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Complete pseudoscalar photo-production measurements

Complete pseudoscalar photo-production measurements. F.J. Klein (CUA) NSTAR 2011, Newport News, VA, May 16-20, 2011. photoproduction cross section. Baryon spectrum. N*. D. PDG listing. Quark model coupling to π N decreases rapidly with energy

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Complete pseudoscalar photo-production measurements

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  1. Complete pseudoscalar photo-production measurements F.J. Klein (CUA) NSTAR 2011, Newport News, VA, May 16-20, 2011

  2. photoproduction cross section

  3. Baryon spectrum N* D PDG listing

  4. Quark model • coupling to πN decreases rapidly with energy • many more resonances predicted than experimentally observed • only supermultiplets filled that are consistent with di-quark models • known baryon spectrum chiefly determined from πNreactions Capstick - Roberts

  5. γN→KΛ Model comparison SAPHIR data (1998) triggered discussion on “missing” D13(1960): Mart-Bennhold: evidence for D13(1890) Saghai: bump in s due to u-channel and off-shell effects Q.Zhao: no need for D13(~1900) Janssen: s-p wave interference (P11(1840)) SAID: no need for D13(~1900) Penner-Mosel: evidence for D13(1900) Waluyo-Bennhold: strong evidence for D13(1950) Sarantsev-Klempt: evidence for radial excitation of D13(1520) at 1950 MeV note: ~20% normalization offset Mart: refit with multipole model: P13(1900) Torres-Meissner: KKN bound state Nikanov: refit of Bonn-Gatchina model: P13(1900) • new dσ/dΩdata: • e.g. CLAS (PRC 81 (2010)): broader energy range, • good agreement with previous CLAS data • new polarization data: • e.g. CLAS, CBELSA, CB@MAMI, GRAAL • lack of constraining data

  6. γp→K+Λ database (SAID) recoil polarization P differential cross section dσ/dΩ … and 3 data points for T (from 1978) NO double polarization observables! beam asymmetry Σ

  7. Frozen-spin target programs: Circularly and plane polarized photons on (a) long. and transv. polarized butanol target: • CLAS: γp→π0p, π+n,ηp, γp→π+π-p, K+Λ, K+Σ0 • CBELSA: γp→π0p, ηp, γp→π0π0p • CB@MAMI: γp→π0p, ηp, γn→π0n, ηn (b) long. polarized HD target: • CLAS: γn→π-p,γn→π+π-n,γn→K0Λ, K0Σ0, K+Σ- all 15 polar. observ. for K+Λ, K+Σ0 7 polar. observ. forπ0p, π+n, ηp 7 polar. observ. forπ0p, ηp →talk by F. Klein (Friday) 9 polar. observ. forπ0N, ηN →talk by H.J. Arends (Friday) 13 polar. observ. for K0Λ , 4-5 polar. observ. for K0Σ0, K+Σ- 3 (7) polar. observ. for π-p

  8. Polarization observables in 0- meson production • 4 complex amplitudes (16 bilinear combinations) • ≥ 8 carefully chosen measurements for complete set • polar. target: all 4 combinations of beam (lin,circ) and target (long,trans) • for Λ, Σ0,+ (self-analyzing) or recoil polarimeter complete set • all observables as fcts of √s and cosθ • use algebraic relations to check for systematics long. and transv. polar. target (together with polar. photons) polarized photons on liq. H2 or D2

  9. Extraction of polarization observables polarized cross section (0- photoproduction): α=orientation of photon polarization β=orientation of target polarization PT=linear photon polarization Po=circular photon polarization Pz=longitudinal target polarization Pxy=transverse target polarization Extraction of spin observables via Fourier analysis of polarized cross section in each (E,cosθ) bin

  10. γp→π0p, π+n (sample PWA) sample PWA using MC data generated from SM02 greatly reduced uncertainties

  11. γp→π0p, π+n Impact on Single Energy Solutions

  12. Frozen-spin butanol target e.g.FROST design g9a (2008/9) g9b (2010) polarization: ±85% +82% +85% -85% -93% relaxation time: 500 h 2700 h (+) 3500 h (+) 1400 h (-) 1900 h (-) (~5%/day) (<1.5%/day) (<1%/day) base temp: 50 mK 30 mK 25 mK Ch. Bradtke, PhD Bonn

  13. HDice at CLAS target: Ø15mm x 50mm 3g of solid H-D composite density: 0.147 g/cm3 2050 cooling wires (Al) Ø50mm PV(D)~40%, P(H)~40% or PV(D)~0%, P(H)~75% Polarize at 15T &12 mK and operate at 1T & 250mK 1/e relaxation time: τ1~1.5 years additional “empty cell” downstream: subtraction of Al background LEGS

  14. Why additional neutron data? Amplitudes for photo-producing pseudoscalar mesons have 3 components: coupling of isoscalar & isovector components of photon field to nucleon for N* (I=1/2) sign only resolved by proton and neutron data D* (I=3/2) couplings determined by proton data

  15. Extraction of observables from butanol target FROST (CLAS) e.g. circ. pol. beam on long. pol. target: Comparison of yields for anti-aligned/aligned spins subtract background from bound nucleon reaction using additional Carbon foil

  16. π0pphotoproduction beam asymmetry Σ for γp→π0p (g8b, analysis ASU)

  17. π0beam-target asymmetries helicity asymmetry γp→π0p • → Talk byH. Iwamoto (Wed. II-A) • preliminary data for Eγ = 0.5-2.4GeV • models consistent with data at Eγ < 1.35 GeV preliminary CLAS –g9a GDH Mainz

  18. π0beam-target asymmetries beam – target asymmetry G for γp→π0p (CBELSA) →Talk by Jan Hartmann (Wed. II-A)

  19. π+photoproduction beam asymmetryΣ for γp→π+n (CLAS g8b, analysis ASU) • large energy and angular coverage • good agreement with previous data

  20. π+helicity asymmetry E circ. pol. beam – long. pol. target(FROST) preliminary →Talk by S. Strauch (Wed. II-A) • ~700 data points for 1.25 < W < 2.3 GeV • good agreement with SAID & MAID for W<1.7 GeV

  21. π+beam-target asymmetry G plane pol. beam – long. pol. target -ve target polar. →J. McAndrew (Wed II-A) W-dependence at constantcos θ +ve target polar.

  22. π-photoproduction γn→π-pbeam asymmetry & double pol. observables (40cm LD2 target) using HDice target in 2011/12 expected data (ΔW=15MeV) preliminary MAID07 SAID FA06 preliminary γn→π-pdata needed to separate isoscalar & isovector coupling of photon field (PhD Daria Sokhan, U.Edinburgh)

  23. η photoproduction helicity asymmetry E beam asymmetry (g8b, P.Collins, ASU) → Talk by B. Morrison (Thu III-C)

  24. K+Λ photoproduction g11: W=1.7 – 2.8 GeV (unpolarized beam & target) recoil polarization P excitation function PRC 81, 025201 (2010)

  25. γpK+Λ circ.pol.Beam-Recoil Cx and Cz • refit of Bonn-Gachina • model (Nikanov) • mix includes: • S11 wave, P13(1720), • P13(1900), P11(1840) • promotes this ‘missing’ res. • from ** to **** status • K+Σ0dσ/dΩ also better • described with P13(1900) • P13(1900) is found in • (qqq) quark models, • but not in quark-diquark • models PRC 75, 035205 (2007)

  26. Beam asymmetry in K+Λ, K+Σ0photoproduction γp→K+Λ (beam asymmetry) γp→K+Σ0 (beam asymmetry) preliminary • good agreement with GRAAL & LEPS data • larger energy and angular coverage (PhD Craig Paterson, U.Glasgow)

  27. γpK+Λ lin.pol.Beam-Recoil Ox and Oz +1 0 -1 cos q KaonMAID; RPR2-Regge only; RPR2-core; RPR2-w/D13 (PhD C.Paterson, U.Glasgow)

  28. γpK+Λ helicity asymmetry E (PhD L. Casey, CUA) preliminary

  29. γpK+Λ helicity asymmetry E (PhD L. Casey, CUA) preliminary

  30. γpK+Λ Polarization transfer Lx, Lz (PhD L. Casey, CUA) very preliminary • additional studies for Polarization transfer observables underway • extraction of helicity asymmetry E forK+Σ0started • analysis of data with transversely polarized target soon starting

  31. Summary and Outlook • Photoproduction of pseudoscalar mesons: • earlier runs for cross section (and Λrecoil asymmetry) measurements • for last 6 years only runs with polarized photons (circ., linear) • recently all photon experiments with • polarized photons and polarized targets • lots of cross section data recently published • beam asymmetry data will be published shortly • analysis of beam-target (and target-recoil) asymmetries underway • double-polarization data from neutron (deuterium) target are being taken in 2011/12 • complete set of measurements for KΛ(and KΣ) and • almost complete sets for πN, ηp

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