Introduction and Motivation Experimental Methods in Meson Spectroscopy Glueballs and Light Mesons The GlueX Experiment at Jefferson Lab Summary and Outlook Glueballs and Light-Meson Spectroscopy 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 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 The Quark Model of Hadrons Mesons (qq) q ⊗ q = 3 ⊗ 3 = 8 ⊕ 1 Baryons (qqq) q ⊗ q ⊗ q = 3 ⊗ 3 ⊗ 3 = 10 ⊕ 8 ⊕ 8 ⊕ 1 | {z } Ordinary matter ... 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 The Quark Model of Hadrons 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 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 Ordinary Mesons 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 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 Ordinary and Exotic Mesons 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− , · · · 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 Mesons and their Quantum Numbers 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. 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 Mesons and their Quantum Numbers 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. 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 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 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 Glue-Rich Environments Glueballs and Light Mesons Photoproduction The GlueX Experiment at Jefferson Lab Summary and Outlook Glue-Rich Environments 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 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 The OZI Rule and Flavor-Tagging Approach 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. 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 Meson Spectroscopy in Photoinduced Reactions 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) 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 Meson Spectroscopy in Photoinduced Reactions 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) V.