Upgrade of BBfitv3r6 v4r0

C. Reeddevelopment of method

S. Galata implementation into SeaTray

J. B. Implementation into online (standalone) version

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

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

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

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 !)

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

BBfit v3r6 linesLines with T3

BBfit v4r0 linesLines added from new hit selection

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

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

Angular resolution (median)

• Important improvement with final fit step

• Full geometry only contributes 0.1º

v3r6 v4r0 full geom v3r6 v4r0 full geom

Number of Lines used in fit

• 12 lines 3pe period

nline nlinm

Classic BBfit After new hit selection

Number of storeys (hits) used in fit

• 12 lines 3pe period

<nhit>=11.5 <nhim>=18.9

Classic BBfit After new hit selection

Total charge of used hits

• 12 lines 3pe period

<amp>=69 p.e. <ampm>=79 p.e.

Classic BBfit After new hit selection

Effective area ()• Comparison of strategies

Q<1.4

Nline>1&&Nhit>5

AAfit (C.B.) BBfit

Loose cut Point Source analysis 90% neutrino purity

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

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

Effective area ()

Crossover at ~20TeV

BBfit better at low energies if same purity requires

BBfit with similar performance at high E

Dashed: BBfitSolid: AAfit

Effective area

• Watch out for differences between &

Full NeutrinoDashed Antineutrino

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

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

0.69º

0.43º