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Yongseok Oh

8/24/09 HEP Seminar. Spectrum and Production of Strange Baryons. Yongseok Oh. Overview. Nuclear & Hadron Physics Structure of hadrons Effective theories and models for QCD Mechanisms of particle production Relativistic heavy ion physics Matter at extreme conditions New state of matter

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Yongseok Oh

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  1. 8/24/09 HEP Seminar Spectrum and Production of Strange Baryons Yongseok Oh

  2. Overview • Nuclear & Hadron Physics • Structure of hadrons • Effective theories and models for QCD • Mechanisms of particle production • Relativistic heavy ion physics • Matter at extreme conditions • New state of matter • Rare Isotopic Accelerator • Structure of atomic nuclei • Nucleosynthesis • Missing resonance problem • Spectrum of baryons containing strange quark(s) KISTI, Aug, 2009

  3. Hadron physics Structure of hadrons • To understand hadron spectroscopy • To understand QCD in low energy scale • To understand the response of hadrons to the probe Have we discovered enough hadrons? KISTI, Aug, 2009

  4. Heavy ion physics Hadrons under extreme conditions • To understand Early universe, Neutron stars.. • To understand QCD in non-perturbative domain • To understand generation of mass, confinement of quarks, its relation symmetries New state of matter? KISTI, Aug, 2009

  5. GSI How do we study hadrons & nuclei? JLab RHIC SPring-8 KISTI, Aug, 2009

  6. New & future accelerators LHC JLab (upgrade) J-PARC GSI (upgrade) KISTI, Aug, 2009

  7. Particle zoo (mesons) Pseudoscalar mesons Vector mesons And meson resonances (excited states) KISTI, Aug, 2009

  8. Particle zoo (baryons) And baryon resonances (excited states: orbital angular momentum) KISTI, Aug, 2009

  9. Flavor SU(4) mesons baryons Other exotic hadrons KISTI, Aug, 2009

  10. Missing resonance problem Particle Data Group: ~ 100 mesons and ~ 80 baryons (about 20 nucleon and D resonances) Quark model vs Experiment Many particles are missing in PDG. • Failure of quark model? • Quark model predictions for N* gpN Search for resonances in other reactions! KISTI, Aug, 2009

  11. Dynamical coupled-channel analysis Hadron Production data QCD N* parameters Hadron models + QCD sum rules + Lattice QCD Dynamical reaction model + Amplitude analysis Information on hadron structure KISTI, Aug, 2009

  12. Vector meson photoproduction Four ground vector mesons (r, w, f, K*) meson pomeron Photoproduction of f YOet al, PRC58, PRL79 Searching for missing resonances KISTI, Aug, 2009

  13. w meson photoproduction YOet al, PRC63, PRC66 • Major background: pion exchange with N* Pomeron exch. pion exch. + N* without N* Total cross section Differential cross section Dominant N*: N(1910) with 3/2+ : missing resonance, N(1960) with 3/2- : D13(2080) in PDG KISTI, Aug, 2009

  14. w meson photoproduction Cross sections are not enough. Spin asymmetries are needed. JLab: first data coming soon with N* with N* without N* without N* Parity asymmetry Double asymmetry KISTI, Aug, 2009

  15. S*(1350) production YOet al, PRC77 Role of nucleon & D resonances in With N*/D* Without N*/D* Total cross section KISTI, Aug, 2009

  16. S* production YOet al, PRC77 Predictions for LEPS (SPring8): predictions data: LEPS (2008) Differential cross section Photon beam asymmetry KISTI, Aug, 2009

  17. Hadron models • Quark-based models • (relativistic) quark model (with effective potential) • Diquark model • Nambu—Jona-Lasinio model (chiral symmetry) • Bag models • 1/Nc expansion • Effective theories • Chiral perturbation theory • Heavy quark effective theory • QCD sum rules • Skyrme soliton model • and so on… KISTI, Aug, 2009

  18. What do we know about X baryons • Strangeness -2 baryons: qss (q: light u/d quark) • Baryon number = 1, isospin = 1/2 • If flavor SU(3) symmetry is exact for the classification of all particles, then we have N(X*) = N(N*) + N(D*) • Currently, only a dozen of X baryons have been identified so far. (cf. more than 20 N*s & more than 20 D*s) KISTI, Aug, 2009

  19. X in PDG • What do we know about X baryons? Particle Data Group (2006): 11 X’s Parity: not directlymeasured Cf. Spin of W- = 3/2 was confirmed by BaBar PRL 97 (2006) States whose JP is known KISTI, Aug, 2009

  20. What do we know about X baryons • Strangeness -2 baryons: qss (q: light u/d quark) • Baryon number = 1, isospin = 1/2 • If flavor SU(3) symmetry is exact for the classification of all particles, then we have N(X) = N(N*) + N(D*) • Currently, only a dozen of X have been identified so far. (cf. more than 20 N*s & more than 20 D*s) • Only X(1318) and X(1530) have four-star status • Only three states with known spin-parity • Even the quantum numbers of most X resonances are still to be identified • Practically, no important information for the X resonances. KISTI, Aug, 2009

  21. What can we learn from X? • Baryon structure from X spectroscopy • Properties of S=-1 resonances(through the study on production mechanisms) • Exotic particles (penta-quarks & tetra-quarks)(purely exotic, not cryptoexotic) • New particles (perhaps an S=-4 dibaryon?) KISTI, Aug, 2009

  22. Characters of the X hyperons • Narrow widths: G(X*)/G(N* or D*) ~ 1/10 for pionic decays • G is proportioanl to (# of light valence quarks)2Riska, EPJA 17 (2003) Decuplet g octet + p from J. Price KISTI, Aug, 2009

  23. X baryons in Experiments • Good Things • Small decay widths • Narrow peaks • Identifiable in a missing mass plot, e.g.,missing mass Mc(K+K+) in g + p g K+ + K+ + X,invariant mass of decay products such as Xgp L • Background is less complicated. (g + p g K+ + K+ + X*g K+ + K+ + p + Xgs) • Isospin ½(cf. nucleonic resonances have N* & D*; I=1/2 and 3/2)(baryons with one strange quark: L & S hyperons) KISTI, Aug, 2009

  24. Bad Things • Mostly processes through K-p reactions or the S-hyperon induced reactions were used. (initial state has S=-1) • No current activity in X physics with hadron beams • They can only be produced via indirect processes from the nucleon. (initial state has S=0) • In the case of photon-nucleon reaction, we have at least three-body final state. • The current CLAS data indicate that the production cross section is less than 20 nb at low energies. (cf. KL or KS photoproduction have cross sections of order of a few mb). • Other technical difficulties KISTI, Aug, 2009

  25. PDG says • Particle Data Group (2006) KISTI, Aug, 2009

  26. WA89 (CERN-SPS) • S--nucleus collisions EPJC, 11 (1999) KISTI, Aug, 2009

  27. Exotic X(1860) or F(1860) • Isospin-3/2 state: therefore, penta-quark exotic • Report from NA49 in pp collision PRL 92 (2004) • but never be confirmed by other experiments with higher statistics, e.g. WA89 PRC 70 (2004) WA89 NA49 KISTI, Aug, 2009

  28. Earlier experiments • WA89 results (hep-ex/0406077) 1530 1690 1860(?) KISTI, Aug, 2009

  29. Recent activity • CLAS at JLab: initiated a Cascade physics programphotoproduction processes: gp g KKX PRC 71 (2005) nucl-ex/0702027 KISTI, Aug, 2009

  30. More on CLAS data X(1530) X(1620) & X(1690) ? Need higher statistics ! Invariant mass distribution in the Xp channel Also cross sections for X photoproduction KISTI, Aug, 2009

  31. Possible Questions • What is the third lowest state following X(1320) and X(1530)? X(1620) vs X(1690) • Does X(1620) exist? • Spin-Parity of the excited states? KISTI, Aug, 2009

  32. 3. X baryons in theories • Review on the works before 1975Samlos, Goldberg & Meadows, Rev. Mod. Phys. 46 (1974) 49 • Classify the states as octet or decuplet (depending on the spin-parity, use Gell-man—Okubo mass rel.)(recent work along this line; Guzey & Polyakov, hep-ph/0512355) • What is the third state following X(1320) and X(1530)? • Quantum numbers? Couplings & decay channels • Most model builders have not considered X spectrum or the structure of X resonances seriously, except the lowest X’s of octet and decuplet. • Most model gives (almost) correct values for X(1320) & X(1530). • But the predictions on the higher states are quite different. KISTI, Aug, 2009

  33. Nonrelativistic Quark Model • Chao, Isgur, Karl,PRD 23 (1981) • X(1690)*** has JP=1/2+ ? • The first negative parity state appears at ~1800 MeV. • Decay widths are not fully calculated by limiting the final state. (but indicates narrow widths) • Relativistic quark model ? The 3rd lowest state at 1695 MeV? from S. Capstick KISTI, Aug, 2009

  34. Relativistic Quark Model • Capstick & Isgur PRD 34 (1986) RQM NRQM The 3rd lowest state? KISTI, Aug, 2009

  35. One-boson-exchange model • Glozman & Riska, Phys. Rep. 268 (1996) • Exchange of octet pseudoscalar mesons. First order perturbation calculation around harmonic oscillator spectrum. • Negative parity state seems to have lower mass: but no clear separation between +ve and –ve parity states • Strong decay widths are not calculated. The 3rd lowest state? KISTI, Aug, 2009

  36. Comparison of NRQM & OBE • The two models show very different X hyperon spectrum. • The predictions on the candidate for X(1690) are different. KISTI, Aug, 2009

  37. Large Nc (constituent quark model) Expand the mass operator by 1/Nc expansion • Basically O(3) X SU(6) quark model • Mass formula (e.g. 70-plet: L=1, p=-1) • Fit the coefficients to the known particle masses and then predict. Where is X(1690)? from J.L. Goity KISTI, Aug, 2009

  38. Schat, Scoccola, Goity, PRL 88 (2002) and other groups The 3rd lowest state? KISTI, Aug, 2009

  39. KISTI, Aug, 2009

  40. Quark-based models • The third state • Expt. X(1620)*, X(1690)***, spin-parity unknown • NRQM: 1695 MeV with 1/2+ • RQM: 1755 MeV with 1/2- • OBE: 1758 MeV with 1/2- or 3/2- • Large Nc: 1780 MeV with 1/2- • Algebraic model: 1727 MeV with 1/2+ • Highly model-dependent: expt. should judge • The predicted masses are higher than 1690 MeV (except NRQM) • How to describe X(1690)? • The presence of X(1620) is puzzling, if it exists. • Cf. similar problems in quark models: L(1405) KISTI, Aug, 2009

  41. QCD sum rules • Mass splitting between 1/2+ and1/2- baryons. • Jido & Oka,hep-ph/9611322 • Interpolating field (with a parameter t) • X(1/2+) = 1320 MeV and X(1/2-) = 1630 MeV. • So, X(1690) would be X(1/2-). • Sum rules for 1/2+, 1/2-, and 3/2-. • F.X. Lee & X. Liu,PRD 66 (2002) • Three-parameter calculation (similar interpolating field) • X(1/2+) = 1320 MeV, X(1/2-) = 1550 MeV, X(3/2-) = 1840 MeV (exp. 1820 MeV) • X(1820) is well reproduced, but where is X(1690)? KISTI, Aug, 2009

  42. Lattice calculation • Quenched approx. • Level cross-over in the physical region? • Results for 1/2+ and 1/2- states 1/2- 1/2+ F.X. Lee et al., NPB(PS) 119 (2003) KISTI, Aug, 2009

  43. Lattice calculation • Quenched approx. (variational method) • The first excited state seems to have -ve parity at 1780 MeV. (two states are nearly degenerate) • Bern-Graz-Regensburg Coll., PRD 74 (2006) X with J = 1/2 KISTI, Aug, 2009

  44. Skyrme models • Baryons are topological solitons in the nonlinear meson field theory. • In SU(2)F, it gives N and D. • Extension to SU(3) • Is SU(3) a good symmetry for baryon structure? SU(3) collective rotation (Chemtob, Prasalowicz, …) Ms ~ Mqperturbative treatment for symmetry breakers Exact diagonalization (Yabu, Ando, …) Ms > Mqdiagonalize the total Hamiltonian Bound state approach (Callan, Klebanov, …) Ms >> Mqdifferent treatment for isospin and strangeness KISTI, Aug, 2009

  45. bound Kaon Bound state approach SU(3) is badly broken Treat light flavors and strangeness on the different footing L = LSU(2) + LK/K* Soliton provides background potential which traps K/K* (or heavy) meson KISTI, Aug, 2009

  46. Bound state approach Anomaly terms • Push up the S = +1 stateto the continuum}no bound state • Pull down the S = -1 statebelow the threshold}bound state N, D: almost SU(2) object Hyperons: bound states ofthe soliton and K/K* Heavy vector mesons • Should be treatedexplicitly • Gives the correct heavyquark symmetry of theresulting baryon spectrum}degenerate S and S* Heavy quark baryons: bound states of the soliton and heavy meson (D/D*, B/B*) KISTI, Aug, 2009

  47. Bound state approach • Renders two bound states with negative strangeness • P-wave; lowest state • S-wave: first excited state • After quantization • P-wave aL(1116) +ve parity hyperon • S-wave aL(1405) -ve parity hyperon • Mass formula 270 MeV energy difference KISTI, Aug, 2009

  48. PDG 18 L’s 26 S’s 11 X’s 4 W’s KISTI, Aug, 2009

  49. Hyperon spectrum (expt) parity undetermined negative parity 290 MeV positive parity 285 MeV 289 MeV KISTI, Aug, 2009

  50. Mass spectrum Nearly equal spacings between particles of same spin and of opposite parity (~300 MeV) Mass differences L(1/2)=L(1/2-)-L(1/2+): 289 S(1/2): 311, S(3/2): 278 X(3/2): 290, 300 W(3/2): 284, 304, 322, W(1/2): 303 YO, PRD 75 Spin-parity not known KISTI, Aug, 2009

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