6 GeV Program Overview Rolf Ent PAC38 Meeting August 22 nd 2011

1. 6 GeV Program Overview Rolf Ent PAC38 Meeting August 22nd 2011

2. Good FY11 Operations • Did run as promised until May 13, 2011 & started 6 Month Shut Down work • Cumulative delivered beam used: Hall A 101% (routine running) • Hall B 70% (HDIce delay) • Hall C 82% (Qweak catching up)

3. Ongoing 6 GeV Program • Issues remaining: • Completion of g2p/GEp apparatus in Hall A • Proof of polarized HDIce operations in Hall B • Sufficient beam in Hall C

4. Hall A: Ongoing 6 GeV Program Now Underway Not shown on the FY2010 Schedule is the APEX test run; it took place just after PREx

5. Lead (208Pb) Radius Experiment : PREX Elastic Scattering Parity-Violating Asymmetry Z0 : Clean Probe Couples Mainly to Neutrons Applications : Nuclear Physics, Neutron Stars, Atomic Parity, Heavy Ion Collisions PREX PREX Relativistic mean field A neutron skin of 0.2 fm or more has implications for our understanding of neutron stars and their ultimate fate Nonrelativisticskyrme • The Lead (208Pb) Radius Experiment (PREX) finds neutron radius larger than proton radius by +0.35 fm (+0.15, -0.17). • This result provides model-independent confirmation of the existence of a neutron skin relevant for neutron star calculations. • Follow-up experiment to reduce uncertainties by factor of 3 andpin down symmetry energy in EOS.

6. Strangeness Contribution to Nucleon Form Factors Pink line represents 2% of the proton form factors (in the same combination of electric and magnetic as the strange form factors)  strange quarks represent less than 2% of the proton form factors. HAPPEx-III results final, publication in preparation - accurate measurement at Q2 = 0.6 GeV2, completing the parity-violating program constraining the contributions of strange quarks to the proton’s charge & magnetization. - contributions to these distributions are found to be minimal. - strange quarks do not play a substantial role in the long-range electromagnetic structure of nucleons Completes Performance Measure HP4

7. Searches for a gauge boson A’ – APEX Test Run Result Electroproduction of A’ decay • Published results : • Beam dump searches: SLAC:E137, 141; FNAL: E774 • electron and muon (g-2), limits • BaBar, U(3s)-> g and m+m- (inferred limit) • KLOE, mass of an e+e- pair (bump search) • APEX test run, mass of e+e- pair – arXiv:1108.2750 • MAMI – APEX type scheme • Future searches for a new force carrier: • APEX – electron-nucleus fixed-target, an e+e- pair in two focusing spectrometers • HPS – same, the e+e-, m+m- pairs in a custom Si-tracker magnetic spectrometer • DarkLight – an internal target with an electron beam in Jefferson Lab ERL, detect an e+e- pair and e’p • VEPP3 – a positron beam incident on an internal H2 target, missing mass in (e+e-, g X) • MAMI – APEX type scheme with lower beam energy

8. Hall A: Upcoming Program up to May 2012 Shutdown for 12-GeV installation Last piece of incremental equipment funding provided by DOE/NP Removed from schedule due to extended time needed for g2p /Gep transitions • Hall A submitted draft plan for initial operations in FY14-FY16 to Director, expected to continue iterations in 2011 • MIE for Super Bigbite System submitted to DOE, DOE science & technical review scheduled for October 13 + 14 • Draft MIE proposal for Moller experiment in hand

9. Hall B: Ongoing 6 GeV Program Almost … Technical feasibility to be established

10. April-May/11 • In-beam Cryostat (IBC) passed ASME pressure-code tests • IBC installed in CLAS and aligned • LHe circuit cooled; auto-fill from ESR established • magnets (3 superconducting, 1 normal) commissioned at full current • in-beam NMR successfully tested • test transfer of solid HD from HDice Lab -to- Hall B –to- IBC • low target temperatures prevented by blocked capillary HDice commissioning First photo sent to us from HDIce in Hall B April 2011

11. May-August/11 • • Blocked capillary was found to be piece of low-tech solder • • Achieved 48 mK July 31, 2011 (and I believe they reached 43 mK in the end) • •Produced additional three spare polarized target batches in July/August • • IBC moved to Hall B again last week • Start cooling when ESR availability permits • Need to do HD spin transfer tests in Hall HDice commissioning

12. ep e’π0X • A 5.75 GeV polarized electron beam was used with CLAS to measure the azimuthal dependence of the beam spin asymmetry for in a large xB, and PT range. • Significant asymmetries are observed for 0.3<PT<0.7 GeV and in the range xB≤ 0.4. Beam-spin asymmetry for π0 SIDIS Structure function FLU receives contributions from contributions from the convolution of twist-2 and twist-3 distribution and fragmentation functions, e.g. twist-2 Boers-Mulders DF, Collins FF and twist-3 DFse and g T The observed asymmetry for π0 suggests that the major contribution to pion beam SSA originates from spin-orbit correlations. M. Aghasyan et al. (CLAS), arXiv:1106.2293, PLB accepted

13. Hall C: Ongoing 6 GeV Program Now Underway

14. Hall C: Qweak status • Precision measurement of the proton’s weak charge in the simplest system • Search for parity-violating new physics up to the ~ 2 TeVscale • No show-stoppers found, on track for proposed 4% precision on QpWeak • Asymmetry Width • Beam: routine data-taking at 165 μA @ ~88% polarization (and tests up to 180 mA) • Helicity-correlated properties • acceptable! σ = 236 ppm Status at 05/13/11 Above: 6.5 minutes of data @ 165 μA Total detected rate = ~5.83 GHz Pure counting statistics: ~215 ppm + detector energy resolution -> 232 ppm + beam current normalization -> 235 ppmagrees with data

15. Evolution of PVES Helicity Correlated Beam Properties

16. The QWEAK Experiment: Measurement of the Proton’s Weak Charge QPW = - 2 (2C1u + C1d ) Elastic ep Scattering Parity-Violating Asymmetry Run I (completed) Anticipated QPW uncertainty: Run I + Run II Isoscalar weak charge sin2qW MS Theory Curve : J. Erler, M. J. Ramsey-Musolf et al., See Particle Data Group 2010 Young, Carlini, Thomas & Roche, PRL Q (GeV) Isovector weak charge • First direct measurement of the proton’s weak charge. • Precision determination of the neutral current weak couplings to the quarks (C1u & C1d). • Mass scale reach for parity-violating new physics at expected final uncertainty (95% CL) is ~2.3 TeV. Anticipated constraints if QPW is consistent with the Standard Model.

17. The TAC Process Added for PAC38 an independent technical review process, and tried this on five proposals Please note that for this PAC, we have asked a team of experienced and critical scientists, representing all Hall groups to look at some of the more technically challenging proposals. You will find the comments of this technical review attached to the individual reports. Our hope is, that this will be useful to both the PAC and the experiment proponents, and adds a layer of coherence to the technical review process. If a proposal was selected, this simply reflects our feeling that the proposal could benefit from this independent technical review.  On the other hand, if a proposal was not selected, it does not mean it will not have technically challenging components. We welcome any feedback you might have on the use of this independent technical review process.

18. The 12 GeV PAC Process (cont.) • Planning the Initial Operation in Each Hall • Following the model used for the initial CEBAF program, ~2-3 years before start of 12 GeV operation hall-by-hall: • Each hall will provide for PAC review and comment (and potential improvement) a “commissioning and early running” plan folding in guidance of DOE/NP on early operations in FY14-FY16. • The collaboration’s tradeoff between the best possible science and the realities of commissioning equipment. • 3 years after the start of physics in each hall, jeopardy will begin. • Status: Hall A early draft submitted to Director and iterations ongoing, Hall B plan started, Hall C plan just discussed at Summer workshop. Submit all for PAC review and comments Summer 2012?