CHARMONIUM

New era(~after 2001)

where I hope to convince you that charmonium still has the potential

to surprise us

This lecture is about the

B-factories

/ KL detection 14/15 lyr. RPC+Fe

Tracking + dE/dx small cell + He/C2H5

CsI(Tl) 16X0

Aerogel Cherenkov cnt. n=1.015~1.030

Si vtx. det. 3 lyr. DSSD

TOF counter

SC solenoid1.5T

8GeV e

3.5GeV e

Cherenkov Detector (DIRC)[144 quartz bars, 11000 PMTs]

Silicon Vertex Tracker (SVT)[5 layers]

Instrumented Flux Return (IFR) [Iron interleaved with RPCs].

CsI(Tl) Calorimeter (EMC)[6580 crystals].

Superconducting Coil (1.5T)

Drift Chamber [40 stereo lyrs](DCH)

e- (9 GeV)

e+ (3 GeV)e+e- → Y(4S)

e+e– → сharmonium CLEO-c BES-IIE=3.0-4.8GeVL~1033/cm2/s

BaBar Belle

E=10.6GeV

L~1033/cm2/s

pp collider CDF D0E ~ 1.8 TeV

¯

Controversal tests of COM modelLeptoproduction at HERA: COM predicts too high x-section

-production at LEP: COM expectation are in a nice agreement with the data

Photoproduction at HERA: COM is ok

Charmonium production in e+e– at E~10GeV

Color-Singlet e+e- J/ cc was estimated to be very small by Kiselev et al. (1994) ~ 0.05 pb should be unobservable even

at high luminosity B-factoriesColor-octet e+e- (cc)8 g J/ g (with Oncc fixed

to Tevatron and others data) should not be large as well (but can be significant around the end-point of J/ momentum) Braaten-Chen (1996)

Color-Singlet e+e- J/ gg is the best candidate! Predicted CS ~1 -2 pb Cho-Leibovich (1996)

was first observed experimentally (although it is not so much surprising, nobody thought about this possibility). CLEO/Argus, 1992: cross section

e+e- J/ ~ 2 pb.

Surprisingly large double charmonium production

Look at the recoil mass against reconstructed J/ using two body kinematics (with a known initial energy)

Mrecoil = (Ecms- E J/ )2 - P J/ 2 )

See all the (narrow) states produced together with J/y. The data shows unexpected charmonia: c, c0, c(2S)

Note: all recoil states are 0±+. C=+1 is expected: C()=–1, C(J/)=–1

experiment

~10*theory

Belle(2002) BaBar (2005)

Double charmonium is not a whole story, in addition, also observed associated production • e+e– J/ D(*+) X• e+e– J/ D0 X

demonstrating large e+e- J/ cc unlike theory expectation

(e+e-→ J/cc)/(e+e-→ J/X) =0.590.140.12

Surprisingly large J/ production with charm mesons

(e+e–→ J/cc)~ 1pb ~10-20 times greater than theory expects

This results do not kill COM, but remove the basis for it:If CSM can not calculate correctly c→J/ fragmentation (as demonstrated by these data), why do we need COM (suggested to resolve discrepancy CSM-data).

Belle(2002)

Back to charmonium spectroscopy

1974-1980, ten charmonium states observed (1.5 per year)1980-2002, no new state found

Potential models successfully describe the charmonium spectrum, annihilation decays and radiative transitions

2002-2007, ~ twelve new charmonium (charmonium-like) states found. Do they fit the potential model?

One more important ingredient: to take into account charmed meson-antimeson pair coupling to charmonium. Important above DD threshold.

H0

H2

Hint ?

Cornell coupled channel model Model of quark pair production in vacuum

D*

D̄

How to identify it?Quantum numbers can be fixed at production:

• In e+e– annihilation (including annihilation after initial state radiation), only the states with quantum number of photon can be produced (JPC=1- -)

• In fusion, only the states with C=+1, J=0,2 are produced

• In double charmonium production e+e– → *→ Xcc1Xcc

2, only if two charmonium can form 1- - (if you know quantum number of one of the states you can say something about accompaning one).

• In B-decays and in hadronic interaction, generally no constrain. P non conservation in weak decays/not understanding of production mechanism.

... Or in “X” decay• Selection rules: angular momentum, P, C conservation in

strong and electromagnetic decays.• The most powerfull tool is to study angular distributions,

depending on JP . It is even more powerful when “X” is found in B decay.

If you find a new charmonium state “X”, than

Observation of hc

(2S) → 0 hc → 0 c

hc

Potential model expectations: M(hc) = centre of gravity of c states =1/9 * [(2*2+1) * M(c2) + (2*1+1) * M(c1) + (2*0+1) * M(c0) ] = 3525.3 ± 0.3 MeV

CLEO 2005

M(hc) = (3524.4 ± 0.6 ± 0.4) MeV

This prediction is independent on the potential. This measurement unfortunately does not check the models.

Observation of c(2S)

c(2S)

observed

• in B decays (c(2S)KSK)

• in e+e- annihilation (inclusive)

confirmed by CLEO & BaBar in

B(KSK)K

e+e- J/c(2S)

the properties are in reasonable agreement with the expectations (mass, total width, -width)

<55MeV

M=263012 MeV/c2

Belle, 2002

M=265410 MeV/c2

Chramonium table below DD threshold is complete!

New unexpected particle

observed in the decay B+(J/)K+ MX=(3872.00.60.5)MeV/c2

MX - MDD* = (0.2 0.7) MeV/c2

narrow: <2.3MeV at 90% CL

decay dynamics: M+- tends to peak around limit (J/ 0 is isospin violating decay)

X(3872) – the first in “X” seriesintroduce new (ugly) particle naming scheme: X, Y, Z ...

Belle, 2003

Everything is surprising:

The B-meson signal depending on M(J/)

M(+–)

Confirmed by CDF,D0,BaBar

Belle

X(3872) is well established, can not be attributed to experimental mistake

At pp collision only ~10% produced from B-decays, others are directly produced (new headache for “production” theory)

¯

more information – more understanding?- X decays to J/, but very rarely (Belle 2004, BaBar 2006). This observation fix CX=+1, and confirm that in the X→J/decay

This only add confusion: if X-charmonium, the radiative decays should be stronger than X→J/transition.- X decays to J/with Br ~ Br (X→J/). This confirms isospin violation.- Fit to M() favours PX=+1. - Angular analysis:

Belle, 2004CDF, 2006 Favours JPC = 1++

JPC=1++ corresponds to c1(23P1) if X-charmonium:- c1’ J/ should be much stronger than c1’ J/ (measured ratio ~0.15, expected ~ 30)- ~100MeV/c2 lighter than expected.

JPC=2–+ c2(11D2): is expected to decay into hadrons (via gg) rather than into isospin violating mode.

Options for X(3872)

1++ is predicted

Vote:Absolute winnerX ≡ D0D*0 molecule 0

5

10

15

20

25

30

Molecule 4-quark Hybrid Others

B±→XK± B0→XKS

MX = M(X from B±) ─ M(X from B0) = (0.22±0.90±0.27)MeV/c2

• No mass splitting expected by tetraquark model Br(B0→X(3872)K0)/Br(B±→X(3872)K±) = 0.94±0.24±0.10

• equal BR for neutral and charged B, is this a big problem for molecular model? Some molecular models predicts this ratio 1/10.

cdc dXd =

cuc uXu =

Tetraquark hypothesisexpects several X states around 3872 with a typical splitting ~ 4-5MeV

Predictions: #1 there should be charged state (difficult to check experimentally)#2 the X-states produced in B0 and B+ are different and should have different masses (this is finally checked in 2007(Belle))

Good agreement between Belle/BaBar, ...but 4 from M(X→J/ψ)

Decay to D0D00

Is this a new state, different from X(3872)? If X(3872) is DD* molecular state with the pole just below the DD* threshold, this observation is not surprising. Such model expects:

X→J/ψ with unresolvable width exactly at the DD* threshold Flatte-like XD0D00 behaviour with a typical “width” of 3MeV

Looking for B XK , XD0D00 (D0D*0 ) Belle 2006, BaBar 2007

One more misterious state Y(3940)

BYK

B0YKS

B0/B

M(J/) (GeV)

Belle, 2004BaBar, 2007

BYK, YJ/

M= 3943 11 13 MeV

tot = 87 22 26 MeV

M= 3914.6 1.9 MeV

tot = 33 5 MeV

+3.8−3.4

+12 −8

The state is well above both DD and DD* thresholds. At least one of these final state is allowed for charmonim. Why it is not seen in any of these final state?

M(J/) (GeV)

c2’ in productionObserved as a peak at MDD~3.930 GeV/c2 in selected events

pt distribution consistent with production

M=393142MeV/c2 =2083MeV

Helicity distribution favors spin = 2 while J=0 disfavored

The observed state is c2’:However, the mass is ~80-100 MeV lighter than expected by potential models

Belle,2005

(2J+1) × B(ZDD)=(1.130.30)keV

M = 3942 ±6 MeV

tot =37 ±12 MeV

+7-6

+26 - 15

D*

D*πD*

D

D

New states in e+e− J/ D(*)D(*)Belle, 2005Belle, 2007

M= 4156 15 MeV

tot = 139 21 MeV

+25−20

+111 −61

Two new states observed, both decay at open charm final states like “normal” charmonium.

X(3940) → DD*

X(4160) → D*D*

Possible assignments are c(3S) and c(4S). But in both cases the masses predicted by the potential models are ~100-150 MeV lower.Theory probably needs more elaborated model to take into account couple channel effects.

Y(4260)→J/

Another enigmatic particle(s)

(2S)

BaBar 2005, CLEO,Belle,2006

e+

e–e–

s=(Ecm-E

)2-p

21–– final state

=

Consistent with BaBarNew state?

Y(4360) consistent with BaBar Y(4660)

NEW

Y(4350)→(2S)

More states?BaBar 2005, CLEO,Belle,2006

e+

e–e–

s=(Ecm-E

)2-p

21–– final state

=

e+e–→J/+– & e+e– → (2S)+–

Peak positions in M(J/) & M((2S)) significanctly different. There is no place in the 1–– charmonium spectrum even for one state...

Y(4260)

PDG 2006

Inclusive cross section arond 4 GeV

In spite of ψ(3770), ψ(4040), ψ(4160), ψ(4415) are know for more 25 years, their parameters M, , ee are quite uncertain: • To fix the parameters we need to know their decays channels (to take into account their interference: if two states decays into the same final state they should interdere, if into different final states their contribution are uncoherent)• How to take into account non-resonance contribution• Need to take into account DD thresholds (~ 50 ...)

The interference is taken into account for the first time (model dependent)Significant difference with fit without interference

Resonance shapes Interference term

Rres=RBW+Rint

arXiv:0705.4500

New fit to the inclusive spectrum

Resonance parameters

BES-II 2007

We need exclusive cross sections e+e−→D(*)D(*) for model independent fit

Exclusive e+e−→D(*)D* cross-sections

D(*)D*

e+

e–e–

s=(Ecm-E

)2-p

21–– final state

=

Belle 2006, CLEO 2007

D*+D*-

D+D*-

(4040)

(4415)

(4160)

Y(4260)

Charged D(*)D*

½ from CLEOc

DD*

D*D*(4160)

Y(4260)

(4040)

Y(4260) signal DD* : hint, but not significant D*D* : clear dip

Observation of the decay (4415)DD

DD non DD*2(2460)

DD*2(2460)

~10σ

DD

e+

e–e–

s=(Ecm-E

)2-p

21–– final state

=

Belle 2007

M(D0+) vs M(D-+) from (4415) regionPositive interference

Non D*2(2460)

contribution is not seen

(4040)

(4160)

(4415)(3770)

DD

+

Contributions to the inclusive cross-section

D*D*

DD*

uds-continuum

+

=

These 4 final states almost saturate inclusive cross section, still many missing f.s. e.g. Ds

(*)Ds(*)

2×

DD

DD

Anything else?

2×

Resonance? in +(2S)

M = (4433±4±2) MeV= (45+18

-13+30

-13) MeV

7.3

K*(890) & K*(1430) excluded

(2S))

M2 (

(2S

)),

(G

eV2 )

M2(K), (GeV2 )K*(890)→K+-

K*(1430)→K+-

???

Dalitz plot for signal events

B → K + (2S), (2S) → ℓ+ℓ–; J/

The first charmonium-like state, for which charmonium assignment is impossible.

Is this a state or threshold effect (cusp)? Tetraquark or meson molecular state? or charmonium-light meson molecule-like state?

Belle,2007

M(M

eV

)

JPC

DD(3770)

c1c2

’c

c

X(3940)

X(4160)

X(3872)

Y(3940)(4040)

(4415)

(4160) Y(4260)

Y(4350)

c0

hc

J/

’

c2’

Trying to put all new state in the table

Z+(4440)

Y(4660)Placed here by JPC

New charmonium /charmonium-like states:

• 2 new states below open charm threshold: hc and c(2S) are

well identified and well fit the potential model prediction

• 3 new states (c2(2P), X(3940), X(4160)) behave like a

normal charmonium, but all three are significantly lighter than expected by potential model. This can be corrected by modifying the charmonium-charm mesons interaction.• 1 state X(3872) is very probably to be a D0D*0 molecular state (not a big exotics) with probably a mixture of c1(1P),

c1(2P). At least there is no better explanation...

• 1 state Y(3940) is probably a normal charmonium - experimental information is still poor. The only • 4 states in 1–– spectrum are the most problematic. The best quantative prediction is that these states are hybrids (ccg) (expected by LQCD calculation in this mass region). Note of the Voloshin’s explanation (lecture on the first day of the school).• Charged charmonium-like state Z+(4430) may be a tetraquark. Note of the Voloshin’s explanation