1. New Results from the G0 Experiment Elizabeth Beise, University of Maryland 1 CIPANP 2009 E. Beise, U Maryland Parity-violating electron scattering from the nucleon Hydrogen and deuterium targets Strange quark contributions to electromagnetic form factors Axial-vector N-  transition Weak interaction contribution to pion photoproduction Transverse beam spin asymmetries

2. Spatial distribution of s-quarks in the nucleon Access via form factors: contribution to nucleon charge and magnetism E. Beise, U Maryland sin 2  W = .2312 Electromagnetic: and use charge symmetry CIPANP 2009 2 courtesy of JLab

3. Parity Violating elastic e-N scattering E. Beise, U Maryland 3 polarized electrons, unpolarized target forward, H e.g.: G0 at 687 MeV (Q 2 ~ 0.6 GeV 2 ) a 0 (ppm) a 1 (ppm) a 2 (ppm) a 3 (ppm) AFAF -2480433 ABAB -39226312 AdAd -50191314 back, H back, D CIPANP 2009

4. Axial form factor seen by PV electron scattering E. Beise, U Maryland ++ but Q 2 behavior is not well constrained (  F A  + R e ) at Q 2 =0 computed by Zhu etal, PRD 62 (2000) 033008 SAMPLE deuterium asymmetry data agree well CIPANP 2009 4

5. Summary of data at Q 2 =0.1 GeV 2 E. Beise, U Maryland 5 (thanks to K. Pashke, R. Young) Solid ellipse: K. Pashke, private comm, [same as J. Liu, et al PRC 76, 025202 (2007)], uses theoretical constraints on the axial form factor Dashed ellipse: R. Young,et al. PRL 97 (2006) 102002, does not constrain G A with theory CIPANP 2009 2007 Long Range Plan note: Placement of SAMPLE band on the graph depends on choice for G A

6. New Results from PVA4 Q 2 = 0.22 GeV 2  = 145° A meas =  17.23 ± 0.82 ± 0.89 ppm A nvs =  15.87 ± 1.22 ppm (uses theoretical constraint of Zhu et al., for the axial FF) S. Baunack et al., PRL 102 (2009) 151803 % contribution to proton: electric:  3.0 ± 2.5 % magnetic:  2.9 ± 3.2 % CIPANP 2009 6E. Beise, U Maryland Wang, et al. (arXiv:0807.09442), 1.8 ± 1.1 %

7. Quasielastic PV (ee’) in Deuterium E. Beise, U Maryland Parity conserving nuclear corrections to the asymmetry are generally small, 1-3% at backward angles. Calculation provided to us by R. Schiavilla includes final state interactions and 2-body effects. Use Quasielastic scattering from deuterium as lever arm for G A e (Q 2 ) Diaconescu, Schiavilla + van Kolck, PRC 63 (2001) 044007 Schiavilla, Carlson + Paris, PRC 67 (2003) 032501 See also Hadjimichael, Poulis + Donnelly, PRC45 (1992) 2666 Schramm + Horowitz, PRC 49 (1994) 2777 Kuster + Arenhovel, NPA 626 (1997) 911 Liu, Prezeau, + Ramsey-Musolf, PRC 67 (2003) 035501 CIPANP 2009 7

8. Deuterium model comparison to cross section data E. Beise, U Maryland8 CIPANP 2009 data from: S. Dytman, et al., Phys. Rev. C 38, 800 (1988) B. Quinn, et al., Phys. Rev. C 37, 1609 (1988) calculation from R. Schiavilla see also R.S., J. Carlson, and M. Paris, PRC70, 044007 (2004). AV18 NN potential relativistic kinematics J.J. Kelly fit to nucleon form factors

9. 2-body effects in the D asymmetry E. Beise, U Maryland9 CIPANP 2009 leading term of the asymmetry axial form factor coefficient has ~ 15% correction from 2-body effects calculations from R. Schiavilla, see also R.S., J. Carlson, and M. Paris, PRC70, 044007 (2004).

10. E. Beise, U Maryland Jefferson Laboratory E ~ 6 GeV Continuous Polarized Electron Beam > 100  A up to 85% polarization concurrent to 3 Halls upgrade to 12 GeV now underway AC G0 CIPANP 2009 10

11. The G0 experiment at JLAB E. Beise, U Maryland Forward and backward angle PV e-p elastic and e-d (quasielastic) in JLab Hall C superconducting toroidal magnet scattered particles detected in segmented scintillator arrays in spectrometer focal plane custom electronics count and process scattered particles at > 1 MHz forward angle data published 2005 backward angle data: 2006-2007 CIPANP 2009 11

12. G0 Apparatus E. Beise, U Maryland One octant’s scintillator array 20 cm LH 2 Target CIPANP 2009 12

13. G0 Forward angle Results E. Beise, U Maryland D.S. Armstrong et al., PRL 95 (2005) 092001 EM form factors: J.J.Kelly, PRC 70, 068202 (2004) CIPANP 2009 13 HAPPEX-3 G0 Backward J. Liu, Univ Maryland 2006 JLab Thesis Prize

14. G0 Backward Angle E. Beise, U Maryland Electron detection:  = 108°, H and D targets Add Cryostat Exit Detectors (CED) to define electron trajectory Aerogel Cerenkov detector for  /e separation (p  < 380 MeV/c) 1 scaler per channel FPD/CED pair (w/ and wo/ CER) E e (MeV)Q 2 (GeV 2 ) 3620.23 6870.62 Common Q 2 with HAPPEX-III and PVA4 CIPANP 2009 14 Both H and D at each kinematic setting

15. Summary of the G0 Backangle Run RunCoulombsHoursGbytes data H 68786400600 H 362119550825 D 36266520800 D 687 I40520780 D 687 II15240340 total33023003450 Run start to run end ~ 8940 hours! Beise Run Coordinator report March 2007

16. G0 fun facts from Wikipedia: 1 “drop” (metric) = 0.05 mL 330 C ~ 0.1 “drop” of water Beise Run Coordinator report, March 2007 3.5 Tb ~ 5.5 x 10 8 inches of 6250 bpi tape ~ 14,000 km distance from Newport News to Katmandu, Nepal ~ 14,000 data tapes

17. We measured an asymmetry in detected rate when the beam helicity flips: We measured 2,000 asymmetries 15 times per second In 2400 hours, we measured 250 billion asymmetries (or, each asymmetry is measured 13 million times) Beise Run Coordinator report, March 2007 (14 FPDs x 9 CEDs x 2 CER states x 8 octants)

18. 362 MeV Hydrogen raw electron data Hz/uA d CIPANP 200918E. Beise, U Maryland octant # (azimuthal distribution) 687 MeV Hz/uA

19. 362 MeV 687 MeV Deuterium raw electron data Hz/uA d d CIPANP 200919E. Beise, U Maryland octant # (azimuthal distribution)

20. Blinding Factors × 0.75-1.25 H, D Raw Asymmetries, A meas Corrections Scaler counting correction Rate corrections from electronics Helicity-correlated corrections Background corrections Beam polarization Other measurements A(E i, Q 2 ) Q 2 Determination (from simulation) Analysis Strategy H, D Physics Asymmetries, A phys Unblind Electromagnetic radiative corrections (from simulation) P= 0.8578 ± 0.0007 (stat) ±.014 (sys) < 0.1 ppm CIPANP 2009 20E. Beise, U Maryland 4% on asymmetry ~ 10-50 ppm ± 0.003 GeV 2 < 1% of A phys

21. Rate Corrections H 687 MeV H 362 MeV Deadtimes (%) Correct the yields for random coincidences and electronic deadtime prior to asymmetry calculation randoms small except for D-687 (due to higher pion rate) Direct (out-of-time) randoms measured Validated with simulation of the complete electronics chain CIPANP 2009 21E. Beise, U Maryland Data set Correction to Yield (%) Asymmetry Correction (ppm) systematic error (ppm) H 36260.30.06 H 68771.40.17 D 362130.70.2 D 687961.8

22. Backgrounds: Magnetic Field Scans Use simulation shapes to help determine dilution factors Main contributions are Aluminum windows ( ~ 10%), pions (for D-687 data only). D-687 CED 7, FPD 13 CIPANP 2009 22E. Beise, U Maryland Data setAsymmetry Correction (ppm) systematic error (ppm) H 3620.500.37 H 6870.130.78 D 3620.060.02 D 6872.030.37

23. Experimental “Physics” Asymmetries E. Beise, U Maryland23 CIPANP 2009 Data SetAsymmetryStatSys ptGlobal H 362-11.420.840.260.37 D 362-17.020.790.390.19 H 687-46.142.360.800.72 D 687-55.873.221.910.62 Largest correction is due to the 85% beam polarization H: systematic uncertainties dominated by beam pol’n D-687: rate corrections and beam pol’n contribute about equally to the systematic uncertainty all entries in ppm PRELIMINARY – NOT FOR QUOTATION

24. Asymmetries to Form Factors E. Beise, U Maryland24 CIPANP 2009 Electromagnetic form factors: Kelly (PRC 70 (2004)) also used in Schiavilla calculation for D does not include new low Q 2 data from BLAST or JLab eventually use new fits (Arrington & Melnitchouk for p, Arrington & Sick for n) differences in fits become 0.5 – 1 % in the asymmetry Two-boson exchange corrections to Asymmetry: 0.5 -1.2% (see Tjon, Blunden & Melnitchouk, arXiv:0903.2759v1) includes D contributions, calculation for n in progress

25. Form Factor Results Using interpolation of G0 forward measurements G0 forward/backward PVA4: PRL 102 (2009) Q 2 = 0.1 GeV 2 combined (G0,HAPPEX, SAMPLE & PVA4) Global uncertainties G0 forward/backward SAMPLE Zhu, et al. PRD 62 (2000) CIPANP 2009 25E. Beise, U Maryland Some calculations: Leinweber, et al. PRL 97 (2006) 022001 Leinweber, et al. PRL 94 (2005) 152001 Wang, et al arXiv:0807.0944 (Q 2 = 0.23 GeV 2 ) Doi, et al, arXiv:0903.3232 PRELIMINARY – NOT FOR QUOTATION

26. Anapole form factor F  A (Q 2 ) E. Beise, U Maryland 26 2. F A (Q 2 ) is flat (Riska, NPA 678 (2000) 79) 1. F A (Q 2 ) is like G A (Q 2 ) 3. F A (Q 2 ) ~ 1 + Q 2 (Maekawa, Viega, van Kolck, PLB 488 (2000) 167) – (shown here are the most extreme set of model parameters) Three scenarios CIPANP 2009 PRELIMINARY – NOT FOR QUOTATION

27. Summary E. Beise, U Maryland Q 2 behavior of strangeness contribution to proton’s charge and magnetism: continue to be small first results for the Q 2 behavior of the anapole contributions to the axial form factor other results to come soon from G0:  transverse beam spin asymmetries (2-  exchange) in H and D  PV in the N-  transition: axial transition f.f.  PV asymmetry in inclusive   production 27 CIPANP 2009

28. 28 The G 0 Collaboration (backward angle run) Caltech, Carnegie Mellon, William and Mary, Hendricks College, Orsay, Grenoble, LA Tech, NMSU, Ohio, JLab, TRIUMF, Illinois, Kentucky, Manitoba, Maryland, Winnipeg, Zagreb, Virginia Tech, Yerevan Physics Institute CIPANP 2009 E. Beise, U Maryland PhD students: C. Capuano, A. Coppens, C. Ellis, J. Mammei, M. Muether, J. Schaub, M. Veerstegen, S. Bailey Analysis Coordinator: F. Benmokhtar

29. E. Beise, U Maryland backups CIPANP 2009 29

30. Preliminary Inelastic Asymmetries Background, radiative corrections not included [OUT + IN = 0.07 ± 5.1 ppm] [OUT + IN = -9.9 ± 10.5 ppm] PRELIMINARY – NOT FOR QUOTATION

31. Scaler Counting Issue with Electronics  Electronics sorts detector coincidences (CED i and FPD j ) into separate scaler channels  FPGA-based system in North American electronics (4 octants)  Because of error in FPGA programming, two short (~3 ns) pulses could be sent to scaler in < 7 ns  ~ 1% of events have such miscounts  Such pulse pairs can cause scaler to drop or add bits  Detailed simulation of ASIC with propagation delays between (flip flop) elements  Effect on asymmetry is <0.01 A phys  Test by cutting data; compare with French octants Data Simulation CIPANP 2009 31E. Beise, U Maryland

32. e - beam target CED + Cherenkov FPD E. Beise, U Maryland G0 Backward angle configuration Particle detection and identification Turn-around of the magnet Detection of the electrons (  e ~ 110°) Extensive simulation of background Need for new shielding around the target cell and at the magnet exit window Cryostat Exit Detectors (CED) to separate elastic and inelastic electrons Cherenkov detector  /e separation (both are recorded) 5 cm aerogel, n= 1.03 (OK for p  < 380 MeV/c), 90% efficient for e - and  rejection factor  100 From cosmic muons and test beam : 5-8 p.e. Special design for Magnetic shielding (SMS fringe field) CIPANP 2009 32

33. Correction due to misidentified pions red: pions blue: electrons 3 Ways to calculate runs with special beam structure providing timing reference allowing particle TOF PMT Multiplicity (two versus three of the cerenkov PMT’s firing) Pulse heights (waveform digitized) cerenkov detector 4 pmts aerogel # single photo electrons counts threshold   contamination to electron yield (A  ~ 0) D 362: 0.5% D 687: 4% 687 MeV CIPANP 2009 33E. Beise, U Maryland

34. G0 Forward Detection Scheme Detect scattered Protons: Magnet sorts protons by Q 2 at one setting Beam bunches 32 nsec apart Flight time separates p and   Beam spin flipped every 30 ms: + - - + pions inelastic protons elastic protons Det 8 CIPANP 2009 34

35. 2 ns time structure Polarization reversal: 30 Hz, random quartets (+--+, -++-) Slow helicity reversal: /4 wave plate IN and OUT Helicity-correlation properties: Polarized Beam Properties Beam Parameter Achieved (OUT-IN)/2 “Specs” charge asymmetry 0.09 +/- 0.082 ppm x position difference -19 +/- 340 nm y position difference -17 +/- 240 nm x angle difference -0.8 +/- 0.24 nrad y angle difference 0.0 +/- 0.14 nrad energy difference 2.5 +/- 0.534 eV Beam halo (out 6 mm) < 0.3 x 10 -6 10 -6 Charge Asymmetry Run Number w/ feedback  x (nm)  x (nrad)  E (keV)  y (nrad)  y (nm) CIPANP 2009 35E. Beise, U Maryland

36. Sep.-Dec. 2006 April 2006 March 2007 687 MeV Møller Results Beam Polarization Measurements of Møller asymmetry at 687 MeV  Low energy tune of Møller spectrometer Use Mott scattering for 362 MeV measurements  Mott asymmetry measured at 5 MeV in injector  New work on effect of background improves agreement with Møller P e (687 MeV) = 85.78 ± 0.07 ± 1.38% P e (362 MeV) = ± 2.05% Bottom Lines: CIPANP 2009 36E. Beise, U Maryland

37. Rate Corrections for Electronics  Deadtime & Random Coincidences Helicity Correlated Beam Corrections Dilution corrections: (inelastic electrons, target windows, misidentified pions ) EM Radiative Corrections (via Simulation) Beam Polarization P= 0.8578 ± 0.0007 (stat) ±.0138 (sys) From Raw asymmetries to unblinding 37 ~7-13 % correction to the yield, prior to computing the asymmetry < 0.1 ppm (E, charge, or position beam- induced false asymmetry) Inelastic electrons: ~1% to yield Al target windows ~12% to yield Pions: 5% for D-687, ~ 0 for rest ~4% correction to the asymmetry CIPANP 2009 E. Beise, U Maryland

38. Determining Form Factors Interpolation of G0 forward angle measurement CIPANP 2009 38E. Beise, U Maryland