New Results on Hadron Spectroscopy (Experimental Review) Shan JIN Institute of High Energy Physics...

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New Results on Hadron Spectroscopy(Experimental Review)

Shan JINInstitute of High Energy Physics (IHEP)

Chinese Academy of Sciences

jins@mail.ihep.ac.cn

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

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 %95@16.0~027.0)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

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

fBR%95@13.0

))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

fBR%95@13.0

))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

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