1. Elton S. Smith MESON2012 May 31 – June 5, 2012 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. Elton S. Smith MESON2012 May 31 – June 5, 2012 2 Quarks are confined inside colorless hadrons q q q Quarks combine to “neutralize” color force q q q q q q q mesonsbaryons Allowed by QCD, but do they exist in nature? glueball mesonhybrid meson q q pentaquark q q q q molecules q q q q q

3. Elton S. Smith MESON2012 May 31 – June 5, 2012 3 Normal Mesons – qq color singlet bound states 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. J PC = 0 – – 0 + – 1 – + 2 + – … Not-allowed: exotic J PC = 0 – + 0 ++ 1 – – 1 + – 2 ++ … Allowed combinations K+K+ −− K−K− ++ 00 ’’  K0K0 K0K0 K*    Spin 0 Spin 1 S = S 1 + S 2 J = L + S P = - (-1) L C = (-1) L+S S1S1 S2S2 L

4. Elton S. Smith MESON2012 May 31 – June 5, 2012 Families of Exotics 4  1 I G (J PC )=1 - (1 -+ )  ’ 1 I G (J PC )=0 + (1 -+ )  1 I G (J PC )=0 + (1 -+ ) K 1 I G (J PC )= ½ (1 - ) NN  e X  , ,   1    1   b 1,   ’ 1   Couple to vector meson + exchanged particle 1 -+ nonet

5. Elton S. Smith MESON2012 May 31 – June 5, 2012 Meson Spectroscopy from LQCD 5 Dudek PRD 83 (2011) 111502 Dudek PRD 84 (2011) 074023 Isovector mesons, m  ~700 MeV normal mesons exotics Friday Plenary 3

6. Elton S. Smith MESON2012 May 31 – June 5, 2012 Meson Spectroscopy from LQCD 6 Dudek PRD 83 (2011) 111502 Dudek PRD 84 (2011) 074023 Isovector mesons, m  ~700 MeV normal mesons exotics Friday Plenary 3

7. Elton S. Smith MESON2012 May 31 – June 5, 2012 Meson Spectroscopy from LQCD 7 Dudek PRD 83 (2011) 111502 Dudek PRD 84 (2011) 074023 Isovector mesons, m  ~700 MeV normal mesons exotics Friday Plenary 3

8. Elton S. Smith MESON2012 May 31 – June 5, 2012 Extrapolation to physical mass 8 At m  =400 MeV, mass (1 −+ ) ~ 1.9 GeV, mass (0 + − ) ~ 2.5 GeV

9. Elton S. Smith MESON2012 May 31 – June 5, 2012 Models for hybrid mesons 9 0 −+ 1 −− 2 −+ 1 −+ 0 +− 2 +− Lattice QCD Mass (GeV) 0 −+ 1 −− 2 −+ 1 −+ 0 +− 2 +− Flux Tube J g PC =1 + − and 1 -+ 1 +− 1 ++ Isgur Phys Rev Lett 54 (1985) 869

10. Elton S. Smith MESON2012 May 31 – June 5, 2012 Models for hybrid mesons 10 0 −+ 1 −− 2 −+ 1 −+ 0 +− 2 +− Lattice QCD Mass (GeV) 0 ++ 1 ++ 1 −+ 0 −− 1 +− 2 ++ 3 −+ Effective QCD Hamiltonian Cotanch NP A689 (2001) 481

11. Elton S. Smith MESON2012 May 31 – June 5, 2012 Models for hybrid mesons 11 0 −+ 1 −− 2 −+ 1 −+ 0 +− 2 +− 0 −+ 1 −− 2 −+ 1 −+ 0 +− 2 +− Lattice QCD Constituent Gluon J g PC =1 + − Mass (GeV) Similar features as LQCD spectrum Guo PRD 78 (2011) 056003

12. Elton S. Smith MESON2012 May 31 – June 5, 2012 12 How do exotics decay? Possible daughters: L=1: a,b,h,f,… L=0: , , , ,… simple decay modes such as , , … are suppressed. The angular momentum in the flux tube stays in one of the daughter mesons (L=1) and (L=0) meson, e.g: Example:  1 →b 1  flux tube L=1 quark L=1  → (3  )  or  → (  )  Flux Tube Model

13. Elton S. Smith MESON2012 May 31 – June 5, 2012 Partial width dependence on hybrid mass 13 Page PRD 59, 034016-9 K 1 (1400)K  (1295)  b 1 (1235)  

14. Elton S. Smith MESON2012 May 31 – June 5, 2012 Experimental status of exotic 1 −+  (1600) 14 Only photoproduction search For review see Meyer PRC 82 (2010) 025208 [Saturday Plenary 4]

15. Elton S. Smith MESON2012 May 31 – June 5, 2012 CLEO-c exotic  1 15 Events /50MeV Adams PRD 84 (2011) 112009 Exotic 1 -+  1 ->  ’  Mass =1670±36 MeV,  =240±78 MeV 4 sigma significance

16. Elton S. Smith MESON2012 May 31 – June 5, 2012 Other suspected hybrid signals 16 A second new state Y(2175) is proposed as its light quark analog ssg [Friday C1] Belle PRD 80 (2009) 031101 Y(2175) 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

17. Elton S. Smith MESON2012 May 31 – June 5, 2012 Photoproduction 17 Decomposition of total cross section E  = 9.3 GeV Approximately the 70% of total cross section in the energy region E  ~ 7-12 GeV has multiple neutrals and is completely unexplored

18. Elton S. Smith MESON2012 May 31 – June 5, 2012 18  and  beams SLAC a2a2 Phys. Rev. D43, 2787 (1991) B. Grube DPG March 2012 Events/50 MeV M(  +  +  − ) (GeV) M(  +  −  − ) (GeV) 190 GeV COMPASS Note: much more photon data from Jlab at lower energy 19.3 GeV

19. Elton S. Smith MESON2012 May 31 – June 5, 2012 Photoproduction and linear polarization 19  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  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. Dudek PRD 79 (2009) 094504 Filter on naturality

20. Elton S. Smith MESON2012 May 31 – June 5, 2012 20 Minimum photon energy for search Resonant shapes generated with the same widths and production cross sections. Yield and line shape determined by production kinematics. Mass = 2.5 GeV E  = 9 GeV

21. Elton S. Smith MESON2012 May 31 – June 5, 2012 GlueX strategy for hybrid meson search 21  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. Elton S. Smith MESON2012 May 31 – June 5, 2012 Areal view of accelerator 22

23. Elton S. Smith MESON2012 May 31 – June 5, 2012 Hall D civil construction complete 23 Summer 2011

24. Elton S. Smith MESON2012 May 31 – June 5, 2012 4 nominaltagginginterval Photon Beam Intensity Spectrum photon energy (GeV) tagged  E/E = 0.1% Pol = 40% Linearly Polarized Photon Beam Rates are based on  12 GeV electron beam  20  m diamond crystal  300 nA electron beam  Rad-collimator: 76 m  Collimator diameter: 3.5mm Page 24 Leads to 10 7  /s on target Design is expandable to 10 8  /s

25. Elton S. Smith MESON2012 May 31 – June 5, 2012 Tagger Spectrometer (Upstream) Hermetic detection of charged and neutral particles in solenoid magnet Hall D – GlueX detector Time- of-flight (tof) Pb-glass detector (Fcal) Tracking Cathode strips Drift chambers Straw tubes Superconducting 2 T solenoid Initial Flux 10 7  /s 18,000 FADCs 4,000 pipeline TDCs 20 KHz L1 trigger 300 MB/s to tape Target (LH 2 ) Barrel Calorimeter (Bcal)

26. Elton S. Smith MESON2012 May 31 – June 5, 2012 Detector status 26

27. Elton S. Smith MESON2012 May 31 – June 5, 2012 Sample amplitude analysis with GlueX 27 1 − + exotic wave generated with 1.6% relative strength Corresponds to 3.5 hours GlueX data, full detector simulation and reconstruction generated waves

28. Elton S. Smith MESON2012 May 31 – June 5, 2012 12 GeV Project Schedule 28 Hall A commissioning start Jan 2014 Hall D commissioning start October 2014 Halls B and C commissioning start April 2015

29. Elton S. Smith MESON2012 May 31 – June 5, 2012 Summary 29  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 (J g =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.

30. Elton S. Smith MESON2012 May 31 – June 5, 2012 30 Backup Slides

31. Elton S. Smith MESON2012 May 31 – June 5, 2012 Meson Spectroscopy from LQCD 31 Dudek PRD 83 (2011) 111502 Dudek PRD 84 (2011) 074023 m  ~400 MeV exotics normal mesons

32. Elton S. Smith MESON2012 May 31 – June 5, 2012 32 Can we learn anything qualitative about QCD?  Determination of the spectrum of hybrids will provide insight into ─ The nature of strongly interacting gluon fields ─ The gluon configuration for light quark masses Data Models/Theory Lattice

33. Elton S. Smith MESON2012 May 31 – June 5, 2012 Naming Scheme for u,d Mesons 33 Name (I=1, I=0)LSJ PC2S+1 L J Examples  000- +0- +1S01S0  011 1  3S03S0  b, h101 1  1P11P1 b 1 (1235), h 1 (1170) a, f110 0  3P03P0 a 0 (980), f 0 (980) a, f111 1  3P13P1 a 1 (1260), f 1 (1285) a, f112 2  3P23P2 a 2 (1320), f 2 (1270)  202 2  1D21D2     211 - -3D13D1       212 2  3D23D2 213 3  3D33D3    b, h303 3  1F31F3 a, f312 2  3F23F2 313 3  3F33F3 314 4  3F43F4 P = (-1) L+1 C = (-1) L+S PC= (-1) S+1 G = C(-1) I

34. Elton S. Smith MESON2012 May 31 – June 5, 2012 Experimental evidence for 1  + exotic hybrids 34 Hybrid unlikely Dynamical origin? May be hybrid Challenge in 3  to separate exotic    from   Cleaner  ’  signal Needs confirmation

35. Elton S. Smith MESON2012 May 31 – June 5, 2012 Flux Tube Expectations for  1 (2000) 35 Decay Mode Final state Partial Width PSS (MeV) Partial Width IKP (MeV) b   4358    K  3375  (1295)  2721  16  12 f 1 (1285)  1038 a 1 (1260)  713    K  K 719 Total> 155> 252 Page PRD 59 (1999) Section IV.A.4, 034016-9

36. Elton S. Smith MESON2012 May 31 – June 5, 2012 Selection rules for decays  Decays of J PC =0 , 1 , 2 ,…. exotic hybrids to pseudoscalar mesons vanish.  Hybrids do not decay to .  Hybrids decays to , , KK are forbidden.  Decays of hybrids to s-wave mesons highly suppressed.  Hybrid decay to  is suppressed. 36 Page Phys Lett B402 (1997) 183 Strong interaction selection rules in the limit of non– relativistically moving quarks when the daughter states are identical except for isospin and spin.

37. Elton S. Smith MESON2012 May 31 – June 5, 2012 CLEO-c analysis of exotic 37

38. Elton S. Smith MESON2012 May 31 – June 5, 2012 Experimental evidence for 1  + exotic hybrids 38 Listed among “further states” Needs confirmation Unlikely Hybrid Dynamical origin? May be hybrid Challenge in 3  to separate exotic    from   Cleaner  ’  signal

39. Elton S. Smith MESON2012 May 31 – June 5, 2012 39 6 GeV CEBAFCHL-2 Upgrade magnets and power supplies 12 Enhance equipment in existing halls add Hall D (and beam line)

40. Elton S. Smith MESON2012 May 31 – June 5, 2012 Top View 75 m Tagger Area Experimental Hall D Electron beam Coherent Bremsstrahlung photon beam Solenoid- Based detector Collimator Photon Beam dump Counting HouseRadiator Photon beam and experimental area East arc North linac Tagger area Hall D Electron Beam dump Page 40

41. Elton S. Smith MESON2012 May 31 – June 5, 2012 Particle kinematics 41

42. Elton S. Smith MESON2012 May 31 – June 5, 2012 What to conclude from existing evidence? 42

43. Elton S. Smith MESON2012 May 31 – June 5, 2012 43 Amplitude analysis 3  system in isobar model  (beam) n (recoil) p (target) Hybrid J PC M   = + natural  = − unnatural parity exchange aa  (bachelor) bb R  spin S L 1 2 The decay of the 3  system at point 1 to the di-pion resonance R  and a bachelor pion is described in the Gottfried-Jackson frame. The decay of R  →  a  b at point 2 is described in the helicity frame.