TWIST Analysis Plans

Last Updated October 16, 2003

See also the TWIST Systematics Studies.

  1. Helix Fitter Tests

    1. Tuning of drift time/distance fitting code (Konstantin/Andrei). This will be done after blind analysis code is prepared. Present helix fitter vs michel parameter sensitivity:
      1. fit with L/R unknown
      2. fit with L/R from MC
      3. compare b & c
      4. fit with wire centers -done
      5. compare e & c/b
      6. fit with different strs
      7. move/stagger chambers in GEANT -done
      8. with and without fieldmap

  2. Pattern Recognition Tests (Jim/Blair)

    1. Study effect of muon dead zone on classification.
      1. GEANT Test - Artificially deaden hits some number of planes before muon stop. See at what level this effects michel parameters compared to non-deadened run.
      2. Data test - Compare classification of early non-overlapping decays (1000 - 1500 ns) to late decays (5000 - 9000 ns).

    2. Study inaccurate winding number assignments.
      1. Apply early rough cut, such as average wires/plane or cluster size/pair. Examine effect of throwing out outliers. Amost done see firstguess postings.

      2. Use cluster size vs. |cos(theta)| relationship to aid in FirstGuess.
        1. Use to constrain winding number in (omega_z, phi_not) fit in manner similar to dense stack constraints.
        2. Evaluate resulting cluster size vs. |cos(theta)| for accuracy of fit.
        3. Evaluate effect of instrumenting more of the dense stack (Jim).

    3. Study inefficiencies in delta removal code.
      1. Compare reconstruction of GEANT runs with and without delta production. Eventually should be full statistics study to see sensitivity to Michel parameters.
      2. Explore possible correlations with delta removal failures. Success/failure vs. (MC decay params, delta parameters, other)

    4. GEANT-to-GEANT Studies
      1. Evaluate backgrounds from showering in the yoke - not possible using field map.

    5. Study October 23, 2002 beam tune change by fitting set B to set A.
      1. Use set A as standard distributions.
      2. Use GEANT produced derivative distributions.

    6. Test classification for case if target PCs are used in ADC mode, and so have low efficiency for TDC information. (Do test by throwing away all target PC TDC information.) Progress...

      Done. No effect on Michel in low statistics test.

    7. Examine effect of changing parameters in classification. Check sensitivities for both GEANT and data.
      1. Cross Talk, Noise, and Cosmic Removal Parameters
      2. Windowing Parameters
      3. Other Side Delta Removal Parameters
      4. High Angle Track and Scattering Detection Parameters
      5. Muon ID Parameters
      6. Soft Uncorrelated Laserlike Track ID Parameters

    8. Ntuple updates... not pattern recognition(Blair)
      1. Debug ID of pi-> e nu windows to make sure they make it to the ntuple Done? (21 Aug 2003)
      2. Post list of ntuple variables, get feedback, and add/remove variables Done, here's the list (7 Jul 2003)
      3. And some root tree documentation Documented Here.

  3. Asymmetry/Muon Polarization Studies

    1. Check sensitivity of asymmetry estimate to different cuts Done with no clear culprit. Was tune even worse than we thought?
    2. Try other methods of analysis developed
    3. Look at asymmetry of different data sets
      1. Slightly upstream and slightly downstream
      2. Changed B2
      3. Different densities
      4. Different stopping locations (different C02% or extra foils)
    4. Revisit T1GEANT to try to estimate expected muon polarization for stainless steel cladded Be target.
    5. Get some new data with Graphite target
    6. Get data to study polarization as muon momentum is lowered (different depths in production target).

  4. Blind Analysis Code Preparation (Andrei)

    1. Develop Fitting scheme Done. Doc required.
    2. Ripple studies
      1. Check for effect of different binning - Done, biases remain
      2. Artificially worsen resolution
      3. Use alignment files for generation of GEANT - no conclusion whether to make this the default.

  5. TWIST Geant Tests (Rob et al.)

    6. Ways to verify Geant against real data. The main person looking into each item is listed in [square brackes]. Current priorities are listed for RPM's tasks.

    High Level Tests

    These are looking at various impacts on the "end results" of simulations, especially momentum and angle distributions. Michel spectrum fitting will be useful for some of these.

    "Downstream Aluminum Problem" [RPM (1)]
    Understanding why an aluminum plate placed downstream has so much more impact in data than in Geant.

    "Geant vs Geant" [RPM (1.1)]
    Mirrors of various "data vs data" studies.
    • Still looking at 'downstream aluminum' studies. Investigate delta removal.
    • Coordinating with JRM to ID studies that show the largest effects (DS aluminum, DC HV, etc).

    • A list of relavent forum links is available.

    Energy Loss & Multiple Scattering [RPM (3)]
    Can also compare both Geant and data against theoretical calculations. Especially when all material thicknesses are known.
    • I'll use muon ranging during momentum scans to get another estimate of the target's graphite layer thickness, to compare with that suggested by the energy loss results.
    • The aluminum target (with known thickness) will be very valuable for these tests, as well.

    "Slightly" upstream/downstream stops. [RPM (5)]
    Test response (e.g. asymmetry, momentum distribution, etc.) to muons stopping in target, but not centred.

    Energy calibration with pions. [Roman]
    Compare measured response function of 70 MeV/c positrons from decay of stopped pions.

    Low Level Tests

    These are looking at parts of the simulation in detail.

    Distribution of cluster sizes and numbers of hits. [RPM (2)] (Clear evidence of extra hits not modeled in GEANT, UV photons still a plausible mechanism.)
    Mainly a test of clustering, and of the efficiency of detecting when a track clips a cell corner.
    • Cluster size discrepancies can skew some parts of the reconstruction, so it's important to get them right (or at least close).
    • A list of relavent forum links is available.

    Reconstruction Efficiency [RPM (4)]
    Looking at through-going tracks (e.g. decays from upstream-stopping muons); how many reconstruct in one half but not the other? Compare distributions between Geant and data.

    TDC spectra. [KO?]
    Test of clustering, resolution functions, etc.

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