1. EG4-Update Krishna Adhikari Old Dominion University Deep Processes Working Group Meeting Nov 2, 2007, Jlab

2. Introduction Focused on the measurement of g1 and then its first moment  1 and the Generalized Gerasimov-Drell-Hearn (GDH) sum for proton & deuteron @ low Q 2 (0.01 – 0.5 GeV 2 ) region. Data taken from February to May, 2006. Spokepersons NH 3: M. Battaglieri, A. Deur, R. De Vita, M. Ripani (Contact) ND 3: A. Deur (Contact), G. Dodge, K. Slifer PhD. Students K. Adhikari, H. Kang, K. Kovacs INFN, JLab, ODU, Seoul U., U. Va. g1 is extracted from the helicity dependent absolute inclusive cross-section difference. Goal of the experiment is to measure the scattering of polarized electrons off polarized targets down to 6° scattering angles (to achieve the needed low Q 2 )

3. EG4 Experimental Set-Up (Longitudinally) polarized NH 3 and ND 3 targets. Longitudinally polarized electron beam (Pb ~ 80%) at energies 3.0, 2.3, 2.0, (1.5), 1.3 & 1.0 GeV. Cross section measurement requires uniform detection efficiency at low Q 2. New Cherenkov detector (INFN – Genova) installed to extend coverage for small scattering angles (down to 6 degrees) in sector-6. Out-bending torus field. New Moeller Shield (Tungsten). Standard CLAS NH3 & ND3 polarized targets in retracted position (-1m).

4. Calibration Status DC K. Slifer Complete CC (pedestals, gain matchings, efficiency) M. Ripani, K. Michaelson, A Vlassov, E.Golovach, X. Zheng. Complete TOF M. Ripani, J. Santoro ~90% Complete CC TDC J. Langheinrich, K. Michaelsen, M. Ripani ~90% Complete F-CupP. Konczykowski, A. Deur ~ 90% Complete EC TimingR. De Vita, K. Adhikari ~ 90% Complete ECC. Smith To be checked

5. Some Calibration Plots Position resolution in microns. (ns)

6. Analysis Tasks Radiation Length P. Konczykowski*, A. Deur Complete CC Cut & Efficiency study X. ZhengComplete Proton PolarimetryH. KangUnderway Deuteron PolarimetryK. KovacsUnderway Raster CorrectionK. Adhikari, P. Bosted, S. Kuhn Underway * Summer student from Saclay. Still working on F-Cup calibration in France

7. Proton Polarimetry - H Kang’s (Seoul U.) Work P b P tExtraction of P b P t. Procedure based on elastic scattering asymmetry at beam energy of 2.999 GeV. Dilution Factor evaluated from 12 C target data. Corrected for Beam Charge asymmetry. Currently, all corrections not applied yet (PbPt = 0.52 +- 0.04; expected between 0.6 and 0.7) and preliminary results show unphysical dependence on Q 2. (May be, applying the Fiducial cuts will improve the result)

8. Deuteron Polarimetry – K. Kovac’s (U.Va.) work Fitting the NMR data (red dots) by the theoretical Lineshape function (black line). P ratio vs P area For GEN data ND3 target polarization timeline (April, 06). Red dots – online. Green dots – offline analysis. CC values via ratio method using GEN NMR data vs different polarization values. Chi^2/D.F. = 0.5042 about CC = 63.381 Ratio Method for Deuteron P t : Chris Dulya’s (1996) revised code used for fitting, peak heights and P t measurements. Method used on GEN and RSS data; compared with the ‘TE method’ results to explore the limits of the ratio method. Error analysis and ‘ratio’ vs ‘TE’ comparison indicates that the method is reliable and accurate. In EG4, the TE calibration method for ND 3 not practical, so the ratio method is even more important. Started also working on the elastic asymmetry method (using Peter Bosted’s code) for the cross-check..

9. CC Efficiency: X. Zheng’s (U.Va.) work Cuts used: dt(sc – cc) > – 6ns & dt(ec –cc)> -6ns and elastic conditions. Theta & Phi coverage  p &  p : projected angles on CC plane, not the real scattering angles which are slightly below 6 degrees as designed. The green/red box: a fiducial cut to be used on CC. Ineff = e (-x/10) ; x = 10n phe

10. Raster Correction: K. Adhikari’s (ODU) Work Exclusive: 50808 Z 0 : a fit parameter that defines the target center. Z c : corrected vertex position - a function of , , sector-  & reconstructed p y, p x Conversion of ADC counts to cm: X 0, Y 0, c x & c y : fit parameters.

11. Physics Topics K. Adhikari Ph. D. student (ODU) Neutron inclusive analysis H. Kang Ph. D. student (Seoul U.) Proton inclusive analysis K. Kovacs Ph. D. student (U. Va.) Deuteron inclusive analysis Ramesh Subedi, X. Zheng Postdoc (U Va) Faculty (U. Va.)  + &  - exclusive analysis A. Biselli X. Zheng Faculty (Fairfield U.) Faculty (U. Va.)  0 exclusive analysis

12. Summary A few (3) iterations of pass-zero done. Finishing calibration by the end of Nov, 07. Will start pass-one in Dec, 07. Thank You!

14. Outline Introduction/Motivation Experimental Set-Up Calibration Status Analysis Status Summary