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NSTAR 2007 Summary

NSTAR 2007 Summary. Experiment/analysis Facilities/new results Upcoming developments Theory Baryons Dynamics of reactions involving baryons. BRAG pre-meeting. L. Tiator, A. Svarc; problem relating experimental results to theoretical predictions

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NSTAR 2007 Summary

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  1. Simon Capstick, Florida State University

  2. NSTAR 2007 Summary • Experiment/analysis • Facilities/new results • Upcoming developments • Theory • Baryons • Dynamics of reactions involving baryons Simon Capstick, Florida State University

  3. BRAG pre-meeting • L. Tiator, A. Svarc; problem relating experimental results to theoretical predictions • Partial wave analysis and amplitude analysis give reliable results for dressed scattering matrix singularities • Quark model calculations give information on bare resonant quantities • Does not apply to those states seen in chiral unitary models—see talks by A. Ramos, E. Oset, A. Martinez Torres, and M. Doering at this meeting • Dressing (un-quenching) the quark model is tough, but solvable in principle • See talks by E. Santopinto, R. Bijker, and B. Pasquini at this meeting; S.C. and M. Giannini in BRAG pre-meeting • Undressing dressed scattering matrix singularities in coupled-channel models is in principle a model-dependent procedure because of presence of model-dependent hadronic mass shifts • From unmeasurability of off-shell effects accompanying any dressing procedure. • BRAG pre-meeting talks by Ch. Hanhart, S. Scherer, J. Gegelia Simon Capstick, Florida State University

  4. BRAG pre-meeting Conclusions: (1) Bare quantities in coupled-channel models are legitimate quantities to be extracted • Only within a framework of a well defined model • To interpret, keep track of the existence of the hadronic mass shifts produced by off-shell-ambiguities (2) Dressed scattering matrix singularities are best meeting point between quark model predictions and experiments • Recommendation: put a lot of effort into defining and thoroughly checking the pole extraction procedures • starting either from energy dependent partial waves or from partial wave data directly Simon Capstick, Florida State University

  5. Experimental programs for N* • Common developments: • Precision data on host of final states • Emphasis on N, N, 2N, N, K, K,… • Polarization (beam, target, double planned or underway) • Aim is to measure as many observables as possible for a subset of these reactions (“complete” experiments) • Reduce (not eliminate) model dependence of analysis • Challenge for models to fit polarization observables • Strong sensitivity to resonance properties • This is how physics progresses! Simon Capstick, Florida State University

  6. Expt. CLAS@Jefferson Lab • V. Burkert: CLAS collaboration • Major focus is N* physics • the search for new baryon states and determination of baryon resonance properties • resonance transition form factors • Nucleon spin structure in the transition region • polarized proton structure function g1(x,Q2) • Bjorken Sum: 1p-n(Q2) • Deeply exclusive processes and generalized parton distributions (GPDs) • DVCS/Bethe-Heitler beam spin asymmetry sensitive to H Simon Capstick, Florida State University

  7. Expt. CLAS@Jefferson Lab • Search for new baryon states • Aim for “complete” or nearly complete measurements • γp→πN, ηN, K+Y and γn→πN, K0Y • Combinations of beam, target (new FROST target), and recoil polarizations • differential cross sections with unpolarized, circularly polarized, and linearly polarized photon beams • recoil polarizations for hyperons • longitudinally or transversely polarized proton and neutron (deuteron) targets • Other reactions • γp → ρN, ωp, ππN • linearly polarized beams, polarized beam and polarized targets Simon Capstick, Florida State University

  8. Expt. CLAS@Jefferson Lab • R. Schumacher: polarization transfer in K+Λ photo and electro-production • Polarized beam,  (recoil) polarization through its weak decay asymmetry • New GRAAL results for recoil polarization P agree with CLAS results • Large polarization transfer Cz along circularly polarized photon beam direction • Find P2 + Cx2 + Cz2 ' 1 • Models did not predict this • Bonn, Giessen, Gatchina (Sarantsev, Nikonov, Anisovich, Klempt, Thoma ) fit with additional resonance P13(1860) • See talks by A. Sarantsev, V. Nikonov this meeting • Beam asymmetry  featureless (GRAAL, LEPS) Simon Capstick, Florida State University

  9. Expt. CLAS@Jefferson Lab Simon Capstick, Florida State University

  10. Expt. CLAS@Jefferson Lab Simon Capstick, Florida State University

  11. Expt. CLAS@Jefferson Lab • V. Burkert, V. Mokeev • Q2 dependence of EM transition form factors (0-6 GeV2) using CLAS@Jefferson Lab • Probes evolution of relevant degrees of freedom in baryons • e-N ! ! N • Dominant M1 contains non-resonant effects involving , at level of 30% • Ratios of electric and scalar (quadrupole) multipoles to M1 measured to 0.5-2% over entire range of Q2 • Do not tend to pQCD limits • e-N ! N½+(1440)! N, N • Changes sign at Q2 ~ 0.5 GeV2 (seen in relativistic models based on light-cone dynamics) • Consistent results using different analysis methods, different final states Simon Capstick, Florida State University

  12. Expt. Electron scattering labs… Nπ, pπ+π- nπ+ DR UIM nπ+ pπ0 pπ0 • CLAS@Jefferson Lab Simon Capstick, Florida State University

  13. Expt. Electron scattering labs… D13(1520) P11(1440) from analysis of 1p CLAS data from analysis of CLAS 2p data within the framework of JM06 combined analysis of 1p/2p CLAS data Simon Capstick, Florida State University

  14. PDG Nπ, pπ+π- nπ+ nπ+ pπ0 pπ0 Expt. Electron scattering labs… • N3/2-(1520)D13 A3/2 Previous pπ0 based data preliminary preliminary A1/2 Q2, GeV2 Q2, GeV2 Simon Capstick, Florida State University

  15. Expt. CLAS@Jefferson Lab • Cascade (0 ssu, - ssd) baryon program • Advantage that low-lying states are likely narrow γp―>K+K+Ξ-* γp―>π-K+K+Ξ0* Simon Capstick, Florida State University

  16. Expt. BaBar • Veronique Ziegler: e+e- annihilation at BaBar (results preliminary, under BaBar internal review) • Study 0(1530) in c+ ! (-+) K+ • Indication is J=3/2 (confirms decuplet expectation) • Study 0(1690) in c+ ! (LK0) K+ • Preferred spin is J=1/2, some indication of negative parity If negative parity, not Roper equivalent as some of us (!) thought Much too light for quark model expectations of L=1 excited states N* + 2(ms-mu,d) ! Calculable on the lattice (D. Richards) Simon Capstick, Florida State University

  17. Expt. Crystal Barrel/TAPS@ELSA • H. Schmieden: Physics at ELSA • Photoproduction of baryon resonances • ELSA • photon beam energy (to 2.5 GeV) • Linear and circular polarization • CB/TAPS • provides ~4 detection • Best for neutral final states (missing mass for a charged particle) through their photon decays Simon Capstick, Florida State University

  18. Expt. Crystal Barrel/TAPS@ELSA • Goal: “complete” experiments on and photoproduction • Analysis simplified because only make N* (no D*) • Recent results: • Unpolarized photoproduction of  • Differential cross sections • From  and 30! 6 decays of  • Linearly polarized photoproduction of  (D. Elsner talk) Simon Capstick, Florida State University

  19. Expt. Crystal Barrel/TAPS@ELSA • D. Elsner: linearly polarized photoproduction of  • Targetpolarization  • Consistent withGRAAL results Simon Capstick, Florida State University

  20. Expt. Crystal Barrel/TAPS@ELSA • Photoproduction of  off deuteron Simon Capstick, Florida State University

  21. Expt. Crystal Barrel/TAPS@ELSA • Data analysed to d/d • Bonn-Gatchina PWA: see P11(1840) • Polarization asymmetries R,  Simon Capstick, Florida State University

  22. Expt. Crystal Barrel/TAPS@ELSA • Talk by E. Gutz: polarization asymmetry  in • Bonn-Gatchina PWA: (1940)D33 Simon Capstick, Florida State University

  23. Expt. Crystal Barrel/TAPS@ELSA • Polarized photoproduction of  • Penner et al. and Shkylar (Giessen) analyses disagree Simon Capstick, Florida State University

  24. Expt. ANKE, TOF@COSY • W. Schroeder • ANKE can see Y* states up to 1540 MeV, TOF is best for threshold region • pp! pK+Y0*! pK+§ X¨ • Select events where X- = -, plot vs. MM(pK+): • Effect in X-+at 1480 MeV,=60 MeV • Also in X+- Simon Capstick, Florida State University

  25. Expt. ANKE, TOF@COSY • ANKE: line shape of (1405) • Not Breit-Wigner, see talk by E. Oset this meeting L.S. Geng, E. Oset, arXiv: 0707.3343 Simon Capstick, Florida State University

  26. Expt. ANKE, TOF@COSY • TOF: • See no + pentaquark in pp! (pK0)+ or in (pK0)+ • Need polarized beam, target and detector improvements to continue program of examining N*! YK in 1.6-1.9 GeV region • New detector WASA ( and neutrals) will allow study of excited hyperons pp! pK+(1405)! pK+00! pK+()0 Simon Capstick, Florida State University

  27. Expt. Crystal Ball/TAPS@MAMI • M. Kotulla • Determination of magnetic moment of +(1232) • Use  p!0 0 p Simon Capstick, Florida State University

  28. Expt. Crystal Ball/TAPS@MAMI • Analysis effort underway • Pascalutsa and Vanderhaeghen, chiral effective theory (good to E’ ~ 100 MeV) • Sensitivity ~ 0.2 N Simon Capstick, Florida State University

  29. Expt. BESII@IHEP • W. Li: light hadron spectroscopy in J/ decays • New states: • ,  (masses and widths determined) • X(1835) in J/ ’ • X(1580) in J/ KK • Enhancement in J/  • (1760) in J/  • N* observed in: • J/ pn ; J/ pp0 ; J/ nKS; Compared with (2S) decay; • Some N*, e.g. N*(1535), N*(2065) better measured • Some branching fractions involving baryons are measured • Analysis of existing data ongoing • BEPCII/BESIII should collect data in 2008 Simon Capstick, Florida State University

  30. Expt. LNS@Sendai • H. Shimizu: observation of N*(1670) • Have 300 MeV e- linac coupled to a 1 GeV synchroton • Use d !X • Also p !X to subtract proton contribution • Use -MAID analysis to understand p !p • Interpret as new S11 at 1670 MeV, width below 50 MeV, strong in n !n • Not seen in proton channel • Could this be an antidecuplet pentaquark? Simon Capstick, Florida State University

  31. Expt. LEGS@BNL • A. Sandorfi: Physics at LEGS • LEGS-Spin collaboration • LEGS 2.8 GeV e- beam, backscattered laser beam, maximum photon energy ~430 MeV • High circular polarization • HD frozen spin • Hydrogen polarized or D polarized or both • Mostly HD and a little H2 and D2 which feed HD polarized state (then decay away themselves, so HD spin frozen) • Spin relaxation times ~ 1 year • Can transfer polarization from H to D • Polarized photon + HD double-polarization physics • Measure various polarization asymmetries in inclusive and exclusive  HD ! X reactions on neutron • Use Lee Sato Matsuyama  N! N amplitudes and fold into D structure Simon Capstick, Florida State University

  32. Expt. LEGS@BNL • Analysis • Not a free neutron! Only half of the events are quasi-free • Analysis of data on-going: separate § using momentum analysis • Targets and some of staff migrating from BNL to JLab • E06-101 (pol) + HD ! K0(pol), K0(pol), i.e. n • Electron experiments on transversely polarized target • GPDs, N* form factors, Collins/Sivers functions… Simon Capstick, Florida State University

  33. Expt. MAMI@Mainz • A. Thomas: Physics at MAMI • Virtual and real photons, linear and circular polarization • Three detectors Kaos,…,Crystal Ball/TAPS • MAMI: • Harmonic double-sided microtron (electron accelerator) • four bending magnets and two linacs • Energy 0.855-1.5 GeV • Tagged photon and electron scattering experiments • Experiments • Target asymmetry puzzle in  and 0 production off proton • Isobar models and Giessen models fail to describe • Electroproduction of  at low Q2 • Cross section and recoil polarization • Single and double pion production • Helicity asymmetry in double-pion production • Discrepancies with models Simon Capstick, Florida State University

  34. Expt. MAMI@Mainz • Physics at MAMI: • , 0 physics  mass, rare  decays (C,CP violation) Quark mass different mu-md in ! 30 0!00 decays • GDH experiment @ MAMI-B with DAPHNE detector (charged particle tracking) • Polarized butanol target with high deuteron polarization • MAMI/ELSA GDH sum rule 3/2-1/2 • Verified at 10% level • Also in exclusive reactions, important for PWAs • Have for  production • Photoproduction of p+- • Helicity-dependent invariant mass distributions • The future: • Frozen spin target for Crystal Ball—built this year • Recoil polarization of proton • Kaos—kaon electroproduction Simon Capstick, Florida State University

  35. Theory developments • Both lattice QCD and quark model calculations must face reality of light quark pairs • “Un-quenching” either is hard work • Requires calculation of couplings to continuum states • Coupled-channel analyses are becoming increasingly sophisticated • Need to preserve unitarity, gauge invariance, and analytic structure, but remain manageable Simon Capstick, Florida State University

  36. Theory Lattice QCD • The nucleon and baryon resonances on the lattice: C. Gattringer (Graz-Regensburg), D. Richards (LHPC collaboration), A. Rusetsky • Recent important developments • Basic quantities are Euclidean two and three-point functions • Time dependence of two-point functions gives masses • Matrix elements in three-point functions give properties • Extraction of excited state masses using carefully chosen basis of interpolators Oi • Use these to construct a matrix of correlators • Solve eigenvalue problem to get accurate signal for mass of excited states Simon Capstick, Florida State University

  37. Theory Lattice QCD… • Eigenvalues (t) vs. Euclidean time Simon Capstick, Florida State University

  38. Theory Lattice QCD • Recent important developments… • Hadron interpolators distributed over spatial lattice points • LHPC collaboration, Graz-Regensburg • classify into irreducible representations of lattice rotation group • Allows nodes in radial wave function • Can avoid chiral extrapolations by using chiral perturbation theory in a finite volume (small-scale expansion): See talk by A. Rusetsky, this meeting • Luscher formalism developed for N scattering • Use statistical method to extract resonance mass and width from lattice results • Demonstrated for (1232) mass and width Simon Capstick, Florida State University

  39. Theory Lattice QCD… • Spatially distributed interpolators • Much better overlap with excited states Simon Capstick, Florida State University

  40. Theory Lattice QCD… • Baryon spectrum, quenched calculations Simon Capstick, Florida State University

  41. Theory Lattice QCD… Simon Capstick, Florida State University

  42. Theory Lattice QCD… • Proton structure from three-point functions, chiral extrapolation to physical pion masses • Different treatment of valence and sea quarks allows first look at chiral regime (un-quenched) • Isovector charge form factor (p-n) • Isovector charge radius • Axial charge gA • Moments of quark momentum fraction hxiu-d and helicity fraction hxiu -d • Study of GPDs • Calculation of quark orbital angular momentum • Nucleon transverse size Simon Capstick, Florida State University

  43. Theory Lattice QCD • Lu and Ld substantial, total small Simon Capstick, Florida State University

  44. Theory Lattice QCD • Un-quenched calculations in development • Need clean separation of scattering states once decays possible • Use different volume dependence of masses of resonances and continuum states, large lattices • Working on evaluating transition matrix elements (decay constants) for resonances • Need contribution of disconnected diagrams (loops, gluons) to hadron structure • Currently sensitive to statistical fluctuations Simon Capstick, Florida State University

  45. Theory Models • B. Borasoy: chiral corrections to the Roper resonance mass • Lighter than its parity partner S11(1535) • 30-40% branch into N • Parity order not settled in lattice QCD • Need reliable chiral extrapolation techniques • Use effective Lagrangian (N, Roper, ), calculate mR(m2) to full 1-loop order (no explicit p) • Have R coupling = gA' 1.26, RN coupling (0.3-0.4), 4 chiral parameters • Infrared regularization scheme extended to one light scale (m) and two heavy (MN2 << MR2) • No strong m dependence near physical point Simon Capstick, Florida State University

  46. Theory Models • Constituent Quark Model: E. Santopinto, R. Bijker • See also talk by Qiang Zhao, this meeting, on selection rules and quark correlations in the N* spectrum • See also talk by A. Buchmann, this meeting, on calculation of higher (octupole) moments of baryons in pion-cloud quark model • Tackle difficult problem of inclusion of next Fock space component in quark model • Use large baryon-meson basis to expand qqq qq(bar) • Flux-tube breaking model gives overlap between qqq and qqq qq(bar) • Checked that calculation returns usual CQM in closure limit • Evaluate flavor asymmetry of nucleon sea Simon Capstick, Florida State University

  47. Theory Models • Results: significant difference from naïve nonrelativistic CQM results and relativistic CQM results • Closer to experiment and lattice QCD u = 1.00 uexp= 0.82(5) uLQCD =0.79(11) uNRM = 4/3 uRQM = 1.01 d=-0.43 dexp= -0.44(5) dLQCD =-0.42(11) dNRM = -1/3 dRQM = -0.251 s =-0.06 sexp= -0.10(5) sLQCD =-0.12(11) sNRM =0 sRQM = 0 Simon Capstick, Florida State University

  48. Theory Models • B. Metsch: Covariant constituent quark model • Based on instantaneous approximation to Bether-Salpeter equation • Relativistic form of confining potential, chosen to minimize spin-orbit effects • Instanton-based spin-spin interaction between quarks • Model parameters fit to spectrum • Calculate a host of other properties: • Magnetic moments and charge radii • Including magnetic moments of excited states • Resonance photocouplings and semi-leptonic decays • Strong two-body decay amplitudes • Verifies pattern of decoupling of states not seen in analyses Simon Capstick, Florida State University

  49. Theory Models • B. Metsch: Covariant constituent quark model • Provides useful background against which to search for unconventional states • Roper resonance EM couplings anomalous • Everything (mass, EM and strong couplings) about the (1405) is anomalous • Hard to understand why the second band of negative parity  states [D35 and its partners] can be as low as ~1900 MeV Simon Capstick, Florida State University

  50. Theory Models • Chiral Unitary Approach: A. Ramos, E. Oset • KN I=0 JP=1/2- (S01) scattering state (1405) is 27 MeV below threshold • Looks like quasi-bound state • Use chiral meson-baryon Lagrangian to generate an S-wave potential • Need KN, , , and K channels to fit decay branching ratios of this and nearby states • Get two poles in T matrix approaching 1400 MeV when break SU(3)f gradually • Explains why properties of (1405) depend on channel in which it is observed Simon Capstick, Florida State University

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