upgrade of bbfit v3r6 v4r0 c. reed development of method s. galata implementation into seatray...
DESCRIPTION
C P P M3 2-line Degeneracy 2-lines used in fit Two tracks have same chi2 in BBFit Same zenith Different azimuth BB3D 2-Line Degeneracy BBC Full Fit Resolution PlansTRANSCRIPT
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Upgrade of BBfitv3r6 v4r0
C. Reeddevelopment of method
S. Galata implementation into SeaTray
J. B. Implementation into online (standalone) version
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24 . 11 . 2008 C P P M 2
Progress with BBFit
Corey Reed
Antares Physics Analysis WorkshopRome, November, 2008
BB3D 2-Line Degeneracy BBC Full Fit Resolution Plans
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24 . 11 . 2008 C P P M 3
2-line Degeneracy2-lines used in fit
Two tracks have same chi2 in BBFit
Same zenith
Different azimuth
BB3D 2-Line Degeneracy BBC Full Fit Resolution Plans
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24 . 11 . 2008 C P P M 4
2-line DegeneracyPredict time, angle of Cherenkov photonsLoose time residual cut30 ns, to check only direct hitsLook all hits (not just those used in fit)
Variable Selection EfficiencySum of hit charge * angl. wt.61.3%Sum of angl. accpt. wt. 67.7%Number of hits in cut 69.9%Total charge of hits in cut 70.2%
BB3D 2-Line Degeneracy BBC Full Fit Resolution Plans
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New hit selection + Final fit step
Take result from original BBfit or mirror solution if betterNew hit selection within 20nsecNew fit with M-estimator : time residuals only
Whole procedure was originally implemented in ArkWas thought to work well only with full geometry
(wrong assumption !)
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Implementation into online BBfit
• For Nline==2– Mirror resolution method applied
• For Nline>1– New hit selection + M-estimator applied
• Ntuple modification (BBbatch)– tcosth,tphi,tcterr,tphierr replaced– New fields added : nlim,nhim,ampm,chim
• Event Display– New hit selection and final fit displayed
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BBfit v3r6 linesLines with T3
BBfit v4r0 linesLines added from new hit selection
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Track Fit quality• Multi-line sample (nline>1 && nhit > 5) Ag-2008• Toffset_line + MC(2nsec) included
Data/MC = 1.3
Data 665MC 609MC 40
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Improvement of angular resolution
• Example: atmospheric neutrinos (12L 3pe)• online BBfit, nominal geometry
Nline == 2 Nline > 2v3r6 4.32ºv4r0 1.79º MC 1.85º
v3r6 0.95ºv4r0 0.64º
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Angular resolution (median)
• Important improvement with final fit step
• Full geometry only contributes 0.1º
v3r6 v4r0 full geom v3r6 v4r0 full geom
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Number of Lines used in fit
• 12 lines 3pe period
nline nlinm
Classic BBfit After new hit selection
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Number of storeys (hits) used in fit
• 12 lines 3pe period
<nhit>=11.5 <nhim>=18.9
Classic BBfit After new hit selection
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Total charge of used hits
• 12 lines 3pe period
<amp>=69 p.e. <ampm>=79 p.e.
Classic BBfit After new hit selection
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Effective area ()• Comparison of strategies
Q<1.4
Nline>1&&Nhit>5
AAfit (C.B.) BBfit
Loose cut Point Source analysis 90% neutrino purity
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Effective area ()• Comparison of strategies
Crossover at ~5TeV
BBfit very bad at high energies
BBfit better at low energies if same purity requires
“Loose cut” curves agreeSanity check
Dashed: BBfitSolid: AAfit
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Effective area ()
• Modified quality cut in BBfit• Recover HE part which was lost due to
distance penalty in fit qualityNline > 1Q < 1.3+(0.04*NDF)^2Q < 1.4
Same efficiency at low E
Important gain at high E
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Effective area ()
Crossover at ~20TeV
BBfit better at low energies if same purity requires
BBfit with similar performance at high E
Dashed: BBfitSolid: AAfit
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Effective area
• Watch out for differences between &
Full NeutrinoDashed Antineutrino
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Elevation angles 2008
• Purity unchanged by modified cut
Data 665MC 609MC 40
Data 624MC 588MC 40
Q < 1.4 Q < 1.3+(0.04*NDF)^2
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Angular resolution
• Enery dependent cut improves PSF for M-estimator fit
• Median unchanged
Q < 1.3+(0.04*NDF)^2Q < 1.3+(0.04*NDF)^2Q < 1.4Q < 1.4
v3r6 v4r0 full geom v3r6 v4r0 full geom
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0.69º
0.43º
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