1. EG4 Update Sebastian Kuhn Old Dominion University June 21, 2013 With help from Krishna Adhikari, Alexandre Deur, Marco Ripani and the EG4 group

2. CLAS- EG4 (E03-006 (NH 3 ) + E06- 017 (ND 3 )): a measurement of g 1 and the extended GDH (Gerasimov- Dreall-Hearn) integral for the proton and neutron (deuteron) at very low Q 2 (0.015 – 0.5 GeV 2 ) Performed in Jlab Hall-B from February to May, 2006. Analysis crew as of today: Hyekoo Kang, Krishna Adhikari (Ph.D. Students) and Alexandre Deur, Marco Ripani, Karl Slifer, Sarah Phillips, Elena Long, Xiaochao Zheng, Sebastian Kuhn

3. Importance of Generalized GDH Sum Rule Generalized GDH Sum Rule, being defined for all Q 2, provides a useful tool to study the transition from hadronic to partonic descriptions of Strong interaction. – Very high Q 2 (> ~5 GeV 2 ): (Bjorken limit): pQCD – High Q 2 (> ~1 GeV 2 ): Operator Product Expansion – Intermediate Q 2 region: Lattice QCD calculations – Low Q 2 region (< ~0.1 GeV 2 ): Chiral Perturbation Theory Calculations: Relativistic Baryon  PT with  Bernard, Hemmert, Meissner  Heavy Baryon  PT, Ji, Kao, Osborne; Kao, Spitzenberg, Vanderhaeghen – The experimental measurement of the GDH integral will be very important to test and constrain such calculations. 11 Expected precision for deuteron Expected precision for proton

4. Methodology to measure GDH sum  How to extract g 1 ? N -+, N ++  the # of events detected for the parallel & anti-parallel beam-target polarizations N i, t, , f and P b P t  the # of incident electrons (Faraday cup), target areal-density, the detector acceptance, detector efficiency, and the product of beam-target polarizations respectively.  How to measure the helicity dependent absolute cross-section difference?  g 2 contribution is small at low Q 2 values; extract g 1, then evaluate  1, the GDH sum and higher moments.

5. Methodology to measure GDH sum Practical Approach:  Normalize for PbPt, target thickness, overall efficiency using well-known cross section difference in the (quasi-)elastic region  Method I:  Use model of world data on all structure functions, radiative effects etc. to generate simulated count differences on polarized species (p, d) for opposite beam helicities  Run through GSIM, GPP, RECSIS, higher level analysis  Apply corrections for efficiency (CC, tracking,…), backgrounds  Compare with data (count differences)  Iterate with varying input for g 1 to extract “true g 1 ”  Method II:  Use full simulation of complete target (NH 3, ND 3 + He, foils…) tuned to agree with data; determine acceptance*efficiency from ratio MC reconstructed/MC thrown  Correct measured count rate differences for all factors on previous slide, apply corrections for g 2 etc., extract g 1

7. P B P T from QE Asymmetry vs Polarimetry NMR&Moller QE Asym Stat errors only Analysis by Sarah Phillips (Deuteron Run) S. Phillips, K. Slifer Very good agreement between the methods before ESR Crash/Material change afterwards, NMR+Moller is larger than the asymmetry result. Each data point represents average over a run-group 1) 51582 – 51601 2) 51602 – 51679 3) 51680 – 51779 4) 51791 – 51870 5) 51874 – 52040 before ESR crash After ESR crash

8. PbPt for NH 3 runs (simulation) H. Kang, A.Deur Working on absolute proton polarized elastic cross- section difference. Initially used simpler simulation than GSIM Now, working on repeating this work with GSIM (more detailed simulation but more of a "black box" so it's harder to understand and to be sure to control everything GSIM does).

9. Simulation of Deuteron Data K. Adhikari, S. Kuhn “RCSLACPOL” program (Incorporates both internal & external radiative effects) generates polarized & unpolarized cross sections (both Born and radiated) Based on the standard approach by Shumeiko and Kuhto as well as Mo and Tsai, including external radiation in the target. Extensively tested & used – at SLAC (E142, E143, E154, E155 & E155x) & Jlab (EG1a/b). Updated with the most recent models on polarized and unpolarized structure functions (F 1, F 2, A 1 & A 2 ) and an implementation of the folding algorithm developed by W. Melnitchouk and Y. Kahn for structure functions of the deuteron. The models fitted to & tested with data from EG1b as well as world data on both A1 and A2 over a wide range of Q2 and W, including the resonance region and the DIS region. For EG4, we have combined this code with the event generator “STEG” developed by the Genova group – RCSLACPOL generates cross-section map & STEG generates events accordingly.

10. But: Strange RECSIS features… DataGSIM

11. …lead (?) to discrepancies between data and simulation…

12. Spectra look different!

13. Use  VTX and  DC1-pos for fiducial cuts

14. Remove areas of clear CC inefficiency

15. ⇒ somewhat improved agreement (will have to select stable region for P b P t DF)

16. CC inefficiency 1:

17. CC inefficiency 2: 1 – (Events passing all cuts/Events passing EC cuts only)

18. CC inefficieny 3: Fit to use for weighting MC events

19. Summary & Future Work Finished most of the data analysis tasks Extensive work on simulation with GSIM ongoing – try to understand differences with data – GSIM Simulation work to extract physics quantities from ND 3 data underway – K. Adhikari, S. Kuhn – GSIM Simulation on NH 3 data underway – H. Kang, A. Deur, M. Ripani Expect first results on the deuteron by end of this year Hope for publications next year