Pentaquark Theta+

5-quark states in a chiral
potential Atsushi Hosaka (RCNP)
Structure of a Pentaquark baryon
sss
+
Q
ssu
sdu
suu
uuu
ssd
uud
sdd
udd
ddd
JPS meeting Miyazaki, Sept 2003
JPS meeting Miyazaki, Sept 2003
Experiment
at LEPS
Quantum numbers

n  K Q 
 K  n,
K0p
B 1, Q 1, S  1, I3  0
At least 4 quarks + 1 antiquark => Purely exotic

Quark content => ud ud s
Unknoswn quantum numbers


J 1 / 2, 3 / 2, 5 / 2 ?
I  0, 1, 2 ?
P  ,  ?
Theta production at LEPS
JPS meeting Miyazaki, Sept 2003
picture
JPS meeting Miyazaki, Sept 2003
Quark model
Flavor structure
_


3  3  3  3  3 ~ 1, 8, 10, 10, 27, 35

_ 
3  3  3 ~ 10
Q
SSs


S ~ [ ud]
U ~ [ ds]
D ~ [ su]

1 
SS u  U S s  SUs 
3
1 
SU u  UU s  US u 
3
UU u

p
n
10
10
-
10
--
10
+
10
10
0

-
10

10
 DDd
 10
JPS meeting Miyazaki, Sept 2003
Masses
Parity
Sum of constituent quarks
M Q  5m  
~ 1730 MeV
4
M N *  5m   ~ 1790 MeV
3
5
M  *  5m   ~ 1850 MeV
3
M  *  5m  2 ~ 1910 MeV
p
udud s
Negative
JPS meeting Miyazaki, Sept 2003
KN Bound state approach of Skyrmion
S-wave bound state => Negative parity
P-wave bound state => Positive parity
s
Q (1540)
(1405)
P
WZ



0
(1116) 
P-orbit
JPS meeting Miyazaki, Sept 2003
Chiral soliton
Diakonov et al (1997)
Assumptions:
• Large-Nc => Skyrme soliton (hedgehog)
• SU(3) collective motion in flavor space
Rotation of a hedgehog in
SU(3) flavor space
JPS meeting Miyazaki, Sept 2003
Predictions
 10
Flavor 10, Isospin I = 0
Relatively small M(Q+)
Spin parity J = 1/2
10
N10
Q
+
and small width ~ 15 MeV
 10
N10
Q
Wider splitting
P
 10
 10
quark model
Chiral soliton
JPS meeting Miyazaki, Sept 2003
Chiral popential
4
2
-
+
(1 )
Chiral bag model
Hosaka Toki, Phys Rep ‘96
1
+
2
(1 - )
1
-
+
0
0
Hedgehog
Chiral
MIT
K  J I
Grand angular momentum
-2
0.0
0.2
0.4
0.6
0.8
Chiral angle -F/ 
1.0
JPS meeting Miyazaki, Sept 2003
st interaction
Hedgehog corraltion
Spin-isospin splitting
K 1
J  I  1/ 2
K0
u, d, u, d

c2  0

JPS meeting Miyazaki, Sept 2003
Chiral bag
3
2
1
-
-
s
(0  ) 3 (1 )(1/ 2 )
2
1
Negative parity
K  1/ 2 or 3 / 2

h
0
(0  ) 3 (1 )(1/ 2 )
Positive parity
h
h

I0
J  1/ 2 or 3 / 2
h
+
0

+
0.0
0.2
0.4
0.6
0.8
Chiral angle F(R)/
1.0
Theory and exp
Const. quark model
Chiral soliton: Collective quant.
Skyrmion bound state
Chiral bag
Diquark
Sum rule
Lattice
Gamma + n, p, d ->
K+ + n, p, d ->
pp ->
JPS meeting Miyazaki, Sept 2003
What more?
1. Spin and parity
P  , J  1/ 2, 3 / 2

 

n

K
Q
(1)
total cross sections
(2) K  p   K  n
polarization
2. Internal structure of 5quarks


Diquark correlation
Chiral interaction
3. Other bound states of many quarks

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