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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Progress Report to PAC3J-PARC E06 Experiment (TREK)Measurement of T-violating Transverse Muon Polarization (PT) in K+→p0m+n DecaysJ. ImazatoJuly 6, 2007
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.
K+→p0m+ndecay
are small.Non-zero PTis a signature of T violation.
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
Statistical sensitivity estimate
_
polarization analyzing power : a = AT / PT❷
In determining the sensitivity,❶and❷are separable.
They are shown next step by step.
Positron asymmetry measurement
FoM = AT√Ne+
(cf. 0.27 in E246)
⇒ Detector acceptanceW(Km3) = 1.14 ×10-2
N(Km3) = N(K+)・estop・Br(Km3)・ W(Km3)
= 3.3 × 109 (total E06 good events)
dPT = 6.9 / √N(Km3)
= 1.2 ×10-4
(The effect of Ee+ threshold was partially included in the proposal.)
2005 design
2007 design
( It was 1.0×107 s in the proposal.)
Acc = 6.0 msr %Dp/p
Acc = 4.5 msr %Dp/p
Systematic error estimate
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
S12 and/or
fwd/bwdalmost
all systematics
Old errors
Newcomer
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 ?
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)
PT= 0 and dz = dr= 5o = 87 mr
==> dPT= (2±7)×10-4 for 108 events
Momentum resolutions
Consistency
MC simulation
==> suppression to < 1/10 (<0.002%)
dPT < 10-4
<qz> isnot fwd/bwd cancelling.
qz distribution in E246
<qz>= -0.004±0.12 mr
dPT (<qz>) ≪ 10-4
dPT (<qr>) ~dPTstat&fwd/bwd
≪ 10-4
-1 0 +1
0
measurement is left-right
canceling :
up to small Dr = rfwd - rbwd
m+ stopping
distribution
in the stopper
Dr = rfwd - rbwd
was a few % in E246
dPTshould be < 10-4
R&D of detector upgrade
Upgraded elements
materials
Typical TF precession pattern
Al alloys: A5052, A6063, Mg alloys: AZ31, ZK60, Z6, AM60, AZ91
Cosmic ray test
Energy Timing
st =3ns
Pulse height
spectrum
Pulse shape
20 cm + clear fiber + MPPC
at RCNP
with dose
H- and V-amplitude
correlation
Middle residual
Amplitude vertical
Amplitude horizontal
Residualx(mm)
TOSCA 3D calculation
Collaboration/Funding/Beamline
TRIUMF, Univ. of Montreal
- New participation -
K1.1
at T1, it will become very difficult to
install the frond end of the channel
K1.1-BR
T1
(These are not very different from the estimates in the proposal.)
20091) Spectrometer setup
2) Field mapping
3) Detector setup
4) Beam tuning
2010-11 5) Engineering run, and
6) Data taking
PT ~ [e’/e effect]× 20 = 5 x 10-6× 20 ~ 10-4
-- unless enhanced couplings to leptons!
(I. Bigi, CERN Flavor WS, 2007 )
PAC3
END of Slides
GEANT3 calculation
thickness
800 MeV/c
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
1) ×30 beam intensity,
2) ×10 detector acceptance, and
dPTsyst ~ 0.1 dPTsyst (E246) ~10-4by
1) Precise calibration of misalignments using data
2) Correction of systematic effects
symmetrization
(Estimate of cancellation power using data)
Muon polarimeter and muon field distribution
One-sector view
Cross section
B
y(cm)
_
m+ →e+ne nm
W(e+) ∝ 1 + A cos q
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%
L/Re+ asymmetry measurement
proportional to dose
K+ flux distribution
p+
m+
e+
n
- enough for the beam intensity in Phase 1
Use of a collimator system
azimuthal rotation
two tilt angles
- A kind of normalization -
@q = 0o
er=1o
dr=1o
ez=1o
dz=1o
using Km3 form factors.
is not problematic.
N
PT
p0-fwd
p0-bwd
dz=5o
dr=5o
qz distribution in E246
<qz>= -0.004±0.12 mr
-1 0 +1
0
- Suppression of systematic errors -
: core members (younger people)