Sci Fi Simulation Status

Osaka, 2 nd Malcolm Ellis MICE Meeting August 2004

Outline

   Status at last collaboration meeting Progress since April: – dE/dx in track fit – addition of fibres as measurements – pattern recognition – current performance   momentum resolution efficiency/purity To-do/priority setting 2

Status at CERN Meeting

   Prototype data had been analysed, light yield, efficiency, dead channels and resolution matched expectations.

Specifications for next station used in G4MICE, light yield, dead channels, etc matched in G4MICE to prototype.

Lack of time had meant some improvements predicted at Abingdon meeting had yet to be implemented...

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Beam/Backgrounds

  All plots presented in this talk were produced with the following conditions: – Beam: Default G4MICE beam – RF Background: 0, 0.1, 1 and 10 times expected rate (100 impossible due to file size) – Detector description: current design, as reported at CERN – Only modification in datacards was to vary the RF background rate (see next slide) Hope to start using beam from G4Beamline once I have time to work with Kenny on this (not before September).

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Sample datacards

                numEvts 50000 SciFiadcFactor 6.0

SciFiFiberConvFactor 3284.0

SciFivlpcEnergyRes 2.0

SciFiMUXNum 7 TPGMode Off SciFiDeadChanFName nom.dcl

rfBGSource gamma rfBGPhotonModel Uniform rfBGNumberOfPhotons 10 rfBGDirection 1 rfBGPhotonEnergy 10 rfBGTimeWindow 100 rfBGTimeDelay -15 rfBGZstart -5650 rfBGRadius 150 Due to file size limitation (max 2G) did not achieve 50k events for large background rates.

0.25% Dead channels as before Same RF background model as before Modify RF Background rate 5

Progress since April

    Improved model of dE/dx in the energy range of interest has been added to the Reconstruction for use by the Kalman package Prototype code to add clusters as measurements in the track fit. Can not be used fully until after the design iteration Pattern recognition improved to enhance purity of muon track selection Code still does not “talk” to PID detectors, this will not happen until design-iteration is carried forward...

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dE/dx in Kalman

   Kalman package can accept a table of mean dE/dx as a function of total momentum.

Currently, does not differentiate between particle types.

dE/dx versus P determined from GEANT4 and fed into Kalman for use in Reconstruction 7

Clusters in Track Fit

   A space point (triplet) consists of three clusters, each describing a line in a Sci-Fi plane.

These clusters can be added to the track and used in the fit as individual measurements, rather than as the 3D space point of the intersection.

This allows efficiency to be recovered by adding 2 or even only 1 cluster per station to the track fit (next version).

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Pattern Recognition

 Proceeds as before, only changes are extra cuts to remove background and reduce CPU use.

– Find clusters – Build space points (only triplets) – Find straight tracks and lock off points – Find best helix – Fit helix 9

Space Points (Triplets)

  A triplet should be three clusters (one in each view) which intersect in space and time Pattern recognition checks the geometrical alignment of the three fibres, as well as the difference in time between them as recorded in the TDCs 10

Triplet Finding

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Straight Tracks

    P T distribution shows a lot of RF induced background are essentially straight tracks Use this to select potential straight tracks and lock the points off so that they will not be considered when searching for a helix This produces a massive saving in CPU use for high RF background Potential for use of a better track model that does not need to differentiate between “straight” and “curved” tracks – see Ken’s talk.

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Straight Tracks

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Muon Track Recognition

   Pretty much as before: – Pick three points – Determine the circle parameters – Check TDC information is consistent – Look for a 4 th or 5 th matching point – Fit track using Kalman filter – Pick track with best c 2 .

Use of the old MINUIT based code is gradually being phased out.

By the time we move to the design iteration version, it will not be used at all...

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Current Performance

    All plots following are with the expected amount of RF background, 0.25% dead channels, conservative light yield, etc, etc...

Result purely Sci Fi, no matching to particle ID detectors for PR or Particle ID (require design-iteration code for that) Position resolution effectively unchanged (slight variation due to new fibre spacing): ~400 m m RMS values quoted versus RF level at end...

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P

X

Resolution – 6.0%

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P

Y

Resolution – 6.7%

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P

Z

Resolution – 1.9%

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P

T

Resolution – 4.7%

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X’ Resolution – 7.4%

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Y’ Resolution – 7.8%

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T’ Resolution – 0.5%

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Track-Finding Efficiency

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Track Purity – 99.8%

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Variation with RF

RMS Values Statistics P X (MeV/c) P Y (MeV/c) P Z (MeV/c) P T (MeV/c) X’ (mrad) Y’ (mrad) T’ Purity In Purity Out No RF 50000 1.68

1.90

3.56

1.68

10.53

11.12

5.23E-3 99.82

99.83

0.1 RF 50000 1.68

1.88

3.63

1.68

10.63

11.16

5.31E-3 99.81

99.83

1.0 RF 26247 1.75

1.91

3.71

1.75

10.85

11.36

5.84E-3 99.83

99.82

10.0 RF 3183 1.86

2.09

3.84

1.65

7.79

11.38

4.94E-3 99.33

99.36

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Magnetic Field versus P?

  Test the hypothesis that as the tracker is m/s limited, there is no advantage to be had by lowering the solenoid field if the mean momentum is lowered.

Simulated 160 MeV/c muons at 4T and at 3.2T, compare momentum resolution...

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160 MeV/c – 4T

10.6 % 13.7 % 27

160 MeV/c – 3.2T

6.5 % 8.0 % 28

To-do / Priority Setting

      Using a realistic description of tracker, background, etc, performance is better than 10% required.

Purity is very high.

Efficiency of PR requires more work.

Further major improvements will not be made without moving to the new design and taking it forward.

Question – is the performance of this code (in CVS already) sufficient for other work (e.g. emittance calculation) to carry on?

If so – as much effort as possible should be directed towards the new design.

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