Exotic Mesonsfrom an experimental perspective

S. Olsen 贵州大学June 3 2008

M(M

eV

)

JPC

DD(3770)

c1c2

’c

c

X(3940)X(3940)

X(41X(416060))

X(3872)X(3872)

Y(3940)Y(3940)(4040)

(4415)

(4160) Y(4260)Y(4260)

Y(4360)Y(4360)

c0

hc

J/

’

c2’

ZZ++(4440)(4440)

Y(4660)Y(4660)Placed here by JPC

The XYZ Mesons

can’t all be accommodated inthe charmonium spectrum

What are they?

•NA Tornqvist PLB 590, 209 (2004)•ES Swanson PLB 598,197 (2004)•E Braaten & T Kusunoki PRD 69 074005 (2004)•CY Wong PRC 69, 055202 (2004)•MB Voloshin PLB 579, 316 (2004)•F Close & P Page PLB 578,119 (2004)•X Liu arXiv 0708..4167…

•L Maiani et al PRD 71,014028 (2005)•T-W Chiu & TH Hsieh PRD 73, 111503 (2006)•D Ebert et al PLB 634, 214 (2006)…

• P Lacock et al (UKQCD) PLB 401, 308 (1997)•SL Zhu PLB 625, 212 (2005) •FE Close, PR Page PLB 628, 215 (2005)• E Kou, O Pene PLB 631, 164 (2005)

…

Molecules?

PDG: MD0 + MD*0 = 3871.8 ± 0.4 MeV

MeVPDG: M(X3872)M(X3872) =

Belle: M(Z4430)M(Z4430) =4433 ± 5 MeV

PDG: MD* + MD1 = 4432.6 ± 1.4 MeV

Equal to 1 part in 10-4

Coincidence?

arXiv: hep-ph/0308277

arXiv: 07084222

correct predictions

But not 1+

JP of the Z(4430)?

l

l+l- ’ kl

K

l+l- ’

0-

1-

JP=1+ favored,but only @ ~2 level

1+

arXiv: 0801.3540

””…

arXiv: 0801.1616

”

”

Molecules/threshold effectsshould be near thresholds

DSDS thresholdsDD thresholds

some of the states are near thresholds,but this is not a universal feature

Note: there is no- or -exchange

between Ds states??

??

??

??

Molecular picture may work for some XYZ states, but

not all.

Diquark –antidiquark?

uccu

dccd

dccu

uccd

These should come in isospin- & SU(3)-multiplets

where are the “partner states”?

Xu(3872) Xd(3872) X+(3872) X-(3872)

Expect:

Bf(B0K-X+)Bf(X+J/)

Bf(B-K-X0)Bf(X+J/)≈ 2

B+K-Xu B0K0Xd

M(Xd)-M(Xu)= 2(md-mu)/cos

L Maiani et al PRD 71,014028 (20050

8 ± 3 MeV

BKSX & BK±X comparison

M = 0.22 ± 0.90 ± 0.27 MeV

Compared to 8±3 MeV(Maiani et al PRD 71 014028)

BaBar 0803.2838

KS mode

K± mode

KS mode

K± mode

M = 2.7 ± 1.6 ± 0.4 MeV

no X±(3872) isospin partner is seen

B0 K± ∓ 0J/ B∓ KS ∓ 0J/

Bf(B0K-X+)Bf(X++0J/)

Bf(B-K-X0)Bf(X++-J/)< 0.4

(expect 2)

? ?

None of the partner states required by the diquark-diantiquark picture

have yet been seen.

How about cc-gluon hybrids?

c c

• qq-gluon excitations predicted 30 yrs ago • LQCD: lowest 1-- cc-gluon mass ~4.3 GeV

- QCD sum rules get lower values ~3.7 GeV • relevant open charm threshold is D**D (~4.28 GeV) • (J/) larger than that for normal charmonium • (e+e-) for 1-- states less than ordinary charmonium

Horn & Mandula PRD 17, 898 (1977)

Banner et al, PRD 56, 7039 (1997); Mei & Luo, IJMPA 18, 15713 (2003)

Isgur, Koloski & Paton PRL 54, 869 (1985)

McNeile, Michael & Pennanen PRD 65, 094505 (2002)

Close & Page NP B443, 233 (1995)

Kisslinger et al, arXiv 0805.1943 (2008)

Y(4260) s

eems t

o matc

h all

of these

!!!

DD** thresholds in & “Y(4260)”

4.26

D** spectrum

M(J/) GeV

No obviousdistortions

D1D

D2D

4.7

4.5

4.3

4.1

3.9

3.7

D

D DD

D

D

DD(**) thresholds

e+e- ’ peaks in Belle

M=4324 24 MeV

= 172 33 MeV

548 fb-1

X.L. Wang et al (Belle) arXiv:0707.3699PRL 99, 142002 (2007)

Two peaks!

M=4664 11 ±5 MeV

= 48 15 ±3 MeV

M=4361 9 ±9 MeV

= 74 15 ±10 MeV

Earlier BaBar values

(both relatively narrow)(& both above all D**D thresh)

(& neither consistent with 4260)42

60

436

0

466

0

Y(4360) & Y(4660) are above

all DD** thresholdsD** spectrum

4.7

4.5

4.3

4.1

3.9

3.7

D

D DD

D

D

4.36

4.66

No signs in (e+e- D0D

Belle: G. Pakhlova et al, PRL 100, 062001 (2008)

D0*(2400)D + D2*(2460)D

4260

4360

4660

100pb

(e+e- +-J/)

~60pbC.Z. Yuan et al, PRL 99, 182004 (2007)

eyeball estimate

5.0)(

)/(**

2**

04260

4260

DDDDYBf

JYBf

(e+e- +-’)

~70pb

~40pb

X.L. Wang et al, PRL 99, 142002 (2007)5.0

)(

)(**

2**

04660,4360

4660,4360

DDDDYBf

YBf

eyeball estimate

(Y +-J/ (’)) are large

X.H. Mo et al, PLB640, 182 (2006): (Y4260J/)>10x10x(3770+-J/)

BES: PRL 88, 101802 (2006)

426

0

436

0

436

0

Belle (DD + DD* + D*D* + DD)

Data are in poor agreement with hybrid expectations

Moreover, there are no charged charmonium hybrids, so these

can’t account for the Z+(4430)

Are there XYZ counterpartsin the ss- & bb- systems?

Belle:((5S)(nS))

2S

3S4S

(4S) (1S) +

(4S)(1S)477 fb-1 from Belle

44±

8 ev

ts“(5S)”(1S)23.6 fb-1 from Belle

(1/20 times the data &~1/10th the crosssection)

325±

20 e

vts!

8 times as many events!

Belle 0710.2577

K.F. Chen et al (Belle) PRL 100, 112001 (2008)

is Huge!!!

Partial Widths

N.B. Resonance cross section 0.302 ± 0.015 nb at 10.87 GeV PRD 98, 052001 (2007) [Belle]

Cf (2S) (1S) ~ 6 keV (3S) 0.9 keV (4S) 1.8 keV

Assume “(5S)” = (5S)PDG value taken for (nS) properties

>100 times bigger!!

+- (nS) Dalitz plots

(1S) + (2S) +

It looks like there is a bbversion of the Y(4260), the “Yb,”

lurking around the (5S)

W.-S. Hou PRD 74, 017504 (2007)

Yb +-(nS)

(5S)

(4S)

If there are bb versions of the XYZ’s, why not ss versions as well?

1-- Ys states around 2 GeV?Y(2175)f0(980)

from BaBar

e+e- f0(980)@ Ecm ~10.6 GeV BESII

M(f0(980) GeV

M.Ablikim et al (BES)PRL 100, 102003 (2008)

ss equivalent of the J/

Maybe the X(1835) is one too?

M. Ablikim et al (BESII), Phys.Rev.Lett.95:262001,2005

J/X(1835) | ’

X(1835)

mostly ss

comments• There is a new meson spectroscopy not well explained as qq states

– Maybe more than one– Bodes well for BESIII, Super-B factories & PANDA

• Some states are narrow even though they are far above decay thresholds– e.g. Y(4660)’ & Z+(4430)’ have large Q but ≈50 MeV

• characterized by large partial widths (or Bfs) to hadrons+J/(or ’)

– Br(X(3872)J/) > 4.3% (Isospin=1)– (Y(3940)J/) > 7 MeV – (Y(4260)J/) > 1.6 MeV

• States that decay to ’ not seen decaying to J/ (and vice-versa) – Bf(Y(4660)’) >> Bf(y(4660)J/) same for Y(4360) & Z(4430’– Y(4260) not seen in Y(4260)’

• The new 1-- states are not apparent in the e+e-D(*)D(*) cross sections

• There are no evident changes at the D**D mass threshold

• None of the existing ideas for non-qq mesons, i.e. molecules, di-quarks & hybrids, provide a natural explanation for the observed properties.

•Not all candidate states are close to thresholds.

•None of the expected Ispin- or SU(3) partners are seen

•No influence from DD** threshold observed

•No possibility to accommodate the Z+(4430)

Candidate models

Implications for BES-III

•Search for charmonium-like states decaying to c mesons •so far only J/ & ’ final states have been studied•At BES-III we have the possibility of clean c signals

For example: arXiv: 0805.4460 (last week)

Accessible at BES-III?

Implications for BES-III

•Search for charmonium-like states decaying to c mesons •so far only J/ & ’ final states have been studied•At BES-III we have the possibility of clean c signals

•Measure “open strangeness” decay modes for X(1835), Y(2175), etc•hybrid models say K1(1270)K &/or K1(1400)K should dominate

•Systematic studies of final states including a or an ’ •need to find patterns

Example:+-’ spectrum with 58M J/’s

M(’) GeV/c2

2 yrs @ BESII

X(1835)2.5 days @ BES-III

M(’) GeV/c2

final comments

1963 Elementary particle “zoo”mesons

baryons

+…

+…

One good idea

baryons

su sd

ds us

du dd uu ud

mesons

etc.

Gell-Mann

Zweig

2008: a new “zoo”

X(1835)

Y(4360)Y(4660)

Z+(4430) Y(2175)

Y(3940)

X(3940)

Y(4260)

X(4160)

We need a new idea

• There is lots still to be learned about hadronic physics.

• BES-III is well positioned in time & energy to contribute.

• There are big challenges (& opportunities) for theorists.

Summary

My advice to theorists present:

•Think out of the box.

•加油

謝謝