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16 March 2009 EuNPC, Bochum 0 Kaon Photoproduction Results from CLAS D. G. Ireland
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1 “Missing” Baryon Resonances
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2 Resonance Hunting… Mostly done with N scattering or photoproduction Missing resonances may decay through other channels Total Cross-sections + differential cross-sections + Partial Wave Analysis +... 0.5 1.0 1.5 Cross section E (GeV ) P 33 N(1440)P 11 N(1520)D 13 N(1535)S 11 (1600)P 33
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3 Meson Photoproduction Cross Sections
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4 Evidence for new resonance? With D 13 Without D 13 Mart & Benhold, Phys. Rev. C 61 012201(R) (1999)
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5 Transversity Amplitudes b 1 = 1 / 2 [(S 1 + S 2 ) + i(N - D)] } } } } b 2 = 1 / 2 [(S 1 + S 2 ) - i(N - D)] b 3 = 1 / 2 [(S 1 - S 2 ) - i(N + D)] b 4 = 1 / 2 [(S 1 - S 2 ) + i(N + D)] N, S 1,S 2, D: Helicity Amplitudes
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6 Experimental Observables
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7 p →K Reaction Kinematics proton K+K+ Cross Section without target polarisation Hyperon is self-analysing
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8 CEBAF at Jefferson Laboratory
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9 CLAS
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10 Tagged Photons at CLAS E = E 0 – E’ Circular Polarisation: polarised electron beam, amorphous radiator Linear polarisation: Crystal (diamond) radiator
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11 p →K Cross Section Measurements R. Bradford et al., Phys. Rev. C 73, 035202 (2006).
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12 Recoil Polarisation proton K+K+ Hyperon is self-analysing
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13 Recoil Polarisation (P) p→K Guidal, Laget, Vanderhaeghen GENT Kaon-MAID J. McNabb et al. (CLAS) Phys. Rev. C 69, 042201 (2004).
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14 Beam-Recoil Double Polarisation (C x’,C z’ ) proton K+K+ Hyperon is self-analysing
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15 Polarisation → fully polarised R. Bradford et al., Phys. Rev. C 75, 035205 (2007).
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16 Photon Beam Asymmetry ( ) proton K+K+
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17 Linear Polarisation analysis Photon Linear Polarisation Particle ID Thesis work of Craig Paterson (Glasgow)
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18 p →K Photon Beam Asymmetry
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19 p →K Photon Beam Asymmetry PRELIMINARY
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20 p →K Photon Beam Asymmetry PRELIMINARY
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21 Beam-Recoil Double Polarisation ( x,O z ) proton K+K+
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22 p →K Extracting O x and O z
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23 p →K Beam-Recoil O x and O z O x PRELIMINARY O z PRELIMINARY
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24 Experimental Observables
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25 Outlook – Deuterium Target Data taking completed Currently being analysed Data on quasifree neutron and proton Circular and Linear Polarisation
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26 Outlook – FROzen Spin Target (FROST) Target can be longitudinally or transversely polarised “Complete” measurement possible First part of run complete Undergoing calibration Second period to run soon…
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27 Conclusions Kaon Photoproduction results from CLAS: Published results: , P, C x, C z Preliminary results: , T, O x, O z In the near future: Same set of results for 2 H target (quasifree neutron and proton) “Complete” results (FROST) Next few years: Complete set on 2 H and p (HDIce)
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28 Backup Slides…
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29 Resonances in Quark Models
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30 Kaon Photoproduction
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31 Contributing Processes + channel coupling…
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32 Helicity Amplitudes N No overall helicity flip = | – p | } S 1 Single helicity flip } S 2 Single helicity flip } D Double helicity flip }
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33 Cross Section Measurements R. Bradford et al., Phys. Rev. C 73, 035202 (2006).
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34 Cross Section Measurements R. Bradford et al., Phys. Rev. C 73, 035202 (2006).
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35 Cross Section Measurements R. Bradford et al., Phys. Rev. C 73, 035202 (2006).
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36 Beam-Recoil Double Polarisation C z R. Bradford et al., Phys. Rev. C 75, 035205 (2007). Saclay, Argonne, Pittsburgh Bonn, Giessen, Gatchina Kaon-MAID Regge+Resonance GENT Shklyar Lenske Mosel
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37 Beam-Recoil Double Polarisation C xGENT Saclay, Argonne, Pittsburgh Bonn, Giessen, Gatchina Kaon-MAID Regge+Resonance Shklyar Lenske Mosel R. Bradford et al., Phys. Rev. C 75, 035205 (2007).
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38 Photon Beam Asymmetry
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39 Photon Beam Asymmetry PRELIMINARY
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40 Photon Beam Asymmetry PRELIMINARY
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41 Recoil - Comparison g8b Prev CLAS GRAAL ~Factor of 4 increase in statistics from best previous measurements PRELIMINARY
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