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Cross Sections, Γγγ’s, and uncertainties for12C and 208Pb
Dustin McNultyUMass
PrimEx Collaborationmcnulty@jlab.org
July 21, 2007
PrimEx Collaboration Jefferson Lab Hall B
12C Yield
(degrees)θ Production Angle, 0π0 0.5 1 1.5 2 2.5 3
)o Y
ield
(per
0.0
20 π
0
0.2
0.4
0.6
0.8
1
1.2
310× C, crystal only)12 Photoproduction Yield (0π
yield + bkgd0πElastic
bkgd0πInelastic s = 97330πTotal
]= 289os:[0,0.30π
Preliminaryelastic range:[0.906,1.086]
(degrees)θ Production Angle, 0π0 0.5 1 1.5 2 2.5 3
’sγ/2
.334
e+12
inci
dent
o
Yie
ld/0
.02
0 π
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1310× C, crystal only)12 Photoproduction Yield (0π
yield0πElastic s = 640040πTotal
]= 5187os:[0,0.30π
Preliminaryelastic range:[0.906,1.086]
.
Dustin McNulty, Collaboration Meeting, July 21, 2007 1
PrimEx Collaboration Jefferson Lab Hall B
12C Efficiencies
Losses (%)
Description 12C
ROC Fastbus Errors 0 �448�
0 �009
Photon Absorption in Target 5 �41
�
0 �02
Best (tdiff) Candidate selection 2 �5 �
0 �3Elasticity Cut:
�
0 �906 � 1 �086�
1 �7 �
0 �3Veto Cut: all flags
�0 � 1 � 2 � 3 �
1 �97
�
0 �12
Branching Ratio π0 � γγ 1 �2 �
0 �03
Total 13 �25
�
0 �4
Table 1: Summary of non-geometric losses.
Dustin McNulty, Collaboration Meeting, July 21, 2007 2
PrimEx Collaboration Jefferson Lab Hall B
Yield Fit for 12C
(degrees)θ Production Angle, 0π0 0.5 1 1.5 2 2.5 3 3.5 4
(degrees)θ Production Angle, 0π0 0.5 1 1.5 2 2.5 3 3.5 4
o Y
ield
/0.0
20 π
0
100
200
300
400
500
600
700
800
900
C, crystal only)12 Photoproduction yield (0π
yield0π Measured •
yield Fit0π------ Calculated
Fit Parameters: 0.0586 ± : 1.910 ncb
0.1584 eV± : 8.246 pb
0.047 rad.±| : 0.9908 φ| 0.398± : 7.2359 bb
/ndf : 190.56 / 1472χ
Preliminary----- Primakoff
----- Nuclear Coherent----- Interference----- Incoherent
.
Dustin McNulty, Collaboration Meeting, July 21, 2007 3
PrimEx Collaboration Jefferson Lab Hall B
208Pb Yield
(degrees)θ Production Angle, 0π0 0.5 1 1.5 2 2.5
)o Y
ield
(per
0.0
20 π
0
100
200
300
400
500
600
700
800Pb, crystal only)208 Photoproduction Yield (0π
yield + bkgd0πElastic
bkgd0πInelastic s = 6610πTotal
]= 75os:[0,0.30π
Preliminaryelastic range:[0.906,1.086]
(degrees)θ Production Angle, 0π0 0.5 1 1.5 2 2.5
’sγ/1
.311
e+12
inci
dent
o
Yie
ld/0
.02
0 π
0
100
200
300
400
500
600
700
800Pb, crystal only)208 Photoproduction Yield (0π
yield0πElastic s = 84430πTotal
]= 4624os:[0,0.30π
Preliminaryelastic range:[0.906,1.086]
.
Dustin McNulty, Collaboration Meeting, July 21, 2007 4
PrimEx Collaboration Jefferson Lab Hall B
208Pb Efficiencies
Losses (%)
Description 208Pb
ROC Fastbus Errors 0 �468�
0 �013
Photon Absorption in Target 5 �92
�
0 �01
Best (tdiff) Candidate selection 1 �1 �
0 �3Elasticity Cut:
�
0 �906 � 1 �086�
1 �7 �
0 �3Veto Cut: all flags
�0 � 1 � 2 � 3 �
1 �97
�
0 �12
Branching Ratio π0 � γγ 1 �2 �
0 �03
Total 12 �34
�
0 �4
Table 2: Summary of non-geometric losses.
Dustin McNulty, Collaboration Meeting, July 21, 2007 5
PrimEx Collaboration Jefferson Lab Hall B
Yield Fit for 208Pb
(degrees)θ Production Angle, 0π0 0.5 1 1.5 2 2.5 3
(degrees)θ Production Angle, 0π0 0.5 1 1.5 2 2.5 3
o Y
ield
/0.0
20 π
0
100
200
300
400
500
Pb, crystal only)208 Photoproduction yield (0π
yield0π Measured •
yield Fit0π------ Calculated
Fit Parameters: 0.0741 ± : 0.831 ncb
0.1646 eV± : 8.263 pb
0.120 rad.±| : 0.9388 φ| 0.492± : 7.6453 bb
/ndf : 168.83 / 1472χ
Preliminary----- Primakoff
----- Nuclear Coherent----- Interference----- Incoherent
.
Dustin McNulty, Collaboration Meeting, July 21, 2007 6
PrimEx Collaboration Jefferson Lab Hall B
Nuc. Coherent Parameter vs. Elasticty Cut and Fit Range
)σ ±Elasticity Cut (0 1 2 3 4 5 6 7 8 9 10
ncY
ield
Fit
Par
amet
er: b
1.5
1.6
1.7
1.8
1.9
2
2.1
2.2
2.3
2.4
2.5C, crystal only)12Elasticity cut Systematic Error Study (
max fit0πθ o2.00
max fit0πθ o2.25
max fit0πθ o2.50
max fit0πθ o2.75
max fit0πθ o3.00
1.0k2.0k2.5k
0.000±0.00
0.073±1.87
0.000±0.00
C, crystal only)12Elasticity cut Systematic Error Study (
Dustin McNulty, Collaboration Meeting, July 21, 2007 7
PrimEx Collaboration Jefferson Lab Hall B
Incoherent Parameter vs. Elasticty Cut and Fit Range
)σ ±Elasticity Cut (0 1 2 3 4 5 6 7 8 9 10
bY
ield
Fit
Par
amet
er: b
0
1
2
3
4
5
6
7
8
9
10C, crystal only)12Elasticity cut Systematic Error Study (
max fit0πθ o2.00
max fit0πθ o2.25
max fit0πθ o2.50
max fit0πθ o2.75
max fit0πθ o3.00
1.0k2.0k2.5k
0.000±0.000.178±7.320.000±0.00
C, crystal only)12Elasticity cut Systematic Error Study (
Dustin McNulty, Collaboration Meeting, July 21, 2007 8
PrimEx Collaboration Jefferson Lab Hall B
φ Parameter vs. Elasticty Cut and Fit Range
)σ ±Elasticity Cut (0 1 2 3 4 5 6 7 8 9 10
(rad
)φ
Yie
ld F
it P
aram
eter
:
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
1.1C, crystal only)12Elasticity cut Systematic Error Study (
max fit0πθ o2.00
max fit0πθ o2.25
max fit0πθ o2.50
max fit0πθ o2.75
max fit0πθ o3.00
1.0k2.0k2.5k
0.000±0.00
0.024±0.970.000±0.00
C, crystal only)12Elasticity cut Systematic Error Study (
Dustin McNulty, Collaboration Meeting, July 21, 2007 9
PrimEx Collaboration Jefferson Lab Hall B
Fit χ2/d.o.f vs. Elasticty Cut and Fit Range
)σ ±Elasticity Cut (0 1 2 3 4 5 6 7 8 9 10
/Ndf
2 χY
ield
Fit
Par
amet
er:
1
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
2C, crystal only)12Elasticity cut Systematic Error Study (
max fit0πθ o2.00
max fit0πθ o2.25
max fit0πθ o2.50
max fit0πθ o2.75
max fit0πθ o3.00
1.0k2.0k2.5k
-0.000±0.00
0.404±1.09-0.000±0.00
C, crystal only)12Elasticity cut Systematic Error Study (
Dustin McNulty, Collaboration Meeting, July 21, 2007 10
PrimEx Collaboration Jefferson Lab Hall B
Γγγ Parameter vs. Elasticty Cut and Fit Range
)σ ±Elasticity Cut (0 1 2 3 4 5 6 7 8 9 10
(MeV
)γγΓ
Yie
ld F
it P
aram
eter
:
7.4
7.6
7.8
8
8.2
8.4
8.6
8.8-610×
C, crystal only)12Elasticity cut Systematic Error Study (
max fit0πθ o2.00
max fit0πθ o2.25
max fit0πθ o2.50
max fit0πθ o2.75
max fit0πθ o3.00
1.0k2.0k2.5k
0.0000±0.0000.1758±8.206
0.0000±0.000
C, crystal only)12Elasticity cut Systematic Error Study (
Dustin McNulty, Collaboration Meeting, July 21, 2007 11
PrimEx Collaboration Jefferson Lab Hall B
Nuc. Coherent Parameter vs. Elasticty Cut and Fit Range
)σ ±Elasticity Cut (0 1 2 3 4 5 6 7 8 9 10
ncY
ield
Fit
Par
amet
er: b
0.5
0.6
0.7
0.8
0.9
1
1.1
1.2
1.3
1.4
1.5Pb, crystal only)208Elasticity cut Systematic Error Study (
max fit0πθ o2.00
max fit0πθ o2.25
max fit0πθ o2.50
max fit0πθ o2.75
max fit0πθ o3.00
1.0k2.0k2.5k
nan±nan
nan±nan
0.000±0.00
Pb, crystal only)208Elasticity cut Systematic Error Study (
Dustin McNulty, Collaboration Meeting, July 21, 2007 12
PrimEx Collaboration Jefferson Lab Hall B
Incoherent Parameter vs. Elasticty Cut and Fit Range
)σ ±Elasticity Cut (0 1 2 3 4 5 6 7 8 9 10
bY
ield
Fit
Par
amet
er: b
0
1
2
3
4
5
6
7
8
9
10Pb, crystal only)208Elasticity cut Systematic Error Study (
max fit0πθ o2.00
max fit0πθ o2.25
max fit0πθ o2.50
max fit0πθ o2.75
max fit0πθ o3.00
1.0k2.0k2.5k
nan±nan0.496±5.510.000±0.00
Pb, crystal only)208Elasticity cut Systematic Error Study (
Dustin McNulty, Collaboration Meeting, July 21, 2007 13
PrimEx Collaboration Jefferson Lab Hall B
φ Parameter vs. Elasticty Cut and Fit Range
)σ ±Elasticity Cut (0 1 2 3 4 5 6 7 8 9 10
(rad
)φ
Yie
ld F
it P
aram
eter
:
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
1.1Pb, crystal only)208Elasticity cut Systematic Error Study (
max fit0πθ o2.00
max fit0πθ o2.25
max fit0πθ o2.50
max fit0πθ o2.75
max fit0πθ o3.00
1.0k2.0k2.5k
nan±nan
0.081±0.92 nan±nan
Pb, crystal only)208Elasticity cut Systematic Error Study (
Dustin McNulty, Collaboration Meeting, July 21, 2007 14
PrimEx Collaboration Jefferson Lab Hall B
Fit χ2/d.o.f vs. Elasticty Cut and Fit Range
)σ ±Elasticity Cut (0 1 2 3 4 5 6 7 8 9 10
/Ndf
2 χY
ield
Fit
Par
amet
er:
1
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
2Pb, crystal only)208Elasticity cut Systematic Error Study (
max fit0πθ o2.00
max fit0πθ o2.25
max fit0πθ o2.50
max fit0πθ o2.75
max fit0πθ o3.00
1.0k2.0k2.5k
0.000±0.00
0.491±1.250.000±0.00
Pb, crystal only)208Elasticity cut Systematic Error Study (
Dustin McNulty, Collaboration Meeting, July 21, 2007 15
PrimEx Collaboration Jefferson Lab Hall B
Γγγ Parameter vs. Elasticty Cut and Fit Range
)σ ±Elasticity Cut (0 1 2 3 4 5 6 7 8 9 10
(MeV
)γγΓ
Yie
ld F
it P
aram
eter
:
7.4
7.6
7.8
8
8.2
8.4
8.6
8.8-610× Pb, crystal only)208Elasticity cut Systematic Error Study (
max fit0πθ o2.00
max fit0πθ o2.25
max fit0πθ o2.50
max fit0πθ o2.75
max fit0πθ o3.00
1.0k2.0k2.5k
0.0000±0.0000.0933±8.111
0.0000±0.000
Pb, crystal only)208Elasticity cut Systematic Error Study (
Dustin McNulty, Collaboration Meeting, July 21, 2007 16
PrimEx Collaboration Jefferson Lab Hall B
Systematic Error Table
Dustin McNulty, Collaboration Meeting, July 21, 2007 17
PrimEx Collaboration Jefferson Lab Hall B
Uncertainty (%)
Description 12C 208Pb
mγγ fits + inelast bkgd corr. 1.8 1.1
Photon flux 1.1 1.1
Nuclear coh. XS energy dep. 0.04�
0.04
�
Detection/Recon efficiency 0.5 0.5
Fiducial Acceptance 0.6 0.6
�
Event Selection 1.0 1.0
�
Target thick. + branch ratio 0.06 0.5
Tagged Photon Energy 0.3 0.3
�
Total 2.4 2.1
Table 3: Preliminary summary of systematic uncertainties.
� � Not beenre-evaluated yet.
Dustin McNulty, Collaboration Meeting, July 21, 2007 18
PrimEx Collaboration Jefferson Lab Hall B
Preliminary Result Summary
From 12C:Γπ0 γγ
� 8 �20eV
�
1 �8%
�
stat
� �
2 �4%
�
syst
� �1 �3
�%
�
model
�
From 208Pb:Γπ0 γγ
� 8 �11eV
�
2 �0%
�
stat
� �
2 �1%�
syst� �
1 �3
�
%
�
model
�
� � � � Not been fully evaluated.Above width results for Sergey’s incoherent XSparameterization
Dustin McNulty, Collaboration Meeting, July 21, 2007 19
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