1. Elastic Electron Scattering off He and He (E04-018) Elena Khrosinkova Kent State University Hall A Collaboration Meeting Jefferson Lab, June 2008 34

2. Objective Elastic scattering off helium's stable isotopes at large momentum transfers Extraction of He3 charge and magnetic and He4 charge form factors Jefferson Lab, June 2008 2/17

3. Experimental Apparatus Coincidence experiment using TOF method 20 cm helium cells Jefferson Lab, June 2008 3/17

4. Elastic Electron-Helium Scattering He charge and magnetic form factors:, He charge form factor: AB const A B Jefferson Lab, June 2008 4/17

5. Data range Jefferson Lab, June 2008 5/17

6. Data range Jefferson Lab, June 2008 6/16

7. Data range Jefferson Lab, June 2008 7/17

8. Analysis projects Current Calibration 2 current calibrations Normalization of the current at the injector cavity to the Faraday cup Cross-check with the Unser current Jefferson Lab, June 2008 8/17

9. Normalization of the two BCM cavities to the calibrated injector cavity Analysis projects Current Calibration Jefferson Lab, June 2008 9/17

10. Normalization of the scalers frequency (right, left) to the average value of the calibrated injector cavity current Analysis projects Current Calibration Jefferson Lab, June 2008 10/17

11. Analysis projects Calorimeter calibration 6x6 blocks calibration MC simulation for energy deposited in first and second layers 1222 – 1273 runs ep elastic, 2.13 GeV E/p vs E E/p Counts Jefferson Lab, June 2008 11/17

12. Cerenkov sum corrected Analysis projects Cerenkov Gain Equalization With cuts on >99% of total light in one particular tube Number of photoelectrons > 6 Cerenkov efficiency close to 100% 1222 – 1273 runs ep elastic, 2.13 GeV L.cer.a_p[4] L.cer.a_p[5] Counts Jefferson Lab, June 2008 12/17

13. Analysis projects Timing Offsets Correction 1232 – 1233 runs, ep elastic 2.34 GeV Jefferson Lab, June 2008 13/17 tof, uncorrected tof, corrected Counts

14. Analysis projects Scintillators ADC Equalization L.s1.ra_p[3] L.s1.ra_p[2] L.s1.la_p[3] L.s1.la_p[2] L.s1.la_c[*] + L.s1.ra_c[*] Jefferson Lab, June 2008 14/17 1222 – 1273 runs ep elastic, 2.13 GeV

15. Analysis projects Event Display Jefferson Lab, June 2008 15/17 3D event display For all tracks from the analyzer LHRS and RHRS Cuts for fired blocks In progress

16. Elastic stripe = 40 fm, e He Jefferson Lab, June 2008 16/17 Left, m Right, m

17. Summary Finalization of the detector calibrations Improving tracking routine Ready for mass analysis Jefferson Lab, June 2008 17/17