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

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

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)

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 H3164 - 10

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)

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

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

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

Radius mwpc = 66.5cm Liquid hydrogen target

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

PID-II & polarised target

PID-II PMTs Same tubes and bases as for PID-I BUT use new packaged tube + base assemblies -include magnetic shield Hamamatsu H3164 - 10

Very 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

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)

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

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

New polarised target design