1. CLAS DB: Physics data analysis capabilities
Hall B,
Thomas Jefferson
National Accelerator Facility
Vitaly Chesnokov,
Moscow State University Skobeltsyn Institute for Nuclear Physics

2. 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 N*’s
Vitaly Chesnokov: CLAS DB Physics Data Analysis Capabilities

3. Structure functions for reactions with unpolarized beam and target
φ dependence of exclusive cross-sections
Relations between extracted coefficients and
exclusive structure functions:
φ is asimutal angle for final particle with respect to electron scattering plane
KL is equivalent photon vector,
MN is nucleon mass,
α = 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
Vitaly Chesnokov: CLAS DB Physics Data Analysis Capabilities

4. 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 φ‑distribution for detected particle. Currently such fit is available for the following CLAS experiments:
CLAS
Experiment
Number in CLAS DB
E93-006 1
E89-042 7
E89-038 8
E89-037 9
E99-107 14
E94-005 62 76
Vitaly Chesnokov: CLAS DB Physics Data Analysis Capabilities

5. Beam Asymmetry E99-107 Data fitting: 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 θ-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 p+n cross-sections.
Unpolarized cross-sections were estimated in model independent way.
Vitaly Chesnokov: CLAS DB Physics Data Analysis Capabilities

6. Evaluation of unpolarized cross-sections at arbitrary θ bin
We have different grids for cross-sections and asymmetries
Unpolarized cross-sections were estimated from formulae of mentioned above (3rdslide).
θ-dependences for A,B,C coefficients were interpolated by 2-order polynomials.
E76M26 + average(E14M48,E14M49) 2
1.5 1
A, B, C coefficients
0.5
-0.5
-0.8
-0.6
-0.4
-0.2
0.2
0.4
0.6
0.8 1
cos(θ)
A interpolation
B interpolation
Q2=1.87÷2.23 GeV2
W =1.34÷1.38 GeV
C interpolation
Vitaly Chesnokov: CLAS DB Physics Data Analysis Capabilities

7. Integrated 5th structure functions
Calculated RLT’ was integrated over cos(θ)
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).
RLT’ коммутирует с RKL’
Vitaly Chesnokov: CLAS DB Physics Data Analysis Capabilities

8. 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 π+n exclusive channel show prominent structures in its W-dependence, possibly related to the contributions from N*’s. 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
Vitaly Chesnokov: CLAS DB Physics Data Analysis Capabilities