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New Results on Hadron Spectroscopy(Experimental Review)
Shan JINInstitute of High Energy Physics (IHEP)
Chinese Academy of Sciences
August 20, 2004
ICHEP 2004, Beijing
Multi-quark State, Glueball and Hybrid
Hadrons consist of 2 or 3 quarks ：
Naive Quark Model ：
New forms of hadrons:• Multi-quark states ： Number of quarks > ＝ 4 • Hybrids ： qqg ， qqqg …
• Glueballs ： gg ， ggg …
Meson （ q q ）
Baryon （ q q q ）
Multi-quark states, glueballs and hybrids have been searched for experimentally for a very long time, but none is established.
However, during the past one year, a lot of surprising experimental evidences showed the existence of hadrons that cannot (easily) be explained in the conventional quark model.
There are so many exciting unexpected new observations as well as many negative search results that I will not be able to cover many “conventional” topics, such as charm baryons, charmonium production…
I would deeply apologize to those experiments who contribute these beautiful results to the conference.
Outline Multi-quark candidates:
• Pentaquarks
• X(3872)
• DsJ(2632)
• Resonant structures near mass thresholds and J/ mass thresholds.
Light scalar mesons:
• σ, κ, f0(980), f0(1370), f0(1500), f0(1710), f0(1790)
Other interesting results from BES and CLEO-c
Kpppp C ,,,
Observations of pentaquarks
Θ+(1540)
First evidence of pentaquark was presented by LEPS in the process :
Nevent= 19 +/- 2.8
Significance: ~ 4.6 σ
Minimum quark content: uudds
Its mass and width are consistent with chiral soliton model prediction.
MnK+
LEPSnKKn
MeV
MeVM
25
5101540
at 90% CL
)/( BS
CLAS
KpnKd
M(nK+)
2.5:~
43
21
51542
ceSignifican
N
MeV
MeVM
event
)/( BS
M(nK+)
CLAS
8.7:~
41
26
101555
ceSignifican
N
MeV
MeVM
event
)/( BS
KnKp
SAPHIR
0SKnKp
M(nK+)
8.4:
1363
25
241540
ceSignifican
N
MeV
MeVM
event
(fit)
3.0~))1520(*(/))1540(()1520(* R
M(pKs)
4~3~
6~4:~
60~
3917
231528
ceSignifican
N
MeV
MeVM
event
)/( BS
SS NN /
Inclusive γ*- production
HERMES
5.3~6.1~)1520(*R
Fragmentation ZEUS
6.4~9.3:~
48221
48
5.15.1521 8.27.1
ceSignifican
N
MeV
MeVM
event
(fit)
RΛ ~ 0.04
Assuming the production rate of Λ*(1520) is 5 times smaller than Λ, I estimated:
RΛ*(1520) ~ 0.2
M(pKs)
M(pKs)
Asratyan et al.- induced
7.6:~
27
20
51533
ceSignifican
N
MeV
MeVM
event
)/( BS
DIANA
)( 0
'0
pKnK
XepKXeK
M(pKs)
4.4:~
29
9
221539
ceSignifican
N
MeV
MeVM
event
)/( BS
XpKpA
SVD
S
0
2
b
ceSignifican
N
MeV
MeVM
event
120~30)(
6.5:~
50
24
331526
M(pKs)
)/( BS
0SpKpp
TOFCOSY
M(pKs)
b
ceSignifican
N
MeV
MeVM
event
1.01.04.0)(
9.5~7.3:~
120~
18
51530
Pentaquarks at JINR
How many pentaquarks did they see?
M(nK+)
(LEPS)
nK
MΘ
0SpK
0SpKnK
F. Close and Q. Zhao, hep-ph/0404075
ΓΘ
PDG 04:
(R.N. Cahn, G.H.Trilling, PR D69 011501R, based on the production cro
ss-section estimation from DIANA data, σR=ABiBfΓ)
Consistent with other estimation of the upper limit on the width based on K+N partial wave reanalysis
( < 1 MeV )
Why the width is so narrow seems very hard to understand.
MeV3.09.0
Isospin of Θ+(1540)
No Θ++ was observed by SAPHIR, HERMES or other experiments.
Θ+ is an isoscalar
Ξ--(1862)
Also evidence for Ξ0(1862)
( I = 3/2 )
NA49 )a
)b
)c
)d
)( M
ussdd
dssdu
dudss
uddss 8.5:~
69
18
21862
ceSignifican
N
MeV
MeVM
event
)/( BSS
)))) dcba
)( M
pp collision at Ecm=17.2GeV
Θc(3099)
Minimum quark content: uuddc
4.5:~
2.116.50
12
533099
ceSignifican
N
MeV
MeVM
event
DIS (Q2 > 1GeV2)
Poisson Prob.
01.0~))3099(()3099( pDBRN
Nc
D
c
Negative search results on pentaquarks
BES
Upper limits @ 90% C.L.
BR ( (2S) (KSp)(K-n) + (KSp)(K+n))< 0.84X10-5
BR ( J/ (KSp)(K-n) + (KSp)(K+n)) < 1.1 X10-5
(2S) J/
RΛ*(1520) < ?
ALEPH
No evidence for Θ+(1540), Ξ--(1862), Ξ0(1862) , Θc(3100)
in Z decays
M(pKs)
Also no evidence for Θ+(1540), Θ++(1540) at DELPHI
ALEPH Limits at 95% C.L.
018.0))3100((
0031.0))3100((
16.0))1862((
082.0))1862((
027.0))1535((
0)3100(
0)3100(
0
)1530(
)1862(
)1530(
)1862(
0
)1520(
)1535(
0
0
0
0
0
pDBRN
N
pDBRN
N
BRN
N
BRN
N
pKBRN
N
c
D
c
D
s
c
c
No evidence for Θ+(1540) in two photon collisions.
L3
CDF No evidence of Θ+(1540), Ξ--(1862), Ξ0(1862) or Θc(3100)
observed at CDF.
M(pKs)
Θc(3100)
Θ+(1540)
HERA-B
M(pKs)
)( M
)1540(
)1860(
No evidence of Θ+(1540), Ξ--(1862), Ξ0(1862) at HERA-B(proton-nucleus collisions at )GeVs 6.41
CLR %[email protected]~027.0)1520(*
CL
BR
%95@
04.0)1530(/)1862( 0
Θc(3099) was not observed at ZEUS in a data sample
which is 1.7 times of the H1 data sample.
M(D*p)
0035.0)(
pDBRN
Nc
D
c
95% C.L. upper limit:
Inconsistent with H1: ~0.01
ZEUS
More quantitative comparisonsrequire detector efficiency corrections.
BaBar
No evidence of Θ+(1540), Ξ--(1862) or other possible pentaquarks was observed at BaBar. Upper limits were set.
RΛ*(1520) < ~ 0.01
@ 90 % CL
003.0~)1530(/)1862( 0 BR
Belle
Belle did not see Θ+(1540):
RΛ*(1520) < 0.02
@ 90 % CL
Θc(3100) was not seen
either.
155fb-1
(1520)
nothing
m(GeV)
pK-
pKS
Inconsistencies (I)
Width of Θ+(1540)
• Two “positive” experiments:
HERMES: ΓΘ = 17 9 2 MeV
ZEUS: ΓΘ = 8 4 MeV
• K+N PWA results indicates ΓΘ < 1 MeV
Mass of Θ+(1540)
(LEPS)
nK
MΘ
0SpK
0SpKnK
Inconsistencies (II) Production rate (e.g. for Θ+(1540) )
• “Positive” experiments:
SAPHIR: RΛ*(1520) ~ 0.3
HERMES: RΛ*(1520) ~ 1.6~3.5
ZEUS: RΛ*(1520) ~ 0.2 ( I estimated from RΛ ~ 0.04 )
SVD-2: RΛ*(1520) > 0.2 ( estimated by SPHINX,
hep-ex/0407026)
• “Negative” experiments:
ALEPH: RΛ*(1520) < 0.1
BaBar: RΛ*(1520) < ~ 0.01 Belle: <0.02
HERA-B: RΛ*(1520) < 0.027~0.16
SPHINX: RΛ*(1520) < 0.02
The “negative” experiments have much larger statistics, also are at relatively higher energies (but Babar and Belle are at low energy).
• Pentaquarks do not exist, or• Pentaquarks have very exotic production me
chanism. via N*? Then why N* has much higher production rate at low energy?
Looking forward to more experimental results at low energy with high statistics, especially those photo-production experiments !
Comments on statistical significance
Using to estimate statistical significance seems too optimistic. Even if we have firm knowledge on the background CLb as LEP
Higgs used is recommended.
When the background is estimated from the fit of sideband, the likelihood ratio with D.O.F. taken into consideration is a better estimator of statistical significance.
• In this case, the uncertainty of all possible background shapes should be included in the uncertainty of significance.
Do not optimize/tune the cuts on the data! Determine the cuts based on MC optimization before looking at data.
• The sys. uncertainty on significance from “bias” cut is hard to estimate.
“Look elsewhere” effect may reduce the significance by 1~2σ.
BS /
X(3872)
First observed by Belle Experiments in:
M(J/) –M(J/)
’J/
X(3872) 10σeffect
Belle
MeV
MeVM
3.2
5.06.00.3872
at 90% C.L.
X(3872) at CDF and D0
5.2 effect
11.6 effect
MeVM X 4.07.03.3871 MeVMM JX 0.31.39.774/
X(3872) at BaBar
The significance is low (about 3.5 σ), but its production rate is consistent with Belle:
/JM
3.5 σ effect
510)41.028.1()/()(
4.14.3873
JXBXKBBR
MeVM X
510)3.03.1(: Belle
BaBar
No evidence of X is observed in B0 XK+, B XK0
s with X J/ - 0.
So, isovector hypothesis of X disfavored.
Search for B XK at BaBar
Mode B J/0K+
B J/0K0s
n obs. 87 31
n bkg. 101.8 ± 10.2 27.6 ± 6.2
n signal -14.8 ± 13.9 3.4 ± 8.3
90%CL < 5.8 x 10-6 < 11 x 10-6
CLEO – γγFusion and ISR
eVJXBX
eVJXBXJ
ee 0.8)/)3872(())3872((
9.12)/)3872(())3872(()12(
(90% C.L)
Consistent with Yuan et al. estimation from BES data: JPC=1- - disfavoured
New decay mode observed at Belle
Belle observed a new decay mode of X(3872) *J/ +-0J/
(XJ/)/(X J/) = 0.8 ±0.3± 0.1
M()
M(J
/
)
BK X(3872)
Nevt=10.0 ± 3.6Signif = 5.8
No other decay modes of X(3872) are observed
So far, it is only observed in J/ and *J/ modes.
90% C.L. upper limits (most from Belle):
Non-observation of DD modes suggests that JP=0+, 1-, 2+,…, is ruled out.
6)/(/)(
7)/(/)(
6.0)/(/)/(
40.0)/(/)/(
1.1)/(/)(
89.0)/(/)(
000
2
1
JXDDX
JXDDX
JXJX
JXJX
JXX
JXX
c
c
BaBar
Is X(3872) a Charmonium? All possible charmonium assignments seem to
have difficulties (S.L. Olsen, hep-ex/0407033):
State nickname JPC comment
13 D2 ψ2 2-- Mass wrong; Гγχc1 too small
21 P1 h’c 1+- Ruled out by |cosθJ/ψ| distribution
13 D3 ψ3 3-- Mass & width wrong; Гγχc2 too small; Spin is too high
23 P1 χ’c1 1++ ГγJ/ψ too small
11D2 ηc2 2-+ B(π+π- J/ψ ) expected to be very small
31 S0 η”c 0-+ Mass and width are wrong
DD* “Molecular State”? MX(3872) is very close to MD + MD*.
It was suggested that a DD* multi-quark “molecular state” have large BR(XD0D00). Belle observes:
Some theoretical calculations predict the above ratio is small. (Swanson’s talk in Session 10)
Swanson also predicts:
Consistent with Belle new observation.
6)/(/)( 000 JXDDX at 90% C.L.
6.0~)/(/)/( JXJX
DsJ(2632)
DsJ(2317) and DsJ(2460)
BaBar - DsJ(2317) CLEO Belle
DSJ(2317)
DSJ(2460)
DSJ(2317)
DSJ(2460)
DSJ(2460)
)( 0SDM
)( 0SDM
)( 0*SDM
0SD
0*SD
SD
KKDS
0 KKDS
)( sJDM
DSJ(2632) at SELEX
A narrow resonance was observed in mode.
Nevent = 45.0 9.3
The significance is about 7.2 σ using .
Probability of 6 bins region with > 100 events anywhere on this plot with background of 54.4+/-2.5:
3x10-6 ~4.6σ)( SDM
SD
BS /
(Talk given by P.S. Cooper at PIC 2004)
DsJ(2632)
DSJ(2632) was also observed in D0K+ mode.
Nevent = 14.0 4.5
The significance is about 5.3 σ (?) using .
)( 0 KDMBS /
Properties of DSJ(2632)
Mass: 2632.6 1.6 MeV ( above D(*) K threshold )
Narrow Width: < 17 MeV at 90% C.L.
Unusual decay pattern:
What is it?• First radial excitation of DS*(2112)?• A csg hybrid?• A tetraquark or molecular state? ( Y.Q. Chen and X.Q. Li, hep-ph/0407062; K.T. Chao, hep-ph/0407091;
T. Barnes et al., hep-ph/0407120; Y.R. Liu et al., hep-ph/0407157 … )
Next talk
06.016.0)(/)( 0 SDKD
DSJ(2632) search at CLEO
SELEX noted one-bin excess at 2636 MeV in CLEO 2.16 fb-1data.
However, CLEO did not observe a narrow peak around 2632 MeV in 20 fb-1 data.
DsJ(2632) ?
2s GeV/c η)m(D
DsJ(2632)+
Even
ts/1
0
MeV
/c2
DSJ(2632) search at BaBar
BaBar did not see DSJ(2632) in the same decay modes as SELEX in 125 fb-1 data.
DsJ(2632) B (DsJ(2632)) D0K) DsJ(2573) B(DsJ (2573)) D0K)
<1.2% @90%CL
Known state DsJ(2573) is clearly seen (N=7292164) but no sign of DsJ(2632) (N=-66 64)
DsJ(2632)
N/
2M
eV
D0K+ mass
Ds mode under study
cf. SELEX 56 27%
550 M(MeV) 850
SELEX
DSJ(2632) search at Belle
155fb-1Belle
Resonant structures near , KΛ mass thresholds
and J/ mass thresholds
cpppp ,,
Observation of an anomalous enhancement near the threshold of mass spectrum at BES II
M=1859 MeV/c2
< 30 MeV/c2 (90% CL)
J/pp
M(pp)-2mp (GeV)
0 0.1 0.2 0.3
3-body phase space acceptance
2/dof=56/56
acceptance weighted BW +3 +5
10 25
pp
BES II
With threshold kinematic contributions removed, there are very smooth threshold enhancements in elastic “matrix element” and very small enhancement in annihilation “matrix element”:
much weaker than what BES observed !
NO strong dynamical threshold enhancement in cross sections (at LEAR)
pp
pp
pmppM 2)(
|M|2 |M|2BES BES
elasticelasticM ~|| 2 annlabann PM ~|| 2
Both arbitrary normalization Both arbitrary normalization
Any inconsistency? NO!
For example: with Mres = 1859 MeV, Γ = 30 MeV, J=0, BR(ppbar) ~ 10%, an estimation based on:
At Ecm = 2mp + 6 MeV ( i.e., pLab = 150 MeV ), in elastic process, the resonant cross section is ~ 0.6 mb : much smaller than the continuum cross section ~ 94 20 mb .
Difficult to observe it in cross sections.
4/)(4
)(4
)12)(12(
)12(22
2
22
2
21
rescm
outin
pcmres mE
BB
mE
c
SS
J
pp
Why can it be seen in J/ decays, but not in cross sections?
Reason is simple:
J/ decays do not suffer large t-channel “background”. It is an s-channel effect !
pp
>>
p p p p
p
p p p p
p
/J
Final State Interaction ? —— Not favored
1. Theoretical calculation (Zou and Chiang, PRD69 034004 (2003)) shows: The enhancement caused by one-pion-exchange (OPE) FSI is too small to explain the BES structure.
2. The enhancement caused by Coulomb interaction is even smaller than one-pion-exchange FSI !
BES
one-pion-exchange FSI
|M|2 |M|2
Both arbitrary normalization
BES
pmppM 2)(
Both arbitrary normalization
Coulomb interaction
Final State Interaction ? —— Not favored
Theoretical calculation might be unreliable, however, according to Watson’s theorem, we can use elastic scattering experiments to check the FSI effect, i.e.,if the BES structure were from FSI, it should be the same as in elastic scattering: But it is NOT ! FSI cannot
explainthe BES structure.
/J
p
p
p p
p pelastic scattering
|M|2 BES
Both arbitrary normalization
elasticelasticM ~|| 2
pmppM 2)(
pp bound state (baryonium)?
+ n +
deuteron:
loosely bound 3-q 3-
q color singlets with Md = 2mp-
baryonium:
loosely bound
3-q 3-q color singlets with Mb = 2mp-
?
attractive nuclear force attractive force?
There is lots & lots of literature about this possibility
E. Fermi, C.N. Yang, Phys. Rev. 76, 1739 (1949)
…I.S. Sharpiro, Phys. Rept. 35, 129 (1978)C.B. Dover, M. Goldhaber, PRD 15, 1997 (1977)…A. Datta, P.J. O’Donnell, PLB 567, 273 (2003)]M.L. Yan et al., hep-ph/0405087
Observations of this structure in otherdecay modes are desirable.
Observation of an anomalous enhancement near the threshold of mass spectrum at BES IIp
BES II pKJ /
3-body phase space
For a S-wave BW fit: M = 2075 12 5 MeV Γ = 90 35 9 MeV
)(GeV/c2
ΛKM
PS, eff. corrected
MMM KΛK
Observation of a strong enhancement near the threshold of mass spectrum at BES IIK
(Arbitrary normalization)
BES II pKJ /
NX*
A strong enhancement is observed near the mass threshold of MK at BES II.
Preliminary PWA with various combinations of possible N* and Λ* in the fits —— The structure Nx*has:
Mass 1500~1650MeV
Width 70~110MeV
JP favors 1/2-
consistent with N*(1535)
The most important is:
It has large BR(J/ψ pNX*) BR(NX* KΛ) 2 X 10-4 ,
suggesting NX*has strong coupling to KΛ.indicating it could be a KΛ molecular state
(5 - quark system). cf: f0(980)
Fit with BW:
Observation of an anomalous enhancement near the threshold of mass spectrum at Bellecp
Belle cpB
2
202.003.0
/)04.004.009.0(
/)02.034.3(
cGeV
cGeVM
,,,, 00 pKpKpKc
If it is fit with a BW:
Significance: > 8
Observation of an anomalous enhancement near the threshold of J/ mass spectrum at Belle
Belle
BKJ/MeV
MeVM
2492
113941
Threshold Enhancements in J/ decays and B decays
They may come from different mechanism:
There is “fragmentation” mechanism in B decays but NOT in J/ decays.
KppB
Belle
BES II
ppJ /
“Threshold” enhancement in B decays is much wider and is not really at threshold. It can be explained by fragmentation mechanism.
Threshold enhancement in J/ decays is obviously much more narrow and just at threshold, and it cannot be explained by fragmentation mechanism.
Is the STRONG threshold enhancement universal in J/ decays ? —— NO !
Actually in many other cases we do NOT see STRONG threshold enhancements !
For example: In J/ decays at BES II
np J /
)( pM
)(KKMpmppM 2)(
KKJ /
)( pKM
pKJ /
0/ ppJ
Light Scalar Mesons:
σ, κ, f0(980), f0(1370),
f0(1500), f0(1710), f0(1790)
Why light scalar mesons are interesting?
There have been hot debates on the existence of σ and κ .
σ, κ and f0(980) are also possible mutiquark states. They are all near threshold.
Lattice QCD predicts the 0++ scalar glueball mass ~ 1.6 GeV. f0(1500) and f0(1710) are good candidates.
σ at BES BES II observed σ in J/ +-.
Pole position from PWA:
BES II
M
MeVi )42252()39541(
BES II observed in J/K*KKK.
Preliminary PWA result
Pole position:
κ at BES
BES IIPreliminary
MeVi )420~310()840~760(
Important parameters from PWA fit:
Large coupling with KK indicates big component in f0(980)
BES IIPreliminary
/J
KKJ /
f0(980) at BES
21.025.021.4
1510165
68965
g
g
MeVg
MeVM
KK
ss
f0(980)
f0(980)
f0(980) is observed in f0(980) at KLOE (Background: ISR, FSR and ).
The results support that f0(980) has large coupling with KK.
f0(980) at KLOE
KLOEPreliminary
f0(980) f0(980)
)(M )(M
Background subtracted
There has been some debate whether f0(1370) exist or not.
f0(1370) clearly seen in J/ , but not seen in J/ .
/J
BES IIPreliminary
/J
PWA 0++ components
f0(1370)
NO f0(1370)
f0(1370) at BES
MeV
MeVM
40265
501350
Clear f0(1710) peak in J/ KK.
No f0(1710) observed in J/ !
f0(1710) at BES
BES IIPreliminary
KKJ /
/J
f0(1710)
NO f0(1710)
MeV
MeVM
20125
301740
CLKKfBR
))1710((
))1710((
0
0
ZEUS observed a narrow peak around 1730 MeV in KSKS mode:
Its width is much narrower than BES and others. Spin-parity needed.
How many mesons in this mass range?
f0(1710) (?) at ZEUS
f0(1710) ???
MeV
MeVM201438
71726
A clear peak around 1790 MeV is observed in J/ .
No evident peak in J/ KK. If f0(1790) were the same as f0(1710), we would have:
Inconsistent with what we observed in J/ , KK
New f0(1790) at BES
BES IIPreliminary
/Jf0(1790)
KKJ /?
MeV
MeVM6030
4030
270
1790
5.1~))1710((
))1790((
0
0
KKfBR
fBR
CLKKfBR
))1710((
))1710((
0
0
f0(1790) is a new scalar !
Scalars in J/ , KK
Two scalars in J/ :
• One is around 1470 MeV, may be f0(1500)?
• The other is around 1765 MeV, is it f0(1790) or a mixture of f0(1710) and f0(1790)?
One scalar f0(1710) in J/ KK.
BES IIPreliminary
/J
?)1500(0f ?)1710(0f
)1710(0f
KKJ /
f0(1500) at BES
One scalar with a mass = 1466 6 16 MeV is needed in J/ , is it f0(1500)? Why the mass is different from PDG?
No peak directly seen in , KK, , KK.
OZI rule and flavor tagging in J/ hadronic decays
In J/ hadronic decays, an or Φ signal deter
mines the or component, respe
ctively. OZI rule
dduu ss
/J /J
dduu
ss
Unusual properties of f0(1370), f0(1710) and f0(1790)
f0(1710):
• It dominantly decays to KK (not to )
• It is mainly produced together with (not ) • What is it ?
f0(1370) and f0(1790)
• They dominantly decays to (not to KK) • It is mainly produced together with (not ) • What are they ?
Scalar Puzzle
dduu
dduu
ss
ss
Other interesting results from BES and CLEO-c
Possible new N*(2050) at BES II
N*(1440)?
N*(1520)
N*(1535)N*(1650)
N*(1675)
N*(1680)
?
MeV
MeVM
4012175
32065 1530
npJ /
BES IIPreliminary
decays and 12% rule test
Puzzle:Qh<<12%
VP• Most channels BRs are consistent.
• BES BR() > CLEO by ~ 3, because PWA takes into acount the interference.
• BR(K*0K0) are deviated
%12)/(
)'(
)/(
)'(
eeJB
eeB
XJB
XBQh
CLEO-c
hQ
Summary
Pentaquarks need confirmation, then we need to answer:• The exotic production mechanism of pentaquarks.• Why the widths are so narrow?• What are their JP ?
One new decay mode X(3872) *J/ is observed at Belle. We still need to:
• Find more decay modes of X(3872)
• Understand its nature: a charmonium or molecular state?
DsJ(2632) needs confirmation, then we need to understand its width and unusual decay properties, also its unusual production mechanism.
A unique very narrow threshold enhancement is observed in decays at BES II:• It is not observed in elastic cross section
it cannot be explained by FSI.
• It is obviously different from the structure observed in B decays and it cannot be explained by fragmentation.
We need to understand the nature of the strong anomalous baryon-antibaryon, baryon-meson threshold enhancements in J/ decays: multiquark states or other dynamical mechanism ? (keeping in mind that there are no strong threshold enhancements in many cases)
We need to understand the Scalar Puzzle: why many scalar mesons behave differently in the production and decay properties? We also need to answer: How will the new observed f0(1790) change the scalar glueball picture?
pp
ppppJ /
No matter what are the interpretations for the recent new surprising observations, these discoveries certainly open a new window for understanding the strong interaction and hadron spectroscopy.
We need to have a global picture if there are new forms of hadrons beyond the naïve quark model —— any pentaquark, tetraquark, molecular state or other multiquark states cannot stay alone !
A lot of opportunities for BES III and other experiments working on hadron spectroscopy !!!
Prospects
谢 谢！Thank You!
ZEUS
No evidence for Ξ--(1862), Ξ0(1862) in deep inelastic scattering data.
)1530(0
WA89
Ξ- -(1862) was searched for with 676000 Ξ- candidates at WA89.
No evidence observed.
)( M
015.0)())1530((
))1862((0
BR
@ 99.9% C.L.
hep-ex/0405042
SPHINX
SPHINX systematically searched for Θ+(1540) in many final states.
No evidence was
observed.
RΛ*(1520) <0.02 @ 90 %CL
Cross Section Limit vs. M(NK)
LS KpK )(
SKnK )(
SS KpK )(
SL KpK )(
NKNp 0
hep-ex/0407026
MARK-III & DM2 Results
Threshold enhancement
pp/J
Claimed inPhys. Rep. 174(1989) 67-227
Too small statistics to draw any conclusion on the threshold enhancement,
e.g., cannot exclude known particles such as (1760)
MARK-III
DM2
ppM
