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Progress Report to PAC3 J-PARC E06 Experiment (TREK) Measurement of T-violating Transverse Muon Polarization ( P T ) in K + → p 0 m + n Decays J. Imazato July 6, 2007. Problem assigned by PAC1.

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slide1

Progress Report to PAC3J-PARC E06 Experiment (TREK)Measurement of T-violating Transverse Muon Polarization (PT) in K+→p0m+n DecaysJ. ImazatoJuly 6, 2007

problem assigned by pac1
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.

outline
Outline
  • Statistical sensitivity estimate
  • Systematic error estimate
    • Polarimeter misalignments
    • Other systematics
  • R&D for the detector upgrade
  • Collaboration/Cost/Funding/Beam
  • Summary
transverse polarization in k m 3
Transverse polarization in Km3

K+→p0m+ndecay

  • PT is T-odd and spurious effects from final state interaction

are small.Non-zero PTis 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.
p t measurement
PT measurement

Use of upgraded E246 detector

PT measured as the azimuthal

asymmetry of the m+ decay e+

Ncw - Nccw

Afwd(bwd) = ; AT = (Afwd - Abwd) / 2

Ncw - Nccw

factors for statistical sensitivity
Factors for statistical sensitivity

_

  • K+ beam intensity × Run time
  • K+ stopping efficiency (estop~0.30according to a MC )
  • K+→p0m+n event rate with m+ in the polarimeter ❶
    • E246 experience + MC calculation
  • m+→e+nn event rate with e+ detected, and

polarization analyzing power : a = AT / PT❷

    • MC calculation for the new active polarimeter

In determining the sensitivity,❶and❷are separable.

They are shown next step by step.

slide8

Positron asymmetry measurement

  • E246:
  • p0- forward (fwd)
  • and backward (bwd)
  • integral analysis
  • E06:
  • conservative estimate now by fwd/bwd
  • ambitious analysis including left/right
  • event-by-event analysis: future option
optimum e measurement
Optimume+measurement
  • PT = AT / a <cosqT>
  • a : analyzing power,
  • <cosqT> : attenuation factor
  • Figure of Merit (FoM) optimization by a MC simulation using a realistic m+ stopper condition

FoM = AT√Ne+

  • Eeth = 38 MeV
  • cosqeth = 0.34
  • a = 0.38

(cf. 0.27 in E246)

optimum p 0 measurement
Optimum p0 measurement
  • cosqT ≈ cosqp0
  • up to finite m+ acceptance qm+
  • cosqpth = 0.30
  • <cosqp0> = 0.68
  • PT = AT/ 0.258
  • Optimization of qpth by FoM of
  • FoM = <cosqp0> √Npo
k m 3 event rate and sensitivity
Km3 event rate and sensitivity
  • Standard event selection conditions as in E246 :
    • 65 < Mgg < 185 MeV/c2
    • 3500 < M2TOF < 18,000 (MeV/c2)2
    • pm+ <185 MeV/c
    • m+ incident into the polarimeter
    • qm+p0 < 160o
    • M2missing > -15,000 (MeV/c2)2

⇒ Detector acceptanceW(Km3) = 1.14 ×10-2

N(Km3) = N(K+)・estop・Br(Km3)・ W(Km3)

= 3.3 × 109 (total E06 good events)

  • MC calculation for 108 events and using PT =AT / 0.258 :

dPT = 6.9 / √N(Km3)

= 1.2 ×10-4

summary of statistical sensitivity
Summary of statistical sensitivity
  • dPT =1.2×10-4 for the fwd+bwd integral analysis compared with dPT = 1.8×10-4 given in the proposal .
    • Significant gain due to qe 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 dPT = 1.0×10-4 (fwd+bwd) and dPT = 0.8×10-4 (including left+right).
update of run time
Update of run time
  • K1.1-BR beam optics was changed due to B1 position

2005 design

2007 design

  • K+ beam intensity @ 9mA p on T1 is now 2.1×106 /s
  • Necessary run time is now 1.4×107 s.

( It was 1.0×107 s in the proposal.)

Acc = 6.0 msr %Dp/p

Acc = 4.5 msr %Dp/p

slide15

E246 systematic errors

Source of ErrorS12 fwd/bwddPTx 104e+ 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 <0.1m+ counter f-offset x o <0.1MWPC f-offset (C4) x o 2.0CsI misalignment o o 1.6B offset (e) x o 3.0B rotation (dx) x o 0.4B rotation (dz) x x5.3K+ stopping distribution o o <3.0m+ multiple scattering x x7.1Decay plane rotation (qr) x o 1.2Decay plane rotation (qz) x x0.7Kp2 DIF background x o 0.6K+ DIF background o x < 1.9Analysis - - 3.8Total 11.4

  • Cancellation by

S12 and/or

fwd/bwdalmost

all systematics

  • except for :
  • m+ field alignment
  • m+ multiple scattering
  • decay plane shifts
  • due to
  • K+ stopping distribution
  • Detector inefficiency
  • distribution etc.
suppression of systematic errors in e06
Suppression of systematic errors in E06

Old errors

  • m+ field alignment : dPT < 10-4
    • PT analysis free from misalignment
  • m+ multiple scattering : dPT < 0
    • no longer relevant with the active polarimeter
  • decay plane shifts : dPT < 10-4
    • correction for PT only with statistical uncertainty
  • active polarimeter e+ analysis : dPT < 10-4
    • Perfect fwd/bwd cancellation mechanism

Newcomer

  • dPTsyst ~ 0.1 dPTsyst (E246) ~10-4
e asymmetry due to polarimeter misalignment
e+ asymmetrydue topolarimeter misalignment

Rotation about

Component r-axis z-axis

Polarimeter erez

Muon field drdz

fwd - bwd : vanishes for

er , ez , dr when t-integrated

fwd - bwd : not vanishing

for dz !

spurious AT ?

misalignment analysis using k m 3
Misalignment analysis using Km3

Asymmetry analysis in terms of q0 : in plane spin angle from z-axis

PT

PT+dz

PT+dr

PT+dz+dr

Asum(q0)

Asub(q0)

  • Ddz ~ Ddr ~ 3×10-4 for misalignment determination
  • dPT < 1.2×10-4 for PT determination from Asub
systematic error 1 associated with misalignment analysis
Systematic error (1) associated withmisalignment analysis
  • Simulation calculation with:

PT= 0 and dz = dr= 5o = 87 mr

==> dPT= (2±7)×10-4 for 108 events

    • Essentially statistical error of PT
    • No significant effect beyond the statistical error
    • In reality, dz ~ dr ~ 1 mr :
    • dPTsystshould be < 10-4
  • PT can be deduced regardless of the existence of the polarimeter misalignments, er, ez, dr and dz.
  • But, how much is the systematic error induced in this misalignment analysis?
systematic error 2 due to k p 2 bg
Systematic error (2) due to Kp2 BG

Momentum resolutions

Consistency

MC simulation

  • Cancellation in gap integration
  • ==> averaging to < 1/10 (<0.02%)
  • p0 - fwd/bwd cancellation

==> suppression to < 1/10 (<0.002%)

dPT < 10-4

  • Dangerous p+ -> m+n background with a PT component
  • Substantial reduction due to the addition of the C0 chamber
systematic error 3 associated with decay plane rotation correction
Systematic error (3) associated with decay plane rotation correction
  • Two rotation angles of qz and qr
  • Relation: dPT ~ 0.5 <q>due to PN and PL admixture
    • <qr> isfwd/bwd cancelling, but

<qz> isnot fwd/bwd cancelling.

  • PTwill be corrected for <qz> and <qr>

qz distribution in E246

<qz>= -0.004±0.12 mr

  • Statistical error of the correction
  • d<qz> = s(qz) /√Ntotal
  • dPT (<qz>) ≪dPTstat ~ 10-4

dPT (<qz>) ≪ 10-4

dPT (<qr>) ~dPTstat&fwd/bwd

≪ 10-4

-1 0 +1

0

systematic errors 4 associated with positron analysis
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 Dr = rfwd - rbwd

  • symmetrization of r with bias
  • rfwd(r,y,z) = rbwd(r,y,z)
  • PTfwd = PT + dPT’
  • PTbwd = -PT+ dPT” No problem
  • Cancellation power will be calculated using data.

m+ stopping

distribution

in the stopper

Dr = rfwd - rbwd

was a few % in E246

dPTshould be < 10-4

stopper m sr study canada japan
Stopper mSR study (Canada, Japan)
  • Muon spin behavior was studied for candidate stopper

materials

Typical TF precession pattern

  • TRIUMF surface muon beam with full polarization
  • E1120 experiment to study mSR 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

csi tl readout inr
CsI(Tl) readout (INR)
  • First application of APD readout to a large CsI(Tl) calorimeter

Cosmic ray test

Energy Timing

st =3ns

  • Very good timing characteristics were confirmed
fiber target inr kek
Fiber target (INR, KEK)
  • Target cross section
  • Light yield test of the fiber

Pulse height

spectrum

Pulse shape

  • 2.5x2.5 mm x 20 cm fiber
  • Tapered coupling to MPPC
  • Yield of ~ 20 p.e. for 90Sr

20 cm + clear fiber + MPPC

  • MPPC radiation hardness test

at RCNP

    • Increasing leakage current

with dose

    • Design of shielding
c0 and c1 gem chambers mit
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
  • Dx = 90 mm
  • Rate capability
  • Readout electronics

Amplitude vertical

Amplitude horizontal

Residualx(mm)

muon field magnet kek
Muon field magnet (KEK)

TOSCA 3D calculation

collaboration
Collaboration
  • International cooperation in detector construction
  • 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
  • Strong support from : (1) TRIUMF detector shop, and
  • (2) MIT GEM Lab.
beamline preparation
Beamline preparation

K1.1

  • 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.

K1.1-BR

T1

cost estimate and funding policy
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 :
time schedule
Time schedule
  • Totally dependent on the K1.1-BR beamline installation and funding of the experiment.
  • In the proposal we presented:

20091) 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.
theory impact
Theory impact
  • A clean search for CP violation via Higgs dynamics.
  • Direct CP violation presumably unsuppressed by DI=1/2 rule

PT ~ [e’/e effect]× 20 = 5 x 10-6× 20 ~ 10-4

-- unless enhanced couplings to leptons!

(I. Bigi, CERN Flavor WS, 2007 )

summary
Summary
  • We have shown with MC studies that E06 can reach at least the statistical sensitivity of dPT =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.
our request to pac
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.

PAC3

k stopping efficiency
K+Stopping efficiency

GEANT3 calculation

  • Optimum degrader

thickness

  • Target diameter of
    • d=8cm
    • d=6cm
    • d=4cm
  • FOM is maximum at

800 MeV/c

  • estop=0.25~0.30
stopped beam method
Stopped beam method
  • Double ratio experiment
  • AT = (Afwd - Abwd) / 2
  • Ncw - Nccw
  • Afwd(bwd) =
  • 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. )

bwd -p0 (g )

fwd -p0 (g )

Statistical error dominant

target of e06
Target of E06
  • E246 detector is upgraded for E06
sensitivity improvement in e06
Sensitivity improvement in E06
  • We aim at a sensitivity of dPT ~10-4
  • dPTstat ~0.05 dPTstat (E246) ~10-4 with

1) ×30 beam intensity,

2) ×10 detector acceptance, and

        • Higher analyzing power

dPTsyst ~ 0.1 dPTsyst (E246) ~10-4by

1) Precise calibration of misalignments using data

2) Correction of systematic effects

        • Precise fwd-bwd cancellation of systematics by data

symmetrization

(Estimate of cancellation power using data)

  • Most crucial systematics are misalignment of :

Muon polarimeter and muon field distribution

e246 muon polarimeter
E246 muon polarimeter

One-sector view

Cross section

B

y(cm)

_

m+ →e+ne nm

W(e+) ∝ 1 + A cos q

  • Passive polarimeter with
    • Al muon stopper
    • Left/Right positron counters
    • simple analysis and systematics
active muon stopoper
Active muon stopoper
  • Identification of muon stopping point/ decay vertex
  • Measurement of positron energy Ee+ and angle qe+
  • Large positron acceptance of nearly 4p
  • Larger analyzing power
  • Higher sensitivity
  • Lower BG in positron spectra
  • Parallel plate stopper with
  • Gap wire chambers

Number of plates 31

Plate material Al, Mg or alloy

Plate thickness ~ 2 mm

Plate gap ~ 8 mm

Ave. density 0.24 rAl

m+ stop efficiency ~ 85%

  • Small systematics for

L/Re+ asymmetry measurement

  • Fit for p0fwd/bwd measurement
  • Simple structure
tracking system
Tracking system
  • E246 J-PARC E06
  • C0 (cylindrical) and C1(planer) are GEM chambers
rad hardness test of mppc
Rad.hardness test of MPPC
  • MPPC 400 pixel type
  • Irradiation of up to 36 Gy
  • Increase of leakage current

proportional to dose

beam halo simulation
Beam halo simulation
  • GEANT4 simulation
  • 10 cm-f BeO degrader + 6 cm-fTarget

K+ flux distribution

p+

m+

e+

n

csi tl readout
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
apd readout of csi tl
APD readout of CsI(Tl)
  • E246 CsI(Tl)
  • 5 x 5mm APD
  • CR measurement
  • 1.5 ms width
tracking system alignment
Tracking system alignment

Use of a collimator system

csi tl alignment
CsI(Tl) alignment
  • Use of K+ →p+p0 with back to back kinematics

azimuthal rotation

two tilt angles

precession patterns due to misalignments
Precession patterns due to misalignments

- A kind of normalization -

@q = 0o

er=1o

dr=1o

ez=1o

dz=1o

misalignment analysis
Misalignment analysis
  • Time-integrated asymmetry function
  • Effects of ez and er vanish.
  • q0 determination event-by-event

using Km3 form factors.

  • Ambiguity of q0 determination

is not problematic.

q 0 dependence of the asymmetry
q0 dependence of the asymmetry

N

PT

p0-fwd

p0-bwd

dz=5o

dr=5o

correction for decay plane rotation
Correction for decay plane rotation
  • Two rotation angles of qz and qr
  • Relation: dPT ~ 0.5 <qz>, ~ 0.5 <qr>
  • PTwill be corrected for <qz> and <qr>
    • <qr> isfwd/bwd cancelling, but
  • <qz> isnot fwd/bwd cancelling.
  • Statistical error of the correction
  • d<qz> = s(qz)/√Ntotal
  • dPT(<qz>) ≪dPTstat ~ 10-4

qz distribution in E246

<qz>= -0.004±0.12 mr

-1 0 +1

0

data symmetrization
Data symmetrization

- Suppression of systematic errors -

  • K+ stopping distribution
    • non-bias cut
    • small loss of events
  • m+ stopping distributions
  • rfwd(r,y,z) ≠rbwd(r,y,z)
  • rfwd(r,y,z) = rbwd(r,y,z)
  • PTfwd = PT + dPT’
  • PTbwd = -PT+ dPT”
  • eliminates systematics
  • in the polarimeter
group members
Group members

: core members (younger people)

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