measurement of luminosity at energy 2.23 gev, 2.4 gev, 2.8...
TRANSCRIPT
Measurement of Luminosityat energy 2.23 GeV, 2.4 GeV, 2.8 GeV and 3.4 GeV
Geng Cong
Center for Particle Physics and TechnologyUniversity of Science and Technology of China
September 3, 2012
Geng Cong (CPPT-USTC) Luminosity September 3, 2012 1 / 14
Outline
Introduction
Measurement with e+e− → e+e−
Measurement with e+e− → γγ
Geng Cong (CPPT-USTC) Luminosity September 3, 2012 2 / 14
Introduction
Luminosity (integrated Luminosity, denoted as L ) is a keyparameter of high energy physics and an important input value ofmany analyses. Precise measurement of Luminosity is desired inany experiments.
In e+e− collider, the precise measurement is always achieved dueto the well-understood QED processes e+e− → (γ)e+e−,e+e− → (γ)γ+γ− and e+e− → (γ)µ+µ−.
For a special physical process, the corresponding events rate isN = L · σ(·ε), where the σ is cross section of the physical processand ε denotes the efficiency. So, conversely, using thewell-understood processes, the Luminosity is determined as:
L =N
σ · ε
Geng Cong (CPPT-USTC) Luminosity September 3, 2012 3 / 14
Measurement with e+e− → e+e−: Event Selections
Tracks
Vr < 1.0cm, |Vz | < 10.0cm
N+ = N− = 1
180− arccos−→P+·−→P−
|P+||P−| < 50
Shower
| cos θ| < 0.8
Eshower > 1.3 GeV for 3.4 GeVEshower > 1.0 GeV for 2.8 GeVEshower > 0.8 GeV for 2.4 GeVEshower > 0.7 GeV for 2.23 GeV
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Generators and Results
Two generators, Babayaga and Bhwide, are used to generate MC events ofe+e− → e+e−. The check by Bhwide is in progress.
2.23 GeV 2.4 GeV 2.8 GeV 3.4 GeVnumber of events 706237 785791 629424 193949
cross section (nb) 818.3 708.1 521.1 353.9Babayga efficiency (%) 32.8 32.5 32.2 31.7
Luminosity (pb−1) 2.631 3.415 3.751 1.729
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Comparisons between data (Red) and MC (Black)
)
(eθcos
0.8 0.6 0.4 0.2 0 0.2 0.4 0.6 0.80
2000
4000
6000
8000
10000
12000
14000
16000
)+
(eθcos
0.8 0.6 0.4 0.2 0 0.2 0.4 0.6 0.80
2000
4000
6000
8000
10000
12000
14000
16000
Acollinearity
0 1 2 3 4 5 60
5000
10000
15000
20000
25000
30000
180− arccos−−→Pe+ ·−−→Pe−
|Pe+ ||Pe− |
φ∆
50 40 30 20 10 0 10 20 30 40 50
1
10
210
310
410
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Momentum and Energy: data (Red) and MC (Black)
) (GeV)
momentum (e
1 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.80
5000
10000
15000
20000
25000
) (GeV)+
momentum (e
1 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.80
5000
10000
15000
20000
25000
30000
E
1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.90
2000
4000
6000
8000
10000
12000
14000
E
1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.90
2000
4000
6000
8000
10000
12000
14000
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Check by Bhwide
)
(eθcos
0.8 0.6 0.4 0.2 0 0.2 0.4 0.6 0.80
2000
4000
6000
8000
10000
12000
14000
16000
)+
(eθcos
0.8 0.6 0.4 0.2 0 0.2 0.4 0.6 0.80
2000
4000
6000
8000
10000
12000
14000
16000
Acollinearity
0 1 2 3 4 5 60
5000
10000
15000
20000
25000
30000
φ∆
50 40 30 20 10 0 10 20 30 40 50
1
10
210
310
410
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Measurement with e+e− → γγ: Event Selections
Shower
| cos θ| < 0.8
Eshower > 1.3 GeV for 3.4 GeVEshower > 1.0 GeV for 2.8 GeVEshower > 0.8 GeV for 2.4 GeVEshower > 0.7 GeV for 2.23 GeV
Nshower = 2
180− arccos−→P1·−→P2
|P1||P2| < 50
−20 < 180− |φ1 − φ2| < 40
Tracks
Vr < 1.0cm, |Vz | < 10.0cm
Ntrack = 0
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e+e− → e+e− and e+e− → γγ
Without taking into account the number of tracks in MDC.
φ∆
50 40 30 20 10 0 10 20 30 40 500
2000
4000
6000
8000
10000
12000
14000
16000
18000
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Results
Babayaga is used to generate MC events of e+e− → γγ.
2.23 GeV 2.4 GeV 2.8 GeV 3.4 GeVnumber of events 81222 91036 73041 22694
cross section (nb) 56.07 48.52 35.69 24.24Babayga efficiency (%) 55.0 54.9 54.5 53.8
Luminosity (pb−1) 2.634 3.418 3.755 1.740
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Comparisons between data (Red) and MC (Black)
θcos
0.8 0.6 0.4 0.2 0 0.2 0.4 0.6 0.80
200
400
600
800
1000
Acollinearity
0 1 2 3 4 5 60
200
400
600
800
1000
1200
1400
1600
1800
φ∆
10 8 6 4 2 0 2 4 6 8 10
10
210
310
E
1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.90
500
1000
1500
2000
2500
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Another generator: Radgg
Radgg generate MC events with full geometric coverage. Efficiency is 6.7% andcross section is 210 nb. The calculated luminosity is 1.613 pb−1.
φ∆
10 8 6 4 2 0 2 4 6 8 10
10
210
310
Acollinearity
0 1 2 3 4 5 60
200
400
600
800
1000
1200
1400
1600
1800
θcos
0.8 0.6 0.4 0.2 0 0.2 0.4 0.6 0.80
200
400
600
800
1000
1200
1400
1600
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Summary
2.23 GeV 2.4 GeV 2.8 GeV 3.4 GeVLuminosity(e+e− → e+e−) (pb−1) 2.631 3.415 3.751 1.729Luminosity(e+e− → γγ) (pb−1) 2.634 3.418 3.755 1.740difference 0.1% 0.1% 0.1% 0.6%Radgg (pb−1) 2.464 3.202 3.517 1.613online (pb−1) 1.466 2.341 3.099 1.658
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