Transcript ppt

DOE NP Town Meeting
Rutgers U.
12-14 Jan 2007
Ted Barnes
Physics Div. ORNL
Dept. of Physics and
Astronomy, U.Tenn.
From Heavy Q to Light q Systems
(Meson Spectroscopy Theory Overview)
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)
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
qq
Conventional quark model
mesons and baryons.
q
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” :
2
3
g , g ,…
glueballs
maybe 1 e.g.
6
3 n
ca. 10 e.g.s of (q ) , maybe 1-3 others
X(3872) = DD*!
3
qqg, q g,…
hybrids
maybe 1-3 e.g.s
22 22
4 4
q
q q,…
(qqq, ),(q
q),…
multiquark clusters
multiquarks
dangerous
e.g. Q(1540)
Quarkonia
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
Parity Pqq = (-1)
quantum numbers
(L+1)
C-parity Cqq = (-1)
(L+S)
The resulting qq NL states N2S+1LJ have JPC =
1S: 3S1 1- - ;
1
S0 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 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).
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 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
black = expt, red = theory.
DD
states fitted
S*S OGE
cc and cc–H from LGT
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!
<- 1- + exotic cc-H at 4.4 GeV
Small
L=2 hfs.
n.b. The flux-tube model of hybrids
PC
has a lightest multiplet with 8 J s;
3 exotics and 5 nonexotics, roughly
+- /-+
++,
-degenerate: (0,1,2)
,1 ,1 .
Y(4260), Y(4350)?
Fitted and predicted cc spectrum
Coulomb (OGE) + linear scalar conft. potential model
black = expt, red = theory.
Y(4350) JPC = 1- Y(4260) J
Z(3930) J
PC
X(3872) J
PC
++
=2
++
=1
PC
--
=1
; X(3940), Y(3940) C = (+)
DD*
DD
S*S OGE
Molecules and Multiquarks
Belle Collab. K.Abe et al, hep-ex/0308029;
S.-K.Choi et al, hep-ex/0309032, PRL91 (2003) 262001.
X(3872)
B
+/-
-> K
+/-
+ -
p p J/Y
n.b. molecule.ne.multiquark
G < 2.3 MeV
M = 3872.0 +- 0.6 +- 0.5 MeV
M( Do + D*o) = 3871.5 +- 0.5 MeV
n.b. M( D+ + D*-) = 3879.5 +- 0.7 MeV
A DD* molecule?!
Charm in nuclear physics???
Isospin “violation” in molecule decays: a signature
++
o
o
E.Swanson, hep-ph/0311229, PLB588, 189 (2004): 1 D D* + … molecule
(additional comps. due to off-diagonal FSI 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. Now appears confirmed. (maybe)
Nothing about the X(3872) is input: this all follows from OpE and C.I.
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)
1)
VNN(R)
-2mN
bag model:
2 2 2
u d s H-dibaryon, MH - MLL = - 80 MeV.
nuclei and hypernuclei
weak int-R attraction allows
“molecules”
E(cluster) < M1 + M2,
“VLL(R)”
n.b.
LLhypernuclei
exist, so this H was wrong.
-2mL
R
R
3)
Heavy-light
2 2
Q q (Q = b, c?)
Where it all started: The BABAR state
D.Aubert et al. (BABAR Collab.),
PRL90, 242001 (2003).
M = 2317 MeV (2 Ds channels),
G < 9 MeV (expt. resolution)
(Theorists expected L=1 cs states, e.g.
P
+
J =0 , but with a LARGE width and at a
much higher mass.) …
D*
sJ(2317)
+
in Ds
+ 0
p
+
+ 0
And another! The CLEO state D*sJ(2463) in Ds*
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
+
+
J =1 partner of the D*s0(2317) cs?
p
(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.
Light qq (I=1 u,d shown)
I=1 shown, dashed = expected
Approx. status, light (u,d,s) qq spectrum
to 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.
GlueX regime
(ALL mesons in this range)
Several recent candidates, e.g.
a1(1700), a2(1750).
Strong decays give
M, G, JPC of qq candidates.
(Light) Hybrids:
New band of meson excitations
predicted, starting at ca. 1.9 GeV.
Flavor nonets x 8 J
+-
-+
PC
= 72 states.
+- PC
Includes 0 , 1 and 2 J -exotics.
Strong Decays
3
Open-charm strong decays: P0 decay model (Orsay group, 1970s)
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.
Extensive strong decay tables
(ca. 1985-present)
3
Mainly light (u,d,s) hadrons in f.-t. or P0 models.
A few references:
qq meson decays:
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.]
st
T.Barnes, S.Godfrey and E.S.Swanson, PRD72, 054026 (2005). [charmonia: 1 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 Ds]
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]
Example of the detailed theor. predictions for light qq meson strong decays:
Some results for strange meson decays (BBP paper):
3
F4 ss (max J)
typically ARE
dominated by
the lowest
few narrowest
The five
allowed modes.
(Cent. barrier.)
state
unknown (?) ssbar states below 2.2 GeV:
Gtot
Favored modes
-+
2 D2 h2(1850) 129 MeV KK*
++
1 F4 f4(2200) 156 MeV K*K*, KK, KK*
1) 2
2) 4
1
[WA102 h2(1617)-h2(1842): nn
3
3
-+
3) 0
1
3 S0 hs(1950) 175 MeV
*
K2 K
F3 ss ->
K*K*,dominant
KK*
1
++
2 P1 h1(1850) 193 MeV KK*, K*K*, hf [ss filter]
--
1 D2 f2(1850) 214 MeV KK*, hf
4) 1
5) 2
3
[expt?]
3
F2 ss -> K1(1273) K
confirms
<-> ss mixing?]
Blundell and Godfrey.
[LASS 2209; Serp. E173 2257]
(Light) Hybrids
Hybrid = qq“g” states (with q=u,d,s) span flavor nonets,
hence there are many experimental possibilities.
PC
Models agree that the lightest hybrid multiplet contains J -exotics.
PC
f.t. model predicts 8 J x 9 flavors = 72 “extra” resonances at the hybrid threshold.
PC
3/8 J
+-
-+
+-
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 .
PC
-+
J = 1 with I=1, “p1”, 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 model
N.Isgur, R.Kokoski and J.Paton, PRL54, 869 (1985).
Gluonic Excitations of Mesons:
Why They Are Missing and Where to Find Them.
HL=1 -> S+P
p1 -> b1p, f1p
Expt Hybrid mesons? The current best signal for a JPC = 1-+ exotic.
(Can’t be qq.) E852@BNL, ca. 1996
p-p -> (p-h’) p
(Current best of several
reactions with claims of
exotics.)
p1(1600)
n.b. NOT an
“S+P” flux tube
favored mode!
exotic
a2(1320)
qq
p2(2000)
hybrid;
b1p mode
F.E.Close and P.R.Page,
NPB443, 233 (1995).
Close and Page: some notably narrow nonexotic hybrids in the f-t model
w(2000)
hybrid
Hybrid baryons
Spectrum of light (n=u,d) hybrid baryons.
S.Capstick and P.R.Page,
nucl-th/0207027, Phys. Rev. C66 (2002) 065204.
M (MeV)
lightest hybrid baryons,
flux tube model
overpopulation
of the qqq
quark model,
starting with
+
+
1/2 , 3/2
ca. 1870 MeV
(flux tube model)
Glueballs
Theor. masses (LGT)
The glueball spectrum from an
anisotropic lattice study
Colin Morningstar, Mike Peardon
Phys. Rev. D60 (1999) 034509
New I=0 mesons starting with
1 scalar at ca. 1.6 GeV.
Then no states until > 2 GeV.
PC
No J -exotics until 4 GeV.
Scalar glueball discovery? Crystal Barrel expt. (LEAR@CERN, ca. 1995)
pp -> p0 p0 p0
Evidence for a
scalar resonance,
f0(1500) -> p0 p0
n.b.
Some prefer a different scalar,
f0(1710) -> hh, KK.
PROBLEM: Neither f0 decays in a naïve glueball flavor-symmetric way to pp, hh, KK.
qq <-> G mixing?
(Light) Molecules:
“Extra” hadrons just below
two-hadron thresholds.
S-waves easiest – look for
quantum numbers of an
S-wave pair.
Nuclei are examples…
MANY molecules exist!
Can’t predict molecules
w/o understanding soft
2 -> 2 hadron scattering.
Add X(3872) to the list
of molecules!
L’oops
Future: “Unquenching the quark model”
Virtual meson decay loop effects,
qq <-> M1 M2 mixing.
e.g. D * states (mixed cs <-> DK …, how large is the mixing?)
sJ
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).
Summary regarding meson spectroscopy:
Theorists expect new types of mesons (glueballs and hybrids) starting at ca. 1.5 - 2 GeV.
PC
A few candidates exist. Looking for J -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/Y
Ds0*(2317)
Ds1(2463)
X(3872)
Summary regarding GlueX at JLAB: (A.Dzierba presentation)
PC
Photoproduction accesses exotic J easily (S=1 beam).
Several mechanisms, 2 are:
t-channel CEX, e.g. g (-> r0) + p+ - -> p1
diffr., e.g. g + P -> 2
+-
(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