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EMCal simulations

e + 100 MeV. EMCal simulations. MICE Video Conference 2005-03-09 Rikard Sandström Geneva University. Outline. Introduction to setup Beams Improved geometry & digitization Simulation of hits Monochromatic beams of e + and µ + Energy loss Ranges Detector response (Digitization)

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EMCal simulations

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  1. e+ 100 MeV EMCal simulations MICE Video Conference 2005-03-09 Rikard Sandström Geneva University

  2. Outline • Introduction to setup • Beams • Improved geometry & digitization • Simulation of hits • Monochromatic beams of e+ and µ+ • Energy loss • Ranges • Detector response (Digitization) • Using digits to separate mu from e. • Wrap-up

  3. Beams • For a start, will compare monochromatic e+ & µ+ beams: • 100, 150, 200 MeV/c. • The “real” beam: • A Tilley TURTLE beam, fed into G4MICE by Malcolm. • Starting at z = -5800 mm (before upstream SciFi) in G4MICE. • Initial energy 231.6 MeV (see plot). • Found a small bug: • CKOV2 windows material • Etot = 208.5 +- 2.8 MeV when leaving downsteam tracker. • With TOF and CKOV Etot ~ 185 MeV at EMCal. • 0.22 X0 between downstream tracker and EmCal -> 20 MeV. • TOF 6 MeV, CKOV windows 13 MeV. • Steve is fixing it.

  4. 40 mm 0.5 mm 1.35 mm 0.3 mm Improved geometryand digitization • Added air gap (holes) between lead and fibers. • (Pictures from G4MICE.) • Added incomplete gamma functions to integrate over the signal. • With cuts on open gate etc.

  5. Initial mu+ hit 2nds Energy deposited by real beam E lost in TOF & CKOV

  6. 1st to 2nd layer 2nd to 3rd layer Total energy, real beam MeV mu+ 2nds z [mm] Note that the fiber structure is visible.

  7. 1st to 2nd layer Hit position, real beam Black = mu+ only Red = total

  8. Hit position, 200 MeV/c e+ beam Fitted with Landau, shower maxima at 22 mm.

  9. Range, muons • Checks suggested by Ludovico Tortora. • Result: Makes sense to me. • Checked muon ranges with PDG for: • Pure lead • Pure polystyrene • Compound material (lead+polystyrene @ 5.645 g/cm2 ~1:1 ratio) • Lead, mu+ 222 MeV/c: • PDG: 8.22 cm • G4MICE: 8 cm • Polystyrene, mu+ 100 MeV/c: • PDG: 7.37 cm • G4MICE: 6.7 cm • Compound material (real), mu+ 222 MeV/c: • PDG1: max 16.5 cm • G4MICE: 14 cm Boundaries 1 Calculating true density, treating it as Pb. (Polystyrene would shorten range.)

  10. Range, EM-cascades • No good theory exist (Passage of particles through matter) • X0(Pb) = 0.56 cm • Xshower(Pb) = 2 X0 = 1.12 cm (average) • In G4MICE, 200 MeV/c e+: dzMPV(Pb) = 1.312±0.002 cm • EGSnrc (basis for PDG’s “Passage of particles…”) • Lead 45.2%, fibers 49.7% of EMCal volume. • 16 cm EMCal = 7.232 cm lead. • Rest is air gap between lead and fibers. • 200 MeV/c, 7.232 cm Pb (treating fibers & air gaps as vacuum) -> • 0.88% energy reflected • 95.27% energy deposited • 3.844% energy transmitted

  11. Well, what about the fibers? • Extreme case, all lead (16 cm): • EGSnrc gives-> • 1.0% energy reflected • 99.0% energy deposited • 0.058% energy transmitted • Even if we overestimate the amount of lead, a 200 MeV/c e+ still showers through sometimes. • G4MICE: 4.2% of the energy of a 200 MeV/c e+ beam is neither deposited in lead nor fiber. • Lead-only in EGSnrc: 4.7%. • Did not could energy lost in the air gaps. • According to EGSnrc 1% should be lost to upstream. • Still ~3% showers through.

  12. Comments, and PID ideas • Passage of particles through matter: • “The number of particles crossing a planeis sensitive to the cutoff energy[...]. The electron number falls off more quickly than energy deposition. This is because, with increasing depth, a larger fraction of the cascade energy is carried by photons.” • I don’t see this since we cut well below Ecrit. • The hit position wrt layer is very characteristic for mu+ compared with e+ • Thus also for digits. • Expected range (or barycenter) should be used for PID. • On all following slides: • Muon beam • Positron beam µ+ e+ 4 1 2 3

  13. Hit deposition, fiber/lead (200 MeV/c) Edep fiber/lead is constant for muons, and different for e and µ. Fibers sees electrons, photons convert in lead, fiber/lead dep decreases with z.

  14. Hit deposition, per total (200 MeV/c)

  15. ADC in each layer (200 MeV/c) Should look similar to the hits on previous page (and does).

  16. Total ADC (200 MeV/c)

  17. Plotting A against B (My “Alessandra plots”, all preliminary.) • Visual representation of e-mu separation. • Using log scaled sizes of “z” values. + More colour -> Old professors can see my results. - Gives impression that the peaks melt into each other more than they actually do. • Higher statistics looks worse in terms of separation. • Modest green line = 2D Gaussian fit. • Indicated fit results are • p0 = norm, p1 =xmean, p2 = xsigma, p3 = ymean, p4 = ysigma, p5 = correlation. • Gaussian/Gaussian != Gaussian, but a Cauchy distribution. • In principle, could make 3D plots with [ADC1]:[Total ADC] :[Barycenter] • Or why not a 4D fit with ADC2 in addition?

  18. Separation, based on layer 1 200 MeV/c

  19. Separation, based on layer 2 200 MeV/c

  20. Barycenter vs total ADC 200 MeV/c

  21. At lower momenta (#1) 200 MeV/c • No difference in total ADC at low p. • Variables used for PID have an ideal p-range. • Algorithm should use many variables for robustness. 150 MeV/c 100 MeV/c

  22. At lower momenta (#2) 100 MeV/c 150 MeV/c • Barycenter separation gets worse, but… • At very low p muons are confined in first layer, whereas a shower is not. • At 150 MeV/c ADC counts in layer 2 looks best. 150 MeV/c

  23. Comments on results • Some improvements and cross-checks needed: • No noise. • No decay. • No cutoff in time. • Made the open gate very long to isolate problems. • Total ADC etc is sum of all channels. • Also left-right of same cell. • I tried using a product of left-right ADC counts instead of a sum, but saw no improvement. • Difference in E-dep between e/mu might motivate decision on lead to fiber ratio. • I verified that this difference does not on simulation Ecutoff. • It looks like PID is good with this design. • Algorithm can use the same method on both 1st and 2nd layer and compare. • Muons are “point like”, i.e. well defined and predictable. • Longitudinal and total energy deposition seem powerful test variables. • ADC1, ADC2, totalADC, barycenter. • Need to investigate 200-260 MeV/c range to see if we need a 5th layer.

  24. Transverse hit positions • NB: No use was made yet of transverse properties. • Will be used together with extrapolated tracks from tracker. • G4 meeting yesterday: • Next Geant4 patch will include improved transverse position for EM-showers. • Crossed cell planes or parallel?

  25. Future plans • Identify, choose, and weight good PID variables. • Will require the measured momentum px, py, pz (from tracker) and calculating expected signals in EMCal. • Write the EMCal reconstruction in G4MICE. • Should give information to global PID (tracker, TOF, etc) in format adequate for statistical combination. • Report on actual e-mu separation efficiency. • Tune time variables (open gate, trigger delay etc). • When new event structure in G4MICE is ready, run with real spill, real beam, with decay.

  26. Barycenter vs total ADC, 200 MeV/c

  27. Barycenter vs ADC1/total ADC, 200 MeV/c

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