Performance of the CLC Minbias Trigger
The CLC consists of two modules (one per side)
covering the interval 3.7 < |η| < 4.7
Each module has 48 Cherenkov counters and PMTs
The Minbias trigger forms coincidences of the
discriminated signals
Tight trigger:
Require at least two hits on each side
Used until June 4
Loose trigger:
Require only one hit per side
In place since June 4
11/14/2001
D. Acosta
I will report only on
this configuration
1
Efficiency of the CLC Minbias Trigger
Many L1 triggers use the CLC in coincidence, so it’s
important to understand its efficiency
Use an orthogonal trigger to tag min bias events,
then measure fraction of events that fire CLC trigger
But there aren’t so many unbiased triggers!
Typical L1 triggers used for this purpose:
L1_CEM0_PT4, L1_CMU0_PT8
L1_CEM4_PT4, L1_CEM8_PT8
L1_CMU1.5_PT1.5, L1_CMU6_PT8
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Estimate of proton loss and non-beam fractions
For events with a hit in both CLC modules:
N ( ∆tCLC > 10 ns)
fraction of tags from losses
f =
Ntot
Events without a hit in either CLC module are
expected to be negligible for hard-core events:
loss
ε hc
mb ≈ 95%
coincidence in both modules
hc
hc
ε side
= ε mb
≈ 97.5% hit in one module
non
⇒ ε CLC
= (1 − 0.975)2 ≈ 0.06%
So f
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non
N (0 hits in both CLC modules)
=
Ntot
D. Acosta
Hits with only bad
times in just one
module are also
included in
numerator
3
Method to unfold trigger efficiencies
Experimentally, we measure a trigger efficiency
from the tagged events as:
ε meas
trig
≡
N trig*tag
N tag
σ trig*tag
=
σ tag
We can extract the CLC hard-core efficiency from:
ε htrig =
ε meas
trig
loss
1 − ftag
− ftagnon
Assume that tagging triggers have negligibly small
acceptance for diffractive scattering
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D. Acosta
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Results from Tracking Triggers
1
Minbias Efficiency from L1 Track Triggers
Level 1 Triggers:
PT3 (Stream I, raw)
PT8 (Stream I, raw)
0.98
PT1.5 (Stream I, raw)
0.99
0.98
1
Efficiency
Efficiency
Minbias Efficiency from L1 Track Triggers
0.99
0.97
0.97
0.96
0.96
0.95
0.95
0.94
0.94
0.93
0.93
0.92
0.92
Level 1 Triggers:
PT4 (Stream B, raw)
PT4 (Stream B, ISOT strip)
PT4 (Zero Bias, raw)
0.91
0.91
x10
0.9
1160 1165 1170 1175 1180 1185 1190 1195 1200
Run Number
2
0.9
1265
June
11/14/2001
PT8 (Stream B, raw)
1270
Sep
D. Acosta
1275
x10
1280
1285
1290
Run Number
2
Oct
5
Results from CEM Triggers
Minbias Efficiency from L1 CEM Triggers
1
1
0.99
Efficiency
Efficiency
Minbias Efficiency from L1 CEM Triggers
0.98
0.98
0.97
0.97
0.96
0.96
0.95
0.95
0.94
0.94
0.99
Level 1 Triggers:
0.93
0.92
0.91
Level 1 Triggers:
0.93
CEM3 (Stream I, raw)
CEM4 (Stream I, raw)
CEM8 (Stream B, raw)
CEM8 (Stream B, raw)
CEM8 (Stream B, ISOT strip)
0.91
2
0.9
1265
June
11/14/2001
CEM4 (Stream B, ISOT strip)
0.92
CEM5 (Stream B, raw)
x10
0.9
1160 1165 1170 1175 1180 1185 1190 1195 1200
Run Number
CEM4 (Stream B, raw)
1270
Sep
D. Acosta
1275
x10
1280
1285
1290
Run Number
2
Oct
6
Results from CMU Triggers
Efficiency
Minbias Efficiency from Stream J (raw data)
1
0.99
0.98
0.97
0.96
0.95
0.94
0.93
Level 1 Triggers:
CMU1.5 PT1.5 (stream J, raw)
0.92
~7% non-collision triggers
CMU6 PT8 (stream J, raw)
0.91
0.9
1200
1220
1240
1260
Aug
11/14/2001
x102
1280
1300
Run Number
Sep
D. Acosta
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Efficiency vs. Highest Track PT
PT4 trigger, Stream B, ISOT strip
TrigEff: MB Efficiency vs. Maximum Track Pt (PT4 Trigger)
TrigEff_Eff_TrackPt_PT4
Nent = 22
1
Mean = 12.03
RMS = 4.605
Under =
0.98
0
Over = 0.9927
Integ = 15.43
0.96
0.94
0.92
0.9
0
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2
4
6
8
10
12
D. Acosta
14
16
18
20
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Efficiency vs. Track Multiplicity
PT4 trigger, Stream B, ISOT strip
TrigEff_Eff_NTrack_PT4
TrigEff: MB Efficiency vs. Number of Tracks (PT4 Trigger)
Nent = 22
Mean = 41.67
RMS = 22.58
Under =
Over =
0
1
Integ = 18.72
1
0.8
0.6
0.4
0.2
0
0
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10
20
30
40
50
D. Acosta
60
70
80
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CLC Loose Minbias Trigger Rate
Loose Min. Bias Rate (Hz)
x 10 2
3500
3000
250 kHz
2500
Prescale:
50K
5Hz
2000
⇒
1500
1000
Sept 14th 2001
Sept 21st 2001
500
Higher proton losses
Oct 5th 2001
0
0
1
2
3
4
5
6
7
Instantaneous Luminosity (1030 cm-2 s-1)
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CLC Tight Minbias Trigger Rate
Tight Min. Bias Rate (Hz)
x 10 2
3500
3000
2500
2000
1500
1000
Sept 14th 2001
Sept 21st 2001
500
εtight ≈ 85%
Oct 5th 2001
0
0
1
2
3
4
5
6
7
Instantaneous Luminosity (1030 cm-2 s-1)
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Conclusions
CLC minbias trigger efficiency has been stable
despite variations in the PMT gain
Efficiency is ~96% for events with a PT>4 track
Actual efficiency depends on hardness of event
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