CLAS DB: Physics data analysis capabilities

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CLAS DBPhysics data analysis capabilities
Hall B, Thomas Jefferson National Accelerator
Facility
Vitaly Chesnokov, Moscow State University
Skobeltsyn Institute for Nuclear Physics
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Contents

• Simple tools for physics analysis in CLAS
  PhysicsDB
• Exclusive structure functions for unpolarized
  beam and target
• Evaluation of 5th structure function from CLAS
  data on beam asymmetry and unpolarized
  cross-sections.
• W-dependence of completely integrated 5th
  structure functions and manifestation of Ns

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Structure functions for reactions with
unpolarized beam and target

• f dependence of exclusive cross-sections

• f is asimutal angle for final particle with
  respect to electron scattering plane
• KL is equivalent photon vector,
• MN is nucleon mass,
• a 1/137,
• Pfin modular of the final particle 3-momentum in
  CM frame,
• W is invariant mass of the final hadronic
  system,
• 389.5 is a coefficient needed to express
  cross-sections in mcbn units

Relations between extracted coefficients
and exclusive structure functions
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Tools in CLAS Physics DB for evaluation of
unpolarized structure function

• Fitting procedures for evaluation of unpolarized
  structure functions for exclusive channel were
  implemented. They allow us to determine structure
  function fitting f-distribution for detected
  particle. Currently such fit is available for the
  following CLAS experiments

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Beam Asymmetry

• E99-107
• CLAS experiment
• Final State ?n
• Q2 1.56 3.79
• W 1.1 1.7

Data fitting
D coefficient were fitted to the data of ALU in
each ?-bin independently. They are related to
the 5th structure function as
in a case of single pion channel
Denominator was fitted to CLAS data on
unpolarized pn cross-sections. Unpolarized
cross-sections were estimated in model
independent way.
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Evaluation of unpolarized cross-sections at
arbitrary ? bin

• We have different grids for cross-sections and
  asymmetries
• Unpolarized cross-sections were estimated from
  formulae of mentioned above (3rdslide).
• ?-dependences for A,B,C coefficients were
  interpolated by 2-order polynomials.

E76M26 average(E14M48,E14M49)
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1.5
1
A, B, C coefficients
0.5
0
-0.5
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
cos(?)
A interpolation
Q21.872.23 GeV2 W 1.341.38 GeV
B interpolation
C interpolation
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Integrated 5th structure functions

• Calculated RLT was integrated over cos(?)

for each W, Q2 bin. Integrated 5th structure
functions were incorporated into the CLAS DB as a
separate measurement of the same experiment
(E76M65 in CLAS DB numeration).
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Conclusions

• 5th structure functions were extracted in
  combined analysis of the data on beam asymmetries
  and unpolarized cross-sections, stored in CLAS
  Physics DB.
• Procedures for 5th structure function extraction
  from the data together with graphical tools for
  presentation of RLS dependence from kinematics
  variables were incorporated to the DB. Currently
  they are available for 7 CLAS experiments. They
  may be easily applied to the data of other
  similar experiments.
• Completely integrated 5th structure function for
  pn exclusive channel show prominent structures
  in its W-dependence, possibly related to the
  contributions from Ns. Their further analysis
  may improve available information on N
  parameters.
• Combined analysis of beam asymmetry and
  unpolarized cross-sections, using variety of the
  data from different measurements is critical for
  model independent evaluation of RLT. Therefore,
  extension of CLAS DB by new data sets will open
  up new opportunities in the studies of exclusive
  structure functions