# Presentation: 566159

## Recent developments in charm meson spectroscopy: Chaos, confusion and craziness.

- Basic hadronics
- Making charmonium
- Spectrum of charmonium
- Exciting new developments (2003-present):
- D*s0, Ds1, X(3872),...(X,Y,Z), Y(4260), Z(4430).

- Theory abstracted from T.Barnes, S.Godfrey and E.S.Swanson, PRD72, 054026 (2005).
-                                               For BABAR, BELLE, BES, CLEO, GSI, ... :
- All 40 c_c_ states expected to 4.42 GeV, all 139 of their open flavor strong modes and partial widths,
- all 231 o.f. strong decay amplitudes, all 153 E1 and (some) M1 EM widths.  Phew.

- Ted Barnes
- BNL Seminar
- 18 Mar. 2008

## 1. Basic hadronics.

##    Color singlets and QCD exotica
       “confinement happens”.

- 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” VQ_Q_(R)

- Coul.
- (OGE)

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

*   **Color singlets and QCD exotica*
*       “**confinement happens”.*

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

- qq_** **_

- q3

- Conventional quark model
- mesons and baryons.

*100s of e.g.s*

- “exotica” :

- _

- Basis state mixing may be
- very important in some sectors.

## qq mesons                            states

**The quark model treats conventional mesons as ****q**_**q**_** bound states.**
**Since each quark has spin-1/2, the total spin is**
-                           **S****q**_**q**_** tot**** = 1⁄2 x 1⁄2 = 1 + 0**
**Combining this with orbital angular momentum ****L****q**_**q**_** ****gives states**
**of total **
-                                       **J****q**_**q**_** = L****q**_**q**_                         **spin singlets**
-                       **J****q**_**q**_** = L****q**_**q**_**+1, L****q**_**q**_**, L****q**_**q**_**-1**          **spin triplets**

##            Parity  Pqq = (-1) (L+1)            C-parity  Cqq = (-1) (L+S)

- q_q_ mesons             _quantum numbers_

- 1S: 3S1 **1 ******** ****** ;   1S0  **0 ******** ******       2S: 23S1 **1 ******** ****** ;  21S0  **0 ******** ******   ...
- 1P: 3P2 **2 ****** ;  3P1 **1 ****** ; 3P0 **0 ****** ; 1P1  **1 ******** ******2P ...
- 1D: 3D3 **3 ****** ; 3D2 **2 ****** ; 3D1 **1 ****** ; 1D2  **2 ******** ******2D ...

- JPC forbidden to q_q_ are called  “**J****PC****-exotic quantum numbers**” :
**    ****0 ****- -************    0 ****+ -******   ** 1 ****- +****** **   2 ****+ -****** **  3 ****- +******** ** ...
-                           **Plausible ****J****PC****-exotic**** ****candidates = **
**hybrids****, glueballs** (high mass), maybe **multiquarks**** **(fall-apart decays).

**The resulting q**_**q**_**  NL states  N****2S+1****L****J****  have**  **J****PC**  **=**

## 2. Making charmonium.

## How to make charmonium?

- Hit things together.

**e********e******** collisions **
- (as in Beijing, Cornell, SLAC)
*“**clean” theoretically but small cross sections*
*and restricted quantum numbers*
**hadron-hadron collisions**
- e.g. **p**_**p**_
- Fermilab (past),
- GSI/Darmstadt (start 2013 AD)
*messy theoretically, large backgrounds, *
*less restricted quantum numbers *

- ...some Feynman diagrams:

## ee collisions (1):

- The traditional approach: s-channel annihilation.
- Restricted to  **J****PC**** = 1 ****** .      = O(2).
- (May then use hadronic or radiative transitions to reach other states.)

- e

- e

****

****

- hadrons

## ee collisions (2):

- “**Two-photon collisions**”.
- Forms positive C-parity charmonia.  (esp. JPC = 0 ,  0 , 2 ).
- Quite small cross sections,  = O(4),  so
- requires high intensity ee beams.

## ee collisions (3):

- Surprisingly effective for making charmonia.
- The source of several recent discoveries in this field.

- “**B factories**”

**b**_**b**_

## pp collisions :

- Used at Fermilab (E760 and E835).
- Planned for GSI/Darmstadt (PANDA facility).

## 3. The spectrum of charmonium.

## Charmonium  (cc)

*Charmonium  (c*_*c*_*)*
- A nice example of a Q_Q_ spectrum.
- Expt. states (blue) are shown with the usual L classification.

- Above 3.73 GeV:
- Open charm strong decays
- (D_D_, D_D_* ...):
- broader states
- except 1D2 22

_*3.73 GeV*_

- Below 3.73 GeV:
- Annihilation and EM decays.
- , KK* , c_c_, , ll..):
- 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...

## Fitted and predicted cc spectrum

- s  = 0.5538
- b   = 0.1422 [GeV2]
- mc = 1.4834 [GeV]
-    = 1.0222 [GeV]

**Fitted and predicted c**_**c**_** spectrum**
**Coulomb (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 spectrum

**Fitted and predicted c**_**c**_** spectrum**
**Coulomb (OGE) + linear scalar conft. ****potential model**** **
- blue = expt, red = theory.

- S*S OGE

- L*S OGE – L*S conft,
-   T   OGE

- Two narrow states are expected,
- with JPC =  2 and  2.
- The 1D multiplet is theoretically
- close to degenerate, near the
- D(3770).

## cc from LGT

************ exotic c_c_-H at 4.4 GeV

-  c_c_ 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 c_c_ potential model.
- No c_c_ radiative or strong decay predictions from LGT yet.

## Best recent LQCD ref for ccbar and cc-H spectroscopy:

- Best recent LQCD ref for c_c_bar and c_c_-H spectroscopy:
**“****Charmonium excited state spectrum in lattice QCD.”**
- J.J.Dudek, R.G.Edwards, N.Mathur and D.G.Richards, **arXiv:0707.4162** [hep-lat], **Phys.Rev.D77:034501,2008**.

- Results for c_c_ still rather difficult
- to distinguish from quark model.
- Ambiguity in the 1 exotic noted.
- (However other exotics again appear
- around 4.5 GeV.)

- (J   spectrum)

- M [MeV]

##  End of 

- Introduction to c_c_

## 4. The new “XYZ” states:

- 2P c_c_?  3S c_c_?  Molecules?  c_c_ hybrids?
- Nonresonant enhancements?  Experimental  errors?
- How to test these possibilities?

## “Selections from...”  

**“****Selections from...”  **
**(Godfrey and Olsen review, list of new states):**

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

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

- 2P or not 2P?

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

## D*s0 (2317)  and  Ds1(2457)

**c**_**s**_** mesons or DK molecules?**
**(or both)**

-          ... but first, the first of the new discoveries:
-        new, unexpected, very long-lived mesons in the c_s_ sector!

## ee collisions (3):

- Surprisingly effective for making charmonia.
- The source of several recent discoveries in this field.

- “**B factories**”

## Where it all started.               BABAR:   D*s0(2317)+  in  Ds+ 0

- Where it all started.               BABAR:   **D*********s0****(2317)****+**  in  Ds+ ****0

- D.Aubert et al. (BABAR Collab.),
- PRL90, 242001 (2003).

- M = 2317 MeV (2 Ds channels),
-  < 9 MeV (expt. resolution)

- (Theorists expected L=1 **c**_**s**_ states, e.g. JP=0+, but with a LARGE width and at a much higher mass.)   ...

- “Who ordered that !?”
-                  I.I.Rabi, about the ******-**

- Since confirmed by
- CLEO, Belle and FOCUS.

## And another!                      CLEO:      Ds1(2460)+  in  Ds*+ 0 

- And another!                      CLEO:      **D****s1****(2460)****+**  in  Ds*+ ****0

- Since confirmed by BABAR and Belle.
- M = 2457 MeV.

- D.Besson et al. (CLEO Collab.),
- PRD68, 032002 (2003).

- M = 2463 MeV,
-  < 7 MeV (expt. resolution)

- A JP=1+partner of the  0+ D*s0(2317)+ **c**_**s**_ ?

## What caused large downwards

- (Godfrey and Isgur potential model.)

- Prev. (narrow) expt. states in gray.

**DK threshold**

- mass shifts? Mixing with 2 meson
- continuum states? (Believed true.)

## L’oops

-  [ J/  -  M1M2  -  J/
- 3P0 decay model,
- std. params. and SHO wfns.

- M1M2               M [J/]         PM1M2 [J/]

- DD            -   23.  MeV       0.021

- DD*          -   83.  MeV       0.066

- D*D*       - 132.  MeV       0.094

- DsDs          -   21.  MeV       0.015

- DsDs*       -   76.  MeV       0.048

- Ds*Ds*      - 123.  MeV       0.072

-     famous 1 : 4 : 7 ratio  DD : DD* : D*D*

- Sum =      - 457.  MeV        Pc_c_ =  69.%

**VERY LARGE**** ****mass shift**** **
- and large non-cc component!

- Can the QM really accommodate such large mass shifts??? Other “c_c_” states?

## L’oops

-    [ c_c_  -  M1M2  -  c_c_
-          3P0 decay model,
- std. params. and SHO wfns.

***Loops produce a roughly state-independent overall negative mass shift ! ****** ***

## L’oops

-    [ c_c_  -  M1M2  -  c_c_
-          3P0 decay model,
- std. params. and SHO wfns.

***Loop mass shifts of states within L,S c***_***c***_*** multiplets are analytically identical if the initial masses are equal, if you sum over  multiplets of loop spin states! ***
*(A theorem in:) *
***“******Hadron Loops: General Theorems and Application to Charmonium”***
*T.Barnes and E.S.Swanson, *arXiv:0711.2080 [hep-ph] (Nov.2007)

## X(3872)

**a charmed meson molecule?**

## Fitted and predicted cc spectrum

**Fitted and predicted c**_**c**_** spectrum**
**Coulomb (OGE) + linear scalar conft. ****potential model**** **
- blue = expt, red = theory.

- S*S OGE

- L*S OGE – L*S conft,
-   T   OGE

- Two narrow states are expected,
- with JPC =  2 and  2.
- The 1D multiplet is theoretically
- close to degenerate, near the
- D(3770).

## X(3872) from KEK

****************************************J** **************

- D_D_*MeV** **

- Accidental agreement?
- X = c_c_  (2 or 2 or ...),
- or a DD* molecule?

-  MeV

- Alas the known****  =  **3****D****1**** **** **c_c_.
**If** the X(3872) is 1D c_c_,
- an L-excited multiplet is split much more than expected assuming
- scalar confinement.

- n.b.D_D_*MeV

- MeV

**Belle** **Collab.** K.Abe et al, hep-ex/0308029;
- S.-K.Choi et al, hep-ex/0309032, PRL91 (2003) 262001.

- X(3872) from KEK

## X(3872) confirmation (from Fermilab)

- n.b. most recent **CDF II**:
- M =**  3871.3 **pm** 0.7 **pm** 0.4 **MeV

**CDF II Collab.**
- D.Acosta et al, hep-ex/0312021,
- PRL.

- OK, it’s real...
- n.b. ***molecule***.ne.***multiquark***

- X(3872) also confirmed by
**D0** **Collab.** at Fermilab.
- Perhaps also seen by **BaBar**

## The trouble with multiquarks:       “Fall-Apart Decay”     

- (**actually not a decay at all**: no HI)**     **

**Multiquark** models found that
- most channels showed short distance
- repulsion:
**E(cluster) > M****1**** + M****2****.**
**Thus no bound states.**
**Only 1+2 repulsive scattering. **

**nuclei and hypernuclei**
**weak int-R attraction allows **
**“****molecules”**

**E(cluster) < M****1**** + M****2****, **
**bag model:**
**u****2****d****2****s****2**** H-dibaryon, M****H**** - M******** =  ******** 80 MeV. **
- n.b. hypernuclei exist, so this H was wrong.

**Exceptions:**

- VNN(R)
- 2mN

- R

- R

- “V(R)”

- 2m

**Q****2**_**q**_**2****  (Q = b, c?)**

**2)**

**1)**

**3)**

- Heavy-light

## X(3872) 

**Belle** **Collab.** K.Abe et al, hep-ex/0308029;
- S.-K.Choi et al, hep-ex/0309032, PRL91 (2003) 262001.

****************************************J ************

- D_D_*MeV** **

- Accidental agreement?
- X = c_c_ 2 or 2 or ...,
- or a **molecular** (DD*) state?

-  MeV

-   =  3D1  c_c_.
- If the X(3872) is 1D c_c_,
- an L-multiplet is split much more than expected assuming
- scalar conft.

- n.b.D_D_*MeV

- MeV

- Charm in nuclear physics???

## XMeV

- This possibility is suggested by the similarity in mass,

- N.A.Tornqvist, PRL67, 556 (1991); hep-ph/0308277.
- F.E.Close and P.R.Page, hep-ph/0309253, PLB578, 119 (2004).
- C.Y.Wong, hep-ph/0311088.
- E.Braaten and M.Kusunoki, PRD69, 074005 (2004).
- E.S.Swanson, PLB588, 189 (2004); PLB589, 197 (2004).

- n.b. The suggestion of charm meson molecules dates back to 1976:
- (4040) as a D*D* molecule;
- (Voloshin and Okun; deRujula, Georgi and Glashow).

- XMeV
- D_D_*MeV

- n.b.2 Could the signal simply be a cusp due to new DD* channels opening?

## J“”

- _Interesting prediction of molecule decay modes:_
- E.S.Swanson: **1******  **D****o****D*****o**** molecule**  - ***maximally isospin violating!***
- with additional comps. due to rescattering.

- J“”

- J

- Predicted total width *ca.* = expt limit (2 MeV).
- Very characteristic _**mix of isospins**_: comparable J andJ“”decay modes expected. **Appears to be confirmed experimentally!**
- Nothing about the X(3872) is input: this all follows from OE and C.I.

## Z(3930)

**a 2****3****P****2**** charmonium state?**

## ee collisions (2):

- “**Two-photon collisions**”.
- Forms positive C-parity charmonia.  (esp. JPC = 0 ,  0 , 2 ).
- Quite small cross sections,  = O(4),  so
- requires high intensity ee beams.

## Z(3931)

**Z(3931)**

****** ********  ****Z(3931)**** ********  D**_**D**_

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

## tot

**Z(3931) = 2****3****P****2**** c**_**c**_** ? ****  **(suggested by Belle)

- Expt for Z(3931):   Z(3931) -> DD
-   MeV
-  * BDD  =   keV

- thy

- expt

- tot

- Theory for **2****3****P****2****(**_**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) = 2****3****P****2**** c**_**c**_** : **
**DD* mode ************?**

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

**Z(3931)**

## X(3940)

**and double charmonium production**

## ee collisions (5):   Double charmonium production. 

- The traditional approach, s-channel annihilation, but can now make C=(+) charmonia!
-                                                                                                               **J****PC**** =** **J****P******

- J/

- C=(+)  c_c_

## X(3943)

- c’

- 0

- c

**X(3943)**

- An interesting new charmonium
- production mechanism!
- Allows access to C=(+) c_c_ states
- in ee w/o using  .

- No or    !?

**X(3943)**

- [ref]  = Belle, hep-ex/0507019, 8 Jul 2005.

- n.b. Eichten: **X(3943)** may be the 31S0 c_c_ c’’.

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

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

- Possible new **C=(+)** c_c_ states
- from ee !

- 2P or not 2P?

## Y(4260)

**a charmonium hybrid?**

## p  ’p

************

- p  **’**p

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

****1(1600)****
-  exotic reported in  **’**

******’**is a nice channel because n_n_ couplings
- are weak for once (*e.g.* the a2(1320) noted here). **The reported ****exotic P-wave**** is dominant!**

**The (only) strong J****PC****-exotic H candidate signal.**

## ee collisions (6):   Initial state radiation (ISR)

- The traditional approach, s-channel annihilation, but **can use higher energy beams.**
- Still restricted to **J****PC**** = 1 ****** .

- J/

## Y(4260)

**Y(4260)**

*e**e*  Y(4260)**ISR**,  Y *J*/

- log scale

- Not seen
- in R.
- Hmmm?!

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

**closed-flavor **
**decay mode !?**

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

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

- Possible 1 state **Y(4260)****.**
- Note no plausible c_c_
- assignment exists.
- A 1 charmonium hybrid??

## cc and cc–H from LGT

************ exotic c_c_-H at 4.4 GeV

- Small
- L=2 hfs.

- A LGT c_c_-sector spectrum e.g.:  X.Liao and T.Manke,
- hep-lat/0210030  (quenched – no decay loops)
- Broadly consistent with the c_c_ potential model.
- No LGT c_c_ 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,**1******
- **Y(4260)?**

## 1. Confirm existence 

- 1. Confirm existence
- 2. Establish the multiplet, including **J****PC**** ****exotics**!
- 3. Unusual decays (if not exotic)

## Y(4360), Y(4660)

**Y(4360), Y(4660)**

**Y(4260)**

- Prev.   state in
*e **e *  J

- New  states in
*e **e *  ’

**X.L.Wang et al, PRL99, 142002 (2007).**

**BaBar; Belle, CLEO**

**Belle shown**

## Z(4430)

**charged charmonium???**

**The latest craziness...**

##  charge requires ccud quark content. 

**BELLE Collab. 0708.1790v1 (14 Aug. 2007)**

**Z(4430)**

-  charge requires c_c_u_d_ quark content.
**Not c**_**c**_**!**
**n.b. At D*(2010) D****1****(2420) threshold.**

## We discussed some of the exciting new discoveries:
D*s0, Ds1    light, long-lived cs + ... mesons
X(3872)    DD* molecule
Z(3940)    new 2P 2++ cc in 
X(3930)    new 2P or 3S C=(+) cc (?) state
Y(4260), Y(4350), Y(4660)    
               charmonium hybrids?
Z(4430)   “charged charmonium”??  D*D1 molecule?
...and new production techniques: ISR and double cc production. 

This is an exciting time for charm spectroscopy, with many topics for 
both experimenters and theorists to study!
                                                                 The End...  Thank you!

- D*s0, Ds1    light, long-lived c_s_ + ... mesons
- X(3872)    DD* molecule
- Z(3940)    new 2P 2++ c_c_ in 
- X(3930)    new 2P or 3S C=(+) c_c_ (?) state
- Y(4260), Y(4350), Y(4660)
-                charmonium hybrids?
- Z(4430)   “charged charmonium”??  D*D1 molecule?
- ...and new production techniques: ISR and double c_c_ production.
- This is an exciting time for charm spectroscopy, with many topics for
- both experimenters and theorists to study!
-                                                                  *The End...  Thank you!*

*Conclusions*

## END / EXTRAS

## 3.b. Strong decays

## Strong decays of charmonia

- There are two main types of c_c_ strong decays. Neither is well understood.
- I. c_c_ annihilation.
- (c_c_)  gluons (?)  light hadrons
- II. Open flavor decays. (Dominant if allowed.)
- (c_c_)  (c_q_) + (q_c_) 
- Theorists have simple ideas about these strong decays and
- rough models for them but not much more. Some simple ideas
- like pQCD fail dramatically.

- This is a wide open field for the smart young theorist.

## Some brief comments about cc-annihilation strong decays. 

- These are secondary strong decay processes that are only dominant
- for states below open-charm threshold. (M < 2MD = 3.73 GeV.)

- Estimating total annihilation widths by counting gluon vertices
- is a standard rough guide:

## Strong decays (open flavor)

## Total widths of cc resonances...

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

**What are the total widths of c**_**c**_** states above 3.73 GeV?**
- (These are dominated by open-flavor decays.)

- < 2.3 MeV

- 80(10) MeV

- 62(20) MeV

- 103(8) MeV

- 2007 PDG values

- X(3872)

- 26.3(1.9) MeV

## Experimental R summary (2003 PDG)

***Very interesting ***_***open***_*** theoretical question:***
- Do strong decays use the*** ***3P0 model decay mechanism
- or*** ***the Cornell model decay mechanism or ... ?

- ee, hence 1  c_c_ states only.

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

***“******Cornell” decay model:**** *
*(1980s c*_*c*_* papers)*
- (c_c_)  (c_n_)(n_c_)* coupling from q*_*q*_* pair production by linear confining interaction. *
- Absolute norm of  is fixed!

## An alternative strong decay model

_**An alternative strong decay model**_
**The ****3****P****0**** decay model**: q_q_ 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.

## Charmed meson decays

- PRD43, 1679 (1991).
- Decays of S- and P-wave
- D Ds B and Bs flavor mesons.
- 3P0 “flux tube” decay model.
- The
- L=1 0+ and 1+ c_s_ “Ds” mesons are predicted to have large total widths, 140 - 990 MeV. (= broad to unobservably broad).

_**Charmed meson decays**_

-      **How large are decay loop mass shifts and mixing effects?**
- 1. What c_s_ mesons are predicted to have exceptionally large strong decay amps?

## The 0+ and 1+ channels are predicted to have very large

- The 0+ and 1+ channels are predicted to have very large
- DK and D*K decay couplings.
- This supports the picture of strongly mixed
- |DsJ*+(2317,2460)>  =  |c_s_> + |(c_n_)(n_s_)>  states.
- Evaluation of loops: Initial results for c_c_ ...

## cc-hybrids, theory

## Characteristics of cc-hybrids.

- (folklore, mainly abstracted from models, some LGT)

_**Hybrid Multiplets**_** **
- (flux-tube model):
- The lightest hybrid multiplet should be a roughly degenerate set containing
**3 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 ee but with a suppressed width.
- (Hybrid models for different reasons predict  c_c_(r=0) = 0, suppressing ee .)
_**Unusual 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 c_c_-H  c_c_ + light mesons are large!
- (Shown for b_b_-H; (b_b_) is preferentially P-wave, and “light mesons” = scalar .)

## QQ-hybrid closed-flavor decays predicted by LGT:

**Q**_**Q**_**-hybrid**** closed-flavor decays predicted by LGT:**

- We are hoping that closed-flavor decays are a signature for
- charmonium hybrids (and not charmonia).
- If so, nature has been kind. This is a nice experimental signature.
- Searches for other decay modes of the Y(4260) are in progress...