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Studies of N* Structure from the CLAS Meson Electroproduction Data

Studies of N* Structure from the CLAS Meson Electroproduction Data. M. Ripani , INFN Genova. N,N* quark core. MENU 2013 Conference. Studies of the N*-Structure in Exclusive Meson Electroproduction. Our experimental program seeks to determine

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Studies of N* Structure from the CLAS Meson Electroproduction Data

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  1. Studies of N* Structure from the CLAS Meson Electroproduction Data M. Ripani, INFN Genova N,N* quark core MENU 2013 Conference

  2. Studies of the N*-Structure in Exclusive Meson Electroproduction • Our experimental program seeks to determine • gvNN* electrocouplingsat photon virtualitiesup to 5.0 GeV2 for most of the excited proton states through analyzing major meson electro-production channels independently and in global multi- channel analyses. • This information is needed to study the evolution of relevant degrees of freedom in N* structure with distance and to access the non-perturbative strong interaction which generates N* states as bound systems of quarks and gluons • (see I. G. Aznauryanet al., Int. J. Mod. Phys. E22, 133015 (2013)). • The non-perturbativestrong interaction represents the most important part of the Standard Model that we have yet to explore. • It is the only fundamental sector where relevant degrees of freedom accessible in the measurements can be very different with respect to those entered in the basic QCD Lagrangian.

  3. Extraction of gvNN* electrocouplings from the data on exclusive meson electroproductionoff protons Resonant amplitudes Non-resonant amplitudes p, h, pp,.. e’ p, h, pp,.. γv e * N*,△ + N’ N N’ N • A1/2(Q2), A3/2(Q2), S1/2(Q2) • or • G1(Q2), G2(Q2), G3(Q2) • or • GM(Q2), GE(Q2), GC(Q2) N*’s photo-/electrocouplingsgvNN* are defined at W=MN* through the N* electromagnetic decay width Gg: See details in: I.G.Aznauryan and V.D.Burkert, Progr. Part. Nucl. Phys. 67, 1 (2012). • Separation of resonant/non-resonant contributions within the framework of reaction models; Breit Wigner ansatz for parameterization of resonant amplitudes; fit of resonance electroexcitation and hadronic parameters to the data. • Consistent results on gvNN* electrocouplingsfrom different meson electroproductionchannels and different analysis approaches demonstrate reliable extraction of N* parameters.

  4. CEBAF Large Acceptance Spectrometer Torus magnet 6 superconducting coils Large angle calorimeters Lead/scintillator, 512 PMTs Liquid D2 (H2)target + g start counter; e minitorus Gas Cherenkov counters e/pi separation, 216 PMTs Drift chambers argon/CO2 gas, 35,000 cells Electromagnetic calorimeters Lead/scintillator, 1296 PMTs Time-of-flight counters plastic scintillators, 684 PMTs The unique combination of the CEBAF continuous electron beam and the CLAS detector makes Hall-B@JLAB the only facility operational worldwide, that is capable of measuring unpolarized cross sections and polarization asymmetries of most exclusive meson electroproduction channels with substantial contributions at W<3.0 GeV and Q2<5.0 GeV2. V.I.Mokeev, NSTAR 2013 Workshop Peniscola, Spain, May 27-30, 2013

  5. Summary of the CLAS Data on Exclusive Meson Electroproduction off Protons in N* Excitation Region • ds/dW-CM angular • distributions • Ab,At,Abt-longitudinal • beam, target, and • beam-target asym- • metries • P’ –recoil polarization • of strange baryon Almost full coverage of the final hadron phase space in pN, p+p-p, hp, and KY electroproduction The data are available in the CLAS Physics Data Base: http://depni.sinp.msu.ru/cgi-bin/jlab/db.cgi

  6. N* Electroexcitation in Exclusive Meson Electroproduction off Protons CLAS data on yields of meson electroproductionat Q2<4 GeV2 Hadronic decays of prominent N*s at W<1.8 GeV.

  7. Approaches for Extraction of gvNN* Electrocouplings from the CLAS Exclusive Meson Electroproduction Data • Analyses of different meson electroproduction channels independently: • p+n and p0p channels: Unitary Isobar Model (UIM) and Fixed-t Dispersion Relations (DR) I.G.Aznauryan, Phys. Rev. C67, 015209 (2003). I.G.Aznauryan et al., CLAS Coll., Phys Rev. C80, 055203 (2009). • hp channel: Extension of UIM and DR I.G.Aznauryan, Phys. Rev. C68, 065204 (2003). Data fit at W<1.6 GeV, assuming S11(1535) dominance H.Denizli et al., CLAS Coll., Phys.Rev. C76, 015204 (2007). • p+p-p channel: Data driven JLAB-MSU meson-baryon model (JM) V.I.Mokeev, V.D.Burkert et al., Phys. Rev. C80, 045212 (2009). V.I.Mokeev et al., CLAS Coll., Phys. Rev. C86, 035203 (2012). • Global coupled-channel analyses of the CLAS/world data of pN, gvN→ pN, hN, ppN, KL, KS exclusive channels: N. Suzuki, T. Sato, T.-S.H.Lee, Phys.Rev. C82 (2010) 045206 H. Kamano, T.-S. H. Lee, AIP Conf.Proc. 1432 (2012) 74-79

  8. DR DR w/o P11 UIM Fits to gVp→p+n Differential Cross Sections and Structure Functions DR Q2=2.44 GeV2 UIM Q2=2.05 GeV2 ds/dWp Legendre moments Dl (l=0,1,2)from various structure functions

  9. The CLAS Data on p+p-p Differential Cross Sections and their Fitwithin the Framework of Meson-Baryon Reaction Model JM G.V.Fedotov et al, PRC 79 (2009), 015204 1.30<W<1.56 GeV; 0.2<Q2<0.6 GeV2 M.Ripani et al, PRL 91 (2003), 022002 1.40<W<2.30 GeV; 0.5<Q2<1.5 GeV2 p+F015(1680) full JM calc. p+D0 rp p-D++ 2p direct p+D013(1520)

  10. JM Model Analysis of the p+p-p Electroproduction Major objectives: extraction of gvNN* electrocouplings and pD, rp decay widths. g p- g p-/+ D++/0 (1232)P33, N0 (1520)D13, D++ (1600)P33, N0(1680)F15 p+ = p p p • six meson-baryon • channels and direct • p+p-p production. • N* contribute to pD • and rp channels only. • unitarizedBreit-Wigner • ansatz for resonant • amplitudes. p’ p’ g p- p-, p+, … g r p+ p+, p-, … + + p p’ p p’,p’, … • V.I.Mokeev, V.D. Burkert, et al., (CLAS Collaboration) Phys. Rev. C86, 035203 (2012). • V.I.Mokeev, V.D. Burkert , et al., Phys. Rev. C80, 045212 (2009). V.I.Mokeev, NSTAR 2013 Workshop Peniscola, Spain, May 27-30, 2013

  11. UnitarizedBreit-Wigner ansatz for resonant amplitudes • Developed based on approach: I.J.R.Aitchison, Nuclear Physics , A189 (1972), 417. Inverse of the JM unitarized N* propagator: N*a N*a diagonal Off-diagonal transitions incorporated into the full resonant amplitudes of the JM model: N*a N*b off-diagonal S11(1535) ↔ S11(1650) D13(1520) ↔ D13(1700) 3/2+(1720) ↔ P13(1700) Full resonant amplitude of unitarizedBreit-Wigner ansatz is consistent with restrictions imposed by a general unitarity condition, as well as with the resonant Argonne-Osaka ansatz in on-shell approximation.

  12. NΔ Transition Form Factors Magnetic Dipole Form Factor Quadrupole Ratios • CLAS • Hall A • Hall C • MAMI • Bates Meson- Baryon cloud pQCD: REM→ 1.0 pQCD: ~1/Q5 pQCD: RSM→ const bare quark core No evidences for pQCD onset at Q2<7 GeV2 • Successful description was achieved taking into account meson-baryon dressing and quark core The mechanisms of the meson-baryon dressing T. Sato and T-S. H. Lee, PRC 63, 055201 (2001). • Quark core was well described by the relativistic QM: B.Julia-Diaz et al., PRC 69, 035212 (2004).

  13. Quark vs Meson-Baryon Degrees of Freedom in N→D Form Factors G*M (Jones-Scadron) Q2/mr2 G1 and G2N→D f.f. from LF quark model: I.G.Aznauryan, V.D.Burkert, Phys. Rev. C85, 055202 (2012). Quark core contribution from DSEQCD: J.Segovia, et al., arXiv:1305.0292[nucl-th]. Contact interaction. Non-perturbative mass generation: quark core. meson-baryon cloud from Argonne-Osaka approach. dressed G1 and G2f.f. contact interaction. contact interaction & quark anomalous magn. moment. For the first time this quark model accounts for momentum dependenceof dressed quark mass. projection for quark running mass. bare G*M inferred from exp. data within Argonne-Osaka c.c. approach.

  14. The P11(1440) Structure from the CLAS Electrocoupling Data CLAS data: p+p-p 2012 Np 2009 p+p-p prelim. S1/2 Light Front quark models: I.G.Aznauryan, A1/2 PRC 76, 025212 (2007). S.Capstick and B.D.Keister, PRD 51, 3598 (1995). • Consistent values of P11(1440) electrocouplings • determined in independent analyses of Np and p+p-p • exclusive channels strongly support reliable • electrocoupling extraction. Meson-Baryon dressing: (absolute values) B,Julia-Diaz et al., PRC 77, 045205 (2008). • The physics analyses of these resultsrevealed the P11(1440) structure as a combined contribution of: a) quark core as a first radial excitation of the nucleon 3-quark ground state and b) meson-baryon dressing.

  15. Quark Core vs Meson-Baryon Cloud in the Structure of P11(1440) First evaluation of the quark core contribution to the P11(1440) electrocouplings starting from QCD Lagrangian within Dyson-Schwinger Equations of QCD: D.J.Wilson, et al, Phys. Rev. C85, 025205 (2012). • Poincare-covariant, symmetry preserving DSEQCD evaluation. • Account for quark mass/structure formation in dressing of bare quark by gluon cloud. • Simplified contact interaction generates momentum independent quark mass. A1/2 Consistent results on the quark core contribution from: DSEQCD. global meson photo-, electro-, and hadroproduction data analysis within EBAC/ Argonne-Osaka approach. • Measured dressed electrocouplings are substantially different from the estimated quark core contribution. Different data analyses suggest sizable meson-baryon cloud at Q2<5.0 GeV2 which gradually decreases with Q2 .

  16. gvNN* Electrocouplings of D13(1520) and S11(1535) Resonances D13(1520) A3/2 S11(1535) A1/2 D13(1520) A1/2 M.Giannini,E.Santopinto, PRC 86, 065202 (2012). S.Capstick, B..D.Keister , PRD 51, 3598 (1995). MB dressing abs. values (EBAC/Argonne-Osaka) hp CLAS, Hall-C • a good agreement between the results from Np, Nh and p+p-p exclusive channels. • access to the lowest orbital excitation of 3-q system and DCSB manifestation through • comparison of the ground and S11(1535) state structure (chiral partners). • contributions from inner quark core and external meson-baryon cloud, which depends • substantially on the resonance quantum numbers.

  17. High lying resonance electrocouplings from the p+p-p CLAS data analysis Δ(1700)D33 NpQ2=0, CLAS Npworld NppCLAS preliminary A1/2 BF(Npp): 80-90% V.D.Burkert, et al., PRC 67, 035204 (2003). M.Dugger, et al., PRC 79,065206 (2009). p+p-p electroproductionchannel provided first preliminary results on S31(1620), S11(1650), F15(1685), D33(1700) , and P13(1720) electrocouplingswith good accuracy. computed from the data on D13(1520) and S11(1535) electrocouplings within the framework of SQTM approach: I.G. Aznauryan and V.D. Burkert, Progr. Nucl. Part. Phys. 67, 1 (2012). A3/2 Single quark electromagnetic current and SU(6) spin-flavor symmetry play an important role in the structure and electroexcitationof D13(1520), S11(1535), and D33(1700) states.

  18. High lying resonance electrocouplings from the p+p-p CLAS data analysis MAID analysis of Npelectroproduction L.Tiator et al., Eur. Phys. J. Spec. Top. 198, 141 (2011). N (1685)F15 A1/2 BF(Np): 65-70% BF(Npp): 30-40% The results from p+p-p channel confirmed the previous MAID analysis of Npelectroproduction Hypercentral constituent quark model by M.M.Giannini, E.Santopinto, PRC 86, 065202 (2012). Bethe-Salpeter Bonn model by M.Ronninger, B.Ch.Metsch, EPJ A49, 8 (2013). A3/2 Difference between the experimental results and QM expectations is likely related to meson-baryon cloud contributions. Evaluations of meson-baryoncloud contributions to electrocouplings of high mass resonances are needed.

  19. High lying resonance electrocouplings from the p+p-p CLAS data analysis Hypercentral constituent quark model by M.Giannini,E.Santopinto, PRC 86, 065202 (2012). D(1620)S31 A1/2 Bethe-Salpeter Bonn model by M.Ronninger, B.Ch.Metsch, EPJ A49, 8 (2013). • Only known N*-state with dominant longitudinal • electroexcitation at Q2>0.5 GeV2. • This feature is well reproduced within • the framework of hypercentral quark model. • Data on electrocouplings of most excited proton states in mass range up to 1.8 GeVdemonstrated distinctive differences in the structure of resonances of different quantum numbers. • The studies of the ground and all prominent excited state structure combined are needed in order to explore the mechanisms of the ground and N*-state formation from quarks and gluons. S1/2

  20. Conclusions and Outlook • High quality meson electroproduction data from the CLAS detector allowed us to determine electrocouplings of P33(1232), P11(1440), D13(1520), and S11(1535) resonances from analyses of Np and Nh channels at Q2<5.0 GeV2 and Q2 <4.0 GeV2 , respectively, as well as from the p+p-pelectroproduction at Q2<1.5 GeV2. Consistent values of gvNN* electrocouplings from independent analyses of Np/Npp and Np/Nhchannels confirmed reliable extraction of these fundamental quantities. • Preliminary results on electrocouplings of S31(1620), S11(1650), F15(1680), D33(1700), and P13(1720) resonances were obtained from analysis of p+p-p electroproduction at 0.5<Q2 <1.5 GeV2 for the first time. • Analyses ofthe results on gvNN* electrocouplings revealed the N*-structure as internal core of three constituent quarks surrounded by external meson-baryon cloud. Resonances of different quantum numbers provided complementary information on the N* structure. The data on electrocouplings of all prominent N*-states are needed. • Electrocouplings of most N*-states in mass range up to 2.0 GeV will be determined in few years from independent analyses of Np and Nppelectroproduction at photon virtualities up to 5.0 GeV2.

  21. Conclusions and outlook • The dedicated experiment on N* studies with the CLAS12 detector at the largest photon virtualities ever achieved 5.0<Q2<12 GeV2is scheduled for the first year of running after completion of the Jefferson Lab 12 GeV Upgrade Project. • The N* program with the CLAS12 detector opens up the prospects to elucidate the emergence of >98 % of nucleon and N* masses from QCD.

  22. Back up

  23. CLAS12 Central Detector • CLAS12supports a broad program in hadronic physics. • Plans to study excited baryons and mesons: • Search for hybrid mesons and baryons • Spectroscopy of Ξ* , Ω- • N* Transition form • factors at high Q2. Forward Detector

  24. Resonance Transitions with the CLAS12 12 GeV experiment E12-09-003 will extend access to electrocouplings for all prominent N* states in the range up to Q2=12GeV2. Resonance electrocouplings in regime of quark core dominance can be related to the running quark masses and their dynamical structure. P11(1440) A1/2 Light front quark model: I.G.Aznauryan, V.D. Burkert, PRC85, 055202 (2012). LQCD DSE accessible at 6 GeV DSEQCD : contact inte- raction; realistic QCD interaction. quark mass (GeV) accessible at 12 GeV CLAS12projected Probe the transition from confinement to pQCD regimes, allowing us to explore how confinement in baryons emerge from QCD and how >98 % of baryon masses are generated non-perturbatively via dynamical chiral symmetry breaking.

  25. Studies of Nucleon Resonance Structure in Exclusive Meson Electroproduction • I. G. Aznauryan, A. Bashir, V. Braun, S.J. Brodsky, V.D. Burkert, L. Chang, Ch. Chen, B. El-Bennich, I.C. Cloët, P.L. Cole, R.G. Edwards, G.V. Fedotov, M.M. Giannini, R.W. Gothe, F. Gross, Huey-Wen Lin, P. Kroll, T.-S.H. Lee, W. Melnitchouk, V.I. Mokeev, M.T. Peña, G. Ramalho, C.D. Roberts, E. Santopinto, G F. de Teramond, K. Tsushima, D.J. Wilson 27 authors – 99 pages • Will be published in Int. J. Mod. Phys. E22, 1330015 (2013). http://arxiv.org/abs/1212.4891

  26. Evidence for new N* states and couplings Bonn-Gatchina Analysis – A.V. Anisovich et al., EPJ A48, 15 (2012) Strong impact from the CLAS KY photoproduction data on the signala from new states New states still need to be confirmed

  27. Whystudies of ground and excited nucleon states combined are needed? Di-quark content of ground and N* states from DSEQCD with vector x vector interaction, C.D.Roberts et al., AIP Conf. Proc. 1432, 309 (2012). N* spectrum and structure from LQCD, J.J.Dudek, R.G.Edwards, Phys. Rev. D85, 054016 (2012). • N* states of different quantum numbers offer complementary information on mechanisms of baryon generation from quarks and gluons. • N* electrocouplings allow us to explore strong regime of QCD at • larger transverse distances with larger as than the ground state form factors.

  28. Impact of the Recent LQCD studies of N* Spectrum and Structure on the N* Program with CLAS/CLAS12 J.J.Dudek, R.G.Edwards, Phys. Rev. D85, 054016 (2012). • each N* state with MN* <1.8 GeV • has partner in computed LQCD • spectrum, butlevel ordering is • not always consistent to the data • wave functions of the low-lying • N* states dominate by 1-2 SU(6) • configurations, while the wave • function of high lying N*’s may • contain many SU(6) configurations • presence of hybrid-N*s with • dominant contribution of hybrid • components at MN*>1.9 GeV marked by Should be verified by experiment ! • New direction in N* studies proposed in V.D.Burkert, arXiv:1203.2373 [nucl-ex]: • Search for hybrid N*-states looking for: • overpopulation of SU(6)-multiplet; • particular behavior of gvNN* electrocouplings, which reflects presence of the hybrid • component.

  29. The Approaches for Extraction of gvNN* Electrocouplings from Np Exclusive Electroproduction off Protons Unitary Isobar Model (UIM) The Model based on fixed-t Dispersion Relations (DR) p p • the real parts of 18 invariant Npelectroproduction amplitudes are computed from their imaginary parts employing model independent fixed-t dispersion relations. • the imaginary parts of the Npelectroproduction amplitudes at W>1.3 GeV are dominated by resonant parts and were computed from N* parameters fit to the data. N N p p p N w,r,p N p N • I. G.Aznauryan, Phys. Rev. C67, 015209 (2003), I.G.Aznauryan, • V. D.Burkert, et al. (CLAS Collaboration), PRC 80. 055203 (2009). p+

  30. Resonant /non-resonant contributions from the fit of p+p-p electroproduction cross sections within the JM model W=1.51 GeV, Q2=0.43 GeV2 W=1.51 GeV, Q2=0.38 GeV2 Reliable isolation of the resonant cross sections is achieved resonant part non-resonant part full cross sections within the JM model

  31. Transition N-P11(1440) form factors in LQCD Includes the quark loops in the sea , which are critical in order to reproduce the CLAS data at Q2<1.0 GeV2 A1/2, S1/2 => F1*, F2* Mπ = 390, 450, 875MeV L box =3.0, 2.5, 2.5 f H.W. Lin and S.D. Cohen, arXiv:1108.2528 CLAS data • Exploratory LQCD results provide reasonable description of the CLAS data from the QCD • Lagrangian. • Prospects for LQCD evaluation with improved projection operators, approaching physical mp in the box of appropriate size.

  32. P11(1440) CLAS: Np and Np/Npp combined gvNN* Electrocouplings: A Unique Window into the Quark Structure Meson-Baryon Dressing D13(1520) absolute meson-baryon cloud amplitudes (EBAC) quark core contributions (constituent quark models) Data on gvNN* electrocouplings from E12-09-003experiment (Q2 > 5 GeV2) will afford for the first time direct access to the non-perturbative strong interaction among dressed quarks, their emergence from QCD, and the subsequent N* formation.

  33. CLAS CLAS CLAS Anticipated N* Electrocouplingsfrom data on Np & Nppelectroproduction P11(1440) D13(1520) S11(1535) Hall C Open circles represent projections and all other markers the available results with the 6-GeV electron beam • Examples of published and projected results obtained within 60d for three prominent excited proton states from analyses of Np and Nppelectroproduction channels. Similar results are expected for many other resonances at higher masses, e.g. S11(1650), F15(1685), D33(1700), P13(1720), … • This experiment will – for the foreseeable future – be the only experiment that can provide data on gvNN* electrocouplings for almost all well established excited proton states at the highest photon virtualities ever achieved in N* studies up to Q2 of 12 GeV2.

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