Hadron spectroscopy Pentaquarks and baryon resonances Atsushi Hosaka

Hadron spectroscopy Pentaquarks and baryon resonances Atsushi Hosaka, RCNP Osaka Univ. • 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 Nov. 30 - Dec. 2, 2005 J-PARC workshop, KEK 1

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 Elementary. Excitation of non-perturbative vacuum (Kunihiro) => Models of QCD hopefully with one or at most few But current understanding is not at this level Nov. 30 - Dec. 2, 2005 J-PARC workshop, KEK 2

Let us start with Quark model Simple setups: • SU(6) and small ms breaking • Harmonic oscillator potential, V(r) = kr 2 • Effective residual interaction Gluons, Chiral mesons, instantons, … To test the quark model, let us see baryon states Nov. 30 - Dec. 2, 2005 J-PARC workshop, KEK 3

Light flavor (uds) baryons Well established states 49 ***, **** states out of 50 13 * , ** states out of 31 62 states out of 81 states But if we rearrange Nov. 30 - Dec. 2, 2005 J-PARC workshop, KEK 4

Positive parity baryons • Measured from the ground state • 8 MS states are shifted downward by 200 Me. V Nov. 30 - Dec. 2, 2005 J-PARC workshop, KEK 5

Negative parity baryons • Measured from the 1/2+ ground state • 48 MS states are shifted downward by 200 Me. V Nov. 30 - Dec. 2, 2005 J-PARC workshop, KEK 6

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 Nov. 30 - Dec. 2, 2005 J-PARC workshop, KEK 7

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 • Also qqq* states can mix with qqq(qq) L(1520) as a KN state => Hyodo • Chiral symmetry Nov. 30 - Dec. 2, 2005 J-PARC workshop, KEK 8

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 Nov. 30 - Dec. 2, 2005 J-PARC workshop, KEK 9

L(1405) Jido-Oller-Oset-Ramos-Meissner, Nucl. Phys. A 725: 181 -200, 2003: nucl-th/0303062 The state is crucially important for the K-nuclei Two poles near Mass ~ 1405 1390 + 66 i (p. S) KN ~ 8 x 8 = 1, 8, 8, 10, 27 attractive repulsive p. S -> p. S KN -> p. S 1426 + 16 i (KN) p –> pp. S, Nov. 30 K - Dec. 2, 2005 – Magas-Oset-Ramos, Phys. Rev. Lett. 95: 052301, 2005 J-PARC workshop, KEK 10

In the quark language qq-correlation vs. qq-correlation Color-spin interaction qq(C, S) (3*C, 0 S) (3*C, 1 S) – 1/2 +1/6 (6 C, 0 S) (6 C, 1 S) +1/4 – 1/12 qq(C, S) (1 C, 0 S) – 1 (8 C, 0 S) +1/8 (1 C, 1 S) +1/3 (8 C, 1 S) – 1/24 qq correlation is equally or more important than qq for equal masses. If m>>m, then qq is suppressed To see qq correlations, heavy quark systems may be suited Nov. 30 - Dec. 2, 2005 J-PARC workshop, KEK 11

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 Nov. 30 - Dec. 2, 2005 J-PARC workshop, KEK 12

They are related to: How far our world is from the symmetric world How strongly chiral symmetry is broken Small fp , ms Nov. 30 - Dec. 2, 2005 Large fp , ms J-PARC workshop, KEK 13

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, Mesons: (0, 0), (1/2, 1/2), (1, 0), … s, p, with mixings r, a 1 • 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 Nov. 30 - Dec. 2, 2005 J-PARC workshop, KEK 14

• g. A ~ 1. 25 close to 1 => N ~ (1/2, 0) + (1, 1/2) • There could be N* of g. A < 0 • Masses of chiral partners degenerate as symmetry recovers BUT we need more studies to clarify the role of chiral symmetry Nov. 30 - Dec. 2, 2005 J-PARC workshop, KEK 15

Pentaquarks Nov. 30 - Dec. 2, 2005 J-PARC workshop, KEK 16

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 + Q+-confined NK-scattering Compute phase shifts qq Nov. 30 - Dec. 2, 2005 J-PARC workshop, KEK qq 17

Hamiltonian NR quark model of Isgur-Karl Nov. 30 - Dec. 2, 2005 J-PARC workshop, KEK 18

KN-phase shifts 1/2+ Eres ~ 530 Me. V Gres ~ 110 Me. V • Mass is too high • Strong qs correlation –> JW configuration is suppressed Diquark formation is a dynamical problem Nov. 30 - Dec. 2, 2005 J-PARC workshop, KEK 19

Production Nov. 30 - Dec. 2, 2005 J-PARC workshop, KEK 20

g n -> n K+ K– J-Lab g p –> n K+ K 0 g d --> K+ K- p (n) ? g 10 Pre lim ina CLAS g 11 g d -> K+ K– p n ry LEPS Nov. 30 - Dec. 2, 2005 J-PARC workshop, KEK 21

LEPS has observed but CLAS does not Observation 1 LEPS: forward angle region CLAS: side Beam line LEPS J-Lab Nov. 30 - Dec. 2, 2005 J-PARC workshop, KEK 22

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 Nov. 30 - Dec. 2, 2005 J-PARC workshop, KEK 23

Effective Lagrangian approach u s t contact present only for charge exchange n –> Q+ or p –> L(1520) Nov. 30 - Dec. 2, 2005 J-PARC workshop, KEK 24

Before the Q-production gn -> K– L(1520) and gp -> K 0 L(1520) was studied and large pn asymmetry was known to us Nam-Hosaka-Kim, hep-ph/0503149 to appear PRD Energy dependence Nov. 30 - Dec. 2, 2005 J-PARC workshop, KEK t (or q) dependence 25

L(1520) JP = 3/2– g p –> K+ L(1520) Charge exchange L = 700 Me. V <=> r ~ 0. 8 fm Contact term • Large pn asymmetry • Strong forward peak • Polarization? ? Nov. 30 - Dec. 2, 2005 J-PARC workshop, KEK To be checked by experiments 26

For Q+ g n –> K– Q+ Charge exchange G = 1 Me. V, L = 700 Me. V <=> 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 Nov. 30 - Dec. 2, 2005 J-PARC workshop, KEK 27

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. Nov. 30 - Dec. 2, 2005 J-PARC workshop, KEK 28

Nov. 30 - Dec. 2, 2005 J-PARC workshop, KEK 29

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) Nov. 30 - Dec. 2, 2005 J-PARC workshop, KEK 30

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? Nov. 30 - Dec. 2, 2005 J-PARC workshop, KEK 31

Theta production, JP = 3/2 Log-scale Total s Nov. 30 - Dec. 2, 2005 neutron ~ forward peak Contact term Log-scale Angular dist proton ~ rather flat J-PARC workshop, KEK 32

Good for conventional baryons Mass Nov. 30 - Dec. 2, 2005 Magnetic moments J-PARC workshop, KEK Charge radii 33

LEPS: deuteron -> (Theta, L(1520)) L(1520) We need to understand g • Reaction mechanism 　　 Soft K? K Q MNK d N • Elementary process Q+, L(1520) production • Consistency between the J-Lab experiment Nov. 30 - Dec. 2, 2005 J-PARC workshop, KEK 34