Transcript The mystery of the X(3872)

NTU
colloquium
June 11, 2007
S.L. Olsen
U of Hawai’i
高能所 北京
Homeless
mesons
Stephen L. Olsen
University of Hawai’I
& 高能所 北京
Constituent Quark Model: 1964
3 quarks
Gell-Mann
(& 3 antiquarks)
u+2/3
Zweig
d-1/3
u-2/3
s-1/3
Baryons: qqq
p:
p:
u+2/3 u+2/3
d-1/3
u-2/3 u-2/3
d+1/3
d+1/3
s+1/3
Mesons: q q
p +:
u+2/3
d+1//3
p-:
u-2/3
u+2/3
Constituent Quark Model: 2007
6 quarks
u+2/3
d-1/3
c+2/3
t+2/3
s-1/3 b-1/3
Baryons: qqq
W c:
W c:
c+2/3 s+1/3
s-1/3
u-2/3 u-2/3
d+1/3
(& 6 antiquarks)
u-2/3 c-2/3
d+1/3
t-2/3
+1/3
s+1/3 b
Mesons: q q
u+2/3
+
B :
b+1//3
B- :
u-2/3
b-1/3
but…
• quarks are not seen
• why only qqq and qq combinations?
• What about spin-statistics?
Fabulously successful at bringing
order to the hadron “zoo”
mesons
q
q
baryons
q
q
q
W-
s-1/3 s-1/3
s-1/3
three s-quarks
in the same
quantum state
Das ist verboten!!
The strong interaction “charge” of
each quark comes in 3 different
varieties
O. Greenberg
Y. Nambu
Ws-1/3 s-1/3
s-1/3
the 3 s-1/3 quarks in the
W- have different color
charges & evade Pauli
QCD: Gauge theory
for color charges
Yang
Mills
Nambu
Fritzsch & GellMann
generalization of QED
QED
scalar charge: e
QED gauge Xform
+ieA
1 vector
field
(photon)
QCD
isotriplet charge:
QCD gauge Xform
er
eb
eg
   + i a l i Gi
eight 3x3 SU(3)
matrices
8 vector
fields
(gluons)
Attractive configurations
eijk eiejek
i≠ j≠k
dij ei ej
same as the rules for combining colors to get white:
add 3 primary colors
or add color+complementary color
quarks: eiejek  color charges
antiquarks: ei ej ek  anticolor charges
Hence the name: Quantum Chromodynamics
Difference between QED & QCD
QED: photons have no charge
QCD: gluons carry color charges
gluons interact with each other
a
Coupling strengths
distance
Test QCD with 3-jet events
(& deep inelastic scattering)
as
gluon
rate for 3-jet events should
decrease with Ecm
“running” as
Why are these
people smiling?
Running as tests QCD at short
distances only
a
The long-distance regime,
where the matter we are
made of exists, remains
untested.
distance
Are there other color-singlet
spectroscopies?
Non-quark model states expected in QCD
Pentaquarks:
e.g. an S=+1 baryon
u
(only anti-s quark has S=+1)
u
d
d s
Glueballs:
gluon-gluon color singlet states
Multi-quark mesons:
qq-gluon hybrid mesons
u c
c u
c
c
Pentaquarks
“Seen” in many experiments
but not seen in just as
many others
Belle
BES
BaBar
CDF
High interest:
1st pentaquark paper
has ~720 citations
Experimental situation is messy
(some contradictory experiments)
γp  Ks K n
SAPHIR (2004)
4.8
Counts/4 MeV
+
CLAS (2005)
Same reaction
M(nK+)(GeV)
Some groups contradict themselves
gdp+K-K+n
CLAS-D (2005)
CLAS-D (2003)
5.2
???
no signal
Pentaquark Scoreboard
Positive signals
Negative results
Also: Belle
Compass
L3
CLAS
Yes: 17
No: 18
PDG 2006
“The conclusion that
pentaquarks in general, and the
Q+ 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
This talk: evidence for non-qq mesons
4 (& 6) quark states
u c
c u
c
c
“hybrid” qq-gluon states
The Beijing Electron Positron
Collider (BEPC)
高能物理研究所
e+
e-
Beijing Spectrometer (BES)
e+e- annihilation cross section
BES Energy Range
ss
cc
q
bb
q
Ecm(GeV)
J/y  g pp
g
p
c+2/3
C-2//3
u+2/3 u+2/3
d-1/3
p
u-2/3 u-2/3
d+1/3
J/y  g pp
What is this???
This is the hc,pp
the J/y’s
spin=0 partner
M(pp) GeV
Fit the M(pp) distribution
Best fit to this peak
is a resonance with
peak mass below the
pp mass threshold
M=1835 MeV
G  100MeV
no know
resonance
fitted peak
location
Actual fit
J/ygpp in the BES expt
M=1830.6 ± 6.7 MeV/c2
G < 153 MeV/c2 (90% CL)
c2/dof=56/56
0
0.1
0.2
0.3
A pp bound state (baryonium)?
There is lots & lots of literature about this possibility
deuteron:
baryonium:
attractive nuclear force
p
n
loosely bound
3-q 3-q color
singlets with
Md = 2mp- e
attractive force?
p
p
loosely bound
3-q 3-q color
singlets with
Mb = 2mp-d ?
An old idea
Fermi & Yang in 1949
(7 years before p discovery):
If NN potential is attractive, they
could bind to form p-like states.
Expectation for pp bound
state meson
below-threshold
p and p
annihilate to
mesons
I=0, JPC=0-+ init. state:
pp  p+p-h’ is common
Above threshold
Xpp ~100%
mp +mp
Look in J/y  g p+p-h’
mp+mp
M=1833 MeV
G  70MeV
M(p+p-h’)
X(1835): “6-quark” meson?
u+2/3 u+2/3
d-1/3
u-2/3 u-2/3
d+1/3
3 quarks
+
3 antiquarks
•Need to confirm JPC of the p+p-h’ peak is 0-+
•Need to find it in other common 0-+ pp
annihilation channels
Move over to Japan
Tsukuba Mountain
KEKB Collider
KEK laboratory
Belle Expt
e+e- annihilation cross section
KEK B-factory
ss
cc
q
bb
q
Ecm(GeV)
Primer on
Charmonium
B meson decays
C+2/3
b-1/3
“Charmonium”
C-2/3
u-2/3
S-1/3
u-2/3
K-
Charmonium
mesons formed from c- and c-quarks
c
r
c
c-quarks are heavy: mc ~ 1.5 GeV  2mp
velocities small: v/c~1/4
non-relativistic QM applies
QM of cc mesons
c
r
c
2

2
  + V (r )  E
2mr
What is V(r) ??
“derive” from QCD
quantum chromodynamics
“Cornell” potential
c
r
~0.1 fm
c
slope~1GeV/fm
“confining”
large distance
component
V(r)
G.S.Bali
hep-ph/0010032
2 parameters:
slope & intercept
1/r “coulombic”
short distance
component
Charmonium spectrum
y’’
y’
hc’
hc
hc
cc0,1,2
J/y
All of these states
are well established
Study
+
BK p p J/y
p+
J/y
C+2/3
b-1/3
pC-2/3
u-2/3
S-1/3
u-2/3
K-
The X(3872)
BK p+p-J/y
y’p+p-J/y
X(3872)p+p-J/y
M(ppJ/y) – M(J/y)
S.K. Choi et al PRL 91, 262001
Its existence is well established
seen in 4 experiments
CDF
9.4
11.6
X(3872)
D0
X(3872)
Is it a cc meson?
Could it be
one of these?
3872 MeV
These states
are already
identified
Determine
PC
J
quantum numbers
of the X(3872)
with minimal assumptions
C=+1 is established
X(3872)gJ/y seen in:
M(pp) looks like a r
CDF
PRL 96 102002
Belle
hep-ex/0505037
&
Belle
X(3872)”w”J/y seen
Belle
Use Angular Correlations to
determine J & P
rp+p-
Jz=0
X3872
z
Rosner (PRD 70 094023)
Bugg (PRD 71 016006)
Suzuki, Pakvasa (PLB 579 67)
J=0
J=0
K
J/ym+m- (e+e-)
0++
ereJ/y
0-+
k(erxeJ/y)
Ruled out by Belle
qlp
y
c2/dof=34/9
c2/dof = 34/9
|cosq|
|cosqlp|
rule out 0++ & 0 -+
|cosy|
Angular analysis from CDF
CDF Collab. PRL 98, 132002 (2007)
1++
or
2-+
Possible JPC values
0--
0-+
0++
0+-
exotic
violates parity
(hc”)
DD allowed
exotic
DD allowed
1- -
1-+
DD allowed
(y(3S))
exotic
DD allowed
++
1
(hc’)
2- (y2)
2- +
(hc2)
2++
2+-
DD allowed
exotic
DD allowed
(cc0’)
++
1
(cc1’)
(cc2’)
1+-
can it be a
++
1
1++cc1’
(the only
charmonium
possibility)
cc state?
M=3872 MeV is too
low, especially now
that we know that
M(cc2’)=3931  4 MeV
Xp+p- J/y decay
3872
g
p+pAllowed
(Isospin E1
transition
violating)
is isospin-violating for
a 1++ cc state
The G(Xg J/y) partial
width is expected to be
30~40xG(Xp+p- J/y);
experimentally it is
~1/10th
Intriguing fact
MX3872 =3871.2 ± 0.5 MeV
mD0 + m D0* = 3871.6 ± 0.4 MeV
lowest mass
lowest mass spin=1
charmed meson
charmed meson
Deuson? deuteron-like DD* bound state?
c
Du
p
D*u
c
one p exchange
attractive for 1++
2 loosely bound
qq color singlets with
M = mD + mD* - d
Tornqvist PLB 590, 209 (2004)
Braaten et al, PRL 93, 162001
DeRujula, Georgi,Glashow, PRL 38, 317
(1977)
X(3872)??
X(3872) = D0D*0 bound state?
• JPC = 1++ is favored
• M ≈ mD0 + mD0*
Tornqvist PLB 590, 209 (2004)
• Large isospin violation is natural (&

|D0D*0> =
1/2(|10>
was predicted):
- |00>)
Equal mixture of I=1 & I =0
Swanson PLB 588, 189 (2004)
•
G(XgJ/y) < G(XppJ/y) was predicted
•
G(XD0D0p0) too large?
Swanson PLB 598, 197 (2004)
• Bf(B0K0X3872)/Bf(B+K+X3872) too large?
Braaten & Kusunoki PR D71, 074005 predict:
BaBar measurement (hep-ex/0507090):
<0.08
0.5  0.3
X(3872) summary
–
–
–
–
–
Existence well established
JPC = 1++ (probably)
Br(Xp+p- J/y) too high for charmonium
Br(XD0D0p0) too high for molecule
Mass too low for hybrid
Four years after discovery, theorists
are still puzzling over what it may be
Next, California
Stanford Linear
Accelerator Ctr
BaBar Detector
Radiative return
B-factory
energies
ss
cc
bb
10.58 GeV
3~5
GeV
Ecm(GeV)
BaBar’s Y(4260)
e e  g ISR p p J /y
+ -
+
-
10.58 GeV
4.26 GeV
M=4259  8 MeV
G = 88  23 MeV
Y(4260)
J/y sideband
B. Aubert et al. (BaBar)
hep-ph/0506081
(e+e-hadrons)
not seen in (e+e-hadrons)
at Ecm =4.26 GeV
BES
J.Z. Bai et al. (BESII)
PRL 88 101802
Well above DD & DD* threshold but wide
& found in a suppressed mode??
No 1-- cc slot for the Y(4260)
X.H. Mo et al, hep-ex/0603024
4260
J.Z. Bai et al. (BESII)
PRL 88 101802
4260
If not charmonium, what?
c
c
“hybrid” cc-gluon state?
But why does it decay to p+p- J/y,
and not to D and D* mesons?
Y(4260) summary
–
–
–
–
Existence well established
JPC = 1-G(Xp+p- J/y) too high for charmonium
Br(XD(*)D(*)) too low for hybrid
Another mystery!!
Concluding remarks
• Pentaquarks are dead (at least for now)
• A number of “mysterious” mesons have been
found
• Are these curiosities?
or 1st signs of new hadron spectroscopies?
• 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:
QCD:
photons have no charge
gluons carry color charges
gluons interact with each other
QCD: Gauge theory
for color charges
Yang
Mills
Nambu
Fritzsch & GellMann
generalization of QED
QED
scalar charge: e
QED gauge Xform
+ieA
1 vector
field
(photon)
QCD
isotriplet charge:
QCD gauge Xform
er
eb
eg
   + i a l i Gi
eight 3x3 SU(3)
matrices
8 vector
fields
(gluons)
Vacuum polarization QED vs QCD
2nf
11CA
in QCD: CA=3, & this dominates
QEDQCD difference
Coupling
strength
a
distance
Test QCD with 3-jet events
(& deep inelastic scattering)
as
gluon
rate for 3-jet events should
decrease with Ecm
“running” as
Looking for
a home:
No rooms left
Fussy!
quark-antiquark chalet
x1835
Y4260
Molecule Manors
rats!
DDp
x1835
Y4260
M<4.4 GeV
need not apply
Fat
Cats!
Hydrid heaven
Y4260
Other hadronium states?
fitted peak
location
J/ygpp in the BES expt
J.Z.Bai PRL 91,022001(2003)
+3 +5
M=1859-10 -25 MeV/c2
G < 30 MeV/c2 (90% CL)
c2/dof=56/56
0
0.1
0.2
M(pp)-2mp (GeV)
0.3
acceptance
Charmonium state?
(e+e-hadrons)
No sign of it (e+e-hadrons)
at Ecm =4.26 GeV
BES
J.Z. Bai et al. (BESII)
PRL 88 101802
4260
DD** threshold in relation to
the “Y(4260)”
D** spectrum
No obvious
distortions
4.28-mD
M(p+p-J/y) GeV
it likes to decay to pp if it can
Decays to pp
Decays to mesons
A pp bound state (baryonium)?
There is lots & lots of literature about this possibility
deuteron:
baryonium:
attractive nuclear force
p
attractive force?
E. Fermi, C.N. Yang, Phys. Rev. 76, 1739 (1949)
n
p
p
!!!
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/0405087
B. Loiseau et al., hep-ph/0411218
loosely bound
3-q 3-q color
singlets with
…
Md = 2mp- e
loosely bound
3-q 3-q color
singlets with
Mb = 2mp-d ?
The X(3872)
Study p+p-J/y produced in BK p+p- J/y decays
????
hadronic molecules
a new spectroscopy?
may be more particles to find
summary
• X(1835):
– Existence well established
– JPC = 0-+
– Br(Xpp) too high for qq meson
– Xp+p-h’ is expected for sub-thresh pp state