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Coherent and Incoherent p 0 Photoproduction on Nuclei

Coherent and Incoherent p 0 Photoproduction on Nuclei. Claire Tarbert, University of Edinburgh Experiment spokesperson: Dan Watts. Outline. MAMI-B data: March/April 2005 E e = 883MeV Pb-208, Ca-40, O-16, C-12. Status of Incoherent analysis/publication. C-12 status Other targets

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Coherent and Incoherent p 0 Photoproduction on Nuclei

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  1. Coherent and Incoherent p0 Photoproduction on Nuclei Claire Tarbert, University of Edinburgh Experiment spokesperson: Dan Watts CB Collaboration Meeting, Dubrovnik, 7 April 2008 Claire Tarbert, Univeristy of Edinburgh

  2. Outline MAMI-B data: March/April 2005 Ee = 883MeV Pb-208, Ca-40, O-16, C-12 • Status of Incoherent analysis/publication. • C-12 status • Other targets • Status of Coherent analysis/publication. • Pb-208: status – cross sections • Pb-208: extracting the matter radius CB Collaboration Meeting, Dubrovnik, 7 April 2008 Claire Tarbert, Univeristy of Edinburgh

  3. IncoherentNuclear p0 Photoproduction on - 12C Incoherent A(g,p0)A* Tagg the final state by coincident detection of nuclear decay gammas. Expect strong anisotropy in decay gamma angular distribution. + data -- Geant3 CB Collaboration Meeting, Dubrovnik, 7 April 2008 Claire Tarbert, Univeristy of Edinburgh

  4. IncoherentNuclear p0 Photoproduction on - 12C • Calculations by Takaki: DWIA + D-hole model • Calculations by Tryasuchev: IA + L-S coupling. • Published in PRL – last week! CB Collaboration Meeting, Dubrovnik, 7 April 2008 Claire Tarbert, Univeristy of Edinburgh

  5. IncoherentNuclear p0 Photoproduction – C-12 CB Collaboration Meeting, Dubrovnik, 7 April 2008 Claire Tarbert, Univeristy of Edinburgh

  6. IncoherentNuclear p0 Photoproduction – C-12 CB Collaboration Meeting, Dubrovnik, 7 April 2008 Claire Tarbert, Univeristy of Edinburgh

  7. IncoherentNuclear p0 Photoproduction – Eg dependence of C-12 Work in progress….. CB Collaboration Meeting, Dubrovnik, 7 April 2008 Claire Tarbert, Univeristy of Edinburgh

  8. IncoherentNuclear p0 Photoproduction – Ca-40 and O-16 Ca-40 O-16 a [o] Calculation (Jp = 3- final state) : • Calculation has been corrected for geometric acceptance of detectors. • Need to investigate angular distribution of decay gs more before normalising incoherent cross sections on Ca-40 and O-16. • No calculations exist for Ca-40 or O-16. CB Collaboration Meeting, Dubrovnik, 7 April 2008 Claire Tarbert, Univeristy of Edinburgh

  9. CoherentNuclear p0 Photoproduction Coherent A(g,p0)A Missing energy analysis to isolate coherent events. • Presented finalised total and differential coherent cross sections as a function of pion angle on 208Pb, 40Ca, 16O, 12C in my thesis. • See satisfactory agreement with previous data and theory calculations. • At present working on extracting the matter form factor from final normalised cross sections. CB Collaboration Meeting, Dubrovnik, 7 April 2008 Claire Tarbert, Univeristy of Edinburgh

  10. CoherentNuclear p0 Photoproduction – Eg dependence Ca-40 Pb-208 + CB data + Glasgow TAPS data Kamalov Calcs: PWIA DWIA Full Calc (DREN) C-12 O-16 CB Collaboration Meeting, Dubrovnik, 7 April 2008 Claire Tarbert, Univeristy of Edinburgh

  11. CoherentNuclear p0 Photoproduction – Pb-208 + CB data + Glasgow TAPS data -- DREN (Kamalov) CB Collaboration Meeting, Dubrovnik, 7 April 2008 Claire Tarbert, Univeristy of Edinburgh

  12. CoherentNuclear p0 Photoproduction – Pb-208 Have re- derived cross sections as a function of momentum transfer to the nucleus ….. CB Collaboration Meeting, Dubrovnik, 7 April 2008 Claire Tarbert, Univeristy of Edinburgh

  13. Extracting the Matter Distribution – Pb-208 Without FSI cross section could be descibed by PWIA. FSI has effect of: 1. Changing momentum of outgoing pion as it leaves the nucleus (shift in q). 2. Loss of strength with another channel. CB Collaboration Meeting, Dubrovnik, 7 April 2008 Claire Tarbert, Univeristy of Edinburgh

  14. Extracting the Matter Distribution – Pb-208 • At least 2 possibilities: • Put different matter distributions into the Kamalov model parametrised as a series of Bessel functions. Then do a c2 minimisation against the data. • Correct the data for the effects of FSI first => gives a PWIA cross section. Form factor can then be lifted out and r.m.s. matter radius extracted in a number of ways. CB Collaboration Meeting, Dubrovnik, 7 April 2008 Claire Tarbert, Univeristy of Edinburgh

  15. A simple model to correct for FSI Vo = [M2+p’2]1/2 – [M2+p2]1/2 + [mp2 + p’2]1/2 – [mp2 + p2]1/2 • Use complex potential from Kamalov model to approximate Vo in simple model. • Use shift in the form factor minimum position between the PWIA and DREN calculations to approximate potential height. mp M CB Collaboration Meeting, Dubrovnik, 7 April 2008 Claire Tarbert, Univeristy of Edinburgh

  16. A simple model to correct for FSI + V calculated using shift in 1st minimum position + V calculated using shift in 2nd minimum position + V calculated using shift in 3rd minimum position CB Collaboration Meeting, Dubrovnik, 7 April 2008 Claire Tarbert, Univeristy of Edinburgh

  17. A simple model to correct for FSI Insert beautiful plot here showing that DREN calculations can be corrected back to PWIA. CB Collaboration Meeting, Dubrovnik, 7 April 2008 Claire Tarbert, Univeristy of Edinburgh

  18. Extracting the Matter Distribution – Pb-208 Fitted with a Bessel function Eg = (200-220)MeV Cross section corrected for FSI using simple model. CB Collaboration Meeting, Dubrovnik, 7 April 2008 Claire Tarbert, Univeristy of Edinburgh

  19. Extracting the Matter Distribution – Pb-208 Position of first minimum * No correction for FSI * Corrected for FSI No skin 0.1fm skin => Non zero neutron skin CB Collaboration Meeting, Dubrovnik, 7 April 2008 Claire Tarbert, Univeristy of Edinburgh

  20. Summary • Incoherent reaction • Differential cross sections for C-12: PUBLISHED. • Eg dependence of C-12 cross sections: ANALYSIS BEING FINALISED. • In principle can do the same for O-16 and Ca-40: NEED CALCULATIONS. • Coherent reaction • Have finalised all cross sections as a function of theta. • Have finalised Pb-208 cross sections as a function of q. • Trying to extract matter radius. • Have first draft of paper within 2 months. • ……………………………….. IN PROGRESS. CB Collaboration Meeting, Dubrovnik, 7 April 2008 Claire Tarbert, Univeristy of Edinburgh

  21. End CB Collaboration Meeting, Dubrovnik, 7 April 2008 Claire Tarbert, Univeristy of Edinburgh

  22. End CB Collaboration Meeting, Dubrovnik, 7 April 2008 Claire Tarbert, Univeristy of Edinburgh

  23. End CB Collaboration Meeting, Dubrovnik, 7 April 2008 Claire Tarbert, Univeristy of Edinburgh

  24. Extracting the Matter Distribution – Still to do • Improve resolution if diffraction minima. • Fine tune FSI correction. • Once have PWIA cross section convert to a F(q) • Extract r.m.s. radius CB Collaboration Meeting, Dubrovnik, 7 April 2008 Claire Tarbert, Univeristy of Edinburgh

  25. Working on extracting matter form factor for Pb-208 Postdoc finishes in May 2008 – needs to be done by then! A preliminary look……. Comparison with Kamalov Calcs Comparison with Krusche TAPS data CB Collaboration Meeting, Dubrovnik, 7 April 2008 Claire Tarbert, Univeristy of Edinburgh

  26. Extracting the Matter Distribution – Pb-208 Have derived cross sections as a function of momentum transfer to the nucleus ….. CB Collaboration Meeting, Dubrovnik, 7 April 2008 Claire Tarbert, Univeristy of Edinburgh

  27. Extracting the Matter Distribution – Pb-208 Have derived cross sections as a function of momentum transfer to the nucleus ….. CB Collaboration Meeting, Dubrovnik, 7 April 2008 Claire Tarbert, Univeristy of Edinburgh

  28. CoherentNuclear p0 Photoproduction – Pb-208 Pb + CB data + Glasgow TAPS data -- DREN CB Collaboration Meeting, Dubrovnik, 7 April 2008 Claire Tarbert, Univeristy of Edinburgh

  29. Extracting the Matter Distribution – Pb-208 Have derived cross sections as a function of momentum transfer to the nucleus ….. CB Collaboration Meeting, Dubrovnik, 7 April 2008 Claire Tarbert, Univeristy of Edinburgh

  30. IncoherentNuclear p0 Photoproduction – C-12 CB Collaboration Meeting, Dubrovnik, 7 April 2008 Claire Tarbert, Univeristy of Edinburgh

  31. IncoherentNuclear p0 Photoproduction – C-12 CB Collaboration Meeting, Dubrovnik, 7 April 2008 Claire Tarbert, Univeristy of Edinburgh

  32. Extracting the Matter Distribution – Pb-208 CB Collaboration Meeting, Dubrovnik, 7 April 2008 Claire Tarbert, Univeristy of Edinburgh

  33. Extracting the Matter Distribution – Pb-208 0.1fm increase in rms => 0.01fm-1 shift in 1st minimum position CB Collaboration Meeting, Dubrovnik, 7 April 2008 Claire Tarbert, Univeristy of Edinburgh

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