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