1 downstream pid performance mice analysis phone conference 2007-01-08 rikard sandström
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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.