The hidden charm of hadrons
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Transcript of The hidden charm of hadrons
The hidden charm of hadrons
Stephen L. Olsen University of Hawai’i
Representing Belle
Invited talk at the Tampa APS/DPF meeting, April 19, 2005
test of QCD: “running” s
Probe QCD from other directions
non-qq or non-qqq hadron spectroscopies:
Pentaquarks:e.g. an S=+1 baryon
Glueballs:gluon-gluon color singlet states
Multi-quark mesons:
qq-gluon hybrid mesons
u cuc
c c
ud
usd
This talk: search for non-standard mesons
with “hidden charm”
• standard cc mesons are:– best understood theoretically– narrow & non overlapping
• c + c systems are commonly produced in B meson decays.
b
cc
s
Vcb
cosC
CKM favored
W-
c c
u cuc (i.e containing c & c)
Thanks to KEKB, Belle has lots of B mesons
(>1M BB pairs/day)>1fb -1/day
Design: 10 34
Is the X(3872) non-standard?
BK J/
M(J) –M(J/)
’J/
X(3872)J/
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?
no obvious cc assignment
3872
c”
hc’
c1’
2
c2
3
M too low and too small
angular dist’n rules out 1
J/ way too small
c too small;M() wrong
c& DD) too small
c should dominate
SLO hep-ex/0407033
go back to square 1
DetermineJPC
quantum numbersof the X(3872)
with minimal assumptions
JPC possibilities (for J ≤ 2)
0--
exotic
violates parity
0-+
(c”)
0++
DD allowed
(c0’)
0+-
exotic
DD allowed
1- -
DD allowed
((3S))
1-+
exotic
DD allowed
1++
(c1’)
1+-
(hc’)
2- -
(2)
2- +
(c2)
2++
DD allowed
c2’)
2+-
exotic
DD allowed
JPC possibilities0-- ruled out; JP=0+,1- & 2+ unlikely
0--
exotic
violates parity 0-+
(c”)
0++
DD allowed
(c0’)
0+-
exotic
DD allowed
1- -
DD allowed
((3S))
1-+
exotic
DD allowed
1++
(c1’)
1+-
(hc’)
2- -
(2)
2- +
(c2)
2++
DD allowed
c2’)
2+-
exotic
DD allowed
Areas of investigation
• Search for radiative decays
• Angular correlations in XJ/ decays
• Fits to the M() distribution
• Search for X(3872)D0D00
Search for X(3872) J/
Kinematic variables
CM energy difference:
Beam-constrained mass:
2/
2 )()2( JKCMbc ppEm
BK J
BKJ2// cmJK EEEE
B
Bϒ(4S)
Ecm/2
e e
Ecm/2
Mbc
E
Select BK J/BKc1; c1J/
X(3872)?
13.6 ± 4.4 X(3872)J/evts (>4significance)
M(J/)
Bf(XJ/)
Bf(XJ/)=0.14 ± 0.05
Mbc Mbc
Evidence for X(3872) J/reported last summer hep-ex/0408116)
12.4 ± 4.2 evts
B-meson yields vs M()
Br(X3J/)Br(X2J/)
= 1.0 ± 0.5 Large (near max)Isospin violation!!
A virtual (782)?
C=+1 is established
• X J/ only allowed for C=+1• same for X””J/ (reported earlier)• M() for XJ/ looks like a
CDF
JPC possibilities (C=-1 ruled out)
0--
exotic
Violates parity 0-+
(c”)
0++
DD allowed
(c0’)
0+-
exotic
DD allowed
1- -
DD allowed
((3S)) 1-+
exotic
DD allowed
1++
(c1’)
1+-
(hc’)
2- -
(2) 2- +
(c2)
2++
DD allowed
c2’)
2+-
exotic
DD allowed
Angular Correlations
K
J/
J=0J=0X3872
Jz=0
z
Rosner (PRD 70 094023)
Bugg (PRD 71 016006)
Suzuki, Pakvasa (PLB 579 67)
Use 253 fb-1 ~275M BB prs
exploit the excellent S/N
Signal(47 ev)Sidebands
(114/10 = 11.4 ev)
XJ/’J/
0++
l
In the limit whereX(3872), , & J/rest frames coincide:
d/dcosl sin2l
rule out 0++ |cosl|
2/dof = 34/9
0-+
0-+ : sin2 sin2
safe to rule out 0-+
|cos|
|cos|
2/dof=34/9
2/dof=18/9
1++
l
1++: sin2l sin2
K
1++ looks okay!
compute angles inX(3872) restframe
|cosl|
2/dof = 11/9
|cos|
2/dof = 5/9
JPC possibilities (0-+ & 0++ ruled out)
0--
exotic
violates parity
0-+
(c”)
0++
DD allowed
(c0’)
0+-
exotic
DD allowed
1- -
DD allowed
((3S)) 1-+
exotic
DD allowed
1++
(c1’)
1+-
(hc’)
2- -
(2) 2- +
(c2)
2++
DD allowed
c2’)
2+-
exotic
DD allowed
Fits to the M()
DistributionXJ/ has a
q*(2l+1) centrifugal barrierX
J/
q*
q*
M() can distinguish -J/ S- & P-waves
S-wave: 2/dof = 43/39 P-wave: 2/dof = 71/39
q*roll-off
q*3
roll-off
(CL=0.1%)(CL= 28%)
Shape of M() distribution nearthe kinematic limit favors S-wave
Possible JPC values (J-+ ruled out)
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
Search for X(3872)D0D00
Select BK D0D00 events
|E| |E|11.3±3.6 sig.evts (5.6)
Bf(BKX)Bf(XDD)=2.2±0.7±0.4x10-4
Preliminary
D*0D00?
M(D0D00)
X(3872)DD rules out 2++
• 1++ : DD* in an S-wave q*
• 2++ : DD in a D-wave q*5
Strong threshold suppression
Possible JPC values (2++ ruled out)
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++1++
can it be a 1++ cc state?
1++ c1’– Mass is ~100 MeV off
– c1’ J/ not allowed by isospin.
Expect: Bf(c1’J/)<0.1%
BaBar measurement: Bf(XJ/)>4%
3872
-(c1’J/) / (c1’J/)
Expect: ~ 40(X3872J/) / (X3872J/)
Measure: 0.14 ± 0.05
c1’ component of X(3872) is ≤few %
Intriguing fact
MX3872 =3872 ± 0.6 ± 0.5 MeV
mD0 + m D0* = 3871.2 ± 1.0 MeV
lowest masscharmed meson
lowest mass spin=1charmed meson
X(3872) is very near DD* threshold.is it somehow related to that?
D0D*0 bound state (deuson)?
p n D D*
deuteron:
2 loosely bound qqq
color singlets with Md = mp+mn-
deuson:
2 loosely bound qq color
singlets with M = mD + mD* -
attractive nuclear force attractive force??
N. Tornqvisthep-ph/0308277
uc
u
c
X(3872) = D0D*0 bound state?
• JPC = 1++ is favored
• M ≈ mD0 + mD0*
• Maximal isospin violation is natural (& was predicted): |I=1; Iz= 0> =1/2(|D+D*->+ |D0D*0>) |I=0; Iz= 0> =1/2(|D+D*-> - |D0D*0>)
|D0D*0> = 1/2(|10> - |00>)
• (XJ/) < (XJ/) was predicted
Equal mixture of I=1 & I =0
Swanson PLB 598, 197 (2004)
Tornqvist PLB 590, 209 (2004)
Swanson PLB 588, 189 (2004)
X(3872) conclusion
•JPC = 1++
•cc content is small
•matches all(?) expectations for a D0D*0 bound state
C C
u cuca non-qq meson
Are there others?Is the X(3872) a one-of-a-kind curiousity?
or the 1st entry in a new spectroscopy?
Look at other B decays hadrons+J/
BK J/
BK J/
BK J/
BK J/ in Belle
“Y(3940)”M≈3940 ± 11 MeV≈ 92 ± 24 MeV
Mbc Mbc Mbc
S.K. Choi et al hep-ex/0408126to appear in PRL
Y(3940): What is it?
• Charmonium?– Conventional wisdom: J/ should not be
a discovery mode for a cc state with mass above DD & DD* threshold!
• Some kind of -J/ threshold interaction?– the J/is not surrounded by brown
muck; can it act like an ordinary hadron?
J/
Brambilla et al (QWG) hep-ph/0412158
Y(3940): What is it (cont’d)?
• another tetraquark?– M ≈ 2mDs
– not seen in YJ/• ( contains ss)
– width too large??– no exchange for DSDS
s csc
??PRL 93, 041801
M( J/)
Y(3940): What is it (cont’d) ?
• cc-gluon hybrid?– predicted by QCD,– decays to DD and DD* are suppressed (“open-charm” thresh = mD + m D** = 4.3 GeV)
– large hadron+J/ widths are predicted– masses expected to be 4.3 ~ 4.4 GeV
(higher than what we see)
c c
Horn & Mandula PRD 17 898 (1974) + (many) others
Summary• X(3872):
– JPC established as 1++
– cc component is small (≤ few %)– all properties consistent with a D0D*0
bound state u cuc
a non-standard meson
• Y(3940):– No obvious cc assignment– tetraquark seems unlikely– cc-gluon hybrid?
c c
?????
- Lots to do: determine JPC ; find other modes (DD*, DsDs, …?)
Mahalo
Back-up slides
• c2,c0<<c1•X(3872) production much lower than for other Charmonium states:•can set lower limit on B.F.
Can measure absolute B.F.’s of B-K-X0
e+e-B+B-
K-X0
Lower limit on BF(XJ/) > 4.3% @ 90% C.L
244 fb-1
Very clear J/ and c signals N J/=258+- 42N c =266 +-42
c2 c1 c0
J/
Jon ColemanMoriond-QCDMarch 2005
M(J/) look-back plot
Fit cosl with 1++ MC
|cosl|
2/dof=11.9/9