Glueballs and Light-Meson Spectroscopy

Introduction and Motivation Experimental Methods in Meson Spectroscopy Glueballs and Light Mesons The GlueX Experiment at Jefferson Lab Summary and Outlook

V. Credé

Florida State University, Tallahassee, Florida

Int. Workshop on Hadron Structure and Spectroscopy Venice, Italy 03/15/2010

V. Credé Glueballs and Light-Meson Spectroscopy Introduction and Motivation Experimental Methods in Meson Spectroscopy Glueballs and Light Mesons The GlueX Experiment at Jefferson Lab Summary and Outlook Outline

1 Introduction and Motivation The Quark Model of Hadrons Meson Spectroscopy 2 Experimental Methods in Meson Spectroscopy Glue-Rich Environments Photoproduction 3 Glueballs and Light Mesons The Quest for the Scalar Glueball Exotic Hybrid Mesons 4 The GlueX Experiment at Jefferson Lab 5 Summary and Outlook

V. Credé Glueballs and Light-Meson Spectroscopy Introduction and Motivation Experimental Methods in Meson Spectroscopy The Quark Model of Hadrons Glueballs and Light Mesons Meson Spectroscopy The GlueX Experiment at Jefferson Lab Summary and Outlook Outline

Mesons (qq) q ⊗ q = 3 ⊗ 3 = 8 ⊕ 1

Baryons (qqq) q ⊗ q ⊗ q = 3 ⊗ 3 ⊗ 3 = 10 ⊕ 8 ⊕ 8 ⊕ 1 | {z } Ordinary matter ...

Mesons (qq) q ⊗ q = 3 ⊗ 3 = 8 ⊕ 1

Baryons (qqq) q ⊗ q ⊗ q = 3 ⊗ 3 ⊗ 3 = 10 ⊕ 8 ⊕ 8 ⊕ 1 | {z } However, QCD also predicts so-called exotic states ➜ simplest possibility: q ⊗ q ⊗ q = 15 ⊕ 6 ⊕ 3 ⊕ 3 “SU(3) Color” | {z } Does not work: color singlets needed! ➜ multiple of (qqq) and (qq ) necessary

Glueballs: g ⊗ g = 8 ⊗ 8 = 27 ⊕ 10 ⊕ 10 ⊕ 8 ⊕ 8 ⊕ 1 Hybrids: q ⊗ q ⊗ g = 27 ⊕ 10 ⊕ 10 ⊕ 8 ⊕ 8 ⊕ 8 ⊕ 1 ➜ (qq)l((q)3)m(g)n , l + m ≥ 1 for n = 1

J PC 2S+1 L = 0, S = 1 : J ≡ LJ ρ, ω, φ (JPC = 1−−) Parity P = (−1)L+1 Charge Conjugation L = 0, S = 0 : (deﬁned for neutral mesons) − e.g. π (JPC = 0 +) C = (−1)L+S G parity G = C(−1)I

J PC 2S+1 L = 0, S = 1 : J ≡ LJ ρ, ω, φ (JPC = 1−−) Parity P = (−1)L+1 Charge Conjugation L = 0, S = 0 : (defined for neutral mesons) − e.g. π (JPC = 0 +) C = (−1)L+S G parity G = C(−1)I 12 GeV CEBAF upgrade has high priority (DOE Office of Science, Long Range Plan) “[key area] is experimental verification of the powerful force fields (flux tubes) believed to be responsible for quark confinement.”

Forbidden States (Exotics): PC + + J = 0 −, 0−−, 1− , · · ·

PC 2S+1 J LJ I = 1 I = 0 (nn¯) I = 0 (ss¯) Strange

−+ 1 ′ L = 0 S = 0 0 S0 π η η K −− 3 ∗ S = 1 1 S1 ρ ω φ K +− 1 ′ L = 1 S = 0 1 P1 b1 h1 h 1 K1 ++ 3 ′ ∗ S = 1 0 P0 a0 f0 f 0 K0 ++ 3 ′ S = 1 1 P1 a1 f1 f 1 K1 ++ 3 ′ ∗ S = 1 2 P2 a2 f2 f 2 K2

Notation

1 JPC s are measured quantities.

2S+1 2 LJ s are internal quantum numbers in a non-relativistic quark model.

PC 2S+1 J LJ I = 1 I = 0 (nn¯) I = 0 (ss¯) Strange

−+ 1 ′ L = 0 S = 0 0 S0 π η η K −− 3 ∗ S = 1 1 S1 ρ ω φ K +− 1 ′ L = 1 S = 0 1 P1 b1 h1 h 1 K1 ++ 3 ′ ∗ S = 1 0 P0 a0 f0 f 0 K0 ++ 3 ′ S = 1 1 P1 a1 f1 f 1 K1 ++ 3 ′ ∗ S = 1 2 P2 a2 f2 f 2 K2 Notation

1 JPC s are measured quantities.

2S+1 2 LJ s are internal quantum numbers in a non-relativistic quark model.

Each box corresponds to 4 nonets (2 nonets for L = 0) ) 2 c Mass (GeV/

Lattice calculations: 2 (lightest) M 0++ ≈ 1.55 GeV/c L = qq angular momentum

V. Credé Glueballs and Light-Meson Spectroscopy Introduction and Motivation Experimental Methods in Meson Spectroscopy Glue-Rich Environments Glueballs and Light Mesons Photoproduction The GlueX Experiment at Jefferson Lab Summary and Outlook Outline

Pictures: Ulrich Wiedner

Asterix, Obelix, Crystal Barrel Mark III, DM 2, BES

Different Production Mechanisms

1 J/ψ may convert into 2 gluons and a photon. 2 In pp¯ annihilation, qq¯ pairs annihilate into gluons forming glueballs.

3 Central production: two hadrons scatter WA 79, WA 102 diffractively, no exchange of valence quarks. WA79, WA102

c D c ω c Φ

¯c D ¯c nn¯ ¯c ss¯

The decay of J/ψ into mesons with open charm (left) is forbidden due to energy conservation. The two right diagrams require annihilation of cc¯ into gluons: Recoiling against ω, mesons with nn¯ quark structure are expected. If a φ is observed, we expect mesons with hidden strangeness ss¯. ➜ OZI rule, e.g. ratio φη ′/ωη ′ ∼ ratio of ss¯/nn¯ in η ′ w.f.

Results on light mesons from CLAS at Jefferson Lab − 1 Search for the photo-excitation of exotic mesons in the π+π+π system (M. Nozar et al., Phys. Rev. Lett. 102, 102002 (2009))

×103 300 γ π γ ρ π a. Total b. Background X /f 2 250 π π ρ/f 200 a) 2 π b) P n 150 * p n p ∆/N 100

Events/40 MeV π 50 charge exchange × 3 160 10 CLAS ++ -+ 140 c. 2 (ρ π ) d. 2 120 D 100 80 60 The authors don’t observe a resonant 40 Events/40 MeV −+ 20 structure in the 1 (ρπ)P partial wave. 0 1 1.2 1.4 1.6 1.8 2 1 1.2 1.4 1.6 1.8 2 M(π+π+π-) (GeV) M(π+π+π-) (GeV)

Results on light mesons from CLAS at Jefferson Lab − 1 Search for the photo-excitation of exotic mesons in the π+π+π system (M. Nozar et al., Phys. Rev. Lett. 102, 102002 (2009))

×103 70 π π π a. -+ -+ γ γγ − ρ ρ π b. π X X /f 2 60 2 ( ) 2 (f ) π π π P,F 2 S ρ ρ π 50 /f /f a) 2 π a) b) 2 π 40 P P ? n * 30 ∆/ p n p p N np 20

Events/40 MeV π 10 charge exchange neutral exchange

×103 50 CLAS E852 45 c. ++ d. -+ ρ π ρ π 40 1 ( ) 1 ( ) S P 35 π 1(1600)? 30 25 20 15 The authors don’t observe a resonant 10 Events/40 MeV −+ 5 structure in the 1 (ρπ)P partial wave. 0 1 1.2 1.4 1.6 1.8 2 1 1.2 1.4 1.6 1.8 2 M(π+π+π-) (GeV) M(π+π+π-) (GeV)

Results on light mesons from CLAS at Jefferson Lab − 1 Search for the photo-excitation of exotic mesons in the π+π+π system (M. Nozar et al., Phys. Rev. Lett. 102, 102002 (2009))

γ π γγ − ρ π π X π π X /f 2 π ρ ρ π /f 2 /f 2 PC + a) π a) b) π A J = 1− gluonic hybrid should be P P ? n ∆/ * photo-produced at the same rate as the p n p p N np π a 2(1320), whereas in pion production it charge exchange neutral exchange should be suppressed by a factor of 10. CLAS E852 (Close & Page, Phys. Rev. D 52, 1706 (1995))

Upper limit for the π1(1600) of 13.5 nb, less than 2 % of the a 2(1320). New HyCLAS data have an order of magnitude more statistics. + + + 0 PC + ➜ e.g. γp → p π π π−, γp → p π π−π (J = 1− isoscalar production?) GlueX proposed to map out the light exotic spectrum.

Results on light mesons from CLAS at Jefferson Lab − 1 Search for the photo-excitation of exotic mesons in the π+π+π system (M. Nozar et al., Phys. Rev. Lett. 102, 102002 (2009))

2 First measurement of direct f0(980) photoproduction on the proton (M. Battaglieri et al., Phys. Rev. Lett. 102, 102001 (2009))

3 Production and decay of the f1/η (1285)[in the g11 data set ] (R. Dickson et al., Ph.D. thesis)

γ p → p π+ π- η Channel Measurements 50000 ηππ dσ/dΩ, mass, and Γ 40000 η' x(1280) a π Dalitz plot analysis 30000 0 5 20000 1.5 10 Events, PDG Properties ∼ · KK π dσ/dΩ, B. F. 10000 ++ 0 f1(1285) 1 , Γ = 24 MeV ρ γ B. F. (upper limit) 0 −+ 0.9 1 1.1 1.2 1.3 1.4η( 1.51295) 0 , Γ = 55 MeV MM(γ,p) GeV

Name Mass [ MeV/c2 ] Width [ MeV/c2 ] Decays η(548) ∗ 547.51 ± 0.18 1.30 ± .07 keV γγ, 3π η ′(958) ∗ 957.78 ± 0.14 0.203 ± 0.016 ηππ, ργ, ωγ, γγ

η(1295) ∗ 1294 ± 4 55 ± 5 ηππ, a0π, γγ, ησ, K K¯ π

η(1405) ∗ 1409.8 ± 2.5 51.1 ± 3.4 K K¯ π, ηππ, a0π, f0η, 4π ∗ η(1475) ∗ 1476 ± 4 87 ± 9 K K¯ π, K K¯ + cc, a0π, γγ η(1760) 1760 ± 11 60 ± 16 ωω, 4π +300 ¯ ¯ η(2225) 2220 ± 18 150−60 ± 60 K K K K

Five pseudoscalar states < 1500 MeV/c2 listed in the PDG summary table ➜ Too many for two nonets!!

In 1990, Mark III reported two pseudoscalar states in the 1400 MeV/c2 region ∗ in radiative J/ψ decays (with J/ψ → a0(980)π and J/ψ → K K ). Both states conﬁrmed by Crystal Barrel and Obelix at LEAR But: CB did NOT observe the η(1295)

4940 Breite Width 50 MeV 56 MeV 4800 56 MeV 64 MeV 47 MeV 4920 80 MeV 40 MeV 100 MeV CB 110 MeV 64 MeV 120 MeV 4600 72 MeV 4900 140 MeV 80 MeV 88 MeV 96 MeV 4880 4400 4860

4200 4840

+ + 4820 4000 pp¯ → π π−π π−η 4800 1200 1250 1300 1350 1400 1450 1500 1550 1600 1400 1450 1500 1550 1600

In 2001, L3 observed η(1475) → K K¯ π in two-photon collisions. No observation by L3 of the second state, the η(1405) ➜ Glueball?

In 2001, L3 observed η(1475) → K K¯ π in two-photon collisions. No observation by L3 of the second state, the η(1405) ➜ Glueball? In 2005, CLEO published (high-statistics) negative results on both states.

V. Credé Glueballs and Light-Meson Spectroscopy Introduction and Motivation Experimental Methods in Meson Spectroscopy The Quest for the Scalar Glueball Glueballs and Light Mesons Exotic Hybrid Mesons The GlueX Experiment at Jefferson Lab Summary and Outlook The Flavor Filter in the Decay J/ψ → γ[γV ] BES-II studied J/ψ → γγV (ρ, φ) Clear observation of peak at M ≈ 1424 MeV/c2 in X(1424) → γρ (left) No observation of X(1424) → γφ (right)! ➜ Glueball should decay to both ﬁnal states.

η ′

V. Credé Glueballs and Light-Meson Spectroscopy Introduction and Motivation Experimental Methods in Meson Spectroscopy The Quest for the Scalar Glueball Glueballs and Light Mesons Exotic Hybrid Mesons The GlueX Experiment at Jefferson Lab Summary and Outlook What about the η(1295)? Often interpreted as ﬁrst radial excitation of the η meson. Ideal mixing: degenerate in mass with π(1300) Problem: only observed in pion-induced reactions!

a 0π E852

η → a0(980)π

η(ππ)S total

First photoproduction measurements of x(1280) (Preliminary conclusions from talk at APS Spring Meeting 2009)

Mass and width of the state consistent with the PDG values for f1(1285), not the η(1295) Cross sections being compared to models for both 0− and 1+

Dalitz plot analysis of ηππ final state shows clear a0(980) intermediate state, with no charge asymmetry γ p → p π+ π- η 50000 KK π and ηππ final states measured; 40000 η' x(1280) no ρ0γ final state seen ➜ 30000 inconsistent with f1(1285) 20000 0 (PDG: (5.5 ± 1.3) % for f1 → γρ ) 10000

0 0.9 1 1.1 1.2 1.3 1.4 1.5 MM(γ,p) GeV

Evidence essentially non-existent! Name Mass [ MeV/c2 ] ∗ ± Two quark conﬁgurations yield 2++: f2(1270) 1275.4 1.1 3 f2(1430) 1430 1 L = 1, S = 1, J = 2 : P2 ➜ f2′(1525) ∗ 1525 ± 5 3 2 L = 3, S = 1, J = 2 : F2 f2(1565) 1546 ± 12

For both nonets, radial excitations are f2(1640) 1638 ± 6

expected. f2(1810) 1815 ± 12

Situation premature: none of the states f2(1910) 1915 ± 7

can be assigned deﬁnitely to any of the f2(1950) ∗ 1944 ± 12 above nonets. ∗ +60 f2(2010) 2011 80 − f2(2150) 2156 ± 11

f2(2300) ∗ 2297 ± 28

f2(2340) ∗ 2339 ± 60

Name Mass [ MeV/c2 ] Width [ MeV/c2 ] Decays f0(600) ∗ 400 − 1200 600 − 1000 ππ, γγ f0(980) ∗ 980 ± 10 40 − 100 ππ, K K¯ , γγ f0(1370) ∗ 1200 − 1500 200 − 500 ππ, ρρ, σσ, π(1300)π, a1π, ηη, K K¯ f0(1500) ∗ 1507 ± 5 109 ± 7 ππ, σσ, ρρ, π(1300)π, a1π, ηη, ηη ′ K K¯ , γγ f0(1710) ∗ 1718 ± 6 137 ± 8 ππ, K K¯ , ηη, ωω, γγ f0(1790) f0(2020) 1992 ± 16 442 ± 60 ρππ, ππ, ρρ, ωω, ηη f0(2100) 2103 ± 7 206 ± 15 ηππ, ππ, ππππ, ηη, ηη ′ f0(2200) 2189 ± 13 238 ± 50 ππ, K K¯ , ηη

Crystal Barrel a pp¯ → π0ηη b pp¯ → π0π0η c pp¯ → π0π0π0 0 d pp¯ → π KLKL

Good description with Two isoscalar states:

f0(1370) / f0(1500) In addition: Both have dominant 4π decay modes. ➜ nn¯ structure

V. Credé Glueballs and Light-Meson Spectroscopy

UNCORRECTED PROOF Introduction and Motivation Experimental Methods in Meson Spectroscopy The Quest for the Scalar Glueball Glueballs and Light Mesons Exotic Hybrid Mesons The GlueX Experiment at Jefferson Lab Summary and Outlook

The f0(1710) Scalar Meson in Crystal Barrel First discovered by Crystal-Ball in radiative J/ψ decays into ηη Spin (J = 0 or 2) remained controversial for a long time No satisfactory Crystal Barrel signal around 1700 MeV/c2 for a scalar or a tensor state in π0π0π0 or π0ηη

2.5 120 700 2.25 D 100 2 600

]

2 1.75 80 500

1.5 400 60 ) [GeV 1.25

πη 300 ( 40 2 1

m 200 0.75 20 100

0.5 number of events / 13.3 MeV

0.25 0 0 0.25 0.5 0.75 1 1.25 1.5 1.75 2 2.25 2.5 1000 1200 1400 1600 1800 2000 πη m 2( πη ) [GeV 2] m( ) [MeV]

The f0(1710) Scalar Meson First discovered by Crystal-Ball in radiative J/ψ decays into ηη Spin (J = 0 or 2) remained controversial for a long time No satisfactory Crystal Barrel signal around 1700 MeV/c2 for a scalar or a tensor state in π0π0π0 or π0ηη Consistent with a dominant ss¯ assignment ➜ Conﬁrmed by WA102 reporting a much stronger K K¯ coupling of f0(1710) than ππ coupling

2000 1500 1000 Flavor Tagging 500 Evts/25MeV 200 150 + − ➜ 2 100 ωK K Peak around 1700 MeV/c 50 Evts/25MeV 500 (OZI rule: nn¯ structure) 400 300 200 100 Evts/30MeV 500 400 300 + − 2 200 φK K ➜ No peak around 1700 MeV/c 100 Evts/30MeV 4000 3000 2000 1000 Evts/25MeV 750

500

250 Evts/25MeV 200 150 100 50 Evts/25MeV 0 0.25 0.5 0.75 1 1.25 1.5 1.75 2 2.25 π+π-/K+K- Mass (GeV/c2)

2000 1500 1000 Flavor Tagging 500 Evts/25MeV 200 150 + − ➜ 2 100 ωK K Peak around 1700 MeV/c 50 Evts/25MeV 500 (OZI rule: nn¯ structure) 400 300 + − 2 200 φπ π ➜ Enhancement at 1790 MeV/c 100 Evts/30MeV 500 400 300 + − 2 200 φK K ➜ No peak around 1700 MeV/c 100 Evts/30MeV 4000 3000 Solution: Two distinct scalar states 2000 1000 Evts/25MeV ¯ 750 The known f0(1710) decaying to K K

500

250 New broad f0(1790) coupling strongly to ππ Evts/25MeV 200 150 Not conﬁrmed by other experiments! 100 50 ¯ Evts/25MeV Mystery why ss recoils against ω 0 0.25 0.5 0.75 1 1.25 1.5 1.75 2 2.25 π+π-/K+K- Mass (GeV/c2)

Belle measured scalar mesons in B+ → K +π+π− and B+ → K +K +K − (Results essentially conﬁrmed by BaBar) 2 No peak at 1500 MeV/c for the f0(1500) (left), But a clear peak around 1500 MeV/c2 decaying to K +K − ➜ Structure of f0(1500) remains unclear (or two states)!

V. Credé Glueballs and Light-Meson Spectroscopy Introduction and Motivation Experimental Methods in Meson Spectroscopy The Quest for the Scalar Glueball Glueballs and Light Mesons Exotic Hybrid Mesons The GlueX Experiment at Jefferson Lab Summary and Outlook Results on Scalar Mesons from γγ Fusion Results were reported by the LEP collaborations at CERN: 0 0 Three clear peaks in the KS KS mass by L3 (dominated by tensors)

No peak for the f0(1500) ➜ Consistent with known small ss¯ component! What about ππ spectrum? L3 80 f2Â(1525) Data Fit 60

f (1270) 2 f (1710) a (1320) J 40 2

Events / 30 MeV 20 ξ(2230)

0 1.5 2 2.5 o o m(KsKs) (GeV)

V. Credé Glueballs and Light-Meson Spectroscopy Introduction and Motivation Experimental Methods in Meson Spectroscopy The Quest for the Scalar Glueball Glueballs and Light Mesons Exotic Hybrid Mesons The GlueX Experiment at Jefferson Lab Summary and Outlook Results on Scalar Mesons from γγ Fusion Results were reported by the LEP collaborations at CERN: 0 0 Three clear peaks in the KS KS mass by L3 (dominated by tensors)

No peak for the f0(1500) ➜ Consistent with known small ss¯ component! What about ππ spectrum?

8000 ALEPH L3 7000 80 6000 f2Â(1525) Data 5000 Events / 20 MeV Fit 4000 60 3000

f2(1270) 2000 fJ(1710) a2(1320) 40 1000 (a)

500

Events / 30 MeV 20 ξ(2230) 0

-500 (b) 0 1.5 2 2.5 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 o o ππ invariant mass (GeV/c2) m(KsKs) (GeV)

The following key questions account for the major differences in the models on scalar mesons and need to be addressed in the future:

1 What is the nature of the f0(980) and a0(980)? (There is the possibility of an exotic nonet below 1 GeV/c2.)

The following key questions account for the major differences in the models on scalar mesons and need to be addressed in the future:

1 What is the nature of the f0(980) and a0(980)? (There is the possibility of an exotic nonet below 1 GeV/c2.)

2 Is the f0(1370) a true qq¯ resonance or of different nature, e.g. generated by ρρ molecular dynamics? Or perhaps, it does not exist ...

The following key questions account for the major differences in the models on scalar mesons and need to be addressed in the future:

1 What is the nature of the f0(980) and a0(980)? (There is the possibility of an exotic nonet below 1 GeV/c2.)

2 Is the f0(1370) a true qq¯ resonance or of different nature, e.g. generated by ρρ molecular dynamics? Or perhaps, it does not exist ...

3 Is the f0(1500) the scalar glueball? Data on J/ψ → γf0(1500) is still statistically limited ➜ BES-III

The following key questions account for the major differences in the models on scalar mesons and need to be addressed in the future:

1 What is the nature of the f0(980) and a0(980)? (There is the possibility of an exotic nonet below 1 GeV/c2.)

2 Is the f0(1370) a true qq¯ resonance or of different nature, e.g. generated by ρρ molecular dynamics? Or perhaps, it does not exist ...

3 Is the f0(1500) the scalar glueball? Data on J/ψ → γf0(1500) is still statistically limited ➜ BES-III

4 Are the two states, f0(1710) and f0(1790) distinct states? 5 ...

There is convincing evidence for an exotic JPC = 1−+ wave. ➜ The interpretation remains controversial. Exotic waves are (all) observed in diffraction-like reactions. ➜ Observation of π1(1400) → ηπ in pp¯ remains exception.

Hybrid-Meson Decays: (angular momentum in the ﬂux tube stays in one of the daughter mesons)

+− + − 0 0 0 L = 1 0 → b1π → π π π π π −+ + − + − 1 → a1π → π π π π

→ f1π → ηπππ ➜ Multi-particle ﬁnal states with L = 0 Lattice calculations: neutral and charged particles! 2 (lightest) M 1−+ ≈ (1.9 ± 0.2) GeV/c

In summary: ′ 1 π1(1400) → ηπ =6 π1(1400) → ρπ (CB & Obelix, Proceedings 2004) ➜ Tetraquark? (too low in mass for hybrid, decuplet state)

π1(1400) → ηπ E852, Phys. Rev. D60 (1999) 092001. 8 Resonant Interpretation <> VES, Phys. Atom. Nuc. D 68 (2005) 3. Crystal Barrel, Phys. Lett. B 423 (1998) 175. :> Non-Resonant Interpretation n E852 (IU), Phys. Rev. Lett. 91 (2003) 092002.

In summary: ′ 1 π1(1400) → ηπ =6 π1(1400) → ρπ (CB & Obelix, Proceedings 2004) ➜ Tetraquark? ′ -+ ++ 2 π1(1600)[→ η π, → f1(1285)π] 1 2

In summary: ′ 1 π1(1400) → ηπ =6 π1(1400) → ρπ (CB & Obelix, Proceedings 2004) ➜ Tetraquark? (too low in mass for hybrid, decuplet state) ′ ′ 2 π1(1600)[→ η π, → f1(1285)π] =6 π1(1600)[→ ρπ, → b1(1235)π] ′ − − → η π : dominant 1 + partial wave (E852, 2001; VES, 2005) → ρ0π−: small relative structure with leakage from other waves (Evidence: E852, ’02; COMPASS, ’09; Negative: VES, ’04; IU, ’06; CLAS, ’09) −+ → b1(1235)π/f1(1285)π: structure in 1 partial wave (E852, ’05, ’04; VES, ’99, ’05)

The 12 GeV upgrade is under construction. Construction of Hall-D broke ground in April 2009. Construction of the GlueX detector has started. Current plans call for the ﬁrst beam in HallD/GlueX in late 2014.

Pion Beam Photon Beam π with S = 0, L = 0 and m = 1 γ with S = 1, L = 0 and m = 1 PC ++ PC + + + + ➜ J = 1 , 1−− ➜ J = 0− , 0 −, 1− , 1 −, ... Spin ﬂip required for exotic quantum No spin ﬂip needed for exotic QN’s numbers

High, and reasonably uniform acceptance up to 2.5 GeV/c2. Sensitive to charged particles and photons. Some particle ID in the initial phases, plans to upgrade this. Able to fully reconstruct the 4-12 particle ﬁnal states.

➜ π0η Photoproduction

QCD predicts glueballs and nonets of mesons with exotic quantum numbers. There is fair evidence for a scalar glueball. There are hints for some states with exotic quantum numbers; two states are consistent with a π1 state. What about the other states? ➜ We have just started to see results from COMPASS. The first searches in photoproduction have come up negative, but the acceptance has been poor, and the lower energy regime may not have been optimal. The GlueX experiment at Jefferson Lab is now under construction with first beam in the hall expected in 2014. GlueX has high acceptance for multi-particle final states, sensitivity to photons, and a linearly-polarized photon beam.

+,-'&( (ωρ )

+,-'&( (a 0(980) η$ηηπ )

+,-'&( (f 0(1500) $ηηπ ) +,-'&( (σπ $3π )

+,-'&( (f o(980) π$3π)

* P ) (ηηπ ) ) *(3 π)

D * * ) (K 0(1430)K)

G ) *(ηη 'π) Average 1816 ±14

$%%&$'(& $'%& MeV/c 2 * Mass & Uncertainty PDG 2008

118.1 o 14.7 o 126.4 o 10.8 o

185cm

342cm 48cm

560cm Magnet and Target 30cm-Target 2 T Solenoid, Superconducting

LH2 Target

118.1 o 14.7 o 126.4 o 10.8 o

!!!!!! ! ! ! ! !!!!!! !!!!!! ! ! ! ! !!!!!! Tracking Chambers !!!!!! ! ! ! ! 185cm !!!!!! ! ! ! ! !!!!!! !!!!!! ! ! ! ! !!!!!! Central Drift Chamber (CDC) !!!!!! ! ! ! ! Straw-Tube Chamber (N = 3522) ➜ d = 1.6 cm, l = 150 cm 342cm (σφ = 150 µm, σz = 1.5 mm) 48cm

dE/dx for PID 560cm 30cm-Target Forward Drift Chamber(s) (FDC) 2304 wires, 10368 cathode strips

σx, y ∼ 200 µm

118.1 o 14.7 o Calorimetry 126.4 o !! 10.8 o !!!!!!!!!!!!!! !! !!!!!!!!!!!!!! !! !!!!!!!!!!!!!! !! Barrel Calorimeter !!!!!!!!!!!!!!!!!!!! ! ! ! ! !! !!!!!! !! !!!!!! ! ! ! ! !! !!!!!! !! !!!!!! ! ! ! ! !! 15.5 radiation lengths !! 185cm !!!!!! ! ! ! ! !! !!!!!! !! σE 5.5 % !!!!!! ! ! ! ! !! ⊕ 1 6 !!!!!! !! E = . % !!!!!!!!!!!!!!!!!!!! ! ! ! ! !! √E !!!!!!!!!!!!!! !! !!!!!!!!!!!!!! !! σ 74 ps !!!!!!!!!!!!!! !! ∆T = ⊕ 33 ps !! E √E

342cm Forward Calorimeter 48cm F8-00 lead glass, 2800 blocks 560cm 30cm-Target 14.5 radiation lengths σE = 5.7 % +2% E √E

σr ≈ 5 − 6 mm

118.1 o 14.7 o 126.4 o !! 10.8 o Timing !!!!!!!!!!!!!! !! !!!!!!!!!!!!!! !! !!!!!!!!!!!!!! !! !!!!!!!!!!!!!!!!!!!! ! ! ! ! !! !!!!!! !! Start Counter !!!!!! ! ! ! ! !! !!!!!! !! !!!!!! ! ! ! ! !! !! 185cm !!!!!! ! ! ! ! !! Event start time !!!!!! !! 8 !!!!!! ! ! ! ! !! ➜ !!!!!! !! Designed to operate at 10 γ / s !!!!!!!!!!!!!!!!!!!! ! ! ! ! !! !!!!!!!!!!!!!! !! !!!!!!!!!!!!!! !! !!!!!!!!!!!!!! !! 40 detectors, 500 mm in length !!

σt ≈ 0.26 ns to 0.16 ns 342cm 48cm

Forward Time-of-Flight 560cm 30cm-Target Two planes of scintillator paddles 250cmx6cmx2.5cm

σ∆t ≈ 80 ps

V. Credé Glueballs and Light-Meson Spectroscopy