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Improving MuCal Design

Improving MuCal Design. Why we need an improved design Improvement Principle Quick Simulation, Analysis & Results Pros & Cons. Why an improved design. CKOV2 funding is uncertain EmCal mu+/e+ is not straightforward Using many parameters with Complicate (Neural Net) Analysis

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Improving MuCal Design

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  1. Improving MuCal Design • Why we need an improved design • Improvement Principle • Quick Simulation, Analysis & Results • Pros & Cons Jean-Sébastien Graulich

  2. Why an improved design • CKOV2 funding is uncertain • EmCal mu+/e+ is not straightforward • Using many parameters with Complicate (Neural Net) Analysis • Stability vs MICE configuration ? Systematics ? • Separation Requires • P and TOF measurement -> How do we do in Stage I ? (No P measurement !) • Precise Energy Measurement -> ADC Problem • EmCal (Kloe) design is optimized for higher energy muons • 200 MeV/c muons are stopped in the middle • Inhomogeneous material-> spread in muon range -> spread in visible energy Jean-Sébastien Graulich

  3. Improvement Principle • Start with a rather thin high Z material layer • Stop primary positrons and convert them into gammas and soft e+/e- • Several layers of plastic scintillators (low Z) • Large Muon range -> long tracks with large energy deposit/layer • Soft e+/e- -> scattered hits with small energy deposit • Nearly Transparent to gammas (low Z) • Problem with low energy muons (<120 MeV/c) • They stop in the first (high Z) layer • Maybe TOF can help e+ µ+ Jean-Sébastien Graulich

  4. Quick Simulation • First layer (Converter) = 1 Kloe layer (4 cm thick, 8 cm wide) • 11 Layers of scintillator, 2 cm thick, 8 cm wide (15 slabs/layer) • A passive plastic layer has been introduced : bad idea ! • This kills the muon detection efficiency below 150 MeV/c • Mu Efficiency is estimated only above this threshold • Many thanks to Rikard 162 MeV/c Muon Passive 6 cm Kloe4 cm Jean-Sébastien Graulich

  5. Simulated Beam • Using an old Turtle beam (small divergence) • Same as Rikard used 3 month ago • Small number of positrons • 256 e+, only 199 reach MuCal in a 20 ns time window. 35085 µ+ over 150 MeV/c Jean-Sébastien Graulich

  6. High thr: 2.5 MeV Low thr: 200 keV Quick Analysis • No realistic digitization yet • Using True Visible Energy with 10% resolution • No charge measurement: • Only two level discriminator: low/high signal • No clustering, signal sharing ignored. • Muons • Positrons Jean-Sébastien Graulich

  7. Quick Analysis • Looking at Track Length • Counting only high level hits • Taking the maximum length of continuous track • X,Y Segmentation not used, the highest hit in the layer is taken • Looking at low level hits • Just count the layerswhere there is a low level hit and no high level hit • Again X,Y Segmentationnot used • Rem: • X,Y Segmentation is used only fordigitization, not for analysis e+ have short tracks andmany low level hits Muons have long tracks and no low level hits Jean-Sébastien Graulich

  8. Quick results • This can be reduced to one single parameter • Continuous intense track length index = High level track length divided by the number of sparse low level hits Cut at 1 Jean-Sébastien Graulich

  9. Results Summary • Muon efficiency (over 150 MeV/c): 99.7 % • Positron rejection efficiency (all energies): 98.4 % • Purity of the muon sample: 99.98 % • Main Losses: mu decay either in flight or in the time window (20 ns) Jean-Sébastien Graulich

  10. Background study • Main background: • Coincidence with muon decay • Either the one just arriving or a previous one • Main effect: • The continuity of the track is affected; a muon is misidentified as a positron • Small bias (decay in flight probability slightly depends on the momentum) • Higher order effect: • The decay product piles up with a positron, producing a fake track. • Highly suppressed by geometric factor if segmentation is used in the calculation of the track length • Case studied: • A muon piles up with its own decay product • Studied by increasing the time window at the digitization level: 20 ns -> 100 ns • Results: • Mu Efficiency drops to 97 % Jean-Sébastien Graulich

  11. Easy mu/e separation 1 parameter with physics signification No need for CKOV2 Simple, “cheap” technology No need for good energy resolution Similar design can do mu/pi separation in Stage I (ask Rikard) Allow triggering on high P muons (in phase w RF) Need more Pmts Who can build it? Need help to find more cons… Pros and Cons Jean-Sébastien Graulich

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