T. BarnesORNL / UTennSLAC HEP Seminar23 Feb. 2006

The XYZs of cc:X(3943), Y(3943), Z(3931) and Y(4260)

1. Good old charmonium.

2. The new states:

3S cc? 2P cc? cc hybrids?

How to test these possibilities.

New theor. results mainly abstracted from:T.Barnes, S.Godfrey and E.S.Swanson, hep-ph/0505002, PRD72, 054026 (2005).

1. Good old charmonium.

QCD flux tube (LGT, G.Bali et al.;hep-ph/010032)

LGT simulation showing the QCD flux tube

Q Q

R = 1.2 [fm]

“funnel-shaped” VQQ(R)

Coul. (OGE)

linear conft.(str. tens. = 16 T)

Color singlets and QCD exotica “confinement happens”.

Physically allowed hadron statesPhysically allowed hadron states (color singlets) (color singlets) (naïve, (naïve, valence)valence)

qq

q3 Conventional quark modelmesons and baryons.

q2q2, q4q,…

multiquarks

g2, g3,…

glueballs

maybe 1 e.g.

qqg, q3g,…

hybrids

maybe 1-3 e.g.s

100s of e.g.s

“exotica” :ca. 106 e.g.s of (q3)n, maybe 1-3 others X(3872) = DD*!

(q3)n, (qq)(qq), (qq)(q3),…

nuclei / molecules

(q2q2),(q4q),…

multiquark clusters

dangerouse.g.

_

Basis state mixing may be very important in some sectors.

qq mesons states

The quark model treats conventional mesons as qq bound states.

Since each quark has spin-1/2, the total spin is

Sqq tot = ½ x ½ = 1 + 0

Combining this with orbital angular momentum Lqq gives states

of total Jqq = Lqq spin singlets Jqq = Lqq+1, Lqq, Lqq-1 spin triplets

Parity Pqq

= (-1) (L+1)

C-parity Cqq

= (-1) (L+S)

qq mesons quantum numbers

1S: 3S1 1 ; 1S

0 0 2S: 23S

1 1 ; 21S

0 0 …

1P: 3P2 2 ; 3P

1 1 ; 3P

0 0 ; 1P

1 1

2P …

1D: 3D3 3 ; 3D

2 2 ; 3D

1 1 ; 1D

2 2

2D …JPC forbidden to qq are called “JPC-exotic quantum numbers” :

0

; 0 ; 1

; 2 ; 3

…

Plausible JPC-exotic candidates =

hybrids, glueballs (high mass), maybe multiquarks (fall-apart decays).

The resulting qq NL states N2S+1LJ have JPC =

The (higher) cc spectrum

Pre-dawn, a lava field near Carrizozo, New Mexico.

Charmonium (cc)A nice example of a QQ spectrum.

Expt. states (blue) are shown with the usual L classification.

Above 3.73 GeV:Open charm strong decays(DD, DD* …):broader statesexcept 1D

2 22

3.73 GeV

Below 3.73 GeV: Annihilation and EM decays.

, KK* , cc, , ll..):narrow states.

Minimal quark potential model physics:

OGE + linear scalar confinement;

Schrödinger eqn (often relativized) for wfns.

Spin-dep. forces, O(v2/c2), treated perturbatively.

Here…

Contact S*S from OGE;Implies S=0 and S=1 c.o.g. degenerate for L > 0.(Not true for vector confinement.)

s = 0.5538

b = 0.1422 [GeV2]m

c = 1.4834 [GeV]

= 1.0222 [GeV]

Fitted and predicted cc spectrumCoulomb (OGE) + linear scalar conft. potential

model blue = expt, red = theory.

S*S OGE

L*S OGE – L*S conft, T OGE

Fitted and predicted cc spectrumCoulomb (OGE) + linear scalar conft. potential

model NR model (LHS) adjacent to GI model (RHS).

S*S OGE

2P

1F

NRGI

cc from LGT

exotic cc-H at 4.4 GeV

cc has returned.

Small L=2 hfs.

A LGT e.g.: X.Liao and T.Manke, hep-lat/0210030 (quenched – no decay loops).Broadly consistent with the cc potential model. No cc radiative or strong decay predictions from LGT yet.

Strong decays

Strong widths of cc resonances

3770

4040

4160

4415

What are the total widths of cc states above 3.73 GeV?

(These are dominated by open-flavor decays.)

< 2.3 MeV

23.6(2.7) MeV

52(10) MeV

43(15) MeV

78(20) MeV

PDG values

X(3872)

Experimental R summary (2003 PDG)Very interesting open theoretical question:Do strong decays use the 3P

0 model decay mechanism

or the Cornell model decay mechanism or … ?

br

vector confinement??? controversial

ee, hence 1 cc states only.

How do open-flavor strong decays happen at the QCD (q-g) level?

“Cornell” decay model:

(1980s cc papers)(cc) (cn)(nc) coupling from qq pair production by linear confining interaction.

Absolute norm of is fixed!

An alternative strong decay modelThe 3P

0 decay model: qq pair production with vacuum quantum numbers.

L I = g

A standard for light hadron decays. It works for D/S in b1 .

The relation to QCD is obscure.

After restoring this “p3 phase space factor”, the BFs are:

D0D0 : D0D*0 : D*0D*0

One success of strong decay models

An historical SLAC puzzle explained:the weakness of (4040) DD

e.g. DD molecule?

famous nodal suppression of a 33S

1 (4040) cc DD

std. cc and D meson SHO wfn. length scale

Theor R from the Cornell model.Eichten et al, PRD21, 203 (1980): 4040

DD

DD*

D*D*

4159

4415

partial widths [MeV](3P

0 decay model):

DD = 0.1 DD* = 32.9 D*D* = 33.4 [multiamp. mode]D

sD

s = 7.8

D*D* amplitudes(3P

0 decay model):

1P1 = 0.034

5P1 = 0.151 = 1P

1

5F1

= 0

2. The new XYYZ states:

3S cc? 2P cc? cc hybrids?

How to test these possibilities.

Expt. preview, M, and modes, X(3943),X(3943), Y(3943), Y(3943), Z(3931): Z(3931):

J/

cc spectrum, potential models (dashed: nonrel L, Godfrey-Isgur R) vs data

Possible new cc states at these masses! Z;X,Y;Y

2P or not 2P?

Reminder:Three as yet unknown 1D states.Predicted to have < 1 MeV!

BGS, hep-ph/0505002, PRD72, 054026 (2005).

cc spectrum, potential models (dashed: nonrel L, Godfrey-Isgur R) vs data

Possible new C=(+) cc states from ee !

2P or not 2P?

c’

0

c

X(3943)

An interesting new charmoniumproduction mechanism!

Allows access to C=(+) cc states in ee w/o using .

No or !?

X(3943)

[ref] = Belle, hep-ex/0507019, 8 Jul 2005. n.b. Eichten: X(3943) may be the 31S0 cc

c’’.

Strong Widths: 3P0 Decay Model

33S1

74 [MeV]

31S0

80 [MeV]

3S

DDDD*D*D*D

sD

s

X(3872)

Maybe not 2P?X(3943) = 31S

0

c” ?

(Eichten)

X(3943)

52(10) MeV

Back to the main theme:

Comparing expt. with theory for 2P cc states.

1st Strong decays (vs. expt.)

2nd EM ( and transitions)

Trivial observations for 2P cc open-charm strong decays:

Thresholds

DD 3.73 GeVDD* 3.87 GeV

(Ds D

s 3.94 GeV - small)

2’ 2++ 23P

2 DD, DD*

1’ 1++ 23P

1 DD*

0’ 0++ 23P

0 DD

hc’ 1+- 21P

1 DD* but C = (-)

Detailed 2P cc predictions…

J P-allowed D, D* modes (M < D*D*)

Looking for both DD and DD* is a good filter!

n.b. JP = 1+ DD* final states have both S and D amps.

2P cc Strong Widths: 3P0 Decay Model

DDDD*D

sD

s

2P23P

2 80 [MeV]

23P1

165 [MeV]

23P0

30 [MeV]

21P1

87 [MeV]

(assuming NR ccpotential model masses;BGS, hep-ph/0505002, PRD72, 054026 (2005).)

Y(3943) B KY(3943), Y J/

[ref] = Belle, PRL94, 182002 (2005).

Y(3943) = 23P1 cc? (Too light for cc-H.)

Expt for Y(3943): B KY(3943), Y J/ = 87 +/- 22 MeV1++ cc J/ is unusual; cc virtual DD* e.g. -> J/ ?n.b.

IS seen in B decays

Theory for 23P1(3943):

= 135 MeV

A strong DD* mode ?The only open-charm mode?

theoryexpt.

tot

Y(3943)

Z(3931) Z(3931) DD

[ref] = Belle, hep-ex/0507033, 8 Jul 2005.

Z(3931) = 23P2 cc ? (suggested by Belle)

Expt for Z(3931): Z(3931) -> DD MeV * BDD

= keV

thy

expt

tot

Theory for 23P2(3931):

= 47 MeV DD*/DD = 0.35 * BDD

= 0.47 keV

( from T.Barnes, IXth Intl. Conf.

on Collisions, La Jolla, 1992.)

The crucial test of Z(3931) = 23P

2 cc :

DD* mode ?

in http://web.utk.edu/~tbarnes/website/Barnes_twophot.pdf

Z(3931)

Z(3931)

Another possibility for Z(3931)???Another possibility for Z(3931)???

Expt for Z(3931): -> Z(3931) -> DD = 20 +/- 8 +/- 3 MeV * BDD

= 0.23 +/- 0.06 +/- 0.04 keV

Theory for 23P0(3931):

: DD only o.c. mode, theor. tiny! (node) Annih. dominates? Recall

ca. 10 MeV.

ca. 2 keV (not calc.)

* BDD << 2 keV.

EM transitions

(How one might make 2P cc states.)

What radiative partial widths do we expect from various initial 1 cc states to 2P cc states?

Strong Widths: 3P0 Decay Model

X(3872)33S

1 74 [MeV]

31S0

80 [MeV]

3S

DDDD*D*D*D

sD

s

52(10) [MeV]

E1 Radiative Partial Widths

3S -> 2P 33S1 23P

2 14 [keV]

33S1 23P

1 39 [keV]

33S1 23P

0 54 [keV]

31S0 21P

1 105 [keV]

3S -> 1P 33S1 3P

2 0.7 [keV]

33S1 3P

1 0.5 [keV]

33S1 3P

0 0.3 [keV]

31S0 1P

1 9.1 [keV]

2D 23D3

148 [MeV]

23D2

92 [MeV]

23D1

74 [MeV]

21D2

111 [MeV]

DDDD*D*D*D

sD

s

DsD

s*

78(20) [MeV]

Strong Widths: 3P0 Decay Model

E1 Radiative Partial Widths

2D -> 1P23D

3 3P

2 29 [keV]

23D2 3P

2 7 [keV]

3P1

26 [keV]

23D1 3P

2 1 [keV]

3P1

14 [keV]

3P0

27 [keV]

21D2 1P

1 40 [keV]

2D -> 1F

23D3 3F

4 66 [keV]

3F3

5

[keV] 3F

2 14

[keV]

23D2 3F

3 44 [keV]

3F2

6 [keV]

23D1 3F

2 51 [keV]

21D2 1F

3 54 [keV]

2D -> 2P23D

3 23P

2 239 [keV]

23D2 23P

2 52 [keV]

23P1

298 [keV]

23D1 23P

2 6 [keV]

23P1

168 [keV]

23P0

483 [keV]

21D2 21P

1 336 [keV]

Y(4260)

cc spectrum, potential models (dashed: nonrel L, Godfrey-Isgur R) vs data

Possible 1 state Y(4260).Note no plausible cc assignment exists.A 1 charmonium hybrid??

Y(4260) ee Y(4260)ISR

, Y J/

log scale

Not seen in R.Hmmm?!

[ref] = BaBar, PRL95, 142001 (2005).

Y(4260) ? B K Y(4260), Y J/

[ref] = BaBar, hep-ex/0507090 (21 Jul 2005).

cc-hybrids, theory

Characteristics of cc-hybrids.

(folklore, mainly abstracted from models, some LGT)

States

(flux-tube model):

The lightest hybrid multiplet should be a roughly degenerate set containing3 exotic and 5 nonexotic JPC;

0, 1, 2, 0, 1, 2, 1, 1

Mass ca. 4.0 – 4.5 GeV, with LGT preferring the higher range.

The 1 should be visible in ee but with a suppressed width. (Hybrid models for different reasons predict

cc(r=0) = 0, suppressing

ee .)

Decays

(flux-tube model and f-t decay model):

Dominant open-charm decay modes are of S+P type, not S+S. (e.g. DD1 not DD or DD*).

n.b. 1(1600) ’ argues against this model.

LGT(UKQCD):

Closed-charm modes like cc-H cc + light mesons are large! (Shown for bb-H; (bb) is preferentially P-wave, and “light mesons” = scalar .)

p ’p

E.I.Ivanov et al. (E852)PRL86, 3977 (2001).

1(1600)

exotic reported in ’

’is a nice channel because nn couplingsare weak for once (e.g. the a

2(1320) noted here).

The reported exotic P-wave is dominant!

The (only) strong JPC-exotic H candidate signal.

cc and cc–H from LGT

exotic cc-H at 4.4 GeV

Small L=2 hfs.

A LGT cc-sector spectrum e.g.: X.Liao and T.Manke, hep-lat/0210030 (quenched – no decay loops)Broadly consistent with the cc potential model. No LGT cc radiative or strong decay predictions yet.

n.b. The flux-tube model of hybrids has a lightest multiplet with 8 JPCs;3 exotics and 5 nonexotics, roughly degenerate: (0,1,2) , 1,1Y(4260)?

PRD52, 5242 (1995).

Early cc-H mass estimates:

cc-H mass result, 1995 BCS flux tube model calculation ([ref] on prev. slide):

QQ-H closed-flavor decays from LGT:

How to test a cc-hybrid assignment, esp. for Y(4260) :

1. Existence

2. Establish the multiplet

3. Decays

How to test a cc-hybrid assignment, esp. for Y(4260):

1. Existence

Make sure it’s really there. Beware “low-“stuff. Is Y(4260) a real effect?

2. States and Partner States (fill in the multiplet)

Mass ca. 4.0 – 4.5 GeV, with LGT preferring the higher range.

Confirm that no cc states with the same JPC are expected at this mass.

Identify JPC partners of the hybrid candidate nearby in mass. (The most convincing evidence: partners, especially JPC exotics.)

The f-t model expects: 0, 1, 2, 0, 1, 2, 1, 1

The 1 should be visible in ee but with a suppressed width.

3. Decays

Decay modes may be distinctive. BFs and decay amplitudes are very interesting…Some calculations suggest S+P, not S+S, open-charm modes.LGT suggests exotic bb-H

b (

S is large.

The models or LGT assumptions may be wrong (note

1(1600) ’ is S+S).

Summary, conclusions, suggestions, re expt:

X(3943), Y(3943), Z(3931) and Y(4260) …

1. X(3943) as 31S0

c’’, cc ? DD*-only checks, may be a bit small..

Just measure J P !!! (also Y and Z!)

2. If Y(3943) is the 23P1

1’, one expects a large DD* mode, and no DD.

3. Z(3931) DD vs. DD* can distinguish 0’ from

Belle’s suggested 2’.

…

Summary, conclusions, suggestions, re expt:

Y(4260) …

4. Y(4260) as hybrid? No new cc 1 expected near this mass: if it exists it’s already something unusual.

Theory folklore says hybrids prefer S+P modes, UKQCD says + light meson(s).

Best approach would be to search for it in all accessible o.c. and c.c. modes. ee DD, DD*, D*D*, DD

0*, DD

1*; J/any other (cc) + light meson mode.

(Close and Page, hep-ph/0507199v2, 30 Sep 2005 gives a detailed list of modes)

Summary, conclusions, suggestions, re expt (cont.):

X(3943), Y(3943), Z(3931) …

5. (For Beijing I guess…) You can find all three 23P

J cc states using

andDD, DD*.

All three E1 rad BFs of the are ca. 0.5 * 10-3. These could show whether the X,Y,Z (3.9) are 2P cc as speculated.

The End