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

KISTI, Aug, 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, Hadron physics Structure of hadrons Have we discovered enough hadrons? 1.To understand hadron spectroscopy 2.To understand QCD in low energy scale 3.To understand the response of hadrons to the probe

KISTI, Aug, Heavy ion physics 1.To understand Early universe, Neutron stars.. 2.To understand QCD in non-perturbative domain 3.To understand generation of mass, confinement of quarks, its relation symmetries Hadrons under extreme conditions New state of matter?

KISTI, Aug, How do we study hadrons & nuclei? JLabRHICSPring-8 GSI

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

KISTI, Aug, Particle zoo (mesons) Pseudoscalar mesonsVector mesons And meson resonances (excited states)

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

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

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

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

KISTI, Aug, Vector meson photoproduction mesonpomeron Four ground vector mesons ( , , , K*) Four ground vector mesons ( , , , K*) Searching for missing resonances Photoproduction of  YO et al, PRC58, PRL79

KISTI, Aug,  meson photoproduction Major background: pion exchange YO et al, PRC63, PRC66 Pomeron exch. pion exch. + N* with N* without N* Dominant N*: N(1910) with 3/2  : missing resonance, N(1960) with 3/2  : D13(2080) in PDG Differential cross section Total cross section

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

KISTI, Aug,  *(1350) production YO et al, PRC77 Role of nucleon &  resonances in Total cross section Without N*/  * With N*/  *

KISTI, Aug,  * production Predictions for LEPS (SPring8): Differential cross section Photon beam asymmetry predictions YO et al, PRC77 data: LEPS (2008)

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

KISTI, Aug, 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, 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?) What can we learn from X?

KISTI, Aug, 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) 2 Riska, EPJA 17 (2003) Decay G exp (MeV) Ratio exp (# of light valence quark) 2 DNpDNp S*  Sp 4044 X*  Xp 1011 Decuplet  octet + p from J. Price

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

KISTI, Aug, 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. K L or K S photoproduction have cross sections of order of a few m b).  Other technical difficulties

KISTI, Aug, PDG says Particle Data Group (2006)

KISTI, Aug, WA89 (CERN-SPS) S - -nucleus collisions EPJC, 11 (1999)

KISTI, Aug, Exotic X (1860) or  (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) NA49 WA89

KISTI, Aug, Earlier experiments WA89 results (hep-ex/ ) (?)

KISTI, Aug, Recent activity CLAS at JLab: initiated a Cascade physics program photoproduction processes:  p  KKX PRC 71 (2005) nucl-ex/

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

KISTI, Aug, 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, X baryons in theories Review on the works before 1975 Samlos, 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/ ) 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, Nonrelativistic Quark Model Chao, Isgur, Karl, PRD 23 (1981) from S. Capstick X(1690) *** has J P =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 3 rd lowest state at 1695 MeV?

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

KISTI, Aug, 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 3 rd lowest state?

KISTI, Aug, 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, Large N c (constituent quark model) Expand the mass operator by 1/N c 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. from J.L. Goity Where is X(1690)?

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

KISTI, Aug,

KISTI, Aug, 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 N c : 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, QCD sum rules Mass splitting between 1/2 + and1/2 - baryons.  Jido & Oka, hep-ph/  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 MeV)  X (1820) is well reproduced, but where is X (1690)?

KISTI, Aug, 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, 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, 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 ~ Mq perturbative treatment for symmetry breakers Exact diagonalization (Yabu, Ando, …) Ms > Mq diagonalize the total Hamiltonian Bound state approach (Callan, Klebanov, …) Ms >> Mq different treatment for isospin and strangeness

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

KISTI, Aug, Bound state approach N, D: almost SU(2) object Hyperons: bound states of the soliton and K/K* Anomaly terms (i) Push up the S = +1 state to the continuum  no bound state (ii) Pull down the S = -1 state below the threshold  bound state Heavy quark baryons: bound states of the soliton and heavy meson (D/D*, B/B*) Heavy vector mesons (i) Should be treated explicitly (ii) Gives the correct heavy quark symmetry of the resulting baryon spectrum  degenerate S and S*

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

KISTI, Aug, PDG 26 S’s18 L’s 11 X’s4 W’s

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

KISTI, Aug, Mass spectrum YO, PRD 75 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 Spin-parity not known

KISTI, Aug, Mass spectrum YO, PRD 75 Recently confirmed by COSY PRL 96 (2006) J P of  (1690) is ½- BABAR: PRD 78 (2008) NRQM predicts ½ + Unique prediction of this model. Most of the quark-based models fail to describe these two states simultaneously.

KISTI, Aug, Mass spectrum Two X (1/2-) states  One kaon in P-wave and one kaon in S-wave  J = J s + J m (J m = J 1 + J 2 )  J s : soliton spin (=1/2), J 1 (J 2 ): spin of the P(S)-wave kaon (=1/2)  J m = 0 or 1  both of them can lead to J=1/2  Two J=1/2 states and one J=3/2 state  In this model, it is natural to have two 1/2- states and their masses are 1616 MeV & 1658 MeV! Cf. unitary extension of chiral perturbation theory  Ramos, Oset, Bennhold PRL 89 (2002)  1/2- state at 1606 MeV  Garcia-Recio, Lutz, Nieves, PLB 582 (2004)  X (1620) & X (1690): 1/2- states Clearly different from the quark models

KISTI, Aug, Outlook Recent studies on hadron structure  Spectrum of strange baryons  Production mechanism of baryons Programs for studying hadron structure  Full coupled-channel dynamical model  A lot of precise data from JLab, Spring-8 etc  Combined analysis of  meson production (YO et al., 2008)  JLab-EBAC  Cascade physics program  Excited Cascade particles & other exotic states like di-Cascade  Soliton model in holographic QCD  Borromean hadrons? ( , n, n) three-body system is bound, while neither ( , n) nor (n, n) are bound.