Jefferson Lab and the 12GeV Upgrade

1. Jefferson Lab and the 12GeV Upgrade Ken Livingston, University of Glasgow Nuclear Physics UK Community Meeting Cosener’s House 11th & 12th June 2009 • Overview of Jefferson Lab and the 12 GeV upgade programme • CLAS Spectrometer (Hall B) • Latest results from the measurement of polarisation obresvables • CLAS12 • BigBite (Hall A) • Latest results on Gen - neutron electric form factor • Super BigBite • GlueX (Hall D)

2. Missing resonances and resonance spectroscopy • Cross sections not enough to separate broad, overlapping resonances • Angular distributions and polarization observables.

3. Linear Polarisation  Circular polarisation  → Y +  Nucleon recoil polarimiter x Longitudinally polarized nucleon targets  Transverse polarized nucleon targets ? Hyperons are “self analysing”  Polarization observables • + N→ N + m

4. Polarization observables in pseudoscalar meson production 4 Complex amplitudes - 16 real polarization observables. A complete measurement from 8 carefully chosen observables. Observable g target recoil I. S. Barker, A. Donnachie, J. K. Storrow, Nucl. Phys. B95 347 (1975).

5. Polarization observables - a simple example, S • Systematics of detector acceptance cancel out. • Only need to know Plin, the degree of linear polarization.

6. g8b: July 2005 Polarized photon energy range: 1.3 – 2.1 GeV Events (single charged particle in CLAS): 10 billion preliminary results:p0p, p+n.Mike Dugger, ASU CLAS data SAID High statistics. Good agreement with previous measurement. Data set extends to photon energy up to 2.1GeV

7. g8b preliminary results:hp, h’pMike Dugger, ASU SAID MAID Nakayama and Haberzettl effective lagrangian model High stats for h. Good agreement with previous measurements. Data set extends to photon energy up to 2.1GeV First measurement of S for h’ 2 Eg bins

8. g8b preliminary results - K+L and K+S0Craig Paterson, Glasgow gp-> K+L -> K+pp-gp-> K+S0 -> K+Lg -> K+pp-g Single polarization observablesS Photon asymmetryP Recoil polarization (induced pol. along y)T Target asymmetryDouble polarization observablesOx Polarization transfer along xOz Polarization transfer along z LS0 figure by R.Schumacher, CMU

9. g8b preliminary results - K+L • Results compared with previous results from GRAAL • 7, 50MeV Energy bins • 1175 -> 1475MeV • Good agreement with previous results PRELIMINARY

10. g8b preliminary results - K+L • Results compared with previous results from LEPS • 6, 100MeV Energy bins • 1550 -> 2050MeV • More bins for our data Increase the angular coverage to backward angles PRELIMINARY

11. g8b preliminary results - K+L Ox/Ozextracted from fit to 2d asymmetry T Target asymmetry from 2d asymmetry (not shown) P Recoil pol. from acceptance corrected proton dist. G8b GRAAL CLAS J.W.C. McNabb, et al. (CLAS) Phys. Rev. C 69, 042201(R) (2004).

12. g8b preliminary results - K+L Double polarization ovservable Ox • Results compared with Regge-Plus-Resonance model from Gent group • - Large Polarizations! • Some evidence for an important role for missing D13(1900) state • Poor agreement at low energy PRELIMINARY

13. g8b preliminary results - K+L Full lamba polarization ? With circularly polarized photons – “fully polarized lambda” R. Bradford et al. (The CLAS Collaboration), Phys. Rev. C 75, 035205 (2007). - Full polarization at forward angles - Not repeated over full kinematic range - More relations can be tested PRELIMINARY (P2 + Ox2+Oz2)1/2

14. g13 meson photoproduction, polarized photons on LD2 gn (p)-> p+p (p) Daria Sokhan, Edinburgh MAID SAID Previous data

15. g13 meson photoproduction, polarized photons on LD2 gp (n)-> K+L0 (n) Russell Johnstone, Glasgow gn (p)-> K0sL0(p) Neil Hassall, Glasgow

16. g9 FROST – FROzen Spin Target Meson photoproduction with linearly and circularly polarized photons on polarized target E02-112: γp→KY (K+Λ, K+Σ0, K0Σ+)‏ E03-105/E04-102: γp→π0p, π+n E05-012: γp→ηp E06-013: γp→π+π-p g9a running conditions November 3, 2007– February 12, 2008 Longitudianally polarized target Circularly and linearly polarized photon beam 0.5-2.4 GeV Trigger: at least one charged particle in CLAS

17. g9aFROST sample analysis of gpp+nEugene Pasyuk, ASU Helicity asymmetry E • Select p+ applying cut on b vs. p • Vertex cuts • Select missing neutron Raw asymmetry butanol 12C CH2 butanol 12C CH2 Preliminary Based on ~2% of statistics

18. g9 FROST outlook • Circularly polarized photon beam on longitudinally polarized target • E P, Lx/Lz, Cx/Cz • Linearly polarized photon beam on longitudinally polarized target • , G, P, (Tx/Tz) Ox/Oz • Circularly polarized photon beam on transversely polarized target • T, F, P,Tx/Tz, Cx/Cz • Linearly polarized photon beam on transversely polarized target • , H, T, P, (Lx/Lz)‏ Upon completion of g9b for the first time we will have complete set of observables in Kaonphotoproduction and nearly complete for all other mesons, which will allow model independent extraction of the amplitude for subsequent extraction of baryon resonances and their properties. g9a Complete g9b scheduled for 2010

19. p q g n p+ Recoil polarimetry possibilities (D. Watts, Edinburgh) g + p → p+ n with (n,p) scatter (detect p+p) Mx(gp→p++X)

20. Polarimetry: from hadronic reactionR. Beck, Mainz -> Bonn Use reaction with a known photon asymmetry • Can be high statistics • Very good relative monitor of polarization • Combined beam, target polarization. • Non-indpendent – depends on specific expt • Need very good systematics or calibration • Awaiting MAMI polarized target and polarised photon beam in 2nd half of 2007 • Recent preliminary results from JLab (g8b)‏ • Proton target • Back to back charge particles in Start Counter • Atomic or hardonic ? • Asymmetry from ~20mins DAQ data • Constant with E from 1.3GeV – 1.9GeV

21. Measurements with photon beam profile detectorD. Glazier, Glasgow 1st Measurement of 2D photon enhancement for coherent bremsstrahlung (MAMI,Mainz) paper in preparation below peak coherent peak above peak Coherent peak at 300Mev, MAMI electron beam energy 855MeV • Good agreement with coherent bremstrahlung calculations • Improvements in incoherent component, collimation + multiple scattering. • No evidence of high energy photons from quasi channeling. • Investigation of 2D strip detector for polarimetry

22. CLAS coherent bremsstrahlung facility • Tagging spectrometer with high rate, good energy and timing resolution • High precision goniometer (GWU) • High quality, thin diamond (Glasgow) • Tight photon beam collimation (ISU) • Polarimetry Photon energy P > 90% Peak > 90% pol. “A device called a goniometer tilts the diamond, much like a lady turning her hand to admire the sparkle of a new ring.” - JLAB On Target Magazine

23. g8b preliminary results - K+L • K+LPhoton Asymmetry, S, extracted from cos(2f) fit to azimuthal kaon distribution • Fits shown for 1 energy bin • 340 (20E, 17q) kinematic bins • Almost full angular coverage

24. g8b preliminary results - K+S0 • Results compared with previous results from GRAAL • 7, 50MeV Energy bins • 1175 -> 1475MeV • Good agreement with previous results PRELIMINARY

25. g8b preliminary results - K+S0 • Results compared with previous results from LEPS • 6, 100MeV Energy bins • 1550 -> 2050MeV • More bins for our data!!! Increase the angular coverage to backward angles PRELIMINARY

26. Peak > 90% pol. PRELIMINARY K.Livingston, Glasgow J.Santoro, CUA Polarimetry: from pair (e+,e-) productionH.Schmieden, Bonn • Well described by QED, but experimentally difficult – small opening angle e+ e- • Pair production simulations by Kharkov group • Polarimeter built and tested at Sping8, recently tested at Jlab • Polarimeter to be based on Jlab design • Microstrip detectors, or pixel detectors (Atlas group) • Bonn student completed 10 months exchange in Glasgow now to be full time in Bonn.