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Baryon spectroscopy at CLAS and CLAS12

Baryon spectroscopy at CLAS and CLAS12. Ken Livingston, University of Glasgow, Scotland For the CLAS collaboration. Baryons’10, Dec 2010, Osaka, Japan. Hadron spectroscopy at CLAS The N* programme CLAS 12 Summary. Hadron spectroscopy at CLAS The N* programme CLAS 12 Summary.

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Baryon spectroscopy at CLAS and CLAS12

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  1. Baryon spectroscopy at CLAS and CLAS12 Ken Livingston, University of Glasgow, Scotland For the CLAS collaboration Baryons’10, Dec 2010, Osaka, Japan • Hadron spectroscopy at CLAS • The N* programme • CLAS 12 • Summary • Hadron spectroscopy at CLAS • The N* programme • CLAS 12 • Summary • Study of nucleon resonances: • Measurement of the transition form factors • Search for missing states • Strangeness production • L and S production • Cascade spectroscopy • Search for “unconventional states” • high statistics search of pentaquark states • search for hybrid mesons • Study of nucleon resonances: • Measurement of the transition form factors • Search for missing states • Strangeness production • L and S production • Cascade spectroscopy • Search for “unconventional states” • high statistics search of pentaquark states • search for hybrid mesons > 100 analyses in progress

  2. With D13 Without D13 Missing baryon resonances After Cx, Cy from CLAS, revised as most likely P13. Eur Phys J A34 (07) 243 Mart & Benhold, Phys. Rev. C 61 012201(R) (1999) • Clear indication of resonances in γp cross section for many channels • Constituent quark models predict many resonances, but several missing • Mostly from πN scattering and single π photoproduction • Really missing or undetected since weak coupling to these channels • Try other channels. Eg. K photoproduction • Eg. Cross sections show some hints of new D13. • Better to look at angular distributions and polarization observables.

  3. Polarization observables in pseudoscalar meson production 4 Complex amplitudes: 16 real polarization observables. Complete measurement from 8 carefully chosen observables. πN has high statistics but in KY recoil is self-analysing ☻ πN KY recoil targγ γ targ recoil ☻☻☻ ☻☻☻ ☻☻☻ ☻☻☻ ☻☻☻ ☻☻☻ ☻☻☻ ☻☻☻ ☻☻☻ I. S. Barker, A. Donnachie, J. K. Storrow, Nucl. Phys. B95 347 (1975). Complete, and over-determined circ polarized photons longitudinally polarized target transversely polarized target linearly polarized photons

  4. Jefferson Lab LINAC LINAC A C B • Continuous • Electron • Beam • Accelerator • Facility • E: 0.75 –6 GeV • Imax: 200mA • RF: 1499 MHz • Duty Cycle:  100% • s(E)/E: 2.5x10-5 • Polarization: 80% • Simultaneous distribution to 3 experimental Halls Injector Experimental Halls

  5. Electromagnetic Calorimeter lead/plastic scintillator, 1296 PMTs Torus Magnet 6 Superconductive Coils Target +  start counter e mini-torus Drift Chamber 35,000 cells Time of Flight Plastic Scintillator, 684 PMTs Cherenkov Counter e/ separation, 256 PMTs CEBAF Large Acceptance Spectrometer

  6. Tagged photons at CLAS • Tagged bremsstrahlung photons up to 6GeV. • Timing resolution < 1 beam bucket. • Circularly polarized • up to ~80% now standard • Linearly polarized • coherent bremsstrahlung up to >90%.

  7. Linear Polarisation  Circular polarisation  → Y +  Nucleon recoil polarimiter x Longitudinally polarized nucleon targets p n 2011 Transverse polarized nucleon targets p n 2011 Hyperons are “self analysing”  Polarization observables at CLAS • + N→ N + m

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

  9. 1st pol. observables in K photoproduction on p at CLAS.P, Cx and Cz R. Bradford et al., Phys. Rev. C 75, 035205 (2007). → L fully polarised

  10. g8b, July 2005 Lin. polarized photon energy range: 1.3 – 2.1 GeV preliminary results:p0p, Mike Dugger, ASU CLAS data SAID Beam Asymmetry Σ • Very high statistics. Good agreement with previous measurement. • We have P well determined – expect <5% systematic error in P. • ~10MeV Eg bins, and will extend up to 2.1GeV • Similar for p+n, hp, h’p

  11. 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

  12. 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 LEPS also recently have some consistent, new points at backward angles. Hicks et al., PRC 76, 042201(R) (2007). PRELIMINARY

  13. 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. P Recoil pol. g8b GRAAL CLAS J.W.C. McNabb, et al. (CLAS) Phys. Rev. C 69, 042201(R) (2004).

  14. G8b Summary Several analyses at advanced stage: • K+L , K+S0 • Single (P,T,S) and double (Ox,Oz) polarization observables • High stats, wide coverage, some 1st measurements • Prelim results already being used as input to models • p0p, p+n, hp, h’p • Photon asymmetry (S) • Very high statistics • wp, p+p-p • Photon asymmetry (S) • 1st measurement …. several publications expected next year

  15. g9 FROST – FROzen Spin Target (butanol = C4H9OH) 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 Racetrack coils for transverse polarization 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 Target Pol > 80%, Relaxation time > 1600hrs – better that design goals g9b March – July 2010 Transversely polarized target

  16. g9aFROST sample analysis of gpp+nEugene Pasyuk, ASU. Jo McAndrew, Edinburgh 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 Preliminary, also in progress for KY. Based on ~2% of statistics

  17. Measurements on n (Deuterium) target • G10. Unpolarized photons on Deuterium • 1st measurement of σ for the γ n → K+Σ- Sergio Anefalos Pereira, INFN. Phys. Lett. B 688 (2010) 289-293 • Detect p- n, K+ • Σfrom p- n inv. mass • CLAS Data ▲ LEPS _____ Gent RPR model • Circularly and linearly polarized photons on n (g13, Deuterium target) • γ n → K+Σ-analysis for polarization observables underway. Edwin Munevar, GWU

  18. Measurements on n (Deuterium) target G13 1st measurement of Beam Asymmetry gn (p)-> K0s L0(p) Neil Hassall, Glasgow PRELIMINARY Single, and double polarization observables in progress

  19. Measurements on n (Deuterium) target • G13b. Linearly polarized photons on n (Deuterium) • Measurement of S for γ n → p- p Daria Sokhan, Edinburgh VERY PRELIMINARY! ~ 30 % of the data Assumed polarisation P = 1 Existing data: • Alspector, PRL 28, 1403 (1972). • Abrahamian,SJNP 32, 69 (1980). • Adamyan, JPG 15, 1797 (1989). Only statistical error is shown!

  20. Measurements on n (Deuterium) target HDIce slide still to be added here.

  21. Construction of the new Hall D Upgrade of the arc magnets CHL-2 Upgrade of the instrumentation of the existing Halls 12 GeV CEBAF Beam Power: 1MW Beam Current: 90 µA Max Pass energy: 2.2 GeV Max Enery Hall A-C: 10.9 GeV Max Energy Hall D: 12 GeV

  22. Forward Tagger Spectroscopy with CLAS12 • electron scattering at “0” degrees (LowQ, post-target tagging): low-Q2 virtual photon  real photon • photons tagged by detecting the scattered electron • quasi-real photons are linearly polarized and the polarization can be determined event by event • high luminosity on thin (gas)- targets • can exploit CLAS12 PiD for final states with strangeness • Complementary to GLUEX Coh. Brem. photon beam • Parasitic running The construction of Low Q Tagging Facility or Forward Tagger has been proposed to continue the spectroscopy program with CLAS12 using quasi-real photoproduction A new physics programme • Meson spectroscopy • Spectroscopy on H target and search for exotics • Spectroscopy on 4He and other gas targets • Hadron spectroscopy • Heavy mass baryon resonances (Cascades and W-) • Compton scattering • Meson polarizabilities • Large -t physics • T-GPDs < 6 GeV Meson Spectroscopy at CLAS and CLAS12, Carlos Salgado SP2, Wed 14.00

  23. Summary to be improved • CLAS has large hadron spectroscopy programme • Focus here was on N* with Kaon and Pion channels • Very high stats single pol measurements for pi, eta • Data for complete measurement KL, SL on p already taken • Analysis underway • Data for complete measurement KL, SL n next year (HDIce) • Many results close to publication from g8 • Much awaited input for models • Could definitive N* answers be only a few years away? • CLAS 12 • A forward tagger offers a whole new hardon spectrosopy programme

  24. Extra slides

  25. K production on n. Deuterium target How good a “free” neutron target is Deuterium ? G13. Compare photon asymmetry of gp (n)-> K+L0 (n) withgp -> K+L0 (free and bound p) gp (n)-> K+L0 (n) Russell Johnstone, Glasgow × Free ● Quasi free PRELIMINARY photon asymmetry S S0 L0 Cosqcm (-1.0 - +1.0) Each plot is 200MeV photon energy bin 1100-2150MeV Free and quasi-free proton Quasi free neutron good approx. to free, here.

  26. K production on n. Deuterium target G13 gn (p)-> K0sL0(p) gn (p)-> K0s S0(p) Neil Hassall, Glasgow

  27. K production on n. Deuterium target G13 1st measurement of Beam Asymmetry gn (p)-> K0sL0(p) Neil Hassall, Glasgow PRELIMINARY Single, and double polarization observables in progress

  28. g8b data. g + p → p+ n with (n,p) scatter (detect p+p) q Mx(gp→p++X) Angle between Pncalc and Ppmeasured K.Livingston Recoil polarimetry possibilities ? n(q,f) =no(q){1+A(q)[Pycos(f)–Pxsin(f)] - How to do this for 4p detector x and y (transverse) components of nucleon polarisation Nucleon polarimeter for CB@MAMI, D. Watts, Edinburgh Graphite p q n g p+ Start counter

  29. 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

  30. 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

  31. 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

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

  33. 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

  34. 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.

  35. 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

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