) | < 544 (mH/GeV)2 from the E246 limit

– B→X constraints also Im(11*) but weaker ( <1900 (mH/GeV)2 )

– N-EDM and b→s constraint differently Im(11*)

SUSY with s-quark mixing (SUS)– Im ∝ Im[V33

H+ V32DL* V31

UR*]/ mH2

– mH ≥ 140 GeV from the E246 limit and no stringent limit from other modes

SUSY with R-parity violation (SUR)– Iml ~ Im [2i2(i12)*], Imd ~ Im [’21k(’22k)*]– No stringent limits from other modes

• Stopped K+ method• Toroidal Spectrometer and CsI(Tl) calorimeter• Measurement of e+ asymmetry in cw/ccw direction

side view end view

decay

KEK-PS E246 experiment

PT = 0.0017 ± 0.0023(stat) ± 0.0011(syst)Im= 0.0053 ± 0.0071(stat) ± 0.0036(syst)

New experiment at J-PARC (TREK) We aim at a sensitivity of PT ~10-4 (E246-PT ~10-3) Reasonable upgrading of the E246 system

Statistical errorPT

stat ≤ 0.1 PTstat (E246) ~10-4 with

1) × 30 of beam intensity → rate capability of detectors

2) × 10 of detector acceptance

Systematic errorPT

syst ~ 0.1 PTsyst (E246) ~10-4 by

　 1) precise calibration of misalignments using data 2) correction of systematic effectsJPARC

J-PARC FacilityJ-PARC is now constructed at Tokai, Ibaraki.

Upgrade of the E246 detector for TREK at J-PARC

Muon polarimeter passive → active

Muon magnetic field toroid → muon field magnet

Target smaller and finer segmentation MPPC readout

Charged particle tracking addition of GEM around target

CsI(Tl) readout PIN → APD with current

amplifier

Active polarimeter Identification of muon stopping point/ decay vertex Measurement of positron energy Ee+ and angle e+ Large positron acceptance of nearly 4 Larger analyzing power Lower BG in positron spectraParallel plate stopper with Ga

p MWPC 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 ~ 95%

Small systematics for L/R positron

Sensitivity estimate of TREK

Source PT • Net run time 1.0 ×107 s

　-- one year run

• Proton beam intensity 9A on T1• K+ beam intensity 3×106 /s

-- 30 times of E246• Total number of good K3 2.4×109

-- detector acceptance: 8 times of E246• Total number of fwd/bwd (N) 7.2×108

• Sensitivity coefficient 3.73√N-- Analyzing power: 1.5 times of E246

Total ~ 10-4

Statistical sensitivity Systematic errors

Source PT

field alignment 　　 < 10-4

kinematic distortion < 10-4

polarimeter analysis < 10-

4

Total <10-4

JPARC

Summary

We aim at a sensitivity of PT ~10-4 for statistical and systematic errors.

New K+ beam line (K0.8). Reasonable upgrading of the E246 system,

(1)active polarimeter, (2)readout of calorimeter, (3)tracking system.

Systematic errors have been carefully checked by MC.New detector components have been tested.Next step is stage-2 approval (stage-1 was already appro

ved).

• backup

Beamline for K+ extraction

Momentum 800 MeV/cMomentum bite ±2.5%Acceptance 6.5 msr % p/pK+ intensity 3 ×106 /sK/ ratio > 2Beam spot 1.04 ×0.78 cm (FWQM)Final focus achromatic

K0.8 ( K1.1-BR)

proton

Final Focus

Single stage DC separator

Vertical focuses before and after the separator

Horizontal focus just afterthe second D-magnet

E246 result

PT = 0.0017 ± 0.0023(stat) ± 0.0011(syst) ( |PT | < 0.0050 : 90% C.L. )

Im= 0.0053 ± 0.0071(stat) ± 0.0036(syst)

( |Im| <0.016 : 90% C.L. )Statistical error dominant

AT = (Afwd - Abwd ) / 2

Ncw - NccwAfwd(bwd) = Ncw + Nccw

PT = AT / {<cosT>} : analyzing power <cosT> : attenuation factor Im = PT / KF

KF : kinematic factor

PRD73, 072005(2006)

Status of TREK

• Stage-1 approval in the first PAC meeting in June-July, 2006.

• Now;– Studies of detector upgrade– Polarimeter alignment procedure– Muon field magnet

• Seek for funding• Grouping Most important issues〉