E246 :Search for T violation in the K+→π0µ+ν Decay
E470 :
Branching ratio measurement ofdirect photon emission in K+ → π+π0γ
J. Imazato
IPNS, KEK
KEK-PS External Review 2004
June 7, 2004

E246 : main experiment
E470 : byproduct experimentE246/E470 collaboration
E246 :Japan

Korea
U.S.A.
Taiwan(1) KEK (2) Univ. of Tsukuba,(3) Tokyo Institute of Technology(4) Univ. of Tokyo (5) Osaka Univ.
(6) Institute for Nuclear Research (RAS)(7) TRIUMF (8) Univ. of British Columbia(9) Univ. of Saskatchewan (10) Univ. of Montreal(11) Yonsei Univ. (12) Korea Univ.
(13) Virginia Polytech Institute (14) Princeton Univ.
(15) National Taiwan Univ.

E470 :(1) (2) (5) (6) (7) (8) (9) (10)RussiaCanada(6) : CsI(Tl) calorimeter(7) : fiber target, chamber gas recycler system(14) : TD circuits

Transverse muon polarization in K+→π0µ+ν
Kµ3 decay form factors andT violation

History of Kµ3 transverse polarization experiments• KL→π−µ+ν• KL→π−µ+ν• KL→π−µ+ν
• K+→π0µ+ν

Bevatron 1967
Argonne1973
BNL-AGS 1980
BNL-AGS 1983

Imξ = -0.02 ±0.08
Imξ = -0.085 ±0.064
Imξ = 0.009 ±0.030
Imξ = -0.016 ±0.025

Feature of K+µ3 PT■

Small standard model contribution––■

SMBigi and Sanda “CP violation” (2000)
PT ~ 10-7

Small FSI spurious effects– Single photon contribution

FSI (example)

Zhitnitskii (1980)
PT < ~ 10-6

– Two photon contribution
Efrosinin et al. PL B493 (2000) 293
PT ~ 4 x 10-6■

High sensitivity to CP violation
beyond the SM– Mult- Higgs doublet model– Leptoquark model– Some Supersymmetric modelsPT ~ 10- 4-10- 3

Three Higgs doublet modelKEK E246 experimentFeatures

Stopped K+ experiment with a SC toroidal spectrometer■ Measurement of all decay kinematics directions– Double ratio measurement with small systematic errors■ An experiment which requested the highest-intensity beam
■Progress

1992-1995 : detector construction
1996-2000 : data taking [ 450 + 180 (extension) shifts ]1999: first result was published with 1/4 of dataImξ = -0.023 ± 0.007(stat) ± 0.003(syst)[M.Abe et al., Phys.Rev.Lett. 83(1999) 4253]

2001-2003 : analysis
May 2004 : A paper submitted for publication with the final result

E246 experimental setup[J.Macdonald et al.; NIM A506 (2003) 60]

End view

Side view

K+→π0µ+νMuon polarimeterOne-sector view

Cross sectiony(cm)Double ratio measurement
fwd and bwd π0 /γCsI barrel768

PT directions

Double ratio measurement

Afwd - Abwd
AT =2
bwd -π0 (γ )fwd -π0 (γ )Two independent analyses■ Two analyses by two teams with their own analysis policy and event selection methods

Comparison of good Kµ3 event e.g. :1998
2γ events
1γ events
A2A11221 k918 k1264 k909 k

2γ—A1•A2A1• A2—A1• A21γ
■ Combination of the two analyses

by resorting of events to 6 data sets

—A1•A2A1• A2—A1• A2

Merits of two analysis method
 Cross check of data quality by A0, decay plane rotation θr and θz andPT

 Comparison of sensitivity by normal asymmetry AN and <cosθT> Check of data quality in e.g. A1 by comparing A1•A2and A1• A2-bar

 Estimate of systematic error by comparing <cosθT> of A1• A 2 from A1 and A2

Analysis of asymmetryKµ3 event selection

fwd events : cosθπ0(γ) > 0.341
bwd events : cosθπ0(γ) < -0.341

e+ time spectrum anlysis
Ncw(ccw) : integration from 20ns to 6 µs
with constant BG subtracted
Asymmetry analysis
AT (y)=[A(y)fwd - A(y)bwd] /2A(y)f (b) =• =2γ; o=1γ

[Ncw(y)-Nccw(y)]f(b)[Ncw(y)+Nccw(y)]f(b)PT (y) =AT (y) / α(y) <cosθT>α(y) = AN(y) / PN⇒

 PT =∫P (y) w (y)dyT Imξ = PT / <PT/Imξ>Experimental data
K+µ3 event selection

e+ time spectrum

TOF analysis

CsI(Tl) analysis : 2γMomentumanalysis

e+ time spectraQuality check of data sets
Null asymmetry check

A0=[(Ncw/Nccw)total -1]/2
total = fwd + bwd

Sensitivity check

AN=(Aleft - Aright)/2
Aleft = [(Ncw/Nccw)left

Aright= [(Ncw/Nccw ) right -1]/2• 6 data sets for each period• Open circles are 2γ events and dots are 1γ events.
Decay plane rotation



PT cut point dependence with unknown bias
Blind analysis



-1]/2

Result
PT = - 0.0017 ± 0.0023(stat) ± 0.0011(syst)( |PT | < 0.0050 : 90% C.L. )Imξ = - 0.0053 ± 0.0071(stat) ± 0.0036(syst)( |Imξ | <0.016 : 90% C.L. )[submitted to a journal]

Systematic errors Σ12 : 12-fold rotational cancellation
 fwd/bwd : π0 forward/backward cancellation

Source of Error

Σ12fwd/bwd

e+ counter r-rotatione+ counter z-rotatione+ counter f-offsete+ counter r-offset
e+ counter z-offsetµ+ counter f-offset
MWPC φ-offset (C4)
CsI misalignment
B offset (ε)
B rotation (δx)
B rotation (δz)
K+ stopping distributionµ+ multiple scattering
Decay plane rotation (θr)
Decay plane rotation (θz)
Kπ2 DIF backgroundK+ DIF background
Analysisxxxooxxoxxx
oxxx
xo-ooooooooooxoxoxox-TotalδPT x 104
0.5
0.2
2.8
<0.1
<0.1
<0.1
2.0
1.6
3.0
0.45.3<3.07.1
1.2
0.7
0.6
< 1.9
3.811.4

Systematics check
Consistency among data

Sector dependence● = 2γ; o =1γ;●=1996-1997; o=1998; ★=1999-2000

Decay plane rotationImξ = -0.0055 ± 0.0073(χ2/d.o.f = 0.78)|θr(fwd)- θr(bwd) | ≤ 4.6|θz(fwd)- θz(bwd) | ≤ 2.6

10-4 rad10-4 radModel implications
Three Higgs doublet model

L = (2√(2)GF)1/2 Σ[αiULKMDDR + βiURMUKDL + γiNLMEER] Hi+ + h.c.
Imξ = Im(α1γ1*)= Im(α1β1*)(mK / mH+)2(v2 /v3)2 (mK / mH+)2

vi : vacuum expectation values

αi, βi, γi : mixing matrix elements

 |Imξ | < 0.016 (90% C.L.) ⇒ Im(α1γ1*) < 544 (at mH=mZ)− ) ⇒ Im(α γ *) < 1900 (at m =m )cf. BR (B→Xτντ
1 1HZ
Neutron EDM in 3HD modeldn ⋲ 4/3 dd ∝ Im(α1β1*)

v2/v3 = mt/mτ

m d / m H2

[R.Garisto and G.Kane, Phys. Rev. D44 (1991)2789 ] |Imξ | < 0.016 (90% C.L.) ⇒ dn < 9 10-27 e cmcf.
dnexp < 6.3 10-26 e cm

E470 : Direct emission in K+ →π+π０γ
 Total branching ratio:

BR(DE) = [ 0.61 ± 0.25(stat) ± 0.19(syst) ] x 10-5
 Partial branching ratio In the region of 55<T! < 90MeV:

Internal Brems.(IB)Direct (DE)IB : Strong suppression due to
ΔI=1/2 rule for K+ →π+π０
DE: Magnetic (M1)chiral anomalous term Electric (E1) ? ⇒ Interferencewith IB
BR(DE) :Important input for Chiral Perturbation
Theory (ChPT) ( determination ofO(p4) terms)
BRChPT(DE)~0.4x10-5BR(DE) = [ 0.32 ± 0.13(stat) ± 0.10(syst) ] x 10-5
No evidence for E1 interference
M.Aliev et al. , Phys. Lett. B554,7 (2003)

Byproduct physics
 K+ →π0e+ν (Ke3) : denial of scalar and tensor couplings,
fS/f+(0)=-0.002 ± 0.026 (stat)±0.014(syst);
fT/f+(0)= -0.01±0.14(stat)±0.09(syst)

Phys.Letters B495, 33 (2000)

 Γ(Kµ3)/Γ(Ke3) ratio : decay form factor f0, q2 dependence λ0, ChPT
λ0 = 0.019 ± 0.005 (stat) ± 0.004 (syst)

Phys. Letters B513, 311 (2001)

 K+→µ+νγ : T violation by transverse polarizarion PT
PT = -0.0064 ± 0.0185 (stat) ± 0.0010 (syst)
PT = -0.0067 ± 0.0143 (stat) ± 0.0014 (syst)

Phys. Letters B561, 166 (2003)

 K+→π+π0π0 : form factors ; g and k parameters
g = 0.518 ± 0.039 , k= 0.043 ± 0.020

Eur.Phys.J. C12,627 (2000)

 K+→π0π0e+ν : form factors, ππ scattering length (methodology)
a00 = 0.45 ± 0.43

submitted to Phys.Rev. D

Doctor theses
Precise Measurement of K+→ π0 e+ν Form Factors using Stopped K+;
Tokyo Institute of Technology, 1997.
2) Y. Igarashi;
Measurement of the form factors in K+→π0µ+ν decay;
University of Tsukuba, 1997.
3) T. Ikeda;
Measurement of Muon In-Plane Polarization in the Decay of Κ+→ π0µ+ν;University of Tsukuba, 1998.
4) T. Yokoi;
Search for T-violating Muon Polarization in Κ+→ π0µ+ν decay;
University of Tokyo, 1998.
5) C. Mindas;
Search for T Violation in the Κ+→π0µ+ν decay;
Princeton University, 1998.
6) H.C. Huang;
Search for T-violating Muon Polarization in K+→γ µ+ν Decay;
National Taiwan University, 1998.
7) Y.H. Shin;
Kinematically Complete Measurement of K+→ π+π0π0 Decays;
Yonsei University, 1998.
8) A.P. Ivashkin; Search for T violation in the Κ+→ π0µ+ν decay using a CsI(Tl) calorimeter asa neutral pion detector (in Russian); INR, Russian Academy of Sciences, 1998.
9) T. Baker;
Measurement of scattering length using Kπ3 decay;
University of Saskatchewan, 1999.
10) O. Mineev;
Development and design of analogue electronics and trigger system inthe experiment to measure T-violating muon polarization in positive kaon decays(in Russian); INR, Russian Academy of Sciences, 2000.
11) K. Horie;
Measurement of Γ(Kµ3)/Γ(Ke3) ratio using stopped positive kaons;
Osaka University, 2002.
12) M. Khabibullin; Measurement of T-violating muon polarization in the decay of positive kaonsand limits on the parameters of non-standard models of CP violation (in Russian);
INR, Russian Academy of Sciences, 2003.
1)

S. Shimizu;

Future plan T-violation experiment of new generation at J-PARC
LoI-19 :“PT measurements in K+→π0µ+ν and K+→µ+νγ
with the accuracy of δPT <10-4 and δPT ~10-4 ”
Theoretical importance: [ M.Kobayashi, T.-T.Lin and Y.Okada;
Prog.Theor.Phys. 95, 361 (1995)]

 Development of a stopped K+ beam of high quality

at J-PARC in Phase 1: K0.8 channel with 2 DCS’s
 Detailed design of experiment : ⇒ Full Proposal(this year)(next year) Possibility of detector development at IHEP( Protvino)
now under consideration
1) Prototype detector2) Development of a stopped K+ beam at the 70-GeV PSA new detector with a highresolution photon detection

Summary■ The final result of the KEK-E246 experiment showed no evidence forT violation with Imξ = - 0.0055 ± 0.0073(stat) ± 0.0036(syst) , or|Imξ | <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 PT experiment at the highintensity accelerator J-PARC.
■ A few comments on the PS performance from our experiment:

 E246 was an extraction-efficiency-limited experiment.
(The maximum extraction beam intensity of 2.7~2.8
1012 /spill
was determined by the extraction loss of more than 1012 /spill.) The E246 data would have been more valuable statistically as well as
qualitatively, if we were always provided with a flat-spill beam.