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