Collaboration Meeting, 28 March 2006, Glasgow Claire Tarbert Coherent  0 Photoproduction Claire Tarbert, University of Edinburgh

Collaboration Meeting, 28 March 2006, Glasgow Claire Tarbert Coherent  0 Photoproduction CoherentA(  0 )A IncoherentA(  0 )A* 208 Pb 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 Coherent  0 Photoproduction Pion Missing Energy Decay Gammas ( 16 O) Energy (MeV)  Pion Missing Energy:  E  = E  (  1,  2 ) – E  (E  ) E  (  1,  2 ) = pion energy calculated from energy and angle of decay photons E  (E  ) = pion energy calculated from incident photon assuming a coherent reaction

Collaboration Meeting, 28 March 2006, Glasgow Claire Tarbert Crystal Ball Energy Calibration Traditionally calibration of CB uses 2 body  0 decay kinematics:  p    p Instead try using kinematics of  0 decay from 12 C:  0  i.e. for each crystal plot M  when it is the central element of one of two clusters making a  0 Constraints:  Limit E  < 180 MeV i.e. just above threshold  ratio of light collection/shower loss remains ~constant  low energy  0 s i.e. photon opening angle is large  80% of cluster energy in central crystal  Correction for cluster ~ correction for central crystal  I E 1 – E 2 I < 0.25( E 1 + E 2 )  Same correction applies to both  0 photons M  2 = 2E 1 E 2 (1 - cos  )

Collaboration Meeting, 28 March 2006, Glasgow Claire Tarbert Crystal Ball Energy Calibration Result: Correction factor for MeV/Chn values for each crystal. Correction Factor = m  / M 

Collaboration Meeting, 28 March 2006, Glasgow Claire Tarbert Crystal Ball Energy Calibration  p  p  0 Calibration (January 2005) Using low E  0 s from 12 C (March/April 2005)

Collaboration Meeting, 28 March 2006, Glasgow Claire Tarbert Linearity of Energy Calibration Separate  into bins according to E 1 and E 2 (  0 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 Linearity of Crystal Ball Energy Calibration Tabulated values plotted

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

Collaboration Meeting, 28 March 2006, Glasgow Claire Tarbert Linearity of Crystal Ball Energy Calibration Fit to plots: aE 3 + bE 2 + CE + d (Fit to average of data… will improve fit!!) i.e. M  = aE3 + bE2 + CE + d To correct photon cluster energy: E true = E det ( m  o / M  ) 2

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

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

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

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

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

Collaboration Meeting, 28 March 2006, Glasgow Claire Tarbert Preliminary look at Incoherent  0 Photoproduction 12 C Contains information on overlap of wavefunction between ground and excited state i.e. Matter Transition Form Factor. Interesting minimum at high energies? Cross section (Arb. Units) + Coherent + Incoherent

Collaboration Meeting, 28 March 2006, Glasgow Claire Tarbert Conclusion Solid target CB energy calibration almost finalised  Coherent   Photoproduction cross sections hopefully available soon. Interesting hints from incoherent channels.

Collaboration Meeting, 28 March 2006, Glasgow Claire Tarbert Preliminary decay gammas from nucleon knockout 12 C( ,ppp) 9 Li Q value Low energy clusters from shaded region 2.69 MeV E  = MeV i=1 3 Also look at pp, 4p, 5p … knockout Missing Energy (MeV) = E  –  T pi –T rec Energy of cluster (MeV)