June 5 2007 INPC 07 Tokyo Measurement of

June 5, 2007 INPC’ 07, Tokyo Measurement of T-violating transverse muon polarization + 0 + in K →p m n decay at Ｊ－ＰＡＲＣ Suguru SHIMIZU Osaka University for the E 06(TREK) collaboration

TREK collaboration l Japan: – – Osaka University National Defense Academy (NDA) Tohoku University KEK l Canada: – – University of Saskatchewan University of British Columbia (UBC) University of Montreal TRIUMF l US: – MIT – University of South Carolina (USC) – Iowa State University (ISU) l Russia: – Institute for Nuclear Research (INR, Russia) l Vietnam: – University of Natural Sciences (UNS, Vietnam)

Transverse muon polarization K+→p 0 m+n decay l T-odd Non-zero PT is a signature of T violation. l 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. l Experiment at KEK(E 246) PT = - 0. 0017 ± 0. 0023(stat) ± 0. 0011(syst) ( |PT | < 0. 0050 : 90% C. L. ) PRD 73, 72005(2006)

Model descriptions of PT l Multi-Higgs doublet (3 Higgs doublet) model (MH) – – l Imx = (m. K 2/m. H 2) Im(g 1 a 1*) | < 544 (m. H/Ge. V)2 from the E 246 limit B→tn. X constraints also Im(g 1 a 1*) but weaker ( <1900 (m. H/Ge. V)2 ) N-EDM and b→sg constraint differently Im(a 1 b 1*) SUSY with s-quark mixing (SUS) – Imx ∝ Im[V 33 H+ V 32 DL* V 31 UR*]/ m. H 2 – m. H ≥ 140 Ge. V from the E 246 limit and no stringent limit from other modes l SUSY with R-parity violation (SUR) – Imxl ~ Im [l 2 i 2(li 12)*], Imxd ~ Im [l’ 21 k(l’ 22 k)*] – No stringent limits from other modes

KEK-PS E 246 experiment • Stopped K+ method • Toroidal Spectrometer and Cs. I(Tl) calorimeter • Measurement of e+ asymmetry in cw/ccw direction side view PT = - 0. 0017 ± 0. 0023(stat) ± 0. 0011(syst) Imx = - 0. 0053 ± 0. 0071(stat) ± 0. 0036(syst) decay end view

New experiment at J-PARC (TREK) l l We aim at a sensitivity of d. PT ~10 -4 (E 246 -d. PT ~10 -3) Reasonable upgrading of the E 246 system Statistical error d. PTstat ≤ 0. 1 d. PTstat (E 246) ~10 -4 with 1) × 30 of beam intensity → rate capability of detectors 2) × 10 of detector acceptance Systematic error d. PTsyst ~ 0. 1 d. PTsyst (E 246) ~10 -4 by 　 1) precise calibration of misalignments using data 2) correction of systematic effects JPARC

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

Upgrade of the E 246 detector for TREK at J-PARC l l l 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 Cs. I(Tl) readout PIN → APD with current amplifier

Active polarimeter Identification of muon stopping point/ decay vertex l Measurement of positron energy Ee+ and angle qe+ l Large positron acceptance of nearly 4 p l Larger analyzing power l Lower BG in positron spectra l Parallel plate stopper with Gap MWPC Number of plates Plate material Plate thickness Plate gap Ave. density m+ stop efficiency 31 Al, Mg or alloy ~ 2 mm ~ 8 mm 0. 24 r. Al ~ 95% Small systematics for L/R positron

Sensitivity estimate of TREK Statistical sensitivity Systematic errors Source d. PT • Net run time 1. 0 × 107 s　 -- one year run • Proton beam intensity 9 m. A on T 1 • K+ beam intensity 3× 106 /s -- 30 times of E 246 • Total number of good Km 3 2. 4× 109 -- detector acceptance: 8 times of E 246 • Total number of fwd/bwd (N) 7. 2× 108 • Sensitivity coefficient 3. 73√N -- Analyzing power: 1. 5 times of E 246 Total ~ 10 -4 JPARC Source d. PT field alignment 　　 < 10 -4 kinematic distortion < 10 -4 polarimeter analysis < 10 -4 Total <10 -4

Summary We aim at a sensitivity of d. PT ~10 -4 for statistical and systematic errors. l New K+ beam line (K 0. 8). l Reasonable upgrading of the E 246 system, (1)active polarimeter, (2)readout of calorimeter, (3)tracking system. l Systematic errors have been carefully checked by MC. New detector components have been tested. Next step is stage-2 approval (stage-1 was already approved).

• backup

Beamline for K+ extraction K 0. 8 ( K 1. 1 -BR) proton Final Focus Single stage DC separator Vertical focuses before and after the separator Horizontal focus just after the second D-magnet Momentum bite Acceptance K+ intensity K/p ratio Beam spot Final focus 800 Me. V/c ± 2. 5% 6. 5 msr % Dp/p 3 × 106 /s >2 1. 04 × 0. 78 cm (FWQM) achromatic

E 246 result AT = (Afwd - Abwd ) / 2 Afwd(bwd) = Ncw - Nccw Ncw + Nccw PT = AT / {a <cosq. T>} a : analyzing power <cosq. T> : attenuation factor Imx = PT / KF KF : kinematic factor PT = - 0. 0017 ± 0. 0023(stat) ± 0. 0011(syst) ( |PT | < 0. 0050 : 90% C. L. ) Imx = - 0. 0053 ± 0. 0071(stat) ± 0. 0036(syst) ( |Imx | <0. 016 : 90% C. L. ) Statistical error dominant PRD 73, 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 〉 Most important issues • Grouping