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Coherent p 0 Photoproduction

Coherent p 0 Photoproduction. Claire Tarbert, University of Edinburgh. Coherent p 0 Photoproduction. 208 Pb. Coherent A( g,p 0 )A Incoherent A( g,p 0 )A*. Theoretical Calculations (Kamalov): PWIA (Plane Wave Impulse Approx ) DWIA (Distorted Wave Impulse Approx)

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Coherent p 0 Photoproduction

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  1. Coherent p0 Photoproduction Claire Tarbert, University of Edinburgh Collaboration Meeting, 28 March 2006, Glasgow Claire Tarbert

  2. Coherent p0 Photoproduction 208Pb Coherent A(g,p0)A Incoherent A(g,p0)A* Theoretical Calculations (Kamalov): PWIA (Plane Wave Impulse Approx ) DWIA (Distorted Wave Impulse Approx) DREN (Delta Resonance Energy Model) Good agreement with theory. Collaboration Meeting, 28 March 2006, Glasgow Claire Tarbert

  3. Coherent p0 Photoproduction • Pion Missing Energy: • DEp = Ep(g1,g2) – Ep(Eg) • Ep(g1,g2) = pion energy calculated from energy and angle of decay photons • Ep(Eg) = pion energy calculated from incident photon assuming a coherent • reaction Pion Missing Energy Decay Gammas (16O) Energy (MeV) Collaboration Meeting, 28 March 2006, Glasgow Claire Tarbert

  4. Crystal Ball Energy Calibration • Traditionally calibration of CB uses 2 body p0 decay kinematics: • p ->p0p Instead try using kinematics of p0 decay from 12C: p0-> g g i.e. for each crystal plot Mgg when it is the central element of one of two clusters making a p0 • Constraints: • Limit Eg < 180 MeV i.e. just above threshold => ratio of light collection/shower loss remains ~constant => low energy p0s i.e. photon opening angle is large • 80% of cluster energy in central crystal => Correction for cluster ~ correction for central crystal • I E1 – E2 I < 0.25( E1 + E2 ) => Same correction applies to both p0 photons Mgg2 = 2E1E2(1 - cosy) Collaboration Meeting, 28 March 2006, Glasgow Claire Tarbert

  5. Crystal Ball Energy Calibration Result: Correction factor for MeV/Chn values for each crystal. Correction Factor = mp / Mgg Collaboration Meeting, 28 March 2006, Glasgow Claire Tarbert

  6. Crystal Ball Energy Calibration Using low E p0s from 12C (March/April 2005) gp -> pp0 Calibration (January 2005) Collaboration Meeting, 28 March 2006, Glasgow Claire Tarbert

  7. Linearity of Energy Calibration Separate Mgg into bins according to E1 and E2 (p0 decay photon energies) e.g. 200 < E1 < 210 MeV && 40 < E2 < 60 MeV, 200 < E1 < 210 MeV && 60 < E2 < 80 MeV, 200 < E1 < 210 MeV && 80 < E2 < 100 MeV etc… Collaboration Meeting, 28 March 2006, Glasgow Claire Tarbert

  8. Linearity of Crystal Ball Energy Calibration Tabulated values plotted Collaboration Meeting, 28 March 2006, Glasgow Claire Tarbert

  9. Linearity of Crystal Ball Energy Calibration Collaboration Meeting, 28 March 2006, Glasgow Claire Tarbert

  10. Linearity of Crystal Ball Energy Calibration Fit to plots: aE3 + bE2 + CE + d (Fit to average of data… will improve fit!!) i.e. Mgg = aE3 + bE2 + CE + d To correct photon cluster energy: Etrue = Edet ( mpo / Mgg )2 Collaboration Meeting, 28 March 2006, Glasgow Claire Tarbert

  11. Linearity of Crystal Ball Energy Calibration Without correction for non linearity Reran WITH Correction Factor (Only 1/3 of data) Collaboration Meeting, 28 March 2006, Glasgow Claire Tarbert

  12. Low Energy Calibration of Crystal Ball • Use 4.43MeV decay gs from 12C. • Select events where decay g fires single crystal. • => new MeV/Chn values for low energies. Collaboration Meeting, 28 March 2006, Glasgow Claire Tarbert

  13. Low Energy Calibration of Crystal Ball Comparison to AmBe calibration Collaboration Meeting, 28 March 2006, Glasgow Claire Tarbert

  14. Low Energy Walk Correction of Crystal Ball Collaboration Meeting, 28 March 2006, Glasgow Claire Tarbert

  15. Low Energy Walk Correction of Crystal Ball With Low Energy Walk Correction Collaboration Meeting, 28 March 2006, Glasgow Claire Tarbert

  16. Preliminary look at Incoherent p0 Photoproduction 12C • Contains information on overlap of wavefunction between ground and excited state i.e. Matter Transition Form Factor. • Interesting minimum at high energies? + Coherent + Incoherent Cross section (Arb. Units) Cross section (Arb. Units) Collaboration Meeting, 28 March 2006, Glasgow Claire Tarbert

  17. Conclusion • Solid target CB energy calibration almost finalised • => Coherent p0 Photoproduction cross sections hopefully available soon. • Interesting hints from incoherent channels. Collaboration Meeting, 28 March 2006, Glasgow Claire Tarbert

  18. Preliminary decay gammas from nucleon knockout 12C(g,ppp)9Li Eg=400-500 MeV 2.69 MeV Low energy clusters from shaded region Q value Missing Energy (MeV) = Eg –STpi –Trec Energy of cluster (MeV) 3 i=1 • Also look at pp, 4p, 5p … knockout Collaboration Meeting, 28 March 2006, Glasgow Claire Tarbert

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