STATUS OF DVCS ANALYSIS FROM E1-6 DATA
Collaboration meeting 30.03.2017
A. Movsisyan, H. Avakian, S. Pisano
INFN-Ferrara
2
Introduction & Motivation
e e’
p p’
𝛄
Measurement of DVCS Cross Section,via detection of final state proton p’ and lepton e’.
Large statistics & broad kinematic coverage => large coverage of Φ acceptance.
Data collected in 2001-2002.Beam energy 5.754 GeV5cm long liquid hydrogen targetAverage beam polarization 70%
E1-6 experiment:epγep & epγ
spatial distributions of calculated photons
Aram Movsisyan, DPWG meeting 30.03.2017
3
Event Selection (ep (1𝛄) (2𝛄) sample)Primary selection - Events with exactly on 1 negative track with the id = 11,
1 positive track, any number of neutral clusters
Electron identification - EC fiducial cuts CC fiducial cuts DC fiducial cuts CC matching CC efficiency Requirements on Calo response
Proton identification - DC fiducial cuts Requirement on reconstructed ToF mass.
Requirements on event vertex
Photon identification - EC fiducial cuts Requirement on EC time. Spatial separation from charged tracks on EC. Minimum energy deposition in Calo.
Corrections Energy loss correction for electrons & protons Momentum & angle corrections for electrons Energy correction for photons
Aram Movsisyan, DPWG meeting 30.03.2017
4
Exclusive pions (ep(2𝛄) sample)Exclusive Pion Selection: 1 electron, 1 proton & 2 photons
Kinematic requirements:
MC is normalized to Data with the scale factor for
Same scale factor is used to evaluate exclusive pion contribution in DVCS process: ep + ep𝛄 sample
Aram Movsisyan, DPWG meeting 30.03.2017
W
2> 4 [GeV
2]
� t < 0.52 [GeV
2]
� 0.05 < M
2X(epX) < 0.09 [GeV
2]
Pele. > 0.7 [GeV ]
P⇡0> 2.5 [GeV ]
Sector(�1) = Sector(�2)
N
Data⇡0
0,1� (x,Q2,�t,�) =
N
Data⇡0
N
MC⇡0
N
MC0,1� (x,Q
2,�t,�)
NData⇡0
NMC⇡0
=9529
135217
5Aram Movsisyan, DPWG meeting 30.03.2017
Exclusive pions (ep(2𝛄) sample)Data - MC comparison exclusive 𝜋0:
]2 [GeV2Q1 2 3 4 50
50
100
150
200
250
300
350
400
Bjx0.1 0.2 0.3 0.4 0.5 0.60
50
100
150
200
250
300
[rad]φ2− 0 20
50100150200250300350400450
]2 [GeV2W4 6 8 100
50
100
150
200
250
300
350
]2-t [GeV0 0.2 0.4 0.60
50
100
150
200
250
]2(epX) [GeV2XM
0.05− 0 0.050
50
100
150
200
250
6Aram Movsisyan, DPWG meeting 30.03.2017
Exclusive photons (ep𝛄 sample)Data - MC comparison exclusive photons:
W 2 > 4 [GeV 2]
0.07 < �t < 0.52 [GeV 2]
|M2X(epX)| < 0.08 [GeV 2]
Pele. > 0.7 [GeV ]
t < tmin
✓�calc. > 2�
[GeV]γE0 1 2 3 4 5 60
200
400
600
800
1000
1200
1400
1600
1800
2000
2200
Data - MC
[GeV]γE0 1 2 3 4 5 60
200
400
600
800
1000
1200
1400
1600
1800
2000
2200
Data - MC
Expected photons within geometrical accepteanceData
0πExclusive DVCSMC sum
[GeV]caloE0.2 0.4 0.6 0.8 1 1.2
0.22
0.24
0.26
0.28
0.3
0.32
0.34
s.f - from e16 electrons
s.f - from CLAS-NOTE 2013-004, Simonyan, Stepanyan
s.f - from CLAS-NOTE 2013-004, Simonyan, Stepanyan
Sampling fraction
7Aram Movsisyan, DPWG meeting 30.03.2017
Exclusive photons (ep𝛄 sample)Data - MC comparison exclusive photons: (exclusive 𝜋0 , DVCS , MC sum )
]2 [GeV2Q1 2 3 4 50
200
400
600
800
1000
1200
Bj.x0.1 0.2 0.3 0.4 0.5 0.60
200
400
600
800
1000
[rad]φ2− 0 20
200
400
600
800
1000
1200
]2 [GeV2W4 6 8 100
200
400
600
800
1000
]2-t [GeV0 0.2 0.4 0.60
100
200
300
400
500
600
700
800
]2(epX) [GeV2XM
0.05− 0 0.050
200
400
600
800
1000
8
DVCS (ep + ep𝛄 sample)Exclusive Event Selection: 1 electron, 1 proton & 0 or 1 photon
Kinematic requirements:
xBj 0.15-0.17 0.17-0.19 0.19-0.21 0.21-0.23 0.23-0.25 0.25-0.27 0.27-0.29 0.29-0.32 0.32-0.35 0.35-0.40 0.40-0.55
-t 0.07-0.16 0.16-0.22 0.22-0.28 0.28-0.35 0.35-0.43 0.43-0.52
Statistics:
739647 events
Aram Movsisyan, DPWG meeting 30.03.2017
W 2 > 4 [GeV 2]
0.07 < �t < 0.52 [GeV 2]
|M2X(epX)| < 0.08 [GeV 2]
Pele. > 0.7 [GeV ]
t < tmin
✓�calc. > 2� [rad]φ
3− 2− 1− 0 1 2 3
5000
10000
15000
20000° > 2.0 calc.γθ° > 2.2 calc.γθ° > 2.5 calc.γθ° > 2.8 calc.γθ° > 3.0 calc.γθ
9
DVCS (ep + ep𝛄 sample)Data - MC comparison (exclusive 𝜋0 , DVCS , MC sum):
Aram Movsisyan, DPWG meeting 30.03.2017
[GeV]lep.P1 2 30
5000
10000
15000
20000
25000
30000
[deg]lep.θ20 30 40 50 600
2000400060008000
1000012000140001600018000
[deg]prot.θ0 20 40 600
2000400060008000
1000012000140001600018000200002200024000
[cm]prot.Zvtx10− 8− 6− 4− 2− 00
2000
4000
6000
8000
10000
12000
14000
[GeV] clac.γE2 3 4 50
5000
10000
15000
20000
25000
30000
[deg] clac.γθ0 10 20 300
10000
20000
30000
40000
50000
10
DVCS (ep + ep𝛄 sample)Data - MC comparison (exclusive 𝜋0 , DVCS , MC sum):
Aram Movsisyan, DPWG meeting 30.03.2017
]2 [GeV2Q1 2 3 4 50
5000
10000
15000
20000
25000
Bj.x0.1 0.2 0.3 0.4 0.5 0.60
2000400060008000
10000120001400016000180002000022000
[rad]φ2− 0 20
2000400060008000
1000012000140001600018000200002200024000
]2 [GeV2W4 6 8 100
2000400060008000
10000120001400016000180002000022000
]2-t [GeV0 0.2 0.4 0.60
2000
4000
6000
8000
10000
12000
]2(epX) [GeV2XM
0.05− 0 0.0502000
400060008000
10000
12000140001600018000
11
DVCS (ep + ep𝛄 sample)Data - MC comparison (exclusive 𝜋0 , DVCS , MC sum):
Aram Movsisyan, DPWG meeting 30.03.2017
[rad]φ2− 0 20
200
400
600
800
1000
[rad]φ2− 0 20
200400600800
10001200140016001800200022002400
[rad]φ2− 0 20
500
1000
1500
2000
2500
3000
[rad]φ2− 0 20
500
1000
1500
2000
2500
3000
[rad]φ2− 0 20
500
1000
1500
2000
2500
3000
[rad]φ2− 0 20
500
1000
1500
2000
2500
[rad]φ2− 0 20
500
1000
1500
2000
2500
[rad]φ2− 0 20
500
1000
1500
2000
2500
3000
[rad]φ2− 0 20
500
1000
1500
2000
2500
[rad]φ2− 0 20
500
1000
1500
2000
2500
[rad]φ2− 0 20
200
400
600
800
1000
1200
1400
12
DVCS (ep + ep𝛄 sample)Data - MC comparison (exclusive 𝜋0 , DVCS , MC sum):
Aram Movsisyan, DPWG meeting 30.03.2017
]2-t [GeV0 0.2 0.4 0.60
200
400
600
800
1000
]2-t [GeV0 0.2 0.4 0.60
200400600800
1000120014001600180020002200
]2-t [GeV0 0.2 0.4 0.60
200400600800
10001200140016001800200022002400
]2-t [GeV0 0.2 0.4 0.60
200400600800
10001200140016001800200022002400
]2-t [GeV0 0.2 0.4 0.60
200400600800
1000
12001400160018002000
]2-t [GeV0 0.2 0.4 0.60
200
400
600
800
1000
1200
1400
1600
]2-t [GeV0 0.2 0.4 0.60
200
400
600
800
1000
1200
1400
]2-t [GeV0 0.2 0.4 0.60
200
400
600
800
1000
1200
1400
1600
1800
]2-t [GeV0 0.2 0.4 0.60
200
400
600
800
1000
1200
1400
]2-t [GeV0 0.2 0.4 0.60
200
400
600
800
1000
1200
1400
1600
]2-t [GeV0 0.2 0.4 0.60
200
400
600
800
1000
1200
[rad]φ0 1 2 3 4 5 6
1−10
1
10
= 1.49892Q = 0.1623Bjx
-t = 0.1105
bin_1 0.07 < -t < 0.16
[rad]φ0 1 2 3 4 5 6
1−10
1
10
= 1.49822Q = 0.1625Bjx
-t = 0.1869
bin_1 0.16 < -t < 0.22
[rad]φ0 1 2 3 4 5 6
1−10
1
10
= 1.49982Q = 0.1625Bjx
-t = 0.2485
bin_1 0.22 < -t < 0.28
[rad]φ0 1 2 3 4 5 6
1−10
1
10 = 1.50002Q = 0.1624Bjx
-t = 0.3135
bin_1 0.28 < -t < 0.35
[rad]φ0 1 2 3 4 5 6
1−10
1
10 = 1.49632Q = 0.1618Bjx
-t = 0.3898
bin_1 0.35 < -t < 0.43
[rad]φ0 1 2 3 4 5 6
1−10
1
10
bin_1 0.43 < -t < 0.52
= 1.49952Q = 0.1623Bjx
-t = 0.4722
bin_1 0.43 < -t < 0.52
13
DVCS (ep + ep𝛄 sample) X-section
BHKM 2016
Aram Movsisyan, DPWG meeting 30.03.2017
Bin1
0.15 < xBj < 0.17
[rad]φ0 1 2 3 4 5 6
3−10
2−10
1−10
bin_21 0.07 < -t < 0.16
[rad]φ0 1 2 3 4 5 6
3−10
2−10
1−10
bin_21 0.16 < -t < 0.22
[rad]φ0 1 2 3 4 5 6
3−10
2−10
1−10
= 3.52782Q = 0.4115Bjx
-t = 0.2610
bin_21 0.22 < -t < 0.28
[rad]φ0 1 2 3 4 5 6
3−10
2−10
1−10
= 3.62162Q = 0.4233Bjx
-t = 0.3186
bin_21 0.28 < -t < 0.35
[rad]φ0 1 2 3 4 5 6
3−10
2−10
1−10
= 3.68952Q = 0.4349Bjx
-t = 0.3912
bin_21 0.35 < -t < 0.43
[rad]φ0 1 2 3 4 5 6
3−10
2−10
1−10
bin_21 0.43 < -t < 0.52
= 3.77102Q = 0.4483Bjx
-t = 0.4757
bin_21 0.43 < -t < 0.52
14
DVCS (ep + ep𝛄 sample) X-section
BHKM 2016
Aram Movsisyan, DPWG meeting 30.03.2017
Bin21
0.40 < xBj < 0.55, ✓ < 34�
15
Comparison with Published Results
Figure 45: Kinematic coverage of the data and binning: Q2 (left) and ≠t (right) as a function ofxB. We defined 21 (Q2, xB) bins using limits in xB and ◊e, and 9 t bins.
xB ◊e (deg) % of the datasetbin 1 0.1 – 0.14 21 – 45 6.96%bin 2 0.14 – 0.17 21 – 25.5 5.48%bin 3 0.14 – 0.17 25.5 – 45 5.94%bin 4 0.17 – 0.2 21 – 25.5 6.48%bin 5 0.17 – 0.2 25.5 – 45 7.43%bin 6 0.2 – 0.23 21 – 27 7.89%bin 7 0.2 – 0.23 27 – 45 6.57%bin 8 0.23 – 0.26 21 – 27 6.69%bin 9 0.23 – 0.26 27 – 45 6.77%
bin 10 0.26 – 0.29 21 – 27 5.16%bin 11 0.26 – 0.29 27 – 45 5.90%bin 12 0.29 – 0.32 21 – 28 4.27%bin 13 0.29 – 0.32 28 – 45 4.19%bin 14 0.32 – 0.35 21 – 28 3.12%bin 15 0.32 – 0.35 28 – 45 3.20%bin 16 0.35 – 0.38 21 – 28 2.33%bin 17 0.35 – 0.38 28 – 45 2.50%bin 18 0.38 – 0.42 21 – 28 2.14%bin 19 0.38 – 0.42 28 – 45 2.40%bin 20 0.42 – 0.58 21 – 33 2.38%bin 21 0.42 – 0.58 33 – 45 2.20%
Table 4: 21 bins in the (Q2, xB) plane defined using xB and ◊e.
≠t (GeV2) % of the dataset0.09 – 0.13 11.57%0.13 – 0.18 12.91%0.18 – 0.23 11.21%0.23 – 0.3 12.13%0.3 – 0.39 11.38%0.39 – 0.52 11.19%0.52 – 0.72 10.84%0.72 – 1.1 10.74%1.1 – 2. 8.03%
Table 5: 9 bins in t.
53
Binning Used in Published analysis.
kinematic coverage of e16 data with binning Used in Published analysis.
✓ele > 21�
✓ele < 45�
Pele > 0.8 [GeV 2]
✓�calculated > 5�
Kinematic requirements to match the conditions of Published results
Aram Movsisyan, DPWG meeting 30.03.2017
[rad]φ0 1 2 3 4 5 6
1−10
1
10
bin_5 0.07 < -t < 0.16
[rad]φ0 1 2 3 4 5 6
1−10
1
10
bin_5 0.16 < -t < 0.22
[rad]φ0 1 2 3 4 5 6
1−10
1
10
bin_5 0.22 < -t < 0.28
[rad]φ0 1 2 3 4 5 6
2−10
1−10
1
10bin_5 0.28 < -t < 0.35
[rad]φ0 1 2 3 4 5 6
2−10
1−10
1
10bin_5 0.35 < -t < 0.43
[rad]φ0 1 2 3 4 5 6
2−10
1−10
1
10bin_5 0.43 < -t < 0.52bin_5 0.43 < -t < 0.52
16
e16 e1-dvcs
Comparison with Published Results
Aram Movsisyan, DPWG meeting 30.03.2017
Bin5
xBj � [0.17� 0.20]
✓ � [25.5� 45]
[rad]φ0 1 2 3 4 5 6
3−10
2−10
1−10
1bin_17 0.07 < -t < 0.16
[rad]φ0 1 2 3 4 5 6
3−10
2−10
1−10
1bin_17 0.16 < -t < 0.22
[rad]φ0 1 2 3 4 5 6
3−10
2−10
1−10
1bin_17 0.22 < -t < 0.28
[rad]φ0 1 2 3 4 5 6
3−10
2−10
1−10
1bin_17 0.28 < -t < 0.35
[rad]φ0 1 2 3 4 5 6
3−10
2−10
1−10
1bin_17 0.35 < -t < 0.43
[rad]φ0 1 2 3 4 5 6
3−10
2−10
1−10
1bin_17 0.43 < -t < 0.52bin_17 0.43 < -t < 0.52
17
e16 e1-dvcs
Comparison with Published Results
Aram Movsisyan, DPWG meeting 30.03.2017
Bin17
xBj � [0.35� 0.38]
✓ � [28� 45]
18
a. Sufficiently good description of exclusive pion production by MC simulation allows to measure DVCS via detection of only electron and proton.b. Further improvement of Data-MC comparison can be obtained by improved particle ID and implementation of radiative corrections.c. Preliminary results are consistent with published CLAS data.
Thank you!
Conclusion & Outlook
a. Improve data-mc comparison.b. Radiative Corrections. c. Check sensitivity to background subtraction.d. Estimation of systematic uncertainties for the measurement of cross sections.
Aram Movsisyan, DPWG meeting 30.03.2017