Hyperons analogous to L(1405)

5th APFB ConferenceAugust 22-26, 2011, Seoul, Korea

Hyperons analogous to Hyperons analogous to

Yongseok Oh(Kyungpook National University,

Korea)

2011-08-23 APFB 2011, Seoul, Korea 2

Overview

1. Introduction2. Bound state approach to the Skyrme model3. Outlook

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• Hyperon spectrum– Completeness of the observed hyperon resonances– Theoretical models for hyperon structure– Structure of (1405)

• uds• Five quark• K-bar N bound state

- baryon analogous to (1405)?

1. Introduction

PDG

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spectrum

Cf. spin of W- (=3/2) was confirmed only recently by BaBar, PRL 97 (2006)

P is not directly measured

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Experiments on multi-strangeness

PDG 2008

No meaningful information on spectrum

Open a new window for studying baryon structure

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Questions

The 3rd lowest state

CLAS: PRC 76 (2007)Babar: JP of (1690) is 1/2 PRD78

(2008)

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Summary

QM (Pervin, Roberts)132518912014

PRC 75

15201934202017251811

17591826

1820 (expt.)

1320 (expt.)

1530 (expt.)

: the 3rd lowest stateExpt: (1620)*, (1690)***

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Highly model-dependent !

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2. Bound state approach to the Skyrme model

bound kaon

SU(3) is badly broken

Treat light flavors and strangenesson the different footing

L = LSU(2) + LK/K*

Soliton provides background potentialwhich traps K/K* (or heavy) meson

Bound state approach(Callan, Klebanov)

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Bound state model

270 MeV energy difference

• Includes parameters• They should be computed with a given Lagrangian

(dynamics).• Or fix them to known masses and then predict.

Mass formula

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Some details

Other approaches

Kaons: one in p-wave and one in s-waveJ=Jsol + Jm (Jm = J1 + J2)

Jsol: soliton spin (=1/2), J1(J2): spin of the p(s)-wave kaon (=1/2)

Jm = 0 and 1: both of them can lead to JP = 1/2- states Therefore, two JP = 1/2- states and one JP = 3/2- stateIn this model, it is natural to have two JP = 1/2- states and their masses are close to each other.

Clearly, different from quark modelsUnitarized extension of chiral perturbation theory Ramos, Oset, Benhold PRL 89 (2002) 1/2- state at 1606 MeV Garxia-Recio, Lutz, Nieves, PLB 582 (2004) (1620) and (1690) are 1/2- states

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Hyperon spectrum

289 MeV

290 MeV

285 MeV positive parity

negative parity

parity undetermined

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Hyperon spectrum

YO, PRD 75 (2007)

spin-parity

Recently confirmed by COSY

PRL 96 (2006)

High precision experiments are required!

’s would be discovered in future.

Babar: JP of (1690) is 1/2-PRD 78 (2008)

NRQM predicts 1/2+

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Outlook

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• Similar mass splitting between parity partners– c(1/2+): 2286 MeV, c(1/2-): 2595 MeV– The mass difference between the two = 309 MeV– Potential is almost flavor-blind but gives richer spectrum

forheavy-quark baryons

– More analyses are needed

Heavy quark baryons