Nestle - Zaka (40)
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Transcript of Nestle - Zaka (40)
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8/8/2019 Nestle - Zaka (40)
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Mar.20-23.2010 Toshiyuki Iwamoto (ICEPP) JPS 2010 Spring meeting, Okayama University
MEGQeK Run2009
MEG
Contents QeK search & MEGExperiment MEG Run2009 and detectorperformance in 2009 Analysis procedure & the current status Prospects in 2010
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Mar.20-23.2010 Toshiyuki Iwamoto (ICEPP) JPS 2010 Spring meeting, Okayama University
Background
Accidental background is our main background
Q eK searchSignal
Positive Q decay at rest
Clear two body kinematics
Back to back (180)
EeEK=52.8MeV Coincident (Te=TK)
KKK HH.HH eeeacc tEEB w22 )()(
K BGe+ BG
Michel positron Random K
.etcKKpee
,KRRQ peRRQ pe
Good detector performance is essentialHigh rate e+ measurement with intense Q beam
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Mar.20-23.2010 Toshiyuki Iwamoto (ICEPP) JPS 2010 Spring meeting, Okayama University
MEGExperimentTarget sensitivity : Br(QeK)~10-13
Current best limit : 1.2x10-11by MEGA experiment
Worlds most intensecontinuous muon beam
MEG detector1.3MW PSI Proton cyclotron
Physics DAQ has started since 2008
The result of Run2008 : Br(Q+e+K)2.8x10-11(90%C.L.)
(Sensitivity was 1.3x10-11)(to be published, cf. J.Adam et al,MEGCollaboration, arXiv:0908.2594)
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Mar.20-23.2010 Toshiyuki Iwamoto (ICEPP) JPS 2010 Spring meeting, Okayama University
MEG Run2009 Full DCH modules worked well LXe light yield as good as expected by prototype
Physics run condition
6.3Hz trigger rate
38TB in total including calibration data
Physics run2009 was shorter than run2008
Apr
Jul
Oct
Jan
2010
PSI accelerator shutdown
Other experimentDCH modificationMaintenance work for MEG
Detector setupCalibrationWaveform digitizer update
Physics run ( 2 months )
PSI accelerator shutdown
2.9x107 Q/s beam intensity
In total, 6.5x1013 Q stoppedon target
Three daysmaintenance
Run2009
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Mar.20-23.2010 Toshiyuki Iwamoto (ICEPP) JPS 2010 Spring meeting, Okayama University
Positron spectrometer Discharge problem of positron tracker (drift chamber, DCH) happened in 2008.The
problem was finally figured out in HV distribution cards after intensive works
All DCHs were repaired before physics DAQ in 2009, and the detection efficiency(14% 40%) and performance of DCH was much improved.
Hit map 2008
2009
Ue
1811mrad
Je
108mrad
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Mar.20-23.2010 Toshiyuki Iwamoto (ICEPP) JPS 2010 Spring meeting, Okayama University
Photon Detector (XEC
) Light yield of liquid xenon in 2008 was improving during physics run by purification Gaseous purification was done for all xenon before physics run in 2009, and the
light yield in 2009 was as good as expected by our prototype
Light yield in 2009 had been stable during physics run without any purification.
Run2008gas&liquidpurification Run2009
Light Yield Energy resolution
Calibration is not finalized yet in 2009, butcomparable resolution is already achieved
signal
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Mar.20-23.2010 Toshiyuki Iwamoto (ICEPP) JPS 2010 Spring meeting, Okayama University
2009 Detectorperformance2008 2009
(preliminary)
Gamma Energy (%) 2.0 (w>2cm)
Gamma Timing (psec) 80 >67
Gamma Position (mm) 5(u,v)/6(w)
Gamma Efficiency (%) 63
e+ Timing (psec)
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Mar.20-23.2010 Toshiyuki Iwamoto (ICEPP) JPS 2010 Spring meeting, Okayama University
Analysis procedure Preselection: ~20% of all events
Blind analysis to avoid any bias
TeK(-1ns
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Maximum likelihood fitting
PDF preparation (S, R, B) : PDF for (QeK, RMD, Background)
Product ofPDFs for the five observables
(EK, Ee, teK, UeK and JeK) Fitting parameters (NBG, NRMD, NSignal)
All figures shown here are run2008 results
All PDFs are being prepared now for run2009
),(!
exp),,(
1
BN
NR
N
NS
N
N
N
NNNNL BGRMD
sigN
iobs
NN
BGRMDsig
obsobs
!!
Blue: AllPink: BGRed: RDGreen: Signal
EKE
e
TeK
UeK
JeK
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Mar.20-23.2010 Toshiyuki Iwamoto (ICEPP) JPS 2010 Spring meeting, Okayama University
Normalization
Count the number of detectedMichel positrons (Michel trigger) NeRRobtained simultaneously with
the signal (MEG trigger)
The upper limit on BR(Q+e+K) iscalculated by normalizing Nsig tothe NeRR
Independent of instantaneousbeam rate and insensitive topositron acceptance andefficiency
KKKKK II
I
I
IKQ
e
g
e
CH
e
CH
vev
TC
e
TC
vev
trig
e
trig
vev
E
vev
vev
sig
AA
A
P
fe
11)( vvvvvv!p
Theory
Resolution
Selectionefficiency
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Run2009 PDF preparation
We are still calibrating the detector and optimizing algorithms
Several times, re-processing for preselected events will be done after certainimprovement
Hopefully in June 2010, well open the blind box, and do the final analysis
Target: publish the result at this summer conference
EK sideband data PDF forEK BG
Ee data PDF forEe BG
TeK data PDF for TeK signal
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Mar.20-23.2010 Toshiyuki Iwamoto (ICEPP) JPS 2010 Spring meeting, Okayama University
Run 2010
Detector performance should be improved by reconstructionalgorithm and calibration methods
Positron beam ( efficiency, resolution )
DCH noise removal ( resolution )
Gamma energy (1.5%W at the best point)
Trigger efficiency ( TC fiber counter)
Optimization of beam stopping position
Data statistics in 2010 will be 11 times higher than 2008 ( 6months data taking ), and the sensitivity is estimated to be
1.3x10-12.
Three years data taking (2010-2012) will enable us to reach thesensitivity of~10-13 level
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Prospects in 20102008 2009 (preliminary) 2010 (preliminary)
Gamma Energy (%) 2.0 (w>2cm) 1.5 (w>2cm)
Gamma Timing (psec) 80 >67 68
Gamma Position (mm) 5(u,v)/6(w)
Gamma Efficiency (%) 63
e+ Timing (psec)
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Optimization of beam stopping
position
Degrader thickness (300Qm 200Qm) in 2009 to match6% air contamination in COBRA by means of MCstudy.
Strong asymmetry was observed by TCupstream/downstream hit map
Beam test for optimization of the degrader is planned
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TC modification
Plastic scintillating fiber +APD ( z measurement )
To provide precise z positionfor online trigger
New front-end boards design
S/N ~ 8 (noise~40mV)
Shorter shaping time for trigger(250ns -> 20ns)
TC bars (J
measurement )
207Bi on TC bar center
Better z position calibration
zJ
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Electronics modification
Waveform digitizer (DRS2DRS4)
700MHz ~ 5GHz, 8(+1) channels with 1024storage cells
Eliminate temperature drifts
Linearity improved ( 0~1V )
Timing accuracy below 30ps
Currently being tested
Trigger
Dead time reduction
Dynamic range
Some front face PMTs saturated with input range(0-
1V) -> (0-2V)
Dedicated E trigger
Improved separation between Es and Ks
Direction matching efficiency improvement byusing TC APD information
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PMT gain shift
Problem in photo
cathode production
stage Might be different
mixture at certain
period, too much
alkali?
R 8 Gain Shift vs SKB
0.8
0.8
0.
0.
1
1.0
1.1
1.1
1.2
1
120
223
3
3
1
3
8
3
1032
1112
12
8
13
1
1
3
1
01
1
3
1
1
1
83
18
1
1
02
1
8
Serial No.
GainShift
2
3
8
SKB
GainShift
SKB
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Mar.20-23.2010 Toshiyuki Iwamoto (ICEPP) JPS 2010 Spring meeting, Okayama University
Ghost pulse problemR
Ghost pulse2% @ 2 GHz
After sampling a pulse, some residual chargeremains in the capacitors on the next turn andcan mimic wrong pulses
Solution: Clear before write
write clear
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Mar.20-23.2010 Toshiyuki Iwamoto (ICEPP) JPS 2010 Spring meeting, Okayama University
UeK
, JeK
Opening angle resolution
combination of
positron angle resolution
target position resolution
photon detector position
2008 results