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					                                                                                                      Ted Barnes
                                                                                                     BNL Seminar
                                                                                                     18 Mar. 2008




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 cc 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.
1. Basic hadronics.
   Color singlets and QCD exotica
     “confinement happens”.

LGT simulation showing the QCD flux tube
                Q        Q
                R = 1.2 [fm]



                                           “funnel-shaped” VQQ(R)
                                            Coul. linear conft.
                                            (OGE) (str. tens. = 16 T)




   QCD flux tube (LGT, G.Bali et al.;
   hep-ph/010032)
Physically allowed hadron states (color singlets) (naïve, valence)

        _                           3                Conventional quark model
      qq                           q                 mesons and baryons.

                   100s of e.g.s

                                                        3 n                            3
                                                     (q ) , (qq)(qq), (qq)(q ),…
        Basis state mixing may be
        very important in some sectors.              nuclei / molecules

     “exotica” :                                           6          3 n
                                                     ca. 10 e.g.s of (q ) , maybe 1-3 others
                                                                             X(3872) = DD*!

        2    3                                3                    22 22    4 4
      g , g ,…                     qqg, q g,…                    (q q q,…
                                                                 q qq, ),(q q),…

      glueballs                     hybrids                      multiquark
                                                                 multiquarksclusters

                                                                 dangerous
      maybe 1 e.g.                 maybe 1-3 e.g.s
                                                                 e.g. Q(1540)
 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
 qq mesons                                quantum numbers
                             (L+1)                              (L+S)
     Parity Pqq = (-1)                    C-parity Cqq = (-1)

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

    1S: 3S1 1 - - ;        S0 0 - +   2S: 23S1 1 - - ; 21S0 0 - + …
                       1




    1P: 3P2 2 + + ; 3P1 1 + + ; 3P0 0 + + ; 1P1 1 + -   2P …

    1D: 3D3 3 - - ; 3D2 2 - - ; 3D1 1 - - ; 1D2 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).
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. pp
              Fermilab (past),
              GSI/Darmstadt (start 2013 AD)
              messy theoretically, large backgrounds,
              less restricted quantum numbers



                              …some Feynman diagrams:
 + -
e e collisions (1):


           -
       e



                        g         y
                                                        hadrons




           +
       e


The traditional approach: s-channel annihilation.
Restricted to JPC = 1 - - . s = O(a2).

(May then use hadronic or radiative transitions to reach other states.)
 + -
e e collisions (2):




“Two-photon collisions”.

Forms positive C-parity charmonia. (esp. JPC = 0 - +, 0 + + , 2 + + ).

Quite small cross sections, s = O(a4), so
requires high intensity e+e- beams.
 + -
e e collisions (3):                    “B factories”




                                                bb




Surprisingly effective for making charmonia.
The source of several recent discoveries in this field.
pp collisions :




Used at Fermilab (E760 and E835).
Planned for GSI/Darmstadt (PANDA facility).
3. The spectrum of charmonium.




               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 states
                                                                -+ --
                                                   except 1D2 2 , 2


                                                                       3.73 GeV


                                                   Below 3.73 GeV:
                                                   Annihilation and EM decays.
                                                                        +-
                                                   (rp, KK* , gcc, gg, l l ..):
                                                   narrow states.
Minimal quark potential model physics:

OGE + linear scalar confinement;

Schrödinger eqn (often relativized) for wfns.
                      2   2
Spin-dep. forces, O(v /c ), 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.)
     Fitted and predicted cc spectrum
Coulomb (OGE) + linear scalar conft. potential model
              blue = expt, red = theory.




                             L*S OGE – L*S conft,
                              T OGE




                                       as = 0.5538
                                                       2
                                       b = 0.1422 [GeV ]
             S*S OGE
                                       mc = 1.4834 [GeV]
                                       s = 1.0222 [GeV]
     Fitted and predicted cc spectrum
Coulomb (OGE) + linear scalar conft. potential model
              blue = expt, red = theory.




                                             Two narrow states are expected,
                                                    PC    -+       --
                                             with J = 2 and 2 .
                                             The 1D multiplet is theoretically
                                             close to degenerate, near the
                                             3
                                               D1 y(3770).




                             L*S OGE – L*S conft,
                              T OGE




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




                                            -+
                                     <- 1        exotic cc-H at 4.4 GeV




                Small
    +-
                L=2 hfs.
    1 cc has
    returned.
                    Best recent LQCD ref for ccbar and cc-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 cc still rather difficult
to distinguish from quark model.                  -+
                                             (J        spectrum)
                    -+
Ambiguity in the 1 exotic noted.
(However other exotics again appear
around 4.5 GeV.)



                                 M [MeV]
     End of

Introduction to cc
  4. The new “XYZ” states:
     2P cc? 3S cc? Molecules? cc hybrids?
Nonresonant enhancements? Experimental errors?
         How to test these possibilities?


                Recommended reading:

        “The New Heavy Mesons: A Status Report”
      E.S.Swanson, Phys. Reports 429, 243-305 (2006).

           “What’s new with the XYZ mesons?”
     S.L.Olsen, arXiv:0801.1153v3 [hep-ex]13 Feb 2008.

        “The Exotic XYZ Charmonium-like Mesons.”
 S.Godfrey and S.L.Olsen, arXiv:0801.3867 [hep-ph] Jan 2008.
           submitted to Ann. Rev. Nucl. Part. Phys.
“Selections from…”

(Godfrey and Olsen review, list of new states):
                                           BGS, hep-ph/0505002, PRD72, 054026 (2005).
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 G < 1 MeV!
 … but first, the first of the new discoveries:

new, unexpected, very long-lived mesons in the cs sector!


        *
      D s0 (2317) and Ds1(2457)

        cs mesons or DK molecules?

                     (or both)
 + -
e e collisions (3):                    “B factories”




Surprisingly effective for making charmonia.
The source of several recent discoveries in this field.
                                                                        +           + 0
Where it all started.                              BABAR:   D*
                                                             s0(2317)       in Ds    p

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


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



          “Who ordered that !?”
                      - I.I.Rabi,   about the m-




 Since confirmed by
 CLEO, Belle and FOCUS.


(Theorists expected L=1 cs states, e.g.
 P  +
J =0 , but with a LARGE width and at a
much higher mass.) …
                                                      +      + 0
And another!                          CLEO:   Ds1(2460) in Ds*   p


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


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




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


   P   +                  +
A J =1 partner of the 0
          +
D*s0(2317) cs ?
(Godfrey and Isgur potential model.)   Prev. (narrow) expt. states in gray.




                                                                       DK threshold




                                       What caused large downwards
                                       mass shifts? Mixing with 2 meson
                                       continuum states? (Believed true.)
   L’oops

                                                         [ J/y - M1M2 - J/y ]
    M 1 M2     DM [J/y]     PM  M [J/y]
                                                        3
                                                         P0 decay model,
                               1 2
                                                        std. params. and SHO wfns.
     DD       - 23. MeV      0.021
     DD*      - 83. MeV      0.066        famous 1 : 4 : 7 ratio DD : DD* : D*D*
     D*D*     - 132. MeV     0.094
     DsDs     - 21. MeV      0.015
     DsDs*    - 76. MeV      0.048
     Ds*Ds*   - 123. MeV     0.072

     Sum =    - 457. MeV     Pcc = 69.%       VERY LARGE mass shift
                                              and large non-cc component!

Can the QM really accommodate such large mass shifts??? Other “cc” states?
L’oops

                     [ cc - M1M2 - cc ]
                       3
                       P0 decay model,
                   std. params. and SHO wfns.




         Loops produce a roughly
         state-independent overall
         negative mass shift !
 L’oops

                                                              [ cc - M1M2 - cc ]
                                                                3
                                                                P0 decay model,
                                                            std. params. and SHO wfns.




Loop mass shifts of states within L,S cc 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
Coulomb (OGE) + linear scalar conft. potential model
              blue = expt, red = theory.




                                             Two narrow states are expected,
                                                    PC    -+       --
                                             with J = 2 and 2 .
                                             The 1D multiplet is theoretically
                                             close to degenerate, near the
                                             3
                                               D1 y(3770).




                             L*S OGE – L*S conft,
                              T OGE




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


    X(3872) from KEK                     B
                                             +/-
                                                   -> K
                                                          +/-   + -
                                                                p p J/Y




                                                                      3
                                   Alas the known y(3770) = D1 cc.

                                   If the X(3872) is 1D cc,
                                   an L-excited multiplet is split much
                                   more than expected assuming
                                   scalar confinement.



                           G < 2.3 MeV

              M = 3872.0 +- 0.6 +- 0.5 MeV            Accidental agreement?
                                                               -+    --
                                                      X = cc (2 or 2 or …),
   M( Do + D*o) = 3871.5 +- 0.5 MeV                   or a DD* molecule?
n.b. M( D+ + D*-) = 3879.5 +- 0.7 MeV
X(3872) confirmation       CDF II Collab.
                           D.Acosta et al, hep-ex/0312021,

(from Fermilab)
                           PRL.




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




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




                       OK, it’s real…
                       n.b. molecule.ne.multiquark
 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) > M1 + M2.

                                              Thus no bound states.

                                              Only 1+2 repulsive scattering.


Exceptions:
                                                    2)   E(cluster) < M1 + M2,

         1)   nuclei and hypernuclei                     bag model:
                                                          2 2 2
                                                         u d s H-dibaryon, MH - MLL = - 80 MeV.
              weak int-R attraction allows
VNN(R)        “molecules”                    “VLL(R)”    n.b.   LLhypernuclei   exist, so this H was wrong.
-2mN                                         -2mL
                                                                                            3)   Heavy-light
                    R                                                R                       2 2
                                                                                            Q q (Q = b, c?)
                                        Belle Collab. K.Abe et al, hep-ex/0308029;
                                        S.-K.Choi et al, hep-ex/0309032, PRL91 (2003) 262001.

                                             +/-          +/-    + -
                                         B         -> K         p p J/Y
           X(3872)
                                                    3
                                   y(3770) =            D1 cc.

                                   If the X(3872) is 1D cc,
                                   an L-multiplet is split much more
                                   than expected assuming
                                   scalar conft.



                           G < 2.3 MeV

                                                         Accidental agreement?
              M = 3872.0 +- 0.6 +- 0.5 MeV                       -+    --
                                                         X = cc 2 or 2 or …,
   M( Do + D*o) = 3871.5 +- 0.5 MeV                      or a molecular (DD*) state?
n.b. M( D+ + D*-) = 3879.5 +- 0.7 MeV
                                                         Charm in nuclear physics???
DD* molecule options
This possibility is suggested by the similarity in mass,

M(X) =               3872.0 +- 0.6 +- 0.5 MeV
       o      o
M( D + D* ) = 3871.5 +- 0.5 MeV

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:
 Y(4040) as a D*D* molecule;
 (Voloshin and Okun; deRujula, Georgi and Glashow).


n.b.2 Could the signal simply be a cusp due to new DD* channels opening?
Interesting prediction of molecule decay modes:
                ++   o   o
E.S.Swanson: 1 D D* molecule - maximally isospin violating!
with additional comps. due to rescattering.

                                                  J/yro          J/y“w”




Predicted total width ca. = expt limit (2 MeV).

Very characteristic mix of isospins: comparable J/yro and J/y“w” decay
modes expected. Appears to be confirmed experimentally!

Nothing about the X(3872) is input: this all follows from OpE and C.I.
       Z(3930)
  3
a 2 P2 charmonium state?
 + -
e e collisions (2):




“Two-photon collisions”.

Forms positive C-parity charmonia. (esp. JPC = 0 - +, 0 + + , 2 + + ).

Quite small cross sections, s = O(a4), so
requires high intensity e+e- beams.
Z(3931)                                         gg -> Z(3931) -> DD




   [ref] = Belle, hep-ex/0507033, 8 Jul 2005.
Z(3931)

                            3
            Z(3931) = 2 P2 cc ?        (suggested by Belle)

            Expt for Z(3931): gg -> Z(3931) -> DD
            G = 20 +/- 8 +/- 3 MeV
            Ggg * BDD = 0.23 +/- 0.06 +/- 0.04 keV

                        3
            Theory for 2 P2(3931):                      The crucial test of
            G = 47 MeV DD*/DD = 0.35                               3
                                                        Z(3931) = 2 P2 cc :
            Ggg * BDD = 0.47 keV                          DD* mode $ ?
                                   th
            (Ggg from T.Barnes, IX Intl. Conf.
            on gg Collisions, La Jolla, 1992.)        Gtot
                                                              thy
                                                       expt




Ggg in http://web.utk.edu/~tbarnes/website/Barnes_twophot.pdf
           X(3940)

and double charmonium production
   + -
  e e collisions (5): Double charmonium production.


                                                                   J/y




                                                                   C=(+) cc


The traditional approach, s-channel annihilation, but can now make C=(+) charmonia!

                                                                   JPC = JP+
                                                                   An interesting new charmonium
X(3943)                                                            production mechanism!


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




                                                      hc’             X(3943)
                                           hc
                                                 c0
                                                                      No c1 or c2 !?




                                                                                    1
  [ref] = Belle, hep-ex/0507019, 8 Jul 2005.    n.b. Eichten: X(3943) may be the 3 S0 cc hc’’.
cc spectrum, potential models (dashed: nonrel L, Godfrey-Isgur R) vs data

                                                 Possible new C=(+) cc states
                                                       + -
                                                 from e e !



                                     2P or not 2P?
     Y(4260)

a charmonium hybrid?
                                                                 E.I.Ivanov et al. (E852)
p1(1600)                     PC
           The (only) strong J -exotic H candidate signal.       PRL86, 3977 (2001).



                                                             p-p -> p-h’ p


                                      p1(1600)
                                       -+
                                      1     exotic reported in p-h’




                                    ph’is a nice channel because nn couplings
                                    are weak for once (e.g. the a2(1320) noted here).
                                    The reported exotic P-wave is dominant!
    + -
  e e collisions (6): Initial state radiation (ISR)


                                                                  J/y




The traditional approach, s-channel annihilation, but can use higher energy beams.

Still restricted to JPC = 1 - - .
Y(4260)                                   + -                     + -
                                         e e -> Y(4260)ISR, Y -> p p J/y
                                                                closed-flavor
  [ref] = BaBar, PRL95, 142001 (2005).                          decay mode !?




                                                                     Not seen
                                                                     in R.
                                                                     Hmmm?!




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




                                -+
                         <- 1        exotic cc-H at 4.4 GeV

                                 n.b. The flux-tube model of hybrids
                                                                   PC
                                 has a lightest multiplet with 8 J s;
                                 3 exotics and 5 nonexotics, roughly
          Small                                       +- /-+   ++,  --
                                 degenerate: (0,1,2)        , 1 ,1 .
          L=2 hfs.
                                                              Y(4260)?
How to test a cc-hybrid assignment, esp. for Y(4260) :



   1. Confirm existence
                                            PC
   2. Establish the multiplet, including J       exotics!

   3. Unusual decays (if not exotic)
Y(4260)
          --
Prev. 1        state in
  +   -        +   -
e e -> p p J/y

BaBar; Belle, CLEO




Y(4360), Y(4660)
          --
New 1          states in
  +   -        +   -
e e -> p p y’

Belle shown



                           X.L.Wang et al, PRL99, 142002 (2007).
The latest craziness…




                         +/-
                        Z (4430)

               charged charmonium???
                                       BELLE Collab. 0708.1790v1 (14 Aug. 2007)




                                                         Z(4430)




+/- charge requires ccud quark content.
Not cc!

n.b. At D*(2010) D1(2420) threshold.
                    Conclusions
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 gg
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!
END / EXTRAS
3.b. Strong decays
Strong decays of charmonia
         This is a wide open field for the smart young theorist.


There are two main types of cc strong decays. Neither is well understood.

I. cc annihilation.

(cc) -> gluons (?) -> light hadrons


II. Open flavor decays. (Dominant if allowed.)

(cc) -> (cq) + (qc)

Theorists have simple ideas about these strong decays and
rough models for them but not much more. Some simple ideas
like pQCD fail dramatically.
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:




    Gtot(MeV):
                 hc 25.5 (3.4)                J/y 0.0934 (0.0021)
                 c0 10.4 (0.7)                y’ 0.337 (0.013)
                 c2 2.06 (0.12)
                 hc’ 14.  (7.)
Strong decays (open flavor)
Total widths of cc resonances…




                              4040          4415
                       3770
                                     4160
What are the total widths of cc states above 3.73 GeV?
       (These are dominated by open-flavor decays.)


                62(20) MeV                      2007 PDG values


                                                103(8) MeV
                80(10) MeV

                                      X(3872)   < 2.3 MeV
                                                26.3(1.9) MeV
How do open-flavor strong decays happen at the QCD (q-g) level?

Experimental R summary (2003 PDG)
Very interesting open theoretical question:
                        3
Do strong decays use the P0 model decay mechanism
or the Cornell model decay mechanism or … ?

               + -            --
              e e , hence 1        cc states only.




                                                     “Cornell” decay model:

                                                     (1980s cc papers)
                                                     (cc) <-> (cn)(nc) coupling from qq pair
                                                     production by linear confining interaction.
                                                     Absolute norm of G is fixed!




                                                         g0          g0
                                                               br

                                                     vector confinement???            controversial
                    An alternative strong decay model
    3
The P0 decay model: qq pair production with vacuum quantum numbers.
                               LI= g y y .
    A standard for light hadron decays. It works for D/S in b1 -> wp.
                     The relation to QCD is obscure.
            How large are decay loop mass shifts and mixing effects?
    1. What cs mesons are predicted to have exceptionally large strong decay amps?

Charmed meson decays
S.Godfrey and R.Kokoski,
PRD43, 1679 (1991).

Decays of S- and P-wave
D Ds B and Bs flavor mesons.
3
P0 “flux tube” decay model.

The
       +      +
L=1 0 and 1 cs “Ds” mesons
are predicted to have large
total widths, 140 - 990 MeV.
(= broad to unobservably
broad).
P    +
J = 1 (2460 channel)
                               +    +
                       The 0 and 1 channels are predicted to have very large
 P   +
J = 0 (2317 channel)   DK and D*K decay couplings.
                       This supports the picture of strongly mixed
                          *+
                       |DsJ (2317,2460)> = |cs> + |(cn)(ns)> states.

                       Evaluation of loops: Initial results for cc …
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
                                  PC
      3 exotic and 5 nonexotic J ;
       +-   -+   +-   -+   +-   -+   ++    --
      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 ycc (r=0) = 0, suppressing Gee .)

      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. p1(1600) -> p h’ 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 pp.)
QQ-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…

				
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posted:10/17/2012
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