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Downstream PID performance

MICE analysis phone conference2007-01-08

Rikard Sandström

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Outline

• Test of fitting methods– ANN, Fisher and LikelihoodD

• Intrinsic purity– Unmatched beam, flip mode

• Reminder of old performance• New performance• Details

– New and modified variables– Redefinition of good events

• PID and emittance• Conclusions

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Test of fitting methods (140 MeV/c)

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Choosing variables

• For now all variables which have proven useful in the past are used.

• Due to the good performance a set of exclusively calorimeter dependent variables have also been tested.

• Which variables are ideal depends on beam momentum.– Hardest case is low momentum, so most of the effort

has gone into finding useful variables at 140 MeV/c.

• Variables are ranked depending on

– Separation ½∫(s(x)-b(x))2 / (s(x)+b(x)) dx

– Background rejected at 99.9% signal efficiency.– Correlation with other variables

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Stage 6 - purity• In stage 6, objective is to

measure emittance to high precision.– Requires high purity from

background.• Requirement:

– Signal efficiency = 99.90%.– Purity = 99.80%.

• Safety margin: – 3 times expected

background.• At non flip magnetic field

mode, expect much more background since fewer background tracks lost at absorbers.

– Safety margin can be expressed as purity = 99.93%

Initial mom[MeV/c]

Input purity

Req. BG rej.(purity 99.80%)

Safety BG rej.(purity 99.93%)

140 99.56 >54.2 >84.5

170 99.59 >51.6 >83.9

200 99.63 >46.5 >81.3

240 99.63 >46.4 >81.3

Not meeting req. Meeting basic req. Meeting safety req.

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Results – Stage 6, summary BG rejection

Initial mom.

No cal.,with TOF

KL, no TOF

SW, no TOF

KL, with TOF

SW, with TOF

140±14 MeV/c

47.8% 56.2% 79.5% 58.2% 79.5%

170±17MeV/c

54.1% 48.8% 56.4% 59.0% 67.8%

200±20MeV/c

59.0% 57.3% 74.2% 79.4% 87.6%

240±24MeV/c

64.5% 65.0% 91.4% 80.0% 92.2%

TURTLE 83.5%

Not meeting req. Meeting basic req. Meeting safety req.

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Results – Stage 6, summary BG rejection

Initial mom. SW, only EMCal SW, with TOFs & SciFi

140±14 MeV/c 77.6% 89.0%

170±17MeV/c 88.0% 98.4%

200±20MeV/c 97.9% 99.0%

240±24MeV/c 97.2% 99.5%

Not meeting req. Meeting basic req. Meeting safety req.

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Results – Stage 6, safety factor

Initial mom. SW, only EMCal SW, with TOFs & SciFi

140±14 MeV/c 2.0 4.1

170±17MeV/c 7.7 31.1

200±20MeV/c 25.0 56.3

240±24MeV/c 19.2 101.5

Not meeting req. Meeting basic req. Meeting safety req.

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ANN output, 240 MeV/c

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ANN output, 140 MeV/c

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Efficiencies, 140 MeV/c

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Redefinition of good events

• I addition to all previous requirements (inside trackers, momentum and tof reasonable etc) a hit in the calorimeter during the open gate was added to the list.

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PID and emittance

• Together with Chris we have developed a way to look at bias on emittance due to mistaken pid.– That will be another talk/MICE note by either of us.

• Calorimeter specific variables are now reconstructed in the Reconstruction application, just like trackers and tofs.– Cross detector variables are still handled in a

custom made application called RootEvent.– Tracker and TOF values are still smeared MC truth,

but using real reconstructed values will be easy.

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Conclusions

• All requirements in terms of purity and efficiency are fulfilled.– Calorimeter is close to fulfilling safety requirements

(green) completely on its own, making it The PID detector.

• Performance is excellent for high momentum, and worse but still good for low momentum.

• No single variable is good enough on its own -> Multi variable analysis, best handled with Artificial Neural

Networks.

• Cases not (re-)studied:– Stage 1, muon-pion separation.– Stage 6, non flip mode

• Higher background transmission?• Worst case scenario is likely 140 MeV/c non flip mode.