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Searching for new forms
of hadronic matter Stephen L. OlsenUniversity of Hawai’i
& 高能物理所 北京
Wuhan
武汉10/15/07
History:(sub-atomic
particles)
1932: proton & neutron
..all we need???
1937: muon
“Who ordered that?”
1947: pion
predicted in 1935
1950’s: ,,,,,…
“Had I foreseen that, I would have
gone into botany” – Fermi
chadwick
Fermi
TingPeters Jones
Rabi
Yukawa
Joliet-Curie
Hadron “zoo”mesons baryons
No “econom
y”
Constituent Quark Model: 1964
(& 3 antiquarks)
Mesons: q q
p: u+2/3
p: u-2/3
+: d-1/3
u+2/3
d+1/3
u-2/3
u-2/3
d+1//3
u+2/3
-: d-1/3
u-2/3
d+1/3 s+1/3
u+2/3
d-1/3 s-1/3
Gell-Mann 3 quarks
Zweig
Baryons: qqq
Constituent Quark Model: 2007
(& 6 antiquarks)
Mesons: q q
c: c+2/3
c: C-2/3
+ : s-1/3
s+1/3
s+1/3
c-2/3
u-2/3
b+1//3
u+2/3
- : b-1/3
S=1/3
b+1/3
t-2/3c+2/3
b-1/3
t+2/3
6 quarks
Baryons: qqq
u-2/3
d+1/3 s+1/3
u+2/3
d-1/3 s-1/3
Fabulously successful at bringing order to the hadron
“zoo”
mesons baryonsqq qq
q
“econom
y”is re
covere
d
Fabulously successful, but…
• Why are isolated quarks are not seen?
• why only qqq and qq combinations?
• What about spin-statistics?
s-1/3
s-1/3
s-1/3
three s-quarksin the same
quantum state
禁止
The “charge” for the strong force
is a 3-dim spinor
Y. NambuO. Greenberg
s-1/3
s-1/3
s-1/3
the 3 s-1/3 quarks in the- have different colorcharges & evade Pauli
-
Each quark can have 3 different “color” charges
QCD: Gauge theory for color charges
generalization of QED
+ i e A + i i Gi
QED gauge Xform QCD gauge Xform
eight 3x3 SU(3) matrices
8 vectorfields
(gluons)
1 vectorfield
(photon)
scalar charge: e triplet charge:
er
eb
eg
QED QCD
Yang MillsNambu
Fritzsch & GellMann
Attractive configurations
ijk eiejek
i ≠ j ≠ k
ij ei ej
same as the rules for combining colors to get white:
add 3 primary colors or add color+complementary color
antiquarks: anticolor charges
Hence the name: Quantum Chromodynamics
quarks: eiejek color charges
ejei ek
Difference between QED & QCD
QED: photons have no charge
QCD: gluons carry color chargesgluons interact with each other
Coupling strengths
distance
Test QCD with 3-jet events(& deep inelastic scattering)
rate for 3-jet events should decrease with Ecm
gluons
s
Energy
dist
“running” s
Winners of the2004 Nobel Prize
Running as tests QCD at short distances only
distance
The long-distance regime,where the matter we are made of exists, remains untested.
Are there other color-singlet arrangements?
Pentaquarks:e.g. an S=+1 baryon
(only anti-s quark has S=+1)
Glueballs:gluon-gluon color singlet states
Multi-quark mesons:
qq-gluon hybrid mesons
u cuc
c c
ud
usd
Non-quark model states expected in QCD
Spring8 electron Ring in Japan
A pentaquark?
T.Nakano et al (LEPS) PRL 91 012002 (2003) 742 citations!!
+(1530)?
M(K+n)
s+1//3
u+2/3 u+2/3
d-1/3
d-1/3
S=+1 baryon: impossible
with only qqq
+ n K- K+ n
Experimental situation is messy(some contradictory experiments)
SAPHIR (2004)4.8
M(nK+)(GeV)
Cou
nts
/4 M
eV
nKKγp s
CLAS (2005)
Same reaction
Some groups contradict themselves
5.2CLAS-D (2003)
nosignal
CLAS-D (2005)
???
d+K-K+n
Pentaquark Scoreboard
Positive signals Negative results
Also: Belle Compass L3 CLAS
Yes: 17 No: 18
Status in 2006
“ The conclusion that pentaquarks in general, and the in particular, do not
exist, appears compelling.” - George Trilling LBL
This is a risky business
You never know if nature is smiling at you
or something else
Another approach: look for non-qq mesons
c c
u cuc
4 (& 6) quark states
“ hybrid” qq-gluon states
u u
uud
d
theory:mc2>4.2 GeV
The Beijing Electron Positron Collider (BEPC)
e+
e-
高能物理研究所
Beijing Spectrometer (BES)
e+e- annihilation cross section
sscc
bb
Ecm(GeV)
q
q
BES Energy Range
J/ pp
C-2//3
c+2/3
p
p
u
uu
ud
d
J/ pp
This is the cpp
the J/’s wellknown S=0
partner
What is this???
M(pp) GeV
BESII
J.Z. Bai et al. (BESII)PRL 91 022001 (2003)
Fit the M(pp) distribution
Best fit to this peakis a resonance withpeak mass below thepp mass threshold
M=1830.6 ± 6.7 MeV/c2
< 153 MeV/c2 (90% CL)
matches to no known state.
A pp bound state (baryonium)?
p n p p
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
An old idea
Fermi & Yang in 1949 (7 years before p discovery):
If NN potential is attractive, they could bind to form -like states.
Expectation for pp bound state meson
mp +mp
Above threshold
Xpp ~100%
below-threshold p
and p annihilate to
mesons
I=0, JPC=0-+ init. state:pp ’ is common
Ding & Yan Phys.Rev.C72:015208,2005.
BES looked at J/ ’
M(’)
M=1833 MeV 70MeV
mp+mp
These values matchthose for the pp peak
(as predicted by Ding&Yan)
BESII
M. Ablikim et al. (BESII)PRL 95, 262001 (2005)
X(1835): a“6-quark” meson?
3 quarks+
3 antiquarks
•Need to confirm JPC of the ’ peak is 0-+
•Need to find it in other common 0-+ pp annihilation channels
job for BESIII
uu
u
ud
d
Move over to Japan
Tsukuba Mountain
KEK laboratory
KEKB Collider
International Collaboration Belle
e+e- annihilation cross section
sscc
bb
Ecm(GeV)
q
q
KEK B-factory
B meson decays
u-2/3
b-1/3 C-2/3
C+2/3
u-2/3
S-1/3
W -
K-
“Charmonium”
Primer on Charmonium
Charmonium
r
mesons formed from c- and c-quarks
c-quarks are heavy: mc ~ 1.5 GeV 2mp
velocities small: v/c~1/4
non-relativistic QM applies
c c
QM of cc mesons
ErVmr
)(2
22
c cr
What is V(r) ??
“ derive” from QCD
quantum chromodynamics
“Cornell” potential
~0.1 fm
G.S.Bali hep-ph/0010032
“confining”large distance
component
slope~1GeV/fm
1/r “coulombic”short distance
component
c cr
V(r)
2 parameters:slope & intercept
Charmonium spectrum
All of these statesare well established
J/
’
c
c’c
’’
hc
Study BK-J/
u-2/3
b-1/3 C-2/3
C+2/3
u-2/3
S-1/3
W -
look here
J
K
The X(3872)
BK J/
M(J) – M(J/)
’J/
X(3872)J/
S.K. Choi et al PRL 91, 262001
Its existence is well established
seen in 4 experiments
X(3872)
CDF
X(3872)
D0
hep-ex/0406022
9.411.6
Is it a cc meson?
These states are alreadyidentified
3872 MeV
Could it beone of these?
The JPC quantum numbersof the X(3872) are 1++
From studying different decay processes& angular correlations among decay
products
can it be the 1++ cc state?
1++c1’(the onlycharmonium possibility)
3872
XJ/decayis a forbidden
decay
(Isospin violating)
M=3872 MeV is low,
Allowed E1transition
23P1 cc state
Intriguing fact
MX3872 =3871.2 ± 0.5 MeV
mD0 + m D0* = 3871.6 ± 0.4 MeV
lowest masscharmed meson
lowest mass spin=1charmed meson
D D*
2 loosely bound qq color singlets
with M = mD + mD* -
u
cu
c
one exchangeattractive for 1++
Tornqvist PLB 590, 209 (2004)Braaten et al, PRL 93, 162001
Deuson? deuteron-like DD* bound state?
Another old ideaDeRujula, Georgi,Glashow, PRL 38, 317 (1977)
X(3872)??
X(3872) summary
– Existence well established– JPC = 1++
– Br(X J/) too high for charmonium– Mass too low for hybrid
Four years after discovery, theoristsare still puzzling over what it may be
Next, CaliforniaStanford LinearAccelerator Ctr
BaBar Detector
Radiative return
sscc
bb
Ecm(GeV)
10.58 GeV
B-factoryenergies
3~5GeV
/ISR Jee
J/ sideband
Well above DD & DD* threshold but wide & found in a suppressed
mode??
M=4259 8 MeV = 88 23 MeV
B. Aubert et al. (BaBar)PRL 95 142001 (2005)
Y(4260)
10.58 GeV
4.26 GeV
not seen in (e+e-hadrons)at Ecm =4.26 GeV
J.Z. Bai et al. (BESII)PRL 88 101802
BES
Y(4260)
(e
+e
- h
ad
ron
s)
a 1-- cc slot for the Y(4260)?
42604260
X.H. Mo et al, hep-ex/0603024
J.Z. Bai et al. (BESII)PRL 88 101802
no cc sl
ot for
it!no cc
slot f
or
it!
Theorist’s favorite interpretation
c c
“ hybrid” qq-gluon states
just about the right mass for theory
A ’ peak at 4325MeV
Nbkg = 3.1 1.0
Nevt = 68 (<5.7 GeV/c2)
2-prob < 5.7 GeV/c2
Y(4260) 6.5 10-3
(4415) 1.2 10-13
Y(4320) 29%
e+e-ISR ’
M=4324 24 MeV
= 172 33 MeV
S.W.Ye QWG-2006 June 2006
Not Compatible with the Y(4260)
D1D
D2D
298 fb-1 (BaBar) hep-ex/0610057
BaBar PRL 98 252001 (2007)
New results on the ’ peak from Belle
548 fb-1
X.L. Wang et al (Belle) arXiv:0707.3699
It is really two peaks!
M=4664 11 ±5 MeV
= 48 15 ±3 MeV
M=4361 9 ±9 MeV
= 74 15 ±10 MeV
(both relatively narrow)
(neither one consistent with 4260)
4260
Need 2 more 1-- cc slots for Y(4630) & Y(4660)
42604260
X.H. Mo et al, hep-ex/06030244660
4360
Excited hybrid states?
c c
Latest Newsele
ctric
ally
charg
ed!!
M(±’) from BK ±’
K. Abe et al (Belle) arXiv:0708.1790
M(’) GeV
6.5
M = 4433 ±4 ±1 MeV
tot = 45 +17 +30 MeV
Nsig =124 ± 31evts-13 -11
Can’t be a cc meson or a hybrid
4260
4660
4360
No charged cc hybrid states
gluons have zero charge
C+2/3 C-2/3
SummaryMesons with no qq assignment:
M(pp) GeV
X(1835)
M(J) – M(J/)
X(3872)J/
Y(4260)
548 fb-1
Y(4660)
Y(4360)
M(J)
M(’) GeV
Z±(4430)Y(3940)
M(J/) MeV
BESII
Concluding remarks
• A number of “mysterious” mesons that don’t fit into the simple quark model picture have been found
• If they are related to each other, these particles can’t be the hybrid states predicted by QCD
• Are these curiosities, each with its own story? … or are they 1st signs of a spectroscopy of new
forms of hadronic matter?
• Hopefully, time, & more experimentation, will tell
謝謝
Thank you
Back-up slides
Conclusion
• either:– The constituent quark model for
mesons needs major revision
• or:– There is a new, non-qq, hadron
spectroscopy, maybe more than one.
Difference between QED & QCD
QED: photons have no charge
QCD: gluons carry color chargesgluons interact with each other
Vacuum polarization QED vs QCD
2nf
11CA
in QCD: CA=3, & this dominates
The LEPS observation of +(1530)
n
K- n
K+
+ n K- K+ n
M(K+ n)
s+1//3
u+2/3 u+2/3
d-1/3
d-1/3
(1530)
Physical Review Letters, 91, 012002 (2003)
+ n K- + K- K+ n
S=+1
Charmonium state?(
e+e
- h
ad
ron
s)
No sign of it (e+e-hadrons)at Ecm =4.26 GeV
BES
4260
J.Z. Bai et al. (BESII)PRL 88 101802
No pla
ce fo
r
it!No p
lace
for
it!
Actual fit
M=1830.6 ± 6.7 MeV/c2
< 153 MeV/c2 (90% CL)
J/pp in the BES expt
0 0.1 0.2 0.3
2/dof=56/56
fitted peak location
A pp bound state (baryonium)?
p n p p
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)
Y.Nambu, G. Jona-Lasinio Phys Rev 122, 345 (1961) …I.S. Shapiro, 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/0405087B. Loiseau et al., hep-ph/0411218
…
These are very famous papers
!!!
The X(3872)
????
Study J/ produced in BK J/decays
hadronic molecules
a new spectroscopy?
may be more particles to find
summary• X(1835):
– Existence well established– JPC = 0-+
– Br(Xpp) too high for qq meson– X’ is expected for sub-thresh pp
state
l
|cosl|
2/dof = 34/9
|cos|
|cos|
2/dof=34/9
0++ 0-+
rule out 0++ & 0 -+
J kxJ
Ruled out by Belle
C=+1 is establishedX(3872)J/ seen in:
&Belle
PRL 96 102002
M( looks like a
X(3872)””J/ seen
CDF Belle
Belle
hep-ex/0505037
Angular analysis from CDF
CDF Collab. PRL 98, 132002 (2007)
1++
or2-+
Use Angular Correlations to determine J & P
K
J/ee
J=0J=0X3872
Jz=0
z
Rosner (PRD 70 094023)
Bugg (PRD 71 016006)
Suzuki, Pakvasa (PLB 579 67)
Possible JPC values
0--
exotic
violates parity
0-+
(c”)
0++
DD allowed
(c0’)
0+-
exotic
DD allowed
1- -
DD allowed
((3S))
1-+
exotic
DD allowed1++
(c1’)
1+-
(hc’)
2- -
(2)
2- +
(c2)
2++
DD allowed
c2’)
2+-
exotic
DD allowed
1++
X(3872) = D0D*0 bound state?
• JPC = 1++ is favored
• M ≈ mD0 + mD0*
• Large isospin violation is natural (& was predicted):
|D0D*0> = 1/2(|10> - |00>)
• (XJ/) < (XJ/) was predicted
• (XD0D00) too large?
• Bf(B0K0X3872)/Bf(B+K+X3872) too large?
Equal mixture of I=1 & I =0
Swanson PLB 598, 197 (2004)
Tornqvist PLB 590, 209 (2004)
Swanson PLB 588, 189 (2004)
Braaten & Kusunoki PR D71, 074005 predict: <0.08BaBar measurement (hep-ex/0507090): 0.5 0.3
Y(3940) in BK J/
M≈3940 ± 11 MeV≈ 92 ± 24 MeV
Belle PRL94, 182002 (2005)
M(J/) MeVM2(K) GeV2
M2(
J
) G
eV2
If not charmonium, what?
c c “ hybrid” cc-gluon state?
But why does it decay to J/, and not to D and D*
mesons?
Y(4260) summary
– Existence well established– JPC = 1--
– (X J/) too high for charmonium– Br(XD(*)D(*)) too low for hybrid
Another mystery!!
J/ pp
C-2//3
c+2/3
u+2/3
u-2/3
d-1/3u+2/3
d+1/3
u-2/3
p
p