1. New particle ID detector for Crystal Ball at MAMI-C
Daniel Watts, Daria Sokhan, Claire Tarbert
University of Edinburgh
John Annand, Douglas Macgregor, Evie Downie, J McGeorge
University of Glasgow

2. PID-I Constraints of MWPC-I and targets → siting of PMTs
at downstream end
Design specifications
Good separation of
p, p with little overhead
in material before MWPC
and CB detectors
The first Particle ID detector was used in almost all of the experiments in the first round. The detetctor me t the design spec and the particle id capabilities were as we expeected fom the GEANT simulations of the detector.
We opted for the solution of putting thinner scintillator material before the MWPC (2mm). This meant the anglar resolution of the particles in the MWPC was not compromised and to keep to a minimum the energy threshold to get to the wre chamber.
As the MWPC was read out in the downsttream direction and the forward angles was already shadowed by MWPC electronics + because of constraints in space from the available traget systems we sited the PMTs at the downstream end.
These constraints will change with the new MPWC

3. MWPC-II & PID-II MWPC-II redesigned for MAMI-C experiments
PID-II outside MWPC 
inbetween the MWPC chambers 
→ Opted for setup similar to PID-I
But PMTs at upstream end - TAPS
Old pid ring radius 55.6 – new = 66 circumference = 1.18 times larger (need ~28 elements)

4. PID-II schematic PID-II schematic rPID-II >rPID-I
Keep same segmentation (24)
tscint = 4mm (PID-I: 2mm)
PID-II – removable!
(redesigned MWPC connectors)
FPID(INNER) = 108.4mm
FMWPC = 133mm
PMTs
500mm
g beam
PMT support
ring
MWPC
supports
MWPC
Chambers
CB Tunnel
PID-II
scintillators
Hamamatsu H

5. PID-II test module – light attenuation
90Sr beta source
Observe position of landau as source moved along scintillator
→ light attenuation
Active detector
region
Enhancement
near PMT
PID-II Test module
PID-I Test module
Position of landau peak (arb units)
What is light coll efficiency – 4%?
Distance from PMT (mm)

6. PID-II GEANT Simulation
Use PID-I simulation parameters – light output, light collection efficiency, QE …
→ Reasonable agreement with experimental data
Include increase in PID-II scintillator thickness
Pions K+
Protons
Energy deposited in CB (GeV)
Energy deposited in PID-II (GeV)
Flat KE distribution
up to 0.7 GeV
Isotropic angular distribution
No shower shape
restrictions

7. PID-II – schedule and status
months 1 2 3 4 5 6
Delivery of scint.
Total construction
time ~ 5.2 months
Cutting & prep of scint.
Lightguide manufacture
Element assembly & tests
Delivery of PMTs
Cutting previoulsy done at juelich. Have Edinburgh mechanical workshop with scintillator cuttinnig facilities and lightguide making facilities.
Detector assembly & tests
Implementation into
MWPC & CB
Present status

8. Summary Manufacture/delivery of PID-II components complete
Module testing completed in ~2 weeks
Completed detector ready in early June

10. Radius mwpc = 66.5cm
Liquid hydrogen
target

11. PID-II PID-I support ring router-rinner = 14mm
4 mm clearance each side
to the polarised target.
Hydrogen target will have
problem – clearance = 0mm!
51,5
65.5

12. PID-II & polarised target

13. PID-II PMTs
Same tubes and bases as for PID-I
BUT use new packaged tube + base assemblies -include magnetic shield
Hamamatsu H

14. Very preliminary decay gammas from nucleon knockout
12C(g,ppp)9Li
Eg= MeV
2.69 MeV
Low energy
clusters from
shaded region
Q value

15. Simulated p+ signals in Crystal Ball
≤ 2 crystals in p+ shower
No restriction on shower size
m+ decay
Highest cluster energy (GeV)
Here i show the results of a simulation where i varied the incident pion energies. I plot the energy of the highest energy cluster as a function of the energy of the incident pion. The plot on the right has no shower shape restriction. [mu][ni]
The restriction on shower shape cleans up the spectra at all energies and we expect reasonable pion energy reconstruxction up to about 200 MeV.
Nuclear interaction
Incident p+ energy (GeV)

16. Very preliminary decay gammas from nucleon knockout
12C(g,ppp)
2.69 MeV
Low energy
clusters from
shaded region
Q value

18. PID-II – schedule and status
rPID-II >rPID-I
Same segmentation (24)
Lscint chosen to give PID
Info for all proposed targets
Lscint =50 cm (PID-I 32cm)
PID-II Test module
PID-I Test module

19. New polarised target design