From Heavy Q to Light q Systems

1. What hadrons exist in nature? Quarkonia / Baryons / Hybrids / Glueballs / Multiquarks

2. Recent developments in cc (noises off)

3. Where we will boldly go if time permits: Status of light qq H G (M)

Next: J.Dudek (light mesons), A.Dzierba (on GlueX@Jlab)

Ted BarnesPhysics Div. ORNL

Dept. of Physics and Astronomy, U.Tenn.

DOE NP Town MeetingRutgers U.12-14 Jan 2007

(Meson Spectroscopy Theory Overview)

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

Quarkonia

Parity Pqq

= (-1) (L+1)

C-parity Cqq

= (-1) (L+S)

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 =

qq mesons quantum numbers

Developments in the cc sector

(noises off)

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

Expt. states 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*S OGE

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

model black = expt, red = theory.

states fitted

DD

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. Need LGT cc radiative and strong decay predictions!

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), (4350)?

S*S OGE

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

model black = expt, red = theory.

Y(4260) JPC = 1- -

(4350) JPC = 1- -

Z(3930) JPC = 2++ ; X(3940), Y(3940) C = (+)DD*

DD

X(3872) JPC = 1++

X(3872)

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

J

DD*MeV

MeV

n.b.DD*MeV

MeV

Charm in nuclear physics???

n.b. molecule.ne.multiquark

A DD* molecule?!

Molecules and Multiquarks

Isospin “violation” in molecule decays: a signature

E.Swanson, hep-ph/0311229, PLB588, 189 (2004): 1 DoD*o + … molecule (additional comps. due to off-diagonal FSI rescattering).

J“”J

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

Very characteristic mix of isospins: comparable J andJ“”decay modes expected. Now appears confirmed. (maybe)

Nothing about the X(3872) is input: this all follows from OE and C.I.

The trouble with multiquarks: “Fall-Apart Decay” (actually not a decay at all: no H

I)

Multiquark models found thatmost channels showed short distance repulsion:

E(cluster) > M1 + M

2.

Thus no bound states.

Only 1+2 repulsive scattering.

nuclei and hypernuclei

weak int-R attraction allows “molecules”

E(cluster) < M1 + M

2,

bag model:

u2d2s2 H-dibaryon, MH - M

= 80 MeV.

n.b.

hypernuclei exist, so this H was wrong.

Exceptions:

VNN

(R)

2mN

R R

“V

(R)”

2m

Q2q2 (Q = b, c?)

2)

1)

3) Heavy-light

Where it all started: The BABAR state D*sJ

(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 cs states, e.g. JP=0+, but with a LARGE width and at a much higher mass.) …

And another! The CLEO state D*sJ

(2463)+ 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)

JP=1+partner of the D*s0

(2317)+cs?

(Godfrey and Isgur potential model.) Prev. (narrow) expt. states in gray.

DK threshold

Light ( = u,d,s,g) mesons

What we theorists expect and will be proven wrong about.

Approx. status, light (u,d,s) qq spectrumto ca. 2.1 GeV.

Well known to ca. 1.5 GeV, poorly known above(except for larger-J).

n.b. ss is poorly known generally.

Strong decays give M, , JPC of qq candidates.

Light qq (I=1 u,d shown)

Several recent candidates, e.g.a

1(1700), a

2(1750).

I=1 shown, dashed = expected

GlueX regime(ALL mesons in this range)

New band of meson excitationspredicted, starting at ca. 1.9 GeV.

Flavor nonets x 8 JPC = 72 states.

Includes 0, 1 and 2 JPC-exotics.

(Light) Hybrids:

Open-charm strong decays: 3P0 decay model (Orsay group, 1970s)

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.

Strong Decays

Extensive strong decay tables (ca. 1985-present)

S.Godfrey and N.Isgur, PRD32, 189 (1985).T.Barnes, F.E.Close, P.R.Page and E.S.Swanson, PRD55, 4157 (1997). [u,d mesons]T.Barnes, N.Black and P.R.Page, PRD68, 054014 (2003). [strange mesons] [43 states, all 525 modes, all 891 amps.]T.Barnes, S.Godfrey and E.S.Swanson, PRD72, 054026 (2005). [charmonia: 1st 40 cc mesons, all open-charm strong decay amps, all E1 and many M1 transitions]F.E.Close and E.S.Swanson, PRD72, 094004 (2005). [open-charm mesons: D and D

s]

qq meson decays:

qqq baryon decays:

S.Capstick and N.Isgur, PRD34, 2809 (1986).S.Capstick and W.Roberts, PRD49, 4570 (1994); PPNP 45, S241-S331 (2000). [BPs, BV modes of u,d baryons]

Mainly light (u,d,s) hadrons in f.-t. or 3P0

models.

A few references:

Example of the detailed theor. predictions for light qq meson strong decays:

Some results for strange meson decays (BBP paper):

3F2 ss -> K

1(1273) K

confirms

Blundell and Godfrey.

3F3 ss -> K

2*K

dominant

3F4 ss (max J)

typically ARE dominated by the lowest few allowed modes.(Cent. barrier.)

The five narrowest unknown (?) ssbar states below 2.2 GeV:

state tot

Favored modes [expt?]

D

2(1850)129 MeV KK* [WA102

2(1617)-

2(1842): nn <-> ss

mixing?]

2) Ff

(2200) 156 MeV K*K*, KK, KK* [LASS 2209; Serp. E173

2257]

3) 31S0

s(1950) 175 MeV K*K*, KK*

4) 21P1 h

1(1850) 193 MeV KK*, K*K*, [ss filter]

5) 13D2

2(1850) 214 MeV KK*,

(Light) Hybrids

Hybrid = qq“g” states (with q=u,d,s) span flavor nonets, hence there are many experimental possibilities.

Models agree that the lightest hybrid multiplet contains JPC-exotics.

f.t. model predicts 8 JPC x 9 flavors = 72 “extra” resonances at the hybrid threshold.

3/8 JPC are exotic, 0, 1, 2.

The remainder, 0, 1, 2, 0, 1, 1 are “overpopulation” rel to the quark model.

Mestm

ca. 1.5 - 2.0 GeV. f.t. 1.9 GeV is famous. LGT mass similar to f.t. for 1 .

JPC = 1 with I=1, “”, is especially attractive. It is predicted in the f.t. model

to be relatively narrow and to have unusual decay modes.

Hybrid Meson Decays: flux-tube modelN.Isgur, R.Kokoski and J.Paton, PRL54, 869 (1985).Gluonic Excitations of Mesons: Why They Are Missing and Where to Find Them.

b

f

S+P

Expt Hybrid mesons? The current best signal for a JPC = 1 exotic. (Can’t be qq.) E852@BNL, ca. 1996

p (’) p

aqq

(Current best of several reactions with claims of

exotics.)

exoticn.b. NOT an“S+P” flux tubefavored mode!

hybrid

hybrid;b mode

Close and Page: some notably narrow nonexotic hybrids in the f-t model

F.E.Close and P.R.Page, NPB443, 233 (1995).

Spectrum of light (n=u,d) hybrid baryons.S.Capstick and P.R.Page, nucl-th/0207027, Phys. Rev. C66 (2002) 065204. (flux tube model)

M (MeV)

Hybrid baryons

lightest hybrid baryons,flux tube model

overpopulationof the qqq quark model,starting with1/2+, 3/2+

ca. 1870 MeV

The glueball spectrum from an anisotropic lattice study

Colin Morningstar, Mike PeardonPhys. Rev. D60 (1999) 034509

Theor. masses (LGT)

Glueballs

New I=0 mesons starting with

1 scalar at ca. 1.6 GeV.

Then no states until > 2 GeV.

No JPC-exotics until 4 GeV.

Scalar glueball discovery? Crystal Barrel expt. (LEAR@CERN, ca. 1995)

pp 0 0 0

Evidence for a scalar resonance,

f 0 0

n.b. Some prefer a different scalar,

f

PROBLEM: Neither f0 decays in a naïve glueball flavor-symmetric way to KK.qq G mixing?

(Light) Molecules:

“Extra” hadrons just below two-hadron thresholds. S-waves easiest – look forquantum numbers of anS-wave pair.

Nuclei are examples… MANY molecules exist!

Can’t predict moleculesw/o understanding soft hadron scattering.

Add X(3872) to the list of molecules!

Future: “Unquenching the quark model”

Virtual meson decay loop effects,qq M1 M2 mixing.

e.g. DsJ

* states (mixed cs DK …, how large is the mixing?)

Are the states close to |cs> or |DK>, or are both basis states important?

A perennial question: accuracy of the valence approximation in QCD.

Also LGT-relevant (they are often quenched too).

L’oops

Summary regarding meson spectroscopy:

Theorists expect new types of mesons (glueballs and hybrids) starting at ca. 1.5 - 2 GeV.

A few candidates exist. Looking for JPC-exotics is a good strategy.

Also overpopulation - need to better establish the qq sector above 1.5 GeV and ss!

Charm mesons (cs and cc sectors) have surprised people recently – low masses hence tiny widths; also perhaps new molecular states.

Data on the spectrum is needed to compare with models and LGT.Strong and EM widths are also useful information. Strong decays are poorly understood in QCD.

Exciting discoveries in meson spectroscopy are often serendipitous:

J/ Ds0

*(2317) Ds1

(2463) X(3872)

Summary regarding GlueX at JLAB: (A.Dzierba presentation)

Photoproduction accesses exotic JPC easily (S=1 beam).

Several mechanisms, 2 are:

t-channel CEX, e.g.

diffr., e.g.

(Also s- and u-channel baryon resonances.)

Detect ALL strong modes, hermetic, PWA.• You get the poorly explored ss sector for free.

Theorists can contribute by 1. LGT spectroscopy and decays,2. modeling photoproduction of both exotic and ordinary qq resonances (CLAS data?).

End