J-PARC E06 K+→π0μ+ν(Kμ3) を用いた

時間反転非保存探索実験における新型光センサーの活用法

Dec 8, 2006第 2 回次世代光センサーに関するワークショップ

清水俊大阪大学理学研究科

Transverse muon polarization

Spurious effects from final state interaction are small. Non-zero PT is a signature of T violation.

Clear channel to search for T violation. Long history of theoretical and experimental studies. (J.J. Sakurai, 1957)

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

Matrix element of K+→ decay

PT is sensitive to scalar couplings.

T-violation parameter : Im(ξ) Im(ξ)≠0 　 　 T-violation

Theoretical aspects Standard Model contribution to PT :

– Only from vertex radiative corrections and PT(SM) < 10-7

Spurious effects from final state interactions (FSI): PT(FSI) < 10-5

There is a large window for new physics beyond the SM in the region of PT = 10-3 ~ 10-5

There are theoretical models which allow sizeable PT without conflicting with other experimental constraints. Multi-Higgs doublet (3 Higgs doublet) model (MH)

SUSY with s-quark mixing (SUS) SUSY with R-parity violation (SUR)

KEK 全体図

KEK-12GeV PS

• Stopped K+ method• Large solid angle and high resolution of

Toroidal Spectrometer and CsI(Tl) calorimeter

side view end view

decay

T-violation search in KEK E246 experiment

Experimental setup

Double ratio measurement ＋ PT(π0 forward) ＝　－ PT(π0 backward)

PN contribution to systematic error is drastically reduced.

Determination of PT

Stopped K+ beam

Stopped K+ のため target と、fwd/bwd π0 検出器が重要な鍵となる。

K+ 静止用ターゲット

• K+ 静止崩壊用ターゲット• 直径 8cm のプラスティック• ２５ 6 本のシンチレーションファイバー

で構成• 読み出し： PMT （浜松 H1635)

• K+ 崩壊位置を特定する

Pπ 測定

measurement of Pπ, Pμ,Sμ

• Pπ ：　 CsI(Tl) calorimeter

Using Stopped K+

not only 2 γ but also 1 γ with high energy

σ ＝１４ MeV

CsI(Tl) photon detector

Segmentation = = 7.5o

Number of crystals 768Length of crystals 25 cm (13.5 X0)Inner radius 20 cmOuter radius 50 cmSolid angle ~75%of 4 Readout PIN diodeLight yield 11000 p.e./MeVEquiv. noise level 65 keVΔE/E 12-14% at 1257 keV

(22Na)σE 　　　　　　　　 3% at 200MeV

D.V.Dementyev et al. Nucl. Instr. Method A440 (2000) 151

Pin diode 使用により、•　強磁場での利用可能•　省スペース化

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

New experiment at J-PARC We aim at a sensitivity of PT ~10-4 (E246-PT ~10-3)

Statistical errorPT

stat ≤ 0.1 PTstat (E246) ~10-4 with

1) × 30 of beam intensity, 2) × 10 of detector acceptance, and3) higher analyzing power

Systematic errorPT

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

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

JPARC

J-PARC 施設

Parameters of Main Ring Extraction Beam Energy 　 50 GeVAverage Beam Current 　　 15 μARepetition 　　　　　　　　　　 0.3 HzExtraction Scheme 　　　　 Fast, and Slow

Upgrade of the detector

Muon polarimeter passive → active

Muon magnetic field toroid → muon field magn

et Target

smaller and finer segmentation

Charged particle tracking addition of two chambers

CsI(Tl) readout PIN diode → APD

New analysis scheme

Target

Smaller size (smaller beam spot) Finer segmentation Sci. fiber of 20 cm length Clear fiber or direct attachment Light readout by SiPMTs

Diameter 6 cmActive length 20 cmFiber size 2.5×2.5 mmNo. of fibers 432Light readout 4 clear fibersLight yield ~ 10/SiPMT

Target and tracking Better kinematical resolution Stronger K2 dif + BG

suppression

Addition of C0 and C1 GEM chambers with - high position resolution

- higher rate performance

Larger C3-C4 distance

Use of He bags

New target

E246 J-PARC

CsI(Tl) readout CsI(Tl) + APD + Amplifier + FADC Electrons after APD : ~ 2 ×107 @ 100 MeV Max count rate / module : ~ 100 kHz Max K+ decay rate : ~ 20 MHz

- enough for the beam intensity in Phase 1 Noise level : to be tested Module energy resolution : to be tested

-Energy resolution is determined by lateral shower leakage

Sensitivity estimate

Source PT • Net run time 1.0 ×107 s• Proton beam intensity 9A on T1• K+ beam intensity 3×106 /s• Total number of good K3 2.4×109

• Total number of fwd/bwd (N) 7.2×108

• Sensitivity coefficient 3.73√N

Total ~ 10-4

Statistical sensitivity Systematic errors

Source PT z < 10-

4

z < 10-4

e+, Ee+ < 10-4

Total ~ 10-4

JPARC

SummaryPT in K3 is a very sensitive probe of new physicsWe propose a J-PARC experiment in the early stage of Phas

e 1 to pursue a limit of PT ~ 10-4.

K0.8 beamline as a branch of K1.1Upgraded E246 detector

Beam time request = 1.3×107 s (net) at Ip= 9A on T1

We would like to take the first step this year toward– Collaboration forming– Fund application– Detector R&D

after obtaining some status.