Download - Electron identification and shower analysis in ECC T.Toshito (Nagoya Univ.) 8.Mar.2002 EW2002@Nagoya
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Electron identificationand shower analysis in ECC
T.Toshito (Nagoya Univ.)
8.Mar.2002EW2002@Nagoya
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Scanned at Nagoya
8GeV/c
2GeV/c
2GeV/c 2events8GeV/c 4events
More statistics are required!
To achieve low backgroundemulsion plates are used asdoublet.
Test experiment at CERN PS in May 1999
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Test experiment at CERN PS in May 2001
• electron identification
• Analysis of cascade shower
P = 2 and 4GeV/c e enriched π- beam
Interesting energy region for OPERA
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To achieve low background
• Fuji-emulsions stored for about 2 month are refreshed at Nagoya
• Packed in transportation from Nagoya to CERN
• Developed soon after the beam exposure
In-flight
~ 1 tracks/mm2
Emulsion plates are used as singlet.
Virtual erasing
Real erasing
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Beam exposure (May 17th 2000)
• Low density (~ a few 102/cm2) run
to study cascade shower
in low background condition
r(e)~10%(2GeV/c),~2%(4GeV/c)
~10electron
• High density (~103/cm2) run
to study e/π identification
with high statistics
r(e)~60%(2GeV/c),~30%(4GeV/c)
100~300electron
27layer
~5X0
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Net Scan by UTS at Nagoya
• High density Oct. 2000 (one week)
(1cm×1cm)×1 beam spot×27 plates
• Low density Dec. 2000 (one month)
(1cm×1cm)×7 beam spots×27 plates
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Tracking in ECC by two kind of configuration
Cosmic-ray
In-flight
Beam
at CERN
Only Em
Em+Pb…
~300tracks/cm2
~300tracks/cm2
Parallel
Isotropic
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e/π identification (High density)
electron
π
Shower detection
X0=5.6mm in lead
λint=170mm in lead
stopped with shower
stopped without shower
punch through
stopped without shower
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χ2 analysis to measure energy variation
so E0 is treated as a free parameter to minimize chi-square.
1mm 2.3mrad
: separator
In practical experiments incident momentum are unknown,
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Track following of low momentum trackand detection of shower track
Angle < 75mrad
Position < 45μm
tolerance
Pmin~100MeV/c
Shower tracks are searched in these tolerances.
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Results of track following
beam momentum 2GeV/c 4GeV/c
too short (2,3 plates) 16 1
stopped with shower 126 65
punch through 138 194
stopped without shower 202 106
Total incident beam
in fiducial area
482 366
electron-likeχ2analysis
χ2analysis
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χ2 for punch through
Data and pure πMCagree very well
No interacting π
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Momentum measurement by multiple coulomb scattering for punch through tracks
26% error
29% error
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χ2 for stopped tracks
Mixture of electron interacted π
Data and MCagree very well
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e-like : shower + negative chi-square
Comparison with cherenkov counter
278 events 2GeV/c
126 events 4GeV/cAccording to MC
Efficiency 88% mis-id Prob. 6% @2GeV/cEfficiency 91% mis-id Prob. 4% @4GeV/c
Installed in the upstream of ECC to monitor e/π ratio.
2GeV/c 4GeV/c
ECC 1.42±0.17 0.41±0.05
cherenkov 1.46±0.11 0.32±0.03
e/π ratio
Consistent
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Performance of electron identification in ECC iswell understood based on high statistics experimental data.
Low density run to study cascade shower
next
Data and MC agree very well in Δχ2.
e/π ratio measured by ECC and cherenkov counteragree very much.
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Analysis of cascade shower (Low density)
• Energy reconstruction
by counting track segments
14 electron events @2GeV/c14 electron events @4GeV/c detected in low density sample
Detection efficiency is estimated as ~ 95%.
Contamination of π is estimated as ~ 2 events at most.
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Counting track segments in horn
2GeV/c
4GeV/c
x
y
Determined as containing 68% @ 4GeV
Δθbeam<250mrad
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Estimation of background
At random volume
Track segments fromanother electron andinteraction are seen.
Random background~1track/mm2
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ResultsN
umbe
r of
eve
nts
Num
ber
of e
vent
s
Number of segments
Number of segments
DATA(shower)
DATA(B.G.)
MC(shower)+DATA(B.G.)
average 51
r.m.s. 14
average 94
r.m.s. 18
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Summary• electron identification
278 e-like events @ 2GeV
126 e-like events @ 4GeV
Efficiency ~90% mis-id Prob. ~5%
• Analysis of cascade shower
14 electrons @ 2GeV
14 electrons @ 4GeV
E (number of segments)∝These performances can be improved in lower background condition.
E(GeV)
ΔE
E~
0.4
@ a few GeV
Refresh in the underground Lower track density