Hadron spectroscopy Pentaquarks and baryon resonances

Nov. 30 - Dec. 2, 2005

J-PARC workshop, KEK 1

Hadron spectroscopy Pentaquarks and baryon resonances

Atsushi Hosaka, RCNP Osaka Univ.

• Baryon resonances Quark model description (deformed oscillator) KN for(1405) ~ importance of qq correlation qq vs qq Chiral symmetry

• Pentaquarks Full 5-body calculation ~ qq Production of + ~ consistency of J-Lab and LEPS

Nov. 30 - Dec. 2, 2005


At low energiesLattice 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

Nov. 30 - Dec. 2, 2005


Simple setups:

• SU(6) and small ms breaking • Harmonic oscillator potential, V(r) = kr2

• Effective residual interaction Gluons, Chiral mesons, instantons, …

Let us start with Quark model

To test the quark model, let us see baryon states

Nov. 30 - Dec. 2, 2005


Light flavor (uds) baryons

Well established states

49 ***,**** states out of 5013 * , ** states out of 31

62 states out of 81 states

2500

2000

1500

1000

N Σ Δ Ξ

But if we rearrange

Nov. 30 - Dec. 2, 2005


Positive parity baryons

2000

1500

1000

500

028 S

28 S28 S

410 S410S

N Σ Δ

P11 (1440)

F15 (1680)

P13 (1720)

H19 (2220)

P11 (1710)P01 (1600)

F05 (1820)

P03 (1890)

H09 (2350)

P01 (1810)

F05 (2110)

P11 (1660)

F15 (1915)

*P13 (1840)

F17 (2030)

*F15 (2070)

**P13 (2080)

P33 (1600)

F37 (1950)

F35 (1905)

P33 (1920)

P31 (1910)

H311 (2420)

P11 (939) P01 (1116) P11 (1189) P13 (1385) P33 (1232)

=0

=0

=2

=4

** P13 (1900)

** F17 (1990)

** F15 (2000)

*F07 (2020)

** F37 (2390)

** P11 (1880)

8MΣ 8 MΣ28 MΣ

• Measured from the ground state • 8MS states are shifted downward by 200 MeV

Nov. 30 - Dec. 2, 2005


Negative parity baryons

• Measured from the 1/2+ ground state • 48MS states are shifted downward by 200 MeV

Nov. 30 - Dec. 2, 2005


Deformed Oscillator Model

• Ground state: spherical • Excited states:

Single particle excitation deforms the confining potential Deformed states rotate collectively => Resonances as collectively rotated states

Takayama-Toki-HosakaProg.Theor.Phys.101:1271-1283,1999

Nov. 30 - Dec. 2, 2005


It seems that we make a good job

Important questions:

BUT: Is this the end of the story???

Roper as a diquark states => Nagata • Quark correlations qq or qq

• Also qqq* states can mix with qqq(qq)

L(1520) as a KN state => Hyodo

• Chiral symmetry

Nov. 30 - Dec. 2, 2005


Role of qq (meson)correlation

Long time being said, but renewed interests due to chiral perturbation and its unitarization

Interaction Resonance

Basic assumptions: Ground state hadrons as building blocks: B and M Contact MB interaction dominates the s-wave dynamics

L Tomozawa-Weinberg

Meson clouds

Nov. 30 - Dec. 2, 2005


(1405)

Two poles near Mass ~ 1405

Σ ->Σ ->Σ

1426 + 16i (KN)

1390 + 66i (Σ)

K–p –> Σ, Magas-Oset-Ramos, Phys.Rev.Lett.95:052301,2005

Jido-Oller-Oset-Ramos-Meissner, Nucl.Phys.A725:181-200,2003: nucl-th/0303062

The state is crucially important for the K-nuclei

KN ~ 8 x 8 = 1, 8, 8, 10, 10, 27attractive repulsive

Nov. 30 - Dec. 2, 2005


In the quark language

qq-correlation vs. qq-correlation

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

qq correlation is equally or more important than qqfor equal masses. If m>>m, then qq is suppressed

To see qq correlations, heavy quark systems may be suited

€

VCS = −ij∑ k

mim j

λa (i)2

λa ( j)2

r σ (i) ⋅ r

σ ( j)

Nov. 30 - Dec. 2, 2005


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


They are related to:

How far our world is from the symmetric worldHow strongly chiral symmetry is broken

Large f , mSmall f , m

Nov. 30 - Dec. 2, 2005


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), ….

Mesons: (0, 0), (1/2, 1/2), (1, 0), …

• For baryons, chiral partners can be made by Particles of the same parity (N, Δ, 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

with mixings

, a1

N N, Δ, Δ,

Nov. 30 - Dec. 2, 2005


• gA ~ 1.25 close to 1 => N ~ (1/2, 0) + (1, 1/2)

• Masses of chiral partners degenerate as symmetry recovers

€

MN

€

q q = 0

€

q q ≠ 0

€

MN *

• There could be N* of gA < 0

BUT we need morestudies to clarify the role of chiral symmetry

Nov. 30 - Dec. 2, 2005


Pentaquarks

Nov. 30 - Dec. 2, 2005


Most serious calculation for 5-body system with scattering states included Gaussian expansion method

+-confined NK-scattering

+

Compute phase shifts

qq qq

5-body calculation for +

Hiyama et al, hep-ph/0507105

Nov. 30 - Dec. 2, 2005


NR quark model of Isgur-Karl

Hamiltonian

Nov. 30 - Dec. 2, 2005


Eres ~ 530 MeVres ~ 110 MeV

• Mass is too high • Strong qs correlation –> JW configuration is suppre

ssed

Diquark formation is a dynamical problem

KN-phase shifts 1/2+

Nov. 30 - Dec. 2, 2005


Production

Nov. 30 - Dec. 2, 2005


J-Lab

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Ç™Ç±ÇÃÉsÉNÉ`ÉÉÇ å©ÇÈÇΩÇflÇ…ÇÕïKóvÇ≈Ç∑ÅB

p –> n K+ K0

CLAS g11

Preli

minaryg10

d --> K+ K- p (n)

?

LEPS n -> n K+ K– d -> K+ K– p n

Nov. 30 - Dec. 2, 2005


J-Lab

LEPSBeam line

LEPS: forward angle regionCLAS: side

LEPS has observed but CLAS does not

Observation 1

Nov. 30 - Dec. 2, 2005


• Large p, n asymmetry

(Charge exchange) >> (Charge non-exchange)

Nam-Hosaka-Kim, hep-ph/0503149, PRD, 71:114012,2005 hep-ph/0505134

Observation 2

• Strongly forward peaking

Nov. 30 - Dec. 2, 2005


present only for charge exchange

Effective Lagrangian approach

s u

tcontact

n –> + or p –> (1520)

Nov. 30 - Dec. 2, 2005


n -> K– (1520) and p -> K0 (1520)

was studied and large pn asymmetry was known to usNam-Hosaka-Kim, hep-ph/0503149 to appear PRD

Energy dependence

Before the -production

t (or ) dependence

Nov. 30 - Dec. 2, 2005


Contact term • Large pn asymmetry • Strong forward peak • Polarization??

= 700 MeV <=> r ~ 0.8 fm

To be checked byexperiments

(1520) JP = 3/2–

p –> K+ (1520) Charge exchange

Nov. 30 - Dec. 2, 2005


• Large pn asymmetry • If + is larger in size,

may be smaller and strongly forward peaking• ~ few nb or less -> consistent with the CLAS result

=1MeV= 700 MeV <=> r ~ 0.8 fm

The total cross section is very sensitive to

For + n –> K– + Charge exchange

Nov. 30 - Dec. 2, 2005


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


Nov. 30 - Dec. 2, 2005


Why hadrons?

• 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)

Everybody knows that:

Nov. 30 - Dec. 2, 2005


But not so easyDue to non-perturbative dynamicsColor 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


Total

Angular dist

Log-

scal

e

neutron ~ forward peak Contact term

proton ~ rather flatLog-

scal

e

Theta production, JP = 3/2

Nov. 30 - Dec. 2, 2005


Mass Magnetic moments Charge radii

Good for conventional baryons

Nov. 30 - Dec. 2, 2005


LEPS: deuteron -> (Theta, L(1520))

• Reaction mechanism　　 Soft K?

We need to understand

d

(1520)

K

NMNK

• Elementary process +, (1520) production

• Consistency between the J-Lab experiment

Documents

Hadron spectroscopy Pentaquarks and baryon resonances