Progress Report to PAC3
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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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Problem assigned by pac1

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


Problem assigned by pac1

Statistical sensitivity estimate


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.


Problem assigned by pac1

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


Problem assigned by pac1

Systematic error estimate


Problem assigned by pac1

E246 systematic errors

Source of ErrorS12 fwd/bwddPTx 104e+ counter r-rotationxo0.5e+ counter z-rotationxo0.2e+ counter f-offsetxo2.8e+ counter r-offsetoo<0.1e+ counter z-offsetoo<0.1m+ counter f-offsetxo<0.1MWPC f-offset (C4)xo2.0CsI misalignmentoo1.6B offset (e)xo3.0B rotation (dx)xo0.4B rotation (dz)xx5.3K+ stopping distributionoo<3.0m+ multiple scatteringxx7.1Decay plane rotation (qr)xo1.2Decay plane rotation (qz)xx0.7Kp2 DIF backgroundxo0.6K+ DIF backgroundox< 1.9Analysis--3.8Total11.4

  • 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


Problem assigned by pac1

R&D of detector upgrade


Problem assigned by pac1

Upgraded elements


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


Problem assigned by pac1

Collaboration/Funding/Beamline


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


Problem assigned by pac1

END of Slides


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


    Spin relaxation rate

    Spin relaxation rate


    Tracking system

    Tracking system

    • E246 J-PARC E06

    • C0 (cylindrical) and C1(planer) are GEM chambers


    Tracking performance

    Tracking performance


    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


    E asymmetry due to polarimter misalignmnet

    e+ asymmetrydue topolarimter misalignmnet


    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)


    Trigger rate reduction

    Trigger rate reduction


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