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

photoproduction cross section

N*  Baryon spectrum PDG listing

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 πN reactions Capstick - Roberts

SAPHIR data (1998) triggered discussion on “missing” D 13 (1960): Mart-Bennhold: evidence for D 13 (1890) Saghai: bump in s due to u-channel and off-shell effects Q.Zhao: no need for D 13 (~1900) Janssen: s-p wave interference (P 11 (1840)) SAID: no need for D 13 (~1900) Penner-Mosel: evidence for D 13 (1900) Waluyo-Bennhold: strong evidence for D 13 (1950) Sarantsev-Klempt: evidence for radial excitation of D 13 (1520) at 1950 MeV lack of constraining data γN→KΛ Model comparison note: ~20% normalization offset Mart: refit with multipole model: P 13 (1900) Torres-Meissner: KKN bound state Nikanov: refit of Bonn-Gatchina model: P 13 (1900) new dσ/dΩ data: e.g. CLAS (PRC 81 (2010)): broader energy range, good agreement with previous CLAS data new polarization data: e.g. CLAS, CBELSA, GRAAL

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

Circularly and plane polarized photons on (a) long. and transv. polarized butanol target: CLAS: γp→π 0 p, π + n, ηp, γp→π + π - p, K + Λ, K + Σ 0 CBELSA: γp→π 0 p, ηp, γp→π 0 π 0 p γp→π 0 p, ηp, γn→π 0 n, ηn (b) long. polarized HD target: CLAS: γn→π - p, γn→π + π - n, γn→K 0 Λ, K 0 Σ 0, K + Σ - Frozen-spin target programs: 13 polar. observ. for K 0 Λ, 4-5 polar. observ. for K 0 Σ 0, K + Σ - 3 (7) polar. observ. for π - p all 15 polar. observ. for K + Λ, K + Σ 0 7 polar. observ. for π 0 p, π + n, ηp 7 polar. observ. for π 0 p, ηp 9 polar. observ. for π 0 N, ηN talk by F. Klein (Friday) → talk by F. Klein (Friday) talk by H.J. Arends (Friday) → talk by H.J. Arends (Friday)

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

polarized cross section (0 - photoproduction): α=orientation of photon polarization β=orientation of target polarization P T =linear photon polarization P o =circular photon polarization P z =longitudinal target polarization P xy =transverse target polarization Extraction of spin observables via Fourier analysis of polarized cross section in each (E,cos θ ) bin Extraction of polarization observables

sample PWA using MC data generated from SM02 greatly reduced uncertainties γp→π 0 p, π + n (sample PWA)

γp→π 0 p, π + n Impact on Single Energy Solutions

Torus magnet 6 superconducting coils Gas Cherenkov counters e/  separation, 256 PMTs Time-of-flight counters plastic scintillators, 684 photomultipliers Drift chambers argon/CO 2 gas, 35,000 cells polarized target + polarized target + start counter start counter Electromagnetic calorimeters Lead/scintillator, 1296 photomultipliers DAQ limit ~10kHz (~2.5TB/day) C EBAF L arge A cceptance S pectrometer

Hall-B photon tagger Jefferson Lab Hall-B photon tagger: Eγ = 20-95% of E 0 Eγ up to ~6 GeV dE/E ~10 -3 of E 0 Circularly polarized beam produced by longitudinally polarized electrons (P e >85%) Linearly polarized photons: coherent bremsstrahlung on oriented diamond crystal Circular polarization linear polarization

Frozen-spin butanol target e.g. FROST design g9a (2008/9) g9b (2010) polarization:±85%+82%+85% -85%-93% relaxation time:500 h2700 h (+)3500 h (+) 1400 h (-)1900 h (-) (~5%/day)(<1.5%/day)(<1%/day) base temp:50 mK30 mK25 mK Ch. Bradtke, PhD Bonn

longitudinal polarization: solenoidal coil (0.55T; ΔB/B~0.2%) → online NMR transverse polarization: “racetrack” coil (0.45T; ΔB/B~0.4%) NEW DEVELOPMENT! size: Ø5cmx11cm size: Ø5cmx20cm max. Pol.~96%, average ~82-85% (τ relax ~90d) CLAS frozen-spin target (FROST) operate at 35mK

target: Ø15mm x 50mm 3g of solid H-D composite density: g/cm cooling wires (Al) Ø50  m P V (D)~40%, P(H)~40% or P V (D)~0%, P(H)~75% Polarize at 15T &12 mK and operate at 1T & 250mK 1/e relaxation time: τ 1 ~1.5 years additional “empty cell” downstream: subtraction of Al background HDice at CLAS LEGS

HD target polarize with B=15T at 12mK for 2 months operate with B=1T at 250mK tensor polarization (~12%): Resolve contributions from P T (D) by flipping D spin and data on polarized H

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

quasi-free reactions fermi motion (missing momentum cut) coplanarity cut to suppress rescattering comparison of free proton/bound proton data from pol. H and pol. D comparison of free proton/bound proton data from pol. H and pol. D (assuming that free/bound neutrons behave similarly) (assuming that free/bound neutrons behave similarly) Extraction of free neutron amplitudes

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

π 0 photoproduction data: CB-ELSA (open), CLAS (filled) curves: SAID SM02(dash-dotted), FA06(solid) γp→π 0 p (M. Dugger et al., PRC 76, (2007)) first row: SAID sec.row: PDG No “new” resonances needed! Strong excitation of P 13 (1720) consistent with analysis of pπ + π - electro-couplings

π 0 p photoproduction beam asymmetry Σ for γp→π 0 p (g8b, analysis ASU)

helicity asymmetry γp→π 0 p π 0 beam-target asymmetries CLAS –g9a GDH Mainz → Talk by H. Iwamoto (Wed. II-A) preliminary data for E γ = GeV preliminary data for E γ = GeV models consistent with data at E γ < 1.35 GeV models consistent with data at E γ < 1.35 GeV

beam – target asymmetry G beam – target asymmetry G for γp→π 0 p (CBELSA) → Talk by Jan Hartmann (Wed. II-A) π 0 beam-target asymmetries

π + photoproduction beam asymmetry Σ for γp→π + n (CLAS g8b, analysis ASU)  large energy and angular coverage  good agreement with previous data

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

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

π - photoproduction MAID07 SAID FA06 γn→π - p beam asymmetry & double pol. observables (40cm LD 2 target) using HDice target in 2011/12 (40cm LD 2 target) using HDice target in 2011/12 γn→π - p γn→π - p data needed to separate isoscalar & isovector coupling of photon field expected data (ΔW=15MeV) (PhD Daria Sokhan, U.Edinburgh)

η photoproduction γp→ηp (g11, analysis CMU: PRC 80, (2009)) excitation function for cos θ* bins

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

Single-bump: resonance-like structure near 1.9 GeV ( N* & D resonances) new data: g11 analysis PRC 82, (2010) K + Σ 0 photoproduction

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

refit of Bonn-Gachina model (Nikanov) mix includes: S11 wave, P13(1720), P13(1900), P11(1840) promotes this ‘missing’ res. from ** to **** status K + Σ 0 dσ/dΩ also better described with P13(1900) P13(1900) is found in (qqq) quark models, but not in quark-diquark models γp  K + Λ circ.pol.Beam-Recoil C x and C z PRC 75, (2007)

Beam asymmetry in K + Λ, K + Σ 0 photoproduction γp→K + Λ (beam asymmetry) γp→K + Σ 0 (beam asymmetry)  good agreement with GRAAL & LEPS data  larger energy and angular coverage (PhD Craig Paterson, U.Glasgow)

γp  K + Λ lin.pol.Beam-Recoil O x and O z (PhD C.Paterson, U.Glasgow) KaonMAID; RPR2-Regge only; RPR2-core; RPR2-w/D cos 

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

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

γp  K + Λ Polarization transfer L x, L z (PhD L. Casey, CUA) additional studies for Polarization transfer observables underway K + Σ 0 extraction of helicity asymmetry E for K + Σ 0 started analysis of data with transversely polarized target soon starting

Summary and Outlook  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 Λ  complete set of measurements for K Λ (and K Σ ) and πN, ηp  almost complete sets for πN, ηp Photoproduction of pseudoscalar mesons: Λ earlier runs for cross section (and Λ recoil asymmetry) measurements for last 6 years only runs with polarized photons (circ., linear) recently all photon experiments with polarized photons and polarized targets

π + beam-target asymmetry G

Experiment cross section, spin observables Theory LQCD, quark models, QCD sum rules, … Reaction Theory dynamical frameworks Amplitude analysis →multipole ampl., →phase shifts σ,dσ/dΩ (single) Σ,P,T (beam-target) E, F, G, H, (beam-recoil) C x,C z, O x,O z, (target-recoil) L x,L z, T x,T z, PWA: energy- independent fits Coupled Channels: resonance parameter extraction from Experiment to Theory

theoretical analysis (EBAC) T(E)=T scat (E) + T int (E) G NB =propagator with dynam. generated width coupled channel equations V=meson-exchange pot., Z(E)=one-particle exchange term (incl. unitarity cuts) Excited Baryon Analysis Center