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Result of T-violating Muon Polarization Measurement in the K + → 0 + Decay C. Rangacharyulu Saskatoon, SK for the KEK-E246 collaboration June 7, ‘04 DAPHNE-04 Transverse muon polarization E246 experiment Analysis Result of the total data

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E246 collaboration Japan ● KEK ● Univ. of Tsukuba, ● Tokyo Institute of Technology ● Univ. of Tokyo ● Osaka Univ. Russia ● Institute for Nuclear Research Canada ● TRIUMF ● Univ. of British Columbia ● Univ. of Saskatchewan ● Univ. of Montreal Korea ● Yonsei Univ. ● Korea Univ. U.S.A. ● Virginia Polytech Institute ● Princeton Univ. Taiwan ● National Taiwan Univ.

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Transverse Muon Polarization in K + → 0 + K 3 decay form factors and T violation History of K 3 transverse polarization experiments K L → − + Bevatron 1967 Im = -0.02 ±0.08 K L → − + Argonne 1973 Im = -0.085 ±0.064 K L → − + BNL-AGS 1980 Im = 0.009 ±0.030 K + → 0 + BNL-AGS 1983 Im = -0.016 ±0.025

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KEK E246 experiment ■ Stopped K + experiment with a SC toroidal spectrometer ■ Measurement of all decay kinematics directions –Double ratio measurement with small systematic errors Features History ■ 1992-1995 : detector construction ■ 1996-2000 : data taking ■ 1999 : first result published with 1/4 of data Im = -0.023 ± 0.007(stat) ± 0.003(syst) [M.Abe et al., Phys.Rev.Lett. 83(1999) 4253] ■ 2001-2003 : analysis ■ 2004 (this conference) : report of the final result Byproducts ■ K + → P T = -0.0064 ± 0.0185(stat) ± 0.0010(syst) [V.Anisimovsky et al., Phys.Lett. B562 (2003) 166] ■ e3 e4

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E246 experimental setup End viewSide view [J.Macdonald et al.; NIM A506 (2003) 60] K + → 0 +

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Muon polarimeter Cross section One-sector view y(cm)

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CsI(Tl) and kinematics CsI barrel fwd and bwd 0 / P T directions fwd - bwd - Double ratio measurement

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Experimental data K + 3 event selection e + time spectra CsI(Tl) analysis : TOF analysis Momentum analysis e + time spectrum

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Two independent analyses ■ Two analyses by two teams with their own analysis policy and event selection methods Comparison of good K 3 event e.g. :1998 2 events 1 events A2 1221 k 1264 k A1 918 k 909 k ■ Combination of the two analyses by resorting of events to 6 data sets — A1 A2 A1 A2 A1 A2 — 22 11 Merits of two analysis method Cross check of data quality by A 0, decay plane rotation r and z and P T Comparison of sensitivity by normal asymmetry A N and Check of data quality in e.g. A1 by comparing A1 A2 and A1 A2-bar Estimate of systematic error by comparing of A1 A 2 from A1 and A2 Improvement of statistical error

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Data quality check Null asymmetry check A 0 =[(N cw /N ccw ) total -1]/2 Sensitivity check A N =(A left - A right )/2 A left = [(N cw /N ccw ) left -1]/2 A right = [(N cw /N ccw ) right -1]/2 total = fwd + bwd 6 data sets for each period Open circles are 2 events and dots are 1 events. Null asymmetry is canceled by double ratio ( fwd-bwd ).

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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. )

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Systematics check ● =1996-1997; o=1998; ★ =1999-2000 Im = -0.0053±0.0071 d.o.f ● = 2 ; o =1 ; Consistency among data Sector dependence Decay plane rotation r (fwd)- r (bwd) ≤ 4.6×10 -4 rad z (fwd)- z (bwd) ≤ 2.6×10 -4 rad

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Systematic errors Source of Error 12fwd/bwd P T x 10 4 e + counter r-rotationxo0.5 e + counter z-rotationxo0.2 e + counter f-offsetxo2.8 e + counter r-offsetoo<0.1 e + counter z-offsetoo<0.1 + counter f-offsetxo<0.1 MWPC -offset (C4)xo2.0 CsI misalignmentoo1.6 B offset ( )xo3.0 B rotation ( x )xo0.4 B rotation ( z )xx5.3 K + stopping distributionoo<3.0 + multiple scatteringxx 7.1 Decay plane rotation ( r )xo1.2 Decay plane rotation ( z )xx0.7 K 2 DIF backgroundxo0.6 K + DIF backgroundox< 1.9 Analysis--4.0 Total<11.4 12 : 12-fold rotational cancellation fwd/bwd : 0 forward/backward cancellation

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Model implications L = (2√(2)G F ) 1/2 [ i U L KM D D R + i U R M U KD L + i N L M E E R ] H i + + h.c. Im = Im( 1 1 * ) × ( v 2 / v 3 ) 2 × (m K / m H + ) 2 = Im( 1 1 * ) × (m K / m H + ) 2 v i : vacuum expectation values i, i, i : mixing matrix elements Three Higgs doublet model |Im | < 0.016 (90% C.L.) ⇒ Im( 1 1 * ) < 544 (at m H =m Z ) cf. BR (B→X ) ⇒ Im( 1 1 * ) < 1900 (at m H =m Z ) Neutron EDM in 3HD model d n ≈ 4/3 d d ∝ Im( 1 1 * ) × m d / m H 2 v 2 / v 3 = m t /m [R.Garisto and G.Kane, Phys. Rev. D44 (1991)2789 ] |Im | < 0.016 (90% C.L.) ⇒ d n < 9 × 10 -27 e cm cf. d n exp < 6.3 × 10 -26 e cm −

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Summary ■ Transverse muon polarization in K + → 0 + decay is a good probe of CP violation beyond the standard model. ■ The final result of the KEK-E246 experiment showed no evidence for T violation with Im = - 0.0053± 0.0071(stat) ± 0.0036(syst), or |Im | <0.016 (90% C.L. ). ■ This limit constrains the parameters of some non-standard CP violation models with high sensitivity. ■ We are going to propose a next generation P T experiment at the high intensity accelerator J-PARC.

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