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Ted Barnes Physics Div. ORNL ICHEP2010 Paris, 23 July 2010. (A Few) Recent Developments in Hadron Spectroscopy (setting the stage for subsequent spectroscopy talks) . Topics: I. Basic hadronics II. Some exciting areas of current research: a. Charm hadrons b. Exotics III. Future .

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Ted Barnes

Physics Div. ORNL

ICHEP2010

Paris, 23 July 2010

(A Few) Recent Developments in Hadron Spectroscopy(setting the stage for subsequent spectroscopy talks)

Topics:

I. Basic hadronics

II. Some exciting areas of current research:

a. Charm hadrons

b. Exotics

III. Future



LGT simulation showing the QCD flux tube

Color singlets and QCD exotica

“confinement happens”.

Q

Q

R = 1.2 [fm]

“funnel-shaped” VQQ(R)

linear conft.

(str. tens. = 16 T)

Coul.

(OGE)

QCD flux tube (LGT, G.Bali et al.;

hep-ph/010032)


Physically allowed hadron states color singlets na ve valence

(q2q2),(q4q),…

(q3)n, (qq)(qq),(qq)(q3),…

multiquark clusters

nuclei / molecules

dangerous

e.g. Q(1540)

ca. 106 e.g.s of (q3)n, maybe 1-3 others

X(3872) = DD*!

g2, g3,…

qqg, q3g,…

q2q2, q4q,…

glueballs

hybrids

multiquarks

maybe 1 e.g. :

f0 (1500)

maybe 1-3 e.g.s

1 is “solid” : p1(1600)

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

_

Conventional quark model

mesons and baryons.

qq

q3

100s of e.g.s

Basis state mixing may be

very important in some sectors.

“exotica” :


Q q mesons quantum numbers
qq mesons: quantum numbers

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

The resulting qq N,L states N2S+1LJ haveJPC=

qq (allowed):

N

L

1S: 3S11 -- ; 1S00 -+2S: 23S11 -- ; 21S00 -+3D …

1P: 3P22 + + ; 3P11 + + ; 3P00 + + ; 1P11 +-2P …

1D: 3D33 - - ; 3D22 - - ; 3D11 - - ; 1D22 -+2D …



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.


Contact S*S from OGE;

Implies S=0 and S=1 c.o.g.

degenerate for L > 0.

(Not true for vector confinement.)

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

Coulomb (OGE) + linear scalar conft. potential model

blue = expt, red = theory.

L*S OGE – L*S conft,

T OGE

as= 0.5538

b = 0.1422 [GeV2]

mc = 1.4834 [GeV]

s = 1.0222 [GeV]

S*S OGE


Fitted and predicted cc spectrum

Coulomb (OGE) + linear scalar conft. potential model

blue = expt, red = theory.

Two narrow states are expected,

with JPC = 2- + and 2- -.

The 1D multiplet is theoretically

close to degenerate, near the

3D1 y(3770).


Best recent LQCD refs for cc and cc-hybrid spectroscopy.

(Summary of JLAB LQCD group results.) For references see:

“Charmonium excited state spectrum in lattice QCD.”

J.J.Dudek, R.G.Edwards, N.Mathur and D.G.Richards,

Phys. Rev. D77, 034501 (2008)and PRD78, 094504 (2008)

n.b. PRD79, 094504 (again) (2009) includes rad. transitions!)

Results for cc still rather difficult

to distinguish from quark model.

Final LQCD predictions fm JLAB:

Exotic cc-H 1- + 4300(50),

Nonexotic cc-H 1- - 4400(60).

J PC exotics

(non-qq)


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).

Possible new cc states

at these masses and

elsewhere! “XYZ” states

Reminder:

Three as yet unknown 1D states.

Predicted to have G < 1 MeV!

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

2P or not 2P?


e+e- collisions: Initial state radiation (ISR)

J/y

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

Still restricted toJPC = 1 - -.


Y(4260)

a (nonexotic) charmonium hybrid?


Y(4260)

e+e- -> Y(4260)ISR, Y -> p+p-J/y

closed-flavor

decay mode !?

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

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.

A1- - charmonium hybrid??


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…


e+e- collisions: 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

production mechanism!

Allows access to C=(+) cc states

in e+e- w/o using gg.

X(3943)

X(3943)

hc’

hc

c0

No c1or c2 !?

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

n.b. Eichten: X(3943) may be the 31S0 cchc’’.


X(3872)

a charmed meson molecule?


BelleCollab. 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

Alas the known y(3770) = 3D1cc

fixes the mass scale of 1D cc states.

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

G < 2.3MeV

M = 3872.0 +- 0.6 +- 0.5 MeV

Accidental agreement?

X = cc (2- + or 2- - or …),

or a DD* molecule?

M( Do + D*o) = 3871.5 +- 0.5 MeV

n.b. M( D+ + D*-) = 3879.5 +- 0.7MeV

Charm in nuclear physics???


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,

bag model:

u2d2s2 H-dibaryon, MH - MLL = - 80 MeV.

n.b. LLhypernuclei exist, so this H was wrong.

1)

nuclei and hypernuclei

weak int-R attraction allows

“molecules”

“VLL(R)”

VNN(R)

-2mN

-2mL

3)

Heavy-light

R

R

Q2q2 (Q = b, c?)


Interesting prediction of molecule decay modes:

E.S.Swanson: 1+ +DoD*o 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/yroandJ/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.


Not to forget the first of the new discoveries:

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

D*s0 (2317) and Ds1(2457)

cs mesons or DK molecules?

(or both)


Where the trouble all started: BABAR D*s0(2317)+ in Ds+p0

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. JP=0+, but with a LARGE width and at a much higher mass.) …


And another! CLEO: Ds1(2460)+ in Ds*+p0

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.

A JP=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.)



Q q mesons vs exotics quantum numbers
qq mesons vs.exotics: quantum numbers

JPC-exotic quantum numbers :

Plausible JPC-exoticcandidates =

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

not

qq:

0 - - 0 + - 1 - + 2 + - 3 - +4 + -…

qq(allowed):

1S: 3S11 -- ; 1S00 -+ 2S: 23S11 -- ; 21S00 -+ …

1P: 3P22 + + ; 3P11 + + ; 3P00 + + ; 1P11 +-2P …

1D: 3D33 - - ; 3D22 - - ; 3D11 - - ; 1D22 -+2D …


E.I.Ivanov et al. (E852)

PRL86, 3977 (2001).

p1(1600)

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

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!


A.Alekseevet al. (COMPASS Collab.) Observation of a JPC =1-+ exotic resonance in diffractive dissociation of 190 GeV pi- into pi- pi- pi+

ArXiv:0910.5842v3 (Sept. 2009)

M = 1660 +-10 +0 -64 MeV , Gamma = 269 +-21+42 -64 MeV.

n.b.

resonant phase

motion (confirmed

but not shown here)

is of course the

crucial test

p1(1600)

JPC exotic

(confirmed)


Most recent LQCD results for light exotics, JPC = 1- +, 2+ -, 0+ -.

J.J.Dudek, R.G.Edwards, M.J.Peardon, D.G.Richards and C.E.Thomas,

([JLAB] Hadron Spectrum Collaboration)

Toward the excited meson spectrum of dynamical QCD

arXiv: 1004.4930v1

n.b.

All 3 of these exotic JPCs were degen. in the

flux-tube model.

In the bag model,

1-+is lighter.

2.5 GeV

2.0 GeV

p1(1600)

1.5 GeV

1.0 GeV

u,d

mqincr.->



Future…

Spectroscopy involves an active interplay between theory and experiment.

Consequently, future topics will depend on developments in both areas.

Experiment:

BES-III is currently gathering high statistics cc data (J/y and y‘) in e+e-.

COMPASS has reported new results on light exotic spectroscopy in HE

hadroproduction.

GlueX will use protoproduction to search for light hybrids (incl. exotic JPC)

at JLAB, start ca. 2015.

PANDA will search for cc-hybrids (incl. exotics) at GSI, start ca. 2017.

Theory:

LQCD is being extended to light quarks; we should have accurate JPC-exotic

mass estimates and predictions of EM couplings and (open flavor) strong decays

in the next few years.



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