Upgrade of BBfit v3r6  v4r0 C. Reed development of method S. Galata implementation into SeaTray J. B. Implementation into online (standalone) version

C P P M2 Progress with BBFit Corey Reed Antares Physics Analysis Workshop Rome, November, 2008 BB3D 2-Line Degeneracy BBC Full Fit Resolution Plans

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 Plans

C P P M4 2-line Degeneracy Predict time, angle of Cherenkov photons Loose time residual cut 30 ns, to check only direct hits Look all hits (not just those used in fit) VariableSelection Efficiency Sum of hit charge * angl. wt.61.3% Sum of angl. accpt. wt.67.7% Number of hits in cut69.9% Total charge of hits in cut70.2% BB3D 2-Line Degeneracy BBC Full Fit Resolution Plans

New hit selection + Final fit step Take result from original BBfit or mirror solution if better New hit selection within 20nsec New fit with M-estimator : time residuals only Whole procedure was originally implemented in Ark Was 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 lines Lines with T3 BBfit v4r0 lines Lines 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 665 MC 609 MC  40

Improvement of angular resolution Example: atmospheric neutrinos (12L 3pe) online BBfit, nominal geometry Nline == 2 Nline > 2 v3r6 1.03º v4r0 0.66º v3r6 4.32º v4r0 1.79º MC 1.85º

Improvement of angular resolution Example: atmospheric neutrinos (12L 3pe) online BBfit, nominal geometry Nline == 2 Nline > 2 v3r6 4.32º v4r0 1.79º MC 1.85º v3r6 0.95º v4r0 0.64º

Angular resolution (median) Important improvement with final fit step Full geometry only contributes 0.1º v3r6 v4r0 full geom

Number of Lines used in fit 12 lines 3pe period nlinenlinm Classic BBfitAfter new hit selection

Number of storeys (hits) used in fit 12 lines 3pe period =11.5 =18.9 Classic BBfitAfter new hit selection

Total charge of used hits 12 lines 3pe period =69 p.e. =79 p.e. Classic BBfitAfter new hit selection

Effective area ( ) Comparison of strategies Q<1.4 Nline>1&&Nhit>5 AAfit (C.B.) BBfit Loose cutPoint Source analysis90% 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 agree Sanity check Dashed: BBfit Solid: AAfit

Effective area ( ) Modified quality cut in BBfit Recover HE part which was lost due to distance penalty in fit quality Nline > 1 Q < 1.3+(0.04*NDF)^2 Q < 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: BBfit Solid: AAfit

Effective area Watch out for differences between & Full Neutrino Dashed Antineutrino

Elevation angles 2008 Purity unchanged by modified cut Data 665 MC 609 MC  40 Data 624 MC 588 MC  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)^2 Q < 1.4 v3r6 v4r0 full geom

0.69º 0.43º