1 / 29

GlueX: Photoproduction of Hybrid Mesons

GlueX: Photoproduction of Hybrid Mesons. Elton S. Smith, Jefferson Lab for the GlueX Collaboration 12th International Workshop on Meson Production, Properties and Interaction. Hybrid mesons – masses and decay modes Expectations from LQCD and models Photoproduction and GlueX.

rangle
Download Presentation

GlueX: Photoproduction of Hybrid Mesons

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. GlueX: Photoproduction of Hybrid Mesons Elton S. Smith, Jefferson Lab for the GlueX Collaboration 12th International Workshop on Meson Production, Properties and Interaction Hybrid mesons – masses and decay modes Expectations from LQCD and models Photoproduction and GlueX

  2. Quarks are confined inside colorless hadrons q q q q q q q q q q q q q q q q q q q q Quarks combine to “neutralize” color force q mesons baryons Allowed by QCD, but do they exist in nature? molecules pentaquark glueball meson hybrid meson

  3. Normal Mesons – qq color singlet bound states K* w r f K* K0 JPC = 0– +0++1– – 1+ –2++ … Allowed combinations JPC = 0– –0+ –1– +2+ – … Not-allowed: exotic Spin/angular momentum configurations & radial excitations generate the known spectrum of light quark mesons. Starting with u - d - s we expect to find mesons grouped in nonets - each characterized by a given J, P and C. Spin 0 Spin 1 S2 S = S1 + S2 J = L + S P = - (-1)L C = (-1)L+S K0 K+ S1 L h’ p0 p+ p− h K−

  4. Families of Exotics K1 IG(JPC)= ½ (1-) X g e N N h’1 IG(JPC)=0+(1-+) h1 IG(JPC)=0+(1-+) 1-+nonet p1 IG(JPC)=1-(1-+) Couple to vector meson + exchanged particle p1  rp h1  rb1 ,wf g  ,, h’1 fw

  5. Meson Spectroscopy from LQCD exotics normal mesons Isovector mesons, mp~700 MeV Dudek PRD 83 (2011) 111502 Friday Plenary 3 Dudek PRD 84 (2011) 074023

  6. Meson Spectroscopy from LQCD exotics normal mesons Isovector mesons, mp~700 MeV Dudek PRD 83 (2011) 111502 Friday Plenary 3 Dudek PRD 84 (2011) 074023

  7. Meson Spectroscopy from LQCD exotics normal mesons Isovector mesons, mp~700 MeV Dudek PRD 83 (2011) 111502 Friday Plenary 3 Dudek PRD 84 (2011) 074023

  8. Extrapolation to physical mass At mp=400 MeV, mass (1−+) ~ 1.9 GeV, mass (0+−) ~ 2.5 GeV

  9. Models for hybrid mesons Isgur Phys Rev Lett 54 (1985) 869 Mass (GeV) 0−+ 1−− 2+− 0−+ 1−− 2+− 1+− 2−+ 1−+ 0+− 2−+ 1−+ 0+− 1++ Lattice QCD Flux Tube JgPC=1+− and 1-+

  10. Models for hybrid mesons Cotanch NP A689 (2001) 481 Mass (GeV) 0−− 3−+ 1−+ 0−+ 1−− 2+− 2−+ 1−+ 0+− 0++ 1+− 1++ 2++ Lattice QCD Effective QCD Hamiltonian

  11. Models for hybrid mesons Guo PRD 78 (2011) 056003 Mass (GeV) 0−+ 0−+ 1−− 1−− 2+− 2+− 2−+ 2−+ 1−+ 1−+ 0+− 0+− Constituent Gluon JgPC=1+− Lattice QCD Similar features as LQCD spectrum

  12. How do exotics decay? Possible daughters: L=1:a,b,h,f,… L=0:,,,,… Flux Tube Model The angular momentum in the flux tube stays in one of the daughter mesons (L=1) and (L=0) meson, e.g: quark L=1 flux tube L=1 Example: p1→b1p wp→ (3p)p or wp→ (pg)p simple decay modes such as ,, … are suppressed.

  13. Partial width dependence on hybrid mass K1(1400)K h(1295)p b1(1235) p rp Page PRD 59, 034016-9

  14. Experimental status of exotic 1−+ p(1600) For review see Meyer PRC 82 (2010) 025208 [Saturday Plenary 4] Only photoproduction search

  15. CLEO-c exotic p1 Events /50MeV Exotic 1-+p1 -> h’pMass =1670±36 MeV, G=240±78 MeV 4 sigma significance Adams PRD 84 (2011) 112009

  16. Other suspected hybrid signals New state Y(4260) 1–-state found by Babar/CLEO Does not fit into the quark model spectrum Properties consistent with hybrid charmonium state. [Friday C2] Zhu Int J Mod Phy E 17 (2008) 283 A second new state Y(2175) is proposed as its light quark analog ssg [Friday C1] Belle PRD 80 (2009) 031101 Y(2175) Y(2175)

  17. Photoproduction Decomposition of total cross section Eg = 9.3 GeV Approximately the 70% of total cross section in the energy region Eg ~ 7-12 GeV has multiple neutrals and is completely unexplored

  18. g and p beams B. Grube DPG March 2012 Phys. Rev. D43, 2787 (1991) a2 19.3 GeV 190 GeV Events/50 MeV COMPASS SLAC M(p+p+p−) (GeV) M(p+p−p−) (GeV) Note: much more photon data from Jlab at lower energy

  19. Photoproduction and linear polarization • Production • The expectation from the flux tube model is that hybrids will be produced at a rate comparable to normal mesons. • This expectation is corroborated by recent lattice calculations that show that the strength of charmonium hybrid radiative decays are similar to normal mesons Dudek PRD 79 (2009) 094504 • Polarization • For a given produced resonance, linear polarization enables one distinguish between naturalities of exchanged particles. • If the production mechanism is known, linear polarization enables one to filter resonances of different naturalities. Filter on naturality

  20. Minimum photon energy for search Eg = 9 GeV Mass = 2.5 GeV Resonant shapes generated with the same widths and production cross sections. Yield and line shape determined by production kinematics.

  21. GlueX strategy for hybrid meson search • Use 8 – 9 GeV polarized photons (12 GeV electron beam) • Expect production of hybrids to be comparable to normal mesons • Dearth of experimental data • Use hermetic detector with large acceptance • Decay modes expected to have multiple particles • hermetic coverage for charged and neutral particles • high data acquisition rate to enable amplitude analysis • Perform amplitude analysis • identify quantum numbers as a function of mass • check consistency of results in different decay modes

  22. Areal view of accelerator

  23. Hall D civil construction complete Summer 2011

  24. Linearly Polarized Photon Beam 4 nominal tagging interval Rates are based on • 12 GeV electron beam • 20 mm diamond crystal • 300 nA electron beam • Rad-collimator: 76 m • Collimator diameter: 3.5mm Leads to 107g/s ontarget Design is expandable to 108g/s Photon Beam Intensity Spectrum tagged photon energy (GeV) dE/E = 0.1% Pol = 40%

  25. Hall D – GlueX detector Pb-glass detector (Fcal) Time- of-flight (tof) Hermetic detection of charged and neutral particles in solenoid magnet Barrel Calorimeter (Bcal) Target (LH2) Initial Flux 107g/s 18,000 FADCs 4,000 pipeline TDCs 20 KHz L1 trigger 300 MB/s to tape Tagger Spectrometer (Upstream) Tracking Cathode strips Drift chambers Straw tubes Superconducting 2 T solenoid

  26. Detector status

  27. Sample amplitude analysis with GlueX generated waves 1−+ exotic wave generated with 1.6% relative strength Corresponds to 3.5 hours GlueX data, full detector simulation and reconstruction

  28. 12 GeV Project Schedule • Hall A commissioning start Jan 2014 • Hall D commissioning start October 2014 • Halls B and C commissioning start April 2015

  29. Summary • QCD on the Lattice • Lattice calculations have made great strides in calculating the spectrum of normal and hybrid mesons. • Hybrid masses are expected in the range of 1.8 to 2.7 GeV • The spectrum is consistent with the constituent gluon model (Jg=1+−) • Model expectations • In photoproduction, gluonic excitations will be produced with roughly the same cross sections as normal mesons. • Gluonic excitations are expected to decay preferentially to multi-particle final states • The GlueX experiment will study the spectrum of mesons with a polarized photon beam up to M ~ 2.8 GeV with sensitivities of a few percent of the total cross section.

More Related