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Coherent p 0 Photoproduction. Claire Tarbert, University of Edinburgh. Coherent p 0 Photoproduction. 208 Pb. CoherentA( g,p 0 )A IncoherentA( g,p 0 )A*. Theoretical Calculations (Kamalov): PWIA (Plane Wave Impulse Approx ) DWIA (Distorted Wave Impulse Approx) - PowerPoint PPT Presentation
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Collaboration Meeting, 28 March 2006, Glasgow Claire Tarbert
Coherent 0 Photoproduction
Claire Tarbert, University of Edinburgh
Collaboration Meeting, 28 March 2006, Glasgow Claire Tarbert
Coherent0 Photoproduction
Coherent A(0)A
IncoherentA(0)A*
208Pb
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
Coherent0 Photoproduction
Pion Missing EnergyDecay Gammas (16O)
Energy (MeV)
Pion Missing Energy:
E = E(1,2) – E(E)
E(1,2) = pion energy calculated from energy and angle of decay photonsE(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 12C: 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 0s 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 0 photons
M2 = 2E1E2(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 p0 Calibration(January 2005)
Using low E 0s from 12C(March/April 2005)
Collaboration Meeting, 28 March 2006, Glasgow Claire Tarbert
Linearity of Energy CalibrationSeparate into bins according to E1 and E2 (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:
aE3 + bE2 + CE + d
(Fit to average of data… will improve fit!!)
i.e. M = aE3 + bE2 + CE + d
To correct photon cluster energy:
Etrue = Edet ( mo / M )2
Collaboration Meeting, 28 March 2006, Glasgow Claire Tarbert
Linearity of Crystal Ball Energy Calibration
Reran WITHCorrection Factor
Without correction fornon 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
12C
•Contains information on overlap of wavefunction between ground and excited state i.e. Matter Transition Form Factor.
•Interesting minimum at high energies?
Cro
ss
se
cti
on
(A
rb.
Un
its
)
Cro
ss
se
cti
on
(A
rb.
Un
its
)
+ Coherent+ Incoherent
Collaboration Meeting, 28 March 2006, Glasgow Claire Tarbert
Conclusion
• Solid target CB energy calibration almost finalisedCoherent 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
12C(,ppp)9Li
Q value
Low energyclusters from shaded region
2.69 MeV
E=400-500 MeV
i=1
3
• Also look at pp, 4p, 5p … knockout
Missing Energy (MeV) = E–Tpi –Trec
Energy of cluster (MeV)