Strong Decays and Couplings

GlueX + Exotic Hadron Spectroscopy 1. Hadrons 101 2. Exotica: glueballs, hybrids and multiquarks/molecules3. Hybrids: theoretical expectations and experimental status4. GlueX@JLAB; g prod of (hybrid) exotics

Ted BarnesPhysics Div. ORNLDept. of Physics and Astronomy, U.Tenn.GlueX PAC @ JLAB23 Aug 2010Hadrons 101

QCD flux tube (LGT, G.Bali et al.;hep-ph/010032)LGT simulation showing the QCD flux tube

QQR = 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 states (color singlets) (nave, valence)qq q3 Conventional quark modelmesons and baryons. q2q2, q4q,multiquarks

the multiquark fiasco-N.Isgurg2, g3, glueballsmaybe 1 e.g.

f0 (1500 or 1710)qqg, q3g,hybridsmaybe 1-3 e.g.sp1 (1600) best

Incl. exotic J PC!100s of e.g.sexotica :ca. 106 e.g.s of (q3)n, maybe 1-3 others X(3872) = DD*!(q3)n, (qq)(qq), (qq)(q3),nuclei / molecules_Basis state mixing may be very important in some sectors.(q2q2),(q4q), multiquark clustersdangerous: may not exist as resonancese.g. Q(1540) Parity Pqq = (-) (L+1) C-parity Cqq = (-) (L+S)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 qq are called JPC-exotic quantum numbers :

0 - - ; 0 + - ; 1 - + ; 2 + - ; 3 - + x Plausible JPC-exotic candidates = hybrids (have all JPC), glueballs (high mass), maybe multiquarks (fall-apart decays).The resulting qq N,L states N2S+1LJ have JPC = qq mesons quantum numbersQuarkonia:qq

as = 0.5538b = 0.1422 [GeV2]mc = 1.4834 [GeV]s = 1.0222 [GeV]Fitted and predicted cc spectrumCoulomb (OGE) + linear scalar conft. potential model blue = expt, red = theory.

S*S OGEL*S OGE L*S conft, T OGEQuarkonia:cc e.g.

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:

J PC exotics(non-qq)cccc hybrids (?)Exotic cc-H 1- + 4300(50), Nonexotic cc-H 1- - 4400(60).

J.J.Dudek, R.G.Edwards and C.E.Thomas,Exotic and excited-state radiative transitions in charmonium from lattice QCDPRD79, 094504 (2009), arXiv:0902.2241 [hep-ph].Paper quotes G(hc1 (1-+ exotic) -> J/y g ) ~ 100 keV.non-exotic 1-- hybridrad. trans.A typical robust cc radiative width. GlueX is justified. Radiative widths of exotics = ? (The BIG question for GlueX.)

Approx. status, light (u,d,s) qq spectrumto ca. 2.1 GeV.States are 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, G, JPC of qq candidates. Several recent candidates, e.g.a1(1700), a2(1750).I=1 shown, dashed boxes = expectedStatus of light meson spectroscopy (I=1 e.g.)Quarkonia:nn e.g.Theor. guides for expt qq searches: Extensive strong decay tables

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 Ds] 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:Exotica:

G/H/M

The glueball spectrum from an anisotropic lattice study

Colin Morningstar, Mike PeardonPhys. Rev. D60 (1999) 034509Theor. masses (LQCD)GlueballsNo JPC-exotics until 4 GeV !1 GeV2 GeV3 GeVG = new I=0 mesons starting with an extra scalar at ca. 1.6 GeV.

Then no new G states until > 2 GeV.

No JPC- exotic G until > 4 GeV. (= forget it)

G = 1 extra I=0 scalar meson at ca. 1.6 GeV.

f0(~1600)

= The worst possible quantum numbers experimentally! Several broad overlapping states.

Then no new G states until > 2 GeV.

No JPC- exotic G until > 4 GeV. (= forget it)GlueballsHow to make new (u,d,s,g) hadrons:Hit things together. A + B -> final state

You may see evidence for a new resonance in the decay products.Reactions between hadrons(traditional approach) are rich but usually poorlyunderstood.e.g.s

BNL p-p -> mesons + baryon

LEAR (CERN) pp annih.All light-q and g mesons,incl. qq, glueballs, hybrids, multiquarks.

Glueball discovery? Crystal Barrel expt. (LEAR@CERN, ca. 1995)pp -> p0 p0 p0

Evidence for a scalar resonance,f0(1500) -> p0 p0n.b. Some prefer a different scalar,f0(1710) -> hh, KK.PROBLEM: Neither f0 decays in a nave glueball flavor-symmetric way to pp, KK, hh.qq G mixing?Extra hadrons just below two-hadron thresholds. S-waves easiest look forquantum numbers of anS-wave pair.

Nuclei are examples MANY molecules exist!

Cant predict moleculesw/o understanding soft 2 -> 2 hadron scattering.

Add X(3872) to the list?

Molecules X(3872)

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 M( Do + D*o) = 3871.5 +- 0.5 MeV G < 2.3 MeVn.b. M( D+ + D*-) = 3879.5 +- 0.7 MeV M = 3872.0 +- 0.6 +- 0.5 MeV Charm in nuclear physics???A DD* molecule???Molecules The trouble with multiquarks:Multiquark models found that most channels showed short distance repulsion:

E(cluster) > M1 + M2.

Thus no bound states. (Remember (1540) ! )

Only 1+2 repulsive scattering (continuum) in this sector of Hilbert space.

nuclei and hypernuclei

weak int-R attraction allows moleculesIf E(cluster) < M1 + M2

bag model:u2d2s2 H-dibaryon, MH - MLL = - 80 MeV.

n.b. LLhypernuclei exist, so this H was wrong.Exceptions:VNN(R)-2mNRRVLL(R)-2mL2)1)Q2q2 (Q = b; c?)3)Heavy-lightn.b. multiquark .ne. moleculeFall-Apart Decay (actually not a decay at all: no HI)

(Light; u,d,s) Hybrids: Theory and Experiment

[flux-tube model]

New RICH band of meson excitationsexpected, starting at ca. 1.9 GeV.

Flavor nonets x 8 JPC = 72 states.

Includes 0+-, 1-+ and 2+- JPC-exotics.

[bag model]

ca. 1.5 GeV.

Lowest exotic is 1-+ (TE gluon) 0+- and 2+- are at higher mass (TM)

Hybrids

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 QCDarXiv: 1004.4930v1Most recent LQCD results for light exotics, JPC = 1- + , 2+ - , 0+ - .mq incr. ->u,d2.5 GeV2.0 GeV1.5 GeVp1(1600)1.0 GeVn.b.

All 3 of these exotic J PCs were degen. in the flux-tube model.

In the bag model, 1-+ is lighter.

N.Isgur, R.Kokoski and J.Paton, PRL54, 869 (1985).

Gluonic Excitations of Mesons: Why They Are Missing and Where to Find Themp1 -> b1p, f1pHL=1 -> S+P

S+P modes

(poorly studied exptally;

multimeson final states)1- + exotic is observably narrow! some hybrids are predicted to be VERY broadHybrid Meson Decays: flux-tube modelHybrids

w(2000) hybridp2(2000) hybrid;b1p modeClose and Page: some notably narrow nonexotic hybrids in the f-t modelF.E.Close and P.R.Page, NPB443, 233 (1995).Hybrid = qqg 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, p1, is especially attractive. It is predicted in the f.t. decay model to be relatively narrow and to have unusual decay modes.

Hybridsflux-tube model(Theory Summary)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 baryonsNon-exotics in a rich N* background spectrum(Light) Hybrids: Experiment

1(1600)E.I.Ivanov et al. (BNL E852)PRL86, 3977 (2001).1- + exotic reported in p-p -> p- h p ph is a nice channel because nn couplingsare weak for once (e.g. the a2(1320) noted here). The reported exotic P-wave is dominant!The (only) strong JPC-exotic H candidate signal.p-p -> p-h p

A.Alekseev et al. (COMPASS Collab.) Observation of a J P C =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.p1(1600)

JPC exotic

(confirmed)n.b.

resonant phase motion (confirmed but not shown here)is of course the crucial testSummary regarding meson spectroscopy and exotics: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 cs low masses hence tiny widths; also perhaps new molecular states and hybrids.

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 terms of QCD.

n.b. Exciting discoveries in meson spectroscopy are often serendipitous:

J/Y Ds0*(2317) Ds1(2460) X(3872) Y(4260)

Hybrids: JLAB and elsewhere(final comments) Existing and planned facilities (the competition?):BES-III (Beijing) [now] e+e- to sqrt(s) ca. 4.2 GeV. Mainly very large J/y and y event samples.Charmonium decays, in future unusual cc sector states? Y(4260)? Application to light and exotic spectroscopy? Could do e.g. rad decays.COMPASS (CERN) [now] High energy p- beam available, former E852 people (S.U.Chung) revisiting p p but at higher E (more diffractive). Have seen evidence for the p1(1600), willproceed to other interesting final states.PANDA (GSI) [2017+] Dedicated spectroscopy experiment. Official goal is cc hybrids.pp annihilation to sqrt(s) ca. 5 GeV (higher energy LEAR). Light spectroscopy for free. n.b. Lower energy pp produced the f0(1500) glueball candidate, and has a large p1(1400) signal.

**Not really. Discovery of unusual hadrons requires confirmation by other experiments. GlueX at JLAB: Photoproduction (~new expt approach) accesses exotic-JPC easily (S=1 beam)plucking the string - Isgur. [or is it vec dom?]

Several production 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.)

n.b. 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?).Recent e.g. of 3pi CEX photoproduction (CLAS), showing a2(1320) and 2(1670) qq states.

a2 2The importance of GlueX at JLAB: (Summary. C.Meyer presentation follows)The light (u,d,s,g) meson spectrum is poorly known above ca. 1.5 GeV.

Theorists expect a rich new spectroscopy of hybrids, including exotics, starting not far above this mass. Widths and decay mechanisms are obscure [models], will be explored by LQCD in the near future.

GlueXs goal is to establish the meson spectrum to ca. 2.5 GeV, and see whats out there. [serendipity in spectroscopy]

Past lessons (4pi detector, hermiticity, neutral and final modes, studies of all decay modes, robust PWA) have been learned (LEAR, E852) and arebeing implemented.

It will be very exciting!

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