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.