One of the foundational cornerstones of the physics program in Hall B with CLAS is the N* program. πn, ωn, φn, ρn, ηn, η N, ππn KΛ, KΣ, K Y, KY

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2 Introduction One of the foundational cornerstones of the physics program in Hall B with CLAS is the N* program. CLAS was designed to measure N and *N cross sections and spin observables over a broad kinematic range via measurement of exclusive reaction channels. πn, ωn, φn, ρn, ηn, η N, ππn KΛ, KΣ, K Y, KY probe relevant degrees of freedom vs. distance scale study non perturbative strong interactions in QCD The constituent quark model predicts a spectrum of states, many of which have not been seen experimentally. N* studies dominated by pionic channels KY channels important contributors in resonance region Coupling to strange final states complementary probe Part of larger international / multi lab effort: ELSA/Crystal Barrel SPring 8/LEPS Grenoble/GRAAL Mainz/MAMI g KYN vs. g NN Daniel S. Carman, Jefferson Laboratory N*211 Workshop May 17 2, 211 2

3 Model Status / Issues Coupled channel models developed by several groups... Giessen, Saclay/Pitt/ANL, KVI, Bonn Julich Fits include CLAS photoproduction data, but electroproduction data has not been included as of yet. Issues (more later) Tree level isobar models currently provide the best possibility to study both reactions in the same framework. "Simple", identify dominant trends Issues Lack of predictive power large number of free parameters Lack of systematic procedure to select resonance set Issues with introducing hadronic FFs to limit Born strength Contributions of "effective" u channel resonances interplay with FFs Gauge invariance restoration procedures Coupling constants: SU(3) values, broken symmetry,... Inclusion of higher spin resonances Channel coupling Final state interactions / rescattering effects Multiple valid fit solutions Daniel S. Carman, Jefferson Laboratory N*211 Workshop May 17 2, 211 3

4 Differential Cross Sections two track three track [McCraken et al., PRC 81, 2521 (21)] W : GeV Daniel S. Carman, Jefferson Laboratory N*211 Workshop May 17 2, 211 4

5 Differential Cross Sections two track three track [Dey et al., PRC 82, 2522 (21)] W : GeV Daniel S. Carman, Jefferson Laboratory N*211 Workshop May 17 2, 211 5

6 Recoil Polarization P P CLAS (29) CLAS (24) SAPHIR (24) GRAAL (27) CLAS (29) CLAS (24) SAPHIR (24) GRAAL (27) [McCracken et al., PRC 81, 2521 (21)] [Dey et al., PRC 82, 2522 (21)] Daniel S. Carman, Jefferson Laboratory N*211 Workshop May 17 2, 211 6

7 Transferred Polarization C x C z [Bradford et al., PRC 75, 3525 (27)] Daniel S. Carman, Jefferson Laboratory N*211 Workshop May 17 2, 211 7

8 CLAS N KY Program Photon Beam Target Recoil Target Recoil x y z x x x y y y z z z x y z x y z x y z x y z unpolarized linearly P o T P T L T x H P G O x T O z L z C z T z E F L x C x T x L x z z circular P F E C x C z O z G H O x p Circularly polarized photons/unpolarized target: n Polarized beam / longitudinally polarized target: Linearly polarized photons/unpolarized target: Polarized beam/longitudinal transverse target: Polarized beam/longitudinal tranvserse target: (last CLAS experiment in 6 GeV era) Daniel S. Carman, Jefferson Laboratory N*211 Workshop May 17 2, 211 8

9 Electroproduction Data At present there has been very limited use of the CLAS electroproduction data. U. Ghent isobar model / Regge plus resonance (RPR) model Mart multipole/isobar model Electroproduction data a richer source of information concerning N* coupling to KY final states. Involves N* coupling to both longitudinal and transverse photons 2 Access to NN* transition helicity amplitudes (electrocouplings) vs. Q Sensitively depends on EM form factors Very useful for constraining background from t channel exchanges Supplementary/complementary information on N* couplings relative to p Suggested approach (Ghent, Mart): Leading class of diagrams is assumed to be identical for p and *p Fix coupling constants to values from photoproduction fits Use parameterizations of EM FFs Partially fix parameters and then refit with p and *p data Daniel S. Carman, Jefferson Laboratory N*211 Workshop May 17 2, 211 9

10 Electroproduction Cross Sections U (nb/sr) cos K *=-.6 cos K *=-.25 cos K *=.5 cos K *=.35 cos K *=.65 cos K *=.9 Data 3 K + Data 3 K + K + K + K + K + TT (nb/sr) LT (nb/sr) -5-1 Janssen - B Mart/Bennhold Guidal [Ambrozewicz et al., PRC 75, 4523 (27)] dσ dω = σ U + ɛσ TT cos 2Φ + ɛ(ɛ +1)σ LT cos Φ E = GeV E = 4.56 GeV 2 2 W: GeV, Q =.65, 1. GeV W= GeV, Q = 1., 1.55, 2.5, 2.55 GeV 2 2 Daniel S. Carman, Jefferson Laboratory N*211 Workshop May 17 2, 211 1

11 Electroproduction Cross Sections 15 cos K *=-.6 cos K *=-.25 cos K *=.5 cos K *=.35 cos K *=.65 cos K *=.9 K + K + K + K + K + K + U (nb/sr) 1 5 TT (nb/sr) LT (nb/sr) -5 Janssen - B Mart/Bennhold Guidal [Ambrozewicz et al., PRC 75, 4523 (27)] dσ E = GeV 2 2 W: GeV, Q =.65, 1. GeV dω = σ U + ɛσ TT cos 2Φ + ɛ(ɛ +1)σ LT cos Φ E = 4.56 GeV 2 W= GeV, Q = 1., 1.55, 2.5, 2.55 GeV 2 Daniel S. Carman, Jefferson Laboratory N*211 Workshop May 17 2,

12 Model Predictions [Corthals et al., PLB 656, 185 (27)] Daniel S. Carman, Jefferson Laboratory N*211 Workshop ïï May 17ï2, 211 ïï 12

13 Structure Function Fits K + Λ K + Σ [Mart, EPJ Web Conf. 3, 72 (21)] KAON Maid New fits Daniel S. Carman, Jefferson Laboratory N*211 Workshop May 17 2,

14 Fifth Structure Function ep e K + Λ LT (nb/sr) cos K * =-.6 cos K * =-.25 cos K * =.5 * * * cos K =.35 cos K =.65 cos K =.9 Ghent RPR w P A LT = 1 P e N + N N + + N σ LT sin Φ = σ A LT ɛ(1 ɛ) E = GeV, Q =.65, 1. GeV Mart/Bennhold GLV Regge Ghent RPR w D 13 Data not included in fits. [Nasseripour et al., PRC 77, 6528 (28)] Daniel S. Carman, Jefferson Laboratory N*211 Workshop May 17 2,

15 Transferred Polarization ep e K + Λ 1. <W>=1.75 GeV <W>=1.99 GeV <W>=2.31 GeV <Q 2 >=2.61 GeV 2 <Q 2 >=2.56 GeV 2 <Q 2 >=2.41 GeV GeV 2 Summed over Q, P x P z Sensitive to model N* ingredients. Rule out P 11 (19) assignment. Data not included in fits. Mart/Bennhold GLV Regge Ghent RPR w P Ghent RPR w D c.m. cos K -1 1 c.m. cos K -1 1 c.m. cos K RPR: background + S 11(165), P 11(171), P (172), P (19) [Carman et al., PRC 79, 6525 (29)] Daniel S. Carman, Jefferson Laboratory N*211 Workshop May 17 2,

16 N* K +?? Historical Lore: Core set of states: S 11(165), P 11 (171), P 13 (172) Recent emergence of: P (19) 13 (from photoproduction fits) Coupled Channel Model (Bonn): [PLB 662, 245 (28)] Most relevant: S 11 wave, P 13 (172), P 13 (19), P 11 (184) Other required states: D (1675), P (171), D (1875), F (2), D (217), P (22) Coupled Channel Model (Saclay/Pitt/ANL): Most relevant: 11 Other required states: S (1535), D (152), P (19) [PRC 73, 5524 (26)] S (165), F (168), S (186), D (1954), F (2) Multipole Model (Mart): SAPHIR/LEPS: CLAS/LEPS: 15 S (165), F (168), D (17), P (172), F (2), D (28) D (1675), F (168), P (19), F (199), D (28) [EPJ A33, 243 (27)] Daniel S. Carman, Jefferson Laboratory N*211 Workshop May 17 2,

17 Theory Issues / Ambiguities Need to reduce ambiguities and improve fits with "all" available data. Include electroproduction data in fits Apparent normalization issue with SAPHIR K + data Internal consistency within multiple CLAS analyses of different data sets See Bydzovksy and Mart, PRC 76, 6522 (27) Extraction of resonance coupling depends on approach to model background. CLAS electroproduction shown to constrain background parameters Regge parameterization does a respectable job for K, poor for K + + Complications when fitting K data inclusion of N* and * states. There is little doubt that a combined fit multi channel approach is ultimately the best path forward. N N N, N, N, KY, N, N *N Daniel S. Carman, Jefferson Laboratory N*211 Workshop May 17 2,

18 Electroproduction Data Outlook Experimental data future: Analysis of Lambda recoil polarization from largest CLAS ep dataset in progress see M. Gabrielyan talk parallel session IIIb Opportunity to extract LT from dataset ~1x larger than published data Possible program of running electron beam with HD Ice target CLAS12 baryon spectroscopy program 2 2 opportunity to probe dynamics to Q up to ~8 1 GeV Planned fits of both photo and electroproduction data: EBAC coupled channel fits planned for (H. Lee "manpower permitting") RPR fits discussed as future work (J. Ryckebusch U. Ghent) Isobar model fits from O. Maxwell FIU [PRC 8, 6525 (29)] (fits in progress) Daniel S. Carman, Jefferson Laboratory N*211 Workshop May 17 2,

19 Summary/ Conclusions The CLAS strangeness physics program: Designed to measure cross sections and all combinations of beam, target, and recoil polarization states. * * CLAS data dominates the world s strangeness physics database for both photo and electroproduction cross section and spin observables. * * Precision data broad kinematic coverage Program includes "complete" experiments on both proton and neutron targets Main points from this talk: Progress in developing more sophisticated coupled channels models. Issues with inconsistent results from different fits Initial focus on photoproduction data; electroproduction data not used yet Electroproduction have been shown to provide important constraints: * non resonant backgrounds * longitudinal response * form factor evolution * N* electrocouplings Electroproduction data will be important to unravel the dominant N* KY decays. Daniel S. Carman, Jefferson Laboratory N*211 Workshop May 17 2,