PrimEx p0 radiative width extraction
Eric Clinton
University of Massachusetts Amherst
June 21, 2007
1
Outline
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Data Source and cuts
Event selection
Hybrid Mass Signal enhancement
Yields
Systematic effects from yield extraction
Simulation
Results
Sytematic Error Analysis
2
Data Source and Cuts
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mysql -h primexdb -u
primex_user book_keeping b --execute="select run
from run_list where
radiator='A' and
target='carbon' and
type='pi0' and
production='good';" >
run_list.example
mysql -h primexdb -u
primex_user book_keeping b --execute="select run
from run_list where
radiator='B' and
target='carbon' and
type='pi0' and
production='good';" >
run_list.example
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1.) Two or more clusters/event.
2.) Minimum three (3) (PbWO4 or lead
glass) detectors to define a “cluster”.
3.) 50 MeV or greater central (PbWO4 or
lead glass) crystal detector energy in
cluster.
4.) 10 MeV or greater minimum
deposited energy in (PbWO4 or lead
glass) detector.
5.) Max cluster energy 8 GeV.
6.) gg invariant mass greater than 0.085
GeV in at least one of the cluster pairs.
7.) Elasticity (cluster pair energy
sum/tagger energy) greater than 0.70.
8.) Cluster energy greater than 0.5 GeV.
9.) Cluster X or Y position must be
greater than 3.8 cm.
10.) Cluster pair energy sum between 3.5
and 6.5 GeV -- additional software cut
not imposed on the skim, but imposed
later:
11.) Timing cut of -15 ns to +5ns.
“pi0gains” used as caliubration
3
Event selection
Eliminate Tagger and HyCal combinatorics
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Likelihood
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Event entries have invariant
mass, elasticity, and timing
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Fit invariant mass, elasticity,
timing signal and background
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Fitted signal lineshape as
probability density function
(PDF)
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Which entry to choose in a
mutli-entry event?
Which is "most likely"?
Evaluate the PDF for each
parameter for each entry.
Three individual likelihoods.
PDFInvariant mass, PDFElasticity,
PDFTiming
Total likelihood = PDFInvariant
mass × PDFElasticity ×PDFTiming
Entry with highest total
likelihood "wins".
4
Getting Final Likelihood spectrum
Take entire “Most Likely” spectrum as event sample
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Most Likely invariant
mass spectrum
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Final Likelihood
PDFInvariant mass × PDFElasticity
×PDFTiming
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Misidentification –
any systematics?
No. MisID is random, and event selection
tends to pick smaller production angle pions.
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Rotation of 2-D data onto 1-D
Try to enhance signal to noise
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Original 2-D data
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Elasticity vs.Invariant Mass
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New 1-D signal
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AKA “Hybrid Mass”
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Selected Hybrid Mass Fits
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p0 yields as a
function of
production angle.
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Systematic error sources?
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Extracted yields
over the entire
pion angle range
must be stable as
these parameters
are varied.
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Lineshape Degrees of Freedom
entire HyCal acceptance
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Integration/BG subtraction range
entire HyCal acceptance
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Stability of Fit Range
entire HyCal acceptance
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The Veto—how it changes the
angular spectrums
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Extracting a Photon Misidentification Efficiency
PME = 0.76%
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Simulation Work
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Thrown with E-Channel Photon flux weighting
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Energy correction added
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Proper shower development
Resolution and centroid tuned
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Energy lost out back of HyCal, out of cluster mask
Added back about 10% of energy
Tracking threshold tuned
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Primakoff (with FSI), Coherent (Cornell with FSI), Incoherent
(Glauber)
Get invariant mass right to proper mock physics
Vet the Simulation
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Push 4 vectors from experiment thru sim
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See how p0 candidate spectrum look, look for losses
Turn off detectors, see how acceptance behaves
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Photon flux
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Poor Elasticity
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Energy Correction
Across entire HyCal acceptance
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Tracking Threshold, resolution, and centroid tuning
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Putting physics
events thru the
Simulation
Around 99.2% fidelity
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Turning off glass detectors
Entire HyCal Acceptance
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Turning off tungstate detectors
Entire HyCal Acceptance
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Turning off glass detectors
HyCal Tungstate Acceptance Only
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Efficiencies
as a function of the photo-pion process, entire HyCal acceptance
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Geometric efficiency
and reconstruction
(cut) efficiency.
Entire HyCal
Acceptance
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Efficiencies
as a function of the photo-pion process, HyCal Tungstate acceptance
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Geometric efficiency
and reconstruction
(cut) efficiency
HyCal tungstate
acceptance
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Fit to Data, and Extracted Width
Entire HyCal Acceptance
Extracted width – 7.870 eV ± 0.139 eV (1.77%)
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Fit to Data, and Extracted Width
HyCal Tungstate Acceptance
Extracted width – 7.859 eV ± 0.146 eV (1.86%)
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Acceptance
Corrected Cross
Sections
Entire HyCal Acceptance
HyCal Tungstate Acceptance
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Systematic Error
Entire HyCal acceptance
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Nominal
7.870
NA
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Fit Range (nominal = ±0.030 HMU’s
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Veto width:
7.779
-1.16
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Cluster Position Finding Method
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7.720
7.888
7.938
7.849
-1.90
0.23
0.86
-0.27
Lineshape (degrees of freedom)***
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Method 0:
Method 1:
Method 2:
Method 4:
DG3Sp:
TG3Po:
7.859
7.931
-0.14
0.77
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* (+)
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* (-)
* (+)
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3% width:
2% width:
0.5% width:
0.3% width:
0.2% width:
7.802
7.841
7.966
7.966
8.001
-0.86
-0.36
1.22
1.22
1.67
* (-)
7.760
7.973
-1.40 %
1.31 %
-30, +33
-30, +27
7.838
7.877
-0.41 %
0.09 %
-27,+30
-33, +30
7.745
8.002
-1.58 %
1.68 %
Average =
Average =
Average
7.867
7.862
7.870
-0.03 % *(-)
-0.10 % *(-)
0.04 % (+)
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Adding the *(+) gives positive
sytematic shift +1.46
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Adding the *(-) gives negative
systematic shift -0.88
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Systematic Error = +1.46, -0.88
Integration range (Nominal cutoff = 1.0%)
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-27, +27
-33, +33
*(+)
***Nominal = Double gaussians with 3rd order polynominal
DG3Sp = Double gaussians with 3rd order spline
TG3Po = Triple gaussians with 3rd order polynominal
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Systematic Error
HyCal Tungstate acceptance
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Nominal
7.859
NA
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Fit Range (nominal = ±0.030 HMU’s
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Veto width:
7.774
-1.16
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Cluster Position Finding Method
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7.699
7.827
7.881
7.670
-2.04
-0.41
0.24
-2.40
Lineshape (degrees of freedom)***
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Method 0:
Method 1:
Method 2:
Method 4:
DG3Sp:
TG3Po:
7.859
7.891
-0.00
0.41
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* (-)
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* (-)
* (+)
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5% width:
2% width:
0.5% width:
0.2% width:
0.1% width:
7.788
7.813
7.877
7.938
7.926
-0.90
-0.59
0.22
1.00
1.31
7.809
7.888
-0.63 %
0.36 %
-30, +33
-30, +27
7.824
7.888
-0.45 %
0.36 %
-27,+30
-33, +30
7.777
7.941
-1.04 %
1.04 %
Average =
Average =
Average
7.867
7.862
7.870
-0.1 % *(-)
-0.03 % *(-)
0.00 % (+)
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Adding the *(+) gives positive
sytematic shift +1.08
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Adding the *(-) gives negative
systematic shift -0.99
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Systematic Error = +1.08, -0.99
Integration range (Nominal cutoff = 1.0%)
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-27, +27
-33, +33
* (-)
*(+)
***Nominal = Double gaussians with 3rd order polynominal
DG3Sp = Double gaussians with 3rd order spline
TG3Po = Triple gaussians with 3rd order polynominal
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Total Error budget
Entire HyCal Acceptance
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HyCal Tungstate Acceptance
Statistical
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Statistical
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Veto Off
± 1.77
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Veto Off
± 1.86
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Veto On
± 1.62
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Veto On
± 1.75
Photon Flux
Systematic (Yield Extrn.)
Branching Ratio
Target Thickness
Veto (if used)
±1.10
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Photon Flux
+1.46, -0.88
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Systematic (Yield Extrn.)
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Branching Ratio
±0.03
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Target Thickness
±0.04
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Veto (if used)
± 0.05
± 0.03
± 0.04
± 0.05
±1.10
+1.08, -0.99
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Result
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Entire HyCal Acceptance
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Gp0 = 7.870 eV ± 0.139 eV +0.144 eV – 0.111 eV
Gp0 = 7.870 eV ± 1.77 % +1.83% - 1.41%
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HyCal Tungstate Acceptance
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Gp0 = 7.859 eV ± 0.146 eV +0.121 eV – 0.116 eV
Gp0 = 7.859 eV ± 1.86 % +1.54% - 1.48%
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Future work
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Work another nuclear incoherent
generator
Evolve cross sections to the weighted
mean photon energy
Lead Target Data?
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