Download - Problem assigned by PAC1
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Progress Report to PAC3J-PARC E06 Experiment (TREK)
Measurement of T-violating Transverse Muon Polarization (PT) i
n K+→ DecaysJ. ImazatoJuly 6, 2007
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Problem assigned by PAC1
The PAC would like the proponent to show that the improvement on the sensitivity and systematic uncertainty below 10-4 is attainable via detailed Monte Carlo studies, e.g. acceptance, B-field offset, detector misalignments and the new polarimeter.
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Outline
Statistical sensitivity estimateSystematic error estimate
Polarimeter misalignmentsOther systematics
R&D for the detector upgradeCollaboration/Cost/Funding/BeamSummary
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Transverse polarization in K3
K+→decay
PT is T-odd and spurious effects from final state interaction
are small. Non-zero PT is a signature of T violation. Standard Model contribution to PT : PT(SM) < 10-7
Spurious effects from final state interactions : PT(FSI) < 10-5
There are theoretical models which allow sizeable PT
without conflicting with other experimental constraints.
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PT measurement
Ncw - NccwAfwd(bwd) = ; AT = (Afwd - Abwd ) / 2 Ncw - Nccw
Use of upgraded E246 detector
PT measured as the azimuthal asymmetry of the + decay e+
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Statistical sensitivity estimate
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Factors for statistical sensitivity K+ beam intensity × Run timeK+ stopping efficiency (stop~0.30 according to a MC )
K+→event rate with + in the polarimeter ❶– E246 experience + MC calculation
→e+event rate with e+ detected, and polarization analyzing power : = AT / PT ❷
– MC calculation for the new active polarimeter
In determining the sensitivity, ❶ and ❷ are separable.
They are shown next step by step.
_
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Positron asymmetry measurement
E06:conservative estimate now by fwd/bwdambitious analysis including left/right event-by-event analysis: future option
E246: 0- forward (fwd) and backward (bwd) integral analysis
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Optimum e+ measurement
Eeth = 38 MeV
coseth = 0.34
= 0.38 (cf. 0.27 in E246)
PT = AT / <cosT> : analyzing power, <cosT> : attenuation factor Figure of Merit (FoM) optimization by a MC simulation using a realistic + stopper condition
FoM = AT√Ne+
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Optimum 0 measurement
costh = 0.30
<cos> = 0.68 PT = AT / 0.258
Optimization of th by FoM of
FoM = <cos0> √No
cosT ≈ cos0
up to finite + acceptance +
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K3 event rate and sensitivity Standard event selection conditions as in E246 :
1. 65 < M < 185 MeV/c2
2. 3500 < M2TOF < 18,000 (MeV/c2)2
3. p <185 MeV/c4. + incident into the polarimeter5. < 160o
6. M2missing > -15,000 (MeV/c2)2
⇒ Detector acceptance = 1.14 ×10-2
N(K) = N(K+) ・ stop・ Br(K) ・ = 3.3 × 109 (total E06 good events)
MC calculation for 108 events and using PT =AT / 0.258 : PT = 6.9 / √N(K) = 1.2 ×10-4
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Summary of statistical sensitivity
PT =1.2×10-4 for the fwd+bwd integral analysis compared with PT = 1.8×10-4 given in the proposal . – Significant gain due to e cut and realistic event selection (The effect of Ee+ threshold was partially included in the proposal.)
We will attack the event-by-event weighted analysis aiming for PT = 1.0×10-4 (fwd+bwd) and PT = 0.8×10-4 (including left+right).
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Update of run time
K+ beam intensity @ 9A p on T1 is now 2.1×106 /sNecessary run time is now 1.4×107 s. ( It was 1.0×107 s in the proposal.)
K1.1-BR beam optics was changed due to B1 position
2005 design 2007 design
Acc = 6.0 msr %p/p Acc = 4.5 msr %p/p
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Systematic error estimate
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Source of Error 12 fwd/bwd PT x 104
e+ counter r-rotation x o 0.5e+ counter z-rotation x o 0.2e+ counter f-offset x o 2.8e+ counter r-offset o o <0.1e+ counter z-offset o o
<0.1+ counter f-offset x o <0.1MWPC-offset (C4) x o 2.0CsI misalignment o o 1.6B offset () x o 3.0B rotation (x) x o 0.4B rotation (z) x x 5.3K+ stopping distribution o o <3.0+ multiple scattering x x 7.1Decay plane rotation (r) x o 1.2Decay plane rotation (z) x x 0.7K2 DIF background x o 0.6K+ DIF background o x
< 1.9Analysis - - 3.8
Total 11.4
E246 systematic errors
Cancellation by 12 and/or fwd/bwd almost all systematics except for :
+ field alignment
+ multiple scattering decay plane shifts due to • K+ stopping distribution • Detector inefficiency distribution etc.
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Suppression of systematic errors in E06
• + field alignment : PT < 10-4
– PT analysis free from misalignment
• + multiple scattering : PT < 0– no longer relevant with the active polarimeter
• decay plane shifts : PT < 10-4
– correction for PT only with statistical uncertainty
• active polarimeter e+ analysis : PT < 10-4
– Perfect fwd/bwd cancellation mechanism
Old errors
Newcomer
PTsyst ~ 0.1 PT
syst (E246) ~10-4
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e+ asymmetrydue to
polarimeter misalignment
Rotation aboutComponent r-axis z-axisPolarimeter r z Muon field r z
fwd - bwd : vanishes for r , z , r when t-integrated
fwd - bwd : not vanishing for z !
spurious AT ?
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Misalignment analysis using K3
z ~ r ~ 3×10- 4 for misalignment determination
PT < 1.2×10- 4 for PT determination from Asub
Asum(0)Asub(0)
Asymmetry analysis in terms of 0 : in plane spin angle from z-axis
PT
PT+z
PT+r
PT+z+r
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Systematic error (1) associated withmisalignment analysis
PT can be deduced regardless of the existence of the polarimeter misalignments, r, z, r and z.
But, how much is the systematic error induced in this misalignment analysis? Simulation calculation with:
PT = 0 and z = r = 5o = 87 mr ==> PT = (2±7)×10-4 for 108 events Essentially statistical error of PT No significant effect beyond the statistical error In reality, z ~ r ~ 1 mr : PT
syst should be < 10-4
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Systematic error (2) due to K2 BGDangerous + -> background with a PT componentSubstantial reduction due to the addition of the C0 chamber
Cancellation in gap integration ==> averaging to < 1/10 (<0.02%) 0 - fwd/bwd cancellation ==> suppression to < 1/10 (<0.002%)
PT < 10-4
MC simulation
Momentum resolutions Consistency
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Systematic error (3) associated with decay plane rotation correction
Two rotation angles of z and r
Relation: PT ~ 0.5 <> due to PN and PL admixture <r> is fwd/bwd cancelling, but <z> is not fwd/bwd cancelling.
PT will be corrected for <z> and <r>
Statistical error of the correction <z> = (z) /√Ntotal PT (<z>) ≪ PT
stat ~ 10-4
z distribution in E246 <z>= -0.004±0.12 mr
-1 0 +1 0
PT (<z>) ≪ 10-4
PT (<r>) ~ PTstat& fwd/bwd
≪ 10-4
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Systematic errors (4) associated with positron analysis
Systematics in the chamber measurement is left-right canceling :
cell inefficiency plate non-uniform thickness etc.
further cancellation by fwd-bwd up to small = fwd -bwd symmetrization of with biasfwd(r,y,z) = bwd(r,y,z) PT
fwd = PT + PT’ PT
bwd = -PT + PT” No problem
Cancellation power will be calculated using data.
= fwd -bwd was a few % in E246
PT should be < 10-4
+ stopping distribution in the stopper
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R&D of detector upgrade
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Upgraded elements
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Stopper SR study (Canada, Japan)
TRIUMF surface muon beam with full polarization E1120 experiment to study SR in Al and Mg alloys Transverse field (TF) and longitudinal field (LF) relaxation rates were
measured with a 0.03 T field. Several candidate stopper materials were confirmed.
Al alloys: A5052, A6063, Mg alloys: AZ31, ZK60, Z6, AM60, AZ91
Muon spin behavior was studied for candidate stopper materials
Typical TF precession pattern
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CsI(Tl) readout (INR)
Cosmic ray test Energy Timing
First application of APD readout to a large CsI(Tl) calorimeter
Very good timing characteristics were confirmed
t =3ns
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Fiber target (INR, KEK)
2.5x2.5 mm x 20 cm fiber Tapered coupling to MPPC Yield of ~ 20 p.e. for 90Sr
Target cross section Light yield test of the fiber
20 cm + clear fiber + MPPC
Pulse height spectrum Pulse shape
MPPC radiation hardness test at RCNP
Increasing leakage current with dose Design of shielding
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C0 and C1 GEM chambers (MIT)
Three chambers were beam-tested at FNAL by MIT GEM Lab.
H- and V-amplitude correlation
Middle residual
• Stable operation• Resolution of x = 90 m• Rate capability• Readout electronics A
mpl
itude
ver
tical
Amplitude horizontal Residual x (mm)
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Muon field magnet (KEK)TOSCA 3D calculation
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Collaboration/Funding/Beamline
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Collaboration• Canada Univ. of Saskatchewan, Univ. of British Columbia, TRIUMF, Univ. of Montreal• U.S.A. MIT, Iowa State Univ., Univ. of South Carolina• Japan KEK, Osaka Univ., Tohoku Univ., Kyoto Univ., NDA- New participation - • Russia INR (group with E246 experience) Altogether • Vietnam Nat. Sci. Univ. in HCMC 35 people
International cooperation in detector construction
Strong support from : (1) TRIUMF detector shop, and (2) MIT GEM Lab.
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Beamline preparationK1.1
K1.1-BR
K1.1BR uses the upstream part of K1.1.
No budget is allocated for K1.1 in the J-PARC budget, although it is one of the planned secondary lines in Phase 1.
We would like to go ahead with the BR (700-800 MYen), with a possible Canadian contribution to the 0.8 GeV leg.
Once full beam operation has started at T1, it will become very difficult to install the frond end of the channel (B1, Q1, Q2, B2). Timely installation of K1.1/K1.1BR is absolutely necessary.
T1
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Cost estimate and funding policy
Updated cost estimate :– Detector upgrade etc. 279,710 kYen– Transfer of the SC spectrrometer 182,000 kYen– K1.1BR branch construction 50,000 kYen(These are not very different from the estimates in the proposal.)
Policy for funding :
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Time scheduleTotally dependent on the K1.1-BR beamline installation a
nd funding of the experiment. In the proposal we presented:
2009 1) Spectrometer setup 2) Field mapping 3) Detector setup 4) Beam tuning
2010-11 5) Engineering run, and 6) Data taking
We would like to pursue the earliest possible schedule aiming to provide the first particle physics output from the hadron hall.
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Theory impact
A clean search for CP violation via Higgs dynamics.
Direct CP violation presumably unsuppressed by I=1/2 rule
PT ~ [’effect × 20 = 5 x 10-6 × 20 ~ 10-4
-- unless enhanced couplings to leptons!
(I. Bigi, CERN Flavor WS, 2007 )
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Summary
We have shown with MC studies that E06 can reach at least the statistical sensitivity of PT =1.2×10-4 in the safe fwd+bwd integral analysis.
We have established a PT extraction method in the presence of any polarimeter misalignments.
We have shown that other systematics should be controllable to the level < 10-4.
We have demonstrated the validity of the proposed upgraded detector elements with necessary test experiments.
PAC341
Our request to PAC
The Canadian and American groups are starting budget requests in their countries. The status of stage-2 approval is very necessary for a successful application. The PAC is requested to consider E06 for the stage-2 approval although there are no funds yet in place.
An endorsement of the K1.1BR beamline installation for E06 is desirable. The PAC is also asked to make a strong recommendation to the IPNS/J-PARC management to provide a plan for the K1.1BR construction so that the Canadian group will be able to request money for a contribution to this stopped K+ beamline.
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END of Slides
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K+ Stopping efficiency
Optimum degrader thickness Target diameter of
d=8cmd=6cmd=4cm
FOM is maximum at
800 MeV/c
stop=0.25~0.30
GEANT3 calculation
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Stopped beam method
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
Double ratio experiment
AT = (Afwd - Abwd ) / 2
Ncw - NccwAfwd(bwd) = Ncw - Nccw
PT = AT / {<cosT>} : analyzing power <cosT> : attenuation factor Im = PT / KF
KF : kinematic factor bwd - fwd -
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Target of E06
E246 detector is upgraded for E06
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Sensitivity improvement in E06 We aim at a sensitivity of PT ~10-4
PTstat ~0.05 PT
stat (E246) ~10-4 with
1) × 30 beam intensity, 2) × 10 detector acceptance, and3) Higher analyzing power
PTsyst ~ 0.1 PT
syst (E246) ~10-4 by 1) Precise calibration of misalignments using data
2) Correction of systematic effects3) Precise fwd-bwd cancellation of systematics by dat
a symmetrization (Estimate of cancellation power using data)
Most crucial systematics are misalignment of : Muon polarimeter and muon field distribution
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E246 muon polarimeterCross section One-sector view
y(cm)
B
+ → e+e W(e+) ∝ 1 + A cos
Passive polarimeter with• Al muon stopper• Left/Right positron counterssimple analysis and systematics
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Active muon stopoper 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 wire 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 e+ asymmetry measurement Fit for 0 fwd/bwd measurement Simple structure
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Spin relaxation rate
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Tracking system
E246 J-PARC E06
C0 (cylindrical) and C1(planer) are GEM chambers
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Tracking performance
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Rad.hardness test of MPPC
MPPC 400 pixel typeIrradiation of up to 36 Gy
Increase of leakage current proportional to dose
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Beam halo simulation GEANT4 simulation 10 cm- BeO degrader + 6 cm-Target
K+ flux distribution
+
+
e+
n
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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
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APD readout of CsI(Tl)
• E246 CsI(Tl)• 5 x 5mm APD• CR measurement• 1.5 s width
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Tracking system alignmentUse of a collimator system
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CsI(Tl) alignment Use of K+ → with back to back kinematics
azimuthal rotation two tilt angles
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e+ asymmetrydue to
polarimter misalignmnet
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Precession patterns due to misalignments
r=1o r=1o
z=1o z=1o
@= 0o
- A kind of normalization -
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Misalignment analysis
• Effects of z andr vanish.
• 0 determination event-by-event using K3 form factors.
• Ambiguity of 0 determination is not problematic.
Time-integrated asymmetry function
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dependence of the asymmetry
0-fwd 0-bwd
PT
z=5o r=5o
N
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Correction for decay plane rotation
• Two rotation angles of z and r
• Relation: PT ~ 0.5 <z>, ~ 0.5 <r>• PT will be corrected for <z> and <r>
<r> is fwd/bwd cancelling, but
Statistical error of the correction <z> = (z)/√Ntotal
PT(<z>) ≪ PTstat ~ 10-4
z distribution in E246 <z>= -0.004±0.12 mr -1 0
+1 0
<z> is not fwd/bwd cancelling.
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Data symmetrization
K+ stopping distribution• non-bias cut• small loss of events
- Suppression of systematic errors -
+ stopping distributions fwd(r,y,z) ≠bwd(r,y,z) ⇩fwd(r,y,z) = bwd(r,y,z)
PTfwd = PT + PT’
PTbwd = -PT + PT”
eliminates systematics in the polarimeter
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Group members
: core members (younger people)
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Trigger rate reduction