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Gluonic Excitations of

Gluonic Excitations of. Hadrons. Curtis A. Meyer Carnegie Mellon University February 7, 2003. Outline of Talk. Introduction Meson Spectroscopy Glueballs Expectations Experimental Data Interpretation Hybrid Mesons Expectations Experimental Data Interpretation

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Gluonic Excitations of

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  1. Gluonic Excitations of Hadrons Curtis A. Meyer Carnegie Mellon University February 7, 2003 Curtis A. Meyer

  2. Outline of Talk • Introduction • Meson Spectroscopy • Glueballs • Expectations • Experimental Data • Interpretation • Hybrid Mesons • Expectations • Experimental Data • Interpretation • The Future Curtis A. Meyer

  3. u c t s d b white white QCD is the theory of quarks and gluons 3 Colors 3 Anti-colors 8 Gluons, each of which has a color an an anti-color Charge. Six Flavors of quarks Curtis A. Meyer

  4. Jets at High Energy Direct evidence for gluons come from high energy jets. But this doesn’t tell us anything about the “static” properties of glue. We learn something about s 2-Jet 3-Jet gluon bremsstrahlung Curtis A. Meyer

  5. Deep Inelastic Scattering As the nucleon is probed to smaller and smaller x, the gluons become more and more important. Much of the nucleon momentum and most of its spin is carried by gluons! Glue is important to hadronic structure. Curtis A. Meyer

  6. white See and systems. white Allowed systems: , , Strong QCD Color singlet objects observed in nature: Nominally, glue is not needed to describe hadrons. Focus on “light-quark mesons” Curtis A. Meyer

  7. Normal Mesons orbital r3,w3,f3,K3 r2,w2,f2,K2 r1,w1,f1,K1 p2,h2,h’2,K2 3-- 2-- 1-- 2-+ L=2 radial s u d a2,f2,f’2,K2 a1,f1,f’1,K1 a0,f0,f’0,K0 b1,h1,h’1,K1 2++ 1++ 0++ 1+- J=L+S L=1 (2S+1) L J s P=(-1) L+1 u d 1S0 = 0 -+ C=(-1) L+S r,w,f,K* p,h,h’,K 1-- 0-+ 3S1 = 1-- L=0 G=C (-1) I Non-quark-antiquark 0-- 0+- 1-+ 2+- 3-+ … quark-antiquark pairs Curtis A. Meyer

  8. Nonet Mixing The I=0 members of a nonet can mix: SU(3) physical states Ideal Mixing: Curtis A. Meyer

  9. Spectrum qq Mesons 2 – + 0 – + 2 + + 2.5 Hybrids 2 + – 2 – + 2.0 1 – – Glueballs 1– + exotic nonets 1 + – 1 + + 1.5 0 + – 0 – + 0 + + 1.0 L = 0 1 2 3 4 Each box corresponds to 4 nonets (2 for L=0) Radial excitations Lattice 1-+ 1.9 GeV 0++ 1.6 GeV (L = qq angular momentum) Curtis A. Meyer

  10. Glueball Mass Spectrum QCD is a theory of quarks and gluons What role do gluons play in the meson spectrum? Lattice calculations predict a spectrum of glueballs. The lightest 3 have JPC Quantum numbers of 0++ , 2++ and 0-+. The lightest is about 1.6 GeV/c2 f0(1710) f0(1500) a0(1450) K*0(1430) f0(1370) Morningstar et al. a0(980) f0(980) Curtis A. Meyer

  11. G M M Glue-rich channels Where should you look experimentally for Glueballs? Radiative J/ Decays 0-+ (1440) 0++ f0(1710) Large signals Proton-Antiproton Annihilation Central Production (double-pomeron exchange) Curtis A. Meyer

  12. Decays of Glueballs? Glueballs should decay in a flavor-blind fashion. ’=0 is true for any SU(3) singlet and for any pseudoscalar mixing angle. Only an SU(3) “8” can couple to ’. Flavor-blind decays have always been cited as glueball signals. Curtis A. Meyer

  13. Crystal Barrel Results Crystal Barrel Results: antiproton-proton annihilation at rest f0(1500) app, hh, hh’, KK, 4p Discovery of the f0(1500) f0(1370) a4p Solidified the f0(1370) Establishes the scalar nonet Discovery of the a0(1450) 250,000 hhp0 Events 700,000 p0p0p0 Events f2(1565)+s f0(1500) f2(1270) f0(980) f0(1500) Curtis A. Meyer

  14. The f0(1500) Is it possible to describe the f0(1500) as a member of a meson nonet? Use SU(3) and OZI suppression to compute relative decays to pairs of pseudoscalar mesons Get an angle of about 143o 90% light-quark 10% strange-quark Both the f0(1370) and f0(1500) are Curtis A. Meyer

  15. WA102 Results CERN experiment colliding p on a hydrogen target. Central Production Experiment Recent comprehensive data set and a coupled channel analysis. Curtis A. Meyer

  16. meson Glueball meson meson meson meson Glueball meson meson Model for Mixing 1 r2 r3 flavor blind? r Solve for mixing scheme F.Close: hep-ph/0103173 Curtis A. Meyer

  17. Meson Glueball Mixing Physical Masses f0(1370),f0(1500),f0(1710) Bare Masses: m1,m2,mG (G) (S) (N) f0(1370)-0.690.07 0.150.01 0.700.07 f0(1500)-0.650.04 0.330.04 –0.700.07 f0(1710)0.390.03 0.910.02 0.150.02 octet piece m1=137720 m2=167410 mG=144324 Lattice of about 1600 Curtis A. Meyer

  18. Glueball Expectations Antiproton-proton: Couples to Observe: f0(1370),f0(1500) Central Production: Couples to G and in phase. Observe: f0(1370),f0(1500), weaker f0(1710). Radiative J/: Couples to G, |1>, suppressed |8> Observe strong f0(1710) from constructive |1>+G Observe f0(1500) from G Observe weak f0(1370) from destructive |1>+G Two photon: Couples to the quark content of states, not to the glueball. Not clear to me that has been seen. Curtis A. Meyer

  19. Higher mass glueballs? Part of the CLEO-c program will be to search for glueballs in radiative J/ decays. Lattice predicts that the 2++ and the 0-+ are the next two, with masses just above 2GeV/c2. Radial Excitations of the 2++ ground state L=3 2++ States + Radial excitations f2(1950), f2(2010), f2(2300), f2(2340)… 2’nd Radial Excitations of the  and ’, perhaps a bit cleaner environment! (I would Not count on it though….) I expect this to be very challenging. Curtis A. Meyer

  20. From G. Bali Lattice QCD Flux Tubes Realized ColorField: 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 Curtis A. Meyer

  21. Hybrid Mesons excited flux-tube m=1 ground-state flux-tube m=0 S=0,L=0,m=1 S=1,L=0,m=1 J=1 CP=+ J=1 CP=- JPC=0-+,0+- 1-+,1+- 2-+,2+- JPC=1++,1-- (not exotic) Flux-tube Model m=0 CP=(-1) S+1 m=1 CP=(-1) S exotic built on quark-model mesons 1-+ or 1+- normal mesons CP={(-1)L+S}{(-1)L+1} ={(-1)S+1} Curtis A. Meyer

  22. QCD Potential excited flux-tube m=1 ground-state flux-tube 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. Curtis A. Meyer

  23. Hybrid Predictions 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 MILC (97) 1.97 0.30 MILC (99) 2.11 0.10 Lacock(99) 1.90 0.20 Mei(02) 2.01 0.10 ~2.0 GeV/c2 1-+ 0+- 2+- Splitting  0.20 In the charmonium sector: 1-+ 4.39 0.08 0+- 4.61 0.11 Splitting = 0.20 Curtis A. Meyer

  24. Decays of Hybrids Decay calculations are model dependent, but the 3P0 model does a good job of describing normal meson decays. 0++ quantum numbers (3P0) The angular momentum in the flux tube stays in one of the daughter mesons (L=1) and (L=0) meson. L=0:,,,,… L=1: a,b,h,f,… ,, … not preferred. 1b1,f1,,a1 87,21,11,9 MeV (partial widths) Curtis A. Meyer

  25. E852 Results p-p -> hp-p (18 GeV) Mass = 1370 +-16+50-30 MeV/c2 Width= 385 +- 40+65-105 MeV/c2 p1(1400) The a2(1320) is the dominant signal. There is a small (few %) exotic wave. p1 a2 Interference effects show a resonant structure in 1-+. (Assumption of flat background phase as shown as 3.) Curtis A. Meyer

  26. CBAR Exotic Crystal Barrel Results: antiproton-neutron annihilation Same strength as the a2. Mass = 1400 +- 20 +- 20 MeV/c2 Width= 310+-50+50-30 MeV/c2 Produced from states with one unit of angular momentum. p1(1400) Without p1c2/ndf = 3, with = 1.29 hp0p- Curtis A. Meyer

  27. Significance of signal. Curtis A. Meyer

  28. E852 Results to partial wave analysis suggests At 18 GeV/c Curtis A. Meyer

  29. Correlation of Phase & Intensity Leakage From Non-exotic Wave due to imperfectly understood acceptance An Exotic Signal Exotic Signal p1(1600) 3p m=1593+-8+28-47G=168+-20+150-12 ph’ m=1597+-10+45-10G=340+-40+-50 Curtis A. Meyer

  30. p1 IG(JPC)=1-(1-+) K1 IG(JPC)= ½ (1-) h’1 IG(JPC)=0+(1-+) h1 IG(JPC)=0+(1-+) Exotic Signals 1(1400)Width ~ 0.3 GeV, Decays: only  weak signal in p production (scattering??) strong signal in antiproton-deuterium. 1(1600) Width ~ 0.3 GeV, Decays ,’,(b1) Only seen in p production, (E852 + VES) In a nonet, there should only be one 1 state. Both of these are lighter than expectations, and The decay modes are not what is expected. Curtis A. Meyer

  31. of Exotics  or  after before beam q q q q  beam Quark spins aligned q q q q Almost no data in hand in the mass region where we expect to find exotic hybrids when flux tube is excited before after Photoproduction Quark spins anti-aligned A pion or kaon beam, when scattering occurs, can have its flux tube excited Much data in hand with some evidence for gluonic excitations (tiny part of cross section) _ _ _ _ Curtis A. Meyer

  32. X Couple to V.M + e g p1  rp e N N h1  rb1 ,wf h’1 fw p1 IG(JPC)=1-(1-+) K1 IG(JPC)= ½ (1-) h’1 IG(JPC)=0+(1-+) h1 IG(JPC)=0+(1-+) Exotics in Photoproduction 1-+ nonet g  ,, Curtis A. Meyer

  33. X b0 IG(JPC)=1+(0+-) g e h0 IG(JPC)=0-(0+-) N N h’0 IG(JPC)=0-(0+-) b2 IG(JPC)=1+(2+-) K0 I(JP)=½(0+) h2 IG(JPC)=0-(2+-) h’2 IG(JPC)=0-(2+-) K2 I(JP)= ½(2+) 0+- and 2+- Exotics In photoproduction, couple to r, w or f? a1,f0,f1 wf0,wf1,ra1 ff0,ff1,ra1 wp, a1,f0,f1 “Similar to p1 ” wh,rp,wf0,wf1,ra1 fh,rp,ff0,ff1,ra1 Kaons do not have exotic QN’s Curtis A. Meyer

  34. Exotics and QCD In order to establish the existence of gluonic excitations, We need to establish the nonet nature of the 1-+ state. We need to establish at other exotic QN nonets – the 0+- and 2+-. In the scalar glueball sector, the decay patterns have provided the most sensitive information. I expect the same will be true in the hybrid sector as well. DECAY PATTERS ARE CRUCIAL Curtis A. Meyer

  35. The Scalar Mesons The Scalar Mesons Overpopulation Strange Decay Patterns Seen in glue-rich reactions Not in glue-poor What about 2++ and 0-+ ? J/Y Decays? Awaiting CLEO-c Glueball and Mesons are mixed. Scheme is model dependent. Crystal Barrel proton-antiproton annihilation Central Production WA102 Three States f0(1370) f0(1500) f0(1710) 0++rr 0++ ss 1.5 2.5 2.5 1.5 Curtis A. Meyer

  36. What will we learn? There is an clear signal for hybrid mesons – Exotic quantum numbers – but confirmation requires the observation of a nonet, not just a single state. Mapping out more than one exotic nonet is necessary to Establishing the hybrid nature of the states. Decay patterns will be useful for the exotic QN states, And necessary for the non-exotic QN states. Curtis A. Meyer

  37. Summary The first round of J/ experiments opened the door to exotic spectroscopy, but the results were confused. LEAR at CERN opened the door to precision, high-statistics spectroscopy experiments and significantly improved both our understanding of the scalar mesons and the scalar glueball. Pion production experiments at BNL (E852) and VES Opened the door to states with non-quark-anti-quark Quantum numbers. CERN central production (WA102) provided solid new data on the scalar sector, and a deeper insight into the scalar glueball. Curtis A. Meyer

  38. The Future The CLAS experiment at Jefferson Lab is opening a small window to meson spectroscopy in photoproduction. CLEO-c will reopen the J/ studies with 100 times Existing statistics. One goal is to find and study the Pseudoscalar (0-+) and tensor glueball (2++) The GlueX experiment will be able to do for hybrids what Crystal Barrel and WA102 (together) did for glueballs. What are the properties of static glue in hadrons and how is this connected to confinement. The antiproton facility at GSI (HESR) will look for hybrids in the charmonium system. Curtis A. Meyer

  39. Gluonic Excitations Workshop at JLab May 14-16, 2003. Curtis A. Meyer

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