10 July 2007 Collaboration Meeting 1 Photon physics at JLab: Status and prospects ?? Daniel Sober The Catholic University of America

10 July Collaboration Meeting2 Outline Jefferson Lab and Hall B Jefferson Lab and Hall B Completed CLAS runs Completed CLAS runs Future CLAS runs Future CLAS runs PRIMEX (Hall B Primakoff experiment) PRIMEX (Hall B Primakoff experiment) Hall D and GlueX Hall D and GlueX Photon physics with CLAS12 Photon physics with CLAS12

10 July Collaboration Meeting3 The Thomas Jefferson National Accelerator Facility (JLab) 5-pass recirculating linear accelerator 5-pass recirculating linear accelerator Maximum energy currently ~5.2 GeV (Planned: Maximum energy currently ~5.2 GeV (Planned: ~5.7 GeV by 11/07, ~6.0 GeV by 10/08, ~6.5 GeV by 6/09) 3 experimental halls 3 experimental halls Tagged photon facility in Hall B Tagged photon facility in Hall B

10 July Collaboration Meeting4 Hall B The CLAS detector The CLAS detector Polarized electron and tagged photon beams Polarized electron and tagged photon beams Cryogenic and polarized targets Cryogenic and polarized targets

10 July Collaboration Meeting5 Performance   L = cm -2 s -1    B dl = 2.5 T m    p/p ~ %   ~ 4  acceptance   Best suited for multiparticle final states   Bremsstrahlung Photon Tagger (  E  /E  ~10 -3 ) The CEBAF Large Acceptance Spectrometer (CLAS) in Hall B

10 July Collaboration Meeting6 Hall B Tagged Photon system

10 July Collaboration Meeting7 Recently completed photon run periods Run E 0 PhotonTargetReactions period(GeV) Pol g103.77circ.LD2pentaquark search, [ K ,  ] g114.02circ.LH2pentaquark search, [ K , K  ] PRIMEX5.75 -C, Pb  0 lifetime by Primakoff effect (non-CLAS) 2005 eg35.75circ.LH2exotic cascade search g8b4.05linearLH2  p,  p,  p [  p,  ‘ p,  0 p,  + n ] 2006 TPE test3.29  → e +,e - 2-photon exchange: Simultaneous e+ and e- scattering 2007 g13severallinearLD2  n→K , K , 1.1 to 2.3 GeV [  0 p,  + n]

10 July 2007 Collaboration Meeting 8 Linearly polarized photon beam to measure photon asymmetries and double polarization observables Beamtime from June 26 th – Aug 31 st 2005 Lin. Pol. photons on 40cm LH2 target 5 coherent peak positions from 1.3 -> 2.1 GeV Polarization in excess of 90% achieved 10 billion events g8b status report - June 2007 Overview

10 July Collaboration Meeting9    production (spin density matrix elements) (Idaho State University)  - production (spin density matrix elements) (Idaho State University)  production (Catholic University of America)  production (Single and double pol. observables) (Glasgow University) ,  ’ production (beam asymmetry) (Arizona State University)   n,  0 p production (beam asymmetry) (Arizona State University) g8b status report - June 2007 Analysis in progress

10 July Collaboration Meeting10 g8b status report - June 2007 Preliminary analysis (ASU): p -> p 0

10 July Collaboration Meeting11 g13 status (ended June 30)  (linear) + LD2:  n → K , K ,  6 coherent peak settings: 1.1 – 1.3 GeV (E0 = 3.3, 3.9, 4.2 GeV) 1.3 – 1.5 GeV (E0 = 4.5 GeV) 1.5 – 1.7 GeV (E0 = 4.7 GeV) 1.7 – 1.9 GeV (E0 = 5.1 GeV) 1.9 – 2.1 GeV (E0 = 5.2 GeV) 2.1 – 2.3 GeV (E0 = 5.2 GeV)

10 July Collaboration Meeting12 g13: Yields for  n → K 0  X Top: invariant mass of p  - near m(  ) Bottom: invariant mass of  +  - near m( K 0 ) Left: no cuts Right: cuts on the other particle Plots show a 5 GeV run with the coh. edge at 1.9 GeV

10 July Collaboration Meeting13 g13 analysis:  n →  - p

10 July Collaboration Meeting14 TPE (Two-photon exchange) - Beyond the Born Approximation e + p→e + p / e - p→e - p 1  A  on 5% radiator

10 July Collaboration Meeting15 Necessary Tagger Modifications for TPE

10 July Collaboration Meeting16 The PrimEx Experiment A. Gasparian et al. (NCA&T, Kentucky, UMass, MIT, … Precision measurement of    lifetime using Primakoff effect:  +  V (nuclear target) →  0 ( →  +  one of the few quantities in the confinement region that QCD can calculate precisely Precision measurement of    lifetime using Primakoff effect:  +  V (nuclear target) →  0 ( →  +  one of the few quantities in the confinement region that QCD can calculate precisely Hall B tagger + “HyCal” (dedicated hybrid calorimeter: PbW0 4 inner detector, lead glass outer detector) Hall B tagger + “HyCal” (dedicated hybrid calorimeter: PbW0 4 inner detector, lead glass outer detector) Separate Primakoff from nuclear    production by angular distribution. Separate Primakoff from nuclear    production by angular distribution. Require absolute cross section – check normalization by measurements of Compton scattering and pair production Require absolute cross section – check normalization by measurements of Compton scattering and pair production Preliminary results presented at April 2007 APS meeting Preliminary results presented at April 2007 APS meeting

10 July Collaboration Meeting17 PrimEx Approach   JLab Hall B high resolution high intensity photon tagging facility   New novel high resolution, high acceptance multi-channel calorimeter (HYCAL) Primakoff effect PrimEx improvements:

10 July Collaboration Meeting18 PrimEx Hybrid Calorimeter - HyCal   Optimize performance and cost Hybrid calorimeter:   1152 PbWO 4 novel crystal detectors;   576 Pb-glass Cherenkov detectors

10 July Collaboration Meeting19 Fit to Extract  0  Decay Width   Combined average from three independent analysis groups: Γ(  0  )  7.93 eV  2.10%(stat.) Interference Incoherent Coherent Primakoff

10 July Collaboration Meeting20 PrimEx Preliminary Result  (  0  ) = 7.93eV  2.1%  2.0%   PrimEx Preliminary Result:  (  0  ) = 7.93eV  2.1%(stat)  2.0%(syst) Most recent calculation of hadronic correction in QCD by Ioffe & Oganesian, hep-ph/ gives:   (  0  ) = 7.93eV ± 1.5% (uncertainty from   due to  0 /  mixing)

10 July Collaboration Meeting21 PrimEx Future Plans Publish existing results Publish existing results New 6 GeV run to obtain proposed 1% statistics New 6 GeV run to obtain proposed 1% statistics 12 GeV proposal:  0, ,  ’ 12 GeV proposal:  0, ,  ’  widths and transition form factor

10 July Collaboration Meeting22 Future CLAS photon run periods Run E 0 Photon TargetReactions period(GeV) Pol g9a 1.8– circ., Longit. Missing resonances in (FROST) 4.0 linear Pol. H  N, K , K ,  p,  +  - p 2008 g12>5.7 circ. LH2Exotic mesons and baryons 2009–2011 g9bVarious circ., Longit.&Missing resonances in (FROST) linear Transv.  N, K , K ,  p,  +  - p Pol. H g16Various circ., Polarized  n →   p,  +  - n, linear HD  0 ,  0  ,  +  

10 July Collaboration Meeting23 target: Ø15mm x 50mm butanol C 4 H 9 OH dilution factor 10/74 eff. density: g/cm 3 operate at ~50mK, repolarize at 0.4K CLAS Frozen-Spin Target (FROST)

10 July 2007 Collaboration Meeting 24 CLAS-FROST:  →  0 p,  + n (sample PWA) CLAS-FROST:  →  0 p,  + n (sample PWA) Sample PWA data generated from SAID SM02 (Recoil, Target asy., all 4 Beam-Target asymmetries) red: predicted FROST data greatly reduced uncertainties 1=uncertainty based on world data

10 July Collaboration Meeting25 ● ● 1 st run period in fall 2007 (long.pol.) ● ● Recent tests successful (20 mW at 200 mK, 100  W at 50 mK – June 2007) ● ● All polarization observables measurable in CLAS will be extracted from data ● ● Complete set of measurements for KY ● ● “Almost” complete set for  N,  p ● ● Double/triple pol. obs. for    - p,  p minimally model-dependent extraction of N* parameters & potential for discovery of missing states FROST outlook

10 July Collaboration Meeting26 HD Target (“HD-ICE”) Previous operation at LEGS (BNL) Previous operation at LEGS (BNL) DOE funding approved: A. Sandorfi and group will move to JLab in early 2008 DOE funding approved: A. Sandorfi and group will move to JLab in early 2008 New horizontal cryostat required for CLAS New horizontal cryostat required for CLAS Aim for 2009 installation and run Aim for 2009 installation and run

10 July Collaboration Meeting27 HD target In-Beam-Cryostat for CLAS target: Ø25mm x 50mm 3g of solid H-D composite density: g/cm cooling wires (Al) Ø50  m P V (D)~40%, P(H)~40% or P V (D)~0%, P(H)~80% LEGS data:

10 July Collaboration Meeting28 MM 2 (  +D) MM 2 (  +n)  n(p)   0  (p)  n(p)   0  (p)   +  – p  – (p)   +  – p  – (p)  n(p)   0  0 (p)  n(p)   0  0 (p)   +  – p  – (  p)   +  – p  – (  p) E06-101: + E06-101: + frozen-spin in CLAS clean channel-separation; clean channel-separation; very low backgrounds very low backgrounds  factors of > 20 reduction in beam-time over other targets beam-time over other targets high nucleon polarizations high nucleon polarizations in-beam lifetimes > year in-beam lifetimes > year

10 July Collaboration Meeting29 Summary of Frozen-Spin Experimental Program polarized butanol target (89 days of beam time) E02-112:  p→KY (K + , K +  0, K 0  + ) E02-112:  p→KY (K + , K +  0, K 0  + ) E03-105/E04-102:  p→  0 p,  + n E03-105/E04-102:  p→  0 p,  + n E05-012:  p→  p E05-012:  p→  p E06-013:  p→  +  - p E06-013:  p→  +  - p polarized HD target (85 days) E06-101:  n→π  - p,  n→  +  - n, E06-101:  n→π  - p,  n→  +  - n,  n→KY (K 0 , K 0  0, K +  - )  n→KY (K 0 , K 0  0, K +  - )

10 July Collaboration Meeting30CHL-2 Upgrade magnets and power supplies Enhance equipment in existing halls 6 GeV CEBAF Add new hall

10 July Collaboration Meeting31 Upgrade Beam Properties All polarized ! Number of passes for Hall D Max. energy for Hall D GeV Number of passes for Halls A, B, C Max. energy for Halls A, B, C 5 (4, 3, 2, 1) 11 GeV (8.8, 6.6, 4.4, 2.2) Max. current to Halls A + B + C Max. current to Hall D 85  A 5  A Max. beam power Duty-cycle 1 MW 100%

10 July Collaboration Meeting32 The 12 GeV Upgrade: Complementary Equipment in Halls B & C, and a New Hall D 9 GeV tagged polarized photons and a 4  hermetic detector D Super High Momentum Spectrometer (SHMS) at high luminosity and forward angles C CLAS upgraded to higher (10 35 cm -2 s -1 ) luminosity and coverage B Retain HRS Pair for continuation of research in which resolution comparable to nuclear level spacing is essential. Use Hall to stage “one-of-a-kind” specialized experiments requiring unique apparatus. A

10 July Collaboration Meeting33 Photon physics after the 12 GeV upgrade (2012+) Hall D: The GlueX experiment Hall D: The GlueX experiment Dedicated coherent bremsstrahlung beam. Search for exotic mesons at E  > 9 GeV Hall B: CLAS-12 Hall B: CLAS-12 No planned tagger upgrade in base equipment. New torus magnet and detectors, emphasizing forward acceptance, electron beam experiments (GPDs)

10 July Collaboration Meeting34 Hall D (GlueX): Research Program   Search for Gluonic Excitations   Hybrid (qqg) spectrum expected between 1.5 and 2.5 GeV/c 2   Exotics do not mix with normal qq mesons   ALSO:   ss spectroscopy   Only five states established   Photon has a large virtual (ss) component   Other physics   KK threshold   Radiative decays of excited vector mesons  

10 July Collaboration Meeting35 Photoproduction More likely to find exotic hybrid mesons using beams of photons. Lowest-mass hybrids predicted to be in J PC =1 -+ nonet. Photon linear polarization constrains the production mechanism.

10 July Collaboration Meeting36 Ideal Photon Beam Energy for GlueX Based on: maintain sufficient photon flux/polarization (via coherent bremsstrahlung) maintain sufficient meson yield for high mass (2.5 GeV) region separate baryon from meson resonances Figure-of-merit (P 2 x N  ) for M = 2.5 GeV and E 0 = 12 GeV

10 July Collaboration Meeting37 Photon beam and experimental area Top View 75 m Tagger Area Experimental Hall D Electron beam Coherent Bremsstrahlung photon beam Solenoid- Based detector Collimator Photon Beam dump East arc North linac Tagger area Hall D Electron Beam dump

10 July Collaboration Meeting38 GlueX Detector in Hall D Tagger Spectrometer (Upstream) Hermetic detection of charged and neutral particles

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10 July Collaboration Meeting41 Hall-D tagger two-magnet design with horizontal deflection hodoscope: variable ‘microscope’ & coarse fixed array photon spectrum: coherent and incoherent bremsstrahlung deflected e-beam primary e-beam

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10 July Collaboration Meeting44 CLAS12 – 12 GeV Upgrade of Hall B CLAS12 Hall B with CLAS12 is a major part of the upgrade to 12 GeV PAC30 recommended approval of a broad initial physics program. Many components are in R&D or design phases: Drift chambers, SVT, calorimeter, Cerenkov counter, TOF counters, s.c. magnets. CD-2 review in summer 2007.

10 July Collaboration Meeting45 Future of the Hall B Tagger Maximum E 0 = 6.2 GeV at I = 2400 A Maximum E 0 = 6.2 GeV at I = 2400 A At 12 GeV operation, Hall B will have choice of 2.2, 4.4, 6.6, 8.8, 11 GeV. At 12 GeV operation, Hall B will have choice of 2.2, 4.4, 6.6, 8.8, 11 GeV. Desirable to raise tagger capability to 6.6 GeV: new power supply, add yoke iron? Desirable to raise tagger capability to 6.6 GeV: new power supply, add yoke iron? More speculative: Dump electrons in tagger yoke? (background test July 2007). More speculative: Dump electrons in tagger yoke? (background test July 2007). New end-point tagger under consideration – no detailed design, no funds in initial upgrade. New end-point tagger under consideration – no detailed design, no funds in initial upgrade.

10 July Collaboration Meeting46 Summary Intensive program in N* photoproduction using polarized beams and frozen-spin polarized targets polarized beams and frozen-spin polarized targets (butanol and HD) in Hall B. After the 12 GeV upgrade: After the 12 GeV upgrade: Exotic meson (gluonic excitations) program in Hall D. Future of photon physics in Hall B is uncertain.