measurement of t-violating transverse muon polarization in + decays at j-parc suguru shimizu...
DESCRIPTION
Matrix element of K + → decay P T is sensitive to scalar couplings. T-violation parameter : Im(ξ) Im(ξ)≠0 T-violationTRANSCRIPT
Measurement of T-violating Transverse Muon Polarization in
+→ Decaysat J-PARC
Suguru SHIMIZUOsaka University
Oct. 6, 2006SPIN2006
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
Beyond the Standard Model Standard Model contribution to PT :
– Only from vertex radiative corrections and PT(SM) < 10-7
Spurious effects from final state interactions (FSI)– Recent elaborate calculation : 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.
Model descriptions of PT Multi-Higgs doublet (3 Higgs doublet) model (MH)
– Im = (mK2/mH
2) Im(11*)
– | Im(11*) | < 544 (mH/GeV)2 from the E246 limit
– B→X constraints also Im(11*) but weaker ( <1900 (mH/GeV)2 )
– N-EDM and b→s constraint differently Im(11*)
SUSY with s-quark mixing (SUS)– Im ∝ Im[V33
H+ V32DL* V31
UR*]/ mH2
– mH ≥ 140 GeV from the E246 limit and no stringent limit from other modes
SUSY with R-parity violation (SUR)– Iml ~ Im [2i2(i12)*], Imd ~ Im [’21k(’22k)*]– No stringent limits from other modes
• 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
Double ratio measurement + PT(π0 forward) = - PT(π0 backward)
PN contribution to systematic error is drastically reduced.
Determination of PT
Stopped K+ beam B
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
PRD73, 072005(2006)
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
Systematic errorPT
syst ~ 0.1 PTsyst (E246) ~10-4 by
1) precise calibration of misalignments using data 2) correction of systematic effects
JPARC
Method of experiment Stopped K+ decay
– Superior to in-flight decay Toroidal spectrometer
E246 detector upgrade–Well known performance–Well studied systematics–Good alignment in magnet and CsI(Tl)–Lower cost
FoM (A√N) distribution
Detector acceptance
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
Active polarimeter Identification of muon stopping point/ decay vertex Measurement of positron energy Ee+ and angle e+ Large positron acceptance of nearly 4 Larger analyzing power Higher sensitivity Lower BG in positron spectra
Parallel plate stopper withGap drift chambers Number of plates 31 Plate material Al, Mg or alloy Plate thickness ~ 2 mm Plate gap ~ 8 mm Ave. density 0.24 Al
stop efficiency ~ 85%
Small systematics for L/R positronFit for 0 fwd/bwd measurement
Muon field magnet
Uniform field of 0.03 T Precise field alignment of 10-3
Gap : 30 cm Pole face : 60 cm ×40 cm No. of coils : 24 Mag. motive force : 3.6×103 A Turn/coil
20 cm
Systematic error from B field rotation
• muon field magnet• Active polarimeter
fwd
bwd
PN
fwd
PNbwd
spectrometer
Side View End View
PNfwd
PNbwd
Left RightLeft Right
B
π0 fwd 1+ PN
bwd 1 PN
fwd/bwd = 1+2PN ≠1
systematic error
Calibration of the polarimeteris very Important.
BPT
fwd PTbwd
π0 fwd 1+ PT
bwd 1 PT
fwd/bwd = 1+2PT
Calibration of four misalignments
Polarimeter left/right asymmetry measurement using
longitudinal pol. PL K+→ (K2 )
radial polarization Pr from K+→(K2 )-+
decay in flight
PrPL
dangerous
A(PL)= (r r )cost + (z-z) sint + r A(Pr)= (rr) sint (z-z) cost + z
Unique determination ofr z r z
with an accuracy of ~10-4
r
r
z
Z
MC results: calibration of misalignments
r=(3.7±0.2) x 10-3
z=(4.0±0.2) x 10-3
r=(3.9±0.2) x 10-3
z=(3.7±0.2) x 10-3
with use of 108 muons
K: 1 day collectionK: simultaneous data collection with K
PrPL
4 rotations
L:blackR: red
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
MC studies of tracking
Four chamber tracking including C0 with 0.1mm resolution Suppression of K2-dif down to ~1.0% Remaining BG is from the + decay between the target and C0. Further suppression down to 0.1% level with the fit trajectory consistency with target fibers, and tar
get fiber analysis.
PT (2 BG) < 10-4
K3 K2-dif
Beamline for K+ extraction
Momentum 800 MeV/cMomentum bite ±2.5%Acceptance 6.5 msr % p/pK+ intensity 3 ×106 /sK/ ratio > 2Beam spot 1.04 ×0.78 cm (FWQM)Final focus achromatic
K0.8 ( K1.1-BR)
K0.8
proton
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 stag
e of Phase 1 to pursue a limit of PT ~ 10-4.
New K0.8 beamlineUpgraded E246 detector
Stage 1 approval– Upgrade will be finished by 2010. – Data taking will be started from 2011.
Collaboration (present group)
Canada U.Saskatchewan TRIUMF UBC U. Montreal
USA MIT U. South Carolina Iowa State U.
Japan KEK Tohoku U. Osaka U. NDA
Beamline Target
Muon field magnet Active polarimeter CsI(Tl) readout DAQ
GEM chambers Tracking upgrade
We will organize more people after obtaining an approval.