1. PN12 Workshop JLab, Nov 2004 R. Michaels Jefferson Lab Parity Violating Neutron Densities Z of Weak Interaction : Clean Probe Couples Mainly to Neutrons Low Q elastic nucleus scattering ( T.W. Donnelly, J. Dubach, I Sick ) 2 0 In PWIA -- but must account for Coulomb distortions (C. J. Horowitz)

2. PN12 Workshop JLab, Nov 2004 R. Michaels Jefferson Lab Parity Violating Asymmetry + 2 Applications : Nucleon Structure (strangeness) Nuclear Structure (neutron density) Standard Model tests ( )

3. PN12 Workshop JLab, Nov 2004 R. Michaels Jefferson Lab Z sees the neutrons 0 proton neutron Electric charge 1 0 Weak charge 0.08 1

4. PN12 Workshop JLab, Nov 2004 R. Michaels Jefferson Lab PREX in Hall A at JLab Hall A Polarized e - Source CEBAF Hall A Pol. Source Lead Foil Target

5. PN12 Workshop JLab, Nov 2004 R. Michaels Jefferson Lab Measured Asymmetry Weak Density at one Q 2 Neutron Density at one Q 2 Correct for Coulomb Distortions Small Corrections for G n E G s E MEC Assume Surface Thickness Good to 25% (MFT) Atomic Parity Violation Mean Field & Other Models Neutron Stars R n Lead Parity Physics Impact of

6. PN12 Workshop JLab, Nov 2004 R. Michaels Jefferson Lab Lead Parity: pins down the symmetry energy (1 parameter) ( R.J. Furnstahl ) energy cost for unequal # protons & neutrons

7. PN12 Workshop JLab, Nov 2004 R. Michaels Jefferson Lab Pb Parity : Neutron Stars Crab Pulsar ( from hubblesite.org ) ( C.J. Horowitz, J. Piekarweicz ) R calibrates EOS of Neutron Rich Matter Combine R with Neutron Star Radius Some Neutron Stars too Cold n n Crust Thickness Explain Obs. Glitches in Pulsar Frequency ? Exotic Core ? (strange matter, quark star) Cooling by neutrino emission (URCA) 0.2 fm URCA probable, else not

8. PN12 Workshop JLab, Nov 2004 R. Michaels Jefferson Lab Optimum Kinematics for Lead Parity: E = 850 MeV, = 0.5 ppm. Accuracy in Asy 3% 1 month run 1% in R n

9. PN12 Workshop JLab, Nov 2004 R. Michaels Jefferson Lab High Resolution Spectrometers Elastic Inelastic detector Q Dipole Quad Spectrometer Concept: Resolve Elastic target

10. PN12 Workshop JLab, Nov 2004 R. Michaels Jefferson Lab Septum Magnets (INFN) Electrons scattered at 6 deg sent to the HRS at 12.5 deg. Superconducting magnets Commissioned 2003-4

11. PN12 Workshop JLab, Nov 2004 R. Michaels Jefferson Lab Integrating Detection PMT Calorimeter (for lead, fits in palm of hand) ADC Integrator electrons Integrate in 30 msec helicity period. Deadtime free. 18 bit ADC with < 10 nonlinearity. But must separate backgrounds & inelastics ( HRS). - 4

12. PN12 Workshop JLab, Nov 2004 R. Michaels Jefferson Lab Lead Target Liquid Helium Coolant Pb C 208 12 Diamond Backing: High Thermal Conductivity Negligible Systematics Beam, rastered 4 x 4 mm beam

13. PN12 Workshop JLab, Nov 2004 R. Michaels Jefferson Lab Halfwave plate (retractable, reverses helicity) Laser Pockel Cell flips helicity Gun GaAs Crystal e beam - Rapid, random helicity reversal Electrical isolation from rest of lab Feedback on Intensity Asymmetry Polarized Electron Source

14. PN12 Workshop JLab, Nov 2004 R. Michaels Jefferson Lab Beam Asymmetries A raw = A det - A Q +  E +  i  x i natural beam jitter (regression) beam modulation (dithering) Slopes from

15. PN12 Workshop JLab, Nov 2004 R. Michaels Jefferson Lab “Energy” BPM BPM Y2 BPM Y1 BPM X1 BPM X2 Scale +/- 100 nm Position Diffs avg ~ 10 nm Negligible Systematic Error Helicity Correlated Differences: Position, Angle, Energy

16. PN12 Workshop JLab, Nov 2004 R. Michaels Jefferson Lab Polarimetry Electron only Photon only Preliminary: 2.5% syst (  only) Møller:  P e /P e ~ 3 % (foil polarization)  Compton: 2% syst. At present 2 analyses based on either electron or photon detection Superlattice: P e =86% !

17. PN12 Workshop JLab, Nov 2004 R. Michaels Jefferson Lab Upgrade of Compton Polarimeter (Nanda, Lhuillier) To reach 1% accuracy: Green Laser Integrating Method

18. PN12 Workshop JLab, Nov 2004 R. Michaels Jefferson Lab Summary -- Neutron Skin R is Fundamental to Nuclear Physics HAPPEX program to demonstrate most technical aspects Polarimetry Upgrade needed Planned 2-day test run in 2005 n

19. PN12 Workshop JLab, Nov 2004 R. Michaels Jefferson Lab extra slides --

20. PN12 Workshop JLab, Nov 2004 R. Michaels Jefferson Lab Moller Polarimetry with Atomic Hydrogen Target ( E. Chudakov, V. Luppov) H atoms Solenoid 8T Trap beam Ultra Cold Traps Polarization ~ 100% Density Lifetime > 10 min Polarimetry 1% stat. err. in 30 min at 30 A Low background High beam currents allowed (100 A) Goal: ~ 0.5 % systematic error

21. PN12 Workshop JLab, Nov 2004 R. Michaels Jefferson Lab controls effective analyzing power Tune residual linear pol. Slow helicity reversal Intensity Attenuator Polarized Source High P e High Q.E. Low A power Optical pumping of solid-state photocathode High Polarization Pockels cell allows rapid helicity flip Careful configuration to reduce beam asymmetries. Slow helicity reversal to further cancel beam asymmetries

22. PN12 Workshop JLab, Nov 2004 R. Michaels Jefferson Lab Beam Modulation to Calibrate Sensitivity to Beam Systematics

23. PN12 Workshop JLab, Nov 2004 R. Michaels Jefferson Lab P I T A Effect Laser at Pol. Source Polarization I nduced Transport Asymmetry where Transport Asymmetry Intensity Asymmetry drifts, but slope is ~ stable. Feedback on