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Measurement of T-violating transverse muon polarization in K + → p 0 m + n decay at Ｊ－ＰＡＲＣ

June 5, 2007 INPC’07, Tokyo. Measurement of T-violating transverse muon polarization in K + → p 0 m + n decay at Ｊ－ＰＡＲＣ. Suguru SHIMIZU Osaka University for the E06(TREK) collaboration. T. K. RE collaboration. Japan: Osaka University National Defense Academy (NDA)

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Measurement of T-violating transverse muon polarization in K + → p 0 m + n decay at Ｊ－ＰＡＲＣ

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  1. June 5, 2007 INPC’07, Tokyo Measurement of T-violating transverse muon polarization in K+→p0m+n decayat Ｊ－ＰＡＲＣ Suguru SHIMIZU Osaka University for the E06(TREK) collaboration

  2. T K 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)

  3. Transverse muon polarization K+→p0m+ndecay T-odd • Non-zero PTis 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)

  4. Model descriptions of PT • Multi-Higgs doublet (3 Higgs doublet) model (MH) • Imx = (mK2/mH2) Im(g1a1*) • | Im(g1a1*) | < 544 (mH/GeV)2 from the E246 limit • B→tnX constraints also Im(g1a1*) but weaker ( <1900 (mH/GeV)2 ) • N-EDM and b→sg constraint differently Im(a1b1*) • SUSY with s-quark mixing (SUS) • Imx ∝ Im[V33H+V32DL* V31UR*]/ mH2 • mH ≥ 140 GeV from the E246 limitand no stringent limit from other modes • SUSY with R-parity violation (SUR) • Imxl ~ Im [l2i2(li12)*], Imxd ~ Im [l’21k(l’22k)*] • No stringent limits from other modes

  5. KEK-PS E246 experiment decay • Stopped K+ method • Toroidal Spectrometer and CsI(Tl) calorimeter • Measurement of e+ asymmetry in cw/ccw direction side view end view PT = - 0.0017 ± 0.0023(stat) ± 0.0011(syst) Imx = - 0.0053 ± 0.0071(stat) ± 0.0036(syst)

  6. New experiment at J-PARC (TREK) • We aim at a sensitivity of dPT ~10-4 (E246-dPT ~10-3) • Reasonable upgrading of the E246 system • Statistical errordPTstat ≤0.1 dPTstat (E246) ~10-4 with 1) ×30 of beam intensity → rate capability of detectors 2) ×10 ofdetector acceptance Systematic error dPTsyst ~ 0.1 dPTsyst (E246) ~10-4by 1) precise calibration of misalignments using data 2) correction of systematic effects JPARC

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

  8. 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 segmentationMPPCreadout • Charged particle tracking addition ofGEMaround target • CsI(Tl) readout PIN → APDwith current amplifier

  9. Active polarimeter • Identification of muon stopping point/ decay vertex • Measurement of positron energy Ee+ and angle qe+ • Large positron acceptance of nearly 4p • Larger analyzing power • Lower BG in positron spectra • Parallel plate stopper with Gap MWPC Number of plates 31 Plate material Al, Mg or alloy Plate thickness ~ 2 mm Plate gap ~ 8 mm Ave. density 0.24 rAl m+ stop efficiency ~ 95% Small systematics for L/R positron

  10. Sensitivity estimate of TREK Statistical sensitivity Systematic errors Source dPT field alignment < 10-4kinematic distortion < 10-4polarimeter analysis < 10-4 Source dPT • Net run time 1.0 ×107 s -- one year run • Proton beam intensity 9mA on T1 • K+ beam intensity 3×106 /s -- 30 times of E246 • Total number of good Km3 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 Total <10-4 JPARC

  11. Summary • We aim at a sensitivity of dPT ~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 approved).

  12. backup

  13. Beamline for K+ extraction K0.8 ( K1.1-BR) proton Final Focus Single stage DC separator Vertical focuses before and after the separator Horizontal focus just after the second D-magnet Momentum 800 MeV/c Momentum bite ±2.5% Acceptance 6.5 msr % Dp/p K+ intensity 3 ×106 /s K/p ratio > 2 Beam spot 1.04 ×0.78 cm (FWQM) Final focus achromatic

  14. E246 result • AT = (Afwd - Abwd) / 2 • Ncw - Nccw • Afwd(bwd) = • Ncw + Nccw • PT = AT / {a <cosqT>} • a : analyzing power • <cosqT> : 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. ) PRD73, 072005(2006) Statistical error dominant

  15. 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

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