1. EG4-Update Krishna Adhikari (Graduate student) Old Dominion University Deep Processes Working Group Meeting Feb 23, 2008, 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. 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 ) Data taken from February to May, 2006.

3. EG4 Experimental Set-Up (Longitudinally) polarized standard CLAS 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. New Cherenkov detector (INFN – Genova) installed in sector-6. ( For uniform detection efficiency at low Q 2 and to extend coverage for small scattering angles (down to 6 degrees) Out-bending torus field. New Moeller Shield (Tungsten). Targets in retracted position (- 1m).

4. Calibration Status ~ 90% Complete P. Konczykowski, A. DeurF-Cup To be checked C. SmithEC Complete M. Ripani, K. Michaelson, A Vlassov, E.Golovach, X. Zheng. CC (pedestals, gain matchings, efficiency) M. Ripani, J. Santoro, R. De Vita TOF R. De Vita, K. Adhikari EC Timing Complete J. Langheinrich, K. Michaelsen, M. Ripani, R. De Vita CC TDC Complete K. Slifer DC Complete

5. Tasks beyond Calibration Work PeopleStatus CC cut & efficiency X. ZhengComplete** Radiation Length P. Konczykowski*, A. DeurComplete Proton Polarimetry H. KangComplete** Deuteron PolarimetryK. Kovacs, K. SliferComplete Simulation (GSIM) V. Droznov, M. Ripani, R. De VitaUnderway Beam parametersK. Kovacs, M. RipaniUnderway Beam Charge asymmentry H. KangUnderway DC performance M. Ungaro, M. RipaniUnderway Raster & Mom. Corr.K. Adhikari, P. Bosted, S. KuhnUnderway * Summer student from Saclay.

6. Some Global Calibration Plots (after Pass04) Position resolution in microns. (ns)

7. Beam Charge Asymmetry by H. Kang Calculated the charge asymmetry of a few 12C runs for various energies using the gated and ungated F-cup counts. Tried to see the false asymmetry from the unpolarized 12C -targets GeVRegionChi2Par.Err 1.10.815<W<1.550.992147-0.0004359970.000168765 1.30.815<W<1.661.193670.00009732350.000185842 2.00.815<W<1.951.041620.0002287060.000193865 2.30.815<W<2.100.9359020.000133210.000311318 3.00.815<W<2.401.113010.0004933660.000271364

8. Beam current (Fcup) by K. Kovacs Target types: Starting from more empty to more full, they are: 0 – empty, no helium; 1 – empty with He; 2 – short C, no He; 3 – long C, no He; 4 – short C with He; 5 – short NH3 with He; 6 – long C with He; 7 – long NH3, top cell; 8 – long NH3 bottom cell; 9 – long ND3 Beam loss for Fcup larger at lower beam energies as expected.

9. Beam current (F-cup) at E = 1.34 GeV (by P. Konczykowski)

10. Results from GSIM Plots for E = 1.339 GeV Solid curve – reconstruction counts Dashed curve – experimental counts For some especial theta – obscure holes and peaks in E’ distributions Might be the software problem. (probably some sneaky bug in RECSIS - - R. De Vita looking into it). V. Droznov and M. Ripani

11. More detailed analysis shows that simulations are good for restored momentum, but not restored phi and theta. E gen – generated momentum, E rec –reconstructed momentum, etc.

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

14. Summary Five iterations of pass-zero done. Calibration finished. Preparation for pass-one in progress. We expect to start in few weeks. Thank You!

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

18. ResultsfromGSIM Results from GSIM

19. 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)

20. Work on beam parameters K. Kovacs and M. Ripani Picked info regarding Fcup/BPM ratio for different beam energies and target types from EG4 online log entry. Made some changes to the offline data reconstruction code to include various various beamline and target variables and created new ntuples for the analysis. Extracted Fcup/BPM ratio from the ntuples for different target types and beam energies to calibrate the Fcup beam loss. (A quick check on the more complete analysis by Piotr K.) Target types: Starting from more empty to more full, they are: 0 – empty, no helium; 1 – empty with He; 2 – short C, no He; 3 – long C, no He; 4 – short C with He; 5 – short NH3 with He; 6 – long C with He; 7 – long NH3, top cell; 8 – long NH3 bottom cell; 9 – long ND3 Obvious – remove it The beam loss for Fcup at lower beam energies is significantly larger than that at the higher energies.

21. 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

22. 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..

23. 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.