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Strangeness in the Proton and N*(1535)

Bing-Song ZouInstitute of High Energy Physics Be

ijing

Collaborators: D.O.Riska, C.S.An, B.C.Liu

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Outline

1. Introduction 2. Strangeness in the proton 3. Strangeness in N*(1535) and its ½- partners4. Summary

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1. Introduction

SU(3) 3q-quark model for baryonsSU(3) 3q-quark model for baryons

1/2 + spin-parity 3/2+1/2 + spin-parity 3/2+

Prediction m- 1670 MeV experim

ent m- 1672.45 0.29 MeV

s

I3

n(udd)

p(uud)

-(dds)

0 (uds) 0

+ (uus)

-(dss) 0(uss) (sss)

△0 △- △+ △++

0*- *+

(ddd) (udd) (uud) (uuu)

(dds) (uds) (uus)

*- *0

(uss)(dss)

-

Successful for spatialground states !

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Outstanding problems for the classical 3q model

• Mass order reverse problem for the lowest excited baryons Mass order reverse problem for the lowest excited baryons

uud (L=1) ½ - ~ N*(1535) should be the lowest uud (n=1) ½ + ~ N*(1440) uds (L=1) ½ - ~ *(1405)

harmonic oscillator ( 2n + L + 3/2 ) hharmonic oscillator ( 2n + L + 3/2 ) h

• The number of observed states is much less than predictedThe number of observed states is much less than predicted ““missing” baryon states : missing” baryon states : non-existence / to be observednon-existence / to be observed ? ?

• Flavor asymmetry of light quarks in the proton

d –u ~ 0.12 Garvey&Peng, Prog. Part. Nucl. Phys.47, 203 (2001)

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What are effective degrees of freedom ?

(a) 3q (b) hybrid (c) diquark (d) meson-cloud

Meson cloud picture: Thomas, Speth, Weise, Oset, Brodsky, Ma, … | p > ~ | uud > + | n ( udd ) + (du ) > + | ++ ( uuu ) - (ud ) > + ’ | (uds) K+ (su ) > …

d >u , s / s asymmetry N*(1535) as K -K state, *(1405) as KN state

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2. Strangeness in the proton

N term, large OZI violating production frompp annihilations

See reviews by Ellis, Beck, …

Question remained : symmetricss fluctuation from sea ?

neutrino DIS sizable charm production (NuTeV)

,Longitudinal momentum

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s / s asymmetry meson cloud model :

| p > ~ | uud > + | n ( udd ) + (du ) > + | ++ ( uuu ) - (ud ) > + ’ | (uds) K+ (su ) > + …

Predictions for the proton: • Strange spin : s < 0• Strange magnetic moment : s < 0

• Strange radii : rs < 0

The most recent analysis of data for strange spin s = -0.05 ~ -0.1 D. de Florian et al., Phys. Rev. D71 (2005) 094018

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Models - a non-exhaustive list for s and rs :

kaon loops, vector dominance, Skyrme model, chiral quark model, dispersion relations, NJL model, quark-meson coupling model, chiral bag model, HBChPT, chiral hyperbag, QCD equalities, Heavy quark, …

e.g., Geiger & Isgur, PRD55, 299 (1997) : K* cloud => s > 0

Carvalho-Navarra-Nielsen, PRC72, 068202 (2005)

Some recent theoretical attempts with closer relation to QCD :

D. Leinweber et al., Phys. Rev. Lett. 94, 212001 (2005) Negative s

X. D. Ji, D.Toublan, hep-ph/0605055 Positive s possibly

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The strange magnetic moment s and radii rs from parity violating electron scattering

G0,HAPPEX/CEBAF, SAMPLE/MIT-Bates, A4/MAMI

HAPPEX/CEBAF, Phys.Rev.Lett. 96 (2006) 022003 G0/CEBAF, Phys.Rev.Lett. 95 (2005) 092001 A4/MAMI, Phys.Rev.Lett. 94 (2005) 152001SAMPLE/MIT-Bates: Phys.Lett.B583 (2004) 79

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Theory vs experiment for s and rs

Our results

Zou&Riska, PRL95(2005)072001; Riska&Zou, PLB636 (2006) 265An-Riska-Zou, PRC73 (2006) 035207

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B.S.Zou, D.O.Riska, Phys. Rev. Lett. 95 (2005) 072001

New picture for strangeness in the proton:

s in S-state, uuds in [31]x[22]F[22]S = 1/4 s in P-state

including diquark configurations [su][ud]

instead of meson cloud (uds) K+ (su ) !

| p > ~ | uud > + [ud][ud]d > + | [ud][us]s > + …

Su

uS

d

u

du

SS

Diquark-cluster vs Meson Cloud

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Strange magnetic form factor Riska & Zou, PLB636 (2006) 265

s s

important & ss compact, radius ~ 0.2fm

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Baryon spectroscopy from J/ decays at BES/BEPC

Ideal isospin filter

**,*,*,/ NBMBJ

3. Strangeness in N*(1535) and its ½- partners

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invariant mass / MC phase spaceBES, Phys. Rev. Lett. 97 (2006) 062001 “Observation of two new N* peaks …”

/J p n /J p n vs

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The nature of the lowest ½- resonance N*(1535)

BES Collaboration, H.B.Li, B.S.Zou, H.C.Chiang, G.X.Peng, J.X.Wang, J.J.Zhu, Phys. Lett. B510 (2001) 75

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N*(1535) in J/p K-+ c.c.

)(GeV/c2KΛM

Eve

nts/

10M

eV

Nx

Nx

Nx

)(GeV/c2 MMM KKΛ

PS, eff. corrected

(Arbitrary normalization)

BES, Int. J. Mod. Phys. A20 (2005)

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B.C.Liu, B.S.Zou, Phys. Rev. Lett. 96 (2006) 042002

From relative branching ratios of J/pN* p (K-p (p

gN*K/gN*p/gN*p~ (1.3+0.3) : 1 : 0.6

Smaller N*(1535) BW mass

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(1)

(2)

(3)

Mass of N*(1535)

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Total cross section and theoretical results with N*(1535), N*(1650), N*(1710), N*(1720)

pp p K+

Tsushima,Sibirtsev,Thomas, PRC59 (1999) 369, without including N*(1535)

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A.Zhang, Y. Liu, P. Huang, W. Deng, X.Chen, S.L. Zhu, hep-ph/0403210 :

1/2- and 1/2+ octet N* pentaquarks have similar masses in Jaffe-Wilczek diquark model

N*(1535) ~ uud (L=1) + [ud][us]s + …

N*(1440) ~ uud (n=1) + [ud][ud]d + …

*(1405) ~ uds (L=1) + [ud][su]u + …

Larger [ud][us]s component in N*(1535) makes it coupling stronger to N & K, weaker to N & K and heavier ! B.C.Liu, B.S.Zou, PRL 96(2006)042002

ud

du

q

u

du

qSq ½+

[ud][ud]}L=1

q ½ -[ud][us] }L=0

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The new picture for the ½ - octet predicts ：* [us][ds]s ~ 1575 MeV* [us][du]d ~ 1360 MeV* [us][ds]u ~ 1520 MeV

*

*

M*(1570) ½- ?H.X.Yang, Ph.D thesis (IHEP,2001)

*(1360)1/2- ?

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J/ decay branching ratio * 104

p

p N*(1535) 1/2- 10

It is very important to check whether under the and peaks there are ½- components ?

} SU(3) breaking

} SU(3) allowed

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(ssq) - Baryon Spectroscopy *

Theory is totally not challenged due to lack of data !

Capstick&IsgurPRD34(1986)2809

BESIII@BEPC2 & Kaon@JPARC

Zhu S L’s predictionof pentaquark state

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4. Summary

• Predictions for the strangeness in the proton: meson cloud : s < 0 , s < 0 , rs < 0 diquark cluster : s < 0 , s > 0 , rs > 0• 5-quark components in baryons are important• The diquark cluster picture reproduces naturally the mass pattern for N*(1535) ,N*(1440), *(1405)

and the strange decay pattern of N*(1535)

• Predictions of the diquark cluster picture for N*(1535)’s ½- can be checked by BES, JPARC, CLAS, …

ex. : p -> K *(1360) with *(1360) ->