Transcript Measurement of T-violating Transverse Muon Polarization in

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
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
清水俊
大阪大学理学研究科
Transverse muon polarization
K+→p0m+n decay
T-odd

Spurious effects from final state interaction are small. Nonzero 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)
Matrix element of K+→p0m+n decay
T-violation parameter : Im(ξ)
Im(ξ)≠0
PT is sensitive to scalar couplings.
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-12GeV PS
KEK 全体図
T-violation search in KEK E246 experiment
• Stopped K+ method
• Large solid angle and high resolution of
Toroidal Spectrometer and CsI(Tl) calorimeter
side view
decay
end view
Experimental setup
Determination of PT
Stopped K+ beam
Double ratio measurement
＋PT(π0 forward) ＝ －PT(π0 backward)
PN contribution to systematic error is
drastically reduced.
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
• ２５6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
Using Stopped K+
measurement of Pπ, Pμ,Sμ
• Pπ： CsI(Tl) calorimeter
not only 2 γ but also 1 γ
with high energy
σ＝１４MeV
CsI(Tl) photon detector
D.V.Dementyev et al.
Nucl. Instr. Method A440
(2000) 151
Segmentation
Dq = Df = 7.5o
Number of crystals
768
Length of crystals
25 cm (13.5 X0)
Inner radius
20 cm
Outer radius
50 cm
Solid angle
~75%of 4p
Readout
PIN diode
Light yield
11000 p.e./MeV
Equiv. noise level
65 keV
ΔE/E
12-14% at 1257 keV(22Na)
σE
3% at 200MeV
Pin diode使用により、
• 強磁場での利用可能
• 省スペース化
E246 result
AT = (Afwd - Abwd ) / 2
Afwd(bwd) =
Ncw - Nccw
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. )
Statistical error dominant
New experiment at J-PARC

We aim at a sensitivity of dPT ~10-4 (E246-dPT ~10-3)
Statistical error
dPTstat ≤ 0.1 dPTstat (E246) ~10-4 with
1) × 30 of beam intensity,
2) × 10 of detector acceptance, and
3) higher analyzing power
Systematic error
dPTsyst ~ 0.1 dPTsyst (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
Average Beam Current
Repetition
Extraction Scheme
50 GeV
15 μA
0.3 Hz
Fast, and Slow
Upgrade of the detector
Muon polarimeter
passive → active
 Muon magnetic field
toroid → muon field magnet
 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
Active length
Fiber size
No. of fibers
Light readout
Light yield
6 cm
20 cm
2.5×2.5 mm
432
4 clear fibers
~ 10/SiPMT
Target and tracking


Better kinematical resolution
Stronger Kp2 dif m+ BG
suppression
E246
 Addition
of C0 and C1
GEM chambers with
- high position resolution
- higher rate performance
J-PARC


Larger C3-C4
distance

Use of He bags
New target
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
Statistical sensitivity
Systematic errors
Source
• Net run time
• Proton beam intensity
• K+ beam intensity
• Total number of good Km3
• Total number of fwd/bwd (N)
• Sensitivity coefficient
dPT
1.0 ×107 s
9mA on T1
3×106 /s
2.4×109
7.2×108
3.73√N
Total
~ 10-4
JPARC
Source
dPT
dz
qz
qe+, Ee+
< 10-4
< 10-4
< 10-4
Total
~ 10-4
Summary
 PT in Km3 is a very sensitive probe of new physics
 We propose a J-PARC experiment in the early stage of Phase 1
to pursue a limit of dPT ~ 10-4.
 K0.8 beamline as a branch of K1.1
 Upgraded E246 detector
 Beam time request = 1.3×107 s (net) at Ip= 9mA on T1
 We would like to take the first step this year toward
– Collaboration forming
– Fund application
– Detector R&D
after obtaining some status.