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GlueX: Search for Gluonic Excitations at JLab

GlueX: Search for Gluonic Excitations at JLab. David Lawrence Jefferson Lab. Motivation. Simplest quark-structure is a meson. Meson Wave Function. Confinement: Quarks cannot exist alone. Hybrid Models. Bag Model Flux Tube Model Constituent Gluon Model QCD Sum Rules +

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GlueX: Search for Gluonic Excitations at JLab

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  1. GlueX: Search for Gluonic Excitations at JLab David Lawrence Jefferson Lab GlueX/Exotics 2005

  2. Motivation Simplest quark-structure is a meson Meson Wave Function Confinement: Quarks cannot exist alone GlueX/Exotics 2005

  3. Hybrid Models • Bag Model • Flux Tube Model • Constituent Gluon Model • QCD Sum Rules + • Lattice Gauge Theory (model indep.) GlueX/Exotics 2005

  4. The Flux Tube Model G. Bali GlueX/Exotics 2005

  5. ~1GeV mass difference Hybrid Mesons GlueX/Exotics 2005

  6. + = S = 0 L = 0 JPC = 0-+ (, K) Hybrid Mesons L = 1 JPC = 1-+ , 1+- JPC = 1-- , 1++ Hybrid Meson or , , , … ? GlueX/Exotics 2005

  7. + = S = 1 L = 0 JPC = 1-- (, ) Exotic! Hybrid Mesons L = 1 JPC = 1-+ , 1+- JPC = 0-+, 1-+, 2-+ 0+-, 1+-, 2+- GlueX/Exotics 2005

  8. Hybrids Should Appear as a Nonet 9 hybrid particles Should exist for each JPC combination GlueX/Exotics 2005

  9. 1-+ Hybrid Mass spectrumFrom LQCD calculations. All masses in GeV/c2 / Collaboration UKQCD(97) 1.87 + 0.2 2.0 + 0.2 MILC(97) 1.97 + 0.09 + 0.30 2.170+0.080+0.30 MILC(99) 2.11 + 0.10 + (sys) SESAM(98) 1.9 + 0.20 Mei & Luo(03) 2.013 + 0.026 + 0.071 Bernard et al.(04) 1.792 + 0.139 2.100 + 0.120 GlueX/Exotics 2005

  10. Light Meson Spectrum Exotic quantum numbers imply deeper structure than simple (No mixing with those states!) GlueX/Exotics 2005

  11. Why Are Hybrids Hard To See? • Most searches involve looking at twobody final states. Coupling of hybrids totwo body final states is almost nonexistent • “Large” masses (~2GeV/c2) • About 1/3 of the (exotic) states havebroad widths GlueX/Exotics 2005

  12. Hybrid Decays Hybrids preferentially couple to states with Both an S-wave and P-wave meson X  b1           X  f1             X  a2 X  a1          GlueX/Exotics 2005

  13. Hybrid Candidates(?) 1(1400) 1-+ E852,Crys. Barrel,VES 1(1600) 1-+ E852,Crys. Barrel,VES 1(2000) 1-+ E852 2(1880) 2-+ E852 a1(2096) 1++ E852 GlueX/Exotics 2005

  14. Decay modes not “hybrid-like” 1(1400) JPC = 1-+ (Looks like a meson-meson molecule!) GlueX/Exotics 2005

  15. 1(1600) JPC = 1-+ E852 PRL 86, 3977 (2001) GlueX/Exotics 2005

  16. 1(2000) JPC = 1-+ f1(1285) E852 hep-ex/0405044 v1 (2004) ; E852 Phys. Lett. B595(2004) 109-117 GlueX/Exotics 2005

  17. ,K  Hadroproduction vs. Photoproduction Non-Exotic Exotic* GlueX/Exotics 2005

  18. Incident Photon Energy Need at least E = 8.4GeV - 9GeV to access masses upto 2.8GeV/c2 GlueX/Exotics 2005

  19. Linearly Polarized s(produced by coherent bremsstrahlung) Having the angle between the photon polarization vector and reaction plane  provides an additional handle in the analysis that can simplify the PWA by a factor of 2. The angle  is related to naturality of exchange particle e. GlueX/Exotics 2005

  20. Location of Jefferson Lab GlueX/Exotics 2005

  21. add Hall D (and beam line) Upgrade magnets and power supplies CHL-2 Enhance equipment in existing halls Jlab Upgrade GlueX/Exotics 2005

  22. The GlueX Detector 1 GlueX/Exotics 2005

  23. The GlueX Detector(all aboard!) GlueX/Exotics 2005

  24. Acceptance of GlueX detector p → 1 p → +−4 p GJ cosGJ GlueX/Exotics 2005

  25.   X   p n PWA Double Blind Monte Carlo Study of 3 Final states p → 1+n → ++−n → +00n Background waves included a1(1260), a2(1320) and 2 (1670) GlueX/Exotics 2005

  26. Protoyping and Testing GlueX/Exotics 2005

  27. Beam Flux and Event Rate Eelectron = 12GeV Coherent Peak E = 9GeV In the first year, GlueX will exceed existing photoproduction data by a couple of orders of magnitude. It will also exceed existing hadroproduction data. GlueX/Exotics 2005

  28. Status of Upgrade DOE Order 413.3 Project Management Manual CD-0 Approve Mission Need FY2004 CD-1 Approve Preliminary Baseline Range FY2005 CD-2 Approve Performance Baseline Range FY2007 CD-3 Approve Start of Construction FY2008 CD-4 Approve Start of Operations FY2012 GlueX/Exotics 2005

  29. Summary • Understanding confinement means understanding the glue which binds quarks. Hybrid mesons are perhaps the most promising subject for studying the nature of the glue • A rich spectrum of hybrid mesons is predicted. Models agree the masses of hybrid states should be around 2GeV, some with exotic JPC. GlueX/Exotics 2005

  30. Summary • GlueX is being constructed to map out the spectrum of Exotic Hybrid Mesons with unprecedented statistics. • GlueX will begin taking data in 2011 GlueX/Exotics 2005

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