Hadron spectroscopy Pentaquarks and baryon resonances

1. • Baryon resonances Quark model description (deformed oscillator) KN for L(1405) ~ importance of qq correlation qq vs qq Chiral symmetry • Pentaquarks Full 5-body calculation ~ qq Production of Q+~ consistency of J-Lab and LEPS Hadron spectroscopyPentaquarks and baryon resonances Atsushi Hosaka, RCNP Osaka Univ. J-PARC workshop, KEK

2. At low energies Lattice QCD does a lot: Masses, Form factors, Resonances, (Interactions) qq potential, Vacuum properties Exotics (pentaquarks,…)? Are there simple way to understand them? Global/local symmetry and its breaking Relevant degrees of freedom, effective interactions ElementaryExcitation of non-perturbative vacuum (Kunihiro) => Models of QCD hopefully with one or at most few But current understanding is not at this level J-PARC workshop, KEK

3. Let us start with Quark model Simple setups: • SU(6) and small ms breaking • Harmonic oscillator potential, V(r) = kr2 • Effective residual interaction Gluons, Chiral mesons, instantons, … To test the quark model, let us see baryon states J-PARC workshop, KEK

4. Well established states 49 ***,**** states out of 50 13 * , ** states out of 31 62 states out of 81 states But if we rearrange Light flavor (uds) baryons J-PARC workshop, KEK

5. • Measured from the ground state • 8MS states are shifted downward by 200 MeV Positive parity baryons J-PARC workshop, KEK

6. Negative parity baryons • Measured from the 1/2+ ground state • 48MS states are shifted downward by 200 MeV J-PARC workshop, KEK

7. Deformed Oscillator Model Takayama-Toki-Hosaka Prog.Theor.Phys.101:1271-1283,1999 • Ground state: spherical • Excited states: Single particle excitation deforms the confining potential Deformed states rotate collectively => Resonances as collectively rotated states J-PARC workshop, KEK

8. • Also qqq* states can mix with qqq(qq) L(1520) as a KN state => Hyodo • Chiral symmetry It seems that we make a good job BUT: Is this the end of the story??? Important questions: • Quark correlations qq or qq Roper as a diquark states => Nagata J-PARC workshop, KEK

9. Role of qq (meson)correlation Meson clouds Long time being said, but renewed interests due to chiral perturbation and its unitarization Interaction Resonance L Tomozawa-Weinberg Basic assumptions: Ground state hadrons as building blocks: B and M Contact MB interaction dominates the s-wave dynamics J-PARC workshop, KEK

10. The state is crucially important for the K-nuclei KN ~ 8 x 8 = 1, 8, 8, 10, 10, 27 attractive repulsive pS -> pS 1390 + 66i (pS) 1426 + 16i (KN) KN -> pS Jido-Oller-Oset-Ramos-Meissner, Nucl.Phys.A725:181-200,2003: nucl-th/0303062 L(1405) Two poles near Mass ~ 1405 K–p –> ppS, Magas-Oset-Ramos, Phys.Rev.Lett.95:052301,2005 J-PARC workshop, KEK

11. qq-correlation vs.qq-correlation qq correlation is equally or more important than qq for equal masses. If m>>m, then qq is suppressed In the quark language Color-spin interaction qq(C, S) (3*C, 0S) (3*C, 1S) (6C, 0S) (6C, 1S) –1/2 +1/6 +1/4 –1/12 qq(C, S) (1C, 0S) (1C, 1S) (8C, 0S) (8C, 1S) –1 +1/3 +1/8 –1/24 To see qq correlations, heavy quark systems may be suited J-PARC workshop, KEK

12. Chiral symmetry Conventional wisdom: • Chiral symmetry is spontaneously broken • <qq> condenses • Quarks couples to <qq> and obtain a constituent mass Questions: • What is the coupling of hadrons to <qq> ~ Hadron mass • What are chiral (parity) partners • What is the realization of chiral symmetry Linear vs. non-linear J-PARC workshop, KEK

13. Small fp , ms Large fp , ms They are related to: How far our world is from the symmetric world How strongly chiral symmetry is broken J-PARC workshop, KEK

14. If symmetry breaking is not very large => Particles in chiral group representations SU(2)L x SU(2)R Baryons: (1/2, 0), (1, 1/2), (3/2, 0), …. N N, D, D, with mixings Mesons: (0, 0), (1/2, 1/2), (1, 0), … s , s, p, r, a1 • For baryons, chiral partners can be made by Particles of the same parity(N, D, R) S. Weinberg,Phys.Rev.177:2604-2620, 1969 Particles of opposite parities (N, N*) Jido-Hosaka-Oka,Prog.Theor.Phys.106:873-908,2001 Jido-Hatsuda-Kunihiro, Phys.Rev.Lett.84:3252,2000 J-PARC workshop, KEK

15. • gA ~ 1.25 close to 1 => N ~ (1/2, 0) + (1, 1/2) • There could be N* of gA < 0 • Masses of chiral partners degenerate as symmetry recovers BUT we need more studies to clarify the role of chiral symmetry J-PARC workshop, KEK

16. Pentaquarks J-PARC workshop, KEK

17. qq qq 5-body calculation for Q+ Hiyama et al, hep-ph/0507105 Most serious calculation for 5-body system with scattering states included Gaussian expansion method + NK-scattering Q+-confined Compute phase shifts J-PARC workshop, KEK

18. Hamiltonian NR quark model of Isgur-Karl J-PARC workshop, KEK

19. • Mass is too high • Strong qs correlation –> JW configuration is suppressed Diquark formation is a dynamical problem KN-phase shifts 1/2+ Eres ~ 530 MeV Gres ~ 110 MeV J-PARC workshop, KEK

20. Production J-PARC workshop, KEK

21. g p –> n K+ K0 g d --> K+ K- p (n) g10 CLAS g11 ? Preliminary LEPS g d -> K+ K– p n g n -> n K+ K– J-Lab J-PARC workshop, KEK

22. Beam line LEPS J-Lab LEPS has observed but CLAS does not Observation 1 LEPS: forward angle region CLAS: side J-PARC workshop, KEK

23. Observation 2 Nam-Hosaka-Kim, hep-ph/0503149, PRD, 71:114012,2005 hep-ph/0505134 • Large p, n asymmetry (Charge exchange) >> (Charge non-exchange) • Strongly forward peaking J-PARC workshop, KEK

24. Effective Lagrangian approach u s t contact present only for charge exchange n –> Q+ or p –> L(1520) J-PARC workshop, KEK

25. gn -> K– L(1520) and gp -> K0 L(1520) Before the Q-production was studied and large pn asymmetry was known to us Nam-Hosaka-Kim, hep-ph/0503149 to appear PRD Energy dependence t (or q) dependence J-PARC workshop, KEK

26. L(1520) JP = 3/2– gp –> K+L(1520) Charge exchange L = 700 MeV <=> r ~ 0.8 fm Contact term • Large pn asymmetry • Strong forward peak • Polarization?? To be checked by experiments J-PARC workshop, KEK

27. For Q+ gn –> K–Q+ Charge exchange G = 1 MeV, L = 700 MeV <=> r ~ 0.8 fm The total cross section is very sensitive to L • Large pn asymmetry • If Q+ is larger in size, s may be smaller and strongly forward peaking •s ~ few nb or less -> consistent with the CLAS result J-PARC workshop, KEK

28. Summary • Hadrons seem to need different ingredients: constituent quarks, diquarks, mesons, chiral symmetries. • Perhaps we need a simple setup having a predictive power, consistent with QCD, and explaining ground to resonant states, decay/productions,… • Pentaquarks may still survive, which should be explained by the same setup • Experimentally: exotics containing multi-quarks and antiquarks are good laboratory to study the relevant questions. J-PARC workshop, KEK

29. J-PARC workshop, KEK

30. Why hadrons? Everybody knows that: • The core of matter (made of atoms) • Strongly interacting quantum system of QCD • Rich aspects in phase structure They are based on: hadron structure and reactions from quarks (QCD) J-PARC workshop, KEK

31. But not so easy Due to non-perturbative dynamics Color confinement and chiral symmetry breaking Is it possible to describe hadron properties? Can we predict masses, form factors, decay/production rates and so on? Can we predict unknown states prior to experiment? J-PARC workshop, KEK

32. Log-scale Theta production, JP = 3/2 Total s Log-scale Angular dist neutron ~ forward peak Contact term proton ~ rather flat J-PARC workshop, KEK

33. Good for conventional baryons Charge radii Mass Magnetic moments J-PARC workshop, KEK

34. LEPS: deuteron -> (Theta, L(1520)) L(1520) We need to understand g K d • Reaction mechanism Soft K? N MNK Q • Elementary process Q+, L(1520) production • Consistency between the J-Lab experiment J-PARC workshop, KEK