"Elastic and inclusive

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"Elastic and inclusive scattering cross-section
studies for E1E data"
Nikolay Markov
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Goals and outline.

• Perform electron ID for 2 data sets of E1E
  experiment
• Obtain elastic cross-section from data
• Obtain inclusive cross-section from data
• Compare cross-sections to existing models.

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1 GeV electron ID.
Number of photoelectrons greater then
0 Calorimeter cut
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Fiducial cut
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W distribution
By making cut on W (0.9 lt W lt 1.05)
cut
cut
cut
cut
cut
cut
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distribution for elastic electrons
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Vertex correction
Using Cole Smiths procedure for vertex correction,
Vertex cut
After
Before
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Correction
Using Cole Smiths procedure,
Black before correction, red - after
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Resulting W distribution.
Before
After
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Elastic acceptance calculation

• One million events generated uniformly in phi
  and theta

• Fiducial cut was applied

• Ratio of accepted to generated events in each
  theta bin was calculated

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Elastic cross-section comparison
Now we can calculate ratio of our experimental
cross-section to theoretical value
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Selecting Q2 bins.
Using this Q2 distribution of events, regions of
Q2 were chosen to calculate inclusive
cross-section.
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Inclusive acceptance

• 1 million events generated uniformly in theta
  (20,60) degree, phi (-30,30)
• degree and momentum (0,1) GeV.

• Based on fiducial cuts, some events were
  accepted, some rejected, and result written in
  different Q2 bins

• Ratio of accepted to generated was calculated in
  each W bin

Generated
Generated
Accepted
Accepted
Generated
Generated
Accepted
Accepted
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BH subtraction

• By cut on phi_proton-phi_electronlt2o we can
  select elastic events

• By cut on phi_proton-phi_electronlt2o we can
  select elastic events

• Comparing W distributions before and after the
  cut, we can find
• normalizing coefficient

• Then, we apply normalizing coefficient to W
  distribution and subtract it from one before
  cuts, and, as final step, for inclusive region
  calculate the ratio of result of subtraction to
  initial W distribution

Phi cut
Phi cut
All
All
Phi cut
Phi cut
All
All
Phi cut
Phi cut
All
All
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The resulting inclusive cross-section
Model
Model
Data
Data
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Simulation

• Simulation using keppel_rad and keppel_norad was
  apllied to
• determine radiative correction to experimental
  cross-section.

• Resulting correction coefficient, defined as
  ratio of number radiative events in one bin to
  number of non-radiative is

Radiative
Radiative
Non-radiative
Non-radiative
0.3ltQ2lt0.4
0.2ltQ2lt0.3
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Resulting Cross-section
model
model
experiment
experiment
0.2ltQ2lt0.3
0.3ltQ2lt0.4
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2 GeV electron ID.
Same cuts were used, except for fiducial cut,
which is tighter
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Vertex cut
Procedure, applied for 1 GeV vertex correction
doesnt work here, so separate vertex cuts were
used for different sectors.
cut
cut
cut
cut
cut
cut
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W spectrum
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Acceptance.
With new fiducail cuts, we need to recalculate
our elastic acceptance
Old
New
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Comparison of elastic cross-section
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Q2 distribution
Several regions were chosen to calculate
inclusive cross-section
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Unselecting the 0 region
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Systematic studies
Systematic studies for 2 GeV inclusive
cross-section consists of the following For BH
elimination procedure, different cuts to select
elastic events were applied first, we obtained
cross-section with phi_proton-phi_electronlt2o,
then ,with phi_proton-phi_electronlt1o, and the
difference between these approaches was
interpreted as systematic error of our BH
subtraction procedure.
1o
2o
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Resulting cross-section
Red model, black data, blue systematic
errors
0.6ltQ2lt0.7
0.5ltQ2lt0.6
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Resulting cross-section
Red model, black data, blue systematic
errors
0.8ltQ2lt0.9
0.7ltQ2lt0.8
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Resulting cross-section
Red model, black data, blue systematic
errors
0.8ltQ2lt0.9
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Radiative corrections
Using the same procedure, as for 1 GeV data, we
obtained following cross-sections
Red model, black - data
0.5ltQ2lt0.6
0.6ltQ2lt0.7
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Radiative corrections
Red model, black - data
0.7ltQ2lt0.8
0.8ltQ2lt0.9
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Radiative corrections
0.9ltQ2lt1.0
Red model, black - data
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ID check
Since there are visible problems with inclusive
cross-section, Studies were performed to check
whether electron ID, used for 2 GeV run is
adequate enough for two GeV data.
Number of photoelectrons
Number of photoelectrons vs W
1 GeV
2 GeV
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Conclusion

• For 1 GeV and 2 GeV data set electron ID was
  performed
• Elastic cross-sections for both data set is in
  good agreement with model
• Inclusive cross-section for 1 GeV data set is in
  reasonable agreement with model
• Inclusive cross-section for 2 GeV data set need
  improvement
• For 2 GeV data set modification of electron ID,
  including Cherenkov cut looks necessary
• For 2 GeV data set there is a need to perform
  kinematical and vertex corrections based on 1 GeV
  procedure.