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Crystal Ball at MAMI

Crystal Ball at MAMI. Daniel Watts, Univ. of Edinburgh (UK) For the CB@MAMI Collaboration. CB@MAMI: Main physics objectives. (mainly involving low cross sections and/or precision measurements). Precision spectroscopy of low lying baryon states:

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Crystal Ball at MAMI

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  1. Crystal Ball at MAMI Daniel Watts, Univ. of Edinburgh (UK) For the CB@MAMI Collaboration

  2. CB@MAMI: Main physics objectives (mainly involving low cross sections and/or precision measurements) • Precision spectroscopy of low lying baryon states: • m((1232)) fromp p0g’pandp+g’n • m(S11(1535)) fromph g’p reaction • Threshold meson production: (test of LET/ ChPT): • Strangeness (g N→LK) • p0photoproduction at threshold • Ambiguity free amplitude analysis of meson photoproduction • Requires Double polarization measurements: • gN→Np(p); Nh (r,…) channels • Tests of fundamental symmetries (C,CP,CPT…) • Rare, h/decays • In medium properties of hadrons & nuclear physics: • Meson photo production on nuclei

  3. The MAMI facility One of the MAMI-C magnets g e • 100% duty factor electron microtron • MAMI-C 1.5 GeV upgrade (2006) (MAMI-B 0.85 GeV) • Crystal Ball - A2 hall (tagged photon beam)

  4. Photon Tagger upgrade

  5. Photon beam facilities Legs B C

  6. Crystal Ball history • 1982-1986 • DORIS • (Ecm = 9 -10 GeV) 1996-2002 BNL-AGS (Ecm = 1.2 – 1.53 GeV) 1976 Conceived 1978 -1981 SPEAR (Ecm = 3 - 7 GeV) 2002 MAMI (Ecm = 1.2 -1.9 GeV)

  7. Crystal Ball arrives at Frankfurt

  8. Setup at MAMI Tracker & Particle-ID Good angular and energy resolution, close to 4p acceptance

  9. Tracker & Particle-ID 2mm thick EJ204 scintillator 320mm s(q) ~ 1.5o s(f) ~ 1.3o • Two cylindrical wire chambers • 480 anode wires, 320 strips • Adapted from DAPHNE • New MWPC tracker under construction (2006)

  10. MWPC & Particle-ID in situ

  11. Setup at MAMI Tracker & Particle-ID Good angular and energy resolution, close to 4p acceptance

  12. MAMI Photo Gallery CB with PMTs CB TAPS CB TAPS Panoramic view of MAMI setup g

  13. Targets at MAMI Polarised 3He gas target (~2008) Liquid hydrogen (deuterium) target Frozen spin Target butanol / deuterated butanol (~2007) Liquid 3He target (2006)

  14. CB@MAMI – timetable Nov '02: Crystal Ballmoved to Mainz Nov '03:Crystal Ball installed at photon beam at MAMI Mar '04:TAPS installed Apr '04:MWPC and PID installed May '04: First test run tests with the complete setup Jun'04-Apr '05 : First production runs Eg=0.1-0.8 GeV: unpolarizedH2or D2targets, nuclear targets Apr '05-Jan'06 : MAMI-C upgrade, photon tagger upgrade '06 onwards : Second production runs Eg=0.1-1.5 GeV: unpolarized, polarised, nuclear targets

  15. Selection of preliminary spectra from first round of experiments Eg = 0.1 – 0.8 GeV

  16. Preliminary analyses:p0, h identification h→ 3p0 → 6g s~25 MeV h→ gg s~23 MeV p0 → gg s~11 MeV

  17. Eg=220 MeV 208Pb sinq ~ 1.22 l/D Rm ~ 5.75 fm (Rc ~ 5.50 fm) 33o Preliminary analyses: Ags(g,p0)Ags coherent p0 photoproduction from nuclei • Clear diffraction patterns for 208Pb, 40Ca, 16O, 12C ds/dW ~ A2(q/kg)P32|Fm(q)|2sin2qp • Matter form factor, D properties in the medium Also see coincident low energy Nuclear Decay Photons !! C. Tarbert, D. Watts 12C 16O 40Ca 3.7MeV 4.4 MeV 6.1 MeV

  18. Preliminary analyses: (g, p)p0 Photon Asymmetry S: A. Starostin

  19. Preliminary analyses: p(g,p)p0p0 • High statistics measurement • With gbeam polarisation →S, Scirc F.Zehr Eg dependence of p0p0 yield (not acc. corrected) ~5% of total statistics

  20. Preliminary analyses: p(g,p)p0g to measurem(D+) m(D+) + dominant + small g´ g p0 D coherent addition... p p g´ g p0 g´ g p0 p p D p p MAMI pilot measurement with TAPS only M. Kotulla et al., PRL 89 (2002) 272001

  21. p(g,p)p0g to measurem(D+) mD=5mp mD=3mp mD=1mp mD= 0.79mp mD=3mp • 100 in statistics • measure g beam polarisation observables • Both pp0andnp+ decay of D+

  22. Future plans with MAMI-C Eg = 0.1 – 1.5 GeV

  23. Double-polarisation in pseudo-scalar meson photoproduction Polarisation of g target recoil Observable

  24. Beam-target observable: E g p → p p0 g p → p h g n → n p0 g n → n h Circularly polarised photons + longitudinally polarised protons (or neutrons) Butanol frozen spin target Deuterated butanol frozen spin target g n → n p0 qp=90o g p → p p0 qp=90o Expected data accuracy qp=±10o Eg=±10 MeV 250 hrs E Eg (MeV) Eg (MeV) Previous E measurement for g p → p p0 led to significant revision of helicity amplitudes for D13(1520) [ PRL 88, 232002 (2002)] Neutron targets: different resonance contributions, isospin structure Also get pp channels – mechanisms, contributions to GDH integrand

  25. Beam-target observable: G g p → p p0 g p → n p+ linearly polarised photons + longitudinally polarised protons Expected Data accuracy qp=±10o Eg=±10 MeV 600 hrs Variable well suited to studies of Roper resonance ( P11(1440) )

  26. Beam-Recoil Observables: Cx, OX, T, P Useful scattered event Select events with scattering angles larger than ~10 degrees : arising from nuclear interaction Initial path of proton Polarimeter acceptance : ±20o polar angle (target at centre) Most events suffer only coulomb scattering Hydrogen target cell g beam TAPS Graphite sheet (~7cm thick) Crystal Ball n(q,f) =no(q){1+A(q)[Pycos(f)–Pxsin(f)]

  27. Beam-Recoil Observables- p(g,p0)p 300 hrs Ee=0.85 GeV 500 hrs Ee=1.5 GeV qp(cm)=130o

  28. Summary ~4p detector system Very good neutral (and charged) particle detection capabilities Excellent properties of MAMI beam Availability of polarized targets Recoil nucleon polarimetry possibilities High quality data for meson photoproduction for Eg up to ~1.5 GeV can be expected

  29. J.Brudvik, J. Goetz, B.M.K.Nefkens, S.N.Prakhov, A.Starostin, I. Saurez, University of California, Los Angeles, CA, USA J.Ahrens, H.J.Arends, D.Drechsel, D.Krambrich, M.Rost, S.Scherer, A.Thomas, L.Tiator, D. von Harrach and Th.Walcher Institut fur Kernphysik, University of Mainz, Germany R. Beck, M. Lang, A. Nikolaev, S. Schumann, M. unverzagt, Helmholtz-Institut fur strahlen und Kernphysik, Universitat Bonn, Germany S.Altieri, A.Braghieri, P.Pedroni, A.Panzeri and T.Pinelli INFN Sezione di Pavia and DFNTUniversity of Pavia, Italy J.R.M.Annand, R.Codling, E.Downie, D.Glazier, J. Kellie, K.Livingston, J.McGeorge, I.J.D.MacGregor, R. Owens D.Protopopescu and G.Rosner Department of Physics and Astronomy, University of Glasgow, Glasgow, UK C.Bennhold and W.Briscoe George Washington University, Washington, USA S.Cherepnya, L.Fil'kov, and V.Kashevarow Lebedev Physical Institute, Moscow, Russia V.Bekrenev, S.Kruglov, A.Koulbardis, and N.Kozlenko Petersburg Nuclear Physics Institute, Gatchina, Russia B.Boillat, B.Krusche and F.Zehr, Institut fur Physik University of Basel, Basel, Ch P. Drexler, F. Hjelm, M. Kotulla, K. Makonoyi, R.Novotny, M. Thiel and D. Trnka II. Phys. Institut, University of Giessen, Germany D.Branford, K.Foehl, C.M.Tarbert and D.P.Watts School of Physics, University of Edinburgh, Edinburgh, UK V.Lisin, R.Kondratiev and A.Polonski Institute for Nuclear Research, Moscow, Russia J.W. Price California State University, Dominguez hills, CA, USA D.Hornidge Mount Allison University, Sackville, Canada P. Grabmayr and T. Hehl Physikalisches Institut Universitat Tubingen, Tubingen, Germany D.M. Manley Kent State University, Kent, USA M. Korolija and I. Supek Rudjer Boskovic Institute, Zagreb, Croatia D. Sober Catholic Catholic University, Washington DC M. Vanderhaeghen, College of William and Mary, Williamsburg, USA CB@MAMI

  30. CB@MAMI: Main physics objectives (mainly involving low cross sections and/or precision measurements) • Precision spectroscopy of low lying baryon states: • m((1232)) fromp p0g’pandp+g’n • m(S11(1535)) fromph g’p reaction • Threshold meson production: (test of LET/ ChPT): • Strangeness (g N→LK) • p0photoproduction at threshold • Ambiguity free amplitude analysis of meson photoproduction • Requires Double polarization measurements: • gN→Np(p); Nh (r,…) channels • Tests of fundamental symmetries (C,CP,CPT…) • Rare,h/decays • In medium properties of hadrons: • Meson photo production on nuclei

  31. p(g,p)p0g to measurem(D+) mD= 0.79mp mD=3mp • 100 in statistics • measure g beam polarisation observables • Both pp0andnp+ decay of D+ mD=5mp mD=3mp mD=1mp

  32. 4 complex amplitudes – 16 observables in meson photoproduction Each double polarisation observable gives different combination of amplitudes To fix the 4 amplitudes unambiguously → 8 real quantities Cannot choose from the same set Double-polarisation: theory background Polarisation of gtarget recoil Observable

  33. Predicted sensitivity to poorly established resonances Resonance parameters from quark model (Capstick and Roberts) Cx’ (g + recoil) – theoretical predictions Solid – SAID Dashed – background + **** Dotdash- background + **** +N-3/2(1960) Dutta, Gao and Lee, PRC 65, 044619 (2002)

  34. Previous experimental data – SAID database P T Data for all CM breakup angles Ox’ Cx’ Recent JLAB data not in database

  35. Recent Cx’ measurement at JLab • First determination • p(g,p)p0 in 2002 • Hall A JLab • MAID & SAID • poor description • of new data Polarisation transfer Cx’ Photon energy (MeV)

  36. The proposed experimental setup Useful scattered event Select events with scattering angles larger than ~10 degrees : arising from nuclear interaction Initial path of proton Polarimeter acceptance : ±20o polar angle (target at centre) Most events suffer only coulomb scattering Hydrogen target cell g beam TAPS Graphite sheet Crystal Ball n(q,f) =no(q){1+A(q)[Pycos(f)–Pxsin(f)]

  37. GEANT simulation of polarimeter • Simulation includes realistic • smearing of energy deposits due to experimental energy resolution • and proper cluster finding algorithms • Finite target size and Eg resolution included No Graphite With Graphite scatterer Angle between qN(Eg,qp) and TAPS hit

  38. qp(CM) >~130o Kinematic acceptance of polarimeter p(g,p)N Polarimeter acceptance Pion angle in CM (deg) Eg=150 MeV Eg=200 Eg=300 Eg=500 Eg=750 Eg=1000 Eg=1500 Nucleon angle in lab (deg)

  39. More forward recoils than for pion production. Almost all recoils are incident on polarimeter up to ~0.8 GeV Kinematic acceptance of polarimeter p(g,h)N Polarimeter acceptance CM h angle (degrees) Eg=720 Eg=820 Eg=920 Eg=1520 Lab nucleon angle (degrees)

  40. Cx’ – Extraction and expected accuracy Cx’ 0 180 360 Photon energy (MeV) • Pg=0.7, Eg=±25MeV, qp=130±10 • s ~ 1 mb/sr →DCx ~ 0.015 • s ~ 0.1 mb/sr →DCx ~0.05 • Greatly improved data quality Plot difference in f distributions for two helicity states (cut on region of q with reasonable A(q)) Left with simple sin(f) Dependence. Extract Px

  41. qscat Polarimetry basics • Measure direction of nucleon before and after the scatterer with sufficient accuracy to determine an analysing reaction has taken place. For incident protons also have multiple (coulomb) scattering Qscat=5-20o

  42. CB@MAMI: Future programme • Magnetic dipole moments: • (1232) fromp p0g’pandp+g’n • S11(1535) fromph g’p) reaction • Threshold meson production: (test of LET/ ChPT): • Strangeness (g N→LK) • p0photoproduction at threshold • Double polarization measurements:(properties of baryon resonances/GDH) • gN→Np(p); Nh (r,…) channels • Mass of-meson and raredecays • Meson photo production on nuclei: medium mod., nuclear properties

  43. 4 complex amplitudes →16 observables in meson photoproduction → need 8 well chosen measurements to fix the 4 amplitudes Each double polarisation observable gives a different combination of amplitudes Double-polarisation in pseudo-scalar meson photoproduction Polarisation of g target recoil Observable

  44. MWPC tracker • Adapted from MWPCs used with the DAPHNE detector • New dedicated MWPC tracker under construction • (Complete early 2006) s(q) ~ 1.5o s(f) ~ 1.3o

  45. Scattered nucleon detection in TAPS • 1 TAPS block ~ position resolution for hit • TAPS~0.9m from scatterer N Straight through 10o scatter 20o scatter p

  46. Detrimental side-effects of scatterer material • To hit polarimeter TN>100 MeV in g(p,p)N above the D • Proton energy loss <10 MeV for Tp>100 MeV. • Multiple scattering <1o FWHM for Tp>100 MeV • 0.37 radiation lengths g conversion ~ 30% Tp after graphite Energy loss Tp exit proton (MeV) Tp incident proton (MeV) Coulomb scattering FWHM scattering angle (deg) Proton energy (MeV)

  47. Crystal Ball history • 1982-1986 • DORIS • (Ecm = 9 -10 GeV) • Y spectroscopy • radiative  decays 1996-2002 BNL-AGS (Ecm = 1.2 – 1.53 GeV) N*, D, L*, S, h decays, medium. mod 1976 Conceived 1978 -1981 SPEAR (Ecm = 3 - 7 GeV) y,y spectroscopy radiative f decays t decays D decays, gg→gg, h, h, f 2002 MAMI (Ecm = 1.2 -1.9 GeV)

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