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Overview of recent photon beam runs at CLAS

Explore recent experiments, analyses, and advancements in photon runs at CLAS, including tagged photons up to 6GeV, polarization observables like g8 and g13, and upcoming research directions. Learn about tagged bremsstrahlung photons, circular and linear polarization, and the significance of polarization observables in enhancing measurements. Discover key findings such as the first measurement of f0 Photoproduction on the proton and the search for new strangeonia. Stay updated on the latest progress and future directions in photon beam runs at CLAS.

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Overview of recent photon beam runs at CLAS

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  1. Overview of recent photon beam runs at CLAS Ken Livingston, University of Glasgow CLAS12 European Workshop, Feb 25-28 2009, Genoa, Italy • Tagged photons at CLAS • Recent experiments and analysis • Polarization observables • g8, g13, g9 • Summary, future experiments

  2. Tagged photons at CLAS • Tagged bremsstrahlung photons up to 6GeV. • Timing resolution < 1 beam bucket. • Circularly polarized • up to ~80% now standard • Linearly polarized • coherent bremsstrahlung up to >90%.

  3. CLAS photon runs > 100 different analyses !(http://www.jlab.org/Hall-B/secure/hadron/wiki/index.php/Analysis_projects) ~20 publications – many more anticipated. Most recent “First Measurement of f0 Photoproduction on the proton”, M. Battaglieri et al. (The CLAS Collaboration), submitted to PRL November 2008 Recent photon runs CLAS g12 update and search for new strangeonia in g12 - Mukesh Saini , in Hadron Spectroscopy session Experiments to measure polarization observables

  4. Missing resonances • Cross sections not enough to separate broad, overlapping resonances • Angular distributions and polarization observables.

  5. Linear Polarisation  Circular polarisation  → Y +  Nucleon recoil polarimiter x Longitudinally polarized nucleon targets  Transverse polarized nucleon targets ? Hyperons are “self analysing”  Polarization observables • + N→ N + m

  6. Polarization observables in pseudoscalar meson production 4 Complex amplitudes - 16 real polarization observables. A complete measurement from 8 carefully chosen observables. Observable g target recoil I. S. Barker, A. Donnachie, J. K. Storrow, Nucl. Phys. B95 347 (1975).

  7. Polarization observables - a simple example, S • Systematics of detector acceptance cancel out. • Only need to know Plin, the degree of linear polarization.

  8. g8b: July 2005 Polarized photon energy range: 1.3 – 2.1 GeV Events (single charged particle in CLAS): 10 billion preliminary results:p0p, p+n.Mike Dugger, ASU CLAS data SAID High statistics. Good agreement with previous measurement. Data set extends to photon energy up to 2.1GeV

  9. g8b preliminary results:hp, h’pMike Dugger, ASU SAID MAID Nakayama and Haberzettl effective lagrangian model High stats for h. Good agreement with previous measurements. Data set extends to photon energy up to 2.1GeV First measurement of S for h’ 2 Eg bins one for coh peak at 1.9 and 2.1GeV

  10. g8b preliminary results - K+L and K+S0Craig Paterson, Glasgow gp-> K+L -> K+pp-gp-> K+S0 -> K+Lg -> K+pp-g Single polarization observablesS Photon asymmetryP Recoil polarization (induced pol. along y)T Target asymmetryDouble polarization observablesOx Polarization transfer along xOz Polarization transfer along z LS0 figure by R.Schumacher, CMU

  11. g8b preliminary results - K+L • Results compared with previous results from GRAAL • 7, 50MeV Energy bins • 1175 -> 1475MeV • Good agreement with previous results PRELIMINARY

  12. g8b preliminary results - K+L • Results compared with previous results from LEPS • 6, 100MeV Energy bins • 1550 -> 2050MeV • More bins for our data Increase the angular coverage to backward angles PRELIMINARY

  13. g8b preliminary results - K+L Ox/Ozextracted from fit to 2d asymmetry T Target asymmetry from 2d asymmetry (not shown) P Recoil pol. from acceptance corrected proton dist. P Recoil pol. g8b GRAAL CLAS J.W.C. McNabb, et al. (CLAS) Phys. Rev. C 69, 042201(R) (2004).

  14. g8b preliminary results - K+L Double polarization ovservable Ox Results compared with Regge-Plus-Resonance model from Gent group • - Large Polarizations! • Some evidence for an important role for missing D13(1900) state • Poor agreement at low energy PRELIMINARY

  15. g8b preliminary results - K+L Full lamba polarization ? With circularly polarized photons – “fully polarized lambda” R. Bradford et al. (The CLAS Collaboration), Phys. Rev. C 75, 035205 (2007). - Full polarization at forward angles - Not repeated over full kinematic range - More relations can be tested PRELIMINARY (P2 + Ox2+Oz2)1/2

  16. g13 meson photoproduction, polarized photons on LD2 gn (p)-> p+p (p) Daria Sokhan, Edinburgh • g13a circularly polarized photons • ~2GeV, ~2.6GeV electron beam • ~2 months beamtime • g13b linearly polarized photons • 1.3, 1.5, 1.7, 1.9, 2.1, 2.3 GeV coh peak • ~ 2months beamtime • Single charge particle trigger • ~7kHz event rate PRELIMINARY MAID SAID Previous data

  17. g13 meson photoproduction, polarized photons on LD2 gn (p)-> K0sL0(p) Neil Hassall, Glasgow gp (n)-> K+L0 (n) Russell Johnstone, Glasgow See talk in Hadron Spectroscopy session PRELIMINARY 1st results photon asymmetry S Cosqcm (-0.8 - +0.8) Each plot is 50MeV photon energy bin 1050-2450MeV

  18. g9 FROST – FROzen Spin Target Meson photoproduction with linearly and circularly polarized photons on polarized target E02-112: γp→KY (K+Λ, K+Σ0, K0Σ+)‏ E03-105/E04-102: γp→π0p, π+n E05-012: γp→ηp E06-013: γp→π+π-p g9a running conditions November 3, 2007– February 12, 2008 Longitudianally polarized target Circularly and linearly polarized photon beam 0.5-2.4 GeV Trigger: at least one charged particle in CLAS Target Pol > 80%, Relaxation time > 1600hrs – better that design goals

  19. g9aFROST sample analysis of gpp+nEugene Pasyuk, ASU Helicity asymmetry E • Select p+ applying cut on b vs. p • Vertex cuts • Select missing neutron Raw asymmetry butanol 12C CH2 butanol 12C CH2 Preliminary Based on ~2% of statistics

  20. g8b data. g + p → p+ n with (n,p) scatter (detect p+p) q Mx(gp→p++X) Angle between Pncalc and Ppmeasured K.Livingston Recoil polarimetry possibilities ? n(q,f) =no(q){1+A(q)[Pycos(f)–Pxsin(f)] - How to do this for 4p detector x and y (transverse) components of nucleon polarisation Nucleon polarimeter for CB@MAMI, D. Watts, Edinburgh Graphite p q n g p+ Start counter

  21. Summary, future experiments • g8b (lin. pol. on LH2) cooking complete, analysis well developed • Photon asymmetries for p0p,p+n, h, h’ KL, KS: prelim. results. • P, T Ox, Oz for KL, KS: • Also f analysis well developed (J. Salamanca, ISU). • 2 p channel talk by C. Hanretty in Hadron spectrosopy session. • g13 (lin., circ. pol on LD2) cooking in progress, analysis beginning • Some very preliminary results for photon asymmetry. • g9 (lin, circ pol on L/T pol butanol) cooking about to begin • Circularly polarized photon beam on longitudinally polarized target • E P, Lx/Lz, Cx/Cz • Linearly polarized photon beam on longitudinally polarized target • , G, P, (Tx/Tz) Ox/Oz • Circularly polarized photon beam on transversely polarized target • T, F, P, Tx/Tz, Cx/Cz • Linearly polarized photon beam on transversely polarized target • , H, T, P, (Lx/Lz)‏ • Upon completion of g9b for the first time we will have complete set of observables in Kaon photoproduction and nearly complete for all other mesons, which will allow model independent extraction of the amplitude for subsequent extraction of baryon resonances and their properties. (E. Pasyuk). • eg6 4He target, Bonus detector coherent meson production. (S.Stepanyan talk on Friday) scheduled 2009 • HDice (A.Sandorfi, F.Klein) Polarized HD target –further extesion of polarization observables scheduled 2010 • CLAS12 • Tagger will only tag up to 6GeV primary beam • Development of Quasi real photon beam (Q2~0) S.Stepanya, R.DeVita, M. Battaglieri • Post target tagger – linearly polarized • High rates scheduled 2010

  22. CLAS coherent bremsstrahlung facility • Tagging spectrometer with high rate, good energy and timing resolution • High precision goniometer (GWU) • High quality, thin diamond (Glasgow) • Tight photon beam collimation (ISU) • Polarimetry Photon energy P > 90% Peak > 90% pol. “A device called a goniometer tilts the diamond, much like a lady turning her hand to admire the sparkle of a new ring.” - JLAB On Target Magazine

  23. Measurements with photon beam profile detectorD. Glazier, Glasgow 1st Measurement of 2D photon enhancement for coherent bremsstrahlung (MAMI,Mainz) paper in preparation below peak coherent peak above peak Coherent peak at 300Mev, MAMI electron beam energy 855MeV • Good agreement with coherent bremstrahlung calculations • Improvements in incoherent component, collimation + multiple scattering. • No evidence of high energy photons from quasi channeling. • Investigation of 2D strip detector for polarimetry

  24. g8b preliminary results - K+L • K+LPhoton Asymmetry, S, extracted from cos(2f) fit to azimuthal kaon distribution • Fits shown for 1 energy bin • 340 (20E, 17q) kinematic bins • Almost full angular coverage

  25. g8b preliminary results - K+S0 • Results compared with previous results from GRAAL • 7, 50MeV Energy bins • 1175 -> 1475MeV • Good agreement with previous results PRELIMINARY

  26. g8b preliminary results - K+S0 • Results compared with previous results from LEPS • 6, 100MeV Energy bins • 1550 -> 2050MeV • More bins for our data!!! Increase the angular coverage to backward angles PRELIMINARY

  27. Peak > 90% pol. PRELIMINARY K.Livingston, Glasgow J.Santoro, CUA Polarimetry: from pair (e+,e-) productionH.Schmieden, Bonn • Well described by QED, but experimentally difficult – small opening angle e+ e- • Pair production simulations by Kharkov group • Polarimeter built and tested at Sping8, recently tested at Jlab • Polarimeter to be based on Jlab design • Microstrip detectors, or pixel detectors (Atlas group) • Bonn student completed 10 months exchange in Glasgow now to be full time in Bonn.

  28. Polarimetry: from hadronic reactionR. Beck, Mainz -> Bonn Use reaction with a known photon asymmetry • Can be high statistics • Very good relative monitor of polarization • Combined beam, target polarization. • Non-indpendent – depends on specific expt • Need very good systematics or calibration • Awaiting MAMI polarized target and polarised photon beam in 2nd half of 2007 • Recent preliminary results from JLab (g8b)‏ • Proton target • Back to back charge particles in Start Counter • Atomic or hardonic ? • Asymmetry from ~20mins DAQ data • Constant with E from 1.3GeV – 1.9GeV

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