Overview Bremsstrahlung Tagging Spectrometer and Photon Beam Review

1. OverviewBremsstrahlung Tagging Spectrometer and Photon Beam Review Elton S. Smith Jefferson Lab Requirements Summary of beamline and rates Status of project

2. Physics goals and key features Normal mesons: glue is passive Hybrid mesons: glue is excited The physics goal of GlueX is to map the spectrum of hybrid mesons starting with those with the unique signature of exotic JPC . • Identifying JPC requires an amplitude analysis which in turn requires • linearly polarized photons • detector with excellent acceptance and resolution • sensitivity to a wide variety of decay modes which include photon and charged particles This, coupled with a hybrid mass reach up to 2.5 GeV, requires 9 GeV photons produced using coherent bremsstrahlung from 12 GeV electrons.

3. Search for QCD Exotics  ,K,g X n,p p The GlueX Detector Design has been driven by the need to carry out Amplitude analysis. 11’1 b2 h2 h’2 b0 h0 h’0 1−+ 2+− 0+− h1 → a+1p-→(o+)(-) →+-+- all charged h0→ bo1po→(o)gg→+-gggggg many photons Photoproduction h’2→ K+1K−→o K+ K−→+−K+K− strange particles Final state particles ± K± p n KL

4. Mass Predictions Lowest mass expected to be p1(1−+) at 1.9±0.2 GeV Lattice 1-+ 1.9 GeV 2+- 2.1 GeV 0+- 2.3 GeV

5. Line shape distortion M=2.8 GeV M=2.5 GeV MX (GeV)

6. g are sensitive to production mechanism V X J=0– or 0+ Parity conservation implies:

7. Strategy for Exotic Meson Discovery • Use 8 – 9 GeV polarized photons (12 GeV electron beam) • Sensitivity to mesons masses up to 2.5 GeV • 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 partial-wave analysis • identify quantum numbers as a function of mass • check consistency of results in different decay modes

8. Requirements for photon beam • Coherent peak ~ 8.4 ─ 9 GeV • Linear polarization • High rates • Initial running at 107g/s in the coherent peak • Design system with a clear path to 108g/s

9. 6 GeV CEBAF add Hall D (and beam line) 12 Upgrade magnets and power supplies CHL-2 Enhance equipment in existing halls

10. Hall D Complex Accelerator East Arc

11. Photon beam and experimental area Tagger area Hall D North linac Electron Beam dump 75 m Photon Beam dump East arc Solenoid- Based detector Electron beam Collimator Experimental Hall D Coherent Bremsstrahlung photon beam Tagger Area Top View

12. GlueX / Hall D Detector Lead Glass Detector Barrel Calorimeter Solenoid Coherent Bremsstrahlung Photon Beam Time of Flight Note that tagger is 80 m upstream of detector Tracking Cerenkov Counter Target Detector Review Oct 20-22, 2004 Electron Beam from CEBAF

13. GlueX detector

14. Institutional Responsibilities • The GlueX collaboration has designed and optimized the detector to study gluonic excitations. Many university groups have contributed to the R&D and development of major subsystems. • SolenoidJLab • Detectors • TrackingCarnegie Mellon, Ohio U, Florida International U • CalorimetryU of Regina, Florida State, Indiana U, Inst for High Energy Physics (Protvino), U of Athens • PIDIndiana U, Inst for High Energy Physics, U of Tenn, ORNL • ComputingJLab, U of Regina, Indiana U, Carnegie Mellon, U Connecticut, Christopher Newport U • Electronics Indiana U, JLab, U of Alberta, Indiana U Cyclotron • BeamlineCatholic U of America, Glasgow U, U of Connecticut • InfrastructureJLab

15. Interface between accelerator and Hall D • The accelerator will be responsible for the electron beamline, and Hall D will be responsible for the photon beam. This is the nominal breakdown of responsibilities, with additional clarification in the next two paragraphs. • The accelerator will deliver and monitor the 12 GeV electron beam to the radiator immediately upstream of the tagger magnet. The accelerator will also be responsible for steering the beam to the electron beam dump. Some monitoring of the electron beam at the dump may be required to insure accurate delivery. • Hall D will be responsible for purchasing and qualifying the crystal radiators, all aspects of the tagger magnet and hodoscope systems, collimation of the photon beam immediately upstream of the photon hall, and monitoring of the photon beam from the radiator to the photon beam dump behind the GlueX detector.

16. Coherent Bremsstrahlung Incoherent & coherent spectrum 40% polarization in peak collimated tagged 0.1% resolution 12 GeV electrons flux This technique provides requisite energy, flux and polarization photons out electrons in spectrometer diamond crystal Hadronic Backgrounds photon energy (GeV)

17. High sensitivity → high rates Start with 8.4 - 9.0 GeV Tagged 30 cm targetcross section = 120 µb low-rate high-rates: multiply by factor of 10

18. Photon Beam Rates and Backgrounds • Total hadronic rate is dominated by the resonance region • For a given electron beam and collimator, background is almost • independent of coherent peak energy, comes mostly from incoherent part. • 3. The following assumes a 12GeV electron beam energy. peak energy8 GeV 9 GeV 10 GeV 11 GeV N in peak185 M/s 100 M/s 45 M/s 15 M/s peak polarization0.54 0.41 0.27 0.11 (f.w.h.m.)(1140 MeV) (900 MeV) (600 MeV) (240 MeV) peak tagging eff.0.55 0.50 0.45 0.29 (f.w.h.m.)(720 MeV) (600 MeV) (420 MeV) (300 MeV) total hadronic rate385 K/s 365 K/s 350 K/s 345 K/s (in tagged peak) (26 K/s) (14 K/s) (6.3 K/s) (2.1 K/s)

19. Today’s presentations Photon Beam dump 75 m Detector Collimator Electron beam 1. Overview 2. Photon beam 3. Simulation and backgrounds Vacuum chamber Photon beam 4. Tagger magnet design 5. Spectrometer optics Hodoscope: 6. Fixed array and beam monitoring 7. Tagger Microscope Electron beam

20. Architect’s rendering of Hall D complex Hall D Counting House Cryo Plant Service Buildings

21. JLab 12 GeV Upgrade Project Status Highlight in the 20-year plan of the Office of Science (2003) What’s New: “New supercomputing studies indicate that force fields called “flux-tubes” may be responsible [for the mechanism that confines quarks], and that exciting these should lead to the creation of never-before-seen particles.” Review of Science program for the 12-GeV Upgrade (Apr 2005) From the Executive Summary: “After a decade of research, we should know whether the formation of flux tubes by the gluon fields is the mechanism of confinement…” Determination of “Mission Need” CD-0 (Apr 2004) Successful Project Review (Jul 2005), CD-1 expected soon Four-year construction project planned to start in FY08

22. GlueX Reviews December 1999: PAC Requested Review of the GlueX Project D. Cassel (chair), J. Domingo, W. Dunwoodie, D. Hitlin, G. Young. April 2001: NSAC Long Range Plan Committee. July 2003: Electronics Review of the GlueX Project J. Domingo, A. Lankford, G. Young (chair) October 2004: Detector Review M. Albrow, J. Alexander (Chair), W. Dunwoodie, B. Mecking. December 2004: Solenoid Assessment J. Alcorn, B. Kephart (Chair), C. Rode. All of these review committees have both identified areas that were unsettled and made excellent suggestions for improvements

23. Hall D Organizational Chart Proposal for merging GlueX collaboration with 12-GeV Upgrade Project Organization reflects the WBS outline

24. Summary • Mapping the spectrum of hybrid mesons provides essential experimental data on the physics of the strong interactions at low energies in the region of confinement. • This unique experimental program is possible now due to • increases in computational power • new developments in detector readout technology • to high quality electron beam at the 12-GeV CEBAF Upgrade • technology to produce thin diamond crystals • You are asked today to review the conceptual design of the Hall D tagger spectrometer and the design parameters of the photon beam for use in this experimental program.