1. Hadronic States with Large Multiquark Component
Bing-Song Zou
( Institute of High Energy Physics, CAS, Beijing )

2. SU(3) 3q-quark model for baryons 1/2 + spin-parity 3/2 +
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) -
1232
1385
1530
1672
Successful for spatial
ground states !
Prediction m- 1670 MeV experiment m- 0.29 MeV

3. An outstanding problem for the classical 3q model
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 - ~ L*(1405)
harmonic oscillator ( 2n + L + 3/2 ) hw
To understand the full baryon spectroscopy, it is crucial to
understand the lowest 1/2- baryon nonet and decuplet first !

4. Nature of N*(1535) and its 1/2- nonet partners`q
`q ½+
[ud]
}L=1 u d `q S
`q ½ -
[ud]
[us]
}L=0
Zhang et al, hep-ph/
N*(1535) ~ uud (L=1) + e [ud][us]`s + …
N*(1440) ~ uud (n=1) + x [ud][ud]`d + …
L*(1405) ~ uds (L=1) + e [ud][su]`u + …
N*(1535): [ud][us]`s  larger coupling to Nh, Nh’, Nf & KL, weaker to Np & KS, and heavier !
B.C. Liu, B.S. Zou, PRL96 (2006) ; PRL98 (2007)

5. The new picture for the 1/2- nonet predicts：
L* [us][ds]`s ~ MeV
S* [us][du]`d ~ MeV very different from
X* [us][ds]`u ~ MeV q model predictions
Capstick 3q model
Isgur 3q model

6. } SU(3) breaking } SU(3) allowed J/y decay branching ratio * 104
`p D(1232) / < 1
`S- S(1385)  0.5
`X+ X(1530)  1.5
`p N*(1535) /  3
`S- S(1360) ?
`X+ X(1520) ?
It is very important to check whether under the S(1385)
and X(1520) peaks there are 1/2 - components ?
Presumed 3/2 + Sc* and Xc* should also be checked.
} SU(3) breaking
} SU(3) allowed

7. Nature of D*(1620) and its 1/2- 10-plet partners
J.J.Xie, B.S.Zou, PLB649 (2007) 405
D*(1620)  ppN & ppnK+S+
extra-ordinary strong coupling of D*(1620) to rN
 D*(1620) ½ rN molecule ? MeV
S*(1750) ½ K*N molecule ? MeV
X*(1950) ½-? K*L molecule ? MeV
W*(2160) ½-? K*X molecule ? MeV
1/2- baryon decuplet ~ V8B8 molecules ?

8. `qqqqq in S-state seems more favorable
Conclusion
`qqqqq in S-state seems more favorable
than qqq with L=1 !
1/2- baryon nonet ~`qq2q2 state + …
1/2- baryon decuplet ~ V8B8 molecules + …

9. Similar problem for the lowest excited mesons
`qq 3P0 or `q2q2 nonet ?
f0(980) `ss , [`u`s ] [us] + [`d`s ] [ds]
k(800) `sd , [`s`u ] [ud ]
f0(600) `uu +`dd , [`u`d ] [ud]
a0(980) `uu -`dd , [`u`s ] [us] - [`d`s] [ds]
w(782) `uu +`dd
r(770) `uu -`dd
K(892) `sd
f(1020) `ss
`qq 3S1 nonet
D*s0(2317) ~`sc (L=1) + [`q`s ] [q c] + DK + …
D*s1(2460) ~`sc (L=1) + D*K + …
X(3872) ~`cc (L=1) + [`q`c ] [q c] + D*D + …

10. A possible way to distinguish the nature of a0/f0
a0(980)-f0(980) mixing

11. No firm direct observation of a0-f0 mixing available !
Estimations from relevant
measured parameters
Model predictions
`KK
`q2q2
`qq
For a very recent prediction from chiral unitary approach,
cf. Hanhart, Kubis & Pelaez, arXiv:  
No firm direct observation of a0-f0 mixing available !

12. 109 J/y events with BES3 detector +
J.J.Wu, Q.Zhao & B.S.Zou, PRD75(2007) :
109 J/y events with BES3 detector +
BR(J/y  f f0  f a0  f hp ) ~ (2-20)*10-6
narrow 8 MeV peak ( – ) MeV
Clear & precise determination of a0-f0 mixing !

13. J/y  fhp
a0-f0 mixing
BG contributions
BR: a0-f0 mixing ~ (2-20)*10-6 , g* ~ 2.6*10-7 , K*K ~ ( )*10-6

14. The lowest L=1 light hadronic states have
Conclusion
`q`q q q in S-state seems more favorable
than`qq with L=1 !
The lowest L=1 light hadronic states have
large multi-quark component .
How about higher excited states ?
Thank you !

16.  `d –`u ~ 0.12 Evidence for components other than 3q in the proton
Deep Inelastic Scattering (DIS) + Drell-Yan (DY) process
 `d –`u ~ 0.12
Garvey&Peng, Prog. Part. Nucl. Phys.47, 203 (2001)
Meson cloud picture: Thomas, Speth, Weise, Oset, Brodsky, Ma, …
| p > ~ | uud > + e1 | n ( udd ) p+ (`du ) >
+ e2 | D++ ( uuu ) p- (`ud ) > + e’ | L (uds) K+ (`su ) > …
Penta-quark picture : Riska, Zou, Zhu, …
| p > ~ | uud > + e1 | [ud][ud]`d > + e’ | [ud][us]`s > + …

17. Strange properties of N*(1535)
From relative branching ratios of
J/y  p`N*  p (K-`L) / p (`ph)
gN*KL /gN*ph /gN*Np ~ 2 : 2 : 1
B.C. Liu, B.S. Zou, PRL96 (2006) ; PRL98 (2007)
Evidence for large gN*Nh’ from g p  p h’
M.Dugger et al., PRL96 (2006)

18. BES Collaboration, H. B. Li, B. S. Zou, H. C. Chiang, G. X. Peng, J. X
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

19. N*(1535) in J/y  p K-`L + c.c. Nx Nx Events/10MeV Nx
(Arbitrary normalization)
PS, eff. corrected Nx
BES, Int. J. Mod. Phys. A20 (2005)

20. Evidence for large gN*KL from pp  p K+ L
Total cross section and theoretical results with
N*(1535), N*(1650), N*(1710), N*(1720)
B.C.Liu, B.S.Zou, Phys. Rev. Lett. 96 (2006)
pp  p K+ L
Tsushima,Sibirtsev,Thomas, PRC59 (1999) 369, without including N*(1535)

21. FSI vs N*(1535) contribution in pp  p K+ L
B.C.Liu & B.S.Zou, Phys. Rev. Lett. 98 (2007) (reply)
A.Sibirtsev et al., Phys. Rev. Lett. 98 (2007) (comment)
COSY-TOF data
S. Abdel-Samad et al., Phys.Lett.B632:27(2006)
FSI
N*(1650) etc.
Both FSI & N*(1535)
are needed !

22. Evidence for large gN*KL from g p  K+ L
B. Julia-Diaz, B. Saghai, T.-S.H. Lee, F. Tabakin, Phys. Rev. C 73, (2006)

23. G.Penner&U.Mosel,
PRC66 (2002)
Partial wave decomposition
For the fit to SAPHIR92-94
Data
Dashed line : /2 -
Dot-dashed line : 3/2+
Shklyar,Lenske&Mosel,
PRC72 (2005)

24. Evidence for large gN*Nf from p- p  nf & pp  ppf
Xie, Zou & Chiang, arXiv:
pp  ppf
r-ex
h-ex
p-ex
with FSI
no FSI
p- p  nf
Evasion of OZI rule by N*(1535) !

25. Evidence for small gN*KS from pp  p K+L /pp  p K+S0
A.Sibirtsev et al.,
EPJA29 (2006) 363
[2] P.Kowina et al., EPJA22 (2004) 293

26. Pentaquark vs Meson Cloud
Weise, Oset et al: N*(1535) as K L-KS state, L*(1405) as KN state `S u S d u d `S S
Pentaquark vs Meson Cloud
More solid information on its coupling to KS
and its 1/2- octet partner are needed !

27. Role of D++*(1620) in ppnK+S+
J.J.Xie, B.S.Zou, PLB649 (2007) 405
Why D++* ?
uuu -- the most experimentally accessible system
with 3 identical valence quarks
-- suggested the color degree of freedom in 1960s
Why D++* (1620) ?
JP = ½ The lowest excited uuu state with L=1
in classical 3q models

28. Our present knowledge on D++* resonances
Why ppnK+S+ ?
Our present knowledge on D++* resonances
mainly comes from p+p experiments
and is still very poor.
D*++ p
p +, r + n S+ K+
ppnK+S D++* production from r+p
-- accessible at COSY and CSR

29. Status on the study of ppnK+S+
-- New COSY-11 data
Resonance model
Incohenrent p/K exchange model also fails to reproduce these data

30. Our calculation for ppnK+S+
D*++(1920) with p+ exchange
D*++(1620) with r+ exchange
D*++(1620) with p+
t-channel r-exchange plays important role !