1. Downstream e-  identification 1. Questions raised by the Committee 2. Particle tracking in stray magnetic field 3. Cerenkov and calorimeter sizes 4. Preliminary conclusions Gh. Grégoire CERN - 27-29 March 2003 Progress towards answers to the International Peer Review Panel 5. Questions MICE Collaboration Meeting

2. Questions raised 1. Homogeneity of response of the particle ID devices downstream ? 2. Risk of bias through loss of muons by unwanted rejection? - position - incident angle - energy dependence of over-vetoing electrons Cerenkov and calorimeter !

3. First elements For the Cerenkov Possible origins of inhomogeneity of response - too few generated photons at some places - non uniform light acceptance/collection across the system Precautions - radiator area is large enough - highly reflective walls and surfaces - number of reflections kept to a minimum Remark These precautions were already taken into account in the conceptual design presented in the proposal … but a second iteration is needed ! What are the sizes and relative positions of the Cerenkov and the calorimeter ?

4. Input data a) Sampleelectrons muons (from P. Janot)4256 10000from the simulation of a cooling channel Starting points Relative populations of electrons vs muons are not normalized ! Previous presentations http://www.fynu.ucl.ac.be/themes/he/mice b) Latest(?) magnetic field configuration from R. Palmer (version 5) c) proposal

5. V.5 Magnetic field configuration r z O

6. Downstream ID detectors … according to proposal ! Transverse size of Cerenkov must match the distribution of muons which reach the calorimeter

7. Particle tracking - Generation of field map downstream the solenoid - GEANT 4 tracking of Janot’s muon and electron files - Results Electron and muon distributions (positions, momentum components) for 0 < z < 1000 mm 0 < r < 500 mm (-500 < x, y < 500 mm) from geometry and current densities (TOF2 not yet taken into account)

8. Trajectories r z r z 1000 mm ElectronsMuons

9. Transverse distributions

10. Acceptance for muons 700 mm 400 mm Calorimeter Cerenkov at z = 100 mm at z  800 mm

11. Preliminary conclusions (1) - Smaller Cerenkov and calorimeter compared to proposal - Updated mechanical and optical designs to come (soon?) - No large improvement expected on homogeneity of response  = 77%Thresh = 5 .e. Fluctuations are largely dominated by statistics Cost … but magnetic shielding not taken into account ! Optical response

12. Preliminary conclusions (2) Correlation with the calorimeter ? With n=1.02, [ % HE muons generating > 5 .e. ] = 0.2 E thr = 530 MeV Unambiguously identified in calo ! … except if  decays inside Cerenkov Proba ~1.5 x 10 -4 (over 0.5 m at 530 MeV) Fraction [ good  ] veto  3 x 10 -7

13. Questions for further work 1. Confirmation of Geant 4 tracking Who? When? 2. Magnetic shielding Rough estimate ~15 cm iron ! Influence on field and on tracking near end of solenoid ?