1. PrimEx II 0 analysis status

2. Runs analyzed
Current analysis includes the part of total statistics beginning from the run 64707, when the new hardware has been installed, i.e.:
Silicon runs: – 64988
Carbon runs: – 65059, – 65112
Empty target runs: – 65005, – 65095
runs have missed reference TAGE TDC

3. Event selection Energy (E single>0.5GeV; E pair>3GeV)
Timing (|Tdiff| < 10ns)
Elasticity (by constrain procedure)
Crystal only HyCal part
Coincidence trigger (bit 10)

4. Energy distribution Two clusters energy Single cluster energy
Analysis cut
Analysis cut

5. HyCal clusters multiplicity in selected events
PrimEx I
PrimEx II
<n>=2.40
<n>=2.28

6. Timing: time difference between Tagger and HyCal time
PrimEx I
PrimEx II
 = 1.0ns
 = 1.5ns

7. Two clusters elasticity distributionSi C
 = 2.4%
 = 2.4%
 = 1.3%
 = 1.3%
Mass constraint applied

8. Two clusters elasticity distribution
Empty target
Mass constraint applied

9. Two gamma invariant massC Si
 = 3.1MeV
 = 3.1MeV
Empty
Empty

10. Two gammas elasticity VS inv. mass
Empty

11. Two gamma invariant mass with elasticity constraintSi
Empty
Empty

12. dN/d Silicon Theory c. s. at 5GeV PrimEx II Number of events
corresponds ~71012 beam photons

13. dN/d Carbon PrimEx I PrimEx II Omega subtracted Omega unsubtracted
Number of events
corresponds ~11012 beam photons

14. Conclusion
Further analysis will include HyCal veto and timing and more algorithm tunings
Very preliminary number of Primakoff events for silicon ~20K, for carbon ~ 8K
We have two more measurements of pi0 Primakoff cross section: on carbon and on silicon, each with higher than PrimEx I statistics
Si has shown good coherent part (first Si measurement?)