Effect of Backgrounds on L1 CSC
Trigger Performance
D.Acosta
University of Florida
CMS Week, March 2001
1
Darin Acosta
Unbiased Min Bias Data Sample
Created an unweighted minimum bias data sample and
stored in a DB at Florida
50K events (not enough for high PT rates)
Pythia event generation
CMSIM 121 hit generation
ORCA_4_4_0 reconstruction
“Head” of L1CSC trigger simulation
Useful for studies on trigger rate from punch-through
Also generated a “signal” sample of neutron background
hits, with 17.3 min. bias events piled per b.x.
Neutron hits seem to be at center of chamber…
CMS Week, March 2001
2
Darin Acosta
Neutron Hits in φ
abs(zhit)<750.and.abs(etahit)<1.5
ID
Entries
Mean
RMS
50
2001/02/28 14.50
abs(zhit)<750.and.abs(etahit)>1.6
91
186
0.7884E-01
0.3229E-01
ID
Entries
Mean
RMS
900
800
40
92
3744
0.8845E-01
0.3923E-01
ME1
700
600
30
500
400
20
300
200
10
100
0
0
0.05
0.1
0
0.15
mod(phihit+0.08727,0.017453)
ID
Entries
Mean
RMS
800
0.1
0.15
abs(zhit)>1000.and.abs(etahit)>1.6
80
93
2307
0.8835E-01
0.3909E-01
ID
Entries
Mean
RMS
70
700
94
841
0.8883E-01
0.5978E-01
ME4
60
600
50
500
40
400
30
300
200
20
100
10
0
0
0
0.05
0.1
0.15
mod(phihit+0.08727,0.017453)
CMS Week, March 2001
0.05
mod(phihit+0.08727,0.017453)
abs(zhit)>1000.and.abs(etahit)<1.5
900
Low η
0
3
High η
0
0.05
0.1
0.15
mod(phihit+0.08727,0.017453)
Darin Acosta
Neutron Hits in η
2001/02/28 14.57
abs(zhit)<750
1000000
3978
1.969
0.3081
ID
Entries
Mean
RMS
250
200
ME1
150
100
50
0
0.8
1
1.2
1.4
1.6
1.8
2
2.2
2.4
2.6
abs(etahit)
abs(zhit)>1000
1000000
3447
1.526
0.2783
ID
Entries
Mean
RMS
600
500
ME4
400
300
200
100
0
1
1.2
1.4
1.6
1.8
2
2.2
2.4
abs(etahit)
CMS Week, March 2001
4
Darin Acosta
2.6
Some Statistics
Neutrons deliver ~800 hits per b.x. at L = 1034
Takes 30 sec per b.x. on 450 MHz Intel
Neutrons alone give 1 LCT per b.x. on average
Correlated anode and cathode trigger primitive somewhere
in CSC system (but usually ME1 or ME4)
May not be correct since hits are centered in chamber
Each min. bias event has 0.03 LCT per collision
17.3 collisions per b.x. 0.6 LCT per b.x. 20 MHz
⇒
CMS Week, March 2001
⇒
5
Darin Acosta
L1 CSC Trigger Rate at L=1034
Trigger Rate (Hz)
2001/03/02 14.19
10 7
Single Muon Rate
L1 TDR (weighted)
No pile-up
10 6
unweighted, ORCA_440
Neutrons + pile-up
10 5
~40% more rate than weighted
samples
10 4
10
Di-muon rate < 35 kHz at
95%CL
3
1
CMS Week, March 2001
10
10
Ptcut (GeV/c)
6
2
“Loose” track definition
applied as in L1 TDR
Darin Acosta
Single Muon Trigger Efficiency
2001/03/03 14.25
Efficiency
Efficiency
No pile-up or neutrons
1
0
0.8
min.bias pile-up and neutrons
1
0
0.8
10
20
10
20
40
40
60
60
0.6
0.6
0.4
0.4
0.2
0.2
0
2001/03/03 14.23
0
20
40
60
80
100
0
0
20
40
PTgen (GeV/c)
80
100
PTgen (GeV/c)
Same as in L1 TDR
CMS Week, March 2001
60
10% drop in efficiency (neutrons?)
7
Darin Acosta
Improvement in L1 CSC Trigger
Performance
D.Acosta
University of Florida
CMS Week, March 2001
8
Darin Acosta
PT Assignment
Re-tuned the region 1.2<η
η<1.6
φ bending changed with new 3D field map used in CMSIM 121
Added 1-bit of z information to PT LUT
So-called “F/R” bit, which tells whether CSC is in front or in
rear (chambers are overlapping in each station)
Mostly sensitive to ME1 (25% variation in ∆φ12)
Improves PT resolution from 26% to 22%
HW solution is possible (2MB → 4MB SRAM)
Still to study:
Use of φ bend angle (for DT/CSC overlap and CSC region)
Nonlinear ∆φ binning for better precision in same size LUT
Requires UCLA to introduce more LCT patterns and to improve
φ resolution in ORCA simulation
CMS Week, March 2001
9
Darin Acosta
PT Resolution
PT<35 GeV
1.2<η
η<2.1
Mean
RMS
140
-0.5446E-01
0.2883
42.98 / 43
102.6
-0.5290E-01
0.2557
120
Constant
Mean
Sigma
100
80
2001/03/05 03.49
Previous
method
60
40
20
0
-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
1/Pt Residual
Mean
RMS
140
-0.1384E-01
0.2669
62.77 / 43
114.4
-0.2046E-01
0.2235
120
Constant
Mean
Sigma
100
80
With F/R
Correction
60
40
20
0
-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1/Pt Residual
CMS Week, March 2001
10
Darin Acosta
1
CSC Trigger Code Status
F/R bit addition has been added to L1CSCTrigger and
L1CSCTrackFinder packages
Should improve efficiency and rate w.r.t. L1 TDR
PT parameterization has been retuned for CMSIM 121
Problem with CMSIM 121 geometry change in
L1CSCTrigger package has been fixed temporarily
Need a more robust solution to de-couple geometry from
trigger primitive code
Future development of L1CSCTrigger primitives will be
done by J.Mumford (UCLA)
CMS Week, March 2001
11
Darin Acosta