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Flux tube forms What do we know about between qq QCD Exotics? Curtis A. Meyer, Carnegie Mellon University What are QCD exotics? Overview of evidence for exotic quantum number states. What does it all mean? May 22, 2003 Curtis A. Meyer 1 Flux tube Normal Mesons forms between Non-quark-antiquark 0-- 0+- 1-+ 2+- 3-+ … quark-antiquark pairs orbital u s d J=L+S P=(-1) L+1 C=(-1) L+S G=C (-1) I May 22, 2003 d s u (2S+1) 1S LJ -+ 0 = 0 3S = 1-1 r3,w3,f3,K3 r2,w2,f2,K2 L=2 r ,w ,f ,K 1 1 1 1 p2,h2,h’2,K2 3-2-1-2-+ a2,f2,f’2,K2 a1,f1,f’1,K1 L=1 a ,f ,f’ ,K 0 0 0 0 b1,h1,h’1,K1 2++ r,w,f,K* L=0 p,h,h’,K 1-0-+ Curtis A. Meyer radial 1++ 0++ 1+- 2 qq Spectrum qq Mesons 2.5 Glueballs 2.0 1.5 between qq Each box corresponds to 4 nonets (2 for L=0) Radial excitations 2 +– 2 –+ 1 –– 1– + 1 +– 1 ++ 0 +– 0 –+ Hybrids 2 –+ 0 –+ 2 ++ Flux tube forms 0 ++ exotic nonets Lattice 1-+ 1.9 GeV 1.0 0++ 1.6 GeV L=0 May 22, 2003 1 2 3 4 (L = qq angular momentum) Curtis A. Meyer 3 Flux tube forms Lattice QCD Flux Tubes Realized Flux tube From G. Bali forms between qq Color Field: Because of self interaction, confining flux tubes form between static color charges Confinement arises from flux tubes and their excitation leads to a new spectrum of mesons May 22, 2003 Curtis A. Meyer 4 between qq Flux tube forms Hybrid Mesons between qq built on quark-model mesons excited flux-tube m=1 ground-state flux-tube m=0 normal mesons CP={(-1)L+S}{(-1)L+1} ={(-1)S+1} Flux-tube Model m=0 CP=(-1) S+1 m=1 CP=(-1) S May 22, 2003 1-+ or 1+- r , w, f S=0,L=0,m=1 S=1,L=0,m=1 J=1 CP=+ J=1 CP=JPC=0-+,0+- JPC=1++,1-- 1-+,1+- (not exotic) exotic Curtis A. Meyer 2-+,2+5 Flux tube QCD Potential forms between qq ground-state excited flux-tube flux-tube m=1 m=0 linear potential Gluonic Excitations provide an experimental measurement of the excited QCD potential. Observations of exotic quantum number nonets are the best experimental signal of gluonic excitations. May 22, 2003 Curtis A. Meyer 6 Flux tube forms between Hybrid Predictions qq Flux-tube model: 8 degenerate nonets 1++,1-- 0-+,0+-,1-+,1+-,2-+,2+- ~1.9 GeV/c2 S=0 S=1 Lattice calculations --- 1-+ nonet is the lightest UKQCD (97) 1.87 0.20 ~2.0 GeV/c2 MILC (97) 1.97 0.30 -+ 1 MILC (99) 2.11 0.10 Splitting 0.20 0.50 +0 Lacock(99) 1.90 0.20 +2 Mei(02) 2.01 0.10 In the charmonium sector: 1-+ 4.39 0.08 Splitting = 0.20 +0 4.61 0.11 May 22, 2003 Curtis A. Meyer 7 Flux tube forms Decays of Hybrids The angular momentum in the flux tube stays in one of the daughter mesons (L=1) and (L=0) meson. between qq Lflux Exotic Quantum Number Hybrids p1 pb1 , pf1 , pr , ha1 h1p(1300)p , a1p 1:.25:.25:.20 1:1 b2 a1p , h1p , wp , a2p h2 b1p , rp , wh 1:1:0.5:0.25 1:1:0.1 b0 p(1300)p , h1p h 0 b 1p , h 1h 1:0.20 1:0.02 May 22, 2003 Curtis A. Meyer Mass and model dependent predictions 8 Exotic Quantum Numbers 1-+ in hp Flux E852 Results tube forms between qq Mass = 1370 +-16+50-30 MeV/c2 p1(1400) Width= 385 +- 40+65 2 -105 MeV/c The a2(1320) is the dominant signal. There is a small (few %) exotic wave. p-p -> hp- p (18 GeV) p1 a2 Interference effects show a resonant structure in 1-+ . (Assumption of flat background phase as shown as 3.) May 22, 2003 Curtis A. Meyer 9 Exotic Quantum Numbers 1-+ in hp Flux tube Crystal Barrel forms between qq Same strength as the a2. p1(1400) Mass = 1400 +- 20 +- 20 MeV/c2 Width= 310+-50+50-30 MeV/c2 Produced from states with one unit of angular momentum. Without p1 c2/ndf = 3, with = 1.29 hp0p- May 22, 2003 Curtis A. Meyer 10 Flux tube forms between qq Significance of signal. May 22, 2003 Curtis A. Meyer 11 E852 Results Exotic Quantum Numbers 1-+ in rp - + - - p pp p p p + - p p p + - - M(p p p ) At 18 GeV/c + - p p GeV / c 2 - M(p p ) GeV / c + to partial wave analysis - 2 suggests p - p r0 p - p p+ p - p - p May 22, 2003 Curtis A. Meyer 12 Flux tube forms between qq Exotic Quantum Numbers 1-+ in rp Flux tube E852 Results forms between qq Correlation of Phase & Intensity 1-+ Exotic Signal p1(1600) Leakage From Non-exotic Wave due to imperfectly understood acceptance May 22, 2003 + - - M(p p p ) GeV / c 2 3p m=1593+-8+28-47 G=168+-20+150-12 Curtis A. Meyer 13 Exotic Quantum Numbers 1-+ in h’p The p1(1600) is the Dominant signal in h’p. Mass = 1.5970.010 GeV Width = 0.3400.040 GeV p1(1600) h’p May 22, 2003 Curtis A. Meyer Flux tube E852 Results forms between qq p-p h’p-p at 18 GeV/c 14 Exotic Quantum Numbers 1-+ in f1p and b1p p-p hp+p-p-p p-p wp0p-p E852 Results Flux tube forms between qq p1(1600) b1p p1(1600) f1p Mass=1.7090.024 GeV Width=0.4030.08 GeV In both b1p and f1p, observe Excess intensity at about 2GeV/c2. Mass ~ 2.00 GeV, Mass = 1.6870.011 GeV Width ~ 0.2 to 0.3 GeV Width = 0.2060.03 GeV May 22, 2003 Curtis A. Meyer 15 Exotic Quantum Numbers 1-+ in rp, b1p and h’p Flux VES Results m=1.60.02 GeV/c2 G=0.290.03 GeV/c2 p1(1600) observed in pA reactions b1p : h’p : rp = 1 : 1.00.3 : 1.6 0.4 p-Awpp (A) (at 37 GeV/c) b1p (1-+) Phase wrt 2+ May 22, 2003 Curtis A. Meyer 16 tube forms between qq Exotic Signals Flux tube forms between qq p1(1400) Width ~ 0.3 GeV, Decays: only hp weak signal in pp production (scattering??) strong signal in antiproton-deuterium. p1(1600) Width ~ 0.16 to 0.3 GeV, Decays rp,h’p,(b1p,f1p) Only seen in pp production, (E852 + VES) In a nonet, there should only be one p1 state. p1 IG(JPC)=1-(1-+) K1 IG(JPC)= h1 IG(JPC)=0+(1-+) ½ (1-) h’1 IG(JPC)=0+(1-+) Both of these are lighter than expectations, and The h[h’]p decay modes are not what are expected. May 22, 2003 Curtis A. Meyer 17 Flux tube Interpretation forms between qq A recent paper by A. Szczepaniak explains the hp and h’p as a background meson-meson interaction. - Fits the E852 data, with the background similar to pp. Is the p1(1400) a 4-quark object? Is the p1(1600) the lightest hybrid? - Recent lattice work indicates that it may be possible to push the masses down. May 22, 2003 Curtis A. Meyer 18 Flux tube forms between Summary qq We have clear experimental evidence for something outside of the simple quark-antiquark picture of mesons. How we interpret these signals is still an open question. New data with particular emphasis on both I=0 states, and other exotic QN states will be needed to solve this. May 22, 2003 Curtis A. Meyer 19