N*s as determined from exclusive reactionsVolker D. Burkert Outline: Goals of the N* Program Large Acceptance Detectors N* related data from JLab Status of the N* Analysis Upcoming experiments at Jlab @ 6 GeV Tools for more complex analyses Penta-Quarks and N*s ConclusionsPAC25 - Mini Workshop on Nucleon Excited States, January 17, 2004, Kingsmill Resort

Goals of the N* Program Two main motivations for the N* program:

The study of the nucleon wave function though measurement of e.m. transition form factors for known resonances, e.g. D(1232), P11(1440), S11(1520), D13(1520), F15(1680), ... => analyze Np, Nh, (Npp) final states

The study of the underlying symmetry properties through the search for SU(6)xO(3) symmetry predicted, yet undiscovered resonances (missing resonance problem), in measurements of Np, Npp, K+L, K+S, pw, Nr, .. final states.

Large Acceptance Detectors for N* Physics. CLAS: (photon and electron reactions) Measure many final states with mostly charged particles simultaneously. Operate with high luminosity electron beams, and with unpolarized and polarized energy-tagged bremsstrahlung photon beams. Coverage for photons limited to lab angles < 45o Crystal Barrel-ELSA: (photon reactions) CsI with excellent photon detection, e.g. Npopo , NpohSAPHIR-ELSA (photon reactions, detector dismantled) Charged particles in final stateGRAAL (photon reactions): BGO crystals, with excellent photon detection, limited charged particle, polarized laser-backscattered tagged photon Crystal Ball MAMI (photon reactions)neutral final states in limited W range BES (Beijing) N* in e+e- collisions.LEPS SPring-8 (photon reactions) Charged particle detection in forward dipole spectrometer, and TPC with large angle coverage.

Status of N*- exclusive meson productionExperimentReactionPhysicsData Analysis Publication StatusStatusStatus

E89-037ep eppoREM, RSMcompl.ongoing PRL88, 122001 (2002)ep enp+REM, RSMcompl.ongoingin preparation E89-038ep enp+gpN*compl.ongoingin preparation eD epp-gnN*compl.------ E89-039ep ephgNS11compl.ongoingPRL86, 1702 (2001)E89-042ep epposLT NDcompl.ongoingPRC68, 032201 (2003)ep enp+sLT ND compl.ongoingin CLAS reviewE01-102ep epposLT NN*compl.ongoing---E01-103ep enp+sLT NN*compl.ongoing---E91-002ep eppoREM high Q2compl.ongoingin preparationE99-107ep eppo REM high Q2compl.ongoing---E91-024ep epwmiss. N*compl.ongoing---E93-006ep epp+p-miss. Res.compl.ongoingPRL91, 022002 (2003)E99-108ep epp+p-miss. Res.compl.started---E93-036ep eppoAet, Atcompl.ongoingPRC68, 035202 (2003)ep ep+nAetcompl.compl.PRL88, 82001 (2002)E93-030ep eK+LN*, miss N*compl.ongoingPRL90, 131804 (2203)E94-005ep epp+p-Axial ffcompl.ongoing---E91-023ep eX Aetcompl.ongoingPRL91, 222002 (2003)

Status of N*- exclusive meson productionExperimentReactionPhysicsData Analysis Publication StatusStatusStatus

E00-112ep eK+Lmiss. N*compl.ongoing PRL90, 131804 E91-011ep epp0REM,RSMcompl.ongoingin preparationE93-050ep epg(p0)N* compl.compl.nucl-ex/0308009

E94-014ep epp0ND(1232)compl.compl.PRL82:45 (1999)ep ephS11(1535)compl.compl.PRD60:052004 (1999)

Status of N*- exclusive meson production

Status of N*- exclusive meson production---gd K+K-p(n)5-quark B5---ongoingPRL91, 252001(2003)E03-xxxsched---------gp K+K-p+(n)5-quark B5---ongoingPRL92, 01 (2004)E04-xxx KonK+, ..Excited Q+ sched.------E04-xxxed p-p-p-pSearch for X--tbd------E04-xxxep manyQ+, X-- tbd------

Kinematics ep epX, E=4GeV

Data published after 1998 ND(1232) Transition

ND(1232) current program

pp0 with high statistics are currently being analyzed covering Q2 = 0.1 6.0 GeV2

ep ep+n channel for Q2 = 0.1 6.0 GeV2

Data on sLT for ppo, np+ in D(1232) region at Q2 < 4 GeV2

Data on At , Aet for ppo, np+, pp- at Q2 < 4 GeV2

Single and double polarization resp. functions at Q2 = 1 GeV2

Cross section for pp0 at backward p0 angles at Q2 = 1 GeV2

pp0 with high statistics taken at Q2 = 6.0 & 7.5 GeV2 (data in hand, partially analyzed)

Response Functions from p0 Electroproduction in the D(1232) Regionds/dW = sT + esL + esTTcos2f+ 2e(e+1)sLTcosf;si(cosq*,W)CLASPreliminary

N* program ND(1232) transitionfQ2=3GeV2C L A S p r e l i m i n a r y

ND(1232) TransitionCLAS preliminary

s = so[1 + Psp + h(A + Psp)] so = no(nLRL + nTRT - nLTRLTcos fpq + nTTRTTcos 2fpq) Aso = no(-nLTRLT sin fpq) Pnso = no(nLRnL + nTRnT - nLTRnLTcos fpq + nTTRnTTcos 2fpq) Pl,tso = no(-nLTRl,tLTsin fpq + nTTRl,tTTsin 2fpq) Pnso = no(-nLTRnLTsin fpq) Pl,t so = no(-nLTRl,tLTcos fpq + nTTRl,tTT)Polarization Observables

Response Functions Hall A

CLAS ND(1232) Asymmetries

ND(1232) Transition Published + publicly presented data.

ND(1232) Transition With current data from CLAS, Hall A & Hall C, JLab data on REM, RSM, and GMD will cover the range Q2 = 0.1 7.5 GeV2 with excellent statistics and low systematics. Results projected from completed experiments. Hall A data include recoil and double polarization responses. CLAS data include pp0, np+,beam asymmetries Ae, beam/target asymmetries At, Aet

Analysis Tools for Meson Production above the D(1232) Unitary Isobar Model (JLab-Yerevan) for single p, h production Born terms + w, r exchange Resonances as relativistic Breit-Wigner Regge exchange at high W

Fixed- t Dispersion Relations (JLab-Yerevan) Imaginary part of amplitude as sum of Resonances Real part by dispersion relations High energy behavior by Regge parametrization

Isobar Model for two-pion analysis (JLab-Moscow-Genova) Non-resonant 3-body p.s., diffractive Nr, Dp, D13p, Reggeon exchange at high W, s-channel Breit-Wigner resonances

Event-based Partial-Wave Analysis with Maximum-Likelihood fits for Npp final state (RPI-JLab)

Second Nucleon Resonance RegionResonances: P11(1440), S11(1535), D13(1520)

Structure of the Roper P11 ? |Q3> quark state? |Q3G> state? |Ns> molecule? |Q4Q> penta-quark? quark core with meson cloud Structure of the S11(1535) hard transition form factor? a 3-quark resonance? a KS molecule?

Q2 evolution of the D13 helicity structure, A3/2 A1/2 dominance.

Second Nucleon Resonance Region Single pion and eta production1) ep e(np+, ppo), Q2 = 0.1 5.0 GeV2E89-038,42 E1-62) ed epp-(p)Q2 = 0.1 3.5 GeV2E89-038/423) ep eph Q2 = 0.1 5.0 GeV2E89-039 4) ep eppo Q2 = 0.1 3.5 GeV2E93-0365) ep ep+n Q2 = 0.1 3.5 GeV2E93-036

Global analysis using DR (JLab-Yerevan) and UIM (JLab-Yerevan) fits performed for 1) - 3) at low Q2 .

First analysis of a consistent set of p0, p+, h cross sections and polarized beam structure functions.

The 2nd Resonance Regionep enp+CLASUnitary Isobar fit

Fit to p, h ElectroproductionW = 1.23 GeV,W = 1.53 GeVp+sT+esL, sTT, sLTQ2=0.4 GeV2

Fit to p, h ElectroproductionW = 1.18 1.58 GeVW = 1.18 - 1.58 GeVpop+sLT (S)

Global Fit to h PhotoproductionW > 1.49 GeVW > 1.49 GeVhhsT, S

Global Fit to h PhotoproductionTarget asymmetry

Global Fit to h Photoproductionstot

First Results from JLab Global AnalysisZero crossing?

First Results from JLab Global Analysis

First Results from JLab Global Analysis contd

D13(1520)First Results from JLab Global Analysis contd

Resonances: S31(1620), S11(1650), D13(1700), D15(1675), F15(1680), P11(1710), P13(1720), D33(1700), ..

Transition form factors in a large Q2 range- test of the Single Quark Transition Model (SQTM) for g + [56,0+] [70,1-], and g + [56,0+] [56,2+] transitions

Does the P11(1710) have a 5-quark component as required by the chiral soliton model of Diakonov et al.? cSM predicted the Q+(1540) as a 5-quark state. Main tools to study transitions in 3rd resonance region g*N Np g*N Npp, many states couple strongly to NppThird Nucleon Resonance Region

Test of the Single Quark Transition Model

Test of the Single Quark Transition Model

Tools to search for Missing Resonances Search for new baryon states (N*, D) in Npp Developed Isobar Model for the analysis of pp+p- photo- and electro-production data (Moscow-JLab-Genova). Developing IM including neutral channel, e.g. np+po, ppopo. Developed event-based PWA approach for the analysis of pp+p- photo-production data.

Search for new baryon states (N*, D) in KY. Appropriate tools for resonance analysis are currently lacking. Coupled-channel analysis essential because of large background.

Search for new baryon states (N*) in pw. Dynamical Model developed by Y. Oh. We are adopting this model to fit experimental data in single channel analysis. Need to include other channels because of background.

Partial Wave Formalism for gp pp+p-Tfi =

= S

= Sya(tf)Va(E)aa Transition matrix: Decay amplitude ya(tf) calculated using isobar model: e.g. JP, M = +, + [D++p-]l=1, lPf = + Production amplitude Va(E) is fitted in unbinned maximum likelihood procedure. Assume Va(E) is independent of E in small energy range. =p+pp-++ . . .

JPMIsobars

1/2+ 1/2Dp (={D++p-, Dop+})

1/2- 1/2Dp, (pr)(s=1/2

3/2+1/2, 3/2(Dp)(l=1) ,(pr)(s=1/2) ,(pr)(s=3/2;l=1,3) ,N*(1440)p

3/2- 1/2, 3/2 (Dp) (l=0,2)

5/2+1/2, 3/2(Dp)(l=1), ps

5/2-1/2, 3/2(Dp)(l=2) Total of 35 waves (complex amplitudes) Diffractive production (t-channel) also includedWaves in the current analysis

Samples of event-based PWA for gp pp+p-P33(1600)?A new P33?F15(1680)?

Isobar Model for the g*N Npp channel All established resonances included as Breit-Wigners

Non-resonant Born terms for all D(1232)p isospin channels, and for D13(1520)p channels.

Non-resonant pro production through diffractive ansatz.

High mass behavior through Reggeon exchange.

Good fits to one-dimensional cross sections at low pp+p- masses.

Isobar Model for the g*N Npp channel

W=1.71GeV Q2=0.95 GeV2W=1.71 GeV Q2=1.30 GeV2Isobar Model for the g*N Npp channel

Resonances in g*p pp+p-missing resonance strength?Genova-MoscowIsobar model fitGNpp PDGGNg AO/SQTM (with amplitudesadjusted)Total cross sectionCLAS

Isobar fit to D13(1700) and new PI3PI3D13(1700)W(GeV)Isobar model fitGNpp PDGGNg AO/SQTMTotal cross sectionCLAS

Isobar fit - A new PI3 state?PI3qp- (deg)Mp+p-Mp+p Data described best by new PI3 0.8 - 0.91650-1750100-200~ 0 known P13 consistent with missingP13 state, but mass lowW = 1.74GeVCLASD13(1700)M = 1.72 +/- 0.02 GeVGT = 114 +/- 19 MeV Dp : 0. 63+/- 0.12 Nr : 0.19 +/- 0.09

Strangeness PhotoproductionDominant resonancesS11(1650)P11(1710)P13(1720)D13(1895) ?Carnegie MellonSimilar data setsexist from SAPHIR.

Strangeness Photoproduction Data indicate significantresonance contributions,interfering with each other and with non-resonantamplitudes.

Extraction of resonance parameters requires a large effort in partial wave analysis and reaction theory. Sample of data covering the full kinematic range in energy and angles for K+L and K+S, including recoil polarization

Strangeness in electroproduction ep eK+Y response functionsCLAS

preliminaryStrangeness in electroproduction g*p K+L CLASbackward hemishereforward hemispherenew N*?knownN*

CLAS - Resonances in gp pw?Model: Y. OhPRELIMINARY

cosqpw+1-1sabove resonanceregioninresonanceregionw - electroproduction CLAS

Penta-Quark Baryons They are part of the baryon spectrum

Some (most?) will mix with ordinary baryons, so they have to be analyzed together with the other excited states.

They may be produced via the decay of excited N*s.

They will help us to understand the symmetries underlying the baryon spectrum

They provide fundamentally new insight into how QCD works in the complex regime where the interaction is strong

CLAS - Q+ Production on Protons V. Kubarovsky, et al.; PRL submitted

M(p,K0,K-), if 1.525 M(p,K0)

What is needed for a full success of the N* program?

More data on polarization observables linearly polarized photons transverse/longitudinally polarized hydrogen and deuterium targets

Full coupled channel analysis including allfinal states, in all isospin channels

Excited Baryon Analysis Center Conclusions