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V.L . Kashevarov . Crystal Ball@MAMI Collaboration Meeting, Edinburg ,13-15 Sept. 2009

Photoproduction of p o h on protons. Identification of g p → p o h p reaction Total cross section Differential cross sections Data fitting Beam helicity asymmetry Spin observables In collaboration with A. Fix and M. Ostrick.

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V.L . Kashevarov . Crystal Ball@MAMI Collaboration Meeting, Edinburg ,13-15 Sept. 2009

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  1. Photoproduction of poh on protons • Identification of g p →po h p reaction • Total cross section • Differential cross sections • Data fitting • Beam helicity asymmetry • Spin observables • In collaboration with A. Fix and M. Ostrick V.L. Kashevarov. Crystal Ball@MAMI Collaboration Meeting, Edinburg ,13-15 Sept. 2009

  2. g p → po h p Reaction identification - 4 or 5 clusters (4 of them are neutrals) - invariant mass for all possible gg combinations (4 photons give 3 independent combinations) - c2 minimization and cut - background subtraction using missing mass distributions for each energy or angular bin V.L. Kashevarov. Crystal Ball@MAMI Collaboration Meeting, Edinburg, 13-15 September 2009

  3. g p → po h p Reaction identification The best combination of gg pairs after c2 minimization and rejection of popoevents. Two entries for each event corresponding to the two photon pair. V.L. Kashevarov. Crystal Ball@MAMI Collaboration Meeting, Edinburg, 13-15 September 2009

  4. g p → po h p Reaction identification Missing mass distributions after subtraction of random coincidences and empty target contribution and aplying c2 cut E g < 1 GeV E g > 1.2 GeV (a) Data (blue) and the best fit by a gaussian + polynominal function (red line) (b) The fit components: gaussian (black) and polynomial (red dashed) (c) Data after background subtrction (blue) and GEANT simulation (red line) V.L. Kashevarov. Crystal Ball@MAMI Collaboration Meeting, Edinburg, 13-15 September 2009

  5. g p → po h p Total cross section Data from July 2007 run LNS and GRALL  stat +syst CB-ELSA  stat (syst ~15%) CB@MAMI  stat (syst ~5%) Blue curve shows the energy dependence of the reaction phase space with arbitrary normalization V.L. Kashevarov. Crystal Ball@MAMI Collaboration Meeting, Edinburg, 13-15 September 2009

  6. g p → po h p Differential cross sections Data from June and July 2007 runs a(W) = (A 3/2 / A 1/2 ) 2 r = G (p S 11 ) / G (h D) a = 0.7 (1.0 – 1.1 GeV) a = 1.2 (1.1 – 1.2 GeV) a = 1.7 (1.2 – 1.3 GeV) a = 2.0 (1.3 – 1.4 GeV) r = 2/3 V.L. Kashevarov. Crystal Ball@MAMI Collaboration Meeting, Edinburg, 13-15 September 2009

  7. g p → po h p Differential cross sections Solid black curve: r = 2/3, a =2.0 Dashed red curve: r = 1/6, a = 2.0 Dotted blue curve: r = 2/3, a =0.7 High sensitivity of the distributions WK(Qp) and WH(fp) to a and WK(fp) and WH(Qp) to r V.L. Kashevarov. Crystal Ball@MAMI Collaboration Meeting, Edinburg, 13-15 September 2009

  8. g p → po h p Differential cross sections Black circles: CB@MAMI 1.72<W<1.87 GeV Red circles: CB-ELSA 1.7<W<1.9 GeV V.L. Kashevarov. Crystal Ball@MAMI Collaboration Meeting, Edinburg, 13-15 September 2009

  9. g p → po h p Data fitting the best fits: green line: D33(1700) blue line: D33(1700) with d-wave red line: D33(1700) with d-wave + P33(1600) + P31(1750) + F35(1905) V.L. Kashevarov. Crystal Ball@MAMI Collaboration Meeting, Edinburg, 13-15 September 2009

  10. g p → po h p Data fitting blue line: the best fit with D33(1700), P33(1600), P31(1750), F35(1905), and Born terms Partial contributions: Red line: D33(1700) Green line: P33(1600) Black line: P31(1750) Dashed red line: F35(1905) Dashed blue line: Born terms V.L. Kashevarov. Crystal Ball@MAMI Collaboration Meeting, Edinburg, 13-15 September 2009

  11. g p → po h p Data fitting The quality of the phenomenological analysis can be greatly improved by accumulating additional data. For example, polarization observables on protons and neutrons. The simplest of them: Beam helicity asymmetry  only circularly polarized photon beam Such a data was taken already! V.L. Kashevarov. Crystal Ball@MAMI Collaboration Meeting, Edinburg, 13-15 September 2009

  12. g p → po h p Beam helicity asymmetry D. Krambrich, F. Zehret al., Phys. Rev. Lett. 103, 052002 (2009)  pp Sc=in experimental data analysis: Usually is analized as fpdependence in the helicity system and may be expanded over function sinnfp(n is integer) n is determined by the orbital momenta of the contributing resonances Pure D33(1700) provides only sinfp term P31(1750), P33(1600), F35(1905) appear in the sin 2fpterm due to interference with D33(1700) sin 3fpterm coming from the interference between s and d waves in the D33 h D decay s+-s- 1 Y+-Y- s++s- P Y++Y- V.L. Kashevarov. Crystal Ball@MAMI Collaboration Meeting, Edinburg, 13-15 September 2009

  13. g p → po h p Beam helicity asymmetry Data from July 2007 and April 2009 runs Fit function : F = P1 sin f + P2 sin 2f V.L. Kashevarov. Crystal Ball@MAMI Collaboration Meeting, Edinburg, 13-15 September 2009

  14. g p → po h p Beam helicity asymmetry Data from July 2007 and April 2009 runs Fit function : F = P1 sin f + P2 sin 2f + P3 sin 3f V.L. Kashevarov. Crystal Ball@MAMI Collaboration Meeting, Edinburg, 13-15 September 2009

  15. g p → po h p Spin observables Our future plans are connected with the proposal A2-09/09: “Spin observables for ph photoproduction in D33(1700) region” We will measure the transverse spin observables T and F We need: - circulary polarized photon beam (only for F); - transversely polarized proton target  frozen-spin butanol (C4H9OH) target Disadvantage: additional background from reactions on 12C and 16O Estimation of this background: - analysis of data taken with a carbon target using the same procedure as for runs with LH2 target; -normalization of the photon flux to LH2 target run; - taking into account the number of 12C nuclei in a carbon target with respect to butanol (16O = 4/3 12C) V.L. Kashevarov. Crystal Ball@MAMI Collaboration Meeting, Edinburg, 13-15 September 2009

  16. g p → po h p Spin observables Expected missing mass spectra for butanol target Eg= 1.0 – 1.1 GeV Eg= 1.1 – 1.2 GeV red line: background contribution from 12C and 16O (data from June 2008 run, 12C target) blue line: investigated reraction(data from July 2007 run, LH2 target) Proposal A2-09/09 was supported by the PAC with the highest priority (A) V.L. Kashevarov. Crystal Ball@MAMI Collaboration Meeting, Edinburg, 13-15 September 2009

  17. This article was accepted on 28.08.09 for publication in EPJA

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